Download Introduction to the Nervous System

Introduction to the Nervous System
1- Both the nervous system and the endocrine system share the responsibilities for
maintaining the normal homeostasis of the body. Both systems detect changes in
the physiologic set point of the body (temp., BP) they integrate the information
they are receiving, and respond by making changes to return the body to its set
point. The nervous system uses a three step approach to generate sensory and
motor output
a- Sensory input (neuron)
b- Interneuron control
c- Motor output (neuron)
2- ALL behavior is controlled by the nervous system
3- The nervous system is one of the smallest but most complex of the 11 organ
systems. The nervous system (brain and nerve) has a total mass of about 2 kg or
about 3% of body weight. The nervous system is divided into two sections
a-
bc-
4- The structure of the nervous system
a- The structures that make up the nervous system include the brain, spinal
cord, nerves, ganglia, enteric plexus and sensory receptors
b- The peripheral nerves exist outside the CNS and are classified according
to their origin, each follows a well defined path and services a specific part
of the body
1- Cranial nerves –
a- There are 12 pairs of cranial nerves (I – XII)
b- Olfactory, Optic, Oculomotor, Trochlear, Trigeminal,
Abducens, Facial, Vestibulocochlear, Glossopharyngeal,
Vagus, Accessory, Hypoglossal
c- Pneumonic contest
2- Spinal nerves –
a- There are 31 pairs of spinal nerves. They are named and
numbered according to the level of the spinal cord from which
they emerge
b- C1-C8, T1-T12, L1-L5, S1-S5, Co1
c- C1 exits between the atlas vertebrae and the occipital bone of
the skull, all others exit directly from the vertebral column
3- Ganglia –
4- Enteric Plexus –
5- Sensory Receptors –
5-Organization of the nervous system
1- Most nerve impulses that stimulate muscles to contract and glands to
secrete originate in the CNS
2- The target of these impulses is usually in the PNS
3- The PNS is further subdivided into the somatic nervous system (SNS)
and the autonomic nervous system (ANS)
4- The SNS contain the sensory neurons and receptors for the special
senses (vision, hearing, taste and smell), which transmit to the CNS.
The SNS also includes the motor neurons to the skeletal muscle. This
part of the PNS is voluntary
5- The ANS consists of
a- Sensory neurons that convey information to the CNS from
sense receptors
b- Motor neurons that conduct impulses to smooth muscle,
cardiac muscle and glands
c- For this reason the ANS is generally considered involuntary.
d- The ANS is divided into three sections
i. Sympathetic nervous system, parasympathetic and
enteric systems
6- Diagram – Subdivisions of the PNS
7- Parts of a Neuron
a- Nissl Bodies -
b- Synaptic end bulb -
c- Schwann cells -
d- Nodes of Ranvier –
8- Gray and White Matter
a- White matter –
b- Gray matter –
c- Diagrams -