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Definition
In the walls of hollow organs, e.g., stomach, urinary bladder, and airways
Uninucleate
Not striated
Involuntary |
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Definition
| striated, intercalated discs, involuntary, mononuclear |
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Definition
| voluntary, striated, multi-nucleate, powerful |
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Definition
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Definition
| ability to recoil to resting length |
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| Major Muscular System Functions: |
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Definition
Movement of bones or fluids (e.g., blood)
Maintaining posture and body position
Stabilizing joints
Heat generation (especially skeletal muscle) |
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| Each muscle is served by: |
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Definition
one artery, many arterioles, many capillaries; one nerve, many axons, many axonal terminals
one or more veins |
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Definition
| a layer of connective tissue, which ensheaths the entire muscle. |
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Definition
| meaning within the muscle, is a layer of connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers. It also contains capillaries, nerves, and lymphatics. It overlies the muscle fiber's cell membrane: the Sarcolemma. |
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Definition
| fibrous connective tissue surrounding fascicles(groups of muscle fibers) (strong!) |
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Definition
| glycogen storage, myoglobin for O2 storage |
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Definition
| a deep invagination of the sarcolemma, which is the plasma membrane, only found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell. |
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Term
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Definition
| A myofibril is a basic unit of a muscle. Muscles are composed of tubular cells called myocytes or myofibers. Myofibers are composed of tubular myofibrils. composed of long proteins such as actin, myosin, and titin, and other proteins that hold them together. |
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Term
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Definition
One part of a myofibril - Smallest contractile unit (functional unit) of a muscle
The region of a myofibril between two successive Z discs
Composed of thick and thin myofilaments made of contractile proteins |
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Definition
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Definition
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Definition
| 2 interwoven, heavy polypeptide chains |
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Definition
2 smaller, light polypeptide chains that act as cross bridges during contraction
Binding sites for actin of thin filaments
Binding sites for ATP
ATPase enzymes |
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Term
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Definition
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Term
| Sarcoplasmic Reticulum (SR) |
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Definition
Network of smooth endoplasmic reticulum surrounding each myofibril
Pairs of terminal cisternae form perpendicular cross channels
Functions in the regulation of intracellular Ca2+ levels |
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Term
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Definition
| to fold inward or to sheath. |
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Term
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Definition
| impulses deep into muscle fiber (voltage sensors) |
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Term
| Requirements for Skeletal Muscle Contraction: |
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Definition
Neural Activation:
neural stimulation at a neuromuscular junction
Muscle Cell Excitation- Contraction Coupling
Generation and propagation of an action potential along the sarcolemma
Final trigger: due to a brief rise in intracellular Ca2+ levels |
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Term
| What is the Neuromuscular Junction? |
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Definition
Situated midway along the length of a muscle fiber
Axon terminal and muscle fiber are separated by a space called the synaptic cleft
Synaptic vesicles of axon terminal contain the neurotransmitter acetylcholine (ACh)
Sarcolemma contain ACh receptors |
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Term
| 3 step: electro - chemical process |
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Definition
Depolarization – initiating a charge
Propagation of action potential
Repolarization – resetting the resting membrane potential |
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Term
| Events at the Neuromuscular Junction: |
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Definition
Nerve impulse (action potential) arrives at axon terminal
Causing Ca ions to flow into the axonal terminal
Presence of Ca causes vesicles containing ACh to migrate to the membrane
ACh is released by exocytosis into the synaptic cleft
ACh binds to receptors on the sarcolemma
Ach binding opens Na channels – Na flows into the muscle cell
This leads to the generation of an action potential on the sarcolemma = transfer of electrical energy to chemical energy and back to electrical energy - called depolarization |
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Term
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Definition
Na+ channels close and voltage-gated K+ channels open
K+ is pumped out rapidly - restores the resting membrane potential
Fiber cannot be stimulated and is in a refractory period until repolarization is complete and …
Ionic conditions of the resting state are restored |
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Term
Role of Calcium (Ca2+) in Contraction/
At low intracellular Ca2+ concentration: |
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Definition
Tropomyosin blocks the active sites on actin
Myosin heads cannot attach to actin
Muscle fiber is relaxed |
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Term
Role of Calcium (Ca2+) in Contraction/
At higher intracellular Ca2+ concentrations: |
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Definition
Ca2+ binds to troponin
Troponin changes shape and moves tropomyosin away from active sites
Events of the cross bridge cycle occur (myosin heads rise & bind with actin, ATP activates the cocking action which moves the actin filament in a power stroke)
When nervous stimulation ceases, Ca2+ is pumped back into the SR and contraction ends |
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Definition
Continues as long as the Ca2+ signal and adequate ATP are present
Working (power) stroke - myosin head sticks and pulls the thin filament toward M line |
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Definition
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Definition
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Definition
| no shortening - muscle tension increases but does not exceed the load |
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Definition
| muscle shortens because muscle tension exceeds the load |
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Term
| muscle mass is increased by: |
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Definition
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Term
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Definition
| a motor neuron and all (few to several hundred) muscle fibers it supplies |
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Term
| Muscle fibers from a motor unit are spread throughout the muscle so that - |
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Definition
| 1 single motor unit causes a weak contraction of entire muscle |
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Term
| Motor units in a muscle usually contract: |
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Definition
| asynchronously - helps prevent fatigue |
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Term
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Definition
| Response of a muscle to a single, brief threshold stimulus |
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Term
| 3 phases of a muscle twitch: |
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Definition
Latent period: events of excitation-contraction coupling
Period of contraction: cross bridge formation; tension increases
Period of relaxation: Ca2+ reentry into the SR; tension declines to zero |
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Term
| Variations in the degree of muscle contraction are called - |
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Definition
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Term
| Graded Muscle Responses are graded by: (2) |
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Definition
Changing the frequency of stimulation
Changing the strength of the stimulus |
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Term
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Definition
| stimulus strength at which the first observable muscle contraction occurs |
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Term
| Contraction force is precisely controlled by: |
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Definition
| recruitment (multiple motor unit summation), which brings more and more muscle fibers into action |
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Term
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Definition
| Constant, slightly contracted state of all muscles |
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Term
| Isotonic contractions are either: |
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Definition
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Term
| Isotonic contractions/concentric |
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Definition
| the muscle shortens and does work |
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Term
| Isotonic contractions/eccentric |
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Definition
| the muscle contracts as it lengthens |
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Term
| the only source used directly for contractile activities is: |
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Definition
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Term
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Definition
Direct phosphorylation
ADP + creatine phosphate (CP) |
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Term
| Anaerobic Glycolysis – without oxygen |
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Definition
70% of maximum contractile activity:
Bulging muscles compress blood vessels
Oxygen delivery is impaired
Pyruvic acid is converted into lactic acid
2 ATP yield
60 seconds duration |
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Term
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Definition
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Term
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Definition
Slowly diffuses into the bloodstream
Used as fuel by the liver, kidneys, and heart
Converted back into pyruvic acid by the liver |
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Term
| Aerobic Pathway – with oxygen |
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Definition
Produces 95% of ATP during rest and light to moderate exercise
Fuels: stored glycogen, then bloodborne glucose, pyruvic acid from glycolysis, and free fatty acids |
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Term
| in citric acid cycle, one glucose molecule gets you: |
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Definition
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Term
| myofilaments in smooth muscles are arranged: |
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Definition
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Term
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Definition
| Provide the major force for producing a specific movement |
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Definition
| Oppose or reverse a particular movement |
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Definition
Add force to a movement
Reduce undesirable or unnecessary movement |
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Definition
| Synergists that immobilize a bone or muscle’s origin |
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Term
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Definition
Location—bone or body region associated with the muscle
Shape—e.g., deltoid muscle (deltoid = triangle)
Relative size—e.g., maximus (largest), minimus (smallest), longus (long)
Direction of fibers or fascicles—e.g., rectus (fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis)
Number of origins—e.g., biceps (2 origins) and triceps (3 origins)
Location of attachments—named according to point of origin or insertion
Action—e.g., flexor or extensor, muscles that flex or extend, respectively |
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Definition
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Definition
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Term
| Arrangement of Fascicles/Circular - |
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Definition
| Fascicles arranged in concentric rings |
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Term
| Arrangement of Fascicles/Convergent - |
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Definition
| Fascicles converge toward a single tendon insertion (e.g., pectoralis major) |
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Term
| Arrangement of Fascicles/Parallel - |
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Definition
| Fascicles parallel to the long axis of a straplike muscle (e.g., sartorius) |
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Term
| Arrangement of Fascicles/Fusiform - |
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Definition
| Spindle-shaped muscles with parallel fibers (e.g., biceps brachii) |
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Term
| Arrangement of Fascicles/Pennate - |
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Definition
| Short fascicles attach obliquely to a central tendon running the length of the muscle (e.g., rectus femoris) |
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