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Exercise Physiology -Chapter 7
Huang-The Nervous System
122
Physiology
Undergraduate 3
02/23/2014

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Term
The nervous system is divided into 2 sections. What are they?
Definition
central nervous system (CNS)
peripheral nervous system (PNS)
Term
What does the CNS consist of?
Definition
brain
spinal cord
Term
What does the PNS consist of?
What are the two divisions of the PNS?
Definition
all neurons outside the CNS

sensory
motor
Term
What is the sensory division of the PNS?
Definition
afferent fibers transmit impulses from receptos to CNS
Term
What is the motor division of the PNS?
Definition
efferent fibers transmit impulses from CNS to effectos organs
Term
What does the motor division play a role in?
Definition
muscle contraction
Term
What is a motor neuron?
Definition
a neuron from the CNS to a muscle
Term
T/F The postganglionic axon in the parasympathetic nervous system is long, but short in the sympathetic nervous system.
Definition
False
the postganglionic axon is shot in the parasympathetic nervous system and long in the sympathetic system.
Term
What is the length of postganglionic axon in the sympathetic nervous system?
Definition
long
Term
What are the effector organs of the sympathetic nervous system?
Definition
smooth muscle
cardiac muscle
glands
Term
What is the neurotransmitter and receptor type of the sympathetic nervous system?
Definition
ACh
nicotinic receptor
Term
What is the neurotransmitter in the effector organs of the sympathetic nervous system?
Definition
NE
Term
What are the receptor types in the effector organs of the sympathetic nervous system?
Definition
alpha 1 & 2
beta 1 & 2
Term
What are the effector organs of the parasympathetic nervous system?
Definition
smooth muscle
cardiac muscle
glands
Term
T/F The preganglionic axon is short in the sympathetic nervous system, but long in the parasympathetic nervous system.
Definition
True
Term
T/F ACh is the neurotransmitter for both the pre and postganglionic axon for the parasympathetic nervous system.
Definition
True
Term
T/F The receptor type in the ganglion is the same in the parasympathetic and sympathetic nervous system.
Definition
True
nicotinic receptor
Term
What is the receptor in the effector organs of the parasympathetic nervous system?
Definition
muscarinic
Term
The somatic nervous system deals with what type of neurons?
Definition
motor neurons
Term
What are the effector organs of the somatic nervous system?
Definition
skeletal muscles
Term
T/F The somatic nervous system has both a pre and post ganglionic axon.
Definition
False
the somatic nervous system has no ganglion
Term
What is the neurotransmitter of the somatic nervous system?
Definition
ACh
Term
What is the receptor in the effector organ of the somatic nervous system?
Definition
nicotinic
Term
What is the difference between neurons and nerves?
Definition
size
Term
When are neurons called nerves?
Definition
when they are bundled in the periphery
Term
Do nerve cells need energy?
What is their primary source of energy?
Definition
yes
glucose
Term
T/F Nerves can contain only sensory or motor neurons.
Definition
False
nerves can also contain both sensory or motor neurons
Term
How many regions can the neuron be divided into?
What are these regions called?
Definition
3
Cell body
Dendrites
Axon
Term
The cell body of the neuron contains what?
Definition
nucleus
Term
What is the role of the dendrites?
Definition
conduct impulses toward the cell body
take information into the cell body
Term
What is the role of the axon?
How many axons can a neuron have?
Definition
carries electrical impulses away from the cell body to effector organs
one
Term
What is the axon covered in?
Definition
Schawnn cells
form the discontinuous myelin sheath
Term
What is a synapse?
Definition
contact points between avon of one neuron and dendrite of another neuron
Term
What is the surface of the axon, smooth or rough?
Definition
smooth
Term
T/F A neuron can have more the one axon.
Definition
False
ONLY ONE AXON PER CELL, but it can be divided into collateral branches
Term
What does the myelin sheath do?
Definition
protect the axon
Term
What is the surface of the dendrite, smooth or rough?
Definition
rough
Term
T/F Usually many dendrites per cell.
Definition
True
Term
T/F Dendrites have a myelin sheath.
Definition
False
no myelin sheath
Term
T/F Usually the larger diameter or the axon, the greater the speed of neural transmission.
Definition
true
Term
T/F Axons with smaller myelin sheaths conduct impulses more rapidly.
Definition
False
axons with larger myelin sheaths conduct impulses more rapidly
Term
what is the longest cell in the body?
Definition
neuron
Term
what is the oldest cell in the body?
Definition
neuron
Term
What is the disadvantage of nerve cells?
Definition
When damaged or die they cannot be replaced
Term
What happens when there is damage to the myelin sheath?
Definition
slows down the speed of neural transmission
Term
What is multiple sclerosis?
Definition
neurological disease that destroys myelin sheath axons
autoimmune disease
Term
Can exercise treat multiple sclerosis?
Definition
No, but there are some studies the suggest exercise can influence cellular and immune parameters
Term
What kind of tissue are neurons?
Definition
excitable tissue
Term
What is irritability?
Definition
ability to respond to a stimulus and convert it to a neural impulse
Term
What is conductivity?
Definition
transmission of the impulse along the axon
Term
What is resting membrane potential?
Definition
the potential difference that exists across the membrane of excitable cells such as nerve and muscle cells

when all these ion forces balance out
Term
Can our cells be activated all the time?
Definition
No, waste of energy
Term
To activate a muscle cell we must increase or decrease the membrane potential?
Definition
increase
Term
At rest, the membrane potential is positive or negative?
Definition
negative
Term
What is the resting membrane potential?
What does this mean?
Definition
-70mV
inside the cells has 70mV less than outside the cell
Term
The process of making the inside of the cell more positive to activate is called what?
Definition
depolarization
Term
T/F the negative charge inside the cell CANNOT cross the membrane and attract positive charges from the extracellular fluid.
Definition
True
Term
At rest which two ions can pass easily across the membrane?
Definition
K+
Cl-
Term
What is the -70mV resting membrane potential determined by?
Definition
the permeability of membrane to different ions
ion concentration
Term
What are the major regulators of membrane potential?
Definition
K
Na
Term
T/F K+ is highest inside the cell, Na+ is highest outside the cell
Definition
true
Term
At rest almost all Na+ channels are (open/closed), but few K+ channel gates are still (open/closed).

What does this result in?
Definition
closed
open

a net loss of positive charges
Term
How can NE/E regulate Ca levels?
Definition
beta receptors open Ca channels to bring Ca into the cell
alpha receptors break down glucose
Term
How do you prevent a net loss of positive charges?
Definition
the cell membrane has a Na+/K+ pump using ATP to maintain both Na+ and K+ intracellular and extracellular concentrations and resting membrane potential
Term
How much Na+ to K+ does the Na+/K+ pump?
Definition
3 Na+ out per 2 K+ in for each cycle of the Na+/K+ ATPase
Term
What hormone regulates K+ concentration?
Definition
aldosterone
Term
Occurs when a stimulus or sufficient strength depolarizes the cell.
Definition
Depolarization
Term
Returns to resting membrane potential, gains negative charge.
Definition
Repolarization
Term
What happens during depolarization?
Definition
open Na+ channels and Na+ diffuses into the cell
K+ channels closed
inside becomes more positive
Term
What happens during repolarization?
Definition
open K+ channels, K+ leaves the cell rapidly
Na+ channels closed
Term
Once a nerve impulse is initiated, it will travel the length of one neuron without a decrease in voltage.
Definition
All-or-None Law
Term
At 30mV what position are the Na+ channel gates in?
Definition
closed
Term
Before the impulse the Na+ gates are?
Definition
open
Term
After the impulse the K+ gates are open or closed?
Definition
open
Term
T/F Repolarization immediately follows depolarization.
Definition
True
Term
Small gap between presynaptic neuron and postsynaptic neuron.
Definition
Synapse
Term
What is a neurotransmitter?
Definition
chemical messenger released from presynaptic membrane
binds to a receptor in postsynaptic membrane
causes depolarization of postsynaptic membrane
Term
What happens after the muscle is depolarized?
Definition
Ca is released from the sarcoplasmic reticulum
requires an action potential
binds to triponin C
Term
What are the steps of synaptic transmission?
Definition
Step 1: action potential travels down the motor neuron to the presynaptic terminal

Step 2&3: depolarization of the presynaptic terminal opens Ca2+ channels and flows into the presynaptic terminal, which causes ACh to be released by exocytosis.

Step 4&5: The ACh diffuses across the the synaptic cleft and binds to nicotinic receptors on the postsynaptic membrane, opening Na+ channels. Allowing Na+ to enter and cause the depolarization (excitatory postsynaptic potentials)

Step 6: the depolarization of the postsynaptic membrane spread by local currents to muscle fibers to reach action potential

Step 7: to prevent chronic depolarization of the postsynaptic neuron, the ACh must be degraded. The postsynaptic neuron becomes repolarized
Term
How is ACh degraded?
Definition
detaches from the receptor
broken down by AChE to choline
almost 50% of choline is pumped back into the presynaptic neuron to be used to make ACh
Term
Why is calcium required for muscle contraction?
Definition
Ca uptake needed to release ACh
Term
T/F all neurotransmitters are excitatory.
Definition
False
NOT ALL neurotransmitters are excitatory some are inhibitory
Term
what are EPSPs?
Definition
excitatory postsynaptic potentials
cause depolarization
Term
what are IPSPs?
Definition
inhibitory postsynaptic potentials
causes hyperpolarization
more negative
Term
What is hyper polarization?
What causes it?
Definition
more negative than resting membrane potential
causes by the efflux of K+ or influx of Cl-
Term
T/F ACh has inhibitory abilities, but not excitatory.
Definition
False
ACh has both
Term
How do EPSPs bring a neuron to threshold?
Definition
Temporal summation
spatial summation
Term
What is temporal summation?
Definition
to sum several EPSPs from a single presynaptic input over a short time
Term
What is spatial summation?
Definition
to sum EPSPs from several different presynaptic inputs
Term
What is motor systems?
Definition
posture and movement depend on a combination of involuntary reflexes coordinated by the spinal cord
Term
What is a motor unit?
Definition
one motor neuron and the muscle fibers it innervates
Term
How is the amount of muscle fibers being innervated determined?
Definition
the nature of the motor activity
Term
what is a motor neuron pool?
Definition
the set of motor neurons innervating fibers with the same muscle
Term
what are the two types of motor neurons?
Definition
alpha
gamma
Term
alpha motor neurons have small or large diameters?
Definition
large diameters
Term
what do alpha motor neurons innervate?
Definition
normal muscle fiber (extrafusal) that generate tension by contracting to allow skeletal movement
Term
gamma motor neuron have smalle or large diameters?
Definition
small diameters
Term
what do gamma motor neurons innervate?
Definition
thin muscle fiber (intrafusal), a component of muscle spindles that provides sensory information about changes in muscle length
Term
what are extrafusal fibers?
innervated by?
what are the used for?
Definition
normal muscle fibers
innervated by alpha motor neurons
used to generate force
Term
what are intrafusal fibers?
innervated by?
Definition
thin muscle fibers
innervated by gamma motor neurons
too small to generate significant force
muscle spindle composed of several intrafusal fibers
Term
What is the muscle spindle?
Definition
insert into the connective tissue within the muscle
Term
what does the muscle spindle consist of?
Definition
intrafusal fiber
sensory neuron
gamma motor neuron
Term
what do primary nerve fibers detect?
Definition
velocity of length changes
Term
what do secondary nerve fibers detect?
Definition
length of the muscle fiber
Term
T/F alpha and gamma motor neurons are activated simultaneously.
Definition
true
Term
what is the stretch reflex?
Definition
stretch on muscle causes reflex contraction
Term
step by step function of the muscle spindle.
Definition
Step 1: when a muscle is stretched, the extrafusal and intrafusal muscle fibers are lengthened

Step 2: this increase in length of intrafusal fibers is detected by and activate the sensory nerve fibers

Step 3: activations of sensory nerve fibers stimulate alpha motor neuron in the spinal cord

Step 4: then this alpha motor neuron innervates extrafusal fibers in the same muscle resulting in (1) the muscle contracts and (2) resisting being stretched thereby decreasing stretch on the muscle spindle which returns to original length
Term
When the extrafusal fiber is activated what happens to synergistic and antagonistic muscles?
Definition
synergistic are activated
antagonistic relax
Term
what is the Golgi Tendon Organ?
Definition
a stretch receptor found in tendons
Term
How does the GTO work?
Definition
Step 1: when the muscle contracts, the extrafusal muscle fibers become shorter, activation GTOs

Step 2: when activated, the GTO sends information to the spinal cord via sensory neuron that synapse on inhibitory interneuron in spinal cord

Step 3: when the inhibitory interneuron is activated, it inhibits the alpha motor neuron, producing relaxation of the contracting muscle
Term
During exercise training, why can you lift more weight?
Definition
desensitize the GTO
Term
What happens at the same time as the relaxation of the synergistic muscles in the GTO?
Definition
the contraction of antagonistic muscles
Term
What is the crossed extensor reflex?
Definition
occurs in response to painful stimulus
Term
How does the crossed extensor reflex work?
Definition
Step 1: when your right hand touches are hot stove, a sensory neuron is activates to synapse on multiple interneurons in the spinal cord, which then innervate alpha motor neurons

Step 2: then, the reflex is activated to cause flexor muscles to contract and extensor muscles to relax (reciprocal inhibition)

Step 3: however, on your left hand this reflex causes flexor muscles to relax and extensor muscles to contract to maintain balance
Term
What is reciprocal inhibition?
Definition
simultaneous excitatory and inhibitory activity
Term
How many synapses do each reflex have?
stretch?
GTO?
crossed-extensor?
Definition
strech:1
GTO:2
crossed-extensor: many
Term
what is the stimulus for the stretch reflex?
Definition
stretch or muscle
Term
what is the stimulus of the GTO?
Definition
contraction of the muscle
Term
what is the stimulus of the crossed-extensor reflex?
Definition
pain; temp
Term
what is the response of the stretch reflex?
Definition
contraction of the muscle
Term
what is the response of the GTO?
Definition
relaxation of the muscle
Term
what is the response of the crossed-extensor reflex?
Definition
flexion on ipsilateral side; extension on contralateral side
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