Muscle Structure Ans Neuromuscular Junction Flashcards
What are the three types of muscle tissue?
Skeletal smooth and cardiac muscle
Is all muscle tissue excitable
Yes
Is all muscle tissue extensible
Yes
Is all muscle tissue under voluntary control
No, only skeletal muscle is under voluntary control
Is skeletal muscle tissue only under voluntary control
No, skeletal muscle can be controlled voluntarily or unconsciously, like the activation of the diaphragm and postural control muscles
Which muscle structure is the myocyte?
Each individual muscle fiber found in a muscle fascicle is a myocyte or muscle cell
What element of muscle structure gives the muscle it’s strength
The bundling of thousands of muscle fibers with its connective tissue
What is the sarcolemma of a myocyte?
The cell membrane
What are T tubules in the muscle fiber
Tiny tunnels that project downwards from the surface into the center of the muscle fiber
What is the cytoplasm of a myocyte called?
Sarcoplasm
What is the smooth endoplasmic reticulum of a myocyte called and what is its function?
Sarco plasmic reticulum, and it stores calcium to be released into the sarcoplasm to cause contraction of the myocyte
What are the long filaments found in the sarcoplasm?
Myofibrils
(Thin Actin and thick myosin)
What are sarcomeres
Segments of myofibrils with actin and myosin, filaments, arranged into segments shorter than the length of the myocyte
Why does skeletal muscle appear striated under a microscope?
Each myocyte is made up of hundreds of sarcomeres, and under a microscope, the myosin filaments look dark, while the actin filaments look light
What is a motor neuron?
And efferent nerve cell that sends motor signals from the brain down through the spinal cord and out from the spinal cord to the target muscle
What neurotransmitter is released at the neuromuscular junction by the motor neuron
Acetyl choline
What happens when the motor neuron releases acetylcholine at the neuromuscular junction?
Acetylcholine is taken up by acetylcholine receptors on the sarcolemma, which causes rapid shifts in ions to occur across the sarcolemma and down the T tubules to bring calcium into the Myocyte. Then the sarcoplasmic reticulum releases its own calcium into the sarcoplasm
The calcium flow into the myocyte causes the actin and myosin to bind and pull in on each other. This causes thousands of sarcomeres within each myocyte to contract all at once.
How is the Sarco plasmic reticulum involved in the relaxation of muscle contraction?
After a muscle contraction, the sarcoplasmic reticulum takes up the calcium ions and stores them again, and without calcium, the contraction ends, and the muscle relaxes
Is cardiac muscle tissue under voluntary control
No
Is cardiac muscle tissue striated
Yes
Do cardio myocytes have T-tubules, Sarcoplasmic reticulum, and sarcomeres like the skeletal muscle
Yes
What is the function of intercalated discs in cardiac muscle tissue?
To connect the cardio myocyte to adjacent cardio myocytes
What are pacemaker cells?
Specialized cardio myocytes that generate and conduct action potentials in the cardiac muscle tissue
What allows for coordinated contraction of cardiac muscle tissue?
As cardiac pacemaker cells generate an action potential, the action potential spreads to neighboring cardio, myocytes since ions can flow through intercalated discs to spread the action potential and cause coordinated contraction of cardiac muscle tissue
Is smooth muscle under voluntary control
No
Is smooth muscle striated
No, there are thick and thin myofilaments in the sarcoplasm of smooth muscle, but they are not organized into sarcomeres, and do not look striated under a microscope
Is skeletal muscle multi nucleated, or have only one nucleus in each muscle fiber
Multi nucleated
Is cardiac muscle multi nucleated, or have only one nucleus in each myocyte
One nucleus
Is smooth muscle multi nucleated or is there only one nucleus in each myocyte?
One nucleus
Where is smooth muscle found
In the walls of hollow organs, like the small and large intestines, the bladder, the uterus and blood vessels
What is the general path of an action potential in a motor neuron?
The cerebral cortex of the brain sends an action potential in an upper motor, neuron down through the spinal cord, where it activates a lower motor neuron in the anterior horn of the spinal cord, which sends the action potential through the axon of the lower motor neuron to its axon terminals to the neuromuscular junction where it meets the muscle fibers innervated by the motor neuron
What is the neuromuscular junction?
The synapse where the axon terminals meet the muscle fibers, they will innervate
What are the three main parts of the neuromuscular junction?
A pre-synaptic membrane(membrane of the axon terminal), a postsynaptic membrane(membrane of the skeletal muscle fiber, a.k.a. motor, end plate,), and the synaptic cleft (gap between the pre-and post synaptic membrane)
What happens when an action potential reaches the axon terminal at the neuromuscular junction to cause the release of acetylcholine
It stimulates voltage gated calcium channels in the membrane to open and extracellular calcium ions flow into the lower motor neuron which causes synaptic vesicles in the axon terminals to release the neurotransmitter acetylcholine into the synaptic cleft
What happens when acetylcholine is released into the synaptic cleft of the neuromuscular junction to cause depolarization of the postsynaptic membrane?
The acetyl choline, then diffusers quickly to the motor and plate on the muscle. Fiber to acetylcholine molecules, will bind to one ligand gated ion channel (a nicotinic receptor) these ligand gated ion channels, open sodium ions, rush into the skeletal muscle, fiber, and a few potassium ions leak out of the cell. This result in an increase in positive charge on the inside of the muscle fiber, and therefore, on the inside of the membrane relative to the outside of the membrane or depolarization of the postsynaptic membrane.
What does depolarization on the postsynaptic membrane do to the resting membrane potential
Depolarization on the postsynaptic membrane is called an end plate potential and it makes the resting potential of the cell membrane less negative
What happens if depolarization on the postsynaptic membrane reaches the threshold for voltage gated sodium ion channels to open?
These channels open, and there is a huge influx of sodium ions into the muscle fiber this leads to a generation of an action potential that rapidly spreads along the entire membrane and gets the entire muscle fiber to contract
What is an end plate potential?
Depolarization of the postsynaptic membrane of the neuromuscular junction
What happens when the signal sent from the lower motor neuron stops?
Voltage gated calcium channels on the pre-synaptic membrane, close the influx of calcium ions stop the synaptic, vesicles full of acetylcholine stay in the axon terminal and acetylcholine molecules left behind within the synaptic cleft are degraded by an enzyme, called acetylcholineesterase into choline and acetate
What happens to the acetate and choline degraded by acetylcholine esterase in the synaptic cleft
The acetate diffusers out from the synaptic cleft, while choline, is taken back into the axon terminal where it’s reused by the enzyme, acetylcholine transferase to make new acetylcholine molecules
How many neuromuscular junctions does each skeletal muscle fiber have
One each skeletal muscle fiber has only one neuromuscular junction so that means that each muscle cell is controlled by one lower motor neuron
How can the axon of a lower motor neuron innervate multiple muscle fibers?
The axon of a lower motor neuron splits into many branches, and each of these branches can innervate multiple adjacent muscle fibers
What is a motor unit?
The lower motor neuron and all the muscle fibers it innervates form a single motor unit and an average one motor neuron innervates 150 skeletal muscle fibers
What dictates the number of skeletal muscle fibers that are innervated by one motor neuron
The precision of the muscle, they control muscles that control precise. I movements consist of many relatively small motor units where every lower motor neuron innervates only 10 to 15 muscle fibers large muscles like the biceps brachii muscle found in your upper arm can have up to 2000 muscle fibers within a single motor unit.
Small motor, neurons, innervate_______muscle fibers
Few
Since small motor neurons have the________ Threshold’s, they fire first
Lowest
The size principle states that___________ motor units are recruited greater tension will develop
More
Large motor neurons innervate___________ muscle fibers
Many
What is an alpha motor neuron
This is another name for a lower motor neuron which relays an action potential from the anterior horn of the spinal cord through an axon to the target, skeletal muscle tissue
What are proprioceptor’s
They are sensory receptors that detect the position and movement of skeletal muscles
What are extrafusal muscle fibers?
Muscle fibers on the outside of the muscle that are innervated by lower motor neurons and provide most of the force during a muscle contraction, the attached to bones with tendons, which are a specific type of connective tissue
What are Golgi tendon organs?
Proprioceptor’s found in muscle tendons that lie at the ends of extrafusal muscle fibers
What are muscle spindles?
Proprioceptor is found within extrafusal muscle fibers
How are Golgi tendon organs and muscle spindles similar and different?
Golgi tendon organs and muscle spindles are both proprioceptor’s sensory receptors that detect the position and movement of skeletal muscles
Differences are that Golgi tendon organs are found in the tendons and detect muscle tension. Muscle spindles are found in extrafusal muscle fibers and detect muscle length
What are intra-fusel muscle fibers
Muscle fibers on the inside of the muscle spindle that have contractile proteins like actin and myosin only on the ends of the intrafusal muscle fibers so only the ends of the intrafusal muscle fibers contract
What types of sensory neurons, fire and relay information about intrafusal fiber stretch
Type one a and type two neurons
What is the role of gamma motor neurons?
Gamma motor neurons caused the end regions of the intrafusal muscle fibers to contract, which shortens and keeps it taut
Using the patellar reflex as an example, how does the stretch reflex work?
When the patellar tendon is tapped, it, stretches the extrafusal muscle fibers, and the muscle spindles
The stretched muscle tendon causes an increase in the rate of the action, potential’s being fired by the muscle, spindle and traveling through type one a and type two sensory fibers, which relay that message to cells in the spinal cord
Type 1a fibers synapse with alpha motor neurons on the leg extensors and caused these muscles to contract, which prevents damage from over stretching
At the same time, the type to fibers trigger the firing of the interneurons, which inhibits the alpha motor neurons of the leg, flexor muscles, causing them to relax the leg kicks out, and the extensor muscles are shortened
Are deep tendon reflexes like the patellar reflex controlled by the brain
No, the efferent and afferent signals are not sent or received by the brain. The entire process happens very quickly, and is controlled at the level of the spinal cord.
Does shortening or stretching of the muscle spindles trigger a reflex
Stretching (lengthening)
What is the process of alpha-gamma, co-activation?
The alpha motor neuron, a.k.a. lower motor neuron stimulates, extrafusal muscle fiber contraction, while the adjacent gamma motor neuron is stimulated to cause the contraction of the intrafusal muscle fibers in the muscle spindle, making them shorten as the muscle shortens
What is the function of alpha-gamma coactivation?
It maintains the tension of the muscle spindles and keeps themsensitive to stretch even when your muscles are contracted andprevents damage from overstretching.
What is the function of the Golgi tendon reflex?
Prevents damage from over-contraction of the muscles
How do Golgi tendon organs prevent muscle damage from over contractionof the muscles?
Golgi tendon organs (GTO) are proprioceptors found in the tendonsthat detect muscle tension. When a muscle shortens duringcontraction, the GTO in the muscle tendon gets compressed and firesoff action potentials that travel through sensory afferent fibers to thespinal cord to synapse with an inhibitory interneuron that synapse withthe alpha motor neuron of the contracting muscle and stimulatoryinterneurons of the antagonist muscles to cause some relaxation of thecontracting muscle and contraction of the antagonist muscle limitingthe tension generated in the initial muscle contraction, functioning as anegative feedback mechanism
Alpha (lower) motor neurons innervate __________ skeletal muscle fibers
extrafusal
_________ motor neurons innervate intrafusal skeletal muscle fibers
Gamma
The general function of the muscle spindle is to sense muscle ________.
Length
Alpha and gamma motor neurons coactivate so that muscle spindles remainsensitive when the muscle is _________________
Contracted
Muscle spindles are composed of __________ muscle fibers
Intrafusal
Muscle spindles run in _________________ with extrafusal muscle fibers
Parallel
When muscle is stretched, the increase in length of the intrafusal fibersactivates sensory afferent fibers from groups _________________
Ia and II
The function of the gamma motor neurons is to maintain the sensitivity ofthe ________ muscle fibers they innervate
Intrafusal
Where does the upper motor neuron synapse with the lower motor neuron to send a signal from the brain down to skeletal muscle to contract?
Anterior horn of the spinal cord
What is the name of the location where the axon terminal of the lower motor neuron reaches the target skeletal muscle?
Neuromuscular junction
Which neurotransmitter is released at the neuromuscular junction to tell the muscle to contract?
Acetylcholine
Does a myocyte have multiple nuclei or only one nucleus?
Multiple nuclei
What are the functional units of the myocyte?
Sarcomeres
What is the sarcolemma?
The cell membrane of the myocyte
What is the cytoplasm of a myocyte called?
Sarcoplasm
What are the T-tubules of the myocyte?
Tiny tunnels that project downwards from the surface towards the center of the muscle fiber.
What is the sarcoplasmic reticulum and what does it store? What does the sarcoplasmic reticulum run perpendicular to?
A special type of smooth endoplasmic reticulum that stores lots of calcium. It runs perpendicular to the T tubules.
What are myofibrils, where are they found, and what does each myofibril consist of?
Long filaments, found in the sarcoplasm, each one consists of contractile proteins and regulatory proteins.
What are the contractile proteins of the myofibrils?
Thick myosin and thin actin filaments
What are the thick myosin filaments made of and what is its shape?
They are made up of hundreds of myosin proteins, and each myosin protein has a tail and two myosin heads- it looks like two golf clubs with their handles twisted around one another. Multiple myosin proteins join their tails together to form the central part of the thick filament.
What are the thin actin filaments made of and what is its shape?
They are made up of small, globular proteins called G-actin. The G-actin proteins form a filament that looks like a long helix structure -like a twisted pearl necklace.This entire filament is called F-actin and it includes the regulatory proteins tropomyosin and troponin
What is the function of the active site on each G-actin protein?
It is where the myosin head binds to it during muscle contraction
What are the regulatory proteins of the myofibrils?
Tropomyosin and troponin
What is the function of tropomyosin?
It is a string-like protein that wraps around F-actin, covering its active sites so that the myosin heads can’t bind to it
Do the thick myosin and thin actin filaments extend the entire length of the myocyte?
No, they’re arranged in short units called sarcomeres
How does the arrangement of sarcomeres give the muscle fiber a striped(striated) appearance under an electron microscope?
The thick myosin filaments look dark, while the thin actin filaments look light which gives the muscle fiber a striped appearance.
What structure is at the center of the sarcomere where the thick filaments attach?
The M line
What structures are at the borders of the sarcomere where the thin filaments attach?
The two Z-discs
How many thin filaments are there for every thick filament?
For every thick filament, there are two thin filaments-one above and one below and the two types of filaments overlap.
What is the region of the sarcomere with only thin filaments that appears light?
The I band
How many I bands are found in each sarcomere and where are they located?
Each sarcomere unit has two half I bands at either end.
What is the region of the sarcomere with thick filaments that appears dark?
The A band
What is the region of the A band where there is only thick filament and appears slightly lighter than the rest of the A band?
Most of the A band has overlap between the thick and thin filaments, but there’s an area towards the center called the H band where there is only thick filament, so it appears slightly lighter.
What happens to the actin filaments and Z discs in the sarcomere when the muscle contracts?
The thick filaments pull the actin (thin) filaments above and below, towards the M line. The Z discs attached to the thin filament also get pulled towards the M line, and the whole sarcomere gets shorter
What happens to the A band in the sarcomere when the muscle contracts?
The A band does not change since it’s the length of the thick filament.
What happens to the H band in the sarcomere when the muscle contracts?
It shortens because as the overlap increases, the regions that consist of only thick or thin filament decreases. At maximal contraction, there’s an almost complete overlap of thick and thin filaments and it is almost completely gone.
What happens to the I band in the sarcomere when the muscle contracts?
It shortens because as the overlap increases, the regions that consist of only thick or thin filament decreases. At maximal contraction, there’s an almost complete overlap of thick and thin filaments and it is almost completely gone.
When an action potential travels along the sarcolemma and reaches the T-tubule, what type of channel is opened and what ion flows into the sarcoplasm?
A calcium channel is opened, allowing large amounts of calcium stored within the sarcoplasmic reticulum to flow out into the sarcoplasm.
What effect does calcium ions binding to troponin regulatory proteins have?
It makes them change their shape and moves tropomyosin out of the way, and that allows F actin to be bound by the myosin heads
How does the myosin head power up to bind to actin?
Part of the myosin head is an ATPase, meaning that it can cleave anATP molecule to ADP and phosphate ion and release some energy. The energy is used to cock the myosin head backwards, into its high energy position
What is it called when the myosin head binds to the active site on the actin filament?
Cross-bridge formation, this is the trigger to release the stored energy in the myosin head. When that happens, the myosin head launches towards the M line, pulling the actin (thin) filament along with it. This is called the power stroke.
What is the power stroke and what do the combined power strokes lead to?
It is when the myosin head binds to the active site on the actin filament through cross-bridge formation, and the myosin head launches toward the M line pulling the actin (thin) filament with it. The combined power strokes of all the myosin heads lead to the sliding of the thin filament along the thick filament.
What happens when the power stroke is done?
The ADP and phosphate ion leave the myosin head, and a new ATP molecule can bind instead. Once a new ATP is bound, the myosin head detaches from the active site. The new ATP is cleaved and the energy is used to re-cocking the myosin head to its high energy position for the next power stroke
What happens once the signal sent from the alpha (lower) motor neuron stops?
The action potentials end, and calcium ions are pumped back into the sarcoplasmic reticulum by calcium pumps that use ATP. When calcium levels fall, troponin is no longer bound to calcium, troponin returns to its original shape, and tropomyosin covers up the active sites on actin.
As a result, the myosin heads can no longer bind to actin, and the muscle relaxes.
During muscle contraction, actin filaments move _____________ the M line?
toward
The attachment and detachment of actin and myosin filaments occur______________ during a single muscle contraction.
several times
During muscle contraction, the I band of the sarcomere becomes_________________.
shorter
During muscle contraction, the H zone of the sarcomere _________________
shortens
During muscle contraction, the A band of the sarcomere _________________.
stays the same
____ hydrolysis releases energy which is used to move the myosin head into t’s high energy position.
ATP
ADP is released from the myosin head __________ the power stroke?
after
What is the force that skeletal muscles apply at rest to stabilize joints and bones called?
Muscle tone
What is the pulling force that skeletal muscles apply to perform an action called?
Muscle tension
Which contractile protein looks like a gently twisted pearl necklace?
Actin
Which contractile protein has a tail and 2 club-like heads?
Myosin
How can the myosin head cleave an ATP molecule to ADP and phosphate to release energy?
It is an ATPase
What five factors does the force of muscle contraction depend on?
The size of the muscle fibers, the number of muscle fibers that are active during contraction, the frequency of stimulation, the length of the sarcomere, and the velocity of muscle shortening
A ______ muscle fiber can produce a stronger contraction.
larger
A ______ of muscle fibers can produce a stronger contraction.
larger number
What does the force-frequency relationship mean for the force of a muscle contraction?
When the frequency of stimulation is increased, more calcium ions accumulate in the sarcoplasm, and the force of contraction increases
What does the length of the sarcomere mean for the force of a muscle contraction (i.e. length-tension relationship)?
The relationship is directly proportional, meaning that the length of the sarcomere is directly related to the length of the muscle. At the normal resting length, a muscle will have the maximum amount of cross-bridges available to form. If a muscle is stretched or shortened the number of potential cross-bridges decreases resulting in a weaker contraction.
What does the length of the force-velocity relationship mean for the force of a muscle contraction?
The quicker the muscle shortens the faster the actin filament is pulled towards the center of the sarcomere. When there’s a rapid contraction there’s less cross bridge formation and the result is a weaker contraction.
What is an isotonic muscle contraction?
The muscle length changes but the tension within the muscle stays the same
What is an isometric muscle contraction?
The length of the muscle stays the same, while the tension increases
What are the two main types of skeletal muscle fibers?
Slow-twitch (AKA slow oxidative fibers or type I muscle fibers) and fast-twitch muscle fibers
What are the subdivisions of fast-twitch muscle fibers?
Fast oxidative and fast glycolytic fibers
What is the subdivision of fast-twitch muscle fibers based on?
The speed of contraction and the metabolic pathway that’s used to make ATP
Do muscles typically have a mix of slow and fast twitch muscle fibers or just one type each?
Most muscles possess a mix of slow-twitch and fast-twitch fibers, but the predominant one determines the primary function of the muscle
How does the form of ATPase enzyme influence the speed of contraction?
The speed of contraction depends on how quickly the ATPase enzyme cleaves a molecule of ATP. Slow twitch fibers have an ATPase that hydrolyzes ATP slowly, and fast twitch fibers have an ATPase that hydrolyzes ATP quickly
What is the main source of ATP used by muscle fibers?
Glucose
What is the name for stored glucose in skeletal muscle cells?
Glycogen
What is the process for skeletal muscle cells to store glucose as glycogen?
Glycogenesis
What is the process for skeletal muscle cells to break down glycogen to glucose when energy is needed?
Glycogenolysis
What is glycolysis?
A set of biochemical reactions that take place in the sarcoplasm to make ATP from glucose It results in 2 molecules of pyruvate and 2molecules of ATP for every glucose molecule
Does glycolysis require oxygen?
No
What is aerobic respiration?
A process that requires oxygen where pyruvate is converted into acetyl-COA which enters the mitochondria to produce NADH via the citric acid cycle. NADH is then used to drive oxidative phosphorylation within the mitochondria, and the result is that each glucose molecule yields a total of 38 ATP
What is anaerobic respiration?
A process that occurs in the absence of oxygen or mitochondria, there’s only anaerobic respiration, or anaerobic glycolysis, which is where glucose is broken down into 2 molecules of ATP and pyruvate.The excess pyruvate gets converted into lactic acid, which goes into the blood, and then to the liver.
What does the liver do with lactic acid?
The liver can recycle lactic acid into pyruvate and then pyruvate into glucose by using 6 ATP. The new glucose can then be sent to the muscles or other organs.
Are slow-twitch muscle fibers generally larger or smaller than fast-twitch muscle fibers?
Smaller and produce the weakest contractions because they have fewer sarcomeres, but they’re well-supplied with blood vessels that bring them a plentiful supply of oxygen
What is myoglobin?
Myoglobin is like hemoglobin, which is the oxygen-carrying protein in the blood, except that myoglobin binds oxygen even more strongly than hemoglobin.
Is myoglobin found more in slow-twitch muscle fibers or fast-twitch muscle fibers?
In the sarcoplasm of slow-twitch muscles, there’s a high concentration myoglobin, which binds and stores oxygen
Do slow-twitch muscle fibers appear red or white? Why?
Red, high levels of myoglobin and an extensive network of blood vessels make these fibers appear red
Do slow-twitch muscle fibers have a large or small number of mitochondria in their sarcoplasm?
Large
Do slow-twitch fibers use up ATP slower or faster than fast-twitch fibers?
Slower
Do slow-twitch fibers need more or less glycogen storage than fast-twitch fibers?
Less, since they use up ATP more slowly and they create a lot of ATP
Do slow-twitch fibers support muscle activity over a short or long period of time?
Long
What are fast oxidative muscle fibers also known as?
Type IIa muscle fibers
How does the name fast oxidative muscle fibers help explain how they function?
“Fast” is for having the ATPase that hydrolyze ATP quickly, while “oxidative” stands for the aerobic metabolism used for generation ofATP
Are fast oxidative muscle fibers larger or smaller than slow oxidative fibers? Are they weaker or stronger?
Larger with a greater number of sarcomeres, which means that they’re also stronger
Do fast oxidative muscle fibers appear red or white? Why?
Red, just like the slow oxidative fibers, fast oxidative muscle fibers have an extensive network of blood vessels, are rich in myoglobin and filled with mitochondria because they primarily rely on aerobic metabolism. (AKA fast red muscle fibers)
Do fast oxidative muscle fibers use up ATP slower or faster than slow-twitch muscle fibers?
Since these fibers contract quickly, they use up ATP faster.
Can fast oxidative muscle fibers use aerobic and anaerobic metabolism or just one of these?
Both, they can use oxidative phosphorylation in the mitochondria which yields more ATP but takes longer to generate ATP, so these fibers can also utilize anaerobic glycolysis
Do fast oxidative muscle fibers fatigue quickly or slowly?
Relatively quickly
What are the fast glycolytic fibers also known as?
Type IIx
How does the name fast glycolytic muscle fibers help explain how they function?
“Fast” is for having the ATPase that hydrolyze ATP quickly, while“glycolytic” stands for the anaerobic pathway using glycolysis, for the generation of ATP.
How does the size of fast glycolytic muscle fibers compare with fast oxidative and slow-twitch muscle fibers?
These fibers are the largest and strongest, because they have the most sarcomeres
Do fast glycolytic muscle fibers appear red or white? Why?
White, because these fibers rely on anaerobic glycolysis, they needless oxygen and therefore have fewer blood vessels. Within their sarcoplasm, they also have low levels of myoglobin and few mitochondria making these fibers appear white (AKA white muscle fibers)
How does the storage of glycogen in fast glycolytic muscle fibers compare with fast oxidative and slow-twitch muscle fibers?
Within the sarcoplasm of the fast glycolytic fibers, there are a lot of glycogen reserves, which ensures that there is plenty of glucose available for anaerobic glycolysis metabolism during contraction.
Which muscle fiber type, slow-twitch, fast oxidative, or fast glycolytic fatigue the fastest?
Fast glycolytic muscle fibers
How many ATP per glucose molecule does anaerobic metabolism yield?
2
During anaerobic metabolism, what is pyruvate converted to?
Lactic acid
Release of which hormone causes increased heart rate and contractility, systemic vasoconstriction to visceral blood vessels, and vasodilation of skeletal muscle blood vessels?
Epinephrine
What is functional hyperemia?
Increased blood flow as a result of increased activity in a specific organ(i.e. muscles during exercise)
What is an example of a long-term body system adaptation from regular physical exercise?
Specific changes to help increase the efficiency and capacity during exercises, for example, the heart muscle hypertrophies, or enlarges, while the heart rate decreases. This allows for the same amount of blood per minute to be pumped even at rest, but the heart muscle uses less energy.
During aerobic metabolism, what is pyruvate converted to?
Pyruvate molecules enter the mitochondria and they’re converted to acetyl CoA, which can enter the Krebs cycle and go through oxidative phosphorylation for ATP regeneration
What is beta oxidation?
Free fatty acids get released into blood circulation, and then transported to the working muscle cells, where they undergo beta-oxidation, which converts free fatty acids to acetyl CoA in the mitochondria which enters the Krebs cycle and goes through oxidative phosphorylation for ATP regeneration
Once formulated, a motor plan is transmitted to the _____________ motor neurons in the primary motor cortex of the brain
upper motor neuron
Upper motor neurons that originate in the primary motor cortex descend to the lower motor neurons in the _________ horn of the spinal cord
anterior
Axon terminals at neuromuscular junctions are filled with synaptic vesicles that contain the neurotransmitter ___________.
Acetylcholine
The general visceral motor nuclei in the brain stem contain cell bodies of nerves in the _____________ preganglionic pathway
parasympathetic
When acetylcholine binds to ligand-gated channels at the neuromuscular junction, sodium ____________ the cell.
enters
When sodium enters the muscle cell at a neuromuscular junction, it _______________, leading to an end plate potential.
depolarizes
What enzyme at the neuromuscular junction degrades acetylcholine?
Acetylcholinesterase
Visceral motor responses are ___________________ than those induced by somatic motor fibers
slower
Preganglionic sympathetic axons use which neurotransmitter?
Acetylcholine
Preganglionic parasympathetic axons use which neurotransmitter?
Acetylcholine
Postganglionic sympathetic axons use which neurotransmitter?
Norepinephrine
Postganglionic parasympathetic axons use which neurotransmitter?
Acetylcholine
