201 Study Guide 3
Muscle
Describe the basic functions and special characteristics of muscle.
Function: Move stuff, helps maintain posture, has some role in thermoregulation (shivering is
contraction of muscle and warms you up)
Primary function is movement. Movement of skeletal muscle pulling on bone, movement of skeletal
muscle to move babies out of uterus, movement of cardiac muscle that is pumping blood to your body
Special characteristics: Extensible, contractile,
Distinguish epimysium, perimysium, and endomysium.
Epi: Around the muscle
Peri: Around the fascicle
Endo: Around the fibers
Define a motor unit, sarcomere, sarcolemma, t-tubule and sarcoplasmic reticulum.
Motor unit: Several muscle cells innervated by a single motor neuron
o One motor neurons and all the muscle fibers or cells it innervates
Sarcomere:
Sarcolemma:
T-Tubule:
Sarcoplasmic Reticulum:
Describe the structure of a muscle using the terms muscle, fascicle, and muscle fiber.
Muscle:
Fascicle:
Muscle Fiber:
Briefly describe the role of myosin, actin, troponin, and tropomyosin in contraction.
Myosin:
Actin: Troponin:
Tropomyosin:
Describe the events responsible for the stimulation and eventual contraction of a muscle cell, including
neurotransmitters, gated channels, ions used, and the role of t-tubules, the sarcoplasmic reticulum, and calcium
in enabling muscle contraction.
An action potential comes down a motor neuron and that motor neuron has an influx of Ca that causes
the release of neurotransmitter (Ach) that activates chemically gated Na channels on the sarcolemma
(cell membrane of muscle cell). If you open enough of the channels, then you will cause the voltage
gated Na channels to open that send an action potential down the sarcolemma (cell membrane of
myocyte). The t-tubules are continuous with the sarcolemma and carry that electrical charge as well. As
the electrical charge moves down the t-tubules, it causes the release of Ca from the terminal systerns of
the SR (sarcoplasmic reticulum). Ca binds troponin and troponin moves tropomyosin out of the way
because tropomyosin blocks the binding sites on actin for myosin. Once tropomyosin is moved out of
the way, myosin can bind to actin and with the use of 1 ATP molecule, for every round, it will attach
pull, attach, pull, attach, pull over and over causing myosin and actin to slide past one another and every
sarcomere which means that the muscle is contracting.
Briefly describe the cross bridge cycle.
Myosin heads binding, pulling, and detaching on actin and for every round of that, every head uses a
molecule of ATP.
Define/ distinguish muscle twitch, wave summation, incomplete tetanus, complete tetanus, threshold stimulus,
maximum stimulus, recruitment (motor unit summation), and the size principle.
Twitch: Muscle cell briefly twitching in response to a single action potential
o Twitches on eyelid
Wave Summation:
Muscle
Describe the basic functions and special characteristics of muscle.
Function: Move stuff, helps maintain posture, has some role in thermoregulation (shivering is
contraction of muscle and warms you up)
Primary function is movement. Movement of skeletal muscle pulling on bone, movement of skeletal
muscle to move babies out of uterus, movement of cardiac muscle that is pumping blood to your body
Special characteristics: Extensible, contractile,
Distinguish epimysium, perimysium, and endomysium.
Epi: Around the muscle
Peri: Around the fascicle
Endo: Around the fibers
Define a motor unit, sarcomere, sarcolemma, t-tubule and sarcoplasmic reticulum.
Motor unit: Several muscle cells innervated by a single motor neuron
o One motor neurons and all the muscle fibers or cells it innervates
Sarcomere:
Sarcolemma:
T-Tubule:
Sarcoplasmic Reticulum:
Describe the structure of a muscle using the terms muscle, fascicle, and muscle fiber.
Muscle:
Fascicle:
Muscle Fiber:
Briefly describe the role of myosin, actin, troponin, and tropomyosin in contraction.
Myosin:
Actin: Troponin:
Tropomyosin:
Describe the events responsible for the stimulation and eventual contraction of a muscle cell, including
neurotransmitters, gated channels, ions used, and the role of t-tubules, the sarcoplasmic reticulum, and calcium
in enabling muscle contraction.
An action potential comes down a motor neuron and that motor neuron has an influx of Ca that causes
the release of neurotransmitter (Ach) that activates chemically gated Na channels on the sarcolemma
(cell membrane of muscle cell). If you open enough of the channels, then you will cause the voltage
gated Na channels to open that send an action potential down the sarcolemma (cell membrane of
myocyte). The t-tubules are continuous with the sarcolemma and carry that electrical charge as well. As
the electrical charge moves down the t-tubules, it causes the release of Ca from the terminal systerns of
the SR (sarcoplasmic reticulum). Ca binds troponin and troponin moves tropomyosin out of the way
because tropomyosin blocks the binding sites on actin for myosin. Once tropomyosin is moved out of
the way, myosin can bind to actin and with the use of 1 ATP molecule, for every round, it will attach
pull, attach, pull, attach, pull over and over causing myosin and actin to slide past one another and every
sarcomere which means that the muscle is contracting.
Briefly describe the cross bridge cycle.
Myosin heads binding, pulling, and detaching on actin and for every round of that, every head uses a
molecule of ATP.
Define/ distinguish muscle twitch, wave summation, incomplete tetanus, complete tetanus, threshold stimulus,
maximum stimulus, recruitment (motor unit summation), and the size principle.
Twitch: Muscle cell briefly twitching in response to a single action potential
o Twitches on eyelid
Wave Summation:
