BIO 201 Unit 3 lecture

What are the functions of muscles?

movement of body and organs

maintain posture and prevent movement

control openings and passageways

body heat production

What is the skeletal muscle structure?

Muscle fibers, fascicle, muscle

what is muscle fiber built of?

long myofibrils (not cells) in skeletal muscle that is connected in linear series

what is a fascicle built of?

bundle of muscle fibers

what is muscle built of?

bundle of fascicle

muscle fascicle

what are the connective tissues of muscle?

endomysium, perimysium, epimysium

describe endomysium

wraps the fascicle. thin layer of areolar tissue surrounding each cell. Allows room for capillaries and nerve fibers

describe perimysium

thicker layer of connective tissue surrounding a bundle of fascicle

describe epimysium

separates muscle, covers whole muscle belly

What are the characteristics of muscle?

responsive, conductive, contractile, extensible, elastic, conversion

what does the characteristic responsive mean?

respond to signals, and electrical changes across plasma membrane

what does the characteristic conductive mean?

electrical change triggers excitation that travels along muscle fiber

what does the characteristic contractile mean?

shoten when stimulated

what does the characteristic extensible mean?

capable of being stretched

what does the characteristic elastic mean?

return to original length after extended

what does the characteristic conversion mean?

change of chemical energy ATP into mechanical energy

what is direct muscle attachement

epimysium is continuous with periosteum

what is indirect muscle attachment?

epimysium continues as tendon or aponeurosis. Merges into periosteum as performing fibers

muscles attachments and stress

stress will tear tendon before pulling tendon loose from muscle or bone

where does muscle attach to

the dermis

what are the coordinated muscle actions

prime mover, synergist, antagonist, fixator

what is the prime mover

produces most of the force

what is the synergist

aids prime mover, stabilize joint, modify direction of movement

what is the antagonist

oposes prime mover, prevent excessive movement and injury

what is the fixator

prevents movement of bone that prime mover is attached to

what are the three types of muscle

skeletal, smooth, cardiac

what are characteristics of skeletal muscle?

muscle fibers, attached to bones. striated appearance, voluntary control, multi-nucleation, and ability to contract quickly but fatigue easily.

What are muscle fibers structure?

Multinucleated, sarcolemma, scarcoplasm, sarcoplasmic reticulum

what is the sarcolemma

tranverse tubles penetrate, carry electric current to cell interior

what builds the sarcoplasm

myofibrils, glycogen, myoglobin

what are myofibrils

comprised of myofilaments

what is myoglobin

protein that stores oxygen

what builds the sarcoplasmic reticulum

terminal cisternae (calcium storage)

muscle fiber

what are thick filaments

200-500 myosin molecules, heads in outward spiral, bare zone in middle with no head

what are thin filaments

primarily composed of actin, troponin, and tropomyosin; responsible for muscle contraction by sliding over thick filaments

what is fibrous actin

globular actin that subunits with the active sites

what is tropomyosin

blocks active sites of 6 or 7

what is troponin complex

bound to calcium and changes shape of troponin-tropomyosin complex

what are elastic filaments made of

titin which is springy and core of each thick filament.

what does titin connect to

connects thick filament to z-disc

what is the function of elastic filaments

alignment, resist overstreching, helps cell recoil

filaments

what are contractile proteins made of

myosin and actin

purpose of contractile protein

do the work of muscle contraction

what is regulatory protein made of

tropomyosin and troponin

what is purpose of regulatory proteins

on/off switch

filament bands

how are filaments organized

A bands, I bands, sarcomere

what are A bands

thick and thin filament band with H zone

what is the H zone

center of A band that contains only thick filaments and appears lighter

what are I bands

thin filament and connectin

what is the connectin

z disc protein that bisects I band and anchors titin and think filaments

what is the sarcomere

z-disc to z-disc

how do muscle cells shorten

sarcomeres shorten pulling z-discs closer together. Filaments do not change length and overlap/slide over each other during contraction.

how is skeletal muscle stimulated

by nerve, if no nerve sensation that equals paralyzation

what are somatic motor neurons

200 terminal branches that supply one muscle fiber

what is a motor unit

a motor neuron and all the muscle fibers in innervates (controls)

describe long term contraction motor units

weak contraction over wide areas that alternate rest

describe fine control motor units

small motor unites for precise control

describe strength control motor units

larger motor units for powerful contractions, more muscle fibers per nerve fiber

what are neuromusclar junctions

The synapse between a motor neuron and a muscle fiber where neurotransmitters are released to trigger muscle contraction.

what is ACh

acetylcholine

what are the NMJ components

synaptic knob, ACh receptors, AChE, synaptic cleft, Schwann cell

what is the synaptic knob

swollen end of nerve fiber that contain ACh, releasing neurotransmitters into the synaptic cleft.

what are ACh receptors

located on the sarcolemma junctional folds, bind ACh released from nerve

what is AChE

Acetylcholinesterase

what is purpose of AChE

enzyme to break down ACh and cause relaxation

what is the synaptic cleft

gap between nerve and muscle cell

what is the schwann cell

envelopes and isolates the NMJ

neuromuscular junction

what is membrane potential

the difference in electric charge across a cell membrane, critical for neuronal signaling and muscle contraction.

what are the types of ion channels

leakage (nongated) or active (gated)

what are leakage channels

passive channels that are always open

what are the types of gate channels

voltage, chemically, mechanically, light

what is a volate gated ion channel

trigger is change in membrane potential

what are types of voltage gated channels in NMJ

Na (sodium) and K (potassium) voltage regulated gates

what are chemically gated channels

opens and closes in response to chemical stiumuli

what are types of chemically gated channels

hormones, neurotransmitters and ions

what are mechanically gated channel

open or close in response to touch, vibration or pressurewha

what is a type of touch mechanically gated channel

meissner

what is a type of pressure mechanically gated channel

pacinian

what are light gated channel

open and close in response to light

where is light gated channel located

rods and cones of eye

what are electrically excitable cells

volatge changes in response to simulation

what happens when ion gates open in electrically excited cells

allows Na+ (sodium) to ruch into cell

what is voltage shift in electrically excited cells called

action potential or depolarization

what happens to muscle and nerve cells in elecrically excited cells

plasma membrane is polarized (charged)

what is resting membrane potential

difference in charge across the membrane with Na+ (sodium) outside of cell and K+ (potassium) and other anions inside cell

what are the four muscle components to contraction and relaxation

excitation, excitation/contraction coupling, contraction, relaxation

what is excitation in muscule contraction

action potential in the nerve leads to formation of action potential in muscle fiber

what is excitation/contraction coupling in muscle contraction

action potentials in sarcolemma activate myofilaments and trigger the release of calcium ions from the sarcoplasmic reticulum, enabling muscle contraction.

what is contraction in muscle contraction

shortening of muscle fiber or formation of tension

what is relaxation in muscle contraction

return of fiber to its resting length

what is isometric muscle contraction

tension develops without changing length

what are the types of isotonic muscle contraction

concentric and eccentric

what is concentric muscle contraction

tension develops while shortening (bicep curls

what is eccentric muscle contraction

tension develops while lengthening (RDL’s)

what is a muscle twitch

minimal voltage to produce action potential