human physiology #3 pt2

types of muscle

skeletal, cardiac, smooth

total body weight

40-50% skeletal muscle

tendons

attached to bones

cold stress

heat production

force production

locomotion, breathing, postal support

epimysium

surrounds entire muscle

perimysium

surrounds fascicles (bundles of fibers)

endomysium

surrounds invididual fibers

basement membrane

below endomysiums

sarcolemma

muscle cell membrane

intracellular structures

sarcolemma, sarcoplasm, sarcoplasmic reticulum

sarcolemma

plasma membrane

sacroplasm

cytoplasm

sarcoplasmic reticulum

smooth er

myofibrils

skeletal and cardiac muscle their characteristics / appearance

actin

thin filament

myosin

thick filament (2 heavy chains 4 light chains)

structure of sarcomeres

z line, a band, I band, h zone, m line

z line

proteins that anchor to end of actin,

a band

contains thick filament (myosin)

I band

portions of actin

h zone

space between non-anchored ends

m line

proteins that connect myosin

sarcoplasmic reticulum (SR)

CA2+ stores and released following membrane excitation

terminal cisternae

enlarged, flattened regions that contain ca2+

transverse tubule (t-tubule)

between terminal cisternae, continues with plasma membrane, avenue through the Alps travel throughout the interior of muscle fibers

contractions

activation of force within muscle fibers

muscle stimulation

excitable tissue (action potentials), motor neurons

somatic efferent neurons (motor neurons)

ventral horns, heavily myelinated, differing diameter axons can conduct action potentials at different velocities

motor unit

allows organized muscle contractions, one alpha motor neuron

neurotransmitter

acetylcholine (ACh)

receptor

nicotinic

motor end plate

folded region of the muscles membrane under synapse

neuromuscular junction

axon terminal with motor end plate

NMJ steps

1.        Motor neuron action potential

2.        CA2+ enters voltage-gated channels

3.        Acetylcholine released

4.        Acetylcholine binding opens ion channels

5.        Na+ enters

6.        Local current between depolarized end plate and adjacent muscle plasma membrane

7.        Muscle fiber action potential initiated

8.        Acetylcholine degradation

end plate potential

analogous to EPSP, grated magnitude, muscle AP

excitation-contraction coupling

starts with Ap, step by step to initiate contraction, results in CA2+ released from SR

classification

maximal velocities of shortening, major pathway to form ATP — oxidative or glycolytic

MANY mitochondria of enzymatic machinery for synthesizing ATP

red muscle, small amounts of O2, oxidative fibers, high capacity

FEW mitochondria of enzymatic machinery for synthesizing ATP

white muscle, high concentration, large store of glycogen

slow oxidative

combine low myosin-ATPase activity with high oxidative capacity

fast oxidative glycolytic

combine high myosin-ATPpase activity with high oxidative capacity and intermediate glycolytic capacity

fast glycolytic

combine high myosin-ATPase activity with high glycolytic capacity

3 Functions for ATP during contract/relax

CB cycle: 70%, Ca2+ pumps: 25%, Na+/K+ pumps: 5%

3 ways a muscle fiber can form ATP

phosphorylation of ADP by creatine phosphate, phosphorylation of ADP by anaerobic glycolysis, oxidative phosphorylation of ADP in the mitochondria

tension

force generated

load

force exerted by an object

twitch

mechanical response to single action potential

twitch contraction

latent period, contraction phase, relaxation phase

latent period

from the action potential to the onset of contraction, due to the excitation-contraction coupling

contraction phase

development of tension due to the cross-bridge cycling

relaxation phase

tension decreasing, longer than contraction phase, takes time to get CA2+ sequestered

isometric

generate tension but don’t shorten the muscle, tension=load

isotonic

muscle length changes

concentric

shortening muscle

eccentric

lengthening muscle

contraction

must phosphorylate myosin

cross-bridge cycling

smooth muscle controlled by a CA2+ regulated enzyme that phosphorylates myosin

relaxation

must dephosphorylate myosin