Human nervous and glandular system

Stimulation: Any environmental change that brings about response in an organism is called stimulus.

Reaction: The response of an organism towards stimulus is called reaction.

Nervous system

It is of 3 types:

1. Central nervous system
2. Peripheral nervous System
3. Autonomic nervous system

Central nervous system: It consists of brain and spinal cord.

A) Brain:

1. It is situated inside cranial cavity called brain box.
2. It is covered with 3 protective membrane called meninges. They are Dura mater, Arachnoid mater and Pia mater.
3. In between Arachnoid and Pia mater there is special fluid called cerebrospinal fluid which protects brain from external shocks.
4. Average weight of brain is about 1.2 1a 1.4 kg.

Brain consists of 3 major parts. They are

1. Cerebellum
2. Cerebrum
3. Medulla oblongata

a. Cerebrum:

1. It occupies about 80% of total brain.
2. It is divided into left and right cerebral hemisphere.
3. Several convolutions are present in it which increases its surface area.

The major functions of this part are:

1. It is the centre of memory, creativity, intelligence, emotion etc.
2. It is the controlling centre of various senses like sense of hearing, sight, smell, taste, pain, pressure etc.
3. It controls and coordinates functions of all other parts of brain.

When the cerebrum doesn’t work due to any disturbance, the person enter into Coma condition (half-dead)

b. Cerebellum:

It is smaller in size and has two hemisphere.

Various functions of cerebellum are as follows:

1. It helps to maintain balance and posture of body
2. It controls voluntary activities of our body.
3. It helps to maintain muscle tone.

c. Medulla oblongata:

1. It is also hind brain.
2. It is cylindrical in shape.
3. Even minor injuries to this part can cause immediate death.

Various functions of it.

1. It controls activities vomiting, sneezing, coughing etc.
2. It controls vital activities like heart beat, blood circulation, respiration, excretion etc.

Spinal cord: It is the bundle of nervous tissue that originates from posterior end of Medulla oblongata and runs through the space within the vertebral column. It is cylindrical in shape.

Its major functions are:

1. It controls reflex action.
2. It gives rise to 31 pairs of spinal nerves which connect various part of body with brain.

Neurone: Neurone is a nerve cell with dendrites and axom.

It is unit of nervous system

There are 2 types of nerves. They are:

1. Sensory nerves
2. Motor nerves

Interneurons:  These are special type of neuron which convert sensory impulses into motor impulses.

Peripheral nervous system:

It consists of nerve fibres that originate from brain or spinal cord. On the basis of origin, there are two types of nerves. They are:

Cranial nerves: Nerves that originate directly from brain are called cranial nerves. There are 12 pairs of cranial nerves.

Spinal nerves: Nerves that originate from spinal cord are called spinal nerves. There are 31 pairs of spinal nerves.

Autonomic nervous system:

The nervous system which controls various activities of muscles and glands continuously even when we are sleeping is called autonomic nervous system. Its of 2 types:

1. Sympathetic autonomic nervous system.
2. Parasympathetic autonomic nervous system.

Sympathetic ANS: Nervous system that prepares the body to face emergency situation in different ways like by increasing breathing rate, heart beat, activities of digestive system, excretory System etc i called sympathetic ANS.

Parasympathetic ANS: Parasympathetic ANS normalizes the changed body condition after the emergency condition is over.

Ganglia: Ganglia are the cluster of nerve cells which are found in the grey matter of spinal cord They help to connect brain and spinal cord.

Glandular system

Click here to see all types of glands, their hormones secretion and functions.

Glands: Glands are the group of special type of tissues which are capable to secrete chemical fluid

In general, there are 2 types of glands

1. Endocrine gland
2. Exocrine gland

Hormone: Hormones are the chemical secretion of endocrine gland. Hormones are also called chemical messenger of body, It is because they are chemical substances which can influence the activities of body cells.

Various endocrine glands, hormones secreted by them and their functions are given

Solved exercise

a. What is reflex action?

It is rapid automatic response of body towards the stimulus which is conducted by spinal cord.

b. Which part of brain is responsible for the Involuntary action of our body? Name any 2 such actions.

Medulla oblongata performs involuntary actions. Eg respiration, blood circulation

c. Which endocrine gland is responsible for physical and mental development of body?

Thyroid gland is responsible for physical and mental development

d. Which hormone is produced during excess excitement?

Adrenaline hormone is produced during excess excitement.

e. What is goitre?

When there is deficiency of iodine, thyroid gland can’t produce thyroxin and it enlarges in size which forms a ball of flesh in the neck, this is called goitre.

f. Why in the pituitary gland also called master gland?

Since hormones secreted by this gland controls activities of other gland, it is also called master gland.

g. Why is pancreas gland as called mixed (heterocrine) gland?

Pancreas like exocrine gland secretes enzymes. Similarly, like endocrine gland secretes hormones is also called heterocrine gland.

h. Write 4 effects of under-secretion of insulin.

They are

1. Diabetes
2. Excess hunger
3. Frequent urination
4. Delay in wound healing

i. Adrenal gland is called emergency gland why?

Hormones secreted by adrenal gland help to prepare our body to face emergency situation, so this gland is also called emergency gland.

j. Write 2 differences between spinal cord and medulla oblongata.

k. Enzymes are called biological catalyst.

Enzymes are secreted only by the body of living organisms and they activate various chemical processes in the body so they’re called biological catalyst.

l. A person injured on backbone may get paralyzed.

When there is injury in backbone, it may damage spinal cord. When spinal cord is damaged at any point, the part below that point can’t communicate with brain. As a result it cause paralysis.

m. Outer surface of spinal cord is white.

Outer surface of spinal cord is made up of white matter of neurons so, it appears white.

Q1) Study diagram and answer

i. Which part has white outer surface?

Part ‘e’ has white outer surface i.e. spinal cord.

ii. Which is responsible for posture of body?

Part ‘f’ i.e. cerebellum.

iii. Name a, d and f.

a: Cerebrum

d: Medulla oblongata

f: cerebellum

iv. Which of them is responsible for reflex action?

Part ‘e’ i.e. spinal cord.

Q2) Study diagram and answer

i. Write names of a, b, e and f.

a: Pituitary gland

b: Thyroid gland

e: Ovary

f: Testes

ii. Identify secretion of c, d, e.

c: Insulin, glucagon

d: Adrenaline

e: Progesterone, oestrogen

iii. Write the function of secretion of ‘c’?

It controls level of glucose in blood

iv. Which one of them is called emergency gland and why?

Gland ‘d’ i.e. adrenal gland is called emergency gland because Hormones secreted by this gland prepare our body to face emergency situation.