MCP 30: Muscles II Flashcards
length-tension relationship (for sarcomere)
maximal force of contraction for sarcomere determined by degree of overlap between actin and myosin, when at optimal overlap, sarcomere at resting potential
isometric contraction
length stays the same, but tension changes, i.e. pushing against a wall
isotonic contraction
muscle tone stays the same but length changes; i.e. lifting free weights
combination of isometric and isotonic contractions
usually isometric contraction followed by isotonic contraction; isometric to counteract load of weight then isotonic to move it forward
force-velocity relationship (muscle)
as force increases, the velocity of shortening decreases, for isotonic contractions
ways to increase contraction speed
1.) faster ATPase 2) changing the force on the muscle (force-velocity relationship)
ways to increase muscle tension
1.) optimizing length tension relationship 2.) hypertrophy 3.) increasing number of stimuli 4.) increasing the # and type of motors units involved
length tension relationship (muscle)
total tension is the sum of the active and passive elements
active tension
due to myosin/actin crossbridges
passive tension
due to the elasticity of muscle components
parallel elastic element
passive tension
hypertrophy
increasing the size of muscle fibers by increase the number of sarcomere
hyperplasia
increasing the number of muscle fibers
tetany
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
series elastic element
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
motor unit
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
type I motor unit (muscle cell)
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
type II motor unit (muscle fiber)
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
red fibers
part of type I motor units
white fibers
part of type II motor units
innervation ratios
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
mutiunit smooth muscle
require fine motor movement, cells electrically isolated from each other, each cell separately innervated, neurogenic
unitary smooth muscle
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
single spike
AP caused by electrical stimulation, hormone/neurotransmitter action or muscle stretch
plateau shaped AP
typical pattern of AP but repolarization delayed
slow wave APs
extremely slower than other APs, Ca2+ channels close very slowly
smooth muscle
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
syncytium
group of cells in unitary smooth muscle
dense bodies
point of attachment for actin in smooth muscle
neurogenic
requires a nerve impulse for contraction; has characteristics that resemble skeletal muscle and each fiber completely insulated from each other
myogenic
innervation isn’t required for the initiation of a contraction on visceral smooth muscle, the innervation serves to modulate the intrinsic pacemaker ability
caveloi
indentations on the smooth muscle cell membrane which contain voltage-gated Ca2+ channels
voltage gated Ca2+ channels
on caveoli, open in response to AP and allow calcium from extracellular space into muscle cell
calcium induced cacium release channels
Ca2+ or secondary messager binds to calcium induced calcium release channels on SR and allow Ca2+ to flow in cytosol
store-operate channels
allow influx of calcium from extracellular space into cystol
IP3 gated Ca2+ release
G protein system that causes release of Ca2+ from channels on SR
contractions in smooth muscle
- ) intracellular Ca2+ concentration rises, and Ca2+ binds to calmodulin (CAM)
- ) Ca-CAM complex binds to myosin light chain kinase (MLCK)
- ) MLCK phosphorylates myosin
- ) phosphorylated myosin forms cross-bridges with actin, contraction occurs
- ) Myosin light chain phosphatase (MLCP) dephosphorylates myosin, stops the cross bridge cycle
latch mode
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.
type 1 motor unit (nerve cell)
Properties of nerve: small cell diameter, fast conduction velocity, high excitability
type II motor unit (nerve cell)
Properties of nerve: large cell diamter, very fast conduction velocity, low excitability,
type 1 motor unit (nerve cell)
Properties of nerve: small cell diameter, fast conduction velocity, high excitability
type II motor unit (nerve cell)
Properties of nerve: large cell diamter, very fast conduction velocity, low excitability,
