MCP 30: Muscles II

Question 1

length-tension relationship (for sarcomere)

Answer 1

maximal force of contraction for sarcomere determined by degree of overlap between actin and myosin, when at optimal overlap, sarcomere at resting potential

Question 2

isometric contraction

Answer 2

length stays the same, but tension changes, i.e. pushing against a wall

Question 3

isotonic contraction

Answer 3

muscle tone stays the same but length changes; i.e. lifting free weights

Question 4

combination of isometric and isotonic contractions

Answer 4

usually isometric contraction followed by isotonic contraction; isometric to counteract load of weight then isotonic to move it forward

Question 5

force-velocity relationship (muscle)

Answer 5

as force increases, the velocity of shortening decreases, for isotonic contractions

Question 6

ways to increase contraction speed

Answer 6

1.) faster ATPase 2) changing the force on the muscle (force-velocity relationship)

Question 7

ways to increase muscle tension

Answer 7

1.) optimizing length tension relationship 2.) hypertrophy 3.) increasing number of stimuli 4.) increasing the # and type of motors units involved

Question 8

length tension relationship (muscle)

Answer 8

total tension is the sum of the active and passive elements

Question 9

active tension

Answer 9

due to myosin/actin crossbridges

Question 10

passive tension

Answer 10

due to the elasticity of muscle components

Question 11

parallel elastic element

Answer 11

passive tension

Question 12

hypertrophy

Answer 12

increasing the size of muscle fibers by increase the number of sarcomere

Question 13

hyperplasia

Answer 13

increasing the number of muscle fibers

Question 14

tetany

Answer 14

mutiple action potentials at a high frequency allow for plentiful Ca2+ release and not enough time for the SR to uptake the calcium; leaders to maximal muscle force

Question 15

series elastic element

Answer 15

accounts for delay between calcium release and contraction, think of fishing line that needs to be taut before able to reel it in, twitches can’t cause maximal tension because of series elastic element

Question 16

motor unit

Answer 16

group of muscle fibers that are all innervated by the same alpha neuron and therefore will twitch all at the same time by an AP; increasing number of fibers innervated in a motor unit will increase strength

Question 17

type I motor unit (muscle cell)

Answer 17

Properties of muscle cell: small number of innervated fibers, moderate fiber diameter, low force, oxidative metabolism, moderate conduction velocity and low fatiguabiity, high myoglobin and lots of mitochondria, low ATPase activity, used for endurance activities, burn fat

Question 18

type II motor unit (muscle fiber)

Answer 18

Properties of muscle cell: many innervated fibers, large fiber diameter, large output force, fast ATPase activity, low excitability, anaerobic exercise, use glycolytic metabolism leading lactic acid behind, high glycogen content, low number of mitochondria, increased fatigue

Question 19

red fibers

Answer 19

part of type I motor units

Question 20

white fibers

Answer 20

part of type II motor units

Question 21

innervation ratios

Answer 21

ratio of muscle fibers to an innervating neuron; low ratios are used for fine muscle tasks and high ratios used for tasks that require immense strength

Question 22

mutiunit smooth muscle

Answer 22

require fine motor movement, cells electrically isolated from each other, each cell separately innervated, neurogenic

Question 23

unitary smooth muscle

Answer 23

less precision, more muscle fibers innervated per motor neuron, cell connect via gap junctions, forms syncitium, contains pacemaker smooth muscle cell where innervation is, myogenic, also called visceral muscle

Question 24

single spike

Answer 24

AP caused by electrical stimulation, hormone/neurotransmitter action or muscle stretch

Question 25

plateau shaped AP

Answer 25

typical pattern of AP but repolarization delayed

Question 26

slow wave APs

Answer 26

extremely slower than other APs, Ca2+ channels close very slowly

Question 27

smooth muscle

Answer 27

composes internal contractile organs except heart, used to expel contents, change cross sectional area of organ, change dimensions, movement (piloerection), smooth muscle cells are small and unstriated, innervated by autonomic nervous system

Question 28

syncytium

Answer 28

group of cells in unitary smooth muscle

Question 29

dense bodies

Answer 29

point of attachment for actin in smooth muscle

Question 30

neurogenic

Answer 30

requires a nerve impulse for contraction; has characteristics that resemble skeletal muscle and each fiber completely insulated from each other

Question 31

myogenic

Answer 31

innervation isn’t required for the initiation of a contraction on visceral smooth muscle, the innervation serves to modulate the intrinsic pacemaker ability

Question 32

caveloi

Answer 32

indentations on the smooth muscle cell membrane which contain voltage-gated Ca2+ channels

Question 33

voltage gated Ca2+ channels

Answer 33

on caveoli, open in response to AP and allow calcium from extracellular space into muscle cell

Question 34

calcium induced cacium release channels

Answer 34

Ca2+ or secondary messager binds to calcium induced calcium release channels on SR and allow Ca2+ to flow in cytosol

Question 35

store-operate channels

Answer 35

allow influx of calcium from extracellular space into cystol

Question 36

IP3 gated Ca2+ release

Answer 36

G protein system that causes release of Ca2+ from channels on SR

Question 37

contractions in smooth muscle

Answer 37

1. ) intracellular Ca2+ concentration rises, and Ca2+ binds to calmodulin (CAM) 2. ) Ca-CAM complex binds to myosin light chain kinase (MLCK) 3. ) MLCK phosphorylates myosin 4. ) phosphorylated myosin forms cross-bridges with actin, contraction occurs 5. ) Myosin light chain phosphatase (MLCP) dephosphorylates myosin, stops the cross bridge cycle

Question 38

latch mode

Answer 38

the smooth muscle can remain contracted without using ATP which is great when you really have to pee otherwise you’d be burning through calories to keep from peeing on yourself.

Question 39

type 1 motor unit (nerve cell)

Answer 39

Properties of nerve: small cell diameter, fast conduction velocity, high excitability

Question 40

type II motor unit (nerve cell)

Answer 40

Properties of nerve: large cell diamter, very fast conduction velocity, low excitability,

Question 41

type 1 motor unit (nerve cell)

Answer 41

Properties of nerve: small cell diameter, fast conduction velocity, high excitability

Question 42

type II motor unit (nerve cell)

Answer 42

Properties of nerve: large cell diamter, very fast conduction velocity, low excitability,