Question

Animals-Nervous System

Answer 1

Animals must be able to sense and respond to the environment in which they live if they are to survive. They need to be able to sense the temperature of their surroundings, for example, so they can avoid the hot sun. They must also be able to identify food and escape predators.The various systems and organs in the body must also be linked so they work together.
Nervous System
The nervous system is composed of specialized tissues; called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control and coordination in complex animals.
Neuron: Neuron is a highly specialized cell which is responsible for transmission of nerve impulses. The neuron consists of the following parts:


Cyton or cell body: The cell body or cyton is somewhat star-shaped; with many hair-like structures protruding out of the margin. These hair-like structures are called dendrites. Dendrites receive the nerve impulses.
Axon: This is the tail of the neuron. It ends in several hair-like structures; called axon terminals. The axon terminals relay nerve impulses.
Myelin Sheath: There is an insulator cover around the axon. This is called myelin sheath. The myelin sheath insulates the axon against nerve impulses from the surroundings.
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.
Association neuron: These neurons relay the signals between sensory neuron and motor neuron.
Nervous System in Humans
The nervous system in humans can be divided into two main parts, viz. the central nervous system and the peripheral nervous system. The peripheral nervous system can be further divided into the somatic nervous system and the autonomous nervous system.
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.

Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves come out of the brain and go to the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region.

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:

(a) 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 and the heart rate; in this case.
(b) 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 conservation of energy.