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NERVOUS SYSTEM
1. Function: Controls and coordinates functions throughout the body and responds to internal and external
stimuli
2. Neurons are… cells that transmit electrical impulses
a.) Sensory neurons: carry impulses from the sense organs to the spinal cord and brain
b.) Motor neurons: carry impulses from the brain and spinal cord to muscles and glands
c.) Interneurons: connect sensory and motor neurons and carry impulses between them
3. Neuron Parts and Function
a.) Cell Body: contains the nucleus and most of the cytoplasm; location of cellular metabolic activity
b.) Dendrites: carry impulses from the environment or from other neurons toward the cell body
c.) Axon: carries impulses away from the cell body
d.) Node: increase the speed at which an impulse can travel
e.) Myelin Sheath: insulates the axon
4. A nerve impulse is similar to… the flow of electrical current through a metal wire
a.) Resting potential of a neuron occurs when… there is an equal but opposite net charge across a
neural membrane
b.) A nerve impulse becomes electrically charged when… there is a difference in electrical charge
between the outer and inner surfaces of a neuron
c.) An impulse begins when… a neuron is stimulated by another neuron or by the environment
d.) A nerve impulse is also known as… action potential
e.) A nerve impulse is self – propagating because… an impulse at any point on the membrane causes
an impulse on the next point on the membrane
f.) Importance of the Na – K pump: maintains the resting potential of a neuron
Resting Potential The sodium-potassium pump in the
neuron cell membrane uses the energy of ATP to pump Na+
out of the cell and, at the same time, to pump K+ in. This
ongoing process maintains resting potential.
5. A threshold is… the minimum level of a stimulus that is required to activate a neuron
6. A synapse is… the location at which a neuron can transfer an impulse to another cell
7. Neurotransmitters are… chemicals used by a neuron to transmit an impulse across a synapse to another
Cell
1. An action potential is generated as Na+ flows inward across
the membrane at 1 location.
2. To the left the membrane is repolarizing as K+ flows
outward. depolarization of the action potential spreads to
the neighboring region of the membrane reinitiating the
action potential there.
3. The depolarization repolarization process is repeated in the
next region of the membrane in the way local currents of
ions across the plasma membrane cause the action
potential to be propagated along the length of the axon.
CNS
CENTRAL NERVOUS SYSTEM
PNS
PERIPHERAL NERVOUS SYSTEM
FUNCTION: relays messages, processes and
analyzes information
FUNCTION: transmits impulses from the sense
organs to the CNS and transmits
impulses from the CNS to muscles and
glands
PARTS AND FUNCTION
PARTS AND FUNCTION
1. Brain: Control center; sends and receives
impulses
a.) Cerebrum: responsible for voluntary or
conscious activities of the body; site of
intelligence, learning and judgment
1. Somatic Nervous System: regulates activities
that are under
conscious control
a.) Reflex arc: quick response to a stimulus;
includes sensory receptor, sensory neuron,
motor neuron and an effector
b.) Cerebellum: coordinates and balances
the actions of the muscles
c.) Brain Stem: regulates the flow of information
between the brain and the rest of the body;
controls blood pressure, heart rate, breathing,
swallowing; includes the Pons and Medulla
Oblongata
d.) Thalamus: receives messages from all of
the sensory receptors throughout the body
and relays that information to the proper
region of the cerebrum for further
processing
e.) Hypothalamus: control center for
recognition and analysis for hunger, thirst,
fatigue, anger, and body temperature; also
controls the coordination of the nervous and
endocrine system
2. Spinal Cord: main communication link
between the brain and the rest of
the body; processes different kinds
of reflexes
a.) Reflex: a quick, automatic response to a
stimulus
2. Autonomic Nervous System: regulates
activities that are
automatic or
involuntary;
controls
responses that
are not under
conscious
control
a.) Sympathetic and Parasympathetic
Nervous Systems: maintain homeostasis by
having opposite effects
on the same organ