3. Muscle Physiology Flashcards
all muscle share some terminology, prefixes ____, ____, ____ refer to muscle:
- myocardium:
- sarcoplasm:
- sarcolemma:
myo, mys, sarco
- myocardium: heart muscle
- sarcoplasm: muscle cell cytoplasm
- sarcolemma: muscle membrane
all muscle cells are elongated and referred to as ______
muscle fibers
muscle contraction depends on two kinds of ______
myofilaments
3 Types of Muscle Tissues:
- Smooth muscle
- Cardiac muscle
- Skeletal muscle
Muscle Tissues differ in the (4)
- structure of their cells
- their body location
- their function
- means by which they are activated to contract
- has no striations
- spindle-shaped cells
- single nucleus
- involuntary
- found mainly in the walls of ______ organs
- weak and slow
smooth muscle
hollow
- found only in the heart
- has striations
- usually has single nucleus
- joined to another muscle cell at an _________
- involuntary
- strong, quick, and continuous
cardiac muscle,
intercalated disc
- is packaged into _________: organs that are attached to bones and skin
- most muscles are attached to bones by _______
- longest muscle cell fibers (muscle cell=muscle fiber)
- cells are multinucleate
- striation
- voluntary
- contract rapidly, tire easily, powerful
skeletal muscle
tendons
location of :
- smooth
- cardiac
- skeletal muscle
- smooth - wall of hollow organs, vessel, respiratory passageways
- cardiac - wall of heart
- skeletal - attached to bones
- tapered at each end, branching networks, nonstriated
- involuntary
- produces peristalsis; contracts and relaxes slowly; may sustain and contraction
smooth muscle
- branching networks; special membranes (intercalated disks) between cells; single nucleus; lightly striated
- involuntary
- pumps blood out of heart; self-excitatory but influenced by nervous system and hormones
cardiac muscle
- long and cylindrical; multinucleated; heavily striated
- voluntary
- produces movement at joints; stimulated by nervous system; contracts and relaxes rapidly
skeletal muscle
All muscle share four main characteristics
- excitability
- contractility
- extensibility
- elasticity
ability to receive and response to stimuli
excitability
ability to shorten forcibly when stimulated
contractility
ability to be stretched/extended
Extensibility
ability to recoil to resting length
elasticity
four muscle functions
- producing movement
- maintaining posture and body position
- stabilizing joints
- generating heat as they contract
skeletal muscle is an organ made up of different tissues with three features which are:
- nerve and blood supply
- attachments
- connective tissue sheaths
tissue responsible for the nerve and blood supply
deep fascia
musle attach to bone in at least two points (2) and these attachments can be ___(2)
two points of muscle to bone attachments:
1. insertion: attach to movable joint
2. origin: immovable or less movable
direct and indirect
two types of attachments and give examples
- direct - epimysium fused to periosteum of bone or perichondrium of cartilage
- indirect - connective tissue wrappings extend beyond muscle as tendon or aponeurosis
In an indirect attachment, connective tissue wrappings extend beyond muscle as ropelike ______ or sheetlike _______
tendon
aponeurosis
connective tissue sheaths of skeletal muscles (3)
epimysium, perimysium, and endomysium
- While the deep fascia does not directly envelop individual muscle fibers or fascicles like the perimysium and endomysium, it surrounds and separates groups of muscles, acting as a strong, continuous layer of connective tissue. It provides support and compartmentalization, separating muscle groups and allowing for coordinated movement.
Organization Levels of Skeletal Muscles (5)
- skeletal muscle
- muscle fascicle
- muscle fiber
- myofibril
- sacromere
surrounded by epimysium and contains muscle fascicles
skeletal muscle
surrounded by perimysium and contains muscle fiber
muscle fascicle
surrounded by endomysium and contains myofibrils
muscle fiber
surrounded by sacroplasmic reticulum and consists of sacromeres (z line to z line)
myofibril
sacromere contains (2) filaments
thick (myosin) and thin (actin) filaments
- are long, cylindrical cells that contain multiple nuclei beneath the sarcolemma
- many mitochondria
- sacroplasm contains many glycosomes and myoglobin
skeletal muscle cell
sacroplasm contains many _______ for glycogen storage and _________ for oxygen storage
glycosomes
myoglobin
______ is plasma membrane of the muscle cell
______ is the cytoplasm of the muscle cell
sarcolemma
sacroplasm
skeletal muscle cells has modified organelles: (3)
- myofibrils
- sacroplasmic reticulum
- transverse tubules (T tubules)
- densely packed, rod-like elements
- 80% of cell volume
- exhibit striation
myofibrils
striation of myofibril is due to perfectly aligned repeating series of dark ______ and light _______
dark A band and light I band
myosin molecule chains (2) and its components
- heavy chain: tail and head
- light chain: 18-kDA and 22-kDA
two binding sites of the myosin head
- actin-binding site
- ATP-binding site
actin parts (3)
- actin
- tropomyosin
- troponin complex
troponin complex components (3)
- Tnl - inhibitory subunit that binds to actin
- TnT - binds to tropomyosin
- TnC - binds calcium ions
two types of actin
- G actin (globular)
- F actin (fibrous)
other proteins help from the structure of the myofibril: (3)
- elastic filament (titin)
- dystrophin
- nebulin, myomesin, c proteins
elastic filament is composed of _______
titin
protein that
- holds thick filaments in place
- helps recoil after stretch
- resist excessive stretching
elastic filament
protein that links thin filaments to proteins of sarcolemma
Dystrophin
proteins that bind filaments or sarcomere together which maintain alignment of sacromere
Nebulin, myomesin, C proteins
sacromere components (5)
- myosin
- actin
- titin
- M line
- Z disc
- network of smooth endoplasmic reticulum surrounding each myofibril
- pairs of terminal cisternae from perpendicular cross channels
- functions in the regulation of intracellular Calcium levels
Sacroplasmic Reticulum
- continuous with the sarcolemma
- penetrate the cell’s interior at each a band and I band junction
T tubules
T tubules associate with the paired terminal cisternae to from _________ that encircle each sacromere and provides signals for muscle contraction
triads
In Triad:
- _____ acts as voltage sensors
- _____ are known to be calcium channels
- T tubules proteins
- Sacroplasmic reticulum proteins
formulated sliding filament theory of contraction
Hugh Huxley, 1954
stated that during contraction the thin filaments slide past the thick filaments so that the actin and myosin filaments overlap to a greater degree
sliding filament theory of contraction
What causes the filaments to slide?
binding of calcium sa TnC of tropomyosin
sequence of events involvd in the sliding of the actin filaments during contraction (4)
- Cross bridge attachment (myosin attaches to actin)
- Power stroke (ADP and Pi released from myosin)
- Cross bridge detachment (ATP binds to myosin)
- Cocking of myosin heads (ATP hydrolysis/dephospho)
four steps that must occur for skeletal muscle to contract
- nerve stimulation
- action potential must be generated in sacrolemma
- action potential must be propagated along sacrolemma
- intracellular Ca2+ level must rise briefly
1 and 2 occur at neuromuscular junction
3 and 4 link electrical signals to contraction
Requirement for Skeletal Muscle Contraction (2)
- activation
- excitation-contraction coupling
what do you call the requirement for skeletal muscle contraction where neural stimulation at neuromuscular junction occurs?
activation
is the requirement for skeletal muscle contraction that generates and propagates an action potential along the sarcolemma and the final trigger (a brief rise in intracellular ________)
Excitation-contraction couping
- Ca2+ levels
Neuromascular Junction
- neurotransmitter
- destroys neurotransmitter
- neurotransmitter receptor
- acetylcholine
- acetylcholin-esterase (AchE)
- Nicotinic acetylcholine receptor
two calcium channels
- __________ - present in T-tubule
- __________ - present in sacroplasmic reticulum
both channels release calcium sa sacroplasm cause the increase of calcium concentration
- Dihydropyridine - L-type calcium channel (DHP)
- Ryanodine receptor channel (RyR)
- autoimmune disease in which a person produces antibodies to the acetylcholine receptors on skeletal muscle fibers
- the number of these receptors decreases, and the synaptic transmission between motor neurons and the muscle fiber becomes less effective
Myasthenia gravis
- results from the consumption of exotoxin
- symptoms:
- double vision
- blurred vision
- droopy eyelids
- slurred speech
- difficulty swallowing
- dry mouth
- muscle weakness
What bacteria is responsible for this disease?
Botulism
Clostridium botulinum
what happens in botulism?
the toxin, paralyzes muscles by _____________ from the motor neurons, is also injected in a a certain facial muscles to eliminate frown lines in _______ treatments
blocking the release of acetylcholiene
“Botox” treatment
what is a motor unit? what are the two types?
it composed of one motor neuron and its muscle fibers (also the neuromuscular junction)
- large motor unit
- small motor unit
- simplest contraction resulting from a muscle fibers response to a single acion potential from a motor neuron
- muscle fiber contracts quickly, then relaxes
- maybe strong or weak, depending on the number of motor units activated
muscle twitch
twitch can be observed and recorded as _______, a graphic recording of mechanical contractile activity. _______ is line recording contraction activity.
Myogram
Tracing
three phases of Muscle twitch
- latent period
- period of contraction
- period of relaxation
______ phase of muscle twitch happens during the events of excitation-contraction coupling occur or the time between stimulus and start of contraction
in this phase, ____ muscle tension is seen
latent period, no muscle tension is seen
phase of muscle tension where cross bridge formation happens and tension increases (______ ms)
period of contraction (10-100 ms tension)
phase of muscle twitch where Ca2+ reenter into sacroplasmis reticulum and actin slides back into place. In this phase the thension declines to ______
period of relaxation
zero (0 ms)
- reponse of a muscle to a single threshold stimulus
- muscle contracts faster than it relaxes
Muscle twitch
Muscle contracts ________ (faster/slower) than it relaxes
faster
true or false
muscle contraction and relaxation is longer compared to the action potential
true
- mas paspas si action potential that is why it is possible to have multiple twitches *
Graded Muscle Responses
normal muscle contraction is relatively smooth, and strength varies with
needs
graded muscle responses vary strength of contraction for different demands and this is required for proper control of skeletal movement
responses are graded by (2)
- changing frequency of neural stimulation
- changing strength of neural stimulation
muscle response to change in stimulus frequency:
- ___________ results in single contractile response (ex. muscle twitch)
- __________ results if two identical stimuli are received by a muscle in rapid succession
- ________ : unfused
- ________ : fused
- Single stimulus
- wave (temporal) summation
- incomplete tetanus
- complete tetanus
complete tetanus can cause ________, where muscle is unable to contract and its tension drops to zero because of ATP deficiency
muscle fatigue
a single action potential in a muscle fiber produces a __________ and repeated stimulation is needed to produce sustained and longer duration of contraction muscles
muscle twitch
muscle fibers can respond to repeated stimuli before they are fully relaxed, this is called _____-
twitch summation
contractions repeated before complete relaxation, leads to progressively strong contractions
wave (temporal) summation
frequency of stimulation allows only incomplete relaxation
unfused (incomplete) tetanus
frequency of stimulation allows no relaxation
fused (complete) tetanus
muscle response to change in stimulus strength
__________ - when stimulus is sent to more muscle fiber leading to more precise control
What are the types of stimulus involved? (3)
Recruitment (multiple motor unit summation)
- subthreshold stimulus
- threshold stimulus
- maximal stimulus (all motor units have been recruitment)
stimulus not strong enough, so no contractions seen
subthreshold stimulus
strongest stimulus that increases maximum contractile force
maximal stimulus
__________is stimulation of additional motor units for an increased strength of contractions
_________ is required for contraction of skeletal muscle
recruitment (multiple motor unit summation)
recruitment of all motor units
the bigger the muscle fiber the ________ tension and ______ motor units are needed
greater and manier
minimal strength needed to start a contraction
threshold stimulus
The strength of a muscle contraction is determined by the ______ and _________ that are recruited to perform the specific task.
size and number of motor units
motor units operate according to ____________ law which means that when a motor unit is stimulated, all of the muscle fibers in that unit will contract. Therefore, the larger the motor unit being recruited, the _________ the force is generated.
all-or-none
greater
Factors Affecting Muscle Tension (3)
- Motor Unit Recruitment
- Size of the muscle
- Muscle Twitch Summation
some muscle fibers are always active to maintain muscles, even when no movement is taking place
Baseline muscle tone
activation of more motor units to increase tension in the muscle as the load increases, i.e. more force needed
Motor Unit Recruitment
