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BIOLOGY 2401
ANATOMY & PHYSIOLOGY
Muscle Tissue and Contraction
LMobley
Kilgore College
I. Background
A. Characteristics – not A CONNECTIVE TISSUE
1. membrane potential -- excitability
a. conductivity
2. contractile
a. define motion in this context
3. extensibility
4. elasticity
B. Functions (as listed in text)
1.
2.
3.
4.
C. Types – review information in tissue chapter
1. skeletal
2. cardiac
3. smooth
II. Skeletal muscle – components
A. connective tissue components
1. tendons (long, sinewy) and aponeuroses (sheets)
2. endomysium around one muscle fiber (muscle cell)
3. perimysium around bundles called fascicles
4. epimysium around one whole muscle (muscle composed of many fascicles)
B. nerves and muscle
1. motor unit (motor neuron and muscle fibers it stimulates)
2. neuromuscular junction
C. histology - light microscope and electron microscope
1. muscle fiber microanatomy – see text and lab
2. the sarcomere and muscle proteins
a. sarcomere = unit of contractility
b. myofibrils and myofilaments
c. actin
d. myosin
e. troponin and tropomyosin - regulatory proteins
f. projection cross bridges = actin and ATP binding sites
g. elastic filament = proteins that stabilize
Biol. 2401 ltm muscle tissue and contraction printed ______ 1
III. Contraction and Relaxation of skeletal muscle fibers
A. The structural part: the sliding filament theory – shortening of the sarcomere
1. components: (see previous section)
2. functional relationships
a. power stroke – the mechanics of the sarcomere shortening
B. Excitation-Contraction Coupling
1. the role of calcium
2. length-tension
3. rigor mortis
C. The electrical part: motor unit and the neuromuscular junction
1. motor unit (the whole “thing”)
a. transmits a nerve impulse (action potential) to a skeletal muscle when
nerve impulse serves as a stimulus for contraction.
b. composed of the motor neuron and muscle fibers it stimulates
c. single motor neuron stimulates as few as 10 or as many as 2000 fibers,
average = 150 fibers
d. excitable cells (neurons and muscles) make contact and communicate at
specialized places called synapses. When a nerve or muscle cell is
stimulated, ion gates in the CM open, Na+ rushes in, K+ rushes out and
changes membrane voltage (called action potentials)
e. definitions:
1)** electrical potential -- potential energy that results from greater
concentration of charged particles at one point than at another. Measured in
volts. When charged like this it is polarized.
2)** resting membrane potential - -90mV for skeletal muscle (minus sign =
negative inside with respect to outside. determined by
a. diffusions of ions down their concentration gradient
b. selectively permeability of CM
c. electrostatic attraction cations to anions
3)** RMP due to unequal conc of K+ inside (40x more concentrated inside),
diffuses out, leaving anions (-) which cannot get out. Somewhat counteracted
by Na+ which is diffusing in (12x more concentrated in ECF). Review sodium
pump
4)** action potential: momentary reversal of RMP
2. neuromuscular junction (the “business end”)
a. description: axon terminal of motor neuron and the portion of the muscle fiber
sarcolemma in close approximation with it
b. parts of the NMJ
c. synapse
d. motor end plate
3. transmission of the current
a. ACh = neurotransmitter released through synaptic vesicles
b. receptors
c. action potential
d. termination of stimulus/response
IV. Whole muscles – next outline (separate link)
Biol. 2401 ltm muscle tissue and contraction printed ______ 2
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