Structure of nerves
There are 2 types of nerves. The cranial nerves and the spinal nerves. These branch out into neurons. The neurons are of 3 types. Sensory neurons which send nerve impulses to the brain from sensory organs, Motor neurons which send nerve impulses to the muscles which make certain actions, and the relay neuron which are found in the central nervous system.
There are two types of nervous system. One is the Central nervous System and the other is the peripheral nervous system. The central nervous system includes the spinal cord and the brain while the peripheral nervous system includes the spinal nerves and the cranial nerves.
How the neurons send impulses to central nervous system?
When you touch a hot pan, your temperature receptors, present in your skin, would feel the rise in temperature and send nerve impulses (which is electric impulse) to the spinal cord though the neurons.
Neurons are further divided into axons and dendrones and little branches called dendrites. The axon neuron sends impulses away from a cell body while the dendrone sends impulses to the cell. The neuron which sends the impulse to the central nervous system is a dendrone. In its way it passes through a cell. Then it is called an axon. Then when it enters the central nervous system, the axon relays impulses chemically to the relay neurons through a synapse.
The neuron then further relays the impulse to the brain which then gives commands to the neuron. The neuron then relays the command through a different set of relay neuron, axon and dendron and then it is sent over to a specific muscle which in this case would be the hand. The person would remove his hand immediately.
There are two types of actions. There are voluntary actions which are done by will and there reflex action which is done by the body itself.
Structure of the Brain
Brain is divided into two parts. The forebrain, hindbrain and the midbrain. The fore brain contains the cerebrum and the hypothalamus. The cerebrum has two cerebral hemispheres which have “wits” or “wrinkles”. This part controls the intelligence of man and animals. The ability to learn and the IQ of a man is dependent on its size and development. The hypothalamus is found in the floor of the fore brain which is in charge of controlling temperature of the body. The gland found below the hypothalamus is call the pituitary gland which secretes anti-diuretic hormone (ADH).
The mid-brain is concerned with visual strength of a man. It lies behind the optic lobes. The Hind brain consists of the cerebellum and the medulla oblaganta. The cerebellum has many lobes on its structure. It is concerned with body balance and muscular concerns. The medulla oblaganta moves down to form the spinal cord. It plays a role in controlling heartbeat, peristalsis and many more reflex actions. The brains outer color is white while its inner structure is grey. The grey part contains cell bodies of the neuron while the white part is just nerve fibers.
Structure of Spinal Cord
Spinal cord is a part of the central nervous system. Its outer structure is white while the inner structure is grey with a central tube inside the grey structure containing cerebrospinal fluid.
Two spinal nerves branch out of the spinal cord. One contains receptor neuron while the other a motor neuron. The spinal nerves then join together at a point creating a mixed nerve which then separates again. The dorsal root of the spinal nerve at the beginning is called the dorsal root ganglion because it has a cell body in it. The spinal cord has relay neurons in it which provide impulses to the brain and then back to the muscle.