BIO 201- CH 9 Lecture
What are the characteristics of skeletal muscle?
- attach and cover the bony skeleton - has striations (obvious stripes) - only muscle tissue under voluntary control - responsible for overall body motility - contracts rapidly, tires easily
What are the four special characteristics that help muscle tissues perform their duties?
- excitability - contractility - extensibility - elasticity
What are characteristics of cardiac muscles?
- forms the walls of the heart - is striated - is involuntary - contracts at steady rate set by heart's pacemaker - contractions can speed up in response to bodily needs
What are the characteristics of Smooth muscle?
- found in the walls of hollow visceral organs - is not striated - is involuntary muscle - forces food and other substances through internal body channels - produces slow, sustained contractions
What are the muscle's four basic important functions that they perform?
- movement - maintaining body posture - stabilizing joints - generating heat
What are the two functions of the sarcoplasmic reticulum?
- regulate intracellular levels of Ca - forms terminal cisternae at the A band-I band junction
What skeletal muscle structures can be seen without a microscope?
- skeletal muscle tissue - blood vessels - nerve fibers - connective tissue - attachments
At resting potential, the inside of the sarcolemma is negative at _____mv.
-70 mv
What are the three major connective tissue sheaths?
-epimysium -perimysium -endomysium
What are the three different types of muscle tissue?
1. Skeletal 2. Cardiac 3. Smooth
What are the steps of activation of a muscle fiber cell?
1. action potential in axon arrives at axon terminal 2. Ca^2+ enters the axon 3. synaptic vesicles fuse with the axonal membrane 4. ACh is released into the synaptic cleft 5. ACh diffuses across the synaptic cleft 6. ACh binds to receptor proteins 7. ACh is broken down
What are the steps of contraction?
1. action potential reaches T-tubules 2. terminal cisternae release Ca^2+ 3. Ca^2+ binds to troponin 4. contraction occurs across cross bridges 5. removal of Ca^2+ 6. tropomyosin restored
What are the three steps involved in inducing a skeletal muscle cell to contract?
1. activation 2. propagation of an action potential 3. increase in intracellular Ca^2+ levels
What are the steps to anaerobic glycolysis?
1. bulging muscles compress the blood vessels within them 2. blood flow and oxygen delivery is impaired 3. oxygen deficit results 4. pyruvic acid is converted to lactic acid 5. this produces only 2 ATPs/glucose but it works without oxygen
What two ways are muscle responses graded?
1. changing the frequency of stimulation 2. changing the strength of stimulation
What are the four steps of the cross bridge cycle?
1. cross bridge formation 2. power stroke 3. cross-bridge detachment 4. cocking of the myosin head
What are the three phases to a muscle twitch?
1. latent period 2. period of contraction 3. period of relaxation
Overview of the Contraction of Skeletal Muscle
1. nerve impulses reach the axon terminal 2. Ca2+ channels open 3. synaptic vesicles fuse w/axonal membrane 4. ACh is released 5. ACh diffuses 6. ACh binds 7. Na+ channels open causing the motor end plate to depolarize 8. Ca2+ is released 9. Ca2+ causes troponin/tropomyosin to move from active site 10.myosin head creates a cross bridge 11.ACh is destroyed 12.sarcolemma is repolarized 13.Ca2+ is removed from the muscle fiber
What are the five steps of the propagation of an action potential?
1. resting potential 2. depolarization 3. action potential 4. repolarization 5. Na/K pump
What are unique characteristics of smooth muscle fibers?
1. spindle-shaped 2. uninucleate 3. much smaller than skeletal muscles 4. lack coarse connective tissue sheaths
Contractions can increase due to two factors, what are these factors?
1.increased availability of Ca2+ in the sarcoplasm 2.muscle enzymes become more efficient because heat is increased as the muscles contract
The diameter of a skeletal muscle fiber is ____ to ____ um (10x an average body cell).
10 to 100
The Creatine Phosphate (CP) is used up in less than ____.
20 seconds
The length of a skeletal muscle fiber is up to ______cm.
30
women's skeletal muscle makes up ___% of their body mass. While men's make up ___% of their body mass. Why?
36% / 42% because of testosterone
During aerobic respiration, one glucose molecule makes ____ ATP molecules.
36-38
Muscles only store about ____ seconds of reserve of ATP
4-6 seconds
By age 80, ___% of muscle mass is lost.
50%
When muscles contract vigorously and contractile activity reaches about ____% of maximum anaerobic glycolysis will occur.
70%
During rest and light to moderate exercise, ___% of ATP used is supplied by aerobic respiration.
95%
bands of both thin and thick filaments in a myofibril
A band
During depolarization of propagation of an action potential, what causes the sodium channels to open?
ACh from the axon
As we begin to exercise, the demand for ____ soars.
ATP
_____ is the only source of energy used directly for contractile activity
ATP
How is each muscle fiber produced?
By the fusion of hundreds of embryonic cells.
Short activities such as sprinting or weight lifting require a surge of power and rely on ____ stores in the muscle.
CP and ATP
a lighter region in the midsection of the A band that is made up of only thick filaments
H zone
bands of only thin filaments in a myofibril
I band
How do muscle tissues differ?
In structure, location, function, and means of activation
Muscles can attach two different ways. Which way is more common?
Indirect attachment because of its durability and small size.
Muscle that cannot ordinarily be consciously controlled
Involuntary muscle
a dark band of proteins that bisects the H zone and anchors thick filaments
M line
During the resting potential of propagation of an action potential, the sarcolemma is relatively impermeable to ___ and ____.
Na and K
The ionic concentration of the resting state is restored by the ____. What step is this in propagation of an action potential?
Na/K pump. the last step
During depolarization, ___ enters the cell, causing the inside to become more positive.
Na^+
Once initiated, can the action potential be stopped?
No
A type of muscle tissue composed of cylindrical, multinucleate cells with obvious striations that forms the major muscles of the body
Skeletal muscle
How does the function movement affect each type of muscle: skeletal, cardiac, and smooth?
Skeletal- locomotion and manipulation Cardiac- movement of blood Smooth- movement through hollow organs
A type of muscle tissue composed of nonstriated, uninucleate cells found mainly in the walls of hollow organs
Smooth muscle
What conducts impulses to the deepest regions of the muscle?
T tubules
What greatly increases the muscle cell's surface area?
T tubules
extension of the sarcolemma in muscle cells that protrudes deeply into the muscle cell
T tubules
Muscle that is under strict, conscious nervous control
Voluntary muscle
protein disk that anchors thin filaments and divides two sarcomeres in a myofibril
Z disc
What is an example of complete tetanus?
a person lifting a car off of another person
What is the appearance of a myosin molecule?
a rod-like tail and two globular heads made of polypeptides
How many myosin molecules do each thick filament contain?
about 300 myosin molecules
At the neuromuscular junction, the synaptic vesicles release the neurotransmitter _____ into the ______.
acetylcholine (ACh) into the synaptic cleft
What are thin filaments composed of?
actin
a depolarization event that is conducted along the membrane of a muscle cell or nerve fiber that creates an electrical current
action potential
organic molecule that stores and releases chemical energy for use in the body cells of all living things
adenosine triphosphate (ATP)
the length of time a muscle can contract using the aerobic pathways
aerobic endurance
During rest and light to moderate exercise, 95% of ATP used is supplied by _____.
aerobic respiration
Prolonged activities where endurance not power is the goal such as a marathon or jogging depend mostly on ____.
aerobic respiration
The most efficient respiration process is the ____.
aerobic respiration
respiration in which oxygen is consumed and glucose is broken down entirely to produce water, carbon dioxide, and large amounts of ATP, also call cellular respiration
aerobic respiration
embryonic growth factor that stimulates the clustering of acetylcholine receptors at the motor end plate
agrin
What is propagation of an action potential as related to the steps of inducing a skeletal muscle to contract?
an electrical current is generated along its sarcolemma
When muscles contract vigorously and contractile activity reaches about 70% of maximum ___ will occur.
anaerobic glycolysis
conversion of glucose to lactic acid to produce ATP when sufficient oxygen is not available to perform aerobic respiration
anaerobic glycolysis
On and off activities that require periodic bursts of activity such as soccer and tennis are mostly fueled by ____.
anaerobic respiration
the point at which muscle metabolism converts to anaerobic glycolysis
anaerobic threshold
Where do T tubules occur?
at the A band-I band junction
Where does activation occur?
at the neuromuscular junction
During activation, axons of the motor neurons enter muscles and _____.
branch profusely
When does sarcopenia begin?
by age 30
A type of muscle tissue composed of branching cells that are generally uninucleate that forms the walls of the heart
cardiac muscle
pouch-like infoldings in the sarcolemma of smooth muscle fibers that act as calcium ion reservoirs
caveolae
During action potential, what causes Na channels of an adjacent patch of sarcolemma to open?
charge reversal of the initial patch of sarcolemma
deep layer of smooth muscle fibers that run around the organ
circular layer
a situation in which all evidence of muscle relaxation disappears and the muscle contraction fuses into a smooth sustained contraction plateau
complete tetanus
Individual muscle fibers are wrapped and held together by ___________.
connectie tissue sheaths
the ability to move by shortening forcibly
contractility
During the _____, thin filaments slide past thick ones so that the actin and myosin filaments overlap to a greater degree.
contraction
ADP + creatine phosphate = ____
creatine + ATP
organic high-energy molecule stored in muscles that is tapped to regenerate ATP
creatine phosphate (CP)
the sequence of cyclical events in which myosin heads on a thick filament attach to the actin on thin filaments and pull them towards the M line
cross bridge cycle
The globular heads of myosin molecules attach to the active sites of the actin subunits to form _____.
cross bridges
What acts as motors to generate the tension developed during muscle contraction?
cross bridges
the area where an axon delivers an impulse to a smooth muscle fiber made up of a varicosity, wide synaptic cleft, and the smooth muscle fiber
diffuse junction
epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage
direct attachment
What are the two different ways that muscles can attach?
direct attachment and indirect attachment
What component of thick filaments allow the filament to spring back into shape after being stretched?
elastic filaments
the ability of a muscle cell to recoil and resume its resting length after being stretched
elasticity
sheath of fine areolar connectie tissue that surrounds each individual muscle fiber
endomysium
sheath of dense irregular connective tissue that surrounds the whole muscle
epimysium
the ability to receive and respond to stimuli
excitability
Propagation of an action potential and increase in intracellular Ca levels (steps 2 and 3 in muscle contraction) are called ______.
excitation-contraction coupling
the sequence of events by which the transmission of an action potential along the sarcolemma leads to the sliding of myofilaments
excitation-contraction coupling
the ability to be stretched or extended
extensibility
bundle of nerve or muscle fibers bound together by connective tissue
fascicle
What do T tubules impulses signal?
for the release of Ca^2+ from the adjacent terminal cisternae
granule of stored glycogen that provide glucose during periods of muscle cell activity
glycosome
Sarcoplasm is similar to that of other cells but has unusually large amounts of ____ and ______.
glycosomes and myoglobin
variations in the degree of muscle contraction by changing either the frequency or strength of the stimulus
graded muscle response
Skeletal muscles fiber are _______ cells.
huge
a situation in which a muscle contraction is sustained but quivering
incomplete tetanus
What is the final trigger for contraction?
increase in intracellular Ca^2+ levels
Muscle's connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis connecting to bone, cartilage, or other muscle
indirect attachment
attachment of a skeletal muscle to a bone that moves during muscular contraction
insertion
contraction of a muscle in which the muscle does not shorten but its internal muscle tension increases
isometric contraction
What are the two types of muscle contraction?
isometric contraction and isotonic contraction
contraction of a muscle in which muscle tension remains constant at a given joint angle and load, and the muscle shortens
isotonic contraction
Large, weight bearing muscles (hips, thighs) with less precise movements have ____.
large motor units
period of time between stimulation and the onset of muscle contraction, during which excitation-contraction coupling is taking place
latent period
What is an example of isotonic contraction?
lifting a 10 lb. book
Which layer of the smooth muscle fiber is responsible for shortening and dilating of the organ?
longitudinal layer
superficial layer of smooth muscle fibers that run along the long axis of the organ
longitudinal layer
What are the two sheets of fibers at right angles to each other that smooth muscle fiber is organized into?
longitudinal layer and circular layer
the strongest stimulus that increases contractile force
maximal stimulus
At the neuromuscular junction, the sarcolemma forms the ______.
motor end plate
highly folded portion of the sarcolemma that contains ACh receptors
motor end plate
a motor neuron and all of the muscle cells it stimulates
motor unit
a state of physiological inability to contract in which a muscle's tension drops to zero
muscle fatigue
A skeletral or smooth muscle cell
muscle fiber
the force exerted by a contracting muscle on some object
muscle tension
What makes up nearly half of the body's mass?
muscle tissue
What is very important to joint stability?
muscle tone
If only a single stimulus occurs, ____ will result.
muscle twitch
the response of a muscle to a single, brief threshold stimulus
muscle twitch
What are the three prefixes that refer to muscle?
myo- mys- sarco-
embryonic mesoderm cells from which all muscle cells develop
myoblasts
rod-like bundle of contractile filaments (myofilaments) found in muscle fibers
myofibril
What accounts for about 80% of the cell's volume?
myofibrils
filaments of actin or myosin that form myofibrils
myofilament
a red protein found in muscle fibers that stores oxygen
myoglobin
What are thick filaments composed of?
myosin
During activation, each set of axonal branches forms a __________ with a single muscle fiber.
neuromuscular junction
region made up of the axon terminals, synaptic clefts, and motor end plates where a motor neuron comes into close contact with a skeletal muscle
neuromuscular junction
Are muscle twitches the way our muscles normally operate?
no
attachment of a skeletal muscle to a bone that remains relatively fixed during muscular contraction
origin
What are the two places that most skeletal muscles span joints and are attached to bone or structures?
origin and insertion
idea that forcing a muscle to work hard promotes increased muscle strength and endurance
overload principle
As long as a muscle cell has enough ____, it will form ATP by the aerobic pathway.
oxygen
sheath of fibrous connective tissue that bundles muscle fibers into fascicles
perimysium
period of time during which cross bridges form, muscle tension increases, and the muscle shortens
period of contraction
period of time during which Ca2+ is reabsorbed into the sarcoplasmic reticulum and the muscle tension decreases to zero
period of relaxation
The force of a contraction is controlled by _____ or multiple motor unit summation.
recruitment
_____ occurs from threshold stimulus to maximal stimulus.
recruitment
the phenomenon by which more and more motor units are incorporated into a muscle contraction as stimuli increase
recruitment
During the _____, thin and thick filaments overlap only slightly.
relaxed state
During what step of propagation of an action potential does K diffuse from the cell, restoring electrical polarity (resting potential) of the sarcolemma?
repolarization
What must occur before the muscle can be stimulated again?
repolarization
At the neuromuscular junction, as ACh is released from the axon, it travels to the ______ of the muscle fiber.
sarcolemma
At the neuromuscular junction, the _____ forms the motor end plate.
sarcolemma
the plasma membrane of a muscle fiber
sarcolemma
the smallest contractile unit of a muscle that consists of the region between two successive Z discs on a myofibril
sarcomere
the gradual loss of muscle mass that occurs with aging
sarcopenia
the cytoplasm of a muscle fiber
sarcoplasm
specialized smooth endoplasmic reticulum that surrounds each myofibril in muscle cells
sarcoplasmic reticulum
Skeletal muscles contain what two sets of intracellular tubules that participate in the regulation of muscle contraction?
sarcoplasmic reticulum and T tubules
When muscles contract, the sarcomeres ____.
shorten
smooth muscle contraction is similar to _____.
skeletal muscle contraction
Each _______ is a long cylindrical cell with multiple oval nuclei just beneath the sarcolemma.
skeletal muscle fiber
model that states that during muscle contraction, the thin filaments slide past the thick filaments so as to increase their degree of overlap
sliding filament model of contraction
Muscles that control fine movements (fingers, eyes) have _____.
small motor units
Unlike skeletal muscle, _____ muscle relies heavily on extracellular Ca2+ to trigger muscular contractions.
smooth
T tubules are notably absent from _____.
smooth muscle
Thick and thin filaments are arranged diagonally in ____.
smooth muscle
____ has no sarcomeres.
smooth muscle
____ lacks a structured neuromuscular junction
smooth muscle
nerve cells of the somatic (voluntary) nervous system
somatic motor neuron
Skeletal muscles are simulated (activated) by ______.
somatic motor neurons
Muscle fibers in a single motor unit are _____.
spread throughout the muscle
increased contraction in response to multiple stimuli of the same strength
staircase response
Within the steps of inducing a skeletal muscle cell to contract, how does activation occur?
stimulation by a nerve cell
gel-filled space between an axon terminal and the neuron or body cell it communicates with
synaptic cleft
At the neuromuscular junction, axon terminals contain many _____.
synaptic vesicles
small membranous sacs that contain a neurotransmitter to be released from a neuron by exocytosis
synaptic vesicles
What gives the muscles their striated appearance?
the A bands and I bands
What happens when muscles contract?
the insertion moves toward the origin
What are thin filaments composed of?
the protein actin
What are thick filaments composed of?
the protein myosin
What is the final trigger for muscle contraction?
the release of Ca^2+ ions by the terminal cisternae
Body strength per unit of muscle mass is _____ in both sexes.
the same
What are the two types of myofilament?
thick filaments and thin filaments
________ contain the active sites to which the myosin heads attach during contraction.
thin filaments
the weakest stimulus capable of producing an observable contraction
threshold stimulus
What is the primary function of wave stimulus?
to produce smooth, continuous muscle contractions
T tubules and their associated paired terminal cisternae form a ____.
triad
a successive grouping of terminal cisternae-T tubule-terminal cisternae that occurs between two sarcomeres
triad
Thin filaments also contain the proteins ______ and ______ that help control the myosin-actin interactions.
tropomyosin and troponin
What is an example of isometric contraction?
trying to lift a 2000 lb. car
a knob-like swelling of autonomic axons that contain mitochondria and synaptic vesicles
varicosity
phenomenon where rapid firing of neurons results in and summative effect in which successive muscle twitches grow stronger
wave stimulation
Stimulation of a single motor unit causes a ___ contraction of the entire muscle.
weak
sarcomeres are present and muscles are contracting by ___ of development in all muscle types.
week 7
When do muscles generate heat?
when they contract
