Muscular (E3) Flashcards
3 layers of skeletal muscle
- Epimysium
- Perimysium
- Endomysium
Components of myofibrils
Sarcomere composed of thin and thick filaments and Z & M lines or discs
Thick filaments
Composed mainly of myosin which is made up of 2 heavy chains and 4 light chains
Thin filaments
Composed of actin, nebulin, troponin, and tropomyosin
Muscle tone
Resistance to stretch exhibited by a relaxed muscle
- due to baseline calcium in the cytosol
Intrinsic muscle tone in smooth muscle
Due to baseline Ca+ levels in the cytosol causing low level tension activity
Alpha motor neurons
-innervate skeletal muscle fibers
-cell bodies are located in the brainstem and spinal cord
T/F: all neuromuscular junctions are excitatory.
True
Botulinum toxin
Neurotoxin released from clostridium botulinum
-blocks Ach release
Curare
-blocks Ach receptors
-similar in action to nondepolarizers
T/F: a muscle cell has multiple nuclei
True
Satellite cells
Undifferentiated stem cells that repair damaged or destroyed skeletal muscle fibers
Skeletal muscle
-attached to bones by tendons
Sarcomere
One unit of thin and thick filaments
Wide dark bands in the middle
A band
Light bands
I bands
Narrow dark bands in middle
H zone (inside A band)
M line (inside H zone)
Sarcoplasmic reticulum
-same as endoplasmic reticulum in most cells
-store large quantities of Ca+
Sarcolemma
-plasma membrane of muscle cell
-propagates action potential
Contraction
Activation of the force generating sites within muscle fibers (the cross bridges)
Motor unit
A motor neurons and the muscle fibers it innervates
How is the length of a skeletal muscle cell related to the force it can generate?
Skelta muscle cells generate the most force when the contraction occurs at an intermediate length
Phases of muscle twitch
Latent period
Contraction phase
Relaxation phase
Latent period
Time elapsed from the application of a stimulus to the beginning of the contraction
Contraction period
Cross bridges are active in the muscle shortens if tension is great enough to overcome the load
Relaxation period
Active transport of calcium back into the sarcoplasmic reticulum and degradation of acetylcholine
Single twitch
Same size twitches if completely relaxed between
Twitch summation
Muscle fiber restimulated before completely relaxed, second twitch added to first twitch
Tetanus
Muscle fibers stimulated so rapidly. It does not relax, maximus is saying contraction occurs
Train of four responses
Absent - 100
One twitch - 90
Two twitches - 80
Three twitches -75
Four twitches -0-75
Central command fatigue
Appropriate regions of the cerebral cortex fail to send excitatory signals to them motor neurons
Oxidative fibers
-more mitochondria
-more blood flow
-long term contractions (posture)
Glycolytic fibers
-few mitochondria
-large store of glycogen
-quick activity bursts
-lack myoglobin (white muscle fibers)
