Chapter 10 and 11, muscle tissues

Winona State University, Dr. Larson A & P

Muscle fiber increases

force and diameter of muscle increases

Functions of muscles

movement, stability, heat production, glucose regulation, control openings and passageways

Movement

move the body or its parts

Stability

maintain upright posture against gravity, involuntary joint stability

Control Openings and Passageways

internal muscular rings called sphincters, in eyes and GI tract

Regulate Glucose

the concentration into the bloodstream, store glucose

Heat Production

skeletal muscles produce 20-30% body heat, 85% during exercise

Muscle Organ

muscle, nervous, connective, and epithelial tissue types, thousands of muscle cells

Endomysium

thin sleeve of CT around muscle fibers

Perimysium

thick layer of CT around fascicles

Epimysium

fibrous sheath around entire muscle

Two kinds Epimysium

outer fascia gradient, and inner projections for perimysium

Fascia

CT that separates muscle from neighboring objects

fusiform

moderate strength

parallel

less strength

pennate

greatest strength

triangular

relatively strong

circular

less strength but effective

Direct attachment

appears that muscle emerges directly from the bone

Indirect attachment

muscle attached to bones due to tendons

Aponeurosis

tendon is broad flat sheet

Retinaculum

connective tissue that tendons from other muscles pass under

Origin

attach at stationary end

Insertion

attach at moving end

Prime Mover action

muscle producing most force for movement

Synergist action

aids the prime mover

Antagonist action

opposes prime mover

Fixator action

muscle prevents movement of bone

Physiologic Characteristics

excitability, conductivity, contractility, extensibility, elasticity

Excitability

chemical signals are received and stretched as electrical changes across the plasma membrane

Conductivity

local electrical excitation sets off wave that travels along muscle fiber

Contractility

shortens when stimulated

Extensibility

capable of being stretched between contractions

Elasticity

when muscle cell is stretched and released, it recoils to short length like a rubber band

Skeletal muscle cell

voluntary and striated, myofiber or muscle fiber

Striations

alternating bands due to arrangement of internal contractile proteins

Sarcolemma

plasma membrane

sarcoplasm

cytoplasm of muscle fiber, occupied by myofibrils

Sarcoplasmic Reticulum

forms network around each myofibril and function as Calcium storage site

Terminal Cisterns

surround each myofibril, calcium collects there

T Tubules

infoldings of sarcolemma penetrate through cell. Signals SR to release calcium into cytosol

Thick Filaments

myosins intertwined, heads directed outward in helical array

Thin Filaments

two intertwined actin strands, active sites which myosin heads bind to. 40-60 molecules tropomyosin. Active sites are covered when relaxed

Elastic Filaments

made of springy titin protein. Core of thick filaments to anchor them between thin filaments for recoil muscles

Bare Zone

thick filament part without myosin heads

actin and myosin

shorten the muscle fiber, proteins

troponin and tropomyosin

determine when the muscle contracts

dystrophin

accessory protein ,links actin to endomysium and transfers force to the tendon, muscular dystrophy

A band

dark band, overlapping thick, thin, and elastic fibers

I band

light band, thin and elastic filaments

H band

thick filaments only, no myosin heads, contains vertical m line.

sarcomere

from one z-disk to another.

Nerve

enclosed, cable like bundle of nerve fibers called axons

Motor neuron

nerve cell whose cell bodies are in brainstem or spinal cord, Somatic= skeletal muscles

Axons

transmit nerve signals away from nerve cell body, branch extensively at distal end

Somatic motor fibers

AXONs that lead to muscles, stimulate all muscle fibers to contract in unison

Motor Unit

one nerve fiber and the muscle fibers innervated by it

Synapse

point where nerve fiber meets its target cell

Neuromuscular Junction

when target cell is a muscle fiber

Excitation

a process which action potentials in nerve fiber lead to action potentials in the muscle fiber

Excitation-contraction coupling

events that link the action potentials on the sarcolemma to activation of the myofilaments, preparing to contract

Contraction

step in which muscle fiber develops tension and may shorten

Relaxation

stimulation ends, muscle fiber relaxes and turns to resting length

Mechanically Gated

respond to physical stress like stretch or pressure

Ligand Gated

chemical messengers like neurotransmitters, molecule attaches to others

Voltage Gated

changes in electrical potential across the PM

Isometric

muscle develops tension but doesnt change length

Isotonic

muscle maintains constant tension while changing length. Concentric: muscle shortens. Eccentric: muscle lengthens

Anaerobic Fermentation

enables cells to produce ATP in absence of oxygen, yields lactate

Aerobic fermentation

produces far more ATP with oxygen, no lactate