NERVOUS SYSTEM FOR BIOLOGY NDA 2022

The neural system is a control system, which coordinates with endocrine system to coordinate various body parts, thus maintaining physiology.
It gives ability to think and understand.
Nervous system receives and conducts stimuli to show a specific response against that stimuli. It mainly occurs with the help of neurons.
Neurons are structural and functional units of nervous system.
On the basis of function, neurons can be

Sensory (receptor/afferent), which connect sense organs with CNS,
Motor (effector/efferent), which connects CNS to effectors like muscles and glands,
Interneurons/connector/relaying/adjuster, which occurs in between sensory and motor neurons for distant transmission of impulses.

On the basis of number of nerve processes, there are four types of neurons namely unipolar neuron (only axon with no dendron, e.g. early embryo), bipolar neuron (1 dendrite and 1 axon, e.g. olfactory epithelium and retina), multipolar neuron (1 axon and multiple dendrites, e.g. brain and spinal cord) and pseudounipolar neuron (bipolar but appear as unipolar, e.g. dorsal root ganglion of spinal cord).
A synapse is a gap between two neurons.
Synapse helps in the transmission of nerve impulse from one neuron to another. The membranes of pre and postsynaptic neurons are separated by a synaptic cleft.
Human nervous system is divided into three parts, i.e. central nervous system, peripheral nervous system and autonomic nervous system.

1. Central Nervous System (CNS)

CNS is the part of nervous system that controls whole body and itself. The central nervous system is consists of brain and spinal cord.

(i) Brain

It is the anterior portion of the CNS, which is lodged in the cranial cavity, i.e. cranium of the skull. It weighs from 1220 to 1400 grams. Structurally, it consists of three membranes (meninges)

Piamater membrane innermost thin, very delicate, vascular and inverts the brain closely.
Arachnoid membrane outer to piamater thin, spider webby structure.
Duramater membrane outermost, tough fibrous membrane, adhering closely to the inside of the skull.

Brain have following parts

(a) Forebrain

It is the largest part of brain.
It occupies 2/3 portion of brain.
It is the main thinking part of brain.
It consists of two parts, i.e. cerebrum and diencephalon.
Cerebrum is the most developed part in human. It is divided into right and left cerebral hemispheres connected by corpus callosum.
Cerebrum consists of many fold having small grooves (sulci), large grooves (fissures) and bulges between two (gyri).
Diencephalon is consists of three parts, i.e. thalamus, hypothalamus and epithalamus.
Thalamus controls emotions and memory.
Hypothalamus control visceral activities. It helps to maintain homeostasis, control thirst, hunger, temperature, respiration, heartbeat.

(b) Midbrain

It is made of two parts, i.e. cerebral peduncle and corpora quadrigema. It lies between the hindbrain and forebrain.
If consists of group of fibres that arouses the forebrain when something unusual happens.
Midbrain is responsible for vision and heary.

It consists of the medulla, cerebellum and pons. The medulla is the swelling at the tip of the brain that serves as the passage way for nerves extending to and from the brain.
The pons is the swelling between the medulla and midbrain. The pons acts as a bridge between various portions of the brain.
Hind brain is responsible for muscular activities breathing, coughing, etc.

(ii) Spinal Cord

It extends from the base of the brain and is continuous to second lumbar vertebra. In adult, the spinal cord ranges from 42 to 45 cm in length.
It mainly lies in the neural canal of the vertebral column.
It is basically the posterior part of CNS, which runs mid-dorsally within the vertebral column. The three meninges, i.e. duramater, arachnoid and piamater, which covers the brain, also continue over the spinal cord.
The two indentations, i.e. posterior median sulcus and the anterior median tissues separates the spinal cord into left and right halves.
The inner area is the grey matter, while outside to it are white columns called the white matter.

Functions of Spinal Cord
(i) The stimuli passes from and to the brain through the spinal cord.
(ii) It also act as the centre of spinal reflex action.

2. Peripheral Nervous System (PNS)

The nerves that originate from central nervous system connect either with receptor or effector organs from peripheral neural system.
Nerves, which arises from brain are called cranial nerves while the nerves originating from the spinal cord are termed as spinal nerves.
It relays impulse from the CNS to skeletal muscles. In human body there are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

3. Autonomic Nervous System (ANS)

It transmit impulse from the CNS to the involuntary organs and smooth muscles of the body. This system was discovered by Langly in 1921.
It is further divided into two types

Sympathetic Nervous System Accelerates heartbeat, enlarge pupils, supply blood to muscles, contract nerves of urinary bladder, lowers the intestinal digestion activities, helps in blood clotting, increased secretion of sweat glands, make breathing easier and promote liver to release sugar and decrease bile production are some activities controlled by this nervous system.
Parasympathetic Nervous System Works just analogus to the sympathetic nervous system, i.e. slows down heartbeat, dilates arteries and lower blood pressure, speeds up peristalsis, stimulate salivary gland secretion, contracts gall bladder, promotes pancreas for secretion, decreases the secrection of sweat glands, etc.

Reflex Action

A reflex action is an automatic response to a stimulus.
The pathway taken by nerve impulses in a reflex action is called the reflex arc.
Reflex actions are under the control of spinal cord (CNS).
Reflex actions were discovered by Marshell Hall.
Some examples of reflex action are our foot away when we something sharp, moving hand away on touching a hot plate, a knee-jerk, movement of diaphragm during respiration, coughing, yawning, etc.

Reflex actions are of two types

Uncondition reflex action These are rapid actions that are not controlled by brain, e.g. tears, knee-jerk reflex, etc.

Conditioned Reflex Action These actions or activities are learnt by an individual by continuous practice and experience, e.g. dancing, cycling, swimming. These are under the control of cerebral.

NDA MATHEMATICS NOTES :

#COMPLEX NO.

#SET THEORY

#RELATION

#PERMUTATION AND COMBINATION

#PROBABILITY

QUESTIONS OF PROBABILITY

#VECTOR

#LOGARITHM

#BINARY NO.

#TRIGONOMETRY

#INVERSE TRIGONOMETRY FUNCTION