Quiz #1 + Exam #1 Flashcards
(a) What are skeletal muscles comprised of? What are they bundles of?
(b) What are muscles fibers/muscle cells composed of and what can they be subdivided into? What are they also called?
(c) Where are satellitle cells located?
(d) In humans, most skeletal muscles are ____ of muscle fiber types.
(e) What determines where the sliding filament theory occurs?
(a) Skeletal muscles are comprised of fasicles, which are bundles of muscle fibers
(b) Myofibrils, which can be divided into actin and myosin (aka contractile proteins)
(c) Near, or embedded in, the sarcolemma (exterior of the cell)
(d) a mix
(e) Depends on the acitivy of the individual, thus certain muscle fiber types will be activated
What are the three major functions of skeletal muscle?
- Force generation for locomotion and breathing
- Force generation for postural support
- Heat production during cold stress
What is the sarcoplasm?
A connective tissue that wraps around an individual muscle cell/muscle fiber.
(a) What are thin filaments also called?
(b) What consists of the thin filaments?
(c) What is the net charge?
(a) actin
(b) G-actin, troponin, tropomyosin
(c) positive, +
(a) What are thick filaments also called?
(b) What consists of the thick filaments?
(c) What is the net charge?
(a) myosin
(b) Myosin heads, myosin tails
(c) negative, -
How does the net charge of thick and thin filaments help with muscle contraction?
Allows for them to bind to each other with opposite charges.
(a) What are satellite cells?
(b) Where are they located?
(c) What type of training can activate satellite cells? What does it become?
(d) What is it predicted to play a role in?
e) Explain how does training activate satellite cells (HINT! include nuclei)
(f) “____ is the brain of the cells, without it, the cell has nothing to regulate it.”
(a) A type of precursor cell
(b) Located near the sarcolemma
(c) Resistance training, can become most cell types as needed for bodily fucntion and maintenance
(d) Predicted to play a role in muscle growth and repair
(e) Contraction from training causes tension on the surface of a muscle cell, which is where the satellitle cells are located, thus causing them to become activated and dividing, which theoretically could** increase** the number of cellular nuclei
(f) Nuclei!
What is fascia?
A connective tissue that seperates individual muscles from each other, holding them in position
(a) Describe the neuromuscular junction (NMJ). Be detailed in its function.
(b) Which types of exercise training cause positive adaptions to the NMJ?
(c) Describe the 3 adaptations to the NMJ that occur as a result of training. What does this enhance?
(d) T/F: We see change in muscle size before adaption in the NMJ after weeks of optimal training.
(a) Neuromuscular junction: Interface bewteen a motor neruon and muscle cells OR where neurons meet muscle fibers
- Signals are sent from the brain, down the spinal cord to an alpha motor neuron. AP travels dow nthe synaptic bulb to which it will release ACh, which will then bind to the binding sites on the muscle cells
(b) Both resistance and endurance training
(c) 1. ↑ # of vesicles contain ACh
- ↑ # of ACh receptors on motor end plate
- ↑ size of motor end plate
= Overall enhancement of the electrical signal to the muscles
(d) False!
Consider the results of a 16-week resistance training program, where periodization and nutrition are optimal…
(a) Visually, what are we likely to see?
(b) What causes this result?
(c) Why do muscle cells adapt in this manner? (Exercise training is a stressor)
(d) True or false? Only muscle cells adapt to training. Justify your response.
(e) What term describes the situation where the # of muscle fibers increases? What is the misconception?
(a) Hypertrophy
(b) ↑ # of myofibrils
(c) So that future bouts of exercise/activity are less stressful
(d) ALL systems adapt, all cells involved adapt ; Systems that support muscle cells must also grow and adapt, or else it will all fail.
(e) Hyperplasia ; small amt. of evidence in humans, but def. in chicken and cat
Describe what is the “Myonuclear domain.”
- Myonuclear domain is the volume of sarcoplasm surrounding an individual nucleus. The nucleus is considered to be, “the brain of the (muscle) cell” and holds the necessary gene expression, such as for protein production. Without it, the cell will not be able to regulate/function on its own.
- A single nucleus, however, can only manage cellular activities/functions for a fixed volume of sarcoplasm and the ratio of cell volume and per nucleus remains constant.
- If the sarcoplasmic volume increases due to hypertrophy (from training), then the number of nuclei must also increase. Therefore, to remain a constant ratio, the satellite cells will become activated from training, dividing and creating additional nucleus.
Describe “motor unit”
The motor neuron and all the muscle fiber it innervates.
What is the difference in the motor unit recruitment in relfex movements vs. planned movments.
- Reflex movements begin at spinal cord, brain is “informed” after movement has been intitiated
- Planned movements being in the brain
Describe the excitation sequence of the excitation-contraction coupling.
- Action potential (AP) arrives at synaptic bulb or knob.
- Vesicles secrete ACh, a neurotransmitter.
— ACh binds to receptors on the motor end plate, aka post-synaptic membrane -
Ion channels open on sarcolemma, and Na+ floods
into muscle cell, causing depolarization of the muscle cell.
Describe the contraction sequence of the excitation-contraction coupling.
- Waves of depolarization spread across muscle cells, down ** t-tubules ,** which stimulates SR (sarcoplasmic reticulum) to release Ca2+.
- Ca2+ binds to troponin, which then pulls tropomyosin off the myosin binding site on actin.
- Actin and mysoin bind, formin a cross-bridge.
- Pi is released from mysoin head → powerstroke
- ADP is released from mysoin head → rigor state
- New ATP binds to myosin head, which breaks rigor state
- Enzyme Myosin ATPase hydrolyzes the ATP on the myosin head
- Energy, a product of ATP hydrolysis, is used to recock the myosin head back to starting position
Describe the relaxation sequence of the excitation-contraction coupling.
- Brain stops generating AP
- The release of neurotransmitter, ACh, from vesicles within muscle cells stops
- Muscle cells repolarize
- The Ca2+ that is now within the muscle cell goes back/is pumped back to the SR, which requires ATP
- Troponin blocks the myosin binding site on actin, which breaks apart the crossbridge.
Be familiar with the formula during ATP hydrolysis
*ATP hydrolysis occurs in the presense of water and ATPase!
ATP + H2O (w/ Myosin ATPase) → ADP + Pi + Energy + OH- + H+
Which structure found in skeletal muscle fibers acts the storage location for calcium?
Sarcoplasmic reticulum (SR)
What are the 3 sources of ATP production in muscle during contraction?
- PCr
- Glycolysis
- Oxidative Phosphorylation (Kreb Cycle and Beta Oxidation)
(a) What are human skeletal muscle fiber-type categories based on?
(b) About how many spectrum of fiber type exists?
(c) What are the three types of human skeletal fiber types that will be discussed in class?
(a) Biomechanical properties, mechanical properties, and fucntional characteristics
- Some overlap exists
(b) 12 - 13
(c) - Type I slow-twitch (slow oxidative)
- Type II fast-twitch:
1. Type IIa intermediate (fast oxidative, glycolytic)
2. Type IIx fast glycolytic or fast-twitch
What are the three primary biomechanical properties of skeletal muscle? Explain each one.
- Oxidative capacity:
a) mitochondrial vol. or density
- Relates to cell’s ability to produce ATP aerobically (beta-oxidation) AND fatigue resistance
b) Capillary density: the network of blood vessels that move O2 from lungs to muscle
- ↑capillary density = ↑O2 from lungs to muscle
c) [myoglobin] or [MB]: transports oxygen from through sarcoplasm to mitochondria - Myosin isoform (or type)
- Myosin ATPase
- Type I, IIa, IIx - # actin/mysoin
- per muscle fiber and motor unti
What are the four performance charcteristics of the contractilie properties of a skeletal muscle? Explain each one.
- (346) Max force production or (446) specific tension
- = # of force produced/cross-sectional area of muscle fiber - (346) speed of contraction or (446) max. shortening velocity (aka Vmax)
- Related to:
a) Isoform of ATPase
b) Size of motor neuron
- If the neuron is much bigger, it allows for AP to travel much quicker
c) SR development
- SR is a network that surrounds the muscle fiber that holds Ca2+
- The denser and closer the webbing in a Type IIx allows for Ca2+ to travel a small distance to the troponin, vs. the webbing in a Type I - Max. power output
- = to points #1 and #2 - Effciency of contraction
- = # of ATP used/# of force produced
Distinguish type I fibers vs. type IIA fibers vs. type IIX fibers in terms of the following…
(a) Number of mitochondria
(b) Resistance to fatigue
(c) Predominant energy system
(d) ATPase activity
(e) Vmax (speed of shortening)
(f) Effciency
(g) Specific tension
(a) Number of mitochondria:
- Type I: High
- Type IIa: High/moderate
- Type IIx: Low
(b) Resistance to fatigue:
- Type I: High
- Type IIa: High/moderate
- Type IIx: Low
(c) Predominant energy system:
- Type I: Aerobic
- Type IIa: Combination
- Type IIx: Anaerobic
(d) ATPase activity:
- Type I: Low
- Type IIa: High
- Type IIx: Highest
(e) Vmax (speed of shortening):
- Type I: Low
- Type IIa: High
- Type IIx: Highest
(f) Effciency:
- Type I: High
- Type IIa: Moderate
- Type IIx: Low
(g) Specific tension:
- Type I: Moderate
- Type IIa: High
- Type IIx: High
(a) T/F: Is atheltic performance due only to fiber type distribution? Explain.
(b) What factors in athletic performance?
(c) What are the fiber type distribution in nonathletes?
(d) _ % of fiber types determined prior to birth and _ % determined during first 24 months of life.
(e) What determines a starting point for fiber distribution?
(a) False ; EX: % of Type I fiber distribtuion explains only 40% of VO2 max between individuals
(b) Athletic performance is due to a complex interaction of psychological, neurological, cardiopulmonary, and biomechanical factors
(c) 50% Type I and 50% Type IIa/x
(d) 80% ; 20%
(e) Gene pool