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Chapter 10 - Muscle Tissue
Muscle Tissue and Organization
63
Anatomy
Undergraduate 1
10/23/2011

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Term

 

 

 

Excitability

Definition

 

 

 

The ability to recieve and respond to stimuli

Term

 

 

 

Contractility 

Definition
Stimulation of muscle cells generates tension causes cells to shorten (pull on bones of skeleton). 
Term
Muscle Function
Definition

Locomotion,

Cadiac muscle,

Smooth muscle helps maintain blood pressure or propel substances

Muscles also maintain posture, stabilizes joints, generates heat

Term
Skeletal Muscle: 3 Connective Sheaths
Definition
Epimysium, Perimysium Endomysium
Term
Epimysium
Definition

(upon) dense irregular connective tissue, surrounds skeletal muscle 

 

Term
Perimysium
Definition

(around) dense irregular connective tissue, contains blood vessels and nerves

 

Term
Endomysium 
Definition
Endomysium - (within) innermost areolar connective tissue layer with reticular fibers for binding. 
Term
Myoblast
Definition

(germinating) Embryonic skeletal muscle cells, contain single nucleus

Fuse to form skeletal muscle fibers

Term
Fascile 
Definition
A bundle of muscle fibers seperated from other bundles of fibers by dense connective irregular connective tissue (perimysium)
Term
Muscle 
Definition
Multiple fascicles housing many muscle fibers, connective tissue coverings, blood vessels, nerve fibers. Covered by epimysium.  
Term
Muscle Fiber
Definition
 myofibrils, separated from other fibers by areolar connective tissue (endomysium)
Term
Myofibril
Definition
Contractile element within a muscle fiber, composed of myofilaments (striations)
Term
Myofilaments
Definition
Thick filaments(myosin) and thin filaments (actin, tropomyosin, and troponin) 
Term
Muscle order (smallest to largest)
Definition

Myofilaments (thick and thin)

Myofibril (myofilaments)

Muscle Fiber (many myofibrils)

Fascicle (many muscle fibers)

Muscle (multiple fascicles)

Term
Origin
Definition
less mobile attachment of muscle
Term
Insertion
Definition
more mobile attachment (insertion is pulled towards origin)
Term
Sarcolemma
Definition
plasma membrane of a skeletal muscle
Term
Sarcoplasm
Definition
Cytoplasm of a muscle fiber
Term
Transverse (T) Tubules 
Definition
deep invaginations into the sarcolemma that extend to the sarcoplams of skeletal muscle fibers. Helps coordinate muscle contractions 
Term
Sarcoplasmic Reticulum
Definition
Stores calcium ions needed to initiate muscle contraction. 
Term
Terminal Cisternae
Definition
Sacs within the Sarcoplasmic Reticulum (SR). Reservoirs for calcium release to initate muscle contraction
Term
Thin Filaments
Definition
two strands of protein (G actin and F actin) twisted together. 
Term
Troponin
Definition

regulatory protein

1) attaches to actin

2) attaches to tropomyosin to hold it in place

3) troponin provies a binding site for calcium ions

Term
Thick Filament
Definition
Composed of double stranded protein, myosin.
Term
A band
Definition
dark region, contains thick filament, some thin filaments sections. 
Term
I band
Definition
Composed of thin filaments only
Term
H Zone
Definition
light, central region of A band. Only thick filaments present. During contraction, thin filaments pulled into H zone and zone disappears. 
Term
M Line
Definition
Center of H zone in relaxed fiber, attachement site for thick filaments and keeps thick filaments aligned during contraction and relaxation. 
Term
Z disc
Definition
center of I band, attachement site for thin filament heads. 
Term
Sarcomere
Definition
Functional contractile unit of skeletal muscle fiber
Term
Neuromuscular Junction
Definition
Motor neuron transmits the effect of a nerve impulse to the muscle fiber at neuromuscular junction
Term
Synaptic Knob
Definition
expanded tip of the axon, when it nears the sarcolemma of a muscle fiber, it expands further to cover a relatively large surface area. Nerve impulse travels through the axon to the synaptic knob
Term
Acetylcholine (ACh)
Definition
Neurotransmitter
Term
Motor End Plate
Definition
specialized region of the sarcolemma. It folds and indentations to increase the membrane surface area covered by the synaptic knob. 
Term
ACh Receptors
Definition
In the motor end plate act like doors that normally are close. ACh is the key to open these receptor doors. 
Term
Acetylcholinesterase (AChE)
Definition
resides in the synaptic cleft, rapidly breaks down molecules of ACh that are released into the synaptic cleft. AChE is needed so that ACh will not continuously stimulate the muscle
Term
Muscle Contraction
Definition

1) A nerve impulse causes ACh release at a neuromuscular junction. ACh binds receptors on the motor end plate, initiating a muscle impulse 

2) The muscle impulse spreads quickly along the sarcolemma and into the muscle fiber along the T-tubule membranes 

3) Calcium ions bind to troponin, causing tropomyosin to move and expose active sites on actin. Myosin heads attach to the actin and form crossbridges.

4) Myosin heads go through cyclic "attach, pivot, detach, return" events as the thin filaments are pulled past the thick filaments. ATP is required to detach the myosin heads and complete the sequence. Sarcomere shortens, and the muscle contracts. Cyclic event continues as long as calcium ions remain bound to toponin. 

5) Calcium ions are moved back into the SR by ATP driven ion pumps to reduce calcium concentration in the sarcoplasm, leading to relaxation. Termination of muscle impluse results in passive sliding of myofilaments back to their original state. 

Term
Motor Unit
Definition
Single motor neuron and all the muscle fibers it controls
Term
All-or-none principle
Definition
muscle fiber either contracts completely or does not contract at all. When a motor unit is stimulated, all its fibers contract at the same time.
Term
Isometric Contraction
Definition
No movement, muscle tension is less than the resistance, muscle does not shorten
Term
Isotonic Contraction
Definition
Muscel tension equals or is greater than reisistence. The muscle shortens, movement occurs. 
Term

Concentric Contractions

(An Isotonic Contraction)

Definition
Actively shorten a muscle (lift a baby from the crib)
Term

Eccentric Contraction

(An isotonic contraction)

Definition
actively lengthen a muscle (place baby in crib without dropping)
Term
Slow fiber
Definition

1) small in diameter 

2) continue contracting for an extended period of time

3) slow to fatigue

4) Many mitochondria (to produce greater amounts of ATP)

5) Many myoglobin

6) Aerobic 

7) Extensive capillaries

Term
Fast Fibers
Definition

1) Quick ATP use 

2) Anaerobic (using vast amonts of ATP)

3) White (pale)

4) Sparse capillaries

5) fast contraction velocity

6) large diameter

7) few mitochondria

8) small myoglobin

Term
Circular Muscles
Definition
Concentrically arranged around an opening or a recess (sphincter)
Term
Parallel Muscles
Definition
Fascicles run parallel to its long axis, high endurance not very strong, Rectus abdominus 
Term
Convergent Muscles 
Definition
Triangle muscle with common attachment site (Pectoralis Major). Direction of pull can  be chantged 
Term
Pennate Muscles
Definition
Muslce body has one or more tendon. Fascicles at oblique angel to tendon. Pulls harder than a parallel muscle of equal size 
Term
Unipennate Muscle
Definition
All muscle fibers on the same side of the tendon (Extensor digitorum) 
Term
Bipennate Muscle
Definition
Muscle fibers on both sides of the tendon (Rectus femoris)
Term
Multipennate muscle
Definition
tendon branches within the muslce (deltoid)
Term
Atrophy
Definition
Wasting of the muscle tissue that results in reduction in muscle size, tone and power. Muscle atrophy is initially reversable, dead or dying muscle fibers cannot be replaced. 
Term
Hypertrophy
Definition
Increase in muscle fiber size. No increase in fiber number (hyperplasia). Increase in number of myofibrils per fiber in fast fibers. Repetitive, exhaustive stimulation results in more mitochondria, larger glycogen, and an increased ability to produce ATP. 
Term
First class lever
Definition
Fulcrum in the middle between effort and resistance (scissors, atlanto-occipital joint in the neck)
Term
Second class lever
Definition
Resistance is between the fulcrum and the applied effort (lifting handles of a wheelbarrow, plantar flexion)
Term
Third class lever
Definition
Effort is applied between the resistance and the fulcrum (Fulcrum is the joint between humerous and ulna, effort is applied by the biceps brachii, resistance is what's in the hand) 
Term
Agonist
Definition
Prime mover, muscle that contracts to produce a particular movement
Term
Antagonist
Definition
Muscle whose actions oppose those of the agonist. Agonist produces extension, antagonist would produce flexion.
Term
Synergist 
Definition
Muscle that assists the agonist in performing its action
Term
Cardiac Muscle
Definition

1) Cells are short and branching

2) one or two nuclei in the center of the cell

3) cells joined by intercellular junctions in intercalated discs

4) Sarcomere

5) t-tubules overlie Z discs

6) composed of thick and thin filaments

7) contain SR but less than skeletal muscle

8) More mitochondria than skeletal muscle

Term
Skeletal muscle
Definition

1) cells are long and cylindrical

2) multiple nuceli at the periphery of the cell

3) Cells do not have specialized intercellular junctions

4) Sarcomere

5) T-Tubules overlie A band/I band junctions

6) Composed of thick and thin filaments

7) SR but more than in cardiac muscle

8) Fewer mitchondria than in cardia muscle

Term
Naming of skeletal muscles
Definition

Muscle names incorporate the following qualities of the muscles: 

1) Appearance

2) Location

3) Function

4) Orientation

5) Unusual Features

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