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Definition
| This term describes a muscle which has a broad origin that runs to a single tendon |
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- fascicles form circle of muscle fibers around external body opening.
Example: Orbicularis oris and oculi |
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Definition
Describes a muscle with short fibers attached to central tendon. It would resemble a feather).
Example: Extensor digitorum longus - unipennate ; Rectus femoris - bipennate |
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Definition
Long axis of fascicles run with long axis of muscle
Example: Sartorius – straplike; Biceps - fusiform |
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Definition
| Skeletal muscle consists of long, striated (striped) cells |
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| The cells have a striated appearance due to |
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Definition
| A-bandsI-bands which are alternating light and dark bands which are aligned along the length of the myofibrils. |
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| consists of long multinucleate cells with nuclei pushed to one side by myofibrils packed into the cytoplasm |
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Definition
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Definition
| are produced by alternating light and dark bands composed of thick and thin filaments. |
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| Myofibrils are composed of myofilaments which are made up of two proteins |
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Definition
| actin and myosin. Actin and myosin slide across each other during muscle contraction resulting in shortening of cell |
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Definition
| is defined as the portion of a myofibril between two Z-lines. It extends from one I band to the middle of the next and is the actual contractile unit of the muscle fiber |
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| surrounds individual muscle fibers |
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| skeletal muscles are composed of many muscle fibers bundled together by connective tissue. Layers of connective tissue help to arrange the muscle fibers into patterns: |
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Definition
Epimysium -surrounds intact muscle
Perimysium - surrounds fascicles
Endomysium - surrounds individual muscle fibers |
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Term
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Definition
| is the junction between a nerve fiber and a muscle cell. The nerve fiber carries the message to contract to the muscle fiber. |
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Definition
| consists of motor neuron and all of the muscle fibers it stimulates |
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Definition
| are mostly responsible for producing a movement while antagonists oppose or reverse a movement. |
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Definition
| aid and smooth out action of prime movers. |
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Definition
| prevent movement at the origin of a prime mover allowing all of the tension to be exerted at the insertion. |
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| Humans have three types of muscle tissue |
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Definition
| skeletal, smooth and cardiac |
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Definition
| consists of long, multinucleate cells with cross striations. voluntary muscle |
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Definition
| which is found in the heart, has branched fibers with intercalated disks which mark the boundaries between cells. This muscle is involuntary |
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Definition
| consists of spindle shaped cells which surround tubes such as in the digestive system. These cells have one nucleus and are involuntary |
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| Muscle contraction provides movement as in walking or eye movement |
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Definition
| Contraction of muscle allows us to remain upright! |
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| Tendons of muscles often extend across joints and keep them stable. |
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Definition
| Muscle contraction produces heat used to maintain body temperature |
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Term
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Definition
| refers to the ability to respond to stimuli which in muscle is usually a neurotransmitter released by a nerve cell. This chemical gives the muscle cell the “message to contract |
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Definition
| refers to the ability of a muscle cell or fiber to shorten producing movement. This property sets muscle apart from other tissues. |
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Definition
| refers to the ability of muscle fibers to be stretched or extended. |
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Definition
| refers to the ability of muscle fibers to contract or extend and return to their original length. |
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Term
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Definition
| are produced by alternating light and dark bands composed of the thick and thin filaments that make up the myofibrils. The striated appearance is due to A-bands and I-bands. |
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Term
| muscle fiber is served by |
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Definition
| 1 nerve, an artery and one or more veins. |
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Term
| Muscles attachments may be direct |
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Definition
| in which the epimysium of the muscle is fused to the periosteum of the bone |
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Term
| indirect in which attachment |
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Definition
| is by means of a tendon or sheet like aponeurosis. |
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Definition
| The interior of the cell is filled with myofibrils which are rod like contractile elements. They make up most of the muscle volume and push the nuclei to the edges of the cell |
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Term
| The arrangement of myofibrils within a muscle fiber |
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Definition
| is such that a perfectly aligned repeating series of dark A bands and light I bands is evident. |
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Term
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Definition
| is the smallest contractile unit of a muscle and is defined as the distance between 2 Z- disks. The sarcomere is composed of thick and thin myofilaments composed of contractile protein. Each sarcomere contains 1 A-band and 2 semi I bands. Thick filaments are found at center of sarcomere and thin between thick and attached at Z-disk. I Bands contain thin filaments only. A-bands contain thick with thin in between and the H-zone contains only thick |
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Term
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Definition
| actin, tropomyosin and troponin. |
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Definition
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| Thick filaments are composed of the protein myosin. |
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Definition
| Each myosin molecule has a rod-like tail and two globular heads. The tails consist of two interwoven, heavy polypeptide chains. The heads consist of two smaller, light polypeptide chains and link thick and thin filaments together forming cross bridges. |
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Term
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Definition
| of two interwoven, heavy polypeptide chains |
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Definition
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Term
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Definition
| two smaller, light polypeptide chains and link thick and thin filaments together forming cross bridges. |
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Term
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Definition
| a rod-like tail and two globular heads. The tails consist of two interwoven, heavy polypeptide chains. |
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Term
| sarcoplasmic reticulum (SR |
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Definition
| at a longitudinal section showing one sarcomere endoplasmic reticulum which basically runs longitudinally surrounding each myofibril. |
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Term
| The paired terminal cisternae |
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Definition
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Term
| functions in regulation of intracellular calcium levels |
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Definition
| The sarcoplasmic reticulum |
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Term
| The T-tubules penetrate the cell's interior at the |
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Definition
| A-band I-band junction and associated with the paired terminal cisternae to form triads |
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Term
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Definition
| which are continuous with the sarcolemma, carry impulses to the deepest parts of the muscle fiber and signal calcium release from the adjacent terminal cisternae. |
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Term
| sliding filament model explains the mechanism of contraction: |
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Definition
| Thin filaments slide past the thick ones so that the actin and myosin filaments overlap. Upon stimulation, myosin heads bind to actin and sliding begins. Each myosin head binds and detaches several times during contraction, acting like a ratchet to generate tension and move the thin filaments to the center of the sarcomere. As this occurs throughout the sarcomeres, the muscle shortens |
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Term
| In order to contract, a skeletal muscle must: |
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Definition
Be stimulated by a nerve ending
Move an action potential along its sarcolemma
Have a rise in intracellular calcium levels which is the final trigger for contraction |
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Term
| Linking the electrical signal to the contraction is called excitation-contraction coupling |
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Definition
| This is the sequence of events by which transmission of an action potential along the sarcolemma leads to sliding of myofilaments. |
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Term
| structure of neuromuscular junction involves |
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Definition
Presynaptic axonal endings which contain synaptic vesicles containing the neurotransmitter acetylcholine.
Synaptic cleft which is the space between the axon and muscle fiber.
Postsynaptic membrane which is the sarcolemma of the muscle fiber. This is called a motor end plate and contains receptors for acetylcholine |
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Term
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Definition
| which is the sarcolemma of the muscle fiber. This is called a motor end plate and contains receptors for acetylcholine. |
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Term
| Presynaptic axonal endings |
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Definition
| which contain synaptic vesicles containing the neurotransmitter acetylcholine |
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Term
| Presynaptic axonal endings |
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Definition
| which contain synaptic vesicles containing the neurotransmitter acetylcholine |
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Term
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Definition
| which is the space between the axon and muscle fiber. |
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Term
| a nerve impulse reaches the end of an axon |
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Definition
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Term
| open and allow calcium ions to enter the axon. |
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Definition
| Voltage-regulated calcium channels |
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Term
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Definition
| inside the axon terminal cause axonal vesicles to fuse with the axonal membrane |
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Term
| Calcium ions inside the axon terminal cause axonal vesicles to fuse with the axonal membrane |
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Definition
| This fusion releases acetylcholine (ACH) into the synaptic cleft via exocytosis |
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Term
| ACH diffuses across the synaptic cleft to ACH receptors on the sarcolemma. |
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Definition
| Binding of ACH to its receptors initiates an action potential in the muscle. |
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Term
| ACH bound to ACH receptors is quickly destroyed by the enzyme |
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Definition
| acetylcholinesterase. This destruction prevents continued muscle fiber contraction in the absence of additional stimuli |
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Term
| Events at the Neuromuscular Junction |
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Definition
When a nerve impulse reaches the end of an axon at the neuromuscular junction:
Voltage-regulated calcium channels open and allow calcium ions to enter the axon.
Calcium ions inside the axon terminal cause axonal vesicles to fuse with the axonal membrane.
This fusion releases acetylcholine (ACH) into the synaptic cleft via exocytosis.
ACH diffuses across the synaptic cleft to ACH receptors on the sarcolemma.
Binding of ACH to its receptors initiates an action potential in the muscle.
ACH bound to ACH receptors is quickly destroyed by the enzyme acetylcholinesterase. This destruction prevents continued muscle fiber contraction in the absence of additional stimuli. |
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Term
| This event is called depolarization |
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Definition
ACH binds its receptors at the motor end plate.
Binding opens chemically gated channels.
Because more sodium ions diffuse in than potassium ions fuse out, the interior of the sarcolemma becomes less negative |
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Term
| In order for a muscle to contract, it must receive a “message” from a motor neuron. This starts a local electrical event called |
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Definition
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Term
| This starts a local electrical event called an end plate potential. Later it ignites an |
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Definition
| action potential that spreads in all directions across the sarcolemma. |
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Term
| Excitation-Contraction Coupling |
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Definition
Once generated, the action potential:
Is propagated along the sarcolemma
Travels down the T tubules
Triggers calcium ion release from the terminal cisternae |
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Term
| Calcium ions bind to troponin causing |
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Definition
The blocking action of tropomyosin to stop
Actin active binding sites to be exposed |
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Term
| Excitation-Contraction Coupling As the process continues: |
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Definition
Myosin cross bridges alternately attach and detach.
Thin filaments move toward the center of the sarcomere.
Calcium ions are removed into the sarcoplasmic reticulum, tropomyosin blockage is restored, and the muscle fiber relaxes.
Hydrolysis of ATP powers this cycling process. |
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Term
| Role of Ionic Calcium in the Contraction Mechanism |
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Definition
At low intracellular calcium ion concentration:
Tropomyosin blocks the
binding sites on actin.
2. Myosin cross bridges cannot
attach to binding sites on actin
The relaxed state of the
muscle is enforced |
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Term
| At higher intracellular calcium ion concentrations |
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Definition
Additional calcium binds to troponin (inactive troponin binds two calcium ions).
Calcium activated troponin binds an additional two Calcium ions at a separate regulatory site. |
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Term
| Role of Ionic Calcium in the Contraction Mechanism |
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Definition
Calcium-activated troponin undergoes a conformational (“shape”) change.
2. This change moves tropomyosin away from actin’s binding sites. |
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Term
| Role of Ionic Calcium in the Contraction Mechanism |
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Definition
Myosin head can now bind and cycle
This permits contraction (sliding of the thin filaments by the myosin to begin |
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Term
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Definition
| myosin cross bridge attaches to the actin filament |
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Term
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Definition
| myosin cross bridge attaches to the actin filament |
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Term
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Definition
| myosin cross bridge attaches to the actin filament |
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Term
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Definition
| myosin cross bridge attaches to the actin filament |
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