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Muscle Function

-produce movement
-generate heat
-maintain posture
-move substances in body
-regulate organ volume

Muscle properties

-Excitability
-Contractibility
-Extensibility
-Elasticity

Excitability

ability to respond to stimuli by producing action potential

Contractibility

ability to shorten/thicken generating force

Extensibility

ability to stretch without damaging tissue

Elasticity

ability to return to original size/shape after contraction/stretching

Fascia

fibrous CT that surrounds the muscle tissue

Superficial fascia

separates muscle from skin
-protects muscle from trauma
-protects against shock (insulates)
-stores fat
-carries blood vessels/nerves

Deep Fascia

it groups muscles with similar functions together
-it fills spaces b/w muscles
-it carries nerves/blood vessels/lymphatic vessels

Epimysium

CT membrane that covers entire muscle

Perimysium

CT membrane covers individual fasicle

endomysium

CT covers individual muscle fiber and fills space in between.

sarcolemma

plasma membrane

sarcoplasmic reticulum

resembles ER. encircles each myofibril
-stores/ release Ca++

T. Tubules

to rapidly propagate nerve impulse along muscle fiber

Sarcoplasma

resembles cytoplasm.
-glycogen=ATP
-myoglobin--reddish pigment. stores and releases 02 in aerobic reaction.

sacromere

area between 2 Z discs. most important basic functional unit in muscle tissue

Actin

the thin filament protein

Myosin

thick filament protein
-a motor protein=spreads ATP

Sacromere Anatomy

-H Zone: only myosin
-A Band: both actin and myosin
-I band: only actin
-M line: marks center of the H-Zone
-Z discs: mark center of I-Band
-----anchors thin filaments
-----connect myofibrils

Muscle proteins

-contractile, regulatory, and structural

Contractile proteins

for contraction
-actin
-myosin

regulatory proteins

to switch contraction on/off

troponin

holds tropomyosin in place

tropomyosin

when is held in place, it blocks myosin from reaching actin

structural proteins

titin: responsible for elasticity
Myomesine: form M-line
Nebulin: ensures alignment of thin filaments
Dystrohin: carries tension from sacromere to tendon.

Muscle contraction

1.) Ca++ is released from sarcoplasmic reticulum
2.) Ca++ binds to troponin and changes its shape
3.) Tropomyosin moves out of the way
4.) Myosin can now reach actin
5.) myosin heads use ATP and move actin (contraction)

synapse

area of communication b/w two neurons, or a neuron/target cell.

Neurotransmitter

a protein released from neuron to switch a muscle contraction on.

neurotransmitter junction

synapse b/w a neuron and a muscle

Muscle Energy source

1.) Creatine Phosphate: 1 ATP---15 seconds
2.) Anaerobic cellular respiration: 2 ATP---30-60 seconds
3.) aerobic respiration: 36-38 ATP hours--need O2

Twitch contraction

a brief contraction of all muscle fibers in a motor unit in response to single action potential

latent period

A brief delay between the stimulus and muscular contraction

contraction period

-Ca++ binds to troponin
-Cross-bridges form

wave stimulation

the increased strength of contraction resulting from the application of second stimulus before the muscle has completely relaxed after a previous stimulus. (fused/complete or unfused/imcomplete)

Skeletal fiber types

1.) Based on content of Myoglobin
a. increased myoglobin = dark meat fibers
b. decreased myoglobin = white meat fibers
2.) Based on structural function
a. Aerobic--oxidative fiber (fast/slow)
b. Anaerobic--Glycolytic fibers (fast)

Cardiac Muscles

-in the walls of the heart
-fibers branch
-fibers have intercalated discs (desmosomes & gap junction)
-contractions are longer than skeletal
-involuntary; striated

smooth muscle

1.) visceral (single unit)
-----in organs/large blood vessels
-----all muscle fibers contract as a single unit
2.) Multi unit
-----iris/arrector pili muscle
----- each muscle fiber contract singly
-slowest, non-striated, involuntary

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