Neural Control of Exercising Muscle Flashcards
What is the nervous system divided into?
CNS (Central) and PNS (Peripheral)
What is the CNS and PNS composed of?
Brain/Spinal Cord & PNS composed of sensory and motor nerves
What are sensory and motor nerves also known as?
afferent and efferent
What are sensory nerves?
informing the CNS about what is going on within and outside the body (incoming)
What are motor nerves?
responsible for sending information from the CNS to the various tissues, organs, and systems of the body in response to the signals coming in from the sensory division (outgoing)
What are the motor nerves composed of?
autonomic and somatic nervous system; voluntary to skeletal muscles; involuntary to internal organs and bodily functions
What is the autonomic nervous system further divided into?
sympathetic and parasympathetic nervous system
What is the neuron and what three regions is it composed of?
neuron is the basic unit of nervous system; cell body, dendrites, and axon
Describe the cell body.
it contains a nucleus; cell processes radiate outward
Describe dendrites.
receives cell processes; carries impulse toward the cell body
Describe the axon.
sends cell processes by starting at the axon hillock; has end branches, terminals, and nuerotransmitters
Where does communication occur with the electrical signal?
between the periphery and brain
How is the electrical signal generated, propagated, and then transmitted?
stimulus; down an axon; to the next cell in line
What is the difference in electrical charges between the outside and inside of the cell?
-70 mV
Why is there a difference in electrical charges between the outside/inside the cell?
uneven separation of charged ions; polarized
Why is it -70 mV?
There is a higher concentration of sodium cells outside the cell and medium # of potassium cells; more negative inside to outside
Can Na+ ions enter the channel?
They’re unable to, but channels are closed.
Are K+ channels open?
Yes; K+ ions leave the cell.
Describe the pathway of how the neuron allows nerve impulses travel:
dendrites > cell body > axon hillock > axon > axon terminal
What are axon terminal (synaptic knobs) filled with?
neurotransmitters
When does depolarization occur?
when the inside of the cell becomes less negative (-70 mV to 0 mV)
Why does depolarization occur?
as more positively charged sodium channels open, the Na+ ions enter the cell
Which is required for nerve impulses to arise and travel?
depolarization
When does hyperpolarization occur?
when the inside of the cell becomes more negative (-70 mV to -90 mV), more K+ channels open, allowing K+ to leave the cell
Which makes it harder for nerve impulses to arise and travel?
hyperpolarization
What are graded potentials (GP), do they excite or inhibit?
localized changes in membrane potential; both cause depolarization/hyperpolarization
What are action potentials?
rapid/substantial depolarization of the neuron’s membrane; passes signal down the axon; only excitatory
Where are the ESPS’ being integrated?
at the axon hillock
What is it called when the membrane voltage at which graded potential becomes an action potential?
threshold
Can another action potential be generated, if it is already open?
If an axon’s sodium channels are open, they are all open, thus unable to respond to another stimulus
What is the absolute refractory period?
period from the initiation of the action potential to immediately after the peak’ a period in which another stimulus will not occur
What is the relative refractive period?
the interval of time during which a second action potential can be initiated, but initiation will require a greater stimulus than before
Which two characteristics determine how quickly a impulse can pass along an axon?
myelination and neuron diameter
Propagation of the action potential.
- resting membrane potential
- depolarizing stimulus
- membrane depolarizes to threshold causing Na+ channels open allowing Na+ ions to enter
- Rapid Na+ entry
- Na+ channels close and slower K+ channels open
- K+ moves from the cell to the ECF
- K+ channels remain open and more K+ ions leave, causing hyper-polarization
- Voltage-gated K+ channel’s close
- Cell returns to resting ion permeability and RMP
What is the inhibitory signal and the excitatory signal?
K+ efflux (hyper-polarization);
Na+ influx (depolarization)
-70 to -55 mV
depolarizing GP; Na+ influx
-55 to +30 mV
depolarizing AP; Na+ influx
+30 to -70 mV
re-polarizing AP, K+ efflux
Are Na+ channels open during the relative refractory period?
No, but could reopen.
Why do larger axon diameters result in faster propagation?
larger neurons present less resistance to local current flow
How are myelin sheaths formed?
specialized cells called schwann cells
What is saltatory conduction?
propagation of action potentials along myelinated axons from one node of Ranvier to the next node
What is the synapse?
junction or gap between neurons; serves as site of neuron-to-neuron communication
Describe how the signal changes form across the synapse
presynaptic to synaptic to postsynaptic; electrical to chemical to electrical
What do axon terminals contain? What do they serve, carry, bind to, and stimulate?
contains neurotransmitters;
serves as chemical messengers;
carries electrical action potential across the synaptic cleft;
bind to receptor on postsynaptic surface;
stimulates graded potential in postsynaptic neuron
What is the site of the neuron-to-muscle communication?
neuromuscular junction, where the postsynaptic cell is a muscle fiber
What is used as the neurotransmitter in neuron-to-muscle communication?
acetylcholine
Where does ACh bind to and what does it do?
binds to receptor at motor end plate and causes depolarization by opening up the sodium channels
Where does the action potential travel along?
spreads along the plasmalemma, down the T-tubules
Does the plasmalemma undergo re-polarization, after it has been depolarized?
yes; sodium gates close and potassium gates remain open
Which category of neurotransmitters is rapid-acting?
small molecules
Which category of neurotransmitters is slow-acting?
large molecules; neuropeptides
Which two neurotransmitters govern exercise?
acetylcholine and norepinephrine
What does the ACh stimulate?
skeletal muscle contraction; mediates parasympathetic nervous system effects
What does NE stimulate?
mediates sympathetic nervous system effects; can be either excitatory or inhibitory
What does binding to the postsynaptic membrane cause?
graded potential
What is the excitatory postsynaptic potential (EPSP)?
excitatory impulse causing depolarization
What is the inhibitory postsynaptic potential (EPSP)?
inhibitory impulse causing hyperpolarization
Which, EPSP or IPSP, prevents AP?
IPSP as it is hyperpolarizing and inhibitory
What happens to the neurotransmitters once an impulse has been successfully transmitted?
destroyed by enzymes, removed by reuptake int the presynaptic terminal, or diffuses away from the synapse
Acetylcholine regulates
somatic nervous system
Norepinephrine regulates
autonomic nervous system
What are the four major regions of the brain?
cerebrum
diencephalon
cerebellum
brain stem
What is the diencephalon composed of?
hypothalamus and thalamus
What is regulated by the hypothalamus?
regulating almost all processes that affect the body’s internal environment
What are some things that are regulated by the hypothalamus?
blood pressure, heart rate, and contractility; respiration; digestion; body temperature; thirst and fluid balance; neuroendocrine conntrol; appetite and food intake; and sleep-wake cycle
What is the brain stem composed of?
midbrain, pons, and medulla oblongata
What is the brain stem connected to and why?
connects to and information relays between brain/spinal cord
What does the brain stem contain autonomic centers for?
respiratory and cardiovascular systems
What is the specialized collection of neurons called, which influences and is influenced by?
reticular formation
What are the neurons of reticular formation helping with?
coordinate skeletal muscle function;
maintain muscle tone;
controls cardiovascular/respiratory functions; and
determines state of consciousness (arousal/sleeP)
what is continuous by the spinal cord?
medulla oblongata
Are afferent fibers sensory or motor?
sensory
Are efferent fibers sensory or motor?
motor
Are afferent fibers descending or ascending?
ascending
Are efferent fibers descending or ascending?
descending
How many pairs of cranial nerves are connected to the brain?
12
How many pairs of spinal nerves are connected to the brain?
31
Do both types of nerves (spinal and cranial) supply blood to skeletal muscle?
Yes
What does the sensory division of the PNS carry sensory information toward?
from periphery to the brain
What are the major families of sensory receptors?
mechanoreceptors (physical forces) thermoreceptors (temperature) nociceptors (pain) photoreceptors (light) chemoreceptors (chemical stimuli)
What are the special families of sensory receptors?
joint kinesthetic receptors;
muscle spindles; and
golgi tedon organ
Describe joint kinesthetic receptors.
sensitive to joint angles and rate of angle change; senses joint position/movement
Describe muscle spindles.
sensitive to muscle length (rate of change); senses muscle stretch
Describe golgi tendon organs.
sensitive to tension in tendon; senses strength of contraction
What does the motor division of the PNS carry sensory information toward?
from brain to periphery
How many subdivisions are included in the motor division? What are they?
2 subdivisions;
autonomic and somatic
Describe the autonomic and somatic subdivisions.
autonomic: regulates visceral activity; and
somatic: stimulates skeletal muscle activity
What does the autonomic nervous system control?
involuntary internal functions
What exercise-related autonomic regulation are involved?
heart rate, blood pressure, and lung funnction
What are the complementary divisions of autonomic nervous system?
sympathetic and parasympathetic nervous system
What nervous system is the fight or flight system associated with?
autonomic-sympathetic nervous system; prepares body for exercise
What does the sympathetic nervous system stimulate?
increases: heart rate and blood pressure; blood flow to muscles; airway diameter; metabolic rate, glucose levels, FFA levels; and mental activity
What nervous system is the rest and digestion system associated with?
parasympathetic nervous system
What does the parasympathetic stimulate?
increases digestion and urination;
conservation of energy;
decreased heart rate; and
decreased diameter of vessels/airways
What are the five sequential steps in sensory-motor integration?
- stimulus sensed by sensory receptor
- sensory action potential on sensory neurons to CNS
- CNS interprets sensory information, sending out an response
- motor action potential sends out on a alpha-motor neuron
- arrives at skeletal muscle and response occurs
What is the sensory-motor integration?
represents communication/interaction between the sensory/motor systems
What is the motor reflex?
instant, programmed response to stimulus (which is unchanged every time)
Which motor unit has more fibers? Fewer fibers?
gross motor control; and fine motor control
