Chapter 12: Muscle Physiology

*on exam 3

generate force and motion

generate force and motion

Overall functions of muscle

generation of heat for thermal regulation

extra function of skeletal muscle

cardiac, smooth, skeletal

What are the 3 different types of muscle tissue?

skeletal

striated, voluntary muscle

cardiac

striated, involuntary muscle

smooth

nonstriated, involuntary muscle

motor neurons

what controls skeletal muscle?

intrinsic, hormonal and autonomic control

what controls cardiac and smooth muscles?

position and move the skeleton

main function of skeletal muscle

tendon

collagen attachment of muscle to bone

origin

attachment point closer to midline/trunk or more stationary bone

insertion

distal attachment of muscle to bone

bone

what structure does skeletal muscle attach to?

flexor miuscles

move bones closer together

extensor muscles

move bones away from each other

ATP

what is required to generate muscle contraction?

load

weight that opposes force

force, contraction

Muscles generate ________ by _________

muscle fibers or myofibers

name for muscle cells

sacroplasm

skeletal muscle cytoplasm

satellite cells

muscle stem cells

long and multinucleated

structure of a skeletal muscle cell

fascicles

collections of muscle fibers surrounded by connective tissue

Sarcolemma

skeletal muscle cell membrane

myofibrils

major intracellular structures; long, parallel contractile structures

myofibrils, glycogen granules, mitochondria

structures found inside a skeletal muscle fiber

sarcoplasmic reticulum

modified ER found in skeletal muscle cells ,longitudinal tubules that wraps each myofibril

terminal cisternae

ends of sarcoplasmic reticulum; Concentrates calcium with at Ca2+ ATPase

transverse “t” tubules

-functions to carry AP throughout entire muscle;

-lumen is continuous with ECF

2 terminal cisternae and a t tubule

what makes up a triad in a skeletal muscle cell?

1000

about how many myofibrils are found in each muscle fiber?

sarcomere

proteins within the myofibrils that form functional contractile units

a series of interactions between muscle proteins

what causes muscle contraction?

myosin

thick filament, grabs and pulls, motor protein with head neck and tail regions

actin

thin filament, structural rods

tropomyosin

blocks actin binding site, cannot have contraction when in place

troponin

calcium binds, controls tropomyosin

head

myosin motor domain that binds ATP, can bind actin

crossbridge

formed when myosin head binds to actin

titan and nebulin

-Elastic proteins, helps stabilize position of actin and myosin
-Elastic properties return stretched muscle to resting length

alternating light and dark bands

what does the sarcomere look like under microscope?

I band

Sarcomere region with only thin filaments

A band

Sarcomere region thick and thin filaments overlap

Z disk

found in center of I band, protein attachment sites for actin

H zone

found in center of A band, only thick filaments present

m line

center of sarcomere: center proteins, attachment for thick filament (myosin)

NMJ

where does signaling for muscle contraciton start?

synaptic vesicles

membrane bound vesicles that contain neurotransmitters

increased Na+ inside cell

what causes electrical signal in muscles

t-tubule

what brings action potential into core of muscle?

excitation contraction coupling

Refers to the relationship b/w AP generation in muscle, increased intracellular
calcium levels, and initiation of contraction-relaxation cycle in sarcomere

I band

what band of the sarcomere shortens in contraction?

sliding filament theory

describes actin and myosin sliding by each othe

Ca2+

what ion does AP release from the SR?

DHP and Ryanodine receptor

2 proteins involved in calcium release

Rigor state

Contractile cycle state where myosin head is bound to actin, not ATP

Resting State

Contractile cycle state where myosin (Myosin ATPase) hydrolyzes ATP → ADP + Pi; prevents full binding between actin/myosin

Ca2+ influx

what begins a power stroke?

the M line

in a power stroke….. myosin moves actin toward _________

myosin releases ADP and goes back to rigor state

what happens after a power stroke?

muscle “twitch”

single contraction and relaxation phase

Myosin, Ca2+, and Na-K ATPase

types of ATP needed by skeletal muscle

glycolysis/oxidative phosphorylation, phosphocreatine

what processes are skeletal muscle ATP sources

fatigue

muscles not able to generate expected power output

central fatigue

fatigue w/ CNS origins, subjective feelings, psychological basis

peripheral fatigue

fatigue anywhere b/w NMJ and contraction process

no

do all muscle fiber types fatigue at the same rate?

contraction speed and fatigue resistance

how can muscle fibers be classified?

Slow twitch (type I)

Muscle type used for posture
-Oxidative

-Endurance

Fast twitch oxidative (Type IIA)

-Faster movements; fatigue resistant
-Oxidative

Fast twitch (type IIB)

-Fastest, fatigable

-Glycolytic (anaerobic)

-high intensity for short duration

the # of crossbridges that form

Length-tension relationship: tension generated by muscle is directly proportional to ____________

intermediate level

what filament overlap allows for maximal sarcomere tension in muscles?

increasing AP frequency

how do you increase the force for a muscle

summation

increases force of muscle beyond a simple twitch

contraction

is a muscle AP or muscle contraction longer?

tetanus

maximal contraction of muscle

motor unit

single motor neuron and all of the individual muscle fibers that it innervates

fine motor

what type of motor unit has a greater level of control

gross motor

many fibers innervated by individual neurons

fine motor

only a few muscle fibers innervated by a neuron

the same

Each motor neuron innervates _______ type of muscle fiber

recruitment

activation of Motor Unit, resulting in contraction

slow twitch, fast twitch type IIA, fast twitch type IIB

order of recruitment

neurons have lowest threshold

why are slow twitch muscle recruited first?

isotonic

muscle contraction creates force to move loads

Concentric

shortening contractions to move load

eccentric contraction

lengthening contractions

blood vessels, digestive tract, urinary tract, airways, uterus

where are some locations that smooth muscle is found?

phasic

cyclical contraction and relaxation

tonic

contraction pattern that is always under some level of contraction, stimulus causes slight relaxation

more

Smooth muscle is _____ variable than skeletal muscle

actin and myosin crossbridges, sliding filaments, calcium concentrations regulate contraction

similarities between smooth and skeletal muscle

no

are smooth muscle layers parallel?

actin and myosin organization, more stretch, layers not parallel

differences between smooth and skeletal muscle

slowly

smooth muscle contracts and relax more ________ than the other muscle types

less, less

smooth muscle uses _______- ATP which results in ______ fatigue

no

does smooth muscle have motor endplates?

varicosities

in smooth muscle, stimulation is at these various points which trigger local contraction

MLC kinase

Muscle contraction ends by phosphorylation of myosin light chain by _________