Chapter : Control and Coordination - Notes of Nervous system

CHAPTER 7 – CONTROL & COORDINATION

KEY CONCEPTS & GIST OF THE LESSON

˜  Coordination-The working together of various organs of the body of an organism in a proper

      manner to produce appropriate reaction to a stimulus is called coordination.

  Example : Withdrawal of hand on touching a hot object.

Control and Coordination in Animals

It is brought about in all animals with the help of two main systems

(a) Nervous System

(b) Endocrine System

Nervous System

Parts of the Nervous system – (i) Brain (ii) Spinal cord (iii) Nerves (Neurons)

Functions

(i) To receive the information from environment

(ii) To receive the information from various body parts.

     (Stimuli ® Response)

(iii) To act accordingly through muscles and glands.

Stimulus : Any change in environment to which the organisms respond and react is called stimulus. E.g., touching a hot plate.

Response : The reaction of our body to a stimulus. E.g. withdrawal of our hand on touching hot plate.

How do we detect that we are touching a hot object?

Receptors : Are specialised tips of some nerve cells that detect the information from the environment.

Receptors Are present in  Sense Organs

Photo receptors   Thermo/Thigmo      Phonoreceptors      Olfactory Receptor  GustatoryReceptor

                               receptors

      Eyes                   (Skin)                     Ear                                (Nose)                      (Tongue)

   Visual                    Pain                      Hearing/Balance              Smell             Taste Detection

    Stimulus               Touch                    Of the body

                                   Heat                      Detection

Neuron : It is the structural and functional unit of nervous system.

Neuron has 3 main parts:

1.      Dendrite    : Information is acquired.                  

2.      Cell body   : Information travels as an electrical impulse.                   

3.       Axon         : Information travels as an electrical impulse.                   

Synapse : Part where electrical signal is converted into chemical message for onward        

                 transmission to next neuron by release of neurotransmitters.

Synapse :  Space/junction between two adjacent nerves (between the terminal branches of axon of one neuron with the dendrite of another neuron) is called Synapse.

v Passing of information takes place – (i) By Electric impulse (inside the neuron) and

                                                                   (ii) In the form of chemicals (At synapse)

v Nervous system

Stimulus → Receptor organ → Sensory nerve → Brain/Spinal cord

                                                                                     ↓

                       Response ← Effector organ ← Motor nerve

v Endocrine system

   Stimulus → Endocrine organ → Secrete hormone → Hormone in blood

                                                                                               ↓

                                                             Response ← Target organ

REFLEX ACTION

Reflex action is quick, sudden and immediate response of the body to a stimulus.

- Spontaneous, involuntary and automatic response to a stimulus to protect us from harmful situations.

 Eg. On touching a hot object unknowingly we instantly withdraw our hand, knee jerk etc.

Reflex arc : The pathway through which nerve impulses pass during reflex action is called reflex arc.

Stimulus → Receptor organ → Sensory nerve → Spinal cord →Motor nerve →Effector organ→ Response

Response

Responses are of three main types

1.      Voluntary : Controlled by fore brain

           eg. Talking, Writing

2.      Involuntary : Controlled by mid and hind brain

          eg. Heart beat, vomiting, regulation of heartbeat

3.      Reflex action : Controlled by spinal cord

           eg. Withdrawl of hand on touching a hot object.

v Nervous system- (1) Central Nervous system (CNS) –i) Brain

                                                                                             ii) Spinal cord

                                   (2) Peripheral Nervous system(PNS)- i) Cranial nerves-arise from brain.

                                                                                             ii) Spinal nerves-arise from spinal cord

                                   (3) Autonomic Nervous system

Human Brain

Human brain has three major parts or regions

a) Forebrain b) Mid Brain c) Hind Brain

Forebrain

Most complex/specialized part of the brain is CEREBRUM

Functions

1. Thinking part of the brain

2. Control the voluntary actions.

3. Store information (Memory)

4.. Receives sensory impulses from various body parts and integrates it.

Cerebrum has 3 main areas.

a. Sensory area- to receive impulses from sense organs via Receptors

b. Motor area- control voluntary movements.

c. Association areas- Reasoning, learning & intelligence.

HYPOTHALAMUS :

   Connecting link between nervous system and Endocrine system.

   Controls body temperature.

   Centre assosciated with hunger.

PITUITARY GLAND : Secretes hormones. (Master Gland)

Mid Brain : Connects forebrain to hind brain.

Hind Brain :

CEREBELLUM

i) Controls posture and balance

ii) Control precision of voluntary actions

Walking in a straight line.

MEDULLA: Controls involuntary actions

eg. blood pressure, salivation, vomiting

PONS:  Involuntary action, regulation of respiration

PROTECTION OF BRAIN AND SPINAL CORD

˜ Brain : i) Brain is also enclosed by three membranes i.e. Meninges.

   ii) Cerebrospinal fluid is present in between the three meninges. It acts as shock absorber.

   iii) Brain is enclosed in cranium (Brain Box).

˜ Spinal Cord : Spinal Cord is enclosed in Vertebral column.

Coordination between Nervous and Muscular Tissue

Motor nerve  ← Brain/ Spinal cord← Sensory nerve←Receptors← Stimulus

         ↓

Nerve impulse → Muscle cell → Change in arrangement of proteins in muscles

                          (Effector organ)                                               ↓

Action caused ← Shorter form of muscles ← Change in shape of muscle