Download The Nervous System

The Nervous System
I.
Response to Stimuli
A. your body responds to changes in the environment and adjusts itself
B. stimulus: _________________________________________________________________
C. Internal control systems respond to maintain ______________________
D. The nervous system controls and coordinates function throughout the body and responds to
internal and ________________ stimuli
II.
Neurons
A. definition:
B. receptors: located in skin and sense organs, these transmit stimuli (nerve impulses) to
different types of neurons
C. types1.
________________________: receive info from sense organs and send
impulses to the brain and spinal cord
2.
interneurons: relay the impulses from the sensory neurons once they reach the
brain or spinal cord to the ________________ neurons (most numerous)
3.
_______________________: conduct impulses from the brain or spinal cord
to muscles or _____________ throughout the body
D. structure:
1.
cell body: _______________________________________
2.
dendrite:
i. receives messages and sends them to the ___________________
ii. many branched extensions
3.
________________:
i. long fiber that carries messages ___________ from the cell body
ii. single branched end have swellings called __________________
iii. may have a myelin sheath: insulating membrane which increases the speed
at which __________________ can travel
E. nerve: clusters of dendrites and axons
III.
The Nerve Impulse:
A. Definition: electrical signals carried by a neuron depending on the movement of negatively
charged electrons (e-)
B. Resting Potential in a neuron: the difference in electrical charge across a membrane
1.
there are more ________________ ions (K+) inside the cell than outside
2.
there are more ______________ ions (Na+) outside of the cell than inside
3.
these concentrations must be maintained by _________________________
4.
negative charge builds up inside the cell as more K+ ions diffuse out than Na+
diffuse in
C. The Moving Impulse
1.
a nerve impulse is caused by the movement of ______ across a membrane
and begins when a neuron is stimulated by another neuron or its environment
2.
a neuron’s cell membrane has 1000’s of _________ channels that allow ions
to pass through when the “gates” are opened
3.
as an impulse moves down a neuron, the “gates” are opened and ______
flows _______ the cell
4.
the cell membrane gains a “+” charge inside and a “–“ charge outside creating
an ________________________
5.
as the impulse passes, the K+ gates open and these ions move _________ of
the cell and the ______________________ is re-established
D. Threshold
1.
the strength of the __________ is always the same (you respond or you don’t)
2.
the __________ must be of adequate strength to cause an impulse = threshold
E. ________________: location at which a neuron can transfer an impulse to another cell
1.
a small cleft (gap) separates the ______________________ from the
dendrites of the adjacent cell
2.
the terminals contain tiny sacs filled with __________________________
(chemicals used by a neuron to transmit impulses across a synapse)
3.
when an action potential arrives at the axon terminal, the sacs release the
neurotransmitter into the ____________
4.
neurotransmitter diffuses across the cleft and attach themselves to
___________________ on the membrane of the adjacent cell
5.
this stimulus causes ___________ to rush across the membrane
6.
if the threshold is met, then the impulse begins an action potential in the next
cell
IV.
Central Nervous System (CNS)
A. made of the ____________ and __________________________
B. job: relay messages, processes information, and analyzes information
C. brain
1.
made up of 100 billion neurons (mainly ______________________)
2.
divided into 3 major sections
i. _____________________ (largest)
- responsible for conscious/voluntary activities of the body
- divided into 2 sections called ______________________,
controlling the opposite side of the body
- the _________ hemisphere may control creativity and artistic ability
- the left hemisphere may control analytical and mathematical ability
- site of learning, judgment, and _____________________
- the cerebral ___________ (outer layer) consists of grey matter with
densely packed nerve cell bodies (______________) which process
info from the sense organs and control body movements
- the inner surface of the cerebrum consists of white matter made up
of _____________________________ of the axons
ii. ______________________
- behind and under the cerebrum
- coordinates _________________ muscle movement
- maintains balance and muscle tone
iii. brain stem
- extends out from the cerebrum and connects the brain to the spinal
cord
- made up of the midbrain, the pons, and medulla oblongata: these
regulate the flow of info to the brain from the rest of the body
- controls ___________________, breathing, and blood pressure by
coordinating involuntary muscle movements
iv. ________________________:
- found between the brain stem and cerebrum
- receives messages from the _______________________ and relay
info to the proper section of the cerebrum
v. _________________________
- found between the brain stem and cerebrum
- control center for recognition of _____________, hunger, fatigue,
_____________, and body temp
D. spinal cord
1.
extension of the brain stem
2.
processes _____________________
3.
made of bundles of neurons that carry impulses from all parts of the body to
the brain and from the brain to all parts of your body
E. protection
1.
the _________________ protects the brain
2.
the ___________________ protect the spinal cord
3.
both are wrapped in three layers of connective tissue called the meninges
4.
space between these layers is filled with _____________________________
that acts as a shock absorber
V.
Peripheral Nervous System (PNS)
A. all of the nerves outside of the central nervous system including the spinal and cranial
nerves which connect the brain and spinal cord to other body parts
B. made up of
1.
12 pairs of cranial nerves (from brain)
2.
31 pairs of spinal nerves (from cord) which are bundles of sensory and motor
neurons
C. 2 divisions
1.
_________________: transmits impulses from sense organs to the CNS
2.
motor:
i. transmits impulses from the CNS to __________________________
ii. further divided into the somatic and autonomic system
- _________________: cranial and spinal nerves that go from the
CNS to your skeletal muscles; voluntary movements and reflex arcs
- _________________: controls heart rate, breathing, digestion, and
gland functions; involuntary movements; sympathetic and
parasympathetic systems
V. Reflexes
A. definition: _________________________________________________________________
B. involves a simple nerve pathway called a _____________________
Example – touching a hot pan
i.
sensory receptors in fingers respond to the hot metal
ii.
an impulse relaying this information is sent via sensory neuron to the spinal cord
iii.
iv.
the impulse passes to an interneuron in the spinal cord
impulses are immediately sent to the motor neurons in your arm causing you to
move your hand
C. reflexes are controlled by your ______________________
D. your brain acts after reflexes occur to help you figure out how to stop the pain, calm heart beat,
slow breathing, etc = maintain __________________________
VI.
The Senses
A. Your senses enable you to hear, see, taste, touch, and smell whatever comes into your
environment.
B. The energy that stimulates your sense organs may be in the form of light rays, heat, sound
waves, chemicals, or pressure.
C. Five categories of sensory receptors:
1.
____________________________: throughout body (except brain) that
respond to chemicals released by damaged cells
2.
thermoreceptors: in ______________________________________________
3.
_____________________________: in skin, skeletal muscles, and inner ears
4.
chemoreceptors: ________________________________
5.
____________________________: in eyes
VII.
Vision
A. Light travels in straight lines/rays and is bent by the ______________ and ___________
B. lens: convex lens that directs the rays onto the retina
C. retina:
1.
tissue at the back of the eye that is sensitive to light energy
2.
contains _________: cells that respond to dim light used to detect shapes and
movement
3.
contains _______________: cells that respond to bright light and color
D. How you see:
1.
Light rays are focused by the cornea and lens onto the ______________ and a
sharp image is formed
2.
Light energy stimulates impulses in the retinal cells which pass impulses to
the ________________________ then to the brain.
3.
The brain interprets theses impulses = you “see” the image
E. Convex lens:
1.
thicker in the _______________ and thinner on the _________________
2.
causes parallel light rays to come together at a focus point
F. Concave lens: lens that is thicker on the edges and thinner in the middle
G. Correcting vision
1.
_______________________
i. if the eyeball is too ______________, light from distant objects is focused
just in ____________ of the retina and a blurred image is formed
ii. _________________ lenses are used to correct
2.
farsightedness
i. if the eyeball is too ____________, light from nearby objects is focused
________________ the retina and a blurred image is formed
ii. __________________ lenses are used to correct
VIII.
Hearing
A. How you hear:
1.
When objects vibrate, they cause the air around them to vibrate creating
energy in the form of sound waves.
2.
When the waves reach your ears they stimulate nerve cells deep in the ear.
3.
impulses are sent from these cells to the brain
4.
the brain responds and you hear a sound
B. the ear is divided into 3 sections
1.
________________
i. traps sound waves and funnels them into the ear canal and middle ear
ii. the sound waves cause the eardrum (membrane) to vibrate like a drum
2.
____________________
i. vibrations from the eardrum cause little bones (__________, __________,
____________________) to vibrate
ii. the stirrup bone rests against a second membrane on the opening of the
inner ear
3.
inner ear
i. _____________: fluid filled structure like a snail’s shell that vibrates from
the stirrup’s vibrations causing nerve endings to send impulses to the brain
via the ________________________ nerve
ii. high-pitch sounds make the nerve endings move differently than lowpitched sounds
iii. balance is also controlled here
- special structures and fluids in the _________________________
are constantly adjusting to the position of your head
- this stimulates impulses to the brain which interprets the position to
help you adjust and maintain your balance
IX.
Smell
A. Food gives off gas molecules into the air which are taken into the nasal passage
B. _____________________cells are moistened; specialized nerve cells that are stimulated by
the gas molecules when these molecules dissolve in the moisture
C. If enough molecules are present, am impulse starts in these cells and travels to the brain
and you “smell” the item
X.
Taste
A. Taste buds on your tongue are the major chemical sensory receptors for taste
B. 10,000 taste buds in your mouth
C. In order to taste something, the food must be dissolved in ______________, therefore the
nervous system triggers salivation when it is time to eat
D. The solution of saliva and food molecules wash over your taste buds and an impulse is sent
to the brain
E. The brain interprets the impulse and you can taste the food.
F. Four basic areas of taste buds: ____________________________________
G. When you are sick, you have trouble tasting food because the gas molecules are blocked
from dissolving in the moist membranes of the nasal passage.
XI.
Touch, Pressure, Pain and Temperature
A. Receptors in the skin (_____________) pick up changes in touch, pressure, and
temperature and transmit impulse to the brain or spinal cord
B. The body will respond to maintain homeostasis