control n co
The response which a living being makes in relation to external stimuli is called control and coordination.
It is Nervous System which is mainly responsible for control and coordination in complex animals.
Nervous System
Nervous system is mainly composed of brain, spinal cord and nerves. Though five sense organs (nose, eyes, ears, tongue and skin) are also a part of nervous system and play a very important role in nervous system.
Functions of Nervous System
• Receive the information from environment by sense organs.
• Transportation of information to brain through spinal cord and nerves.
• After analyzing the information, It reacts accordingly through muscles and glands.
For example when we touch a hot object, our skin helps us to sense the heat, the nerves carry the Impulse to the brain through spinal cord, and then the brain sends impulse to the muscles to contract and take off the hands.
Receptors Receptors are group of cells present in sense organs which are sensitive to change in environment
There are five types of receptors which are responsible for sensing the change in
environment.
i. Gustatory Receptors; Responsible for taste detection.
ii. Phono Receptors: Responsible for heanng.
iii. Olfactory Receptors: Responsible for smell detection.
iv. Photo Receptors: Responsible for detecting hght
v. Thermo Receptors; Responsible for feeling the touch of external stimuli.
Gustatory Phono
Neuron Neurons are specialized cells which are combined to form nerves of the nervous
system. As nerves are emerged from brain and spinal cord and branch out to almost all
paris of the body, so neuron is also called unit of nervous system
The neuron consists of the following parts:
Cell Body: This main part has all of the necessary components of the cell, such as
the nucleus, endoplasmic reticulum. nbosome and mitochondr3a. If the cell body dies.
the neuron dies.
in several hair-like structures; called axon terminals! axon endings. The axon terminals
relay nerve impulses.
Dendrites: These small branch-like projections of the cell make connections to other
neuron and receive the nerve impulses
Synapse: The point of contact between the terminal branches of axon of one
neuron with the dendrite of another neuron is called synapse
Working of Neuron: Neurons are responsible for transrmtling message from brain to body parts arid vice versa.When receptors sense anything, a chenical reaction is triggered. This chenical reaction causes an electrical Impulse In dendrites. This impulse travels through the body of neuron to axon endings. Tiny amount of chemical is released in synapse by axon endings when impulse reaches there. This chemical crosses the synapse and reach to tip of dendrites where it again produces electrical impulse. And then this impulse travels along neuron.
Types of Neuron: a. Sensory Neurons: These neurons transmit message from body parts to central
nervous system (which is composed of the brain and the spinal cord),
b. Motor Neurons: These neurons transmit message from central nervous system
to body parts.
c. Relay Neurons: These neurons relay the signals within the central nervous
system. Nervous System in Humans The nervous system In humans can be divided into two main parts.
1. Peripheral nervous system 2. Central nervous system
Peripheral Nervous System (PNS): The peripheral nervous system is composed of the Cranial nerves. Spinal nerves and
Visceral nerves. Cririia.I Nerves: There are 12 pairs of cranial nerves. The cranial nerves come out of
the brain and go to the sense organs and muscles in the head region.
Spinal Nerves There are 31 pairs of spinal nerves. The spinal nerves come out of the
spinal cord and go to the sense organs and muscles which are below the head region.
These nerves carry message to brain through spinal cord.
Visceral Nerves: The visceral nerves come out of the brain and spinal cord and go to
the Internal organs (like heart, kidney etc.)
Voluntary and Involuntary Actions Voluntary actions are actions which we do in conscious control of brain. FOr example:
Writing, speaking, walking, kicking a ball, lifting an object etc.
Involuntary actions are those which occur without the conscious control of organisms or we can say they are not under the control of will. For example: beating of heart, breathing, sweating, working of kidney, digestion of food.
Reflex Action and Arc Reflex action: It is a quick, automatic response to the change in environment (stimulus) that involves only spinal Cord. Reflex actions occur within fractions of seconds. Reflex arc: It is the pathway through which reflex action occurs.
Types of Reflexes I Reflex actions
Cerebral Reflex: A cerebral I cranial reflex is one that is controlled by one of the cranial nerves and tends to take place in the facial or head area. For ex.
Change in size of pupil in bright light etc.
2. Spinal Reflex: A spinal reflex is a reflex that involves only the spinal nerves and spinal cord and is not processed by the brain. For ex. take off the hand on
touching a hot objeci
How Muscles (Effectors) cause Movement?
Muscles are made up of muscle cells which have special proteins. These proteins can change their arrangement on receiving message from brain. When they do so, shape of muscle changes. They can contract or expand. This contraction and expansion can cause movement in body parts. Central Nervous System (CNS):
The central nervous system Is conosed of the brain and the spinal cord.
Brain
Brain controls all the functions in the human body. It is surrounded by a skulII cranium. Cerebrospinal fluid is filled between the skull and the brain. Cranium and cerebrospinal fluid protect the brain from external shocks.
Human brain has three parts –
a. Forebrain (Cerebrum)- It is the most complex part of brain.
b. Mid brain is 1. Thinking part of the brain.
2. Memory (Store information).
3. Sensation.
4. Movement.
5. Feelings.
Thus cerebrum controls all the voluntary actions. Different parts of cerebrum are responsible for different jobs.
b. Mid brain: It controls cerebral reflexes like change in size of pupil, blinking of eye.
c. Hind brain: It controls all involuntary actions (beating of heart, breathing, sweating elc). Hind brain is mainly composed of three parts –
1. Pons -Regulate respiratory system.
2. Cerebellum – Controls posture, balance, motion, picking an object.
3. Medulla – Controls Involuntary actions ex. digestion, heartbeat, blood pressure, vomiting, saliva in mouth, swallowing.
Spinal Cord Spinal cord is started at medulla (Hind brain) and extends to downward. It is endosed by a bony structure called Vertebral column at back centre of body. Function – • It carries message between brain and nerves. • It controls spinal reflexes.
Endocrine System The endocrine system is composed of several endocrine glands.
What are Glands? Glands are organs in our body which excrete a liquid substance having some different chemicals. This liquid is called secretion of the gland.
Glands are of two types –
a. Exocrine Glands
ClancIs that have ducts are called exocane glands. The secretions of exocrine glands reach thesr target by traveling through a duct (tube), Some examples of exocnne glands are sweat glands and salivary glands.
b. Endocrine Glands
The endocrine glands do not have ducts to cany their product to a surface. They are called ductless glands
Hormones are the chemical substances produced by endocrine glands. These glands secrete their hormones directly into the blood vessels Blood carries the secretion to different parts.
Thus Endocrine System is the system of endocrine glands in our body which secretes chemical substances called Hormones’ This system controls various activities of our body br example growth of body.
Feedback Mechanism
Feedback mechanism takes care that right amount of hormones are secreted by glands.
Difference bw Nervous System
1. Messages are In form of Impulses over nerves.
2. Messages travel fast.
3. Messages have short term effect.
Need for Endocrine System
Endocrine System
Messages are In form of chemicals
through blood.
Messages travel slow.
Messages have long term effect.
• Nervous system is not very efficient in controlling large number of organs at the same time for a particular job. In such situations endocrine system is better.
• Nervous system is not meant for sending continuous messages ftr long time penods. But endocrine system can easily send continuous chemical messages in slow and steady manner. So endocrine system is better for controlling slow processes such as body growth.