Chapter 3 - Co-Ordination

2nd Year Biology Notes

 

XII Biology Notes BISE Karachi Chapter 3 - Co-Ordination



Plant Hormones: (Phytohormone)



Definition



Certain chemical produced by plants have profound effect on their
subsequent growth and development. Such chemicals are called Plant
Hormones or Phytohormone.

Phytohormone are synthesized by plants in minute concentration and
exert their effect by activating gene expression or inhibiting enzyme
or changing properties of membrane.





Types of Phytohormone



There are five kind of plant hormones

1. Auxins

2. Gibberellins

3. Cytokinins

4. Abscisic Acid

5. Ethene



1. Auxins

Discovery

the first auxin was discovered by Fret Went in 1926.

Chemical Nature

Indol Acetic Acid (I.A.A)

Indol Acetic Acid (I.B.A)

Nephthalene Acetic Acid (N.A.A)

Site of Synthesis

It is synthesize at the apices of stem and foot, young leaves and young embryo.



Role of Auxin

i. Cell division and cell enlargement

It stimulate teh cell division and cell enlargement and plant in increase the length of plant.

ii. Initiation of Root

Auxins also initiates development of adventitious roots when applied at the cut base of stem.

iii. Abscission

In mature leaves and fruits when auxin production diminishes, a layer
of thin walled cells is formed at the base of petiole and stake of
fruit. This layer is called Abscission layer and causes fall of leaves
and fruit with slight jerk.

iv. Growth of Fruit

Auxins produced in young embryo promotes the growth of fruit.

v. Parthenocarpy

Use of auxin helps in producing parthenocarpic or seedless fruits.

vi. Apical Dominance

Besides growth promoting function on Auxin, also has inhibitory effect
on growth. Growth of apical bud inhibits growth of lateral buds beneath
the stem. This phenomenon is termed as apical dominance removal of
apical buds initiates growth of lateral buds with more leaves and
axillary bud.

vii. Weedicide

Auxins are selective weed killer 2-4 dichlorophenoxy acetic acid (-2-4-D) is used to kill weeds in lawn's and cereal crops.



2. Gibberellins

Discovery

Gibberellins was discovered by T.Yabuta and I.Hayashu in a fungus
called Gibberellins funjikuroi. This fungus causes foolish seedling
(Bakanae) disease in rice. In this disease the infected rice seedling
elongated and ultimately fallover without producing grains.

Chemical Nature

The chemical nature of Gibberellins is Gibberellins acid 70 types of gibberellins have been discovered.



Role of Gibberellins

i. Cell division and cell enlargement

Like auxins Gibberellin also promotes cell division and elongation.

ii. Control of Dwarfism

Gibberellins can control genetic and physiological dwartism plants.

iii. Seed Germination

They promote the synthesis of a-amylase enzyme is dorman seeds due to
the production of this enzyme, the seed starts germination.

iv. Parthenocarpy

These hormones help in the formation of seedless fruit which are called Parthenocarpic fruits.

v. Increase of Crop Yield

The crop yield of sugar can can be increased by the application of gibberellin about 50 tons/ acre.

vi. Formation of Flower and Growth of Pollen Tube

They stimulate flowering and the growth of pollen tubes during fertilization



3. Cytokinins

Discovery

Cytokinins are discovered by Miller in coconut milk.

Chemical Nature

Chemically there are two types of cytokinins.

Kinetin It is found in coconut milk etc.

Zeatin It is found in maize.



Role of Cytokinins

i. Cell Division

They initiate rapid cell division only in the presence of auxin.

ii. Delay in Senescence

They also caused delayed senescence (old age).

iii. Breaking of Seed Dormancy

They break seed dormancy and promote fruit development some species.



4. Abscisic Acid (A.B.A)

In contrast to growth promoting hormones, abscisic acid is growth
inhibitor, produced by plants during adverse environment conditions
such as drought conditions.



Role of Abscisic Acid

• It increases dormancy in buds and seeds.

• It causes stomata to close.

• It turn leaf primordia into scale.

5. Ethene

It is a gas which also acts as a growth inhibitor.



Role of Ethene

• It triggers ripening of fruits.

• It contributes in leaf abscission and also breaks the dormancy of seeds and buds.

• It also initiates flowering in plants e.g. pineapple.

Responses to Environmental Stress



Changes in environmental conditions are the big threats for living
organisms especially for plants. These factors which change the normal
condition of light, CO2, nutrients, temperature etc. causes severe
stresses on plants. The common environmental stresses for plants are

1. Water Shortage (Drought condition)

2. Less Oxygen Supply

3. High Concentration of Salt in the Soil

4. High Temperature

5. Low / Cold Temperature

6. Herbivory / Over Grazzing



1. Water Shortage

• In dry condition, the guard cells of leaf become flaccid to close the stomata.

• In this way the transpiration is stopped.

• The dry condition also stimulates increased synthesis and release of abscisic acid.

• This hormone help in keeping stomata close.

• These plants produce deeper root system.

2. Oxygen Deficiency

• Those plants which grow in wet habitat or marshes, they develop aerial roots to absorb oxygen.

• Some plants developed air tubes that provide oxygen to submerged roots.

3. Salt Stress

• The plants especially halophytes, have salt glands in their leaves where desalination occurs.

4. Heat Stress

In plants there are two methods to tolerate the heat stress.

• Transpiration has a cooling effect on the plant body. By this method the effects of heat are reduced.

• Above 40oC plants cell start synthesizing relatively large quantities of special protein called heat shock proteins.

5. Cold Stress

• Plants respond to cold stress by altering the lipid
  composition, changes in solute composition is altered also by producing
  different polymers of pentose (Fructose) which allow the crystals to
  super cool without compound formation.

6. Herbivory / Over Grazzing

• Plants overcome excessive herbivory by developing horns and production of distasteful or toxic compounds.

Defence Against Pathogens



Diseases of plants may arise from infections by viruses, bacteria or
fungi and other pathogens in most cases. Against these diseases the
plants produce immune system in their body.



First Line Efence

The outer layer epidermis is a protective covering around the body of plant. This is the First Line Defence.

Second Line Defence

When pathogens enter the body through stomata or any other way, then
plants produce certain chemicals to kill them. This is called Second
Line Defence.

Phytoalexins

In infected plants an antibiotic phytoalexins is produced which is effective to all micro-organisms.





Biological Clocks



Definition

A control system is found in all living organisms which controls
physiological and metabolic and metabolic functions according to time
is called Biological Clock.

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Biological Rhythms OR Biorhythms



Definition

In living things the behavior activities occur at regular intervals which are called biological rhythms OR biorhythms.





Circadian Rhythms



Definition

[Circa => about; dies => day]

Biorhythms may occur, showing periodicity of about 24-Hours. These
are called Circadian Rhythm, which means about one day, so they are
also called diurnal rhythms.





Causes of Biorhythm



Biorhythms occurs due to the following reasons.

1. Exogenous Stimuli

2. Endogenous Stimuli



1. Exogenous Stimuli

There may be direct response to various changes in the external (exogenous) stimuli.

2. Endogenous Stimuli

These rhythms can be controlled internally by an efficient time
measuring system and are independent of light and temperature effects.
These types of rhythms are called endogenous.





Co - Ordination



Definition

The working together of all parts of the body or system is called Co-ordination.





Types of Co-Ordination



There are two types of Co-ordination.

1. Nervous Co-Ordination

2. Chemical Co-Ordination



1. Nervous Co-Ordination

Definition

Co-Ordination brought about by the nervous system. It is quickest
way of communication take place by electro-chemical messages called
Nerve Impulse within the body of all animals is called Nervous
Co-Ordination.



Elements of Nervous System

The elements o nervous system which help in co-ordination are

i. Receptor

ii. Central Nervous System (CNS)

iii. Effector



i. Receptor

The sensory tissues or organs which receive any change in their
external as well as internal environment (stimuli) are called
Receptors.

ii. Central Nervous System

The receptors convey the stimuli to the control centre, the nervous system (Central Nervous System) through sensory nerves.

iii. Effector

The central nervous system (CNS) analyses stimuli and sends an
appropriate command, through it motor nerves to either endocrine organ
to release hormones into the blood or to muscles called Effectors.



Pathway in Nervous System

There are two types of pathway in the nervous system.

i. Afferent Nerve Pathway

ii. Efferent Nerve Pathway



i. Afferent Nerve Pathway

From receptor the messages are carried to the Central Nervous System
i.e. brain and spinal cord, this pathway is called Afferent Nerve
Pathway.

ii. Efferent Nerve Pathway

From central nervous system the messages are transferred to the effector. This pathway is called Efferent Nerve Pathway.





Nervous Tissues



There are two types of nervous tissues

1. Neurons

2. Neuroglia OR Glial Cells



1. Neurons

Definition

The nervous system consist of special cells which can generate and conduct electric current are called Neurons.

OR

The chief structural and functional unit of nervous system is called Neurons.



Structure of Neurons

Neurons are different from each other according to size and shape but the structure of neuron consists of three parts.

i. Some or Cell Body

ii. Dendrites

iii. Axon



i. Soma OR Cell Body

Each neuron has a cell body or soma containing nucleus and various
organelle embedded in the cytoplasm. Nissl's granules which are group
of ribosomes, associated with rough E.R. and Golgi apparatus are
present in the cell body.

Functions

• The cell body or soma is the main nutritional part of the cell necessary for growth of neuron.

• Soma receive message to dendrites and convey it to axon.

ii. Dendrites

From the soma, a large number of small threads like terminal branches are arises are called Dendrites.

Functions

• Dendrites receive stimuli and convey it to the soma.

iii. Axon

The unbranched, single elongated cytoplasm process which usually arises opposite to dendrites called Axon.

Axon Hillock

Axon originates from a pyramid like area of soma called Axon-Hillock.

Axon Terminal

At the terminal end of axon many fine branches are present called Axon Terminals.

Myelin Sheath

The axon of some neurons is enclosed by a layer of fatty substance known as Myelin Sheath.

This serve as insulating layer.

Functions

Axon is specialized for conducting impulses to other neurons.



Types of Neurons

According to the function, neurons are of the three types.

i. Sensory Neuron

ii. Motor Neuron

iii. Inter Neuron



i. Sensory Neuron

The neurons which transmit impulses from receptor to the central nervous system is called Sensory Neuron or Receptor Neurons.



ii. Motor Neuron

The neurons which transmit instructions of the central Nervous System
to the effector are called Motor Neurons or Effector Neurons.



iii. Inter Neurons

The neurons present between sensory and motor neurons are called Inter Neurons. They are found in Central Nervous System.



Functions of Neurons

• Neurons is the functional unit of nervous system which receives stimuli, transfers them to the Central Nervous System (CNS).

• It transfers the messages from CNS to the body parts effector.

Reflex Action



Definition

The automatic involuntary responses which occur either due to internal or external stimuli are called Reflex Action.

OR

An immediate response to a specific stimulus without conscious control is called a Reflex Action.





Parts of Reflex Action



Reflex action consists of

i. Receptor: (Skin) receive stimuli.

ii. Sensory Neuron: It carries message from receptor to the Central Nervous System (CNS).

iii. Motor Neuron: It carries message from Central Nervous System (CNS) to the effector.

iv. Effector: (Muscle of gland) which perform action.





Reflex Arc



Definition

The pathway of passage in impulse during a reflex action is called Reflex Arc.

Reflexes may be monosynaptic or polysynaptic.

Monosynaptic

The reflex action in which only one synapse is involved is called Monosynaptic.

Example: Knee Jerk

Polysynaptic

The reflex action in which many synapses are involve due to presence of
inter neurons between sensory and motor neurons is called
Polysynaptic.

Example: Hand withdrawal on the painful stimuli.



Examples of Reflex Actions

• If our hand touch any hot object, it is quickly withdrawn.

• Secretion of juices from the gland.

• Blinking of eyes.

• Contraction and expansion of lungs.

• If a strong light is flashed across the eye, the eyelids are at once closed or start blinking.

Nerve Impulse



Definition

The electrochemical signals developed by a neuron for communication is called Nerve Impulse.





Method of Development of Nerve Impulse



The neurons develop impulse in the following way.

1. Resting Membrane Potential (RMP)

2. Action Potential

3. Propagation of Impulse

4. Synapse





Resting Membrane Potential



Definition

A typical neuron at rest is more positive electrically outside than
inside the cell membrane. This net difference in charge between the
inner and outer surface of a non conducting neuron is -65mv is called
the Resting Membrane Potential.





Factors Involved in Resting Membrane Potential



This popularity is due to the unequal distribution of ions across the
neurolemma. The major factors which are involved in resting membrane
potential are



Sodium and Potassium Ions

• There is a greater concentration of sodium ions outside than inside the membrane.

• Similarly potassium ions are concentrated muscle inside than outside the membrane.

• This is attributed to the activity of ATP driven sodium potassium pump in the neurolemma.

Action Potential



Definition

When neuron is stimulated reversal of the polarity of the neurolemma
occurs, first changes to +40mv and then restores to -65mv again is
called Action Potential.

This action potential is extremely rapid as it occurs in a few milliseconds.





Factors Involved in Action Potential



Sodium and Potassium Ions

• The change in potential across the membrane is due to the presence to sodium and potassium channels in the neurolemma.

Changes Associated with Action Potential

Sequence of membrane potential changes associated with an Action Potential.

• Resting Potential

• Sodium gates open and Na+ diffuses into the cell causing a
  depolarization of the membrane from negative to zero and then proceeds
  upto +40mv.

• Sodium gates close and potassium gates open.

• K+ diffuses out, causing a repolarization of the membrane.

• Sodium potassium pump restores original ion gradients and resting potential.

Propagation of the Impulse



Definition

When the action potential develops and spreads along the entire length of neurolemma, it is called propagation of nerve.





Synapse



Definition

The region where the impulse moves from one neuron to another is called a Synapse.





Components of Synapse



It consists of three components

1. Pre Synapting Membrane

2. Synaptic Cleft

3. Post Synaptic Membrane



1. Pre Synaptic Membrane

The membrane of axon terminal is called Pre Synaptic Membrane.

2. Synaptic Cleft

The narrow space between neurons is called Synaptic Cleft.

3. Post Synaptic Membrane

The membrane of dendrites of another neuron is called Post Synaptic Membrane.



Motor End Plate

When it is the membrane of muscle cell it is called motor end plate.

Neurotransmitter

The chemicals present in the vesicles which are released at the axon
ending of the neurons, at synapse are called Neurotransmitter.





Mechanism of Impulse Through Synapse

• When an impulse is reached at axon terminals, the calcium channels are opened.

• From synaptic cleft calcium ions are diffused into the calcium channels.

• Due to this synaptic vesicles fuse with the pre-synaptic
  membrane, causing the release of neurotransmitter molecules into the
  synaptic cleft.

• The neurotransmitter bind to the receptors on the
  post-synaptic membrane, which generate action potential in the
  post-synaptic cell.

• The neurotransmitters are then reabsorbed by the pre-synaptic cells for reuse.

Examples of Neurotransmitter

Many different types of neurotransmitter are known. These are
acetylcholine, norepinephrine, glycine, gab a, serotonin, dopamine etc.






Evolution of Nervous System



In different group of animals two types of nervous systems can be recognized, which are

1. Diffused Nervous System

2. Centralized Nervous System



1. Diffused Nervous System

Diffused Nervous System is found in cnidarians and Echinoderms.

Nervous System of Hydra

• In these animals, no anterior and posterior ends is present and their body is radially symmetrical.

• The nerves cells are found in the form of network throughout the body.

• The flow of information is not highly directional and it diffuses in all directions.

• The transmission of impulses is slow because of synapses involved.

• There is no brain but the nerve cells constitute the nervous system.

2. Centralized Nervous System

Centralized Nervous System found to varying degrees in more complex
organisms from platyhelminthes to chordates including humans.

Nervous System of Planaria

• In these animals, definite anterior and posterior ends is present and their body is bilaterally symmetrical animals.

• It consists of an anterior brains (a concentration of neurons) which is connected with the Sensory Organs.

• From the brain arise two cord like nerves running longitudinally through the body.

• The two nerve cords are connected with each other at several points through the transverse nerves.

• They co-ordinated the movement of the two lateral sides of the body.

Nervous System of Man



The nervous system of man is the most advanced, highly developed. It
controls all functions of the body. It consists of two parts

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)



1. Central Nervous System (CNS)

Definition

The nervous system consists of brain and spinal cord (hollow nerve
cord) and also consists of upto 100 billion inter neurons is called
Central Nervous System (CNS).

Components of Central Nervous System

The central nervous system consists of

• Brain

• Spinal Cord

Protection of Central Nervous System

Brain and spinal cord both are protected in three ways

i. Cranium

ii. The Vertebral Column

iii. Meninges

iv. Cerebrospinal Fluid (CSF)



i. Cranium

Cranium, which is part of skill, protects the brain.

ii. Vertebral Column

Neural arches of vertebrate of vertebral column protect the spinal cord.

iii. Meninges

Beneath the cranium, the brain and spinal cord are protected by triple layers of tough connective tissues called meninges.

iv. Cerebrospinal Fluid (CSF)

Between the layers of meninges, there is a plasma like fluid which
bathes the neurons of brain and spinal cord is called Cerebrospinal
Fluid (CSF).

It cushions against the bumps and jolts.



2. Peripheral Nervous System (PNS)

Definition

The nerves arises from brain and spinal cord that are spread in
various part of body which transmits the signals between CNS and body
parts make a nervous system called Peripheral Nervous System.

The peripheral nervous system consists of two types of nerves.

i. Cranial Nerves

ii. Spinal Nerves



i. Cranial Nerves

In humans, there are 12 pairs of nerves which arise from the brain or
lead to the brain these nerves are called cerebral or cranial nerves.

ii. Spinal Nerves

In humans, there are 31 pairs of nerves which arise from the spinal cord or lead to the spinal cord are called spinal nerves.



Types of Peripheral Nervous System

The peripheral nervous system is divided into two types according to their functions.

1. Somatic Nervous System

2. Autonomic Nervous System



1. Somatic Nervous System

The peripheral nervous system which controls all the voluntary
activities of the body such as contraction of skeletal muscles and
movement of joint is called Somatic Nervous System.

2. Autonomic Nervous System

The autonomic nervous system which controls involuntary activities of
the body such as smooth muscles, glands, muscles of heart and other
internal organs is called Autonomic Nervous System.

Types of Autonomic Nervous System

Autonomic nervous system divided into two types

i. Para Sympathetic Nervous System

ii. Sympathetic Nervous System



i. Para Sympathetic Nervous System

The autonomic nervous system formed by some cranial nerves, vagus
nerves and the spinal nerves that are arising from the sacral
vertabrate are called Para Sympathetic Nervous System.

ii. Sympathetic Nervous System

The autonomic nervous system whose nerves arise from the thoracic and
lumber regions of spinal nerves is called Sympathetic Nervous System.

Functions

This system is important during emergency situation and is associated
with "flight or fight". It increases the heart beat, breathing rate,
slows digestion, dilates pupil etc.

Brain



Definition

The most important part of Central Nervous System develops from
dorsal, hollow nerve cord well protected in the cranium of skull and
composed of inter neurons and is the seat of our intelligence, learning
and memory is called Brain.





Part of Brain



The brain consists of three parts

1. Fore Brain

2. Mid Brain

3. Hind Brain



1. Fore Brain

Fore brain can be divided into two regions

i. Telencephalon

ii. Diencephalon



i. Telencephalon

The largest part of fore-brain which is differentiated into two cerebral hemisphere or cerebrum is called Telencephalon.



Cerebrum

Cerebrum is the largest part of the brain and is divided into two halves called Cerebral Hemisphes.

Cerebral Hemisphere

Each hemisphere consist of an outer grey matter or cerebral cortex and an inner white matter.

Cerebral Cortex

• Cerebral cortex is the largest and the most complex part of human brain.

• It is highly convulated to occupy the greater number of inter neurons.

Corpus Callosum

The two cerebral hemisphere communicate with each other by means of large band of axons called Corpus Callosum.

Part of Cerebrum

Functionally, the cerebrum is differentiated into four lobes.

• Anterior Frontal Lobe

• Lower Central Temporal Lobe Parietal Lobe

• Dorsal Occipital Lobe

Function of Cerebrum

• Cerebrum is concerned with intelligence memory, learning, resoning and overall control of all voluntary actions.

• It involved in all conscious activities.

• It co-ordinated different senses together.

2. Diencephalon

The diencephalons consists of two parts

i. Thalamus

ii. Limbic System



i. Thalamus

The clearing house for sensory impulses is called Thalamus.

Functions

• It receives them from different parts of brain and relays them to the appropriate part of the motor cortex.

• It also involves in the perception of pleasure and pain.

ii. Limbic System

The limbic system is located in an are between the thalamus and cerebrum.

Parts of Limbic System

The limbic system consists of

i. Hypothalamus

ii. Amygdala

iii. Hippocampus



i. Hypothalamus

Hypothalamus is the part of limbic system which is called Thermostal of the body.

Functions

• The hypothalamus is important in regulation of homeostasis.

• It regulates pituitary gland.

• It also regulate body temperature, blood pressure, hunger, thirst, aggression, pleasure and pain.

ii. Amygdala

The amygdala produces sensation of pleasure, punishment or sexual arousal stimulation.

It also involve in the feelings of fear.



iii. Hippoc Ampus

Hippocampus is involved in long term memory.





Mid Brain



In mammals mid brain is relatively very small. It consists of the optic lobes which are represented by four small bodies.



Functions

It receives sensory information like vision, odour etc. It receives
sensory information from spinal cord and sends them to the fore brain.





Hind Brain



Hind brain consists of

1. Medulla Oblongata

2. Cerebellum

3. Pons

4. Reticular Formation



1. Medulla Oblongata

Medulla oblongata lies on the top of spinal cord.

Function

• It controls involuntary actions like blood pressure, heart
  beat, sneezing, coughing, breathing rate, hicupping, swallowing etc.

2. Cerebellum

The cerebellum lies dorsally behind the optic lobes. It is highly convoluted. It is large in mammals than other animal.

Functions

• The cerebellum plays an important part in controlling muscular co-ordination.

• It specially maintains balance and also position of the body in space.

3. Pons

Pons regulates activities like muscular co-ordination, facial expressions, breathing and sleeping.



4. Reticular Formation

Reticular formation lies in pons, medulla and mid brain.

Functions

• It monitors the messages to the brain which should be ignored or should be realized.

Brain Stem



The oldest tissues formed by the combination of medulla oblongata, pons and mid brain is called as Brain Stem.

Functions

• It involved in the control of sleep and wakening.

Spiral Cord



Definition

A thick whitish nerve cord that lies below the medulla oblongata and
extends down through the neural canal of vertebrate upto the hips is
called Spinal Cord.





Cross Section of Spinal Cord



In cross section, the spinal cord is differentiated into two areas.

• White Matter

• Gray Matter

Unlike brain, spinal cord has grey matter inside surrounded by
white matter on the outside. They grey matter has the shape of an "H".
The first synapse of each sensory neuron is located in the grey matter.




Central Canal

The narrow central containing cerebrospinal fluid runs through the
middle of the spinal cord. This fluid brings nutrients to the spinal
cord.





Spinal Nerves



The nerve arises from spinal cord is called Spinal Nerves.

• Each spinal nerve divides into two roots just before it joins spinal cord.

1. Dorsal Root

2. Ventral Root



1. Dorsal Root

The dorsal root joints the dorsal part of the spinal cord and it contains axons of sensory neurons.

Dorsal Root Ganglion

The cell bodies of these neurons aggregate in a small swelling known as the dorsal root ganglion.



2. Ventral Root

The ventral root which is attached to the ventral part of the spinal
cord carrying axons of motors neurons, arised from the spinal cord.

Functions of Spinal Cord

• Spinal cord serves as an express way for signals between autonomic nervous system.

• It is also the control centre for many reflexes.

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Receptors



Definition

The single or group of either modified neurons or epithelial cells
which receive stimuli either from external environments and relaying
them in the form of impulses to the CNS are called Receptors.



Receptionists

The receptors are acts as receptionist of nervous system because they
receive any kind of change, which is then transferred to the brain and
spinal cord.



Sensation

Receptor converts stimuli into nerve impulses, this stage awareness of stimulus is called Sensation.



Perception

In the control centre of the nervous system, the impulses are converted into perception.





Types of Receptors



Receptors are classified according to type of stimulus which they can
detect and give response. Following are some types of receptor.



1. Thermoreceptor

The receptors which detect and respond to temperature fluctuations (heat and cold) are called Thermoreceptor.

2. Chemoreceptor

The receptors which can detect and respond to presence of certain chemicals in their surrounding are called Chemoreceptor.

3. Mechanoreceptor

The receptors which can detect the stimuli of sound, motion, touch, pressure gravity and movement are called Mechanoreceptor.

4. Photoreceptor

The receptors which respond to the stimulus of light and ultraviolet rays are called Photoreceptor.

5. Pain Receptor

The receptors which produced sensation of pain or damage tissues are called the Pain Receptor.





Working of Sensory Receptors in Skin



In human, the receptors in skin are concerned with at least five different senses i.e., touch, pressure, cold, warm and pain.



Types of Sensory Receptor in Skin

There are two types of sensory receptors in the skin.

i. Free Nerve Ending Receptors

ii. Encapsulated Receptors



i. Free Nerve Ending Receptors

The simplest types of receptor which contain free end without any
protective capsule and are located just beneath the epidermis are
called Free Nerve Ending Receptors.

Functions

Free nerve ending receptors adapt very slowly to stimulation.

Types

They are of different types



a. Mechanoreceptors Receive touch and pressure.

b. Nociceptors Feel pain

c. Thermoreceptors Feel change in temperature



ii. Encapsulated Receptors

The type of receptor contain a protective capsule of connective tissues
at their ends and lie in skin are called Encapsulated Receptors.

Types

Encapsulated receptor are of following two types

i. Meissner's Corpuscles

ii. Pacinian Corpuscles



i. Meissner's Corpuscles

The encapsulated receptors that are found in those parts which do not
have hairs such as finger tips, eyelids, lips palms, soles, nipples etc
are called Meissner's Corpuscles.

Structure of Capsule

Their capsules consists of thick collagen fibers with spiral and highly coiled nerve endings.

Function

There are touch receptors means very sensitive to touch.



ii. Pacinian Corpuscles

The encapsulated receptors which are found in dermis layer and also in
some internal organs and moveable joints are called Pacinian
Corpuscles.

Structure

Their nerve endings are surrounded by an onion like capsule made of
concentric layers of membrane. Between the membranes fluid filled
spaces are present.

Functions

They are pressure receptor and detect rapid and deep pressure changes produced by vibration and touch.



Sensory Receptors with Reference to Arteries

The aortic arch and the carotid artery contain many receptor which are

Mechanoreceptor

They detect the pressure changes in arteries.

Baroreceptor

They detect the pulse pressure



Function

These receptors transfer these changes to the medulla oblongata which controls blood pressure.



Aortic Body and Carotid Body

The aortic arch and the carotid sinus also contain chemoreceptor called Aortic body and carotid body.

Function

They are sensitive to CO2 concentration and hydrogen ion concentration of the blood.

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Effects of Drugs on Co-Ordination



Drugs



A chemical substance that causes the specific physiological response in the body are called drugs.

Importance

• Many drugs are useful medically to treat emotional stress or certain illness.

• Drugs which people take to alter the mood or emotional
  state affect body functional interfering with the working of
  neurotransmitters.

• Therefore their abuse often causes harmful effects.

Nicotine

• It is a drug found in tobacco.

• It acts as a stimulant and is widely used as a neurological agent.

• Nicotine affects post synaptic membrane in CNS and PNS.

• It minimize the action of acetylcholine on nicotine receptors. So it is stimulant to nerve impulse.

• It increase the heart beat, rate, blood pressure and digestive tract mobility.

• Nicotine may induce vomiting and diarrhea.

• It may cause water retention relation by kidneys.

• It stimulate the nervous system thereby reducing fatigue, increasing, alertness and improving the concentration.

Nervous Disorders



The abnormalities appear in brain, spinal cord, central nervous system
and peripheral nervous system causes diseases called Nervous
Disorders.

Some common disorders of nervous system are as follows

1. Parkinson's Disease

2. Alzheimer's Disease

3. Epilepsy



1. Parkinson's Disease

It is a brain disorder.

Causes

It either caused by degeneration or damage of nerve tissues within the basal ganglia of the brain.

Symptoms

It is characterized by involuntary tremors, diminishing motor power and
rigidity. It causes stiffness, weakness and trembling of the muscles.
The mental faculties are not affected.

Treatment

Leopoda is the effective medicine which is helpful in minimizing the
symptoms by can not halt the degeneration of neurons of brain.



2. Alzheimer's Disease

It is the progressive degeneration of neurons of brain, especially cortex and hippocampus.

Causes

There is a genetic pre-disposition to the disease in some people, so it tends to run in families.

Stages of Diseases

The disease progresses in three broad stages.

First Stage

At first, the patient notices his forgetfulness.

Second Stage

In second phase, there is a severe loss of memory particularly for
recent events. Anxiety increases with sudden changes in mood.

Third Stage

In the third and last stage the disease become severe. He losses
memory, hears voices or see faces in the absence of any person. This
disease is called Hallucination. He does not share his ideas and does
not accept ideas of other persons, such disease is called paranoid
delusions.

Symptoms

The main symptom of the disease is the loss of memory called dementia.

Treatment

• Effective medicines should be used.

• Psychological treatment is better to control the disease.

• Personal care of patient is necessary otherwise he may get any harm.

Chemical Co-Ordination



Definition

The co-ordination brought about by the endocrine gland system. It is
not very rapid, but shows slow and prolonged effect takes place by
chemical substances called hormones and neurotransmitter within the
body of all animals is called Chemical Co-ordination.

Endocrine glands secreat their secretions (hormones) directly into the
blood stream. They are transported by the blood to the target cells.





Types of Hormones



Chemically the hormones are organic compounds which are classified into three types.

1. Peptide Hormones

2. Modified Amino Acids Hormones

3. Steroid Hormones



1. Peptide Hormones

The hormones which are composed of protein are called Peptide Hormone. There are two types of peptide hormones.

i. Small Chain Amino Acids

ii. Large Chain Amino Acids



i. Small Chain Amino Acids

The peptide hormones consists of small chain of amino acids are called Small Chain Amino Acids.

Examples

• Glucagon

• Antidiuretic Hormone (ADH)

• Oxytocin

ii. Large Chain Amino Acids

The peptide hormones consists of long chain of amino acids are called Large Chain Amino Acids.

Example

• Insulin

• Preleclin

2. Modified Amino Acid Hormones

The hormones consists of modified amino acids are called Modified Amino Acid Hormones.

Example

• Thyroxine

• Epinephrine

• Nor-epinephrine

3. Steroid Hormones

The hormones which are composed of lipid are called Steroid Hormones.

Example

• Estrogen

• Progesterone

• Testosterone

• Aldisterone

Hormone Action



To explain the action of hormones two models have been proposed.

1. First Model

2. Second Model



Similarity Between Both Models

Both model agree that the plasm membrane of cells contain certain receptors to accept the hormones.

Dissimilarity Between Both Models

After receiving the hormones continue their way of action called signal transduction pathway. It is different in both models.



1. First Model

According to the first model peptide hormones are involved. The
receptor molecule is attached to an enzyme adenylate cyclase in the
inner part of plasma membrane. The hormone is attached to the receptor.
By the activity of enzyme ATP molecule is changed into cyclic adenosine
monophosphate (AMP) in the cytoplasm. The cyclic (AMP) acts as a
second messenger and activates the particular enzyme which actually
helps in the function. Some other messenger molecules also take part in
the process.



2. Second Model

According to the second model, steroid hormones are involved. These
hormones are fat soluble, so they enter the cell directly through the
plasma membrane, so they do not need second messenger. In the cytoplasm
they are attached to the particular receptors which transfer into the
nucleus. In the nucleus. In the nucleus hormone receptor complex
activities the genes due to which actual function is started.





Functions of Hormones

• They do not initiate new biochemical reactions but produce
  their effects by regulating the enzymatic and other chemical reactions,
  already present.

• They may either stimulate or inhibit a function.

• Hormones may also control some long term changes, such as rate of growth, rate of activity and sexual maturity.

Endocrine System



Definition

Endo => Inside => Krinein => separate i.e. to secrete.

In the body of vertebrates there are certain dustless gland which
poured their secretions (hormones) directly into the blood or in body
fluids are called endocrine glands or ductless glands constitute a
system called Endocrine System.





Endocrine Glands of Man



In the body of man and other mammals, following important endocrine glands are mostly found.

1. Hypothalamus

2. Pituitary Gland

3. Thyroid Gland

4. Parathyroid Gland

5. Pancreas

6. Adrenal Gland

7. Thymus Gland

8. Pineal Gland

9. Gonads



1. Hypothalamus

The part of forebrain which forms a connection between Nervous System and endocrine system is called Hypothalamus.

Hormones

The hypothalamus contains specialized nerve cells called neurosecretory cells which produced two types of hormones.

i. Releasing Hormone

ii. Inhibitory Hormone



i. Releasing Hormones

The hormones which are produced to increase the secretion of another glands are called Releasing Hormones.

Function

Releasing hormone control the secretion of hormones from pituitary gland.



ii. Inhibitory Hormones

The hormones which are produced to prevent the extra secretion of hormones are called Inhibitory Hormones.

Function

Hypothalamus produced two hormones which are

• Oxytocin

• Antidiuretic Hormones (ADH)

These two hormones are stored in the posterior lobe of pituitary gland.



2. Pituitary Gland (Hypophysis)

Pituitary gland is called "master gland" because it controls the secretion of other endocrine glands.

Location

The pituitary gland is located in the brain. It is attached to the base of hypothalamus by short.

Size

The pituitary gland is small pea size gland.

Lobes of Pituitary Gland

Pituitary gland has three lobes

i. Anterior Lobe

ii. Median Lobe

iii. Posterior Lobe



i. Anterior Lobe

Anterior lobe produces three types of hormones which are

a. Tropic Hormone

b. Growth Hormone or STH

c. Prolactin



a. Tropic Hormone

The hormones which control the activity of other hormones are called Tropic Hormones.

Kinds of Tropic Hormone

The tropic hormone secreted by the pituitary gland are as follows

Thyroid Stimulating Hormone (TSH)

It control the working of thyroid gland including secretion of thyroxin.

Adreno-Cortico Tropic Hormone (ACTH)

In controls the activity of outer part of cortex of adrenal gland.

Follicle Stimulating Hormone (FSH)

FSH in females stimulate follicle developing and secretion of oestrogens from the ovaries.

In males it stimulates development of the germinal epithelium of the testis and sperm production.

Leutinizing Hormone (LH)

This hormone helps in the formation of sperms and testosterone hormone
in male. In female it takes part in ovulation i.e. release of ovum from
the ovary.



b. Growth Hormone OR Somatotropin Hormone (STH)

It regulates the normal growth by controlling many metabolic processes,
such as protein synthesis, involved in growth of bones and soft
tissue.



c. Prolactin Hormone

This hormone stimulate mammary glands and production of milk.



ii. Median Lobe

Median lobe produced one hormone called Melanocyte Stimulating Hormone (MSH).

Functions

This hormone controls darkening of skin in many vertebrates. In human,
very small amount of MSH is produced by the anterior pituitary rather
than median.



iii. Posterior Lobe

From posterior lobe of pituitary gland following hormones are secreted.

a. Antidiuretic Hormone (ADH)

b. Oxytocin



a. Antidiuretic Hormone (ADH)

It stimulates the re-absorption of water by tubules of kidney and thus decreases the amount of urine passed.

b. Oxytocin It stimulates contraction of muscles of uterus during child birth and release of milk during breast feeding.



Abnormal Conditions Due to Pituitary Gland

Due to abnormal production of somato tropic hormone (STH) or growth hormone, following abnormalities occur.

i. Gigantism

ii. Dwarfism

iii. Acromegaly



i. Gigantism

It is disease of childhood.

Causes

It occurs due to over secretion of somatotropic hormones (STH) or growth hormone.

Symptoms

The affected individuals becomes abnormally tall.



ii. Dwarfism

It is a disease of childhood.

Causes

It caused due to less secretion of somato tropic hormone or growth hormone.

Symptoms

The affected individuals becomes abnormally short.



iii. Acromegaly

It is a disease of adulthood.

Causes

It occurs due to overproduction to somatotropic homrone (STH).

Symptoms

In this condition, hands, feet and jaw bones and cartilages and soft muscles become larger in size and swollen.



3. Thyroid Gland

Location

Thyroid gland is located in the neck region in front of trachea. It consists of two lobes, one on either side of trachea.

Shape

It is butterfly in shape.

Secretions

It secreats three main main hormones.

i. Thyroxine or T4 (Tetra lodo Thyroxine)

ii. T3 (Tri lodo Thyroxine)

iii. Calcitonin



i. Thyroxine OR T4

• Thyroxin increases the metabolic rate and promotes both physical growth and mental development.

• It increases the oxygen consumption and production of heat.

ii. T3 Hormone

• Tri lodo thyroxine performs the same function as that of thyroxine or Tetra lodo Thyroxine.

iii. Calcitonin

• Calcitonin plays and important role in calcium homeostasis.

• Calcitonin is produced when calcium Ca++ level is increased in blood.

• It respond to decreased the blood calcium level by stimulating the deposition of excess calcium in bones.

Abnormalities of Thyroid Gland

There are two conditions of abnormalities of Thyroid Gland.

i. Hyperthyroidism

ii. Hypothyroidism

i. Hyperthyroidism

The state of over secretion of hormones by thyroid gland is called Hyperthyroidism.

Due to hyperthyroidism following symptoms usually appear.

• High blood pressure

• Increase body temperature

• Intolerance to heat

• Profuse sweating

• Loss in weight etc

ii. Hypothyroidism

The state of deficiency of T4 and T3 hormones is called Hypothyroidism.

It causes following diseases

i. Myxedema

ii. Goiter

iii. Cretinism



i. Myxedema

It occurs in adult stage.

Causes

It occurs due to the deficiency of T3 and T4 Hormones

Symptoms

Myxedema produces following symptoms

• Overweight (Obesity)

• Loss of hairs

• Dry Skin

• Mental activity or body movement become slower

• Intolerance to cold

ii. Goiter

Causes

It occurs due to deficiency of iodine in diet which results in decreased level of thyroxin hormones (T3 and T4).

Symptoms

• Thyroid gland works more than normal to produce more thyroxine. As a result of which they become swollen and enlarged.

iii. Cretinism

It is disease of childhood.

Causes

It occurs due to deficiency of thyroxin hormone in early age, such
persons are called cretinism and the mechanism is known as cretinism.

Symptoms

This disease shows following symptoms

• Mental retardation

• Stunted growth

• Physical weakness

• Abnormal facial features

4. Parathyroid Gland (PTG)

Location

Parathyroid glands are present in the neck regiort with two parts of thyroid gland.

Size

Their size is like pea seeds.

Secretion

Parathyroid gland secrete only one hormone called Parathyroid Hormone (PTM).

Function

• Parathyroid hormone plays an important role in calcium's homeostasis.

• Parathyroid hormone is produced when calcium Ca++ level is decreased in blood.

• It response to increased the calcium ion in blood in two ways.

• It increase the absorption of calcium ions in kidney.

• It induces the bone cells (Osteoblasts) to released
  calcium from bones into the blood. This process is called
  Demineralization.

Abnormalities of Parathyroid Gland

Abnormalities in parathyroid gland usually produces two diseases.

i. Tetany

ii. Rickets

i. Tetany

Deficiency causes a drop in blood Ca++ which in turn leads to muscular tetancy.

ii. Rickets

Over production would lead to a progressive demineralization of the
bones similar to tickets, as well as to the formation of massive kidney
stones.



5. Pancreas

Pancreas is a gland which acts as both exocrine and endocrine gland.

Location

Pancreas is located in abdominal cavity below the liver.

Islets of Langerhans

The cells of pancreas are called Islets of langerhans.

• They perform the function of endocrine gland.

• This is under control of the pituitary trophic hormones
  STH and ACTH and responds directly to the level of blood glucose which
  is normally 90ms/100mg.

• The islets of langerhans are of two distinct types.

i. Alpha Cells

ii. Beta Cells

i. Alpha Cells (α-cells)

Alpha cells secreat hormone called Glucagon.

ii. Beta Cells (β-cells)

Beta cells secreat hormone called Insulin.



Glucagon

• It is secreted in response to decrease sugar level in blood.

• It increase the blood glucose level mainly by promoting breakdown of glycogen to glucose in the liver and muscles.

• It also increase the rate of breakdown of fats.

Insulin

• It is secreted in response to increase sugar level in blood.

• It decrease the blood glucose level mainly by following mechanism:

i. It increases glycogen synthesis in liver and also increasing cell utilization of glucose.

ii. It also stimulates both lipid and protein synthesis which reduces glucose level.

iii. Insulin inhibits the hydrolysis of glycogen in the liver and muscles.



Disorders of Insulin Deficiency

Due to deficiency of insulin, a diseased appeared called Diabetes mellitus.

Diabetes Mellitus

When there is deficiency of insulin, the amount of sugar is increased in blood, it is called Diabetes Mellitus.

Symptoms

• High level of blood sugar

• Sugar in the urine

• Disturbance of the body's osmotic equilibrium

• Dehydration

• Derangement of the nervous system

Types of Diabetes Mellitus

There are two types of Diabetes Mellitus.

i. Insulin Dependent Diabetes

ii. Insulin Independent Diabetes

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6. Adrenal Gland

Location

A pair of adrenal gland is present, one on the top of each kidney.

Structure

Each adrenal gland has two distinct parts

1. Adrenal Cortex

2. Adrenal Medulla



1. Adrenal Cortex

The outer layer of adrenal gland is called Adrenal Cortex. It is
controlled by the adrenocorticotropic hormone (ACTH) secreted from
Pituitary Gland.

Secretions

Adrenal cortex produces many hormones which are collectively called as Corticosteriods.

Functions

• These hormones are very important for regulating carbohydrates metabolism.

• They are also essential for maintaining mineral balance in the body.

• The important corticosteroid hormones are as follows.

1. Cortisol

2. Aldosterone

3. Androgen



1. Cortisol

• This hormone is produced at the time of fever and diseases.

• It converts protein of muscles into amino acids, which are changed into glucose by the activity of liver.

• In this way there is continue supply of energy in the body.

• It reduces pain and inflammation in the body.

Over Secretion of Cortisol

Over secretion of cortisol causes a disease called Cushing's Syndrome.

Cushing's Syndrome

Symptoms

• Obesity

• Breakdown of Muscles

• Diabetes

Deficiency of Cortisol

Deficiency of cortisol causes a diseases called Addison's Disease.

Addison's Disease

Causes

It is due to defect in auto immune system.

Symptoms

• Loss in weight

• Weakness

• Low level o sugar

• Low blood pressure

Aldosterone

• This hormone helps in the reabsorption of Na++ and Cl- ions by the help of kidney.

• It raises the blood pressure and blood volume.

Androgen

• It causes development of the secondary male characteristics,
  such as hairs on face, depending of voice and increase in muscle size.
  It is like a testosterone.

• When their amount in female in increased, hairs are produced on the face of female.

2. Adrenal Cortex

The inner layer of adrenal gland is called Adrenal Medulla.

• Adrenal medulla works under the influence of sympathetic nervous system.

Secretions

Adrenal Medulla produces many hormones which are collectively called as
Emergency Hormones. Both are secreted in stress situation.

The important emergency hormones are

i. Adrenaline OR Epinephrine

ii. Nor-Adrenaline OR Nor-Epinephrine



i. Adrenaline OR Epinephrin

• It increase heart rate, amount of glucose in blood, rapid respiration and metabolism during emotions and emergency.

• It also takes part in the contraction of blood vessels in intestine and dilation of blood vessels in muscles.

ii. Non-Adrenaline Or Nor-Epinephrine

• It also functions like epinephrine, but its main function is control of blood pressure during fight and flight.

• The over secretion of both these hormones causes high blood pressure.

7. Thymus Gland

Location

It is present in the upper region of thorax, behind the breast bone. It
consists of two parts which are attached together in the front region
of trachea.

Structure

It secret hormone called Thymosine.

Function

Thymosine controls the production of Thymphocytes and also their
differentiation. These are the cells of immune system and control the
infection of virus bacteria.



8. Pineal Gland

Location

Pineal gland is a tiny gland present at the upper side of diencephalons in the brain.

Secretion

Pineal gland secretes a hormone called Melatonin.

Functions

• Metatonin regulates the seasonal reproductive cycles.

• It also regulates the growth and development of gonad in many mammals.

• It controls the sensation of light and darkness of eyes.

• It produced a/c to the time of day, night or weather.

8. Gonads

The testes and ovaries also functions as endocrine glands and produce
sex hormone chemically sex hormones are steroids. Secretion of gonadial
hormones is controlled by gonadotropic hormones pituitary gland.



i. Testes

Testes are the male reproductive organs.

Secretion

Testes produced male sex hormone called Testosterone.

Functions

• Tests is responsible of sexual maturity and development of
  secondary sexual characts such as appearance of beard and moustache in
  males.

• It also stimulates the growth of bones and muscles.

ii. Ovaries

Ovaries are female reproductive organs but they acts as endocrine glands.

Secretion

Ovaries secrete two hormones called as

i. Oestrogen

ii. Progesterone



i. Oestrogen

Oestrogen causes development of female secondary sexual characters.

It also helps in thickening of the wall of uterus and prepare it for implantation of fertilized ovum.

ii. Progesterone

It is concerned with maintenance of pregnancy by preventing the contraction of walls of uterus

Read more: Chapter 3 - Co-Ordination