Term
| the types of muscle in the human body |
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Definition
-skeletal
-smooth
-cardiac
[image] |
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Term
| the muscles tat do not have striations |
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Definition
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Term
| what causes striations in skeletal and cardiac muscle? |
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Definition
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Term
| what all muscle types have in common |
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Definition
-Contraction occurs by sliding of actin & myosin filaments
-Excitation/contraction coupling relies on increases in intracellular calcium |
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Term
| Contraction occurs in all muscle types by... |
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Definition
| sliding of actin & myosin filaments |
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Term
| Excitation/contraction coupling in all muscle types relies on... |
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Definition
| increases in intracellular calcium |
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Term
| some general details about skeletal muscles |
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Definition
-Sarcomere is the smallest contractile unit, giving it a striated (striped) appearance
-Control by somatic motor neurons |
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Term
| some general details about cardiac muscles |
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Definition
-Sarcomere is the smallest contractile unit, giving it a striated (striped) appearance
-Pacemaker cells: automatic rhythmic action potentials & contractions
-Regulation of strength & frequency of contraction by autonomic motor neurons |
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Term
| some general details about smooth muscles |
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Definition
-No sarcomeres; no striated appearance
-Control by autonomic motor neurons |
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Term
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Definition
| smallest contractile unit of muscle cell |
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Term
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Definition
serially-repeating sarcomeres (a single muscle cell contains many myofibrils)
[image] |
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Term
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Definition
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Term
|
Definition
bundle of muscle fibers
[image] |
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Term
|
Definition
bundle of fasciculi
[image] |
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Term
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Definition
| plasma membrane of a muscle cell |
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Term
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Definition
| cytoplasm of a muscle cell |
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Term
| SARCOPLASMIC RETICULUM (SR) |
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Definition
| specialized endoplasmic reticulum of a muscle cell |
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Term
| possibly the only cell type in the adult human body with multiple nuclei |
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Definition
| muscle cells (they're polynucleated) |
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Term
| Muscle cells appear striated due to... |
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Definition
| dark & light banding pattern of sarcomeres |
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Term
| general anatomy of a muscle cell |
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Definition
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Term
| some components to how skeletal muscles work |
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Definition
-The motor unit
-The neuromuscular junction
-Excitation/contraction coupling
-Sarcomere structure & the sliding filament model of contraction |
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Term
| A motor unit is comprised of... |
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Definition
a single motor neuron (alpha-motor neuron) and all of the muscle fibers (cells) it innervates
[image] |
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Term
| depiction of a motor unit |
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Definition
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Term
| the number of muscle cells innervated by a single motor neuron varies depending on... |
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Definition
-the motor neuron you look at
-the part of the body is being controlled |
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Term
| A typical motor neuron innervates how many muscle cells? |
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Definition
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Term
| One muscle cell is typically innervated by how many motor neurons? |
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Definition
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Term
| A ______ is comprised of many motor units |
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Definition
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Term
| All muscle fibers in the same motor unit are of the same type, characterized by... |
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Definition
-speed
-strength
-fatigability |
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Term
| example of a muscle controlled by many motor neurons |
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Definition
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Term
| example of a muscle controlled by fewer motor neurons |
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Definition
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Term
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Definition
| how quickly a muscle tires out |
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Term
| neuromuscular junction (NMJ) |
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Definition
| specialized synapse between the somatic motor neuron’s nerve terminal and the motor end plate of the skeletal muscle cell |
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Term
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Definition
small piece of plasma membrane on the skeletal muscle that receives the signal from the terminal of the motor neuron
[image] |
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Term
| depiction of the neuromuscular junction |
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Definition
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Term
| how neurons stimulate muscle cells |
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Definition
| An action potential propagated by the motor neuron typically results in an action potential across the muscle cell membrane |
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Term
| excitation/contraction (E/C) coupling |
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Definition
| Transformation of this electrical signal (in the muscle cell) into contraction of sarcomeres |
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Term
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Definition
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Term
| composition of the sarcolemma |
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Definition
-T (transverse)-tubules invaginate the myofibrils
-T-tubules are continuous with the sarcolemma
[image] |
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Term
| composition of the sarcoplasmic reticulum (SR) |
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Definition
-Terminal cisternae are closely apposed to the T-tubules
-The SR surrounds myofibrils as a network of interconnected sarcotubules
[image] |
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Term
|
Definition
-part of the sarcolemma
-invaginate the myofibrils
-continuous with the sarcolemma
[image] |
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Term
|
Definition
-part of the sarcoplasmic reticulum (SR)
-closely apposed to the T-tubules
[image] |
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Term
|
Definition
A subunit of striated muscle fiber that consists of successive sarcomeres. Myofibrils run parallel to the long axis of the muscle fiber, and the pattern of their filaments provides the striations characteristic of striated muscle cells.
[image] |
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Term
| depiction of how excitation/contraction coupling occurs at the neuromuscular junction |
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Definition
[image]
-not shown in the picture, but the Na channels are expressed all over the membrane of that sarcolemma |
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Term
| the neurotransmitter at the neuromuscular junction |
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Definition
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Term
| the receptor acetylcholine binds to at the motor-end plate |
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Definition
| nicotinic acetylcholine receptors (nAChRs) |
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Term
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Definition
| dihydropyridine receptors |
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Term
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Definition
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Term
| 2 proteins that are critical for E/C coupling |
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Definition
-dihydropyridine receptors (DHPRs)
-ryanodine receptors (RyRs) |
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Term
| dihydropyridine receptors (DHPRs) |
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Definition
integral membrane protein that's inserted into the membrane of the sarcolemma within the T-tubules
[image] |
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Term
| ryanodine receptors (RyRs) |
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Definition
integral membrane protein inserted into the membranes of those terminal cisternae, which are part of the SR that lie very close to the T-tubules
[image] |
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Term
| depiction of the physical coupling of the dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs) and what it does |
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Definition
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Term
| the sequence of events that leads to muscle contraction |
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Definition
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|
Term
| A single muscle cell contains many... |
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Definition
|
|
Term
| A myofibril is comprised of... |
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Definition
| serially-repeating sarcomeres --> striated appearance |
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Term
| the smallest contractile unit of a muscle cell |
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Definition
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Term
| the filaments in a sarcomere |
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Definition
-Thin filaments: actin
-Thick filaments: myosin |
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Term
| Sarcomeres shorten during muscle contraction (with or without) a change in length of their filaments |
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Definition
without
“sliding filament model” of muscle contraction |
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Term
| the thin filaments in a sarcomere are based on... |
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Definition
|
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Term
| the thick filaments in a sarcomere are based on... |
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Definition
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Term
| depiction of the components of the sarcomere |
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Definition
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Term
| 2 proteins in the thin (F-actin) filaments |
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Definition
-tropomyosin
-troponin
[image] |
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Term
|
Definition
the thin (F-actin) filaments attach to this, which is the boundary of the sarcomere
[image] |
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Term
| role of tropomyosin and troponin |
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Definition
| they detect changes in the Ca concentration, which leads to conformational changes in the thin (F-actin) filament |
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Term
| the role of the head groups at the end of the thick (myosin) filaments |
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Definition
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Term
| how the sarcomere shorten |
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Definition
| the thin (F-actin) filaments and thick (myosin) filaments slide past each other |
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Term
| depiction of how all the filaments and everything else are oriented within a sarcomere |
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Definition
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Term
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Definition
the length of a thick filament
[image] |
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Term
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Definition
-traverses 2 neighboring sarcomeres
-has the Z disc in the middle of it with thin filament on either side with no overlapping thick filament within the I band
[image] |
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Term
|
Definition
the portion of the thick filaments that doesn't have any overlapping thin filaments
-it's essentially the very center of a sarcomere where you've only got thick filaments
[image] |
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Term
|
Definition
acts as a spring like connector between the Z discs and the start of those thick filaments
[image] |
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Term
| depiction of The Sliding Filament Model of Muscle Contraction |
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Definition
|
|
Term
| Muscle contraction means shortening of... |
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Definition
|
|
Term
| Shortening of muscle cells results from... |
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Definition
|
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Term
| Shortening of myofibrils means... |
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Definition
movement of Z-discs closer to one another
[image] |
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Term
| The sarcomeres shorten via... |
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Definition
sliding of thin filaments over thick filaments
[image] |
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Term
| the bands in a myofibril that do not shorten during muscle contraction |
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Definition
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Term
| the bands in a myofibril that shorten during muscle contraction |
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Definition
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Term
| Each myosin head group has |
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Definition
-an ATP-binding domain
-an actin-binding domain
[image] |
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Term
| Myosin heads will bind actin (thin filaments) only... |
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Definition
in the presence of Ca
[image] |
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Term
| the 2 positions myosin head groups can exist in |
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Definition
-“cocked” position, relative to actin, or a
-“flexed” position, relative to actin
[image] |
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Term
|
Definition
causes the sliding of thin filaments across thick filaments
[image] |
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Term
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Definition
molecular mechanism of the sliding filament model
[image] |
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Term
| what happens when cross-bridges attach to actin? |
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Definition
-power-strokes occur
-muscles contract |
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Term
| In ______ muscle, the myosin/actin interaction is inhibited |
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Definition
|
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Term
|
Definition
| the grooves of the actin filament |
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Term
| why the myosin/actin interaction is inhibited in relaxed muscle |
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Definition
| because tropomyosin, being in the groove of the actin filament, blocks the association of myosin with actin filaments |
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Term
| the 3 differrent subunits of troponin |
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Definition
-Troponin I
-Troponin T
-Troponin C |
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Term
| the C in Troponin C stands for... |
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Definition
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Term
| the sequence of events that leads to the binding of myosin with actin in a stimulated muscle |
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Definition
| Stimulated muscle: Ca interacts with troponin C --> tropomyosin moves --> myosin associates with actin |
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Term
| depiction of the troponin and tropomyosin associated with the actin filament |
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Definition
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Term
| depiction of how Ca causes E/C coupling & cross-bridge attachment |
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Definition
[image]
troponin bound to Ca pushes the tropomyosin out of the way |
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Term
| Muscle action potential results in the release of... |
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Definition
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Term
| Intracellular Ca binds to ______, leading to a shift in the ______ molecules, thus allowing for... |
|
Definition
troponin
tropomyosin
cross-bridge attachment (myosin/actin interactions)
[image] |
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Term
| Multiple ______ lead to muscle contraction |
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Definition
| cross-bridge cycles (power strokes) |
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Term
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Definition
| the smallest “quantum” of contraction: it’s the response of a muscle to a single action potential |
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Term
| As action potential frequency increases, the muscle response is called... |
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Definition
summation, unfused (incomplete) tetanus, or fused (complete) tetanus
[image] |
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Term
| depiction of types of muscle contractions and what they mean |
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Definition
| [image]
-Panel A: relatively few cross-bridges form; Ca2+i returns to baseline
-Panels B & C: force (and Ca2+i) does not return to baseline between successive twitches; more cross-bridges form
-Panel D: individual twitches cannot be distinguished; maximal cross-bridge activation (not a physiological state) |
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Term
| Individual motor units respond with ______ & sometimes ______ to make muscle contractions in vivo |
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Definition
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Term
| whole-muscle movements are generally smooth & sustained, in large part due to... |
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Definition
| asynchronous activation of multiple motor units |
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Term
| Contraction strength vs. the number of motor units |
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Definition
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Term
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Definition
when the muscle fiber stays the same length because of the weight being lifted is the same as the force applied to it
[image] |
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Term
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Definition
| activation of more motor units to make a muscle contraction |
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Term
| some things that affect the strength of contraction |
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Definition
-Number of fibers
-Frequency of stimulation
-Myofiber thickness
-Length of myofibers at rest |
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Term
| depiction of the relationship between force and velocity of muscle fiber shortening |
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Definition
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Term
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Definition
contraction in which the muscle fiber shortens while doing work
[image] |
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Term
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Definition
lengthening of the muscle fiber while it is still doing work
[image] |
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Term
| how muscle relaxation is an active process |
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Definition
| because ATP is used to move Ca out of the cytosol |
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Term
| depiction of some ways muscles make and use ATP |
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Definition
|
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Term
| some things muscles use ATP for |
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Definition
| -they use Myosin ATPases for contraction
-they use Ca2+-ATPases --> relaxation |
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Term
| some ways muscles make ATP |
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Definition
-aerobic respiration
-anaerobic respiration
-phosphocreatine
[image] |
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Term
| aerobic respiration in muscles uses... |
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Definition
oxidative phosphorylation (mitochondria)
[image] |
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Term
| anaerobic respiration in muscles uses... |
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Definition
glycogenolysis and fermentation to lactate
[image] |
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Term
| some things that determine where the ATP in a muscle comes from |
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Definition
-muscle type
-activity the muscle engages in |
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Term
| when muscles are more likely to use aerobic respiration |
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Definition
when doing light work
[image] |
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Term
| when muscles are more likely to use anaerobic respiration |
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Definition
when doing heavy work, when aerobic respiration alone isn't enough
[image] |
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Term
| things that lead to muscle fatigue |
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Definition
| Repeated activation of muscle fibers --> depletion of energy stores --> muscle fatigue |
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Term
| Factors contributing to muscle fatigue |
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Definition
| -Depletion of muscle glycogen stores
-Lactic acid accumulation
-Impaired E/C coupling (decreased release of Ca2+ from SR) |
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Term
| some things that can result from muscle fatigue |
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Definition
-Decreased force production
-Reduced rate of rise of force
-Longer time to relax |
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Term
| the types of motor units vary by... |
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Definition
-Speed of contraction
-Strength of contraction
-Fatigability |
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Term
| the 3 types of motor units in your muscles |
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Definition
-SLOW (Type I)
-FAST FATIGUE-RESISTANT (Type IIA)
-FAST FATIGABLE (Type IIX) |
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Term
| some characteristics of SLOW (Type I) muscles |
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Definition
-“Red fibers”
-Slow oxidative fibers
-Smaller diameter & less myosin --> less forceful contractions
-Fatigue-resistant
-High oxidative capacity
+Large capillary supply
+Many mito’s & oxphos enzymes
+High concentration of myoglobin (Mb) |
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Term
| why SLOW (Type I) muscle has high oxidative capacity |
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Definition
-Large capillary supply
-Many mito’s & oxphos enzymes
-High concentration of myoglobin (Mb) |
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Term
| some characteristics of FAST FATIGUE-RESISTANT (Type IIA) muscles |
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Definition
-“Red fibers”
-Fast oxidative fibers
-Medium diameter & more myosin --> intermediate forcefulness
-Fatigue-resistant
-Relatively high oxidative capacity |
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Term
| some characteristics of FAST FATIGABLE (Type IIX) muscles |
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Definition
-“White fibers”
-Fast glycolytic fibers
-Large diameter & more myosin --> greatest force
-Fatigue quickly
-Low oxidative capacity (anaerobic respiration)
+Fewer capillaries & mito’s, less Mb
+Increased glycogen stores
+Increased concentration of glycolytic enzymes |
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Term
| why FAST FATIGABLE (Type IIX) muscles have low oxidative capacity (anaerobic respiration) |
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Definition
-Fewer capillaries & mito’s, less Mb
-Increased glycogen stores
-Increased concentration of glycolytic enzymes |
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Term
| depiction of what twitches and tetanus look like in the different types of muscle fibers |
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Definition
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Term
| some components of the nervous system that control skeletal muscle |
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Definition
-Proprioceptors in musculature
-Spinal interneurons
-Lower motor neurons
-Corticospinal (pyramidal) tract
-Extrapyramidal tract |
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Term
| some proprioceptors in musculature |
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Definition
-Muscle spindle apparatus
-Golgi tendon organs |
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Term
| some lower motor neurons that come out of the spinal cord |
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Definition
-alpha-motoneurons
-gamma-motoneurons |
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Term
| components of the corticospinal (pyramidal) tract |
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Definition
-Motor cortex
-Spinal cord |
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Term
| components of the extrapyramidal tract |
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Definition
-Cerebral cortex
-Thalamus / basal ganglia / cerebellum
-Brain stem
-Spinal cord |
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Term
| depiction of the neural circuits that control skeletal muscle |
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Definition
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Term
| some descending tracts involved in control of skeletal muscle |
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Definition
-Corticospinal (pyramidal) tract
-Extrapyramidal tract |
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Term
| corticospinal tract originates in... |
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Definition
|
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Term
|
Definition
the "somatic" motorneurons
-innervation of extrafusal muscle fibers |
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Term
|
Definition
| innervation of intrafusal muscle fibers |
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Term
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Definition
| they make connections in the spinal cord between the alpha- and gamma-motorneurons |
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Term
| function of muscle spindle apparatus |
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Definition
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Term
| some details about the muscle spindle apparatus |
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Definition
-Located on intrafusal muscle fibers
-Muscle stretch --> spindle stretch --> stimulation of sensory neurons
-Increased length of muscle --> increased A.P. frequency |
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Term
| function of the lower motor neurons |
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Definition
|
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Term
| the muscle spindle apparatus senses... |
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Definition
| the stretch of the spindle apparatus |
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Term
|
Definition
| the rodlike muscle cells that engage in contraction |
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Term
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Definition
-part of the spindle apparatus
-not required for muscles to contract
-important for resetting the tension on the muscle spindle apparatus |
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Term
| depiction of the muscle spindle apparatus |
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Definition
|
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Term
| the reflex to a stretch is... |
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Definition
|
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Term
| how gamma-fibers reset the tension on the muscle spindle apparatus |
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Definition
| in response to stretches, they release acetylcholine, leading to excitatory input on the muscle spindle apparatus to reset the tension |
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Term
| an example of a monosynaptic stretch reflex |
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Definition
|
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Term
| depiction of the knee-jerk reflex |
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Definition
[image]
-not shown, but there's also gamma-motorneurons here that reach out to the intrafusal fibers on the muscle spindle apparatus and cause it to contract and return to a resting tension |
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Term
| why the knee-jerk reaction is considered monosynaptic |
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Definition
| because there's only 1 synapse responsible for making this happen |
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Term
| an example of reciprocal innervation |
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Definition
| agonist/antagonist muscles |
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Term
| depiction of agonist/antagonist muscles |
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Definition
|
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Term
| why interneurons are often inhibitory |
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Definition
| because they're GAB-ergic |
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Term
| example of double reciprocal innervation |
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Definition
|
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Term
| depiction of the crossed-extensor reflex |
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Definition
|
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Term
| the type of event the crossed-extensor reflex is |
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Definition
a nociceptive event; it involves nociceptors
[image] |
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