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UNIT 4
• Nervous System:
(1) CNS (central nervous system): brain
and spinal cord
(2) PNS (peripheral nervous system):
nerves
• Neurons: stings of long, thin cells which
send messages to and from the brain along
nerves
~neurons “fire” when they are
stimulated
~work on all or none theory: they either
fire at full strength or don’t fire at all
PARTS OF A NEURON
• 1. Cell body: has nucleus and produces
energy needed to fuel neuron activity
• 2. Dendrites: short, thin fibers that stick
out from cell body; receive messages from
other neurons and send them to cell body
• 3. Axon: long fiber that carries impulses
away from cell body toward the dendrite of
another neuron
NEURON
• Myelin sheath: a white, fatty substance that
insulates and protects the axon
• synapse: the space between neurons;
connects to other neurons
• A neuron transmits its impulses (messages)
to another neuron across the synapse by
releasing chemicals called
neurotransmitters which open chemical
locks to excite the other receptors
• Somatic Nervous System (SNS): the part of
the PNS that controls voluntary activities
• Autonomic Nervous System(ANS): part of
the PNS that controls involuntary activities
like heartbeat, stomach activity, etc.
2 parts of the ANS
• These are all automatic, don’t think about
(1) sympathetic nervous system: prepares
body for emergencies or hard activity
(2) parasympathetic nervous system: saves
energy and helps body to recover after hard
activity; brings body back to normal resting
state
3 Parts of Brain
1. Hindbrain: at the rear base of the skull
(a) cerebellum: controls posture and
balance
(b) medulla: controls breathing and
reflexes
(c) pons: bridge between spinal cord
and brain
2. Midbrain: small part of brain; integrates
sensory information
3. Forebrain: covering of brain’s central
core; “higher” thinking processes
(a) thalamus: relay station for all
information that travels to and from cortex
(b) hypothalamus: controls hunger, thirst,
sexual behavior, body’s temperature
(c) cerebral cortex: outer layer of forebrain;
allows you to see, read, and
understand words
(d) limbic system: in core of forebrain;
regulates our emotions and
motivation
LOBES OF BRAIN
*the cerebrum is 2 hemispheres or 2 sides
(right and left)
*the 2 sides are connected by a band of fibers
called the corpus callosum
(a) left hemisphere: controls movement of
the right side of the body
*controls speech, mathematical
ability, calculation, logic
(b) right hemisphere: controls left side of
body
*visual and spatial (putting together
a puzzle), recognizes patterns,
creativity