Muscle Fibers

For SJU Lecture and Lab A&P

Muscle cell properties

contractibility

Excitability(response to chemicals and hormones)

Conductivity(cells travel through electricity)

Distensiblity(elongation without damage)

Elasticity(returned to normal state)

Neuromuscular Junction

synapse where a single motor neuron communicate

Transmit signals from neuron to sacrolemma of muscles fiber

Three components: axon terminal, synaptic cleft, motor end plate

Excitation phase

action potential arrives at axon terminal, triggers, calcium channel to open

Calcium ions, move into the action terminal and trigger exocytosis synaptic vesicles

Synaptic vesicles release ACH into synaptic cleft

ACH binds to receptors on motor end plate

Sodium ion channels open and sodium enters muscle fiber

Sodium entry, depolarizes, sarcolemma, creating, and plate potential

VIDEO:https://mediaplayer.pearsoncmg.com/assets/_z_QVtvni1EUXVBVXaeWRbRFdEs7sV_g

Excitation Contraction Coupling

and complete potential stimulates on action potential

Action potential is propagated down the T-Tubles

T-Tuble depolarize leads to opening of calcium ion channel is SR and calcium ions enter cytosol

Calcium ions bond to tropnin

Tropomysin moose and active sites on Actin are exposed

VIDEO:https://mediaplayer.pearsoncmg.com/assets/apf-excitation-contraction-coupling

Contraction-cross bridge

ATP Hydrolysis “cock” the myosin head

Myosin head binds to Actin

Powerstroke occurs when phosphate, detached, myosin head and myosin pulls Actin towards the center of the sarcolemma

ATP breaks the attachment of myosin to Actin

VIDEO:https://mediaplayer.pearsoncmg.com/assets/5QBacoiPZ_QDy46rzobIBu9WIiGf125a

Muscle relaxation

Actylcholinsterase degrades remaining ACH and re-polarize occurs

Circle lemma returns, resting, and calcium ion channels in the SR close

Calcium is pumped back into the SR

Troponin shifts and pulls trypomyosin back into position to block active sites of Actin and muscle relaxes

VIDEO:https://mediaplayer.pearsoncmg.com/assets/FBw0ZSz7qfmIzeSTm3Fxh8Lo0zO8OoEg

https://quizlet.com/442186753/skeletal-muscle-parts-diagram/

A tendon-place where epimysium blends into a rope-like connection that links muscle to bone

B epimysium-connective tissue "overcoat" covering entire muscle

D muscle fiber-make up the fascicles; also known as a muscle cell allows contractibility

E endomysium- connective tissue layer that covers each individual muscle fiber surrounded by the ECM

F muscle fasciculi-visible bundles composed of muscle fibers that make up the whole muscle

G perimysium-connective tissue that covers muscle fasciculi (fascicle)

H Bone

Osteon

dense part of bone circular

Central canal

 blood vessels, parallel to the osteon lined with connective tissue called endosteum(inner layer of osteoblast, which secrete bone ECM and osteoclast)

Perforating canal

perpendicular to Lamelle carry blood vessels deep into Periosteum

Lamellae

lines bone ECM give strength

Lacunae

pockets, and layer of matrix osteocytes live in it

Osteocyte

 mature bone cells

Canaliculi

Tiny passage ways, allowed diffusion in nutrients and waste

Periosteum

membrane, blood vessels, nerves, attach, dense, irregular, connective tissue outside a bone

Endosteum

inside lining bone marrow covers trabeculae

Sarcolemma

 muscle fibers plasma membrane

T Tubule

stores, calcium ions

Modified smooth, endoplastic reticulum

Sarcoplasmic reticulum

Myofibril are wrapped in

Terminal Cisternae

on either side of the T-tubule

Triad

1 T-Tubule

2 terminal cisternae

Myofibril

small cyndricil organelles

Myofilment

protein subunits

Thick fillment

Composed of myosin 

Contractive protein

Thin filament

composed of Actin

Contractile protein

A band

dense region of striations

Overlap, thick and thin fill or only thick

I band

lighter region

Only thin

Z disc

middle of I band

Structural protein

H zone

middle of a band

Thick

M line

runs down H zone

Structural protein

Sliding fillment theory

filament move inward(towards M line) which make the Z disc closer

Resting potential

voltage in cell negative compared to outside

Solute move by

leak channel-always open to allow ion move( passive transport hide to low)

Gated-closed at rest, certain ions stimulated to open

Electrochemical gradient

Concentration ions, diffuse hide to low

Electrical-look at charge and goes to the opposite, like charges repel

This builds to the electro chemical gradient which has sodium move and cell due to it being positive and wants to move towards the negative part of the cell, and then the potassium moves on a concentration gradient

Action potential

Quick temporary change move negative inside to positive

Resting stage-muscle at -90 mill volts during rest

Depolarization-sodium moves in more positive in cell

Re-polarization-sodium potassium get pushed outside the cell inside us now negative

Propagation-continuation of this is a wave all throughout the cell

The three stages of electricity in excitability in a cell

resting potential

Solute move

Action potential

Anaerbobic Catabolism

Glycolysis

Glucose sources-food blood to muscle FORM 2 ATP

Anaerobic-no oxygen

Fate of Pyruvate- pyruvate turns into lactic acid

Creatine phosphate

has ATP extra phosphate, quick energy

Aerobic Catabolism

oxidative-reduction reaction

Fuel source glucose

Aerobic-oxygen

Myoglobin-help blood hold onto oxygen

Gain 30 ATP in crab cycle

Long lasting

Muscle twitches three phases

Latent Period-time for action potential to propagate into sarcolemma

Contraction-repeated Crossbridge cycles generate tension

Relaxation-calcium ions are reduced in inside of cell by SR pumps

* Refractory Period-between the start of Latent . And into the contraction. Where muscle fibers can't respond to another stimulus.

Wave summation

waves of messages together create one whole message

Unfused Tetanus

tension gets stronger

Fused Tetanus

Complete contraction, muscle no time to act, tension constant

Length-tension relationship

shorted muscle hit limit

Overstretch hit limit

Type one skeletal fibers-dark muscle

Small, slow, not a lot of tension

“never wear out”

Oxidative mitochondria

Slow twitch

Oxidative fiber

Type two skeletal fiber-light muscle

contract quickly

Fast and powerful

Fatigue easy

Glycolysis

Fast twitch and glycolic fibers

Motor units

larger means more fibers to respond

Fine VS gross control

Fine control-precise control small motor unit

Gross control-large units, powerful contractions

Recruitment

initiation of contraction

Muscle tone

when at rest muscle stay somewhat contracted

Hypotonia VS hypertonia

hypotonia-low muscle tone due to injury

Hypertonia-high muscle tone due to things like working out

Isotonic contraction

cause muscle to change and length

Concentric VS Eccentric

concentric-muscle tension exceeds resistance

Eccentric-elongated muscle decrease intention

Isometric

muscle contraction cannot overcome tension

Endurance training

repetitious less weight increase contracting muscles

Need energy increase the number of mitochondria

Need oxygen

Resistance

weight fewer repetitions

Muscles hypertrofify(increase in size) decrease in mitochondria

Disuse

muscles don't get used less toned atrophy

Muscle fatigue

inability to maintain a level of intensity

Depletion in metabolic and oxygen

Recovery Period

breathe fast, which increases oxygen which increases lactic acid