HES 202 FINAL EXAM UPDATED ACTUAL QUESTIONS
AND CORRECT ANSWERS
Question:
(1) What is the component of the motor neuron where excitatory post-synaptic
potentials summate to generate an action potential?
Answer:
Axon Hillock
Question:
(1) What is a motor unit?
Answer:
A motor unit is a motor neuron and all of the muscle fibers it innervates
Question:
(1) What are the three types of motor units and their characteristics?
Answer:
1. Type 1 MUs, S motor neurons innervate SO type muscle fibers forming S
type motor unit
2. Type IIa MUs, FR motor neurons innervate FOG type muscle fibers forming
FR type motor units
3. Type IIb MUs, FF type motor neurons innervate FG muscle fibers forming FF
type motor units
Question:
(1) What would be the benefit of low threshold (type 1) motor neurons or
small motor neurons innervating slow oxidative muscle fibers/ large motor
neurons and high threshold (type II) motor neurons innervating fast
contracting, fast fatigable of fast glycolytic muscle fibers
Answer:
Endurance, relevant amounts of force, and relevant speeds of force, and that
type 1 is used before type 2
i.e fast contracting is in reserve
Question:
(1) Define Rheobase
Answer:
Rheobase is the direct measure of how much current there has to be put into a
neuron to get it to fire
Ex: rheobase is low in small motor neurons
Question:
(1) How is force controlled inside the muscle?
Answer:
Force is controlled by altering the # of active Mus (de/recruitment) & changing
the frequency of activation (rate coding- MU discharge rate)
Question:
(1) Draw the action potential graph.
,Answer:
Question:
(1) What insulates the axon and stops the movement of sodium and potassium
from moving across?
Answer:
Myelin sheath
Question:
(1) Draw a neuromuscular junction and all it's components
Answer:
Question:
(1) Describe the role of the neuromuscular junction in muscle contraction
Answer:
As axon of motor unit reaches muscle it splits into branches and creates a
synapse called the neuromuscular junction
When action potential reaches a neuromuscular junction is causes
acetylcholine to bind to nicotinic receptors (lets sodium ions into muscle fiber)
If enough of these sodium ions enter then they trigger a muscular action that
spreads throughout the fiber
The potential goes through the sarcolemma to reach the myofibrils,
the T-tubule system, and there the action potential reaches the sarcoplasmic
reticulum which stores calcium for contraction
Question:
(1) Why does botox make the person look lifeless? (curare vs botulinum toxin)
Answer:
Botox paralyzes the muscle by preventing the release of ACH
Similar to the poison Curare and botulinum toxin which prevent the release of
acetylcholine into the neuromuscular junction
Question:
(1) What do nicotinic re-ceptors bind to and what are the two types?
Answer:
Nicotinic receptors are what acetylcholine binds to.
The two types are N1 (ANS) and N2 (neuromuscular junction).
Question:
(1) What are muscarinic receptors and where are they found?
Answer:
Muscarinic receptors are a Large class of receptors called G-protein receptors
Receptors in this class are totally separate from ion channels
They exert their effects on these channels via a protein located on the
cytoplasmic side of the the cell (G proteins)
G protein receptors are slower then nicotinic receptors (found in CNS and the
heart)
Question:
(1) What is a twitch
Answer:
Twitch is a physiological response of a motor unit to stimulation
, This is a force time response to a single input
Question:
(1) What is the difference between fused and unfused tetanus?
Answer:
Unfused tetanus is the relaxation time between successive twitches will get
shorter as the strength of contraction increases in amplitude.
Fused tetanus is the Smooth, sustained muscle contraction.
Question:
(2) What are the two neural control strategies that grade force?
Answer:
Recruitment and Rate Coding
Question:
(2) What are the three types of muscle spindle fibers?
Answer:
Dynamic, Static and Nuclear
Question:
(2) Draw a muscle spindle
Answer:
Question:
(2) Draw the monosynaptic stretch reflex (tendon tap)
Answer:
Question:
(2) Explain orderly motor unit recruitment
Answer:
Motor units are recruited from smallest to largest because it simplifies the task
of modulating force not necessary for higher centers to select specific
combinations of MUs, ensures a smooth increase in force production,
minimizes fatigue as slow twitch, fatigue-resistant muscle fibers are activated
first
Question:
(2) What is the recruitment threshold?
Answer:
Recruitment threshold (amount of force to turn on MU) and it can change
within a motor unit.
The Order across motor units remains consistent
Question:
(2) Describe the rate coding of the motor unit.
Answer:
Force-frequency curve: sigmoidal relationship
The firing rate matches the contractile speed
Reaches plateau, either way,
There is a difference between slow and fast Ex: Solues vs tricep
Question:
(2) Why was the John Eccles Study on motor neurons significant?
AND CORRECT ANSWERS
Question:
(1) What is the component of the motor neuron where excitatory post-synaptic
potentials summate to generate an action potential?
Answer:
Axon Hillock
Question:
(1) What is a motor unit?
Answer:
A motor unit is a motor neuron and all of the muscle fibers it innervates
Question:
(1) What are the three types of motor units and their characteristics?
Answer:
1. Type 1 MUs, S motor neurons innervate SO type muscle fibers forming S
type motor unit
2. Type IIa MUs, FR motor neurons innervate FOG type muscle fibers forming
FR type motor units
3. Type IIb MUs, FF type motor neurons innervate FG muscle fibers forming FF
type motor units
Question:
(1) What would be the benefit of low threshold (type 1) motor neurons or
small motor neurons innervating slow oxidative muscle fibers/ large motor
neurons and high threshold (type II) motor neurons innervating fast
contracting, fast fatigable of fast glycolytic muscle fibers
Answer:
Endurance, relevant amounts of force, and relevant speeds of force, and that
type 1 is used before type 2
i.e fast contracting is in reserve
Question:
(1) Define Rheobase
Answer:
Rheobase is the direct measure of how much current there has to be put into a
neuron to get it to fire
Ex: rheobase is low in small motor neurons
Question:
(1) How is force controlled inside the muscle?
Answer:
Force is controlled by altering the # of active Mus (de/recruitment) & changing
the frequency of activation (rate coding- MU discharge rate)
Question:
(1) Draw the action potential graph.
,Answer:
Question:
(1) What insulates the axon and stops the movement of sodium and potassium
from moving across?
Answer:
Myelin sheath
Question:
(1) Draw a neuromuscular junction and all it's components
Answer:
Question:
(1) Describe the role of the neuromuscular junction in muscle contraction
Answer:
As axon of motor unit reaches muscle it splits into branches and creates a
synapse called the neuromuscular junction
When action potential reaches a neuromuscular junction is causes
acetylcholine to bind to nicotinic receptors (lets sodium ions into muscle fiber)
If enough of these sodium ions enter then they trigger a muscular action that
spreads throughout the fiber
The potential goes through the sarcolemma to reach the myofibrils,
the T-tubule system, and there the action potential reaches the sarcoplasmic
reticulum which stores calcium for contraction
Question:
(1) Why does botox make the person look lifeless? (curare vs botulinum toxin)
Answer:
Botox paralyzes the muscle by preventing the release of ACH
Similar to the poison Curare and botulinum toxin which prevent the release of
acetylcholine into the neuromuscular junction
Question:
(1) What do nicotinic re-ceptors bind to and what are the two types?
Answer:
Nicotinic receptors are what acetylcholine binds to.
The two types are N1 (ANS) and N2 (neuromuscular junction).
Question:
(1) What are muscarinic receptors and where are they found?
Answer:
Muscarinic receptors are a Large class of receptors called G-protein receptors
Receptors in this class are totally separate from ion channels
They exert their effects on these channels via a protein located on the
cytoplasmic side of the the cell (G proteins)
G protein receptors are slower then nicotinic receptors (found in CNS and the
heart)
Question:
(1) What is a twitch
Answer:
Twitch is a physiological response of a motor unit to stimulation
, This is a force time response to a single input
Question:
(1) What is the difference between fused and unfused tetanus?
Answer:
Unfused tetanus is the relaxation time between successive twitches will get
shorter as the strength of contraction increases in amplitude.
Fused tetanus is the Smooth, sustained muscle contraction.
Question:
(2) What are the two neural control strategies that grade force?
Answer:
Recruitment and Rate Coding
Question:
(2) What are the three types of muscle spindle fibers?
Answer:
Dynamic, Static and Nuclear
Question:
(2) Draw a muscle spindle
Answer:
Question:
(2) Draw the monosynaptic stretch reflex (tendon tap)
Answer:
Question:
(2) Explain orderly motor unit recruitment
Answer:
Motor units are recruited from smallest to largest because it simplifies the task
of modulating force not necessary for higher centers to select specific
combinations of MUs, ensures a smooth increase in force production,
minimizes fatigue as slow twitch, fatigue-resistant muscle fibers are activated
first
Question:
(2) What is the recruitment threshold?
Answer:
Recruitment threshold (amount of force to turn on MU) and it can change
within a motor unit.
The Order across motor units remains consistent
Question:
(2) Describe the rate coding of the motor unit.
Answer:
Force-frequency curve: sigmoidal relationship
The firing rate matches the contractile speed
Reaches plateau, either way,
There is a difference between slow and fast Ex: Solues vs tricep
Question:
(2) Why was the John Eccles Study on motor neurons significant?
