test 3 Flashcards
excitation
Phase 1
- impulse travels down axon
- impulse opens calcium channels which cause calcium to enter into the terminal
- Ca2+ causes vesicles to release ACh through exocutosis into synaptic cleft
- ACh binds to the ACh receptors in sarcolemma
- channels open and Na+ enters muscle
cell
acetylcholinesterase
an enzyme that breaks down acetylcholine
muscle cells and nerve cells are…
exciteable
depolarization
inward movement of sodium-the increase of positive charge inside of the cell
repolarization
when potassium leaves the cell, going back to its rest state…going back to negative state
four steps of contraction and relaxation:
Excitation
Excitation and contraction coupling
Contraction
Relaxation
2 guards
troponin
tropomyosin
somatic means
body
motor means
movement
what does the skeletal system allow the body to do
movement, move body parts, breathing
stability, posture and joints
Heat and production
Hormone secretion and glycemic control
Heat production(thermogenesis)
skeletal muscles produce 20-30% of body heat @rest and up to 85% in exercise
Epimysium
surrounds entire muscel
perimysium
surrounds multiple muscle fibers-groups into fascicle
endomysium
surrounds each muscle fiber cell
skeletal muscles are..
voluntary, striated, alternating light and dark. usually attached to bones
muscle cell characteristics
excitability-responsiveness
contractility-shortens
extensibility-stretches
elasticity-goes backd
skeletal muscle connective muscle sheaths from external to internal
epimysium
perimysium
endomysium
fascia
sarcomere is..
the basic unit of muscle contraction…the plasma membrane of a muscle fiber that contain ACh receptors. ACh binds and opens gated channels. slat floods in and potassium goes out
What components make up a sarcomere?
M Lines- attach to myosin
Z lines-where thin filaments attach
Actin-thin line
Myosin-thick line
Where is a contraction taking place in the sarcomere
the region between the two z lines with actin and myosin filaments crossing over each other
High calcium concentration=
low calcium concentration=
High calcium-contraction
low calcium-relaxation
thick filaments of mysosin are…
hundreds of myosin proteins, they have a tail and two heads
thin filaments of actin are…
made of several G-actin proteins to form F-actin –like pearls on a string
What structures compose the Neuromuscular junction
axon, avon, branch, axon terminal, synaptic vesicle, ACh, presynaptic membrane
explain sliding filament..WHEN THE NERVOUS SYSTEM CONTRACTS..
it stimulates muscle fivers, the myosin heads on the thick filaments will interact with the binding sites on the actin subunits. The attachements will form and break several times as the thick filaments pull the thin filaments in towards the center of the sarcomere, thuspulling the Z discs toware the M line. The I Bands shorten and HZone disappears. A bands get close, the muscle shortens
Which parts of the sarcomere are moving closer together and overlapping with one another
A bands
H overlaps
What initiates a muscle contraction?
the nervous system. A nerve impulse travels down the axon and arrives at the axon terminal
what effect does calcium have on the axon terminal>
calcium causes vesicles carrying acetylcholine to move towards the axon terminal’s membrane and release acetylcholine into the synapse
acetylcholine is a neurotransmitter which…
is in synaptic vessels in the axon terminal
how is acetylcholine released? Where does it bind after it releases
through acetylcholine receptors.
it binds to the protein which makes a channel and it opens to allow Na+ to enter and Potassium to leave
what is acetylcholinesterase?
why is it important for normal muscle function
it’s an enzyme in the synaptic cleft -it breaks down acetylcholine, and the ion channel closes, preventing further muscle contraction until another nerve impulse arrives
explain the role of calcium and the calcium pump in relation to muscular contraction and relaxation
Na+channels close and K+ channels open.
what is the end result of acetylcholine
action potential is reached
ACh is released (by motor neurons)to stimulate muscle contraction
where does calcium bind to cause cross bridging
to troponin C -causing the conformational shift.
A cross bridge forms and myosin binds to a new positive actin
Motor unit
one nerve fiber and all the muscle fibers innervated by it. they behave as a functional unit
motor nerve
collection of cells called neurons
Isometric contraction
no shortening-muscle tension increases: does not exceed load (meter) stays the same–holding back and buttocks stiff without contracting during pushups
isotonic contraction
muscle shortens; muscle tension exceeds load
T(tension) doing pushups with your arms.. a tonic
muscle tension
force generated by contracting muscle load is the force placed on a muscle by an object
2 types: isometric and isotonic
twitch
single fiber , single stimulus
smallest unit of a muscle
muscle twitch is …
quick cycle of contraction and relaxation when a muscle is directly stimulated
singular twitches are not part of muscular activity
MS, traumatic brain injury
ALZheimers
what causes muscle tone
muscle tone is the maintenance of partial contraction of a muscle. it is important for generating reflexes, maintaining posture, and balance, and proper function of other organ systems
what are three ways ATP is regenerated during skeletal muscle contraction
Aerobic respiration
Anaerobic
Phosphagen or creatine phosphate
which type of pathway provides the most regeneration/energy
aerobic cellular respiration
what are possible causes of muscle fatigue
improper exercise
ling time combat
military training
diseases like cancer and stroke
longitudinal layer (smooth muscle layer)
outer layer, runs lengthwise along the body-shortens the tract
circular layer
middle layer-prevents food from traveling backward
Multiunit vs unitary smooth muscle
multiunit smooth muscle differs from single unit in that each smooth muscle cell receives its synaptic input
where are multi unit muscle located
in the airways of lungs, large arteries, and ciliary muscles of the eye
unitary are individual smooth cells that are…
couple to neighboring cells by gap junctions
slow oxidative fibers
low intensity, long duration, maintain posture, stabilize joints
long distance running , cycling
fast oxidative fibers
short intense activities, -weight lifting, sprinting
fast glycolytic
faster twitch and larger force, 400 meter run, high intensity, short duration
myofibrils
composed of thick (myosin) and thin(actin) filaments
