PSIO 201 Exam 3 Flashcards
Why are gap junctions important?
They allow the cells to contract in a coordinated fashion
What is a neuromuscular junction?
A site where a nerve fiber communicates with a muscle fiber
In the heart, what triggers the wave of electrical excitation that causes the heart to contract?
Pacemaker
When acetylcholine binds to its receptors on the motor end plate, an ion channel opens & what ions diffuse quickly into the muscle cell?
Sodium
What is the process by which action potentials of a nerve fiber lead to action potentials in the muscle fiber called?
Excitation
What is acetylcholine?
The neurotransmitter released at a neuromuscular junction
Temporal summation leads to a state of fluttering contraction known as what?
Incomplete tetanus
All of the muscle fibers innervated by a single nerve fiber constitute what?
Muscle unit
What is the indented region of the sarcolemma that participates in the neuromuscular junction called?
Motor end plate
Muscles with what fascicle arrangement produce the strongest contractions?
Pennate
What is the immediate trigger for the contraction of smooth muscle?
Calcium ions
What fascicle arrangement produces the weakest muscle?
Circular
What is excitation-contraction coupling?
The events that link the action potential of the sarcolemma to the activation of the myofilament contraction
What are the alternating light and dark bands in skeletal muscle?
Striations
What refers to the bundles of muscle fibers, wrapped in connective tissue, within a muscle?
Fascicles
The synaptic knob does not touch the muscle fiber but is separated by what structure?
Synaptic cleft
Within a synapse, a neuron ends in a swelling called what?
Axon terminal
What fibers do skeletal muscles contain?
Slow oxidative & fast glycolytic
A muscle shortens as it maintains tension in a what type of contraction?
Concentric
The thickened notched ends of cardiac muscle cells which contain gap junctions are called what?
Intercalated discs
What is calmodulin?
A protein that replaces troponin in smooth muscle cells
In smooth muscle, which protein does calcium bind to?
Calmodulin
On a myogram, the time between the stimulus & the twitch is known as what?
Latent period
What is the type of muscle contraction in which there is a change in length, but no change in tension?
Isotonic
What is a quick cycle of contraction in a whole muscle that occurs when a threshold level stimulus is reached?
Twitch
The autonomic nervous system is important in the control of which 2 types of muscle tissue?
Smooth & cardiac
Action potentials spread across the sarcolemma & continue down which structures into the sarcoplasm?
T tubules
What occurs during the contraction phase of a muscle twitch?
It generates tension, pulling on its attachments
During which phase of muscle contraction is calcium transported back into the cisternae & tropomyosin moves back to block the actin active sites?
Relaxation
What is a starch-like carbohydrate that provides energy during intense exercise in muscle cells?
Glycogen
What affects the strength of a muscle twitch?
How stretched the muscle was before stimulation
What are the functions of smooth muscle?
Regulate pupil diameter, move material through the digestive tract, & constrict or dilate blood vessels to control blood pressure
In an NMJ, after acetylcholine diffuses across the synaptic cleft, where does it bind to ligand-gated channels?
On the sarcolemma
Regarding skeletal muscle contraction, what is excitation?
The process by which action potentials in a nerve fiber lead to action potentials in a muscle fiber
What describes cardiac muscle tissue?
Striated, usually uninucleate, branching
What fibers are adapted for a quick response?
Fast glycolytic
At the synaptic knob of the motor neuron, calcium stimulates exocytosis of the synaptic vesicles to release what neurotransmitter into the synapse?
Acetylcholine
What occurs during the relaxation phase of a myogram?
Muscle tension declines
What is the muscle tissue that is typically slow to contract & slow to relax?
Smooth
A synapse is the point where a nerve fiber meets a target cell. When the target cell is a muscle fiber, what is this type of synapse called?
Neuromuscular junction
Which protein makes up the thick filaments of a myofibril?
Myosin
Which tissue can propel content of a digestive organ?
Smooth muscle
What are the characteristics of cardiac muscle cells?
Resistant to fatigue, contract with regular rhythm, contract nearly in unison
What is the 5th step of muscle relaxation?
Tropomyosin covers the myosin binding sites
During relaxation, where is calcium actively pumped back into?
Sarcoplasmic reticulum
What type of contraction involves the development of tension but no change in length?
Isometric
What is a sustained contraction in a whole muscle that occurs when a threshold level stimulus is reached?
Tetany
What is true of endurance exercise?
It increases oxygen transport in the blood
What is the perimysium?
A connective tissue sheath bundling many muscle fibers into a fascicle
Cardiac muscle cells are considered what because they contract rhythmically & independently?
Autorhythmic
What produces incomplete tetanus?
Temporal summation
What are fibers that are well adapted to anaerobic respiration called?
Fast-twitch
What are the characteristics of cardiac muscle?
Rich in myoglobin, large stores of glycogen, & uses aerobic respiration almost exclusively
In smooth muscle cells, what binds the dense bodies to the membrane?
Intermediate filaments
Within skeletal muscle cells, what extends from one Z disc to the next & constitutes one contractile unit?
Sarcomere
What is the enzyme that breaks down acetylcholine?
Acetylcholinesterase (AChE)
In flexing the elbow, what is the prime mover?
Brachialis
What type of tension develops during the latent period of muscle contraction?
Internal
The movement of an object or load results from the development of what kind of tension?
External
In what condition are stimuli are so frequent that the muscle cannot relax, & the muscle twitches fuse into a smooth prolonged contraction?
Tetanus
What fibers contain a fast-acting ATPase & phosphagen enzymes?
Fast-twitch
When a nerve signal arrives at a synaptic knob, which voltage-gated channels open in the knob?
Calcium
What is not naturally seen in the muscles of the body?
Complete tetanus
When lifting something heavy, which type of contraction occurs first?
Isometric
During relaxation, active-transport pumps in the sarcoplasmic reticulum move which ion from the sarcoplasm into the cisternae?
Calcium
Which phase of contraction links the action potential in the sarcolemma to the activation of the myofilament?
Excitation-contraction coupling
What occurs when calcium binds to troponin?
The troponin-tropomyosin complex changes shape & exposes the myosin binding sites (active sites)
What describes the endomysium?
A loose connective tissue layer that surrounds each individual muscle cell
What structures coordinate contraction in cardiac muscle cells?
Gap junctions
Where is cardiac muscle found?
In the heart wall
Which muscle tissue is rich in myoglobin, mitochondria, glycogen, & uses aerobic respiration almost exclusively for its energy needs?
Cardiac
What must occur before tropomyosin can shift, revealing the active sites that allow myosin heads to bind to the actin filaments?
Calcium must bind to troponin
Fatigue resistance is improved by what type of exercise that enhances the delivery & use of oxygen?
Endurance
What is the 2nd step of muscle relaxation?
AChE breaks down ACh down
Stimulus frequency affects the sarcoplasmic concentration of what?
Calcium
What is the red pigment that stores oxygen needed for muscular activity in muscle cells called?
Myoglobin
What are the functions of skeletal muscle?
Heat production, blood sugar regulation, control of body openings & passages, movement, joint stability
What are connective tissue structures that attach bone to muscle called?
Tendons
Cardiac muscle tissue is autorhythmic but what can increase or decrease the heart rate & contraction strength?
Autonomic nervous system
What is the 1st step of muscle relaxation?
The nerve signal ceases
What regulatory protein is associated with the thick filament of smooth muscle & activates myosin light-chain kinase?
Calmodulin
What is the role of acetylcholinesterase?
It breaks down ACh, ending muscle stimulation
What is the 3rd step of muscle relaxation?
Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae
What is another term for prime mover?
Agonist
What are the pockets of sarcolemma smooth muscle cells that contain calcium channels?
Caveolae
On a myogram, how does the relaxation phase compare to the contraction phase?
The relaxation phase is longer
What is the 4th step of muscle relaxation?
Calcium releases from troponin
What are slow-twitch fibers also known as?
Red fibers
What are fibers that are well adapted to aerobic respiration called?
Slow-twitch
What is the continuous forceful contraction in a muscle with no relaxation between stimuli?
Complete (fused) tetanus
What does skeletal muscle contraction help produce?
Body heat
What explains why cardiac muscle is resistant to fatigue?
Cardiac muscle uses little anaerobic fermentation
