Download The Nervous System

Chapter 31 Notes
The Nervous System
The Nervous System:
• is a rapid
communication system
using electrical signals.
• enables movement,
perception, thought,
emotion and learning.
• consists of a network of
specialized cells called
neurons.
Neuron structure:
• Cell Body: central part of neuron, maintains
cell function, relays signals from one part of
cell to another.
• Dendrites: extend from cell body, receive
information from other cells.
• Axon: long extension from the cell body,
transmits signals to other neurons, ends in
an axon terminal. Many axons are insulated
with myelin which improves the efficiency of
signal transmission.
• Synapse: where the axon terminal connects
with another neuron, separated by a gap
called the synaptic cleft.
Axon
terminal
axon
Cell body
dendrites
•Nerve= A bundle of several neurons and
supporting cells.
• Neuron function:
• Neurons transmit signals down axons by
altering the flow of sodium and potassium
ions across their membranes in response to
chemical signals. The resulting imbalance of
electrical charges inside vs. outside the
axon creates an electrical voltage potential
(an “action potential”) that is propagated
down the length of the axon.
• When an electrical
impulse reaches the
axon terminal, it
stimulates the release of
neurotransmitters from
the “pre-synaptic”
neuron into the synaptic
cleft. These chemical
messengers bind
receptors on the surface
of the “post-synaptic”
neuron and either
stimulate or inhibit an
action potential in it.
• Most psychoactive drugs function by
mimicking or interfering with the
function of neurotransmitters and/or
their receptors.
Structure of the Nervous System
• Divided into two parts:
• Central Nervous System (CNS):
– Interprets and responds to information
– Consists of the Brain & Spinal Cord
Optical Illusions Website
• Peripheral Nervous System (PNS), which
contains:
– Sensory neurons that send info (sight, smell,
touch, sound, taste, pain) to the CNS.
– Motor neurons that send commands from CNS to
muscles and other organs.
Divided into:
• Somatic nervous system: controls skeletal muscles that
are under conscious control
• Autonomic nervous system: controls smooth muscles
that are not under conscious control (i.e. the heart,
diaphragm, digestive system)
• Parts of the Brain:
• Cerebrum (green)
– Largest part of the brain,
divided into two hemispheres.
– Handles learning, memory,
perception and intellectual
functions.
– Left hemisphere processes
sensations from and controls
movement on the right side of
the body, the right hemisphere
does the same for the left side
of the body.
• Cerebellum (blue)
– Regulates balance,
posture and movement;
• coordinates the moving
of several muscles
together (i.e. for
walking)
• Brain Stem: a collection of
several structures at the
base of the brain. (yellow)
– Midbrain, pons and medulla
oblongata: relays information
and regulates homeostasis
and vital body functions.
– Thalamus: central relay center
for all sensory information
traveling from the body to the
brain.
– Hypothalamus: regulates
homeostasis and the
endocrine system.