muscle physiology

Only skeletal muscles

the muscles that the muscular system includes

1movement of the skeleton

2posture and body position

3supports soft tissues

4guards enterence/exit

5maintains body temp

functions of the skeletal muscles

muscle fibers

muscle cells are also called

epimysium

__ layer of muscle separates muscle from surrounding tissues

perimysium

__ layer of muscle surrounds muscle fiber bundles (fascicles)

endomysium

__ layer of muscle surrounds individual muscle cells (muscle fibers)

sarcomere

what is the smallest contractile unit of muscle

tendon (bundle of muscle)

aponeurosis (sheet/ broad flat tendon))

endomysium, perimysium, and epimysium come together to form a __(bundle of muscle) or __ (sheet/ broad flat tendon)

nevers of CNS

skeletal muscles are controlled by

1supply large amounts of O2 and nutrients

2carry away waste

functions of blood vessels in muscles

more muscle fibers you need

the finer your movement is the

sarcolemma

__ is the cell membrane of a muscle fiber (cell)

sarcolemma

__ surrounds the sarcoplasm (cytoplasm of muscle fiber)

transmembrane potential

in sarcolemma, a change in __ begins contraction

Transverse tubules (T tubules)

__ transmit action potential through cell

Transverse tubules (T tubules)

__ allow entire muscle fiber to contract simultaneously

Transverse tubules (T tubules)

__ have the same properties as sarcolemma

myofibrils

subdivisions within muscle fiber

myofibrils

made up of protein filaments called myofilaments

myofilaments

__ are responsible for muscle contraction

actin

thin filament is made of protein

myosin

thick filament is made of protein

sarcoplasmic reticulum (SR)

__ is a membranous structure surrounding each myofibril

sarcoplasmic reticulum (SR)

__ helps transmit action potential to myofibril

sarcoplasmic reticulum (SR)

forms chambers (terminal cisternae) attached to T tubules

formed by 1 T tubule and 2 terminal cisternae

how a triad is formed

in terminal cisternae via ion pumps

where is the Ca+ stored in the SE

sarcomeres

terminal cisternae release Ca+ into __ to begin muscle contraction

active transport

Ca+ from cytosole come into cisternae via

myofibril

__ are bundles of contractile protein

sarcomeres

__ are the contractile units of muscle

sarcomeres

__ are the structural units of myofibrils

sarcomeres

__ form visible patterns within myofibrils

repeating units of sarcomeres, or alternating dark, thick filaments (A bands) and ligt, thin filaments (I bands)

__ give muscle its striations

I bands

__ bands are in thin filaments

A bands

__ bands are in thick filaments

H band

__ band, is the area around the M line, and has thick filaments but no thin filaments

zone of overlap

__ is the densest, darkest area in the light micrograph, where thick and thin filaments overlap

M line

__ are the anchoring protein filaments for myosin

H band

__ band, is where only myosin will narrow as actin slides during cantraction

I band

__ band, actin only and shortens as muscle contractions form A band to A band

zones of overlap

transverse tubules encircle the sarcomere near ___

F-actin (filamentous actin)

__ is two twisted rows of globular G-actin

tropomyosin

__ prevents actin-myosin interaction

tropomyosin

__ blocks active sites on myosin

troponin

__ is controlled by Ca+

twisted myosin subunits..

-Head: made of 2 globular protein subunits, reach nearest thin filament

-Tail: binds to other myosin molecules

what thick filaments contain

F-actin, tropomyosin and troponin

what thin filaments contain

troponin

troponin-tropomyosin complex

F-actin

Ca+ binds to receptor on __ molecule, ___ complex changes and exposes active site of __

1. thin filamentsslide toward M lin, alongside thick filaments

2. width of A zone remains the same

3. Z lines move closer together

sliding filament theory

acetylcholine (Ach)

synaptic cleft

Action potential travels along nerve axon and ends at synaptic terminal, releasing neurotransmitter ___, into ___ (a gap between synaptic terminal and motor end plate)

acetylcholine (Ach)

__ transmits from terminus axon to membrane of muscle

junction

__ is the axon terminus and motor end plate

synapse

__ is the space btw axon terminus and motor end plate

1. arrival of an action potential at synaptic terminal

2. vesicle containing Ach in synaptic terminal fuse with neural membrane and dump contents into synaptic cleft

3. binding of Ach to receptors increases the membrane permeability of Na+ ions, Na+ then rushes into cell

4. an action potential spreads across the surface of the sarcolemma, AchE breaks down Ach

...if another action potential arrives at NMJ cycle begins at step 1

4 steps for the neuromuscular junction delivering Ach

ligand (chemically) gated channel, neurotrans: Ach

NMJ (neuromuscular junction) is triggered by

acetic acid and choline (choline is reabsorbed)

Ach is broken down by AchE into __ and __

1. exposure of active sites (Ca+ binds to toponin)

2. formation of cross-bridges (myosin head of globular is exposed and grabs)

3. pivoting of myosin heads (powerstroke releases ADP and Pi from head)

4. detachment of cross-bridges (binding of new ATP triggers detachment)

5. reactivation of myosin (ATP is broken down to ADP and Pi and is in high energy form)

5 steps of the contraction cycle

exposure of active sites

step of contraction cycle when Ca+ binds to toponin

formation of cross-bridges

step of contraction cycle when myosin head of globular is exposed and grabs

pivoting of myosin heads

step of contraction cycle when powerstroke releases ADP and Pi from head

detachment of cross-bridges

step of contraction cycle when binding of new ATP triggers detachment

reactivation of myosin

step of contraction cycle when ATP is broken down to ADP and Pi and is in high energy form

cross-bridge detachement

step of contraction cycle when in low energy form

1. Ca+ concentrations decrease

2. Ca+ detaches from troponin

3. active sites are re-covered by tropomyosin

3 things that occur during relaxation, in contraction cycle

as a whole, a muscle fiber is either contracted or relaxed

the all or none principle refers to:

1. number of pivoting cross-bridges

2. the fibers resting length at the time of stimulation

3. frequency of stimulation

tension of a single muscle fiber depends on 3 things

a twitch that lasts 7-100 msec

(isolated stimulation to a muscle fiber)

a single neural stimulation produces

requires many repeated stimuli

sustained muscular contraction

latent before contraction, contraction, relaxation

3 phases of a twitch

latent period before contraction

__ phase of a twitch, the action potential moves through sarcolemma causing Ca+ release

contraction

__ phase of a twitch, Ca+ ions build, tension builds to peak, sarcomere is shortening

relaxation

__ phase of a twitch, Ca+ levels fall, active sites are covered, tension falls to resting levels

btw contraction and relaxation phases

max tension development or peak of tension is btw __ and __ phase of twitch

wave summation

__ happends when you dont give enough time for muscles to relax

wave summation

__ is increasing tension or summation of twitches

wave summation

__ is repeated stimulations before the end of the relaxation phase: causing increseing tension or summation of twitches

incomplete tetanus

__ when twitches reach maximum tension

incomplete tetanus

__ is when rapid stimulation continues and muscle is not allowed to relax, twitches reach maximum level of tension

complete tetanus

__ is when stimulation frequency is high enough, muscle never begins to relax, and is in continuous contraction, cant do this for long periods of time bc you run out of ATP

motor unit is controled by one motor neuron

what control motor units

slowly increasing the size or number of motor units stimulated this is called recruitment (or multiple motor unit summation)

In a whole muscle or group of muscles, smooth motion and increasing tension are produced by__ and this is called __

all motor units reach tetanus (this can only be sustained for short periods of time)

max tension is achieved when

muscle tone

__ is the normal tension and firmness of a muscle at rest

muscle tone

__ is when muscle units actively maintain body position, without motion

muscle tone

__ is when increasing muscle tone increases metabolic energy used, even at rest

isotonic

__ contraction is when skeletal muscle changes length resulting in motion

isometric

__ contraction is when skeletal muscle develops tension but is prevented from changing length

shortens (concentric contraction)

In isotonic contraction, when tension > load(resistance) muscle

lengthens (eccentric contraction)

In isotonic contraction, when tension < load (resistance) muscle

elastic forces, opposing muscle contractions, and gravity

3 effects after muscle elongation following contraction

elastic forces

__ effect after muscle elongation following contraction, pulls tendons and ligaments

elastic forces

__ effect after muscle elongation following contraction, expands the sarcomeres to resting length

opposing muscle contractions

__ effect after muscle elongation following contraction, reverse the direction of the original motion

opposing muscle contractions

__ effect after muscle elongation following contraction, are the work of opposing skeletal muscle pairs

gravity

__ effect after muscle elongation following contraction, can take the place of opposing muscle contraction to return a muscle to its resting state

t

t/f: muscle store enough energy to start contraction

t

t/f: muscle fibers must make more ATP as needed

creatine phosphate (CP)

__ it the storage molecule for excess ATP energy in resting muscle

CPK- creatine phosphokinase

energy recharges ADP to ATP via __ enzyme