CONTROL AND COORDINATION

Nervous System

Stimuli

The changes in the environment to which living organisms respond are called stimuli. Eg :- heat, cold, sound, smell, taste, touch, pressure, gravity, water etc. Living organisms respond to stimuli in the form of body movements.

Coordination :- For a proper response to a stimulus many organs in the body should work together. The working together of various organs in an organism to produce a proper response to a stimulus is called coordination. i) In animals control and co ordination is done by the nervous system and endocrine system. ii) In plants control and co ordination is done by chemical substances called plant hormones or phytohormones.

Coordination in animalsIn animals control and co ordination is done by the –

Nervous system

ENDOCRINE SYSTEM

Nervous system of Human Nervous system

CNS PNS

Central nervous system includes Brain and Spinal Cord .

Peripheral nervous system includes cranial nerves and Spinal nerves .

NEURON (Nerve Cell)

Neuron is the structural and functional unit of nervous system .

Neuron has following parts. 1. Cyton- It is main cell body with

nucleus ,cell organelles and nissil’s granules. From Cyton ,dendrites and axon are arised.

2. Axon- Axon is the long process ,conducts nerve impulse. It is coated by Myelin sheath. Uncoated points are called as “Ranvier Node”.

Terminal points of axon are known a “Teledendria”.

Synapse-The junction between two neurons or with muscles is called synapse.

Human Brain

Brain is the most important part of

our nervous system.

It is present inside our skull and

protected by cranium.

It is covered by three membranes

called “Meninges” filled with a fluid

called cerebrospinal fluid .

These membranes protect the brain

from shocks.

Structure of Human Brain

Brain is divided into three regions –

1.Fore brain

2.Mid brain

3.Hind Brain

Fore brain

Fore brain includes “Cerebrum & Thalamus”.

Cerebrum – It is the biggest part of the brain. It is divided into two hemisphere. Each hemisphere is divided into four lobes –

Frontal – Muscular activity Occipital - Visual receptionTemporal –Auditory reception. Parietal - Touch ,smell ,

temperature and conscious association.

Fore brain is the thinking part of the brain .It controls voluntary actions , touch , smell, hearing ,mental activities learning ,Memory and emotions.

Midbrain and Hind brainMid brain –It connects forebrain and

hind brain. It controls reflexes involving eyes and ears .

Hind brain-It includes three parts-Cerebellum- It is second big part of brain.It controls muscular

movement, body posture and equilibrium .

Pons- it controls respiratory activities.Medulla oblongata- It controls

involuntary activities like coughing ,vomiting, sneezing, blood pressure etc.

Spinal cordThe spinal cord starts from the brain (Medulla Oblongata) and extends through the vertebral column. It has 31 pairs of spinal nerves. It carries messages to and from the brain. It also controls reflex actions.

Spinal cord has “Gray matter” surrounded by “White matter”. Sensory and motor nerve are arised from spinal cord.

Reflex action

Reflex action is a sudden, unconcious and involuntary response of the effectors to a stimulus. Ex :- We suddenly withdraw our hand if we suddenly touch a hot object. In this reflex action, the nerves in the skin (receptor) detects the heat and passes the message through the sensory nerves to the spinal cord. Then the information passes through the motor nerves to the muscles (effector) of the hand and we withdraw our hand.

Reflex arc

The pathway of a reflex action is called reflex arc. In a reflex arc the stimulus is received by the receptors (sense organs) and it passes through the sensory nerves to the spinal cord. From the spinal cord the information passes through the motor nerves to the effectors (muscles/glands) for the response.

Peripheral Nervous systemSomatic nervous system(SNS)It is voluntary nervous system. It

is associated with the voluntary control of body movement . It includes cranial nerves and spinal nerves.

Autonomic nervous system(ANS)It is non-voluntary nervous

system. It is of two type- (i) Sympathetic Nervous

system- This system makes our body for action.

(ii) Para sympathetic nervous system- This system brings our body in resting condition.