The Nervous System
Function: Recognizes and coordinates the body's __________ to changes in its
internal and external environments.
Structures:
Neurons: The nervous system carries messages as _______________ signals
(__________). The nerve cells that carry these impulses are called _________.
1. The 3 types of neurons:
a. _______________: carry messages from sensory organs (such
as the ear or eye) to the brain or spinal cord.
B: ________________: carry impulses from the brain or spinal
cord to the muscles or glands.
c. ____________________: connect sensory and motor neurons.
2. The parts of the neuron:
Although there are numerous types of neurons, they have the following parts in
common:
a. ______________: contains nucleus, cytoplasm; most metabolic
activities take place here.
b. ___________: short extensions of the cell body; carry impulses
from the body or other neurons to the cell body.
c. ____: a long fiber that carries impulses away from the cell body.
d: ___________________:found at the end of the axon; contain
hundreds of vesicles that contain neurotransmitters.
e. ____________________: found in longer neurons, this is a fatty
membrane that insulates the neuron; this speeds the transmission rate of
impulses.
Nerve impulse:
1. The nerve at rest: the neuron has a net ________ charge outside the
cell and a net _____________ charge inside the cell. This is caused by the
active transport of ions across the cell membrane.
The cell pumps Na+ out of the cell and K+ ions in (the sodium-potassium
pump). This causes a higher concentration of K+ in the cell and a lower
concentration of Na+ out. The cell membrane allows more K+ to leak out of the
cell which produces a negative charge on the inside. This electrical charge is
known as the ______________________.
2. The moving impulse: neurons stay at rest until a ________ (from the
environment or another neuron) starts a nerve __________. This causes ions to
move across the membrane. The impulse moves from the cell body to the axon
terminals. This causes a reversal in the charges along the membrane (see
transparency).
The cell membrane of the neuron contains numerous protein channels
that allow ions to move through it. As an impulse moves along a neuron, these
channels open, allowing Na+ ions in. This switches the charges of the
membrane... the inside becomes positive while the outside becomes negative.
This reversal of charge is called the __________________________.
Once the impulse passes, potassium gates open allowing K+ out. This
restores the resting potential.
3. Threshold: the threshold is the _______ level of stimulus to activate a
neuron. A stimulus that is lower than the threshold will not produce an impulse.
4. The synapse: the impulse arrives at the end of the neuron, the axon
terminal. Here it passes the impulse to another cell, such as a muscle cell. The
location at which a neuron can transfer an impulse to another cell is called
the______________. The axon terminal contains vesicles filled with
_______________________, chemicals that transmit an impulse from one cell to
another.
Types of neurotransmitters:
a. ____________: functions include learning, sleep, and control of
mood. It is similar to drugs that cause mental aberrations such as LSD;
________________ has been linked to low levels of serotonin.
b. ____________: stimulates muscles; some poisons block its
transmission; nerve gas breaks it down.
c. ________________: increases heart rate and blood pressure in
response to short term stress (activates “fight or flight”); low levels associated
with _______________.
d. _________________: high levels are associated with
___________________.
Divisions of the Nervous System:
1. _____________________________________:
a. Functions: relays _____________, processes information, and
analyzes information.
b. Structures: composed of the ______, __________, _________
(connective tissue covering the brain and spinal cord), _____________________
(fluid that bathes brain and spinal cord; acts as shock absorber; allows for
nutrient and waste exchange).
1. The ________: composed of 100 _________ neurons.
a. cerebrum: largest region; responsible for voluntary
activities, intelligence, learning , and judgment; divided into left and right
hemispheres connected by tissue called the _____________. Each hemisphere
deals mainly with the opposite side of the body (left hemisphere controls right
side of body); right hemisphere associated with creativity and artistic ability; left
hemisphere associated with analytical skills and mathematical ability. Composed
of two layers: gray matter (cerebral cortex) that processes information and
controls body movement; white matter that connects the cerebral cortex to the
brain stem.
b. __________________: coordinates and balances
muscle movement to allow for grace and efficiency.
c. ____________: connects the brain to the spinal
cord; composed of the pons and the medulla oblongata; controls functions such
as blood pressure, heart rate, breathing and swallowing.
d. __________: receives sensory information and
relays it to cerebrum for processing.
e. ______________: control center for recognition of
hunger, thirst, fatigue, anger and body temperature; controls the coordination of
the nervous and endocrine systems.
2. The ________________: major link between the brain
and the body; ___ pairs of nerves branch from it to the rest of the body; many
______ (quick, automatic response such as sneezing or blinking) are processed
directly in the spinal cord.
2. The ___________________________________:
A. Composed of:
1. the ________ and supporting cells that are not part of
the brain and spinal cord.
2. May be divided into two parts:
a. _________: sends impulses from sense organs to
CNS.
b. ________: sends impulses from CNS to muscles
or glands; May be divided into ______________ nervous system (conscious
control): example: stepping on sharp object →sensory neuron→spinal
cord→motor neuron causing foot to pull away from object. This is called a ____
_____. The second division is called the __________ nervous system: regulates
automatic or involuntary activity such as heart rate or contraction of the smooth
muscle in the digestive system. The autonomic nervous system slows activity
with the _____________________ nervous system and increases activity with
the _____________________ nervous system.