Muscle Physiology Flashcards
what are characteristics of cardiac muscle
1 nucleus per cell
nucleus is centered
contains striations
contains actin and myosin arranged in sarcomeres
contains intercalated discs
involuntary
branched cell
Y/N
is calcium the trigger for cardiac muscle
yes
Y/N
can cardiac muscle regenerate
no
what are the characteristics of smooth muscle
1 nucleus
nucleus is centered
no striations
contains actin and myosin
involuntary
long tapered shape
plasticity
can smooth muscle regenerate
yes
is calcium the trigger for smooth muscle
yes
what are characteristics of skeletal muscle
multinucleated
nuclei on sides of cells
contains striations
contains sarcomeres
contain actin and myosin
voluntary
long cylindrical shape
can skeletal muscle regenerate
limited ability for regeneration
what is an action potential
a nerve impulse that reaches muscle and “sets off” the muscle
and electrical signal that changes the charge across a membrane
what is excitability
the ability to conduct an electrical signal
what is contractility
the ability to contract
contraction through special protein filaments in muscle that contain actin and myosin
what is elasticity
the ability to stretch and recoil
making something longer and then being able to go back to its original position
what are the functions of the muscular system
movement
posture
temperature control
how does the muscular system aid in temperature control
when we are cold, we shiver
shivering is caused by the muscles vibrating vigorously to create heat
what layers do you need to cut through before you get to skeletal muscle
skin - epidermis and dermis
hypodermis - aka superficial fascia - adipose tissue
deep fascia - dense fibrous connective tissue
what is another name for the superficial fascia
hypodermis
what is the deep fascia made of
dense fibrous connective tissue
where is skeletal muscle located relative to the skin
deep within the body
why is the hypodermis important
it provides a layer of insulation and protection
what type of tissue is found in the hypodermis
areolar tissue
T/F
deep fascia can surround an entire muscle
True
muscles connect to bone via _____________
tendons
what tissue makes up tendons
dense regular connective tissue
what is a tendon sheath
a sack of synovial fluid around a tendon to prevent friction
what is a bursa
a sack of synovial fluid that aids in preventing friction against the joints
what is an aponeurosis
a flat tendon
where can you find aponeurosis
the skull and línea alba
would an entire muscle be a
cell? tissue? organ? system?
organ
many tissues working together to perform a function
what is an epimysium
layer surrounding an entire muscle
what is the perimysium
layer surrounding a fascicle
what is a muscle fascicle
a collection of muscle fibers/muscle cells
what is the endomysium
layer that surrounds an individual muscle fiber/muscle cell
what are fibers made of
myofibrils
what are myofibrils made of
myofilaments
what are myofilaments made of
actin and myosin
what is the sarcolemma
cell membrane of a muscle cell
what is the sarcoplasm
cytoplasm of a muscle cell
what is a T-Tubule
invaginations of the sarcolemma for nerve impulses
what organelles would you find in abundance in the sarcoplasm of a muscle cell
mitochondria
what is the sarcoplasmic reticulum
the smooth ER of a muscle cell
the sarcoplasmic reticulum stores ___________ ions
calcium ions
Ca++
what is a triad
area where there is one part of the sarcoplasmic reticulum and a T Tubule and another part of a sarcoplasmic reticulum
sarcoplasmic reticulum – T-Tubule — sarcoplasmic reticulum
what are the units that make up myofibrils
myofilaments
is a myofibril larger or smaller than a muscle cell
smaller
myofilaments can be thick or thin.
what is the protein in thick filaments
myosin
myofilaments can be thick or thin.
what is/are the protein(s) in thin filaments
Actin
Tropomyosin
Tropo in
what causes striations in skeletal and cardiac muscle
the arrangement of thin and thick myofilaments
what is the A-Band
stacked thick myofilaments with some overlapping thin myofilaments
what is the I-Band
thin actin myofilaments only
what is the Z line
the area in the middle of an I band
what is the H Zone
region with only myosin filaments
T/F
a sarcomere is made of the A band and 2 1/2 I bands on either end
True
the unit of contraction in muscle is the _________
sarcomere
why is it necessary that muscle cells are made of many of these contractile units
for better contraction of the muscle
which part of myosin is called the myosin head
the bulby part
why is the myosin head important
it binds to actin to contract the muscle
what are the functions of myosin
the head has the ability to pivot
the head has the ability to break down ATP
the myosin head can bind to actin
the A-band in a sarcomere consists of _______ myofilaments and overlapping ________ myofilaments
thick (myosin)
thin (actin)
why is it significant that the myosin heads protrude from the thick myofilament
so it can bind to actin 360 degrees all around
the mysoin head will bind to actin, causing the __________ whenever it can
cross bridge
what are the 3 proteins in the thin myofilament
actin
troponin
tropomyosin
what is tropomyosin
protein that wraps as a spiral around actin to cover the actin binding sites at rest
what is troponin
protein that attaches to actin, tropomyosin and calcium
what happens when calcium binds to troponin
troponin changes its shape and releases the tropomyosin thus exposing the actin binding sits for myosin to bind to
when there is no calcium present, the __________________ covers the actin binding sites
troponin-tropomyosin complex
when calcium is present, the troponin-tropomyosin complex will slide off the actin binding sites, therefore actin and myosin can contract, causing the muscle to ___________–
shorten
what is the process of calcium binding to the troponin-tropomyosin complex
At rest troponin-tropomyosin complex covers up myosin head binding sites on actin
When calcium is released, the calcium binds to troponin
The binding of the calcium to the troponin induces a conformational (change in 3D shape) in the troponin-tropomyosin complex
Myosin binding sites are now exposed
what is the sliding filament theory
process of how muscle contracts
what is the process of the sliding filament theory
Action potential goes down the sarcolemma
Calcium releases
Calcium binds to troponin
Twisting of tropomyosin off the binding sites
When the troponin-tropomyosin complex is off the binding site, there is a space for the myosin heads to insert and do its thing
Myosin binds to actin
Myosin heads (cross bridges) ratchet causing Tightening of the bands
Sarcomere shortens
Muscle contraction
what happens to the A band during contraction
nothing it stays the same
what happens to the H band during contraction
it disappears because of the overlapping actin coming towards the center
what happens to the I band during contraction
is decreases
what happens to the Z line during contraction
they come closer to the center
how does the calcium go back into the sarcoplasmic reticulum after the action potential ends
through active transport
what happens when the myosin head binds ATP
it is released from actin and the head is recocked
T/F
ATP aids in detachment of the myosin head
true
what happens at the release of the ADP and P from the myosin head detaching
the myosin head will pivot/swivel that moves the actin towards the center of the sarcomere and shorten the muscle cell
where are the calcium ions located during muscle rest
in the sarcoplasmic reticulum
what are voltage gated channels
channels that open when there is a change in voltage across a membrane
what happens once calcium is released from the sarcoplasmic reticulum
It (calcium) binds to troponin
The binding of calcium to troponin causes tropomyosin to change position
After the change in position of they tropomyosin, the myosin binding sites are exposed to the actin
When the myosin binding sites are exposed, the myosin heads can then attach to the actin
When the myosin head attach to the actin, a contraction of the muscle occurs
the movement of the myosin head is called ___________
power stroke
if the action potential causes the calcium to be released from the sarcoplasmic reticulum, where did the initial action potential come from
a motor neuron
what is the axon terminal
the swelling at the end of a neuron
what is another name for the axon terminal
synaptic end bulb
what is the synaptic cleft
the space between the axon terminal and the motor end plate
what is the motor end plate
the portion of the sarcolemma that interacts with the synaptic cleft
where in the body does the action potential originate
from the sensory nerves in the PNS
how does the action potential “jump” over the space from the neuron to the muscle cell
through vesicles that bind to receptors that trigger a sequence of changes in charge
the binding of the __________ to the receptor will trigger the action potential in the muscle cell
neurotransmitter
what chemical is released in vesicles through the synaptic cleft by diffusion
acetylcholine
once acetylcholine binds to the motor end plate receptors, an _____________ travels down the muscle cell
action potential
what are the events that happen at the neuromuscular junction
The action potential travels down the neuron
When the action potential reaches the axon terminal, Ca ions rush into the terminal
Calcium triggers exocytosis of acetylcholine
Acetylcholine diffuses across the synaptic cleft
Acetylcholine binds to a receptor on the motor end plate
Binding of acetylcholine to the receptor causes sodium to rush into the muscle cell
Sodium has a positive charge so the charge across the membrane changes
The change in charge is propagated across the sarcolemma down the T Tubules
Acetylcholine is broken down by cholinesterase to stop the action potential
where in the axon terminal is the neurotransmitter stored
at the bulb of the axon terminal
what triggers the release of the neurotransmitter
calcium
how is the neurotransmitter released and does it require ATP
through exocytosis
Yes
how does the neurotransmitter move across the synaptic cleft
through diffusion
what is a motor unit
one neuron and all the muscle fibers it innervates
what is a small motor unit composed of
one neuron and a few specific muscle cells
where will you find small motor units
areas what require fine motor movements
fingers, eyes
what is a large motor unit composed of
one neuron and many non-specific muscle cells
where would you find large motor units
areas with general gross motor movements
for posture and muscle tone and standing
what is meant by the word “specific” in regards to motor units
individual nerves that need to communicate with individual muscle cells
if a neuron is stimulated, ______ the muscles attached to that neuron will contract
All, some, none
all
how is the amount of contraction in a muscle changed
by recruitment of motor units
more motor units will be stimulated if more contraction is needed
what is the all-or-none law
each muscle cell will contract to its maximum ability each time it is stimulated
it will be on when triggered and off when not. (similar to a basic light switch)
what is muscle tone
motor units switching on and off
in regards to muscle tone, what does hypertonic mean
an increase of muscle tone
what happens at spasticity
muscles are rigid
what occurs when there is CNS damage in regards to muscle tone
spasticity paralysis
damage to the upper motor neurons in the CNS
in regards to muscle tone, what does hypotonic mean
decreased muscle tone
what happens when muscle tone is flaccid
the muscles are limp
how is flaccid paralysis caused
when there is peripheral nerve damage
what happens in flaccid paralysis
the neuron is damaged and cannot send the action potential to the skeletal muscle cell
what is atrophy
loss of muscle myofibrils
what causes atrophy
non-use
lack of innervation
loss of myofibrils
what will happen if the atrophy is not fixed right away
the muscle fibers will be replaced with fibrous tissue - collagen - and make the process irreversible
what is hypertrophy
increased diameter due to increased myofibrils
Y/N
will there be an increase in sarcoplasmic reticulum and phosphocreatine in hypertrophy
yes
which steps in muscle contraction require ATP
detachment of myosin from actin
power stroke
active transport of calcium
Na+/K+ pump
how does the increase in intracellular calcium cause contraction
calcium ions bind to troponin-tropomyosin complex to reveal the actin binding sites for myosin to bind causing muscles to contract
why is rigor mortis not a permanent condition in cadavers
because the muscles won’t stop contracting until there is no ATP left
what is power stroke
the hydrolysis of ATP and the binding of actin causing the release of ADP and P and the swiveling of the myosin head
where is active transport of calcium happening
in the sarcoplasm taking the calcium back to the sarcoplasmic reticulum
the Na+/K+ pump moves Na+ _________ the cell
into
where does the ATP come from for muscle contraction
from anaerobic and aerobic pathways and from stored glycogen
what is an anaerobic pathway
pathway of making ATP without oxygen which results in 2 lactic acid
what is an aerobic pathway
pathway of making ATP with oxygen from cellular respiration that results in 36-38 ATP, CO2, H2O, Heat
wat is the aerobic production of ATP from glucose called
cellular respiration
where in the muscle cell does aerobic production of ATP occur
in the mitochondria of the muscle cells
explain what happens when muscles are at rest
Not much atp is needed
Myosin binding site is covered up
Excess atp will be left over
Excess atp will donate a phosphate to creatine
Creatine phosphate is formed
ATP is held in reserve for later use
what is the formula for making creatine phosphate
creatine + phosphate = creatine phosphate (aka phosphocreatine)
what is the process for anaerobic pathways
readily available ATP used first
after ready available ATP is used, the cell will start using creatine phosphate
when creatine phosphate is used up, the cell will then turn to glycogen reservoir
glycolysis will occur and create 2 pyruvic acid
no oxygen will make the pyruvic acid turn into 2 lactic acid
is the formation of lactic acid reversible
yes
lactic acid can turn back into pyruvic acid in the liver for recycling
how is glycogen stored in cells
stored in adipose tissue
what type of compound is glycogen
organic compound
what is slow oxidative muscle fiber type
muscle fiber type designed for postural maintenance and resistance to fatigueu
T/F
slow oxidative muscle fibers cannot generate ATP all the time
false
do slow oxidative fibers prefer aerobic or anaerobic
aerobic
where does the oxygen come from in regards to the slow oxidative fibers
the blood and myoglobin
what is fast glycolytic muscle fibers
muscle fibers designed for large rapid force
Y/N
do fast glycolytic fibers fatigue quickly
yes
do fast glycolytic fibers prefer anaerobic or aerobic pathways
anaerobic
what type of athlete would prefer fast glycolytic fibers
(fibers needed for rapid force)
sprinters
what type of athlete would prefer slow oxidative fibers
(fibers used for longer periods of contraction)
marathon runners - long distance runners
Y/N
do slow oxidative fibers contain a good blood supply
yes
contain a lot of capillaries
what gives muscle its red color
myoglobin
what happens if the muscle does not get enough ATP or oxygen
if not enough oxygen, the aerobic pathway will convert to anaerobic pathway
if not enough ATP, muscle contraction will decline
explain muscle fatigue
Muscle cell is going to use up the creatine phosphate and the glycogen stores that are there
After everything is used up, the muscles will try to go the aerobic route
Because the individual is not trained, the blood supply is not feeding enough oxygen
Not enough oxygen makes it go the anaerobic route
Anaerobic route will have increase of lactic acid
Lactic acid makes the cell more acidic
Too much acidic is not good so your muscles get fatigued
what is a way for you to get your muscles to have a better blood supply
exercise and training will cause muscles to have a better blood supply over time to meet needs for more movement
what is oxygen debt
not enough oxygen can be taken in to meet the needs of the muscle
what happens during oxygen debt
individual will have an increase in breathing to make up for the oxygen that was lost
what happens to the muscle cells during recovery
Oxygenation of myoglobin
Cell will get rid of lactic acid build up
Glycogen will be replenished
New creation of phosphocreatine
ATP will be readily available in the sarcoplasm again
what is the recovery period in layman’s terms
replenishing everything you used up during any type of movement
what is a muscle twitch
the response of a single motor unit to an action potential
(lasts 7-100 milliseconds)
what is a myogram
the graph of a twitch
tension vs time
what is another name for myogram
electromyogram - EMG
what are the phases distinguished in the myogram as the motor unit contracts
latent period
period of contraction
period of relaxation
refractory period
explain the latent period of motor unit contraction
contraction has not happened
it is the time between on set of stimulus and on set of the twitch
the time before the twitch happens
internal tension is here - no shortening of muscle fibers
explain the period of contraction of motor unit contraction
motor units will contract
elastic components of the muscles are taught
external tension is created to lift the load
explain the period of relaxation of motor unit contraction
the time it takes for the muscle fibers to relax
calcium is reabsorbed
explain the refractory period of motor unit contraction
the time during which the muscle fibers CANNOT be stimulated again
what is summation
incomplete tetanus
the muscle does not have enough time to relax in between twitches
what happens during summation
the force of each twitch will build on top of the previous one
Each twitch is greater than the last and there is no time for complete relaxation
what is tetanus
sustained muscle contraction
the muscle gets no breaks in between twitches
what happens during tetanus
many twitches will fuse together into a smooth prolonged contraction
tetanus and summation are influences by the availability of ____________________
calcium ions - Ca++
what is treppe
twitch where each twitch develops more tension than the one before it
what happens during treppe
sarcoplasmic reticulum doesn’t have enough time to reabsorb all the calcium ions it released so the concentration of calcium increases in the sarcoplasm
what is the all-or-none law
a muscle cell will always contract to its maximum ability at each action potential
muscle cell contraction is relative to the amount of _____________ available
intracellular calcium
if more calcium available, there will be a __________ contraction
greater
what are the similarities of tetanus, summation and treppe
all are a twitch for a certain amount of time
what are the differences of tetanus, summation and treppe
summation is a shortened version of tetanus
tetanus is a long twitch
treppe is a twitch that multiplies each time
what is isotonic contraction
a contraction where there is constant tension and the muscle shortens
what is an example of isotonic contraction
walking, running, lifting something off the desk
tension is there and the muscle shortens
what is isometric contraction
contraction where tension increases but the muscle does not shorten
tension produced does not exceed load and the muscle doesn’t shorten
give an example of isometric contraction
carrying a bad of groceries, holding head up
tension is there but the muscles don’t move
what is the formula for cellular respiration for aerobic pathways
glucose + oxygen -> carbon dioxide + 36-38 ATP + Heat + Water
C6H12O6 + O2 -> CO2 + H2O + 36-38 ATP + HEAT
what type of organelle is present in high numbers in cardiac and skeletal muscle
mitochondria
why are mitochondria important in cardiac cells
cardiac cells need a lot of ATP to keep the heart pumping
do cardiac muscles contain sarcomeres
yes
do cardiac muscle cells always have sarcomeres
yes
what type of junctions are present at an intercalated disc
gap junctions and desmosomes
why do cardiac muscle cells need gap junctions
so he muscles can communicate to beat as a unit
Y/N
can cardiac muscle cells undergo self-excitation
yes
what is the concept of self-excitation
the ability to create its own action potentials
do cardiac muscle cells have a shorter or longer contraction/refractory period than skeletal muscle?
longer
what is the significance of the long refractory periods in cardiac muscle
so that no action potential is sent right after one was just sent
T/F
cardiac muscle cells do not always need oxygen
false
why is it significant that cardiac muscle cells can use many energy sources
so that it can maintain blood flow and keep the nutrients going throughout the body
what is cardiac muscles capacity for regeneration
none
how is smooth muscle different from skeletal muscle
it is not organized in sarcomeres
how is smooth muscle similar to skeletal muscle
it contains myosin and actin myofilaments
where is smooth muscle located in the body
at the arrector pili muscle
in the GI tract
Y/N
does smooth muscle contain troponin
no
why is it significant that smooth muscle has a longer contraction time and that the contraction time begins slowly
so that the muscle and stretch and accommodate to the body
smooth muscle can stretch and then relax at its new length. this ability is called the _______________
stretch-relaxation response
what is an example of a stretch-relaxation response in smooth muscle
if you are an individual that eats a lot, your stomach will be relatively larger
if you are an individual that doesn’t eat as much, your stomach will be relatively smaller
of all 3 muscle types, __________ muscle has the greatest capacity for regeneration
smooth muscle
does every smooth muscle cell need a motor neuron
no
what is a contraction of one motor unit in response to action potential
twitch
what is the term used to describe a second contraction greater than first when the muscle cell is stimulated before complete relaxation
summation
what is the term used to describe sustained muscle contraction
tetanus
what is the term used to describe muscle contraction that becomes greater if a muscle contracts and completely relaxes several times
treppe
what type of contraction described when a muscle as a whole stays the same length in spite of cross bridges forming
isometric contraction
what occurs when acetylcholine binds to its receptor at the neuromuscular junction
Na+ influx
sodium rushes into the cell
what is the term used to describe constant tension with muscle shortening during a contraction
isotonic contraction
what is the term used to describe tension increasing and the muscle doesn’t shorten (constant length) during a contraction
isometric contraction
