Skeletal Muscle And Smooth Muscle physiology (MODULE 4) Flashcards
Define compare and contrast upper motor neuron and lower motor neuron.
UMN - *Motor neuron signals travel from brain to spinal cord (fully in the CNS)
- A neuron that extends from brain and synapses with a lower motor neuron, commonly in the lower spinal cord
UMNs follow the Pyramidal Tracts = Corticospinal tract and Corticobulbar tract
Synapses with the LMN
LMN - *Motor neuron that originates (cell body) in the spinal cord/brainstem and send signals to skeletal muscles
- Anterior grey horn of spinal cord and cranial nerve nuclei
Define compare and contrast alpha motor neurons and gamma motor neurons
AMN - function and are responsible for directly innervating skeletal muscle fibers, specifically the extrafusal fibers (fibers that generate force for muscle contraction)
- Located on the ventral horn. When they fire they release acetylcholine at the neuromuscular junction, causing the extrafusal muscle fibers to contract, which is voluntary.
GMN - Function to innervate intrafusal muscle fibers within the muscle spindles (a sensory organ that detects muscle stretch).
- Located in the ventral horn of the spinal cord, but their axons project to he muscle spindles, which are embedded within the muscle itself.
- Work to regulate the sensitivity of the muscle spindle by adjusting the tension in the intrafusal fibers. This helps maintain muscle tone and allows the muscle spindle to detach stretch more accurately, contributing to posture and reflexes.
Overall:
AMN - Function: control voluntary muscle contraction
GMN - Function: Regulate sensitivity of muscle spindles
AMN - Target: Extrafusal muscle fibers (contraction)
GMN - Target: Intrafusal muscle fibers (within muscle spindles)
AMN - Activation: Voluntary, via central motor pathways
GMN - Regulated by the CNS to adjust spindle sensitivity
Define compare and contrast extrafusal and interfusal skeletal muscle fibers
Extrafusal
- Primary muscle fibers of skeletal muscle - leads to muscle contraction
- Generates contraction process - creating tension and movement
*Innervated by alpha motors neurons
Infrafusal
- Smaller muscle fibers found within muscle spindles that are embedded within the extrafusal skeletal muscle fibers
*Has SENSORY and MOTOR innervation
(Sensory - Basically, stretch receptors; Detect the amount and rate of change in muscle length)
(Motor - Allows for muscle contraction; Of the fiber, controlling sensitivity of the sensory portion)
Describe a muscle spindle anatomy and function
- Sensory organ within skeletal muscles that plays a crucial role in detecting muscle stretch and contributing to proprioception.
—>Muscle spindles consist of specialized muscle fibers called intrafusal fibers.
Define Motor Units
*All the muscle fibers innervated by one alpha motor nerve fiber (LMN)
- Number of muscle fibers innervated by a motor unit varies (From a few fibers to thousands of fibers; depends on if fine control or gross movement is required)
The force of muscle contraction is “controlled” by the number of motor units that are stimulated.
Define the concept of size principle associated with motor units
Small motor units fire first, then larger ones, then larger ones
• Referred to as the size principle of muscle contraction
• Size Principle
• As more motor units are recruited, progressively larger motor units meet
the action potential threshold and greater tension will be generated
Describe the general process of how UMN LMN lead to muscle contraction
UMN
Role: UMNs are responsible for initiating voluntary movement. They send signals down through the central nervous system (CNS) to the spinal cord.
Pathway: The UMN travels down the corticospinal tract, which crosses over to the opposite side of the body at the level of the brainstem (pyramidal decussation). This means that each side of the brain controls the opposite side of the body.
Synapse: The UMN synapses with the lower motor neuron (LMN) in the spinal cord or brainstem.
LMN
Role: LMNs are responsible for directly stimulating muscles to contract.
Pathway: After receiving input from the UMN, the LMN carries the electrical signal out to the muscle via its axon.
Synapse at the neuromuscular junction: The LMN synapses at the neuromuscular junction with muscle fibers. Here, the electrical signal is translated into a chemical signal (through the release of acetylcholine), which stimulates the muscle to contract.
Overall:
Upper motor neurons initiate and control voluntary movements from the brain.
Lower motor neurons directly stimulate the muscles to produce movement. This collaboration between UMNs and LMNs is essential for coordinated, voluntary muscle contractions.
Somatic Nervous System VS Visceral Nervous System
SNS- PNS associated with the voluntary control of body movement via skeletal muscles; lower and upper motor neurons
VNS- internal organs; autonomic nervous system
What Upper Motor Neuron Originates in CNS?
Corticospinal tract and corticobulbar tract
Cerebral Cortex
Initiates voluntary movement of skeletal muscles
Synapse with lower motor neuron (LMN)
LMN
Motor neuron originates where in the spinal cord and the brainstem?
Spinal cord: Anterior Grey Horn
Brainstem: Pons and Medulla
- Send signals to skeletal muscles to allow for contraction
- Connect the UMNs to skeletal muscles
Name the three types of LMNs?
- Alpha Motor Neuron (focus)
- Beta Motor Neuron
- Gamma Motor Neuron (focus)
Alpha Motor Neurons: Directly innervate skeletal muscle fibers and cause muscle contraction.
Gamma Motor Neurons: Innervate muscle spindles to regulate muscle tone and stretch sensitivity.
Beta motor neurons are believed to contribute to the regulation of both the extrafusal (alpha motor neurons) and intrafusal (gamma motor neurons) fibers within muscles. They may help in modulating muscle spindle sensitivity in some cases, though their role is less clearly defined compared to alpha and gamma neurons.
LMN Types:
Alpha Motor Neurons Overview
- Innervate extrafusal skeletal muscles Synapse fibers
- AP in Alpha motor neurons lead to AP in the extrafusal muscle fibers (muscle cell) they innervate
LMN Types:
Gamma Motor Neurons Overview
- Innervate intrafusal muscle fibers (found within muscle spindles)
- Muscle spindle is to sense muscle length
- Gamma moto neurons function is to adjust the sensitivity of the muscle spindles
T or F
Gamma motor neurons are efferent; Group la and II sensory fibers are afferent
T
T or F
Intrafusal skeletal muscles sensory detect stretch
T
Name the components of the NMJ. (4 total)
- Axon terminal of lower motor neuron
- Synaptic cleft
- Sarcolemma (plasma membrane of skeletal muscle) of skeletal muscle
- Cholinergic Nicotinic receptors
T or F
Cholinergic receptors bind acetylcholine
T
Discuss the steps of NMJ. (6 total) *Simplified
- Action potential is propagated to axon terminal 2. Action potential stimulates voltage gated calcium (Ca 2+) ion channels to open
- Calcium (Ca 2+) ions cause the release of acetylcholine into the synaptic cleft
- Acetylcholine binds to Sodium (Na +) ion LIGAND gated channels on the skeletal muscle
• It is an excitatory stimulus- brings the membrane potential closer to threshold - If the graded potential is strong enough an action potential is generated and in travels in both directions of the plasma membrane
• Generated by activating Sodium (Na +) VOLTAGE gated ion channels
• 6. Acetylcholine is broken down in synaptic cleft and prevents action potential in skeletal muscle from continually being generated
Discuss the NMJ steps. *refer to slides 29-31
Steps 1-3
- Action potential stimulates voltage gated
calcium (Ca2+) channels to open in axon terminal —> Calcium (Ca2+) ions rush into axon
terminal
• Why? • Calcium (Ca2+) ions bind to
synaptic cleft
• Exocytosis
• Acetylcholine (ACh) is released into the synaptic cleft
Step 4
• ACh in synaptic cleft diffuses across the
synaptic cleft • ACh binds to cholinergic nicotinic
receptors
• Bind 2 ACh molecules • Allow for Sodium (Na +) to rush into the cell
• Technically, a little Potassium (K +) ions to rush
out of cell
• Causes what of the motor end plate of
the sarcolemma?
• Graded potential (End Plate Potential)
Step 5
• Sarcolemma undergoes depolarization at the motor end plate
• End plate potential • Leads to the membrane potential depolarization and activation of
the sodium (Na+) voltage gated channels • Action potential travels along sarcolemma and down the T-tubules • T-tubules • Movement of action potential
Step 6
- ACh continues to bind to nicotinic receptors as long as ACh persists in the synaptic cleft • For action potentials to cease
• Must break down ACh within the synaptic cleft
—> Acetylcholinesterase
• Enzyme that breaks down neurotransmitter acetylcholine in synaptic cleft • Breaks ACh into Acetate and Choline
• Choline is endocytosis back into pre-synaptic neuron and used to make more Ach
• Choline Acetyltransferase
• Makes acetylcholine in axon terminal
Define the somatic nervous system
Part of the PNS that is responsible for controlling voluntary movements and converting sensory information from the body to the CNS. It consists of motor neurons that control skeletal muscles and sensory neurons that relay information from sensory receptors to the brains and spinal cord
Describe Nicotinic receptors. What do they do?
What are motor end plates?
- Bind acetylcholine
- Ligand gated sodium (Na+) channels
- Motor End Plates - indented to fit the axon terminal, contains Cholinergic Nicotinic receptors that bind acetylcholine
Describe the characteristics of skeletal cardiac and smooth muscle.
Skeletal
- attached to skeletal system
- voluntary control
- striated appearance
- multi-nucleated
- non-branched
- non-rhythmic contractions
Cardiac
- within the heart
- involuntary control
- striated appearance
- single nucleus
- branched
- rhythmic contractions
Smooth
- within the visceral (organs)
- involuntary
- non-striated appearance
- single nucleus
- tapered
-rhythmic contractions
Describe the difference between the endomysium, fascicles, perimysium, and epimysium of a skeletal muscle.
- Epimysium is the outermost layer of connective tissue that surrounds the entire muscle.
- Perimysium surrounds groups of muscle fibers, forming bundles called fascicles.
- Endomysium is the innnermost connective tissue layer. The endomysium is the innermost connective tissue layer, the endomysium surrounds each individual muscle fibers called.
What are myofibril?
What make up myofilaments?
Muscle cells
Myofilaments are made up of thick and thin filaments
Thick filaments - myosin
Thin filament - actin, tropomyosin, troponin
The triad in a skeletal muscle cell is made of what components?
What do these components do?
T-tubules, these are invaginations of the muscle cell membrane (Sarcolemma) that penetrate into the muscle fiber.
Sarcoplasmic reticulum is a specialized type of endoplasmic reticulum in muscle cells, repsponsible for storing and releasing calcium ions.
Terminal cisterns are enlarged areas of the sarcoplasmic reticulum located adjacent to the T-tubules. They store large amounts of calcium ions and release them into the cytoplasm when the muscle is stimulated to contract.
What are mitochondria’s role in skeletal muscle contraction?
Making ATP for muscle contraction to occur.
Define a sarcomere.
Structural unit of a myofibril in s treated muscle
- Segment between two neighboring Z-lines (or Z-discs)
Overlap of the myofilaments (thick and thin filaments)
Thousands of them in a muscle cell.
Muscle Sarcoplasm contains glycogen and myoglobin. What are these structures for?
Glycogen - storage form of carbohydrates
Myoglobin - Protein that contains heme; red in color; storage device for oxygen
What are the needed “ingredients” for muscle contraction? (5)
- AP within SKM (skeletal muscle)
- Specialized receptors
- Calcium (Ca2+) ions
- Myofilaments
- ATP
T or F
Myosin is a thick filament
T
Myosin heads have 2 binding sites: What are these?
- Myosin ATPase (enzyme to break down ATP to ADP) binding sites
- Actin binding site
Describe actin, tropomyosin, and troponin.
ALL THIN filament
Actin - G-actin contains the binding sites to bind Myosin; F-actin is the chain of G-actin molecules
Tropomyosin - Covers up the myosin binding sites on G-actin
• Tropomyosin covers up the myosin binding sites on G-actin OR
Tropomyosin is moved off the myosin binding sites on G-actin
Troponin - Regulates the position of tropomyosin by binding calcium (Ca 2+) ions
• Technically composed of three components:
• 1) Troponin T binds the troponin components to tropomyosin • 2) Troponin I inhibits the interaction of myosin with actin • 3) Troponin C contains the binding sites for calcium (Ca 2+) ions
What option is true regarding myofibrils?
• A. The thick filament consists of tropomyosin and actin
• B. The thin filament has two binding sites
• C. The thick and thin filament are arranged in sarcomeres that allow for
muscle contraction • D. Calcium binds to actin to allow the thick filament to bind to the thin
filament
C
Describe how the thick filament binds to the thin filament.
Heavy chain of myosin’s head has an actin binding site
What statement is true of sarcomeres?
• A. It contains thick filaments that overlap on z discs
• B. The H zone is where the thick and thin filaments overlap
• C. Sarcomeres are found in myofibrils
• D. It extends from I band to H band
C
Glycogen is a storage form for oxygen in the sarcoplasm.
• A. True
• B. False
B
All of the statements are true, except?
• A. A sarcomere consists of thick and think filaments
• B. The triad region consists of the junction of terminal cisternaes and transverse tubules
• C. Sarcoplasmic reticulum surrounds each myofilament
• D. Skeletal muscle cells have multiple nuclei
C
Voltage gated sodium channels open in the axon terminal to stimulate the release of a neurotransmitter.
• A. True • B. False
B,
AP stimulates voltage gated calcium ion channels to open —> Calcium ions cause the release of acetylcholine into the synaptic cleft
Describe the characteristics and role of the cholinergic nicotinic receptors.
Ligand gated sodium channels that bind acetylcholine found in the motor end plate initiating an action potential
Where are sodium voltage gated channels located on the sarcolemma and what role do they have?
Located just outside of the motor end plate and once activated will generate an action potential within the muscle cell
What role do T-tubules have with the neuromuscular junction?
Allow for the action potential process to be transmitted deep into the skeletal muscle tissue
The ANS and UMN and LMN are part of the somatic nervous system.
• A. True
• B. False
B
LMNs are found in the CNS and PNS.
• A. True
• B. False
A
All of the options are true regarding intrafusal muscle fibers, except?
• A. It contains sensory and motor functions
• B. Alpha lower motor neurons innervate intrafusal muscle fibers
• C. Assists with proprioception
• D. Assists with detection of rate of muscle length
B
Upper motor neurons synapse with extrafusal muscle fibers via a neuromuscular junction.
• A. True • B. False
B
A motor unit is all the gamma lower motor neurons and the extrafusal muscle fibers it innervates.
• A. True • B. False
B
List the 4 muscle contraction steps:
1 - Excitation: AP transmission
- AP is initiated at the motor end plate (NMJ)
- Travels along Sarcolemma and down the T-tubules
2 - Excitation: Contraction Coupling: Release of calcium ions
*Goal is to get calcium ions released from sarcoplasmic reticulum and flood the Sarcoplasm; AP traveling down the T-tables will ultimately activate:
1. Dihydropyridine receptor (DHPR)
2. Ryanodine receptor (found on terminal cisternae of sarcoplasmic reticulum)
- Now the calcium ions flood, bind to troponin, and case a configurational shift which moves tropomyosin off actin’s active sites to bind the thick filament (myosin heads)
3 - Contraction: Crossbridge (when actin and myosin heads bind together) of myofilaments; power stroke (when the myosin head pulls the thin filament toward the M line of the sarcomere) of myofilament. ***Refer to Additional notes document on skeletal muscle module for the process of cross bridge power stroke process
4 - Relaxation: Release of the myofilaments
*SERCA: Sarcoendoplasmic reticulum Ca2+-ATPase
- Pumps calcium (Ca 2+) ions back into the sarcoplasmic reticulum
• Calcium (Ca2+) ions that dissociate from troponin are pumped back up into
the sarcoplasmic reticulum • - Requires energy
The sarcoplasmic reticulum is a holding tank for what ion?
Calcium (Ca+2)
What is a Dihydrophyridine Receptor (DHPR) ?
Contraction Step 2
- Found on the sarcolemma of the T-tubule
• Are voltage-gated calcium (Ca 2+) ion channels
• AKA: L-type calcium channel
Dihydropyridine Receptor is MECHANICALLY connected to the Ryanodine
Receptor
• If DHPR is activated- it activates (opens) the Ryanodine receptor
• Calcium ions FLOOD the sarcoplasm
What is a Ryanodine Receptor? What is this unit mechanically linked to?
What step of contraction is this?
STEP 2
- Found on the membrane of the Sarcoplasmic Reticulum
• Intracellular calcium channel
• Mediate the release of calcium ions from the sarcoplasmic reticulum
• Activated (opens) when DHPR is activated
Dihydropyridine receptor is MECHANICALLY connected to the Ryanodine Receptor
- it DHPR is activated it activates (opens the Ryanodine receptor (calcium ions FLOOD the Sarcoplasm
T or F
DHPR is activated it activates (opens the Ryanodine receptor (calcium ions FLOOD the Sarcoplasm
T
T or F
A cross bridge only occurs where there is a thin filament overlap
F
A cross bridge only occurs where there is thick and thin filament overlap
T or F
A power stroke is when the myosin head pulls the thin filament toward the M line of the sarcomere
T
T or F
During a cross bridge process the myosin’s heads must be in its HIGH ENERGY CONFIGURATION
T
Isometric Contraction VS Isotonic Contraction
Isometric - Generate force without changing the length of the muscle
Isotonic - Generate force by changing the length of the muscle and can be concentric contractions or eccentric contractions
Concentric Contractions VS Eccentric Contractions
CC- causes muscles to shorten, there by generating force
EC - cause muscles to elongate in response to a greater opposing force
The DHP receptor is activated when calcium ions enter the sarcoplasm.
• A. True
• B. False
F
The DHP is activated with the AP travels down the T-tubule
What is the function of calcium ions in muscle contraction?
Calcium binds to troponin, moving tropomyosin off of actin’s binding sites allow myosin (binding site on its head) to bind to actin
Activation of the ryanodine receptor allows for the release of calcium ions into the sarcoplasm.
• A. True
• B. False
T
What is the role of the SERCA?
SERCA is the Sarcoendoplasmic Reticulum Calcium ATPase pump that pumps calcium ions back into the sarcoplasmic reticulum helping to stop muscles fibers from contracting
How does myosin’s high energy configuration work?
Once the myosin head binds ATP and it is hydrolyzed, it puts the myosin head within its high energy configuration allowing it to bind to actin’s binding site (if open)
Alpha lower motor neurons, when stimulated, can have stimulatory or inhibitory effect on extrafusal skeletal muscle fiber contraction.
False
True
F
Just stimulatory
All the options are true regarding the neuromuscular junction, except?
A. Acetylcholine or norepinephrine can be released from the lower motor neuron to stimulate muscle contraction.
B. When the neurotransmitter binds to the receptors on the skeletal muscle, it leads to the opening of sodium ion channels.
C. Neurotransmitter receptors on the skeletal muscle are found in a region called the motor end plate.
A
What option is TRUE regarding the neuromuscular junction with extrafusal muscle cells?
A. Acetylcholine is released from the axon terminal of alpha lower motor neurons that binds to cholinergic muscarinic receptors.
B. Nicotinic receptors are voltage gated channels that open with the binding of acetylcholine.
C. Calcium voltage gate channels must open on the motor end plate to allow the initiation of the action potential in the sarcolemma.
D. The motor end plate region of the skeletal muscle cell contains ionotropic receptors.
D
What option is TRUE of alpha lower motor neurons?
A. They originate in the cerebral cortex of the brain.
B. They innervate intrafusal and extrafusal fibers.
C. They form synapses with skeletal and cardiac muscle cells.
D. They are found in the CNS and PNS of the body.
D
What option is TRUE regarding the neuromuscular junction?
A. Voltage gated sodium ion channels are located just outside of the motor end plate on the skeletal fiber.
B. Acetylcholine binds to cholinergic muscarinic receptors on the motor end plate.
C. Norepinephrine is released from the lower motor neuron.
D. Voltage gated sodium channels are activated on the motor end plate when they bind acetylcholine
A
What option is a characteristic of gamma lower motor neurons?
A. They provide sensory input from intrafusal muscle cells.
B. They provide an inhibitory effect on extrafusal muscle cells.
C. They provide both motor and sensory input to intrafusal muscle cells.
D. They only innervate intrafusal muscle fibers.
D
What option is true regarding motor neurons?
A. Upper motor neurons will synapse with extrafusal muscle fibers.
B. Lower motor neurons originate in the anterior grey horn of the cerebral cortex.
C. A motor unit is a gamma motor neuron and all the branches that innervate extrafusal muscle fibers.
D. Upper motor neurons are found entirely within the CNS.
D
What role does acetylcholinesterase have?
A. None of the options define the role of acetylcholinesterase.
B. It pumps acetylcholine back into the axon terminal.
C. It degrades acetylcholine in the synaptic cleft.
D. It enhances the function of acetylcholine.
C
As the action potential within the lower motor neuron reaches the axon terminal, it stimulates the opening of voltage gated calcium channels within the axon terminal.
True
False
T
Cholinergic nicotinic receptors are only found on the motor end plate of a skeletal muscle?
True
False
T
Myofibrils are composed of myofilaments and are surrounded by sarcoplasmic reticulum.
True.
False.
T
All of the options are functions of the muscular system, except?
A. Postural stability.
B. Body temperature regulation.
C. Blood pH balance.
D. Glycemic control.
C
All of the statements are true regarding muscle contractions, except?
A. Eccentric contractions occur when the muscle elongates.
B. Isometric contractions occur when there is muscle contraction with no change in the length of the muscle.
C. Isotonic contractions occur only when the muscle fibers are shortened.
D. Concentric contractions are type of isotonic contractions.
C
All of the processes have to occur for a cross-bridge to form, except?
A. Propagation of the action potential down the T-tubules.
B. Activation of the ryanodine receptor.
C. Dihydropyridine receptor activation.
D. Activation of the SERCA pump.
D
When muscles undergo contract, the thin filaments are “pushed” toward what structure of the sarcomere?
A. I band.
B. Z disc.
C. A band.
D. M line.
D
All of the options contribute to the termination of muscle contraction in a skeletal muscle cell, except?
A. Increase activity of acetylcholinesterase.
B. Calcium (Ca2+) ions in the sarcoplasm being pumped back into the sarcoplasmic reticulum by the sarco/endoplasmic reticulum Ca2+ ATPase pump.
C. Activation of the ryanodine receptor.
D. Action potential stopping its propagation through the transverse tubules.
C
Skeletal muscle cells can be characterized as:
A. Striated, voluntary, multinucleate.
B. Striated, voluntary, uninucleate.
C. Non-striated, involuntary, multinucleate.
D. Non-striated, voluntary, multinucleate.
A
What option is accurate regarding muscle contraction?
A. Acetylcholinesterase assists with the binding of acetylcholine to the motor end plate receptors.
B. Dihydropyridine receptors (DHPR) are activated by binding calcium (Ca2+) ions.
C. The binding ATP to the myosin head allows for myosin to disengage from the thin filament.
D. Each myofibril contains one sarcomere.
C
What option defines the role of the dihydropyridine receptor function in skeletal muscle contraction?
A. Opening channels on the sarcolemma to allow calcium ions to flow out of the sarcoplasmic reticulum.
B. Activation of the ryanodine receptor.
C. Assists with pumping calcium ions back into the sarcoplasmic reticulum.
D. Generating the action potential down the T-tubule.
B
All the options provide mechanisms to stop skeletal muscle contraction, except?
A. Calcium ions being pumped from the sarcoplasm into the transverse tubules.
B. Tropomyosin blocking actin’s binding site for binding myosin.
C. Acetylcholinesterase breaking down acetylcholine released from the motor neuron.
A
What option is TRUE regarding the cross-bridge formation?
A. Dihydropyridine receptor must become inactivated for the cross-bridge to form.
B. Calcium binds to troponin and hydrolyzes ATP to move tropomyosin off actin’s binding sites.
C. Actin must bind ATP for the cross-bridge to form.
D. Myosin head has to be in its high energy configuration to form a cross-bridge.
D
When muscle contraction occurs, what portion of the sarcomere will be affected?
I band
M line
Z zone
H zone
H zone
The SERCA pump is necessary for:
A. Assisting with the propagation of the action potential down the T-tubules.
B. Assisting with the relaxation phase of the muscle contraction process.
C. Providing the ability for calcium ions to bind to troponin.
D. Assists with stopping the action potential traveling throughout the sarcolemma to allow for muscle relaxation.
B,
Sarcoendoplasmic reticulum Ca2+-ATPase = pumps calcium (Ca2+) ions back into the sarcoplasmic reticulum
What statement is TRUE regarding the skeletal muscle contraction process?
A. None of the answers are true regarding skeletal muscle contraction process.
B. Tropomyosin binds the calcium ions released from the sarcoplasmic reticulum.
C. Actin has two binding sites: one for the myosin head and the other for the ATP.
D. The cross-bridge formation can only occur when actin hydrolyzes ATP.
A
What option defines the role of the dihydropyridine receptor function in skeletal muscle contraction?
A. Activation of the ryanodine receptor.
B. Assists with pumping calcium ions back into the sarcoplasmic reticulum.
C. Opening channels on the sarcolemma to allow calcium ions to flow out of the sarcoplasmic reticulum.
D. Generating the action potential down the T-tubule.
A
Transverse tubules are classified as part of the sarcolemma that travel deep into the muscle fiber.
True.
False
T
The thin filament is attached to what portion of the sarcomere?
Z line.
M line.
H line.
H zone.
Z line
All of the options have to occur for calcium to be released from the sarcoplasmic reticulum, except?
A. Action potentials travel down the transverse tubules.
B. Nicotinic receptors binding acetylcholine.
C. Dihydropyridine receptor to be activated.
D. ATP hydrolyzed by the myosin’s head ATPase binding site.
D
All of the statements are true regarding muscle contractions, except?
A. Concentric contractions are type of isotonic contractions.
B. Isometric contractions occur when there is muscle contraction with no change in the length of the muscle.
C. Isotonic contractions occur only when the muscle fibers are shortened.
D. Eccentric contractions occur when the muscle elongates.
C
Aerobic involves:
Aerobic (cellular respiration) (oxidative phosphorylation)
W/ O2
Anaerobic involves:
Glycolysis and anaerobic fermentation
What are the four types of ATP production?
Skeletal muscle has minor stage of ATP
Aerobic
Anaerobic
Creatine phosphate (CP)
T or F
Aerobic and anaerobic respiration involve glycolysis
T
_____ ATP are generated per glucose molecule
38
T or F
Reaction of phophocreatine + ADP to ATP + creatine is reversible
T
What is myoglobin?
Can bind O2, specialized protein found in skeletal muscles that store O2
- Contains iron (Fe) molecule
Provides the redness color to muscle
Does not directly make ATP; provides the oxygen
What are the three types of muscle fibers? What do they do?
Slow oxidative (SO); Slow Twitch - Type I MF
Fast oxidative (FO); Glycolytic; Type IIa MF
Fast glycolytic (FG); Type IIb MF
*Type II fibers develop tension 2-3x faster than type I fibers
Speed of contraction is directly related to how long it takes to complete a cross bridge process— Power stroke. What allows for that difference in speed?
- Dependent upon how quickly ATP can hydrolyze
- Type II fibers have a faster ATPase
- Type II fibers pump calcium (Ca2+) into the sarcoplasmic reticulum much faster too
Name the characteristics associated with Type I (SO) muscle fibers.
• Contraction Force -> Low
-Contraction speed
• Slower in contraction
• Slower in releasing and up taking
calcium from sarcoplasmic reticulum
• Slower ATPase hydrolyzing ATP
• Cellular Characteristics
• Dense network of capillaries
• LOTS of mitochondria
• Thinner in diameter
- Muscle Color
• RED
• High myoglobin concentration - Fatigue
• Slow to fatigue
• ATP Usage
• Aerobic respiration - Type of Exercises/Muscles
• Endurance muscles
• Postural muscles
• Running, swimming
Name the characteristics associated with Type IIa (FO) muscle fibers.
• Contraction Force and speed
• Faster in contraction (quick responses)
• Stronger than Type I Fibers
• Fast release and up taking calcium
- Cellular Characteristics
from sarcoplasmic reticulum
• Limited network of capillaries
• Fast ATPase hydrolyzing ATP
• Limited mitochondria
• Thicker in diameter
• Higher levels of creatine phosphate - Muscle Color
• RED
• High myoglobin concentration • Fatigue
• Intermediate
108 - ATP Usage
• Anaerobic and Aerobic respiration - Type of Exercises/Muscles
• Sprinting 400 meters
• Power lifting
• Jumping/Sprinting
Name the characteristics associated with Type IIb (FG) muscle fibers.
Contraction Speed
• Fastest in contraction
• Faster in releasing and up taking
calcium from sarcoplasmic reticulum
• Faster ATPase hydrolyzing ATP
moments
• Power lifting • Jumping/Sprinting
- ATP Usage
• Anaerobic respiration • - Type of Exercises/Muscles
• Quick bursts of movement for short
• Contraction Force
• High - Cellular Characteristics
• Limited network of capillaries
• Limited of mitochondria
• Thickest in diameter
• Muscle Color
• WHITE
• No to low myoglobin concentration • - Fatigue
• Fastest to fatigue
109
This type of muscle fiber has the highest concentration of myoglobin.
Type I.
All of the options have high concentrations of myoglobin.
Type IIb.
Type Ib.
Type I
This type of muscle fiber primarily utilizes creatine phosphate as a source of energy.
Type I muscle fibers.
Type IIb muscle fibers.
Type Ia muscle fibers.
Type IIa muscle fibers.
Slow oxidative muscle fibers.
Type IIb muscle fibers
What option is associated with Type IIa fibers?
It has the fastest contractions.
Its appearance has a white color.
Utilizes both anaerobic and aerobic respiration to make ATP.
Utilized for quick bursts of movement for very short moments
Utilizes both anaerobic and aerobic respiration to make ATP
Creatine phosphate is utilized primarily which type of muscle fiber?
Type II.
Type IIb.
Type Ia.
Type Ib.
Type IIc.
Type IIb
Myoglobin within the muscle fiber will allow for better anaerobic respiration to produce ATP.
False.
True.
F, because it is used for storage of oxygen (aerobic)
Which muscle fiber has the fastest ATPase activity?
Type IIa.
Type II.
Type I.
Type IIb.
Type IIb
What type of muscle fiber is largely dependent upon cellular respiration?
Type Ia muscle fibers.
Type II muscle fibers.
Type IIa muscle fibers.
Type I muscle fibers
Type I muscle fibers
Which muscle fiber has the slowest myosin ATPase activity?
Type I muscle fibers.
Type Ia muscle fibers.
Type II muscle fibers.
Type IIa muscle fibers.
Type Ib muscle fibers.
Type I muscle fibers
Postural muscles are associated with this type of muscle fiber?
Type II muscle fibers.
Type IIa muscle fibers.
Type Ib muscle fibers.
Type I muscle fibers.
Type I muscle fibers
All the options are true, except?
Type IIa muscle fibers are red in appearance.
Skeletal muscle cells store a small amount of ATP within them.
Type IIb muscle fibers have low to no myoglobin concentration.
Aerobic respiration is only associated with Type I fibers
Aerobic respiration is only associated with Type I fibers
T or F
Smooth muscle has striations and sarcomere
F
Do not have striations or sarcomere
T or F
Smooth muscle has thick and thin filaments
T
Name the two types of smooth muscle.
Where are they located and how do they work? How are they innervated?
- Unitary Smooth Muscle (Visceral Muscle) - Located: GI tract, Uterus, Urogenital tract
- Cells have gap junctions (electrically coupled)
- Contract as a unit-unison
Innervated by ANS, Hormones, and stretching
- Multi-Unit Smooth Muscle - Located: Tunica media, Bronchioles, Eyes, Dermis
- DO NOT HAVE Gap Junction
-Each muscle cell has to receive stimulus input - Have varicostities
Innervated by ANS, Hormones, NOT from Stretching
What is a myosin light chain and what does it involve?
Part of the thick filament,
- Has myosin light chain kinase (MLCK)
*Adds a phosphate group (phosphorylation) to the myosin head to active ATPase activity. Allows for it bind to actin - Has myosin light chain phophatase (MLCP)
*Removes the phosphate group (dephospohrylation) from the myosin head. Inhibits ATPase activity and prevents it from binding to actin.
What does a phosphate do to a protein?
Activate the protein = Kinase
Briefly explain the 5 steps of smooth muscle contraction.
- Stimulus - meets potential threshold
- Increase of ICF of Calcium ions - From the ECF (voltage gated Ca 2+ channels) and/or Sarcoplasmic Reticulum
- Calcium ions bind to calmodulin activating it - Leads to activation of myosin light chain kinase (MLCK); Inhibition of caldesmon and calponin
- Activated MLCK activates the myosin light chain
- Cross bridge and Power stroke
T or F
Smooth muscle has troponin
F
It has calmodulin with binds calcium ions that come into the smooth muscle cell
T or F
Kinase is not active unless calmodulin is bound to calcium
T
Explain the process of smooth muscle relaxation.
- Intracellular Calcium (Ca 2+) Ions Decrease
* Stimulus is removed or no longer leads to threshold potential
* Voltage gated Calcium (Ca 2+) close * Increase uptake of Calcium (Ca 2+) ions back into sarcoplasmic reticulum * Remove Calcium (Ca 2+) ions from the sarcoplasm back into the ISF
* Calcium (Ca2+) ATPase pump
* Calcium (Ca2+) - Sodium (Na +) Cotransporter pump - Activity of Myosin Light Chain Phosphatase
* Removes the phosphate from the myosin light chain
* Opposite action of active myosin light chain kinase
* Inhibits the activity of the myosin ATPase enzyme on myosin head
* Activity increases with decreased intracellular calcium (Ca 2+) ion concentration
What are latch-bridges?
A subset or class of cross-bridges between myosin heads and actin.
These latch-bridges basically keep the thick and thin filaments linked together for a prolonged periods of time (without the need for ATP)
What are latch-bridges?
A subset or class of cross-bridges between myosin heads and actin.
These latch-bridges basically keep the thick and thin filaments linked together for a prolonged periods of time (without the need for ATP)
All of the options are true regarding smooth muscle types, except?
• A. Unitary smooth muscle has gap junctions
• B. Multi-unit smooth muscle cells can contract independently of each other
• C. Unitary smooth muscle contract as a unit
• D. Multi-unit smooth muscle cells can be stimulated to contract by stretch
D
Latch-bridges are a class of cross-bridges in smooth muscle that are commonly found in smooth muscle sphincters.
* A. True
* B. False
T
All the options are true regarding smooth muscle contraction, except?
A. Most of the calcium that allows for smooth muscle contraction comes from the
ECF
B. The myosin light chain kinase becomes activated by calmodulin
C. When the myosin head binds calcium, it can bind with actin
D. Myosin light chain phosphatase needs to be activated for smooth muscle relaxation to occur
C
Oxygen presence is necessary for Type IIb muscle fibers to contract?
• A. True
• B. False
F
Creatine phosphate allows for the production of ATP from ADP and provides minutes of activity
as an energy source?
* A. True
* B. False
F, because creatine phosphate allows for explosive anaerobic activites
All the following statements about smooth muscle are true, except?
A. Latch bridges allow for a sustained tonic level of tension in the smooth muscle with little consumption of ATP.
B. In the dephosphorylated state, myosin can still interact with actin.
C. There is a well-developed network of T-tubules found within smooth muscle cells.
D. Myosin-light-chain kinase is activated by the Calcium (Ca2+) ion - Calmodulin complex.
C
All of the statements about smooth muscle are true, except?
A. Smooth muscle cells only have one nucleus.
B. Most of the calcium ions (Ca2+) ions that lead to contraction enter the cytoplasm from the sarcoplasmic reticulum, not the ECF.
C. Smooth muscle can sustain prolonged contraction with minimal energy expenditure.
D. All smooth muscle contraction is involuntarily.
B,
Most of the calcium ions that produce
contraction enter the muscle cell from the ECF; not the sarcoplasmic reticulum
What option best describes smooth muscle cells?
A. Not striated, involuntary, uninucleate.
B. Striated, voluntary, multinucleate.
C. Not striated, voluntary, multinucleate.
D. Striated, involuntary, uninucleate
A
What is the role of the myosin light chain phosphatase?
A. Removes the phosphate group from the myosin light chain.
B. None of the options are correct.
C. Leads to the hydrolyzing of ATP.
D. Assists with the binding of thick filament to the thin filament
A
All of the statements are true regarding excitation-contraction coupling in smooth muscle, except?
A. The amount of tension generated in smooth muscle is proportional to the intracellular Calcium (Ca2+) ion concentration.
B. Calcium (Ca2+) ions bind to actin light chain kinase to ultimately allow for a cross bridge to occur.
C. Myosin-light-chain kinase (MLCK) phosphorylates the light chain in myosin heads and increases myosin ATPase activity.
D. Relaxation of smooth muscle occurs when the intracellular calcium (Ca2+) ion concentration decreases.
B
Which of the following enzymes is responsible for dephosphorylating myosin light chains, thereby causing smooth muscle relaxation?
A. Protein kinase A.
B. Myosin light chain phosphatase.
C. Acto-myosin ATPase.
D. Myosin light chain kinase.
B
Which of the following describes the cells of unitary smooth muscle?
A. The muscle cells are coupled to one another by gap junctions.
B. The muscle cells contract as a unit.
C. The muscle cells are commonly found in the viscera of the body.
D. All of the options are true regarding unitary smooth muscle
D
In smooth muscle, the primary role of gap junctions is:
A. To rapidly transfer an action potential to adjacent cells.
B. Serve as channels for the influx of calcium ion.
C. To form latch bridges for sustained contraction.
D. Ensure synchronous firing of the smooth muscle fibers in multi-unit smooth muscle.
A
Smooth muscle latch-bridges keep the thick and thin filaments linked together for a prolonged periods of time with limited need for ATP?
True.
False
T
Unitary smooth muscle has the capability to contract as a unit because each muscle cell has its own nerve innervation.
False.
True.
F
