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
