Unit 4: Ch 11 (Muscular Tissue) Flashcards
1
Q
Contraction period (of a twitch reaction)
A
- the muscle produces external tension creating a movement
2
Q
Excitation-contraction coupling process
- Description
- Steps
A
- Converts an electrical stimulus to a mechanical response
- Steps:
- Action potentials propagated down T tubules
- Ca ion released from terminal cisterns of sarcoplasmic reticulum
- Ca ion binds to troponin
- Shifting of tropomyosin results in exposure of active sites on actin
3
Q
Fast twitch
A
- AKA fast glycolytic, white, type IIb fibers
- Glycolysis and anaerobic respiration
- Produce powerful movements
- Large motor units
4
Q
Source of Immediate energy
A
- Myoglobin supplies oxygen for a limited amount of aerobic respiration
- Muscle borrows ATP requirements from phosphate groups (Pi) and transfers them to ADP
- 2 enzyme systems control these phosphate transfers
- Myokinase
- Creatine kinase
5
Q
Latent period
A
- The interval between the stimulus being applied and the contraction occurring
- The force generated during this time is the internal tension
- It isn’t visible on the myogram because it causes no shortening of the muscle
6
Q
Length-tension relationship
A
- A short or contracted fiber cannot contract very far leading to brief and weak contractions.
- A stretched fiber has reduced overlap between thick and thin filaments so the myosin heads are unable to get as good of a grip leading to weak contraction.
- Between the extremes, there is an optimum resting length at which the muscle contracts with the greatest force.
7
Q
Main pathways of ATP synthesis
A
-
Aerobic respiration
- Preferred method to make ATP in muscle cells
- Requires O, mitochondria, & glucose
- Final product is H2O & O
- Produces ATP in large quantities but slowly
-
Anaerobic fermentation
- Produces ATP without oxygen
- ATP yield is limited and the process generates a toxic by-product, lactate (lactic acid), which must be removed from the muscle and disposed of by the liver
- Produces ATP quickly
8
Q
Motor unit
A
- all the muscle fibers served by the terminal branches of an axon (somatic nerve fiber), these fibers contract in unison
- dispersed throughout a muscle, they cause a weak contraction over a large area
9
Q
Role of a motor unit
A
- the number of motor units activated adjust the strength and control;
- they also work in shifts so the muscle as a whole can sustain contraction
10
Q
muscle fatigue
and contributing factors
A
- The progressive weakness and loss of contractility that results from prolonged use of muscles
- Factors:
-
High-intensity/short-duration exercise
- Potassium ion accumulation
- ADP/phosphate accumulation
- Lactate
-
Low-intensity/long-duration exercise
- Fuel depletion
- Electrolyte loss
- CNS fatigue (ammonium absorption)
-
High-intensity/short-duration exercise
11
Q
Muscle fiber classifications
A
- Slow twitch are adapted for endurance and fatigue, rely heavily on oxidative metabolism, surrounded by dense capillaries, rich in mitochondria, and thin for oxygen diffusion.
- Fast twitch are adapted for quick responses. Has extensive sarcoplasmic reticulum for fast release and reabsorption of calcium. Relies on anerobic metabolism for quick production of ATP.
12
Q
Contractile proteins
A
- Myocin & actin
- Creates a contraction; shortens the muscle fiber
13
Q
Regulatory proteins
A
- Tropomyosin & troponin
- Acts like a switch to determine when a fiber can contract and when it cannot
14
Q
Structural proteins
A
- Ensures that thin & thick filaments are geographically located in the correct positions
15
Q
Three phases of the twitch cycle on a myogram
A
- latent period
- contraction period
- relaxation period
16
Q
Myogram
A
- Recording of muscle activity
17
Q
Neuromuscular Junction (NMJ)
A
- the point where a nerve meets a muscle fiber
- synapse between a motor neuron and a muscle fiber
- Also called motor end plate
18
Q
relaxation period
A
- Muscle tension declines as the myosin releases the thin filaments
19
Q
Sarcoplasmic Reticulum (SR)
A
- Contains a Ca reservoir that allows for muscle contractions to occur
20
Q
The four stages of the
Sliding Filament Mechanism
A
a. ATP hydrolysis cocks myosin head
b. attachment of myosin to actin to form cross bridges
c. power stroke sliding of thin filament over thick filament
d. detachment of myosin from actin binding of new ATP breaks cross-bridge, re-cocks for a new active site
21
Q
Sliding Filament Theory
A
- the myofilaments don’t become any shorter during contraction;
- the thin filaments slide over the thick ones and pull the Z discs behind them,
- causing each sarcomere as a whole to shorten
22
Q
Slow twitch
A
- adapted for endurance and fatigue,
- rely heavily on oxidative metabolism (Aerobic respiration)
- surrounded by dense capillaries,
- rich in mitochondria, and
- thin for oxygen diffusion
23
Q
Synaptic cleft
A
- space between axon terminal and muscle fiber
24
Q
Thick filaments
- Protein composition
- Binding sites
A
- Composed of myosin; consists of a moving head and a stationary tail
- Binding sites
- ATP binding site: determines if the head is flexed or extended
- Actin binding site (thin filaments): forms a cross-bridge
25
Q
Thin filaments
- Protein composition
- Binding site
A
- Composed of actin, troponin, & tropomyosin
- Myosin binding site
26
Q
Twitch strength factors
A
- Stimulus frequency
- Concentration of Ca+2
- How stretched muscle was before it was stimulated
- Muscle temperature
- pH of sarcoplasm
- State of hydration
- Recruitment or multiple motor unit (MMU) summation
27
Q
isotonic muscle contractions
A
- Muscle develops tension and muscle shortens
28
Q
Isometric muscle contractions
A
- muscle develops tension but does not shorten
