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
Tension
The force generated by a muscle
Load
The resistant force placed on a muscle
Isotonic Contractions
tension generated is sufficient to overcome the load
(contraction that produces a movement)
-muscle changes in length
-a movement is preformed
Two Types:
a. Concentric- muscles shortens as it produces tension
b. Eccentric- muscle lengthened as it generates tension
Isotonic Contractions: Concentric movement
muscle shortens as it produces tensions
ex: when you pick up a box the muscle shortens
Isotonic Contractions: Eccentric movement
muscle is lengthened as it generates tension
ex: muscle is lengthened by triceps when you put a box down
- muscle is tight when lengthening
Isometric Contractions
tension generated is insufficient to overcome the load
- muscle does not change in length
- no movement occurs
ex: wall sits; quadriceps is isometric contraction, its not lengthening or shortening when doing a wall sit
Direct Phosphorylation
Method of ATP regeneration
ADP + P(creatine) –> ATP
- Creatine takes phosphate group from ATP, and adds it to ADP, directly phosphorylating ADP to turn it back to ATP
-Creatine phosphorylates ADP to rebuild ATP
-lasts 30 seconds
After 30 seconds, a muscle must make new ATP via one of the following 2 processes:
- Aerobic Respiration
2. Lactic Acid Fermentation
Aerobic Respiration
Method of ATP regeneration performed by mitochondria summary equation: C6H12O6 + 6O2 --> 6H2O + 38 ATP -use oxygen to breakdown glucose into 6 individual carbons -requires oxygen -slow -huge ATP yield (great amount of ATP produced)
Lactic Acid Fermentation
Method of ATP regeneration performed by cytosol summary equation: glucose --> 2 ATP + Lactic Acid -anaerobic (does not involve oxygen; doesn't use an organelle it uses cytosol so it doesn't need oxygen) -fast -low ATP yield -Lactic Acid causes fatigue
When to use Aerobic Respiration?
if you keep activity at the level or below aerobic threshold you’re using aerobic respiration
When to use Lactic Acid Fermentation?
Go beyond anaerobic threshold
-muscle will fatigue
Type of Skeletal Muscle Fiber: Slow Oxidative Fibers
- use ATP slowly
- thinnest fibers; weakest
- have many mitochondria (organelle that needs oxygen to make ATP) + lots of myoglobin (protein that stores oxygen)
- strictly aerobic ( use aerobic respiration)
- tireless (does not build lactic acid)
Type Of Skeletal Muscle Fiber: Fast Glycolytic Fiber
- use ATP quickly
- thickest fiber (strongest); thicker the fiber the more myosins + actins are in it
- few mitochondria, little myoglobin, lots of glycogen
- use lactic acid fermentation
- tire easily (make lactic acid); produce a lot of force quickly
Type Of Skeletal Muscle Fiber: Fast Oxidative Fibers
- use ATP quickly
- intermediate on thickness (thicker than oxidative, thinner than glycolytic)
- intermediate amounts of mitochondria + myoglobin
- mainly aerobic, but can be forced to use fermentation
Smooth Muscle: Differences compared to Skeletal
- Innervated by autonomic nervous system; is strictly involuntary
- Fibers are usually electrically connected to one another with GAP junctions (allowing large number of fibers to contract as a unit) (exceptions: multiunit smooth muscle(activate in small groups); in iris of eye, controls size of pupil))
- Neurotransmitters aren’t released at NMJ’s (neurotransmitter junctions); they get released to multiple fibers at once via diffuse junctions
- Smooth muscle is slow; latent period is at least 100 times longer than skeletal muscle
- No troponin or Tropomyosin blocking actin; myosin must be activated to bind to actin
a. Calcium, when released by SR, finds to calmodulin (instead Troponin)
b. Calmodulin activates myosin light-chain kinase
c. Myosin light-chain linase activates myosin, which bonds to actin - Thick + thin filaments aren’t arranged into sarcomeres, fibers not striated; this means smooth muscle can generate force when its fibers are stretched or shortened
