Study sets, textbooks, questions
Upgrade to remove ads
BIO 131: Exam 2 Concept Check 1- Skeletal Muscle
Terms in this set (41)
What is the A band?
Dark band that encompasses the entire length of a thick filament; entire length of myosin.
What is the I band?
Light band that represents the region occupied only by thin filaments; Actin only
What is a sarcomere?
Contractile unit of myofibril
What are the contractile proteins for skeletal muscle? What are their functions?
Actin (thin band):
- is like a rope that myosin can grab onto & pull on.
Myosin (thick band):
- the motor protein, which actively induces muscle shortening
- myosin head-
What are the regulator proteins for skeletal muscle? What are their functions?
- controls the position of tropomyosin
- can reversibly bind Ca++
- when Ca++ is present, it changes shape, pulling on tropomyosin & removing it from its inhibiting position; aka. power stroke can now happen
- blocks the powerstroke from happening by inhibiting the myosin head from binding to Actin.
What are the accessory proteins for skeletal muscle? What are their functions?
- stretches from one Z disk to the neighboring M line
- stabilizes the position of the contractile filaments
- its elasticity returns stretched muscles to their resting length
- helps align the actin filaments of the sarcomere
- lies alongise thin filaments & attaches to the Z disk
What is the sliding filament theory?
During contraction, overlapping thick & think filaments slide past each other in an energy-dependent manner as a result of actin-myosin crossbridge movement.
What are the steps during EC coupling?
1) ACh is released from the somatic motor neuron
2) ACh released into the synapse at a neuromuscular junction binds to cholinergic nicotinic receptors on the motor end plate of the muscle fiber.
3) Chemically-gated monovalent (single charge) cation channels open which leads to Na+ influx & K+ efflux.
4) The addition of net (+) charge to the muscle fiber depolarized the membrane, creating an end-plate potential (EPP).
5) EPP triggers the opening of V-gated Na+ & K+ channels.
6) Initiates an AP in the muscle fibers
7) AP travels across the surface of the muscle fiber & into the t-tubules
8) AP in t-tubule alters the DHP Receptor, causing a conformation change to pull open the Ryanodine receptors (RyR) on the SR to release calcium
9) Cytosolic Ca++ binds to troponin
10) Troponin moves troppmyosin from its inhibiting position
11) Power stroke & muscle shortening occurs.
What is the diff. between End Plate Potential & AP in skeletal muscle?
The EPP is caused by ions flowing through monovalent cation channels.
The EPP causes the AP
The AP is caused by ions flowing through V-gated channels.
What channels and ions are involved in End Plate Potential?
Monovalent Cation Channels
What channels and ions are involved in AP in skeletal muscle?
V-gated Na+ & V+gated K+
Na+ & K+ ions.
What steps are necessary for relaxation of the skeletal muscle to occur?
1) Sarcoplasmic Ca++-ATPase pumps Ca++ back into the SR
2) Decrease in free cytosolic Ca++ causes Ca++ to unbind from troponin
3) Troponin allows tropomysoin to move back to the "off" position, blocking myosin heads from binding to actin.
4) When myosin heads release, Titin pulls the filaments back to their relaxed position.
What steps during the contraction/relaxation process require ATP?
ATP is required during:
- Power stroke (myosin head hydrolyzes ATP to swivel at its hinge)
- Pump Ca++ back to SR
- Pump Na+ & K+ back to the ICF & ECF
What is rigor mortis (stiffness after death)?
Why does it occur?
It is when myosin is tightly bound to actin.
Because in death, our bodies no longer produce ATP the myosin head cannot be released from actin. ATP is required to release the mysosin head and "recock" it to perform another power stroke.
Why does rigor mortis NOT occur in a living person?
ATP is required to release the mysosin head and "re-cock" it to perform another power stroke. Our bodies our continuously producing ATP so that our muscles can under go crossbridge cycling.
Which state are actin & myosin usually found in for a living person?
Actin & Myosin are in the "relaxed" state when the muscle is not being used. The Thick & Thin filaments overlap slightly, with the myosin head cocked at 90 degree's.
The bacterium Clostridium Botulinum produces a toxin, that can be injected subdermally to decrease wrinkles & fine lines in the face (Botox injection). The toxin works by inducing localized flaccid muscle paralysis. Suggest a mechanism by which this toxin could have its effect.
- what would happen if the toxin were to enter the general circulation?
What are the ways in which we can alter how much tension is generated by an isolated (out of body) skeletal muscle?
1) Recruit more motor units
- this will increase the stimulus which will increase then tension strength.
2) Change the Length-Tension relationship.
- Adjust the length to Optimal Length to get optimal overlap of actin & myosin for the max # of crossbridges.
3) Increase the freq. of stimulation
- generate a sustained contraction (known as tetanus) to recruit all of the motor units to generate max force.
What is a motor unit?
One motor neuron & its muscle fibers.
- It is the basic unit of contraction composed of a group of muscle fibers that function together & the somatic motor neuron that controls them.
What is motor unit recruitment?
The activation of additional motor units to accomplish an increase in contractile strength in a muscle
Muscles involved in fine motor activities would have a small or large motor units?
Small motor units.
What is the length-tension relationship?
The force created by a muscle fiber is directly related to the length of the sarcomere, as indicated by the initial length of the muscle fiber.
What is optimal length?
The maximum number of crossbridges
What is twitch?
- a single contraction-relaxation cycle in a skeletal muscle fiber.
- the time between AP's is shortened, the muscle fiber does no have time to relax completely between 2 stimuli, resulting in a more forceful contraction.
- AP's continue to stimulate the muscle fiber repeatedly at short intervals, relaxation between contractions diminishes until the muscle fiber achieve a state of maximal contraction.
What happens when you began weight lifting?
Why do your muscles grow?
Does fiber # change in muscle?
- Do the individual muscle fibers change- how?
- Yes. exercise stimulate the synthesis of contractile proteins. This causes the muscle fibers adapt to the strain being placed on them and hypertrophy
What happens when you begin endurance training?
- do your muscle fibers change- how?
The muscle fibers adapt to the strain being placed on them. Specifically, Type 2X fibers can become Type 2A fibers when an individual continues to train aerobically. The anaerobic fibers become more aerobic and adapt to carry out both aerobic & anaerobic exercises.
What is the preferred energy source for skeletal muscle
What is glycogen?
The stored form of glucose
What is phosphocreatine?
When there is excess ATP, it is stored as phosphocreatine.
What is anaerobic metabolism?
- quick, does not require O2
- only produces 2 ATP per glucose
- lactic acid is a byproduct
Citric Acid Cycle, Oxidative Phosporylation
- Slower, requires O2
- happens in the mitochondria
- produces 30 ATP per glucose
What is the diff. between peripheral fatigue & central fatigue?
Peripheral fatigue is due to:
- the accumulation of lactic acid
- the depletion of ATP
- the depletion of ACh
Central fatigue is due to:
- a decrease in voluntary drive
Are red or white muscle fibers of the somatic motor neurons are more sensitive/are activated first during recruitment?
Because red fibers are more fatigue-resistant, they are recruited first.
A chemical that increases acetylcholine esterase (an enzyme that breaks down ACh in the synaptic cleft) activity would lead to what kind of muscle paralysis- flaccid or contracted?
ACh must bind to the nicotinic receptor in order to open the V-gated monovalent cation channels and trigger the AP that will lead to a power stroke.
With ACh being broken down before it can bind to the nicotinic receptor, the muscle will not be able to contract. Thus leading to muscle paralysis.
Increased levels of cortisol would promote/reduce the amount of glycogen storage in skeletal muscle fiber?
Cortisol promotes gluconeogenesis.
Increased cortisol= increased glyocogen.
Increased levels of insulin would promote/reduce the amount of glycogen storage in skeletal muscle fiber?
Insulin decreases glucose concentration,
Acetylcholine esterase is?
An enzyme that deactivates ACh, by breaking it down into acetyl & cholin, in the synaptic cleft.
The main inhibitory neurotransmitter in the brain.
It hyperpolarizes their target cells by opening Cl- channels & allowing Cl- to enter the cell.
The primary excitatory neurotransmitter of the CNS.
It depolarizes their target cells.
Recommended textbook explanations
Concepts of Genetics
Charlotte A. Spencer, Michael A. Palladino, Michael R. Cummings, William S. Klug
Essentials of Genetics Plus MasteringGenetics with eText -- Access Card Package
Charlotte A. Spencer, Michael A. Palladino, Michael R. Cummings, William S. Klug
Sets found in the same folder
BIO 131 Exam 1 Study Guide Prt 1 of 3
BIO 131 Exam 1 Study Guide Prt 2 of 3
BIO 131 Exam 1 Study Guide Prt 3 of 3
Bio 131 Exam 1 Lab Study Guide
Sets with similar terms
Ch 10 Skeletal Muscle
Human Physiology: Chapter 12 - Muscles
Human Physiology - Muscles
Other sets by this creator
ACSM EP-C Prt 3
ACSM EP-C Prt 2
ACSM EP-C Prt 1
Other Quizlet sets
IB Cognitive Level of Analysis (Set 3/3)
Upper Respiratory Pharm
Chapter 13: Gravitation
FSN 328 Quiz 3