chapter 12 Flashcards
what is a muscle fiber, sarcolemma, sarcoplasmic reticulum, myofibrils, and t-tubules
muscle fiber- muscle cell
sarcolemma- plasma membrane of muscle cell
sarcoplasmic reticulum- tons of calcium inside, smooth ER
myofibrils- bundles of conractile proteins
t-tubules- inward extensions of sarcolemma, takes action potentail deep into cell
whats thin and thick filaments
Actin- thin
myosin- thick filament
what is the Z lines, M line, A band, H zone, I band
Z lines- thin filaments only (gets pulled closer together)
M line- thick filaments only
A band- full length of myosin (stays the same)
H zone- only myosin (gets shorter when contracting)
I band- end of myosin to end of other myosin (thin filaments) (gets shorter during contraction)
whats the cross bridge
when actin and myosin are attached
what is the purpose of Tropomyosin and Troponin
Tropomyosin- long filament that covers binding site when its not contrating
Troponin- globular protein that when calcium binds to it it pulls tropomyosin so myosin can bind
what is titin
elastic fiber that hold myosin to the m-line
whats the Sliding filament model
actin and myosin don’t change length but they overlap each other
whats the Cross-bridge cycle
like rowing a boat, pull relase pull relase
Myosin grabs actin and pulls actin toward center of sarcomere
what does ATP do in the cross bridge cycle
ATP provides energy to detach myosin head and cock it back to original shape
Process repeats
what are the Excitation-contraction coupling steps for skeletal muscle
- Depolarization of sarcolemma (caused by Ach binding to receptors)
- Depolarization of T-tubule
- DHP receptors in membrane respond to voltage change and changes shape – ( connect SR and T-tubule ) connected to ryanodine receptors (when DHP cahnges shape it opens the eyanodine receptors (Ca2+channels in SR membrane)
- Release of calcium from sarcoplasmic reticulum
- Calcium binds to troponin which moves tropomyosin away from the binding sites
- Cross bridge cycle
whats the difference between Isometric and Isotonic Twitches
Isometric: No change in muscle length, tension without movement. the load doesn’t moves
Isotonic: Muscle length changes (either shortening or lengthening) while tension remains relatively constant. the load moves
what is summation
summation is when signal is combined and muscle has no time to relax
whats tetanus
tetanus is when signals are sent right after each other so the muscle stays contracted
what does diameter have to do with force
- the bigger the diameter the more fibers you have so you will have more force
what is the difference between fiber length and optical length
- fiber length- length while muscle is relaxed
- optical length- where actin and myosin have optial overlap so it can have the most tension
what are motor units
one motor neruon and all the muscle fibers it controls
what is recruitment
adding more motor units for more force
what are 3 skeletal muscle types and what are they used for
Slow oxidative (uses oxidative phosporlaytion)
- contracts slow but stays contracted for longer
Fast oxidative (uses oxidative phosporlaytion)
- contract fast, but for a short time but longer than Fast glycolytic
Fast glycolytic
- contract really fast, but for a short time
what are Muscle spindles and Golgi tendon organs
Muscle spindles
- wrap around specialized fibers, both help your brain know the position of your limbs, both mechancal receptors
Golgi tendon organs
- in tendons, same as muscle spindles but for tendons
when do muscle spindles send action potentials and send no action potentials
if muscle is stretched out it will send lots of action potentials, relaxed is some, contracted is no action potentials
whats the difference between skeletal muscle and smooth muscle in contraction
no sarcomere, has actin and myosin, actin and myosin cross, pull in diagonal, when it contacts it gets short and fat
what are the steps for Excitation-contraction coupling for smooth muscle
- Depolarization of cell membrane (signal arrives via autonomic neuron or gap junction).
- Voltage-gated calcium channels in plasma membrane respond to depolarization. Calcium enters the cytosol from outside the cell.
- Calcium entering causes opening of calcium channels in endoplasmic reticulum. This is called calcium induced calcium release since influx of calcium triggers release of calcium from ER.
- Calcium rushing out of ER binds to calmodulin.
- The calcium/calmodulin complex activates myosin light chain kinase (MLCK).
- MLCK phosphorylates myosin crossbridges.
- Crossbridge cycling (only when myosin is phosphorylated).
what will stop a contraction in smooth muscle
Stopping contraction requires phosphatase enzymes to dephosphorylate myosin.
whats the difference between Single-unit smooth muscle and Multi-unit smooth muscle
Single-unit smooth muscle- autonomic neuron varicosity is on the surface and cells are connected by gap junctions so when one cell depolarizes every cell depolarizes
Multi-unit smooth muscle- autonomic neuron varicosity is in between smooth muscle cells
whats pacemaker activity
contacts on certain time (every 7 minutes)
what is smooth muscle triggered by
smooth muscle can be triggered by nuerotransmitter or gap junctions
