Control and co-ordination

Control and Co-ordination

Notes By:- Nagraj Sir

• All the living organisms respond and react to changes in the environment around them.
• The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch etc.
• Both plants and animals respond to stimuli but in a different manner. 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 

 The nervous system in humans can be divided into three main parts

1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord. The brain controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain and the peripheral nervous system.

2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region.

3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system can be divided into two parts :

• Sympathetic nervous system.
• Parasympathetic nervous system.

Sympathetic Nervous System: This part of the autonomous nervous system heightens the activity of an organ as per the need. For example, during running, there is an increased demand for oxygen by the body. This is fulfilled by an increased breathing rate and increased heart rate. The sympathetic nervous system works to increase the breathing rate the heart rate, in this case.

Parasympathetic Nervous System: This part of the autonomous nervous system slows the down the activity of an organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in the conservation of energy.

Receptors:

Are specialized tips of some nerve cells that detect the information from the environment. These receptors are located in our sense organs.
(a) Ear : • Phonoreceptors
• Hearing
• Balance of the body
(b) Eyes • Photoreceptors
• Seeing
(c) Skin : • Thermoreceptors
• Heat or cold
• Touch
(d) Nose : • Olfactory receptors
• Smell detection
(e) Tongue : • Gustatory receptors
• Taste detection

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

Types of neuron

• Sensory neuron: These neurons receive signals from a sense organ.
• Motor neuron: These neurons send signals to a muscle or a gland.
•  Relay neuron: These neurons relay the signals between sensory neuron and motor neuron.

Parts of Neuron :

(a) Dendrite : Acquires information.
(b) Cell body : Acquired information travels as an electrical impulse.
(c) Axon : Longest fibre on the cell body is called axon. It transmits electrical impulse from cell body to dendrite of next neuron.

Synapse :It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here electrical signal is converted into chemical signal for onward transmission.

REFLEX ACTION

Reflex action is quick, sudden and immediate response of the body to a stimulus. E.g., Knee jerk, withdrawal of hand on touching hot object.

Response : Responses are of three main types :
(a) Voluntary : Controlled by fore brain. E.g., talking, writing.
(b) Involuntary : Controlled by mid and hind brain. E.g., heart beat, vomiting, respiration.

(c) Reflex action : Controlled by spinal cord. E.g., withdrawal of hand on touching a hot object.

HUMAN BRAIN

Brain is the main coordinating centre of the body. It has three major parts :
(a) Fore-brain             (b) Mid-brain            (c) Hind-brain

Cerebrum: The cerebrum is the largest part in the human brains. It is divided into two hemispheres called cerebral hemispheres.

Functions of cerebrum

• The cerebrum controls voluntary motor actions.
• It is the site of sensory perceptions, like tactile and auditory perceptions.
• It is the seat of learning and memory.

Hypothalamus: The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle of the body. It also controls the urges for eating and drinking.

Cerebellum: Cerebellum lies below the cerebrum and at the back of the whole structure. It coordinates the motor functions. 

• It controls posture and balance.
• It controls the precision of voluntary action.

Medulla: Medulla forms the brain stem, along with the pons. It lies at the base of the brain and continues into the spinal cord. The medulla controls various involuntary functions, like hear beat respiration, etc.
It controls involuntary actions.
Example: Blood pressure, salivation, vomiting.

Pons: It relays impulses between the lower cerebellum and spinal cord, and higher parts of the brain like the cerebrum and midbrain, also regulates respiration.

Spinal cord: Spinal cord controls the reflex actions and conducts massages between different parts of the body and brain.

Protection of Brain and Spinal Cord

(a) Brain : Brain is protected by a fluid (Cerebo-Spinal Fluid) filled balloon which acts as shock absorber and is enclosed in cranium (skull or brain box).

(b) Spinal Cord : Spinal cord is enclosed in vertebral column.

                          COORDINATION IN PLANTS

Movements in plants :
(i) Independent of growth
(ii) Dependent on growth

(i) Independent of growth : Immediate response to stimulus.
• Plants use electrical-chemical means to convey information from cell to cell.
• For movement to happen, cells change their shape by changing the amount of water in them, resulting in swelling or shrinking of cells. E.g., Drooping of leaves of ‘Touch-me-not’ plant on touching it.

(ii) Dependent on growth : These movements are tropic movements i.e., directional movements in response to stimulus.
• Phototropism : Movement towards light.
• Geotropism : Movement towards/away from gravity.
• Chemotropism : Growth of pollen tube towards ovule.
• Hydrotropism : Movement towards water.

Plant Hormones : Are chemical compounds which help to coordinate growth, development and responses to the environment.

Main plant hormones are :

(a) Auxin : • Synthesized at shoot tip
                    • Helps the cells to grow longer
                    • Involved in phototropism
(b) Gibberellin : • Helps in the cell elongation & growth of the stem

(c) Cytokinins : • Promotes cell division
                            • Present in greater concentration in fruits and seeds
(d) Abscisic Acid : • Inhibits growth
                                • Cause wilting of leaves
                                   • Stress hormone

Hormones in Animals :

Endocrine System: The endocrine system is composed of several endocrine glands. A ductless gland is called endocrine gland. Endocrine gland secretes its product directly into the bloodstream. Hormones are produced in the endocrine glands. Nervous do not react to every nook and corner of the body and hence hormones are needed to affect control and coordination in those parts

Hormones : Hormones are the chemical substances which coordinate the activities of living organisms and also their growth.