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POWERPOINT® LECTURE SLIDE PRESENTATIONby LYNN CIALDELLA, MA, MBA, The University of Texas at AustinAdditional Material by J. Padilla exclusively for Physiology 31 at ECC
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
HUMAN PHYSIOLOGYAN INTEGRATED APPROACH FOURTH EDITION
DEE UNGLAUB SILVERTHORN
UNIT 2UNIT 2
PART A
12Muscles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Three Types of Muscle
Figure 12-1a
Cylindrical shaped, multinuclei, straited, voluntary, fibers of different speeds
Branched, uni-/binuclei, involuntary, striated, rhythmic contractions
Spindled shaped, one nucleus, involuntary, non-straited, internal organs
Cylindrical shaped, multinuclei, straited, voluntary, fibers of different speeds
Branched, uni-/binuclei, involuntary, striated, rhythmic contractions
Spindled shaped, one nucleus, involuntary, non-straited, internal organs
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles: Summary
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Skeletal Muscle
Usually attached to bones by tendons- sometimes attached directly to bone (pectoralis major)
Origin: closest to the trunk- usually does not move a joint when contracts.
Insertion: more distal- moves joint when contracts
Flexor: brings bones together- decreases angle at joint
Extensor: bones move away- increases angle at joint
Antagonistic muscle groups: flexor-extensor pairs- antagonistic muscles are usually in opposite sides.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-3a (1 of 2)
Anatomy Summary: Skeletal Muscle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy Review: Muscle Fiber Structure
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-3b
Ultrastructure of Muscle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy Summary: Skeletal Muscle
Figure 12-3a (2 of 2)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-3e
Ultrastructure of Muscle
Myosin are motor proteins. 250 myosins join to form the thick filaments. The thin filament is made up of a string of actin with tropomyosin and tropnin attached. Titin and nebulin anchor and stabilize.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Ultrastructure of Muscle
Figure 12-3c–f
Myofibril
A bandZ disk
Z disk Z disk
I bandM line H zone
Z diskSarcomere
Thin filaments
Tropomyosin
Troponin
Actin chain G-actin molecule
Myosin tail
Myosinheads
Myosin molecule
(c)
(d)
(e)
Thick filaments
Hingeregion
(f)Titin
Nebulin
Titin
M lineM line
Actin and myosin form crossbridgesActin and myosin form crossbridges
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-7
Summary of Muscle Contraction
Muscle tension: force created by muscleLoad: weight that opposes contractionContraction: creation of tension in muscleRelaxation: release of tension
Muscle tension: force created by muscleLoad: weight that opposes contractionContraction: creation of tension in muscleRelaxation: release of tension
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Neuromuscular Junction: Overview
Terminal boutons- insulate the site of the neuromuscular juction and secrete supportive growth factors
Synaptic cleft- space between the axon terminal and the sarcolemma Acetylcholine- neurotransmitter released involves
calcium and binds to nicotinic receptors
Motor end plate- folds on the sarcolemma of the muscle On muscle cell surface
Nicotinic receptors
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11-12 (1 of 3)
Anatomy of the Neuromuscular Junction
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Neuromuscular Junction
Figure 11-12 (2 of 3)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Neuromuscular Junction
Figure 11-12 (3 of 3)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanism of Signal Conduction
Axon terminal (of presynaptic cell) Action potential signals acetylcholine release
Motor end plate – series of folds in the plasma membrane of the postsynaptic cell Two acetylcholine bind
Opens cation channel
Na+ influx – K+ efflux
Membrane depolarized
Stimulates fiber contraction as a result in increased intracellular calcium concentration
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11-13a
Events at the Neuromuscular Junction
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-4
T-tubules and the Sarcoplasmic Reticulum
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-11a, step 1
Excitation-Contraction Coupling
Muscle fiber
Motor end plate
AChAxon terminal ofsomatic motor neuron
Sarcoplasmic reticulum
ActinTroponin
Tropomyosin
Myosinhead
Z disk
Myosin thick filament
M line
T-tubule
DHPreceptor
Ca2+
Somatic motor neuron releases ACh at neuro-muscular junction.
(a)
1
1
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-11a, steps 1–2
Excitation-Contraction Coupling
Muscle fiber
Motor end plate
AChAxon terminal ofsomatic motor neuron
Sarcoplasmic reticulum
ActinTroponin
Tropomyosin
Myosinhead
Z disk
Myosin thick filament
M line
T-tubule
DHPreceptor
Ca2+
Somatic motor neuron releases ACh at neuro-muscular junction.
Net entry of Na+ through ACh receptor-channel initiates a muscle action potential.
Na+
K+
(a)
potential
1
Action
2
1
2 Action potential
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-11b
Excitation-Contraction Coupling
Animation: Muscular System: The Neuromuscular JunctionPLAY
M line
Ca2+
Distance actin moves
Ca2+
released
Myosin thick filament
(b)
Action potential in t-tubule altersconformation of DHP receptor.
DHP receptor opens Ca2+
release channels in sarcoplasmic reticulum and Ca2+ enters cytoplasm.
Ca2+ binds to troponin, allowing strong actin-myosin binding.
Myosin heads execute power stroke.
Actin filament slides toward center of sarcomere.
3 4 5
6 7
3
4
5
6
7
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-8
Changes in Sarcomere Length during Contraction
Animation: Muscular System: Sliding Filament TheoryPLAY
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-10a
Regulatory Role of Tropomyosin and Troponin
In the relaxed state the myosin head is at 90o but it is unbound to actin because the binding sites on actin are blocked.
In the relaxed state the myosin head is at 90o but it is unbound to actin because the binding sites on actin are blocked.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-10b
Regulatory Role of Tropomyosin and Troponin**
PiADP
G-actin moves
Cytosolic Ca2+
Tropomyosin shifts,exposing binding
site on G-actin
TN
Power stroke
Initiation of contraction
Ca2+ levels increasein cytosol.
Ca2+ binds to troponin.
Troponin-Ca2+ complex pulls tropomyosin away from G-actin binding site.
Myosin binds to actin and completes power stroke.
Actin filament moves.
(b)
1
2
3
4
51
2
3
4
5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-9, steps 1–2
The Molecular Basis of Contraction
ATP bindingsite
Myosinbindingsites
Tight binding in the rigor state. The crossbridge is at a 45° angle relative to the filaments.
Myosinfilament45 °
G-actin molecule
ATP binds to its binding siteon the myosin. Myosin thendissociates from actin.
ATP
1 2 3 4 1 2 3 4
1 2
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-9, steps 3–4
The Molecular Basis of Contraction
The ATPase activity of myosinhydrolyzes the ATP. ADP andPi remain bound to myosin.
The myosin head swings over and binds weakly to a new actin molecule. The cross-bridge is now at 90º relative to the filaments.
Pi
Pi
ADP 90°
1 2 3 41 2 3 4
3 4
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-9, steps 5–6
The Molecular Basis of Contraction
At the end of the power stroke,the myosin head releases ADP and resumes the tightly boundrigor state.
ADP
Release of Pi initiates the powerstroke. The myosin head rotateson its hinge, pushing the actinfilament past it.
Pi
Actin filament moves toward M line.
1 2 3 4 5 1 2 3 4 5
5 6
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-9
The Molecular Basis of Contraction
At the end of the power stroke,the myosin head releases ADP and resumes the tightly boundrigor state.
ATP bindingsite
ADP
Tight binding in the rigor state. The crossbridge is at a 45° angle relative to the filaments.
Myosin filament
45°
G-actin molecule
ATP binds to its binding siteon the myosin. Myosin thendissociates from actin.
The ATPase activity of myosinhydrolyzes the ATP. ADP andPi remain bound to myosin.
ATP
The myosin head swings over and binds weakly to a new actin molecule. The crossbridge is now at 90º relative to the filaments.
Pi
Pi
ADP
90°
Release of Pi initiates the powerstroke. The myosin head rotateson its hinge, pushing the actinfilament past it.
Pi
Actin filament moves toward M line.
Contraction-relaxation
Slidingfilament
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4 5
1 2 3 4 5
1
6
2
3
5 4
Myosinbindingsites
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Muscle Fatigue: Multiple Causes
Extended submaximal exercise Depletion of glycogen
stores
Short-duration maximal exertion Increased levels of
inorganic phosphate
May slow Pi release from myosin
Decrease calcium release
Potassium is another factor in fatigue
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Length-Tension Relationships in Contracting Muscle
Figure 12-16
The strength of the contraction is related to the length before the muscle contracts. Very short fibers do not produce much tension because there is a lot of overlap not allowing for much sliding and not many new crossbridges. At optimum lenght there is an optimum number of cross-bridges to there is optimum tension. At a longer length there is less overlap and less ability to produce optimal force
The strength of the contraction is related to the length before the muscle contracts. Very short fibers do not produce much tension because there is a lot of overlap not allowing for much sliding and not many new crossbridges. At optimum lenght there is an optimum number of cross-bridges to there is optimum tension. At a longer length there is less overlap and less ability to produce optimal force
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-12
Electrical and Mechanical Events in Muscle Contraction
A twitch is a single contraction-relaxation cycle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summation of Contractions
Figure 12-17a
Stimuli is too far apart and allows the muscle to relax and lose tension
If action potentials come in at a closer time they recruit more fibers and the additive effect results in increased muscle tension
Stimuli is too far apart and allows the muscle to relax and lose tension
If action potentials come in at a closer time they recruit more fibers and the additive effect results in increased muscle tension
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summation of Contractions
Figure 12-17c
The more stimulus the more fibers recruited until there is a maximum tension but is there is alot of time between the stimulus the muscle relaxes resulting in an unfused tetanus
The more stimulus the more fibers recruited until there is a maximum tension but is there is alot of time between the stimulus the muscle relaxes resulting in an unfused tetanus
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summation of Contractions
Figure 12-17d
Complete tetanus results when action potentials arrive close enough to not allow the muscle to relax. Maximum tension can only be sustained for a limited time because fatigue
Complete tetanus results when action potentials arrive close enough to not allow the muscle to relax. Maximum tension can only be sustained for a limited time because fatigue
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Units: Fine motor movements have more innervationsMotor Units: Fine motor movements have more innervations
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanics of Body Movement
Isotonic contractions create force and move load- creates force and moves a load. Concentric action is a shortening action- contraction
that flexes the joint while working against a load
Eccentric action is a lengthening action- contraction that extends the joint while resisting a load
Isometric contractions create force without moving a load- the muscle produces tension and contracts but does not move the joint.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-19
Isotonic and Isometric Contractions
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-24
Muscle Contraction
Duration of muscle contraction of the three types of muscle- in smooth muscle contraction and relaxation happen slower and can be sustained for a longer time.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Smooth Muscle: Properties
Uses less energy- can maintain maximum tension while using only a small percentage of the total maximum cross bridge
Maintain force for long periods- allows organs to be tonically contracted and maintain tension for a long time (sphincter muscles)
Low oxygen consumption- allows for to maintain tension for a long time without fatiguing (bladder).
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Smooth Muscle
Smooth muscle is not studied as much as skeletal muscle because
It has more variety- impossible to come up with a single muscle function model- special types for vascular, gastrointestinal, urinary, respiratory, reproductive, and ocular
Anatomy makes functional studies difficult- fibers within cells and muscle layers within organs run indifferent directions.
It is controlled by hormones, paracrines, and neurotransmitters
It has variable electrical properties- contraction is not triggered only action potential
Multiple pathways influence contraction and relaxation- acts as an integrating center to interpret mutiple excitatory and inhibitory signals that may arrive at the same time
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IV. Smooth Muscle- A tissue formed by uninucleated spindle shaped cells found in six areas of the body: blood vessel walls, respiratory tract, digestive tubes, urinary organs, reproductive organs, and the eye.
Smooth Muscle LocationsSmooth Muscle Locations
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Smooth Muscle layer orientations
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Cellular details of smooth muscle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Muscle Disorders Muscle cramp: sustained painful contraction –
hyperexcitability of the motor unit, countered with stretching Overuse – excessive use that causes tearing in the muscle
structures (fibers, sheaths, tendon connection) Disuse- loss of muscle activity causes muscle atrophy because
of loss of blood flow, can recover is disuse is less than a year Acquired disorders – infectious diseases and toxin poisoning
that lead to muscle weakness or paralysis Inherited disorders -
Duchenne’s muscular dystrophy – muscle degenrates from pelvis up, happens most often in women, people live to be 20-30, die of respiratory failure Dystrophin –links actin to proteins in cell membrane
McArdle’s disease – limited exercise tolerance Glycogen to glucose-6-phosphate – enzyme missing thus
muscles do not have the energy source available.