Day 3 Flashcards
What do motor neurons connect with?
They connect with skeletal muscles
What do motor neurons tell the skeletal muscle to do?
They tell them to contract
Both neurons and muscles are what?
Both are excitable cells
Both neurons and muscles respond to stimuli by changing their what?
By changing their resting membrane potential
What is an action potential?
It is a large change in a membrane potential that spreads rapidly over long distances with a cell
What do motor neurons use as a neurotransmitter?
Acetylcholine (ACh)
What does acetylcholine do for motor neurons?
It tells the skeletal muscle to contract
Chemically gated ion channels are opened by what
They are open by chemical messengers
What do chemically gated ion channels create?
They create small local changes in membrane potential
What do voltage gated ion channels do?
They open or close and response to changes in the membrane potential
The axon of each motor, neuron branches as it enters the what?
The muscle
What does the axon form as it branches?
It forms a neuromuscular junction with a single muscle fiber
The axon terminal and muscle fiber are separated by what?
The synaptic cleft
What does the synaptic cleft separate?
The axon terminal and muscle fiber
Synaptic vesicles with the axon terminal contains what
Acetylcholine
The muscle fibers sarcolemma Has junctional folds with what?
ACh receptors
Name the sequence of events leading to contraction
A motor neuron fires, an action potential down its axonThe motor neurons axon terminal releases ACh into the synaptic cleftACH binds receptors on the junctional folds of the sarcolemmaACH binding causes a local deep polarization called an end plate potentialThe local depolarization, triggers an action potential in the Adjacent sarcolemmaThe action potential in sarcolemma travels down T tubulesSarcoplasmic reticulum releases CA +2CA +2 binds to trombone which chefs trip said to uncover the finding sites on actinMyosin heads, bind actin, and contraction occurs via Crossbridge cycling
What is excitation contraction coupling?
It is the sequence of events by which an action potential along the circle Lima leads to the sliding of myo filaments
The action potential propagates along where
The Sarcolemma and down the T tubules
The transition of the AP along the T tubules causes what?
It causes voltage sensitive to be proteins to change shape, opening CA +2 release channels in the SR
In excitation contraction coupling, calcium ions flow into what?
Into the cytosol
In excitation contraction coupling, Calcium ions bind what?
Troponin
In excitation contraction coupling Calcium ions, remove what?
Removes the blocking action Of tropomyosin
In excitation contraction coupling, Myosin binding sites on the thin filaments are exposed and ready for what?
Myosin binding
In excitation contraction coupling, Myosin binding to Actin forms what and what begins?
Forms cross, bridges, and contraction begins
What is the cross bridge cycling?
it is the series of events during which myosin heads pull thin filaments toward the center of the Sarcomere
How does the cross bridge cycling begin?
Epic begins when the energized myosin head attaches to an actin microfilament forming a cross bridge
In the cross bridge cycling ADP and PI released and then the myosin head does what?
The myosin head, pulls the actin filament toward the M line
In cross bridge cycling ATP attaches to myosin weakening what?
Weakening the link between myosin and actin and causing the myosin head to detach.
In cross bridge cycling, myosin hydrolyzes what?
ATP to ADP an PI
In cross bridge cycling, Myosin hydrolyzes Returning the myosin head to it’s What?
To its pre-stroke high energy position
The cross bridge cycling continues as long as what happens?
As long as ATP is available and CA +2 is bound to troponin
What does a motor unit consist of?
It consists of one motor neuron and all the muscle fibers it innervates
A muscle that exerts fine control have what type of motor unit?
A small motor unit
Large weight-bearing muscles have what type of motor unit
A large motor unit
A muscle twitch is the response of what?
It is the response of a muscle to a single stimulation
A muscle twitch has three phases named them
The latent period, The period of contraction, and the period of relaxation
Muscle contractions are graded in two ways describe them
An increase in the frequency of stimulation causes temporal summation, and the increase in strength of stimulation causes recruitment
In graded muscle contractions, temporal submission occurs when what happens?
When a second contraction begins before the muscle has completely relaxed
In the graded muscle contraction as the stimulation frequency increases what happens
The relaxation time between twitches becomes shorter, concentration of CA +2 in the cytosol rises, and wave summation becomes greater, progressing to unfused or incomplete tetanus
In the graded muscle contraction, muscle tension increases until what happens?
Until it reaches maximal tension
