Muscle Physiology:The Actions of the Sarcomere.

Cardiac MuscleCharacteristics Intercalated

disks Striated Involuntary Located in heart

Skeletal Muscle

Characteristics Many nuclei per

cell Striated Voluntary Located along

bones

NonstriatedInvoluntaryLocated in digestive tract

Smooth Muscle

Functions of Muscles

Movement: results from muscle contraction, enables you to respond quickly

Maintains Posture and Joint Stability: allows you to sit upright; stabilize joints of the body

Support Soft Tissue: abdominal muscles protect underlying digestive organs.

Guard Entrances and ExitsGenerate Heat: heat is generated as they work…FRICTION

Maintains body temperature Skeletal muscles create the most heat

Characteristics of Muscle Tissue

Excitability: ability to receive and respond to stimuli…

Contractibility: ability to shorten quickly and with force…

Extensibility: ability to be stretched or extended beyond their resting state…

Elasticity: ability of a muscle fiber to recoil and resume its resting length

Organization of Muscle

Muscles are composed of groups of fibers called fasicles.Fibers are the muscle cells inside all muscle.Tendons are bands of collagen fiber that attach muscle to bone.

Sarcomere: the contracting unit

Skeletal Muscle Striations

Z line

I band

H band

A band

Organization from the muscle fiber to the sarcomere.

Cross sectional view of Sarcomere.

Differences are detected in the sizes of the myofilaments

Myosin is the thicker fiber.

Actin is the thinner fiber.

Striations are seen because of sarcomere bands.

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Muscle fiber structure

Muscle cellSarcolemmaSarcoplasmSarcoplasmic reticulumT tubulemitochondria

Structure of Muscle Tissue

Sliding Filament Theory

Sliding Filament TheoryActin slides over myosin shortening the

sacromere between the Z lines

Chain of Events during Muscle Contraction! 1. Cross Bridge Attachment2. Power Stroke 3. Cross Bridge Detachment4. Cocking (Recoil) of Myosin Head

What happens at the sarcomere?

Players for the power stroke

Cross bridge attachmentPower strokesCross bridge detachment“Cocking” of the myosin head

                                 

Power stroke

                                  

  

Motor Unit: A motor neuron and all the muscle fibers it stimulates.

Diagram of a Muscle Twitch

Increase in muscle tension due to continued stimulation.

Muscle that reaches peak tension during rapid cycles of contraction and relaxation.

Complete tetanus = relaxation state is eliminated.

Label the following!

Aerobic Muscle Metabolism

GlycolysisAerobic Respiration Krebs Cycle ETC

Anaerobic Muscle Metabolism

Oxygen Debt

Lactic Acid Fermentation

Muscle Fatigue

Creatine Phosphate

Red (slow) twitch fibers

AerobicSlow-acting ATPases (enzymes that break down ATP) Large amounts of myoglobinRed color to cellAbundant supply of mitochondriaFatigue resistant-as long as O2 is availableHigh endurance (jogging, swimming, soccer)

White (fast) twitch fibers

Large pale cells with twice the diameter of red fibersVery little myoglobinContain fast-acting ATPases and contract rapidlyContain few mitochondria, but large glycogen storesDepend on anaerobic resp. to make ATP, therefore fatigues easilyLow endurance, much power….sprints

Pink (intermediate) twitch fibers

Mixture of red and white fibersAerobic mechanisms and fatigue resistantContain fast-acting ATPasesHigh myoglobin content