Human Nervous | SEE Biology Notes

Science SEE

Human Nervous | SEE Biology Notes


The external substance which can change morphology and physiology of organism is called Stimulus.

a) Light
b) Pressure/ Touch
c) Heat
d) Gravity
e) Water
f) Flow of wind
g) Chemical, etc.


Definition: The change seems in the organism is called Response/ Reaction.

a) When we touch leaves od mimosa pundica, all the leaves are collapsed for some time.
Touch: Stimulus
Collapse leaves: Reaction/ Response
b) Mole comes out from a hole in the night.
Night: Stimulus
Come out from the hole: Response/ Reaction
c) Ant goes towards sugar.
Sugar: Stimulus
Movement towards sugar: Response/ Reaction

Nervous System:

Definition: The system composed of nerves tissue to control and coordinate all part of the body is called the Nervous System.

It has three types:
a) Central Nervous system (CNS).
b) Autonomous Nervous system (ANS).
c) Peripheral Nervous system (PNS), etc.


Central Nervous system (CNS):

The major parts of CNS are:
a) Brain
b) Spinal cord, etc.


Definition: Brain is the main part of the central decision power, thinking, hearing, laughing, vision, and heartbeat movement of the body, etc. It controls the function of all part of the body.

Following are the main part of the brain:
a) Cerebrum
b) Cerebellum
c) Mid-brain
d) Pons
e) Medulla oblongata, etc.

Parts Comments
Cerebrum It covers 80% part of the brain and called forebrain or large brain. It is divided into two hemispheres by deep tissue.
a) Thinking
b) Responding
c) Memory
d) Intelligence
e) Mood
f) Taste
g) pain
h) Happiness
i) Love feeling, etc.
Cerebellum It is a small brain. It is a lemon-shaped semicircular structure present behind posterior end of the cerebrum.
a) It coordinates and controls voluntary body movement.
b) It maintains the balance and equilibrium of our body.
c) It maintains the muscles tone.
Mid-brain The main brain is a part of brain present between cerebellum and pons.
It acts as a relay station between cerebellum and pons.
Pons It is located between midbrain and medulla oblongata. It works as a relay station for impulses.
Medulla oblongata The spinal cord is started from here.
a) It is a center for breathing, heart, and blood pressure.
b) It controls coughing, sneezing, vomiting swallowing, etc.
c) It acts as a bridge between the brain and spinal cord.
d) It controls the secretion of enzymes, hormones, etc.

Spinal Cord:

Definition: The spinal cord is the nerve tissue dedicated for reflex action and it is an extension of the medulla oblongata.

Composition: It is composed of white-grey matter. It is originated from the medulla oblongata and passes through the neural canal of the vertebral column. It is a cylindrical structure gradually becoming thin. It is protected by the vertebral column.



a) It controls reflex action.
b) It is a transmission station between the brain and all the parts of the body, etc.

Some technical terms:

Meninges: It is an outer protective cover of the brain.
It has a three-layered structure.

Following are the layers:
a) Dura mater: Outer
b) Arachnoid: Middle
c) Pia mater: Inner connected with a brain, etc.

Cerebro Spinal fluid: It is a shock absorber fluid filled between arachnoid and perimeter.

Cranium: The bony box of the skull in which the brain is enclosed is called Cranium.

Cranial nerve: The nerve originated from the brain is called Cranial nerve.
It is a 12 pair in number.

Spinal nerve: The nerves originate from the spinal cord is called Spinal nerve.
It is 31 pair in number.


Definition: The neuron/ nerve cell is the unit of neurons system. It composes Neurons composes nerve tissue.

It has three main parts:
a) Cyton/ cell body.
b) Dendrites
c) Axon, etc.



a) Cyton is the central part of neuron it has large nucleus and cytoplasm.
b) Dendrites are highly branched structure of cyton which receive impulses (Wave of sense).
c) Axon is the tail like structure covered with medullary sheath the nacked part of axon where no medullary sheath is called Node of Ranvier.

Types of neurons:

a) Sensory neuron: Carries impulses from part of the body to the brain or spinal cord.
b) Motor neuron: It carries impulses from the brain/ Spinal cord to body.
c) Connective neuron: It connects sensory and motor neuron.

Reflex Action:

Definition: The immediate or involuntary action of the body in the response of stimulus is called Reflex-action.

  • Its center is spinal cord. It is controlled by the spinal cord, not the brain.
  • Very quick involuntary action, etc.
  • Example:
    a) Mouthwatering to see delicious food.
    b) Sneezing when external particle entered into a nose.
    c) With drawl of hand when touched to hot pan/ pots, etc.

Reflex arc:

Definition: The path through which reflex action is activated is called the reflex arc.


Glandular System:

Gland: The gland is the special type of structure responsible for secretion of juice (Enzymes and Hormones).

  • Largest gland: Liver
  • Smallest gland: Pituitary gland
  • Master gland: The pituitary gland is called master gland because it controls and coordinates all the glands of our body.
  • Emergency gland: Adrenal gland: At the time of accidents or injury, it controls pain, fair, pressure, etc.
  • Mixed/ heterocrine gland: Pancreas: It secretes enzymes and hormone both and it is a combination of exocrine and endocrine.

Types of glands:

  • Exocrine gland
  • Endocrine gland
  • Heterocrine gland, etc.

Exocrine and Endocrine gland:

a) Salivary gland
b) Gastric gland
c) Sweet gland
d) Lacrimal gland, etc.Example:
a) Pituitary gland
b) Adrenal gland
c) The thyroid gland, etc.

Exocrine Endocrine
The gland which secretion goes to target organ through the duct is called Exocrine or ductal gland. The gland which secretion goes to target organs without duct is called ductless or Endocrine gland.
The secretion of the exocrine gland is called Enzymes. The secretion of the endocrine gland is called hormones.
A large amount of enzymes is effective. The small amount of hormones is effective.
a) Salivary gland
b) Gastric gland
c) Sweet gland
d) Lacrimal gland, etc.
a) Pituitary gland
b) Adrenal gland
c) Thyroid gland, etc.

Pituitary gland:

  • It is located at the lower portion of the brain in cellaturica.
  • It is a pea-like structure and controls all the glands of our body. It is called Master gland also.
  • Hormones:
    a) GSH (Growth stimulation hormones).
    b) TSH (Thyroid stimulating hormones).
    – Deficiency: Dwarfism
    – Excess secretion: Gigantism

Thyroid gland:

  • It is located at both sides of traches.
  • Its major hormone is thyroxine which contains iodine (I2).
  • Its deficiency causes goiter.
  • It’s over secretion cause weight loss, etc.

Adrenal gland:

  • It is located at the anterior end of the kidney.
  • It has two parts: a) Advanal cortex, and b) Adrenal Medulla, etc.
  • Its secretion is called Adrenaline which controls blood pressure, etc.

Parathyroid gland:

  • It is located at just below the thyroid gland.
  • It secretes a hormone called Parathormone.
  • It controls the exchange of calcium between blood and bone, etc.


  • It is located at the loop of the duodenum.
  • It secretes two hormones insulin and glucagon.
  • Deficiency of it increases the sugar level in blood.
  • Deficiency of it decreases sugar level in blood.


  • It is located at the development of secondary sex characters.
  • Testes of male and ovaries of females are called gonads.
  • It produces sex hormones for both male and female.
  • For male: Testosterone and Androgen, etc.
  • For Female: Oestrogen and progesterone, etc.