POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at...

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


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


Muscles: Summary


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


Anatomy Review: Muscle Fiber Structure

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-3b

Ultrastructure of Muscle


Anatomy Summary: Skeletal Muscle

Figure 12-3a (2 of 2)

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12-3e


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.



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


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



Figure 11-12 (2 of 3)



Figure 11-12 (3 of 3)


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


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


Muscle fiber

Motor end plate

AChAxon terminal ofsomatic motor neuron

Sarcoplasmic reticulum

ActinTroponin

Tropomyosin

Myosinhead

Z disk


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



Animation: Muscular System: The Neuromuscular JunctionPLAY

M line

Ca2+

Distance actin moves

Ca2+

released


(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


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.


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



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



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



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


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


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


Electrical and Mechanical Events in Muscle Contraction

A twitch is a single contraction-relaxation cycle


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



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



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


Motor Units: Fine motor movements have more innervationsMotor Units: Fine motor movements have more innervations


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.


Isotonic and Isometric Contractions


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.


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).


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


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


Smooth Muscle layer orientations


Cellular details of smooth muscle


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.

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