Chapter 10
sudden involuntary contraction of a single muscle within a large group of muscles; usually painless
spasm
i. involuntary
ii. Often painful muscle contractions
iii. Caused by inadequate blood flow to muscles (ex. dehydration), overuse, injury, abnormal blood electrolyte levels
cramp
a. Small capillaries
b. Can produce smooth muscle fibers
pericytes
increase in size of cell
i. Skeletal tissues after birth
hypertrophy
increase in number of cells
i. Smooth muscle in certain instances
hyperplasia
i. Does not have T tubules
ii. Has invaginations of caveolae containing Ca++
iii. Attach to dense bodies functionally similar to Z discs
iv. Use calmodulin instead of troponin as regulatory protein
smooth muscle vs cardiac
smooth muscle squeeze substance through the organs by alternating contracting and relaxing
peristalsis
a. Irregular transverse thickenings of the sarcolemma that connect cardiac muscle fibers to one another
b. Contain desmosomes to hold together gap junctions
intercalated discs in cardiac muscles
an autorhythmic signal can be transmitted to connecting fibers so that they all contract in unison
conneting gap junctions
a. Muscle contracts but does not change length and no movement occurs
isometric contractions
muscle shortens and creates movement to reduce the angle of a joint
concentric
muscle tension resists the load and muscle length increases
eccentric
tension is constant while muscle length changes and movement occurs
1. concentric
2. eccentric
isotonic contraction
a. Extra oxygen over and above the resting oxygen consumption taken in the body after exercise
oxygen debt
a. Before actual muscle fatigue occurs, a person may feel tired and have the desire to stop activity
b. Occurs due to changes in CNS and generally results in cessation of exercise
c. Protective mechanism to stop exercise before muscle damage occurs
central fatigue
a. Even when at rest, skeletal muscle exhibits small amt of tension
b. Established by weak alternating, involuntary activation of small groups of motor units in the muscle
c. Established by neurons that activate skeletal muscle neurons
d. Keeps muscles firm but not enough strong force to produce movement
muscle tone
consists of single somatic motor neuron and all the skeletal muscle fibers it innervates
motor unit
the process in which the number of active motor units increase
mtoor unit recruitment
a. Brief contraction of all muscle fibers in a motor unit in response to a single action potential
b. Brief delay
twitch contraction
a. Inside each synaptic end bulbs, synaptic vesicles
b. Always the neurotransmitter in somatic neurons that innervate skeletal muscle
acetylcholine
a. The region of the sarcolemma opposite the synaptic end bulbs
b. Contains acetylcholine receptors
motor end plate
what happens when nerve impulses arrive at neuromusclar junction
calcium channels open
what happens when calcium channels open and becomes more concetrated in extracellular fluid
influx of calcium
what happens with an influx of calcium
Cause exocytosis of nervous tissue into synaptic cleft which diffuse across synaptic cleft
a. The synapse between a somatic motor neuron and muscle fiber
neuromusclular junction
When the myosin head attaches to actin, the myosin head is referred to as this
cross bridge
a. The sequence of events that links a muscle action potential and sliding of the filaments
Excitation-contraction coupling
a. Describes the mechanism that allows muscles to contract
b. Myosin pulls on actin, causing the thin filament to slide inward
sliding filament theory
i. Regulatory protein
ii. Blocks the myosin binding sites in relaxed muscle
iii. Held in place by troponin molecules
tropomyosin
i. Attachments of Ca++ ions induce a change in shape which pulls tropomyosin away from the actin binding sites
ii. Allows myosin heads to attach and produce contraction
troponin
Region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere.
M line
Narrow region in center of each A band that contains thick filaments but no thin filaments
H zone
Lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each
I band
Dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.
A band
Narrow, plate-shaped regions of dense material that separate one sarcomere from the next.
Z disc
a. Filaments inside a myofibril do not the entire fiber length but are arranged in these functional units
sacromere
i. Individual molecules join and twist into a helix to form a filament
ii. each actin molecule has a myosin binding site where a myosin head can attach
iii. thin filament
actin
i. Acts as a motor protein in all types of MT
ii. Each molecule is shaped like two golf clubs twisted together with the tails of the molecule point toward the M line in the center of the sarcomere and form the shaft of the filament
iii. Have two binding sites: actin and ATP
1. ATP binding functions as ATPase (produces energy for muscle contraction)
iv. thick filament
myosin
a. Transverse tubule and two terminal cisternae on either side
triad
a. Dilated end sacs of the sarcoplasmic reticulum that butt against the T-tubules from both sides
b. large amout of calcim is stored
terminal cisternae
what happens when action potential travels along sarcolemma and enter T-tubules
it causes a release of Ca⁺⁺ ions from the sarcoplasmic reticulum (terminal cisternae) into the sarcoplasm which initiates muscle contraction
muscle plasma membrane
sacrolemma
a. A broad flat sheet that attaches sheet-like muscles needing a wide area of attachment
aponeruosis
rope like band, connects muscle to bone
tendon
a. Protein that contains oxygen used by the mitochondria for ATP production
b. In sarcoplasm
myoglobin
muscle fibers formed from myoblasts cannot undergo
mitosis
b. Mesodermal cells
c. Where embryonic development skeletal muscle fibers arise from
myoblasts
once fusion occurs in from myoblasts what happens
muscle fiber loses its ability to undergo cell division
an overcoat of dense irregular CT that surrounds the entire muscle
endomysium
dense irregular CT that surrounds groups of muscle fibers called fascicles
perimysium
fine sheath of CT composed of reticular fibers surrounding each muscle fiber
epimysium
dense sheet of CT lines body wall and limbs, supports/surrounds muscles and other organs of the body
i. Allows free movement
ii. Contains blood vessels, nerves and lymphatic vessels
iii. Holds muscles with similar functions together
fascia
multinucleated, longitudinal, and striated
skeletal
one nucleus, striated, branched, and intercalated discs
cardiac
one nucleus, spindle shaped, and no striations
visceral ( smooth muscle)
ability to respond to certain stimuli by producing electrical signals called action potentials; nervous tissue
electrical exciability
ability to contract and shorten in length when stimulated by an action potential
Contractility
ability ot stretch without damage
extensibility
ability to return to its original shape and resting length after contraction or extension
elasticity
the fiber is stimulated at 80-100x per sec, it does not relax at all
Fused (complete) tetanus
Unfused (incomplete) tetanus
when a skeletal muscle fiber can only partially relax b/t stimuli at a rate of 20-30x per sec, a sustained but wavering contraction occur
a. Stimuli arriving at different times causes larger contractions
wave summation
b. without oxygen
c. pyruvic acid molecules converted to lactic acid
anaerobic glycosis
what happens to lactic acid
transferred to liver by blood and converted back to glucose/pyruvate
Glucose broken down into two molecules of pyruvic acid by
glycolysis