Download Physiolgy of the nervous system

Physiology of the nervous system
Structural classification
The nervous system can be divided into:
1) Central nervous system (CNS), which includes, brain and spinal
cord.
2) Peripheral nervous system (PNS), which includes, cerebral nerves
(12 pairs) and spinal nerves (31 pairs).
Functional classification
This classification is concerned only with PNS or peripheral nervous
system, which subdivided into:
1) Somatic (voluntary) nervous system, which controls the skeletal
muscle
2) Autonomic (involuntary) nervous system, which controls smooth
muscle
- Central nervous system (CNS) is made up of 2 types of cells,
1) neuron (nerve cells) : dendrites, cell body and Axon
it has 3 shapes, unipolar neuron, bipolar neuron and multipolar
neuron.
2) supporting cells (Neuroglia)
1.
Astrocyte
- It has a swollen ends embracing neurons for protection.
- It acts as a barrier between neurons and blood capillaries
to prevent harmful substances to reach neurons.
2.
Microglial cell
- It phagocytes the debris like bacteria and dead cells.
3.
Ependymal cell
- It lines the cavities of skull and vertebral column to
protect the brain and spinal cord.
- It possesses cilia which circulate the cerebrospinal fluid
which acts as a cushion fluid.
4.
Oligodendrocyte
- It wraps the nerve fibers to insulate.
Reflex Arc
- It consists of 5 elements: receptors – sensory (afferent) neurons –
association neuron (integration center) – motor (efferent) neuron –
effectors (muscle or gland).
- Receptors receives sensation from sense organs, skin, eye, ear, taste
buds in mouth, nose.
- Sensory neuron carries the nerve impulses to CNS.
- Association neuron integrates the coming nerve impulses to motor
neuron.
- Motor neuron carries the reaction as a nerve impulse to effectors.
- ُEffector executes the reaction via muscle contraction or relaxation and
gland secretion.
What is the main functions of Neuron ?
- Neuron has 2 main functions.
1. Irritability, ability to respond to stimulus (form of nerve impulses)
2. Conductivity, ability to transmit (propagation of nerve impulses),
electrochemical transmission
How the nerve impulse be made up?
- Nerve impulse is made up by the conversion the nerve state from
polarization (resting) state to depolarization (action) state.
- neuron starts to increase the positivity inside by entering Na + ions
inside.
How the nerve impulse be propagated?
Electrical transmission
- Propagation of nerve impulse is executed by repeating the
conversion from polarization to depolarization in the next site of
nerve.
- the previous site is returned to the resting state (polarization).
- Conductivity or transmission is exerted electrically alongside
neuron and chemically when nerve impulse transmit from neuron to
another one.
Chemical transmission (Synapsis)
- Synapsis consists of 3 elements: presynaptic neuron – synaptic
cleft – postsynaptic neuron
- presynaptic neuron form neurotransmitter in vesicles.
- vesicles fuse with cell membrane
then open to release
neurotransmitter in synaptic cleft.
- neurotransmitter reacts with receptor on the cell membrane of
postsynaptic neuron, which starts to form new nerve impulse.