Muscular System Flashcards
2 prefixes that mean/refer to muscle
myo
sarco
What are the three series-elastic components of muscular tissue?
The stretchy:
- endomysium
- perimysium
- epimysium
Are the 3 series-elastic components of muscular tissue excitable?
NO but they do stretch and recoil
dont contract
In what type of pairs do voluntary muscle usually work?
Antagonistic
What happens to your muscles when you work out?
Do NOT make more fibers/muscle, you are making your fibers bigger
Do muscles expand?
NO they only contract
ex: muscle contracts to flex arm then an entirely diff. muscle contracts to bring arm back down
What is the name of the cell membrane in a muscle?
sarcolemma
Fascicle
a group of muscle fibers
Difference btwn perimysium, endomysium, and epimysium
Epimysium- surrounds whole muscle
Endomysium- wraps each individuals muscle fiber
Perimysium- surrounds each muscle fiber bundle, called fascicles
What do myofibril contain in a muscle cell?
Thin and thick filaments
What is the one neurotransmitter in skeletal muscle?
Acetylcholine
Acetylcholine
The ONLY one neurotransmitter in skeletal muscle
In which direction does a neuron nerve cell travel?
In the direction in which the axon is pointing; it’s a one way street they can’t go back the same way they came from
Where are neurotransmitters
In synaptic vesicles
How does a neuron move?
Electrical impulse forces calcium channels to come in and push synoptic vesicles to the end of the axon
From left to right, what is the anatomical structure of a neuron
dendrites, soma (body), axon (synaptic vesicles in membrane), gap/synapsis/junction, NEIGHBORING neuron
How does an electrical impulse get from one neuron to another?
Dendrites on the next cell/neuron have receptors for the neurotransmitter acetylcholine, once they receive the acetylcholine the electrical impulse starts all over again on the new neuron
Why can’t electrical impulses travel backwards?
There are no receptors on the front of the cell, only on the dendrites, and there is no acetylcholine in dendrites only receptors
Action potential
the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell
What are the only two types of cells that have action potential?
nerve cells and muscle cells
What happens when the acetylcholine goes to muscle fiber?
Goes to the synapse called neuromuscular junction and the muscle contracts
Neuromuscular junction
where neuron and muscle meet
What happens to acetylcholine after it does its job?
Acetylcholinesterase (enzyme) breaks it down then the neuron (it came from originally) picks up the broken down neurotransmitter and rebuilds it to use it again.
SSRI
Selective seratonin re-uptake inhibitor
ex: prozac, Zoloft, ect.
Sensory neurons
Going INTO the brain (Afferent)
Motor neurons
Going FROM brain to muscle (Efferent)
SAME
sensory—> afferent
motor—–> efferent
How many mitochondria do muscles have?
thousands
What does the sarcolemma consist of?
it has characteristic transverse (T) tubules which are continuous with the sarcolemma. The fibers are multi nucleic
What does the sarcoplasm contain?
Myofibrils made up of myofilaments
Abundant glycogen and myoglobin
Sarcoplasmic reticulum
Stores CALCIUM
2 terminal cisternae of the sarcoplasmic reticulum join with avT tubule to constitute a triad.
Triad
A T tubule with terminal cistern on each side
Myoglobin
attracts oxygen that will help metabolize the glucose in glycogen
What happens when electrical impulse goes into T tubule?
Causes the swollen part of the sarcoplasmic reticulum (cisternae that stores calcium) to RELEASE the calcium
Are T tubules apart of the cell membrane (sarcolemma) ?
YES
Sarcomere
basic unit of muscle contraction
Myofilaments
CENTRAL to muscle contraction; two kinds: thick and thin
Thick myofilaments
Made of MYOSIN shaped somewhat like a gold club
Thin myofilaments
Made up go fibrous (skinny protein) ACTIN with bead-like subunits of globular actin, each of which has an active site that can find with the head of a myosin molecule
Tropomyosin
Lies within the fibrous actin; protein that consists of smaller proteins troponin
Regulatory proteins
Helps to regulate/control when muscle will contract; tropomyosin and troponin
If troponin hides active sites on a actin, how does myosin grab onto the actin to cause it to contract?
The myosin (thick filaments) are already cocked back but troponin is hiding active sites on actin. However, once calcium is released form the cisternae of the sarcoplasmic reticulum, it combines with the troponin and moves it so that myosin can grab onto the actin, release its cocked position, and cause the actin to contract.
What do myofibrils contain?
Thick (myosin) and thin (actin) filaments
What is in between two z-lines in a muscle fiber?
A sarcomere (filaments)
H-band
area where actin doesn’t connect; just myosin. Kind of LIGHT
A-band
Both actin and myosin are there so it’s therefore DARK on the ends
I-band
ONLY actin on the ends of each sarcomere; very LIGHT
Skeletal muscle is innervated by…
somatic motor neurons
Each muscle fiber is supplied by how many motor nerve fibers?
Only ONE
Motor unit
one nerve fiber and all the muscle fibers it interacted (one nerve can affect three different muscle cells for ex)
Does a motor unit behave as a single unit?
Yes it behaves as a single unit and contracts as one (contracts at same time)
What’s the size of a motor unit?
They vary in size
Which has more FINE control: eye (23 muscles fibers/motor unit) or the thigh (500-1,000 muscle fibers/motor unit)?
The eye
What happens when there are multiple more units within a muscle?
They are able to work “in shifts”
When you flex a little, does that mean your muscles aren’t fully contracting?
No it means that only SOME muscle fibers are contracting; fewer motor units. Muscle fibers either contract 100% or they doth contract at all.
Why do you flex harder when you are picking up heavier things? What is happening?
When you flex harder to pick up more, more minuscule fibers are contracting
Synapse
Contact point between a neuron and its target cell (either a muscle or another neuron)
What is the synapse called when the target cell of a neuron is a muscle cell?
Neuromuscular junction
Neuromuscular junction
The synapse when the target cell of a neuron is a muscle cell
Synaptic knob
The neurons expand into this at the neuromuscular junction
Motor end plate
Area on a muscle cell where muscle cell receives the neuronal message (has receptors)
Synaptic cleft
A tiny gap between two cells
What happens as a nervous impulse travels down the neuron?
It triggers the release of a neurotransmitter (always acetylcholine/ACh) from synaptic vesicles in the synaptic knob
Where are ACh receptors located?
In the motor end plate within infoldings called junctional folds.
What shows voltage changes after stimulation of muscle fibers and neurons (which are electrically excitable)?
Plasma membranes
Electrophysiology
The study of the electrical activity in cells; how electricity functions in our bodies
Electric potential
(In volts) the potential energy that results from a polarized state
RMP
Resting membrane potential- electricity not going through cell
Can a cell be polarized and exhibit a RMP?
Yes
What is RMP measured in and what is it determined by
mV and it’s determined by:
- diffusion of ions down their concentration gradients
- selective permeability of the plasma membrane
- electrostatic attraction
Is the electricity (charge) the same on the inside and the outside of a cell?
No they’re different even in resting state therefore, it’s considered polarized and to have a potential
What kind of pump is in the cell membrane of all cells?
Na+K+ATPase pump
What does the Na+K+ATPase pump do?
It pumps Na+ out of the cell because it doesn’t want the cell to flood (water follows Na+) and it pumps K+ back in. Potassium is usually high inside the cell, Na+ is usually high outside of the cell, they both want to diffuse high—> low. ATPase is present because the pump uses a lot of energy.
Is there usually a higher concentration of Na+ inside or outside the cell?
outside
Is there usually a higher concentration of K+ inside or outside the cell?
inside
How often does the sodium-potassium pump work?
24/7
Na+ in relation to water
Where sodium goes, water follows
Normally, how is the RMP maintained?
By the sodium-potassium pump, which removes 3 sodium ions from the cell for every two potassium ions it brings in and therefore has the net effect of contributing to the negative intracellular charge.
Is inside the cell usually more neg. or positive?
Slightly more negative
Ratio of sodium to potassium after the workings of the pump?
3:2
What happens during depolarization?
The Na+ is rushing back into the cell (electrical current) from the pump, but a little too much goes back causing the cells to become slightly positive for a second
Hyperpolarization
Little too much Na+ goes back into cell leaving it slightly positive
When do we use ATP with muscle contraction?
When myosin sets up in cocked position BEFORE the muscle contracts
Review slide 23
muscular contraction and relaxation
What happens to action potentials in the nerve fiber during excitation?
Action potentials in the nerve fiber give rise to action potentials in the muscle fiber
What happens to action potentials in the synaptic knob during excitation?
They trigger the release of ACh from synaptic vesicles. ACh is released to the synaptic cleft; detected by the fated ion channels in the motor end plate
What happens when sodium ions rush into the muscle cell?
It quickly reverses polarity for a section of its cell memrane. as potassium ions rush out of the membrane, polarity is reestablished.
End-plate potential (EPP)
rapid change in polarity at the motor end plate
What does the EPP trigger?
The opening of sodium and potassium channels adjacent to the motor end plate-action potentials radiate from the plate in all directions
Where does the wave of action potential go after the EPP triggers the opening of Na+ and K+ channels?
It reaches T-tubules and terminal cisternae of the sarcoplasmic reticulum causing it to release calcium
During excitation-contraction coupling, what leads to activation of the myofilaments?
Action potentials in the muscle fiber
What happens after the action potential reached the sarcoplasmic reticulum?
It release a flood of calcium ions into the cytosol (cytoplasm/sarcoplasm)
What happens after calcium ions are released into the sarcoplasm?
Calcium ins bind to the troponin C of the thin myofilaments, causing the troponin-tropomyosin complex to shift aside, exposing the active sites on the actin filaments
What happens when troponin-tropomyosin complex shift aside?
The active sites on the actin filaments are exposed and the heads of myosin filaments can now bind to these active sites and initiate contraction.
Where is ATPase built into
The head of a myosin molecule of muscle
What causes the muscle fiber to shorten in contraction?
The sliding of the thin myofilaments (actin) past the thick ones
Does myosin shorten in contraction?
No it doesn’t shorten, only actin does
The Sliding Filament Theory
Suggests that thin filaments slide over thick ones, causing sarcomeres to shorten
What happens to myosin in preparation for actin?
The myosin binds and hydrolyses an ATP molecule, and is now in the cocked position
What does the head of each myosin molecule contain?
Myosin ATPase that release energy from ATP
What happens when the myosin head connects with the active sites on actin?
Power stroke- the time period when cocked myosin releases and actin shortens
What happens at the end of a power stroke of myosin?
Myosin binds to a new ATP, releases the actin, and returns to its original position in a recovery stroke.
Does actin slip back into its original position after a power stroke?
No because many myosin heads pull on the actin at all times
How many times is the cycle of power stoke and recovery repeated during muscle contraction?
MANY times
What zone gets smaller as actin shorten and muscle contracts?
The H zone
Limited state of contraction
Muscles are always in a limited state of contraction even when at rest
Length-tonus relationship
Muscle fibers exhibit this; the tension generated by contraction depends on how stretched (realized) or contracted the fiber was to begin with
Weak contraction
Occurs if the muscle is already mostly contracted
What happens if the muscle is overly stretched?
Little overlap exists between actin and myosin filaments, and contraction can damage the muscle
What happens when nervous stimulation ceases?
The muscle relaxes
Acetylcholinesterase
Breaks down ACh so the muscle stops generating its action potentials (stops dead in its track; can’t have contractions)
What happens to calcium during relaxation?
It’s carried back to the sarcoplasmic reticulum by active transport and a protein
