Skeletal and Smooth Muscle

Question 1

the properties of muscles are: 
contractilily 
excitability
extensibility
elasticity
what do these mean

Answer 1

contractility-ability of a muscle to shorten w/ force
excitability-capacity of muscle to respond to stimulus
extensibility-muscle can be stretched to its normal resting length and beyond, to a limited degree
elasticity-ability of muscle to recoil to original resting length after stretched

Question 2

skeletal, smooth, cardiac muscle
how many nuclei? wehre is it located?
involuntary/volunatry?

Answer 2

skeletal-multiple nuclei peripherally located, voluntary and involunatry (refelx only)
smooth-single nucleus centrally located, involuntary, gap junctions in vesceral smooth muscle
cardiac-single nucleus centrally located, involuntary, intercalated discs

Question 3

what is one of the most important roles of CT

Answer 3

to mechanically transmit the forces generated by contracting muscle cells to the bones to which they are attached

Question 4

where to collagen fibers in tendons insert themselves

Answer 4

into complex infoldings of the sarcolemma of the muscle fibers

Question 5

what do muscle fibers or cells develop from? how long?

Answer 5

myoblasts

100 microns x up to 30cm long

Question 6

what are satellite cells

Answer 6

stem cells under basement membrane

Question 7

what is a myofibril

Answer 7

cylindrical, filamentous, bundles that consist of an end to end chainlike arrangement of sarcomeres

Question 8

what is a triad

Answer 8

1 on each side of T tubule at AI junction of skeletal muscle
-how Ca activates muscle contraction

Question 9

what is the sarcoplasmic reticulum

Answer 9

smooth ER in muscle, surround myofibril

Question 10

what are T tubules

Answer 10

deep invaginations of the sarcolemma

-uniform contraction of cells

Question 11

in myofibril striations, what are the darker bands
what are the lighter bands?
which decompose light

Answer 11

A bands (anisotropic-decompose light into 2 rays in polarized light)
I bands (isotropic, dont alter polarized light)

Question 12

what is a sarcomere

Answer 12

z line to z line

unit of muscle contraction

Question 13

what is titan

Answer 13

protein, coiled at rest, prevent overstretching,

• heavy, largest protein known (MW 3~10^6)
• binds z line to m line
• spans half the length of a sarcomere
• acts as a framework that lines up the myosin and actin filaments and makes the contractility machinery of the sarcomere work

Question 14

what is the z line

what is the m line

Answer 14

• point of attachment of actin filaments

- group of myosin filaments, point of achoring myosin

Question 15

what does alpha actin do

Answer 15

anchors actin to z line

Question 16

where does dystrophin reside

Answer 16

just inside the sarcolemma

Question 17

connectin and titan are what?

Answer 17

synonymous

Question 18

actin myofilaments slide over myosin to shorten what?
what do not change lengths?
what is responsible for skeletal muscle contraction
when do sarcomeres lengthen?
sarcomers are in _____ so contractile force is additive

Answer 18

sarcomeres
actin and myosin
shortening sarcomeres
relaxation
series

Question 19

which bands narrow during contraction

which band is unchanged

Answer 19

H and I

A band

Question 20

what are thick filaments composed of

what are thin filaments composed of

Answer 20

myosin

actin (mainly), troponin, and tropomyosin

Question 21

what are the 2 associated light chains myosin heads have

what are 2 important binding sites on head

Answer 21

essential and regulatory

actin-binding and atp-binding

Question 22

what are tropomyosin and troponin complex associated w/?

waht does it regulate

Answer 22

F-actin

regulates contraction in response to calcium

Question 23

thin filaments are 2 entrwined strands of waht

Answer 23

macromolecular subunits of G-actin (globular) joined front to back to form F-actin (fiber)

Question 24

what are the 3 subunits of troponin

Answer 24

C-binds calcium
T-attaches to tropomyosin
I-inhibitory

Question 25

In the crossbridge cycle, it starts at rest (actin/myosin interaction weak), ATP is partially hydrolyzed wehre? when activated, what happens

Answer 25

``` myosin head (in rest cocked position but not bound to actin filaments) -interaction is stronger and crossbridges become firmly attached ```

Question 26

initially, the crossbridge is at a right angle but rapidly shifts to 45, what supplies energy for this step? what form is it in?

Answer 26

an ATP bound to each crossbridge. this ATP is in partially broken down form

Question 27

what must happen for the crossbridge cycle to detach

Answer 27

new molec of ATP must bind to myosin head and undergo partial hydrolysis -cycle can then begin again

Question 28

what happens at rest in the effect of filament overlap on force generation what does short muscle equal? extend muscle?

Answer 28

optimal force can be produced by a muscle sarcomere aligned best (minimal overlap of actin and myosin, therefore max room to move) (heart=opopsite) short=more overlap extend=reduced tension bc reduced overlap

Question 29

tests for heart attack include blood levels of what? how does that get into the blood?

Answer 29

troponin -can also occur w/ sig. aerobic exercise | when cardiac muscle breaks down

Question 30

what is a motor endplate

Answer 30

a motor neuron synapses on the sarcolemma - entire area has sig invaginations of the plasma membrane - infoldings are lined w ACh receptors - axons are meylinated by schwann cells

Question 31

what is a motor unit

Answer 31

axon brances as it courses through muscle, and each of its terminal branches innervates a single muscle fiber. one axon per muscle cell.

Question 32

postsynaptic membrane is also called what? | what is its voltage change called?

Answer 32

endplate membrane | -its voltage change is called the endplate potential

Question 33

acetylcholinesterase is located where?

Answer 33

synaptic cleft and postsynaptic membrane

Question 34

action potential extends down T-tubules: what are the steps

Answer 34

1. depolarization causes L-type voltage sensors on T-tubule membrane to open ryanodine calcium channels in SR, allowing rapid release of Ca 2. calcium binds to troponin C subunit 3. calcium pump in SR takes Ca back up

Question 35

what are t-tubules purpose

Answer 35

to bring stimulation/signal from motor unit deep inside a muscle cell so all sarcomeres can be contracted

Question 36

what is membrane depolarization caused by

Answer 36

binding of ACh to the Ach (nicotonic) receptors in NMJ which causes an ionic shift (bc its an ionotropic receptor)

Question 37

sarcoplasic reticulum is a significant storage site for what

Answer 37

calcium

Question 38

what does botulinum toxin interfere w/ | -curare binds tightly to acetylcholine receptors but does not open channel, leading to what

Answer 38

``` acetylchoine release (SNARE protein interference) paralysis ```

Question 39

enhancement of neuromuscular transmission is done by

Answer 39

eserine, an ACh-esterase inhibitor, leaving ACh in the synaptic cleft longer, promoting muscle contraction

Question 40

what does myasthenia gravis result from | what is a possible treatment

Answer 40

antibodies to the ACh receptor blocking binding of ACh to muscle receptors - pt first present ptosis - eserine is a possible treatment for MG, allowing more/longer period of ACh in synaptic cleft to compete w/ antibody ACh receptor binding

Question 41

waht does a twitch result from

Answer 41

single action potential | -force low bc its brief

Question 42

in temporal summation of twitches from indiv action potentials, what do skeletal muscles want to do? if a second stimulus is given during relatation from the 1st, what happens? when a second stimulus closely follows 1st, what happens? if stimuli are given repeatedly and rapidly, the result is a sustained contraction called what?

Answer 42

temporally summate the force of contraction additional force is developed force and duration of twitch increases tetanus-a form a temporal summation

Question 43

what does organization of motor units allow of the msucle?

Answer 43

partial activation

Question 44

if muscles adapted for fine and precise control, only a few muscle fibers are associated with what? a total force of a muscle is determined by what? as more motor units are activated, what happens..

Answer 44

a given motor unit the number of motor units active at one time force increases

Question 45

what is isometric muscle contraction what is isotonic muscle contraction

Answer 45

muscle prevented from shortening-pulls against attachments and develops force - muscle is stimulated but length doesnt change ex. martial arts and yoga muscle can shorten and exert a constant force while doing so (work = load x dist) - allows for muscle shortening with stimulation ex. weight lifting

Question 46

what are teh 3 muscle energy sources

Answer 46

creatine phophate - during rest, stores energy to synthesize ATP - when creatine is drained, use: anaerobic respiration -occurs in absense of oxygen and results in breakdown of glucose to yield ATP and lactic acid aerobic respiratoin -only in presense of oxygen, produces more ATP/energy than aerobic

Question 47

``` what is slow twitch : why is it red? what kind of muscles here? how is the crossbridge cycle? what kind of diamter fibers? engage in what kind of resp more efficeintly? how is the ATPase breakdown? glycogen? ```

Answer 47

dark meat, red bc of myoglobin (pigmented oxygen carrying muscle protein, oxygen reserve in muscle) - endurance muscles - crossbridge cycle is slower in these muscles - posture muscles: those that are contracted all the time (ex most back muscles), fatigue resistant - smaller diameter fibers - engage in aerobic respiration more efficiently - ATPase breakdown slow - low glycogen

Question 48

what is intermediate twitch muscle? - what kind of diameter - high what capacity? - what kind of myoglobin? - glycogen? - resistant?

Answer 48

``` fast oxidative- endurance in trained muscles intermediate fiber diatmeter high anaerobic capacity intermediate myoglobin fatigue resistant high glycogen ```

Question 49

``` what are fast switch muscles what color mean diameter? myoglobin? mit and capillaries? fatigue? glycogne? ```

Answer 49

``` fast glycolytic, rapid intense movemtns white large diameter low myoglobin few mit and capillaries fatigue prone high glycogen ```

Question 50

what are the steps to muscle reflexes-withdrawal

Answer 50

1. arrival of stimulus and activation of receptor 2. activation of sensory neuron 3. info processing in CNS 4. activation of a motor neuron 5. response by effector

Question 51

what are the pain receptors

Answer 51

pseudounipolar neuroons of the dorsal root ganglia

Question 52

where is reflex circuitry in?

Answer 52

all w/in the spinal cord, very fast

Question 53

what are the steps to a monosynaptic, deep tendon reflex (ex. knee jerk)

Answer 53

1. stretching of muscle stimulates muscle spindles 2. activation of sensory neuron 3. info processing at motor neuron 4. activation of motor neuron 5. contraction of muscle

Question 54

wehre does the monosynpatic deep tendon reflex occur? | wehre do afferent nuerons synapse directly on?

Answer 54

L3/L4 level of spinal cord efferent

Question 55

waht do muscle spindles sense in deep tendon reflex? what do they provide data about? they are encapsulated muscle fibers w/ what?

Answer 55

rate of stretch - data about muscle length and rate of stretch - afferent neurons (intrafusal vs extrafusal fibers_

Question 56

what are intrafusal fibers | what are extrafusal fibers

Answer 56

gamma motor neurons (travel efferently back to spindle to reset the set point) can innervate muscle as well but mostly the spindle alpha motor neurons (std motor neuron in ant horn of spinal cord which innervates muscle at NMJ) aka LMN

Question 57

what are the 2 types of sensors w/in the muscle spindle

Answer 57

nuclear chain fiber-measure static length (if nothing happens, send signal) nuclear bag fiber-thicker, sends signal of a change, ending w/ the muscle, in which the spindle is located, contracting, dynamic

Question 58

what is the golgi tendon organ handled by? | what does it provide information for?

Answer 58

cerebellum | about the amont of force being generated, not the rate of change

Question 59

what are the types of smooth muscle

Answer 59

visceral or unitary-function as a unit via gap junctions so fibers dont need to stimulate many cells ex. syncitium (single cell w/ many nuclei) multiunit-cells act as independent units,ex. pupillary constrictor

Question 60

``` morphology-is it striated? cell margins have what? what is at the ends of central nucleus? are tehre T tubules? what is required to initiate contractions what kind of intermediat efilaments cells are coupled by what? ```

Answer 60

- not striated, fusiform (actin and myosin filaments overlap giving a dense body (sm muscle equiv of a z lin) where actin filaments are anchored - caveolae - mit - NO bc cells are small - calcium but diff from skeletal muscle - thick, thin, and int filaments. thin and int filaments ass w/ dense bodies (analgous to Z line) noncontractile int filaments (desmin and vimentin) - desmosome and gap junctions

Question 61

in smooth muscle contraction, what does calcium enter through? Ca release from SR by waht? what is Ca restored by? Na is taken outside of the cell via what? what does this allow?

Answer 61

- voltage and ligand gated channels - IP3 and Ca itself - active transport system in SR and plasma mem (Ca ATPase) and by Na-Ca exchange - Na/K pump, allowing the Ca/Na exchange to get more Ca out of the cell

Question 62

what is contraction mediated by? what kind of regulation? when calmodulin binds 4 Ca ions, it associates w/ what? what does it need to proceed?

Answer 62

myosin filament proteins myosin linked regulation: thin filaments lack troponin -w/ myosin light chain kinase (MLCK) and light chains become phophorylated -crossbridge cycle then proceeds

Question 63

what is relaxation mediated by? | -dephohsphoylated mysoin has low affinity for what?

Answer 63

myosin light chain phosphatase (MLCP) | -actin, so cycle terminates

Question 64

biochemical relaxation mechanisms have 2: both involving what? binding of norepinephrine activates what? what does this result in? what stimulates guanyly cyclase? what does tihs lead to? then promote? then lead?

Answer 64

2nd messengers - adenylyl cyclase, resulting in formation of cAMP, which is a promoter of relaxtion - NO, leads to activation of cGMP-dependent protein kinase and promotes the opening of calcium-activated K ion channels leading to hyperpolarization and relaxation

Question 65

NO is thought to be what

Answer 65

autoregulatory factor responsible for keeping retinal capillaries patent