Download Nervous System - Phoenix Union High School District

Nervous System
controls the body and is the
communicating system of the
body
General Schematic of Nervous System
Major functions of the nervous system
1. Sensory input – receives stimuli
occurring inside and outside the
body
2. Integration – interprets sensory input
3. Motor output – responds to stimuli
by activating effector organs
Organization
What are the three major anatomical
parts of the nervous system?
• brain
• spinal cord
• nerves
A) Central nervous system (CNS)
– brain and spinal cord
– serves as integration and command center
B) Peripheral nervous system (PNS)
– cranial and spinal nerves
– carries messages to and from the body to
the spinal cord & brain
Divisions of the PNS
I. Sensory (afferent) division
A) Somatic sensory afferent fibers – carry
impulses from skin, skeletal muscles, and
joints to the brain
B) Visceral afferent fibers – transmit
impulses from visceral organs to the brain
II. Motor (efferent) division
–transmits impulses from the CNS
to effector organs
A) Somatic nervous system
– Conscious control of skeletal muscles
B) Autonomic nervous system (ANS)
e.g. Regulate smooth muscle, cardiac
muscle, and glands
(1) Parasympathetic division- “resting
and digesting system”
e.g. nonstressful situations
•Keeps energy use low and
maintains vital activities running
(2) Sympathetic division- “fight or
flight” division
e.g.
exercise
excitement
emergency
embarrassment
•Prepares the body for action
I. Cells of the Nervous System
A) Neuroglia (glial cells) are helper cells
that support neurons
1. Neuroglia of the CNS
a) astrocytes - star shaped cells that
connect neurons together and to their
blood supply.
b) microglia- function as phagocytes by
engulfing foreign invaders.
c) ependymal- (epithelial-like) provide a
barrier between brain and cerebrospinal
fluid.
d) oligodendrocytes- branched; connect thick
nerve fibers; produce a myelin sheath
around neurons.
2. Neuroglia of the PNS
a) Schwann cells = produce myelin sheath
B) Neurons = are the functional
cells of nervous system that actually
transmit messages
 Conduct
messages in the form of nerve
impulses
 They number in the billions
 Have
extreme longevity
 Most cannot divide (except in
hippocampus which is involved in
memory)
 Have a high metabolic rate; high
O2 and glucose requirement
Flashback!
What are the 3 regions of a neuron?

3 regions: dendrites, cell body, and axon
 Impulses travel from dendrites to cell body
to axons
What’s the difference between these
3 types of neurons?
II. Classification of neurons
A) Structural classification
1. Multipolar (most common)
2. Bipolar (rare)
3. Unipolar (PNS)
B) Functional Classification
B) Functional Classification
1. Sensory neurons


PNS
mostly unipolar; some bipolar
2. Interneurons
 CNS
 multipolar
3. Motor neurons
 PNS
 multipolar