Muscular System Chapter 9 3 types of muscular tissue:
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Transcript of Muscular System Chapter 9 3 types of muscular tissue:
Muscular System
Chapter 9
3 types of muscular tissue:
Functions of muscular system
Stabilize joints Muscle tone Movement Maintain constant body temperature
Muscle structure Fascia – connective tissue around muscle, becomes the tendon
Origin – on stationary bone
Insertion – on the moveable bone
Fascicle – bundle of muscle fibers
Muscle fiber – muscle cell
Myofibril – made of sarcomeres (in-between two Z bands)
Myo-filaments – actin and myosin
Group Actions
Prime mover – the muscle that causes the desired movement
Antagonist – relax during the action
Synergists – muscles that steady the movement (helpers)
The Neuromuscular Junction: Neurons
Parts of : Cell body Dendrites – receive
impulse Axon – carries impulse
away Myelin sheath- white
fatty material• Schwann cells (pns)• Neurilemma (outside the
sheath)• Nodes of Ranvier
The Nerve Impulse
Action potential – steps in the nerve impulse
3 stages of : polarization, depolarization, repolarization
Step 1: Polarization
Resting state of a neuron Sodium/potassium pump – sodium ions
out of cells and potassium ions into cells
Polarization continued
Inside of the cell is – charged Outside of cell is + charged Due to sodium-potassium pump
– 2 K+ ions go in as 3 Na++ go out
http://faculty.washington.edu/chudler/introb.html
Step 3: repolarization
Return to resting state Due to the pumping out of K+. Na+ blocked Inside of cell negative
Continues to synapse
The Sliding Filament theory: Step 1: Neuromuscular Junction
Action potential – the reversal of charges across the plasma membrane.
Nerve impulse arrives at axon terminal releasing acetylcholine (Ach)
Step 1: Neuromuscular Junction
Ach diffuses across synaptic cleft, binds to receptors in the motor end plate.
Triggers action potential
Acetylcholinersterase in cleft destroys Ach to stop action potential
Disorders at the neuromuscular junction
Myasthenia gravis
Botulism
Curare
tetanus
Step 2:
Sarcoplasmic reticulum stimulated to release calcium ions.
Step 3
Release of Calcium causes shift in troponin (actin)
Active site on Actin is uncovered
Step 4
Myosin and ATP combines with active site on actin causing formation of a crossbridge
Step 5 - 7
Energy released causing filaments to slide past each other (power strokes)
ATP converted ADP Troponin slides back Cycle repeats if enough
calcium and ATP are present
Energy for contraction
ATP (respiration) Creatine phosphate-can be stored
longer and more abundant than ATP Glycogen-storage of glucose in liver
Oxygen Debt-strenuous exercise
Lack of oxygen availability
Accumulation of lactic acid (soreness)
Become short of breath to metabolize lactic acid
Muscular Responses
All or nothing response single fiber contracts only maximally– Threshold stimulus
Recruitment -
Types of Whole muscle contraction
Twitch contraction – not a usual method of muscle contraction
Summation -
Muscle not allowed to relax in-between contractions
Stronger contraction
Tetanus
sustained muscle contraction (maintaining posture or tone)
Usual means of movement
Isotonic vs. Isometric
Isotonic contraction Movement produced
as a muscle pulls on an attached bone toward a stationary structure
Isometric contraction
Muscle tension, no shortening of muscles
No movement
Muscle Fiber types
Based on genetics Classified by respiration and the speed
of contraction Strength Training can influence
Fast Twitch Fibers
Energy for quick, forceful contractions
Contraction 2-3 times faster than slow twitch
Anaerobic respiration Short term activities –
basketball, sprinting, volleyball
Slow twitch muscle fibers
Aerobic respiration Slow contracting Endurance type
activities Ex. Long distance
running, soccer, football, basketball