muscles v Flashcards
What is the purpose of intercalated discs?
they allow AP to spread from one fiber to the next
How is cardiac muscle tissue stimulated?
by its own autorhythmic muscle fibers
How does cardiac muscle differ from skeletal muscle?
- intercalated discs
- continuous rhythmic activity
- longer lasting contractions
- lots of big mitochondria
how does cardiac muscle make ATP
depends on aerobic respiration
requires continuous oxygen supply
can use lactic acid from skeletal muscles to make ATP
Where is smooth muscle tissue found?
- walls of arteries, veins, hollow organs, and airways to lungs
- muscles that attach hair follicles, adjust pupil diameter, and adjust eye focus
Describe smooth muscle anatomy
spindle shaped central nucleus cells arranged in sheets no T tubules, use caveoli to trap extracellular calcium SR is less developed fine endomysium only
What is unique about smooth muscle filaments?
not arranged in sarcomere
no troponin/tropomyosin = always ready for crossbridge
Intermediate filaments in smooth muscle tissue
- attached to thin filaments at dense bodies
- attached to sarcolemma at dense plaque (also anchoring point for other smooth muscle cells)
smooth muscle tissue contraction
when actin and myosin generate tension, intermediate filaments pull on dense bodies to shorten cells
Innervation of single unit vs multi unit smooth muscle
single: variscosities release neurotransmitters into wide synaptic clefts (diffuse junctions)
- smooth muscle cells communicate via gap junctions
multi: autonomic motor neuron innervates fibers, similar to skeletal muscle
- no gap junctions
what stimulates smooth muscle?
motor neurons hormones chemicals physical factors (stretching/irritation) autorhythmic (pacemaker activity)
Where does smooth muscle get its calcium?
What physical structures are used to get calcium?
What is the effect of using these structures as opposed to the ones used by skeletal muscle?
- extracellular matrix (a little from SR)
- calveoli gets the calcium
- it takes calcium longer to get in and out of the cell, so activation is slow and contractions are prolonged
Smooth muscle contraction process, beginning with influx of calcium
- calcium binds to calmodulin
- activated calmodulin activates myosin light chain kinase
- kinase phosphorylates myosin head (using phosphate f/ ATP)
- myosin-P heads form crossbridge w/ actin
- myosin ATPase provides energy for crossbridge cycling and power stroke
Relaxation of Smooth muscle
-myosin phosphatase removes P from myosin which decreases myosin ATPase activity, so no more crossbridges
-Removal of calcium
ATPase pumps it into SR
Ca2+ ATPase pumps it through cell membrane
Ca2+Na+ antiporter exchange at cell membrane
graded smooth muscle contractions
- determined by variable amounts of calcium
- intracellular source = SR which reseases Ca thru 2nd messenger system
- extracellular source = membrane channels regulatd by stretch, depolarization (voltage gated), and chemicals (hormones, paracrines, and neurotransmitters)
