Chapter 11 - Muscular Tissue

excitability

responsiveness → chem signals, stretching

conductivity

electrical excitation sets off a wave of excitation that travels along the muscle fiber

contractility

shortens when stimulated

extensibility

capable of being stretched between contraction

elasticity

returns to its original rest length after being stretched

myofiber

muscle cell / muscle fiber

endomysium

CT around ENTIRE MUSCLE CELL

perimysium

CT around muscle fascicle

epimysium

CT surrounding entire muscle

sarcolemma

plasma membrane of a muscle fiber (cell)

sarcoplasm

cytoplasm of a muscle fiber (cell)

myofibrils

long protein cords occupying most of the sarcoplasm

glycogen

carbohydrate stored to provide energy for exercise

myoglobin

red pigment - provides oxygen when needed for muscle activity

myoblasts

stem cells that fused to form each muscle fiber early in development

satellite cells

unspecialized myoblasts (stem cells) remaining between the muscle fiber (cell) and endomysium

mitochondria

packed into spaces between myofibrils - POWERHOUSE

sarcoplasmic reticular (SR)

smooth ER that forms network around EACH myofibril

• CALCIUM RESERVOIR

terminal cisterns

dilated end-sacs of SR (sarcoplasmic reticulum) which cross the muscle fiber from one side to the other

T Tubules

inside sarcolemma - penetrate through cells and emerge onto other side

Tirad

T Tubule and two terminal cisterns associated with it

thick filaments

GOLF CLUB

several hundred myosin molecules

thin filaments

fibrous actin, tropomyosin, troponin

fibrous (f) actin

2 intertwined strands

• string of globular actin subunits each with an ACTIVE SITE that can bind to head of myosin molecule

tropomyosin

each blocking 6/7 active sites on a G actin subunit

troponin

small, calcium-binding protein on EACH tropomyosin molecule

Titin

ELASTIC filament

• stabilizes and positions thick filament

• PREVENTS OVERSTRETCHING

contractile proteins

myosin and actin

what are regulatory proteins?

tropomyosin and troponin

function of regulatory proteins?

• determines when fiber can contract (LIGHT SWITCH)

• activation by release of calcium into sarcoplasm and binding to troponin

  • moves tropomyosin off the active sites

A Bands

DARK (anisotropic)

includes H band and M line

I Band

LIGHT (isotropic)

Includes Z disc

sarcomere

Z disc to Z disc

denervation atrophy

shrinkage of paralyzed muscle when nerve remains disconnected

somatic motor neurons

nerve cells whose cell bodies are in the brainstem and spinal cords

somatic motor fibers

their axons lead to the skeletal muscle

motor unit

one nerve fiber and all the muscle fibers innervated by it

small motor units

FINE degree of control

• 3-6 muscle fibers per neuron

• eye and hand muscles

large motor units

STRENGTH over control

synapse

nerve fiber meets its target cell

neuromuscular junction (NMJ)

target cell is a muscle fiber

axon terminal

swollen end of nerve fiber

• contains synaptic vesicles with acetylcholine (ACh)

synaptic cleft

gap between axon terminal and sarcolemma

basal lamina

thin layer of collagen and glycoprotein separating schwann cell and muscle cell from surrounding tissues

acetylcholinesterase (AChE)

breaks down ACh → allows for relaxation

rigor mortis

hardening of muscles and stiffening of body 3-4 hours after death

Isometric muscle contraction

stays SAME length with external resistance (holding weight)

Isotonic muscle contraction

muscle changes length with NO CHANGE in tension

Concentric contraction

muscle shortens as it maintains tension (lifting weight)

eccentric contraction

muscle lengthens as it maintains tension (slowly lowering weight)

isometric phase

BEGINNING

muscle tension rises but muscle does not shorten

isotonic phase

Muscle shortens and move the load

anaerobic fermentation

cells produce ATP with NO OXYGEN - produces lactate (needs to be disposed by liver)

Aerobic respiration

lots of ATP (yay!), no lactate (yay!), continual oxygen and breathing (noooooooo)

muscle fatigue

weakness from prolonged use of muscles

STOP SLIDE

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