Chapter 9: Muscle Tissue Flashcards
Skeletal Muscle Tissue
muscle tissue attached to skeleton
Muscle Fibers (muscle cells)
-enormous
-elongate
-multinucleate (multiple nucleus) (not in the middle, need to be pushed to the side or top)
-striated (the stripes) (where the action happens) (tighten muscle, produce movement)
-can be used voluntarily
-can generate a wide range of forces
-can generate force quickly
-tires easily
(generates small or lots of force in a short amount of time)
Cardiac Muscle Tissue
found in the walls of your heart
- fibers are:
- enormous
- elongate
- multinucleate
- striated
- branch extensively (cells in a heart chamber act/work as a unit)
- strictly involuntary
Smooth Muscle Tissue
found in “hollow organs” (stomach, intestines)
- normal size
- no striations
- strictly involuntary (cant control consciously, no control over them)
- generate force slowly
- tireless
Characteristics of Muscle Tissue
- Excitable
- Contractile
- Can shorten and Lengthen
- Elastic
Characteristics of Muscle Tissue: Excitable
responsive to stimuli
Stimuli———————— —
Characteristic of Muscle Tissue: Contractile
performs contraction
contraction- generation of tension (when a muscle gets tight)
Characteristic of Muscle Tissue: Shorten and Lengthen
can shorten and lengthen (to produce movement)
Characteristic of Muscle Tissue: Elastic
stop stimuli to go back to resting position
Anatomy of Skeletal Muscle
-each fiber is wrapped with an Endomysium (found inside muscle) (helps insulate skeletal muscles from other skeletal muscles)
-each fascicle is wrapped with a Perimysium
-each muscle is wrapped with a Epimysium
-muscles are wrapped into groups by Deep Fascia:(contains nerves to stimulate skeletal muscle fibers)
(blood vessels)
epi= entire muscle
peri= fossicle
endo=muscle
Anatomy of Skeletal Muscle Fiber
- Sarcolemma- (plasma membrane) creates action
- Sarcoplasm (cytoplasm)
- contains Glycogen (polysaccharide)
- contains myoglobin, (protein in muscle that stores oxygen)
- contains a sarcoplasmic reticulum- (endoplasmic reticulum) stores calcium
- contains myofibrils, the contractile units of the muscle fiber (produce tension/ movement)
Anatomy of a Myofibril
-contains striations
dark bands: A bands
light bands: I bands
-Sarcomere- part of myofibril from one z disc to the next
-contain myofilaments: Thick (red) and Thin (blue) filaments
Myofilaments: Thick and Thin
-Thick Filaments are made out of a protein called Myosin (tail with 2 heads)
- Thin Filaments made of several proteins:
1. Actin- when bound to by myosin, tension is generated
2. Tropomyosin- blocks myosin from binding to actin
3. Troponin- keeps tropomyosin in place binding actin
the “key” to the troponin “lock” is Calcium
(only thing to allow myosin + actin to get together to produce tension + movement)
Excitation-Contraction Coupling
- At a Neuromuscular Junction (NMJ), the neurons axon terminal releases the neurotransmitter acetylcholine (Ach) to the fibers motor end plate
- In response to Ach, the motor end plate creates an Action Potential which travels to the fibers sarcoplasmic reticulum (SR)
- In response, the SR releases calcium to the sarcomeres, and tells troponin to allow myosin to bind to actin
Sliding Filaments Mechanism
uses tension to produce movement
- myosin binds to actin
- myosin performs power (working) stroke
- Z disc are pulled closer together
- Sarcomeres shorten - myosin lets go of actin to bind to ATP
- myosin “spends” the ATP to reattach to actin
Twitch
the response of a muscle fiber to a single impulse (one release of Ach)
3 Parts of a Twitch
- Latent period- (2-3 milliseconds) the time necessary to get myosin to bind to actin
- Contraction period- (20-30 ms) as myosin bind to actins, tension is produced
- Relaxation period- as SR takes calcium back from the Sarcomeres myosin’s + Actins uncouple
3 Parts of a Twitch: Latent Period
(2-3 milliseconds)
-the time necessary to get myosin to bind to actin
3 Parts of a Twitch: Contraction Period
(20-30 ms)
as myosin’s bind to actins, tension is produced
3 Parts of a Twitch: Relaxation Period
as SR takes calcium back from the Sarcomeres myosin’s + actins uncouple
Wave Summation
process of combining summating twitches in order to get a long enough contraction time to produce a movement (a graded response)
-twitch multiple times in a row
Tetanus
a state of constant contraction
- wont have relaxation periods but needs to be in this state have movement)
- the muscle is in tetanus while doing a graded response
- use wave summation to get in the state tetanus (need a high frequency)
Motor Unit
a neuron and all of the muscle fibers it innervates
-a neuron can control more than 1 muscle fiber
Motor Unit Summation
one motor unit enlists the help of other motor units by sending larger impulses to its muscle fibers