The S*"
Grey's biology
5
The nervous system
Second
Peripheral nervous system ?? ?? Nelwork
o it connects the central nervous system with all the body parts
o It consists of a network of nerves that are distributed all over the different body parts & includes:
(1). Cranial nerves
o Number: 12 pairs connected to the brain
o Types: sensory, motor or mixed nerves
Mixed nerves
They are nerves that transmit the nerve impulses from the receptor organs to the brain and transmit the stimulating orders from the brain to the effector organs "They are sensory and motor nerves together"
(2).Ans
EXI
or n are
SyS
Re
R
system
The reflex arc consists of
In most cases
Sense organ
Sensory neuron
connector neuron
Motor neuron
Efferent
Responding organ
Effector
Receptor
Afferent
Intermediate
It is the organ that responds to the changes that happened in the enviroment, such as muscles and glands.For Your Information
o The vertebrae of the vertebral column
33 vertebrae) are arranged from
up to down into five regions, which are:
- Cervical vertebrae
- Thoracic vertebrae (12)
- Lumbar vertebrae
5
- Sacral vertebrae (5)
- Coccygeal vertebrae (4)
-> So, the number of nerves pairs is different from the number of vertebrae in cervical & coccygeal regions
??y?Spinal nerve
Grey's biology
5
The nervous system
o Types: mixed (sensory and motor nerves together)
o Spinal nerves roots: each spinal nerve has two roots (dorsal and ventral.):
P.O.C.

Ventral root
Dorsal root
It contains motor nerve fibers.stimulating motor orders (nerve impulses) that come from the brain and spinal cord to the responding (effector) organs, such as muscles and glands.Sensory neuron
Connector neuron
Sensory fiber
Dorsal root
Grey
mamter
Skin surface of thumb (Sensory receptors)
(2)
(1)
(4)
Motor fiber
Ventral
o the
????b. Involuntary (autonomic) reflex arc
The response is in the involuntary muscles (like cardiac muscle) or glands.Reflex actions are of two types:
a. Voluntary (somatic) reflex arc
The response is in the voluntary (skeletal) muscles.Spinal nerves
o Number: 31 pairs are connected to the spinal cord and exist in successive pairs on both sides of spinal cord and these pairs are arranged, as follows:

Nerve
Number

Cervical
8 pairs that are connected with the neck.It transmits messages or
Function
It transmits messages (nerve impulses) from the receptor organs to the spinal cord and from it to the brain.Thoracic
12 pairs that are connected with the chest (thorax
4
Lumbar
5 pairs that are connected with the lumbar ????vertebrae

Sarcal
5 pairs that are connected with the sacral ?????Structure
It contains sensory nerve fibers.coccygeal
1 pair that is connected with coccyx.vertebrae.???????3?(0).?