Muscle TissueMuscle TissueHandout #5 Muscles and Handout #5 Muscles and #6 Excitation-Contraction#6 Excitation-Contraction

A. Types of muscleA. Types of muscle B. Functions of muscleB. Functions of muscle C. Characteristics of muscleC. Characteristics of muscle D. Anatomy and innervation of skeletal D. Anatomy and innervation of skeletal muscle tissuemuscle tissue

1. Nerve and blood supply1. Nerve and blood supply 2. Connective tissue components2. Connective tissue components 3. The motor unit3. The motor unit 4. The neuromuscular junction4. The neuromuscular junction 5. Microscopic anatomy of muscle5. Microscopic anatomy of muscle a. Myofibrilsa. Myofibrils b. Sarcoplasmic reticulum b. Sarcoplasmic reticulum and transverse tubulesand transverse tubules

E. Contraction of skeletal muscleE. Contraction of skeletal muscle 1. Sliding filament mechanism1. Sliding filament mechanism a. Role of calcium a. Role of calcium and regulator proteinsand regulator proteins b. The power stroke b. The power stroke and the role of ATPand the role of ATP 2. Relaxation2. Relaxation 3. Muscle tone3. Muscle tone 4. Homeostasis of 4. Homeostasis of body temperaturebody temperature

F. Adjusting muscle tensionF. Adjusting muscle tension 1. Twitch1. Twitch 2. Frequency of stimulation2. Frequency of stimulation a. Tetanusa. Tetanus b. Staircase effect (treppe)b. Staircase effect (treppe) 3. Number of muscle cells contracting3. Number of muscle cells contracting 4. Isotonic and isometric contractions4. Isotonic and isometric contractions

G. Cardiac muscleG. Cardiac muscle H. Smooth muscleH. Smooth muscle

Motion results from alternating Motion results from alternating contraction (shortening) and contraction (shortening) and

relaxation of muscles.relaxation of muscles.

The prime function of muscle is to:The prime function of muscle is to:

convert chemical energy (ATP) into convert chemical energy (ATP) into mechanical energy in order to:mechanical energy in order to:

1. generate force1. generate force

2. perform work2. perform work

3. produce movements3. produce movements

Types of Muscle TissueTypes of Muscle Tissue

1. skeletal muscle1. skeletal muscle

2. cardiac muscle2. cardiac muscle

3. smooth muscle3. smooth muscle

Functions of Muscle TissueFunctions of Muscle Tissue

1. motion1. motion

2. stabilizing body positions and2. stabilizing body positions and

regulating organ volume regulating organ volume

3. thermogenesis3. thermogenesis

Characteristics of Muscle TissueCharacteristics of Muscle Tissue

1. excitability (irritability)1. excitability (irritability)

2. contractility2. contractility

3. extensibility3. extensibility

4. elasticity4. elasticity

Anatomy of Skeletal MuscleAnatomy of Skeletal Muscle

Blood supply and innervation of skeletal Blood supply and innervation of skeletal muscle tissuemuscle tissue

FasciaFascia

1. superficial1. superficial

2. deep2. deep

Superficial fascia

Deep Fascia

Connective Tissues of Skeletal MuscleConnective Tissues of Skeletal Muscle

1. epimysium1. epimysium

2. perimysium2. perimysium

-- fascicles-- fascicles

3. endomysium3. endomysium

______________________________

4. tendon4. tendon

5. tendon sheath5. tendon sheath

6. aponeurosis6. aponeurosis

Microscopic AnatomyMicroscopic Anatomy

1. myofiber1. myofiber

2. sarcolemma2. sarcolemma

3. sarcoplasm3. sarcoplasm

4. myofibrils4. myofibrils

5. myofilaments5. myofilaments

6. sarcomeres6. sarcomeres

Skeletal Muscle Anatomy Skeletal Muscle Anatomy SummarySummary

SarcomereSarcomere1. Z disc1. Z disc

2. thin and thick myofilaments2. thin and thick myofilaments

2. A bands and I bands2. A bands and I bands

3. striations3. striations

Thin MyofilamentThin Myofilament1. actin1. actin

a. actin filaments (2)a. actin filaments (2) b. myosin-binding sitesb. myosin-binding sites

2. tropomyosin2. tropomyosin3. troponin3. troponin

______________________________________________4. tropomyosin-troponin complex4. tropomyosin-troponin complex

Thick MyofilamentThick Myofilament1. myosin1. myosin

2. filamentous tail (shaft)2. filamentous tail (shaft)

3. globular head (cross 3. globular head (cross bridge)bridge)

______________________________________

4. titan (elastin filament)4. titan (elastin filament)

Sarcoplasmic ReticulumSarcoplasmic Reticulum1. intracellular tubules1. intracellular tubules

2. stores Ca++ at rest2. stores Ca++ at rest

3. releases Ca++ when stimulated3. releases Ca++ when stimulated

4. Ca++ diffuse into sarcoplasm4. Ca++ diffuse into sarcoplasm

Transverse TubulesTransverse Tubules1. tunnel-like infoldings of sarcolemma1. tunnel-like infoldings of sarcolemma

2. lie at right angles to myofibrils2. lie at right angles to myofibrils

3. filled with ECF3. filled with ECF

4. terminal cisternae4. terminal cisternae

5. muscle triad5. muscle triad

The Nerve Muscle RelationshipThe Nerve Muscle Relationship

1. motor neuron1. motor neuron

2. motor unit2. motor unit

3. precise 3. precise vsvs gross control gross control

4. What is recruitment?4. What is recruitment?

The Neuromuscular JunctionThe Neuromuscular Junction1. axon terminals1. axon terminals2. synapse and synaptic cleft2. synapse and synaptic cleft3. motor end plate3. motor end plate4. synaptic vesicles4. synaptic vesicles5. neurotransmitter =5. neurotransmitter =

acetylcholine (ACh)acetylcholine (ACh)7. exocytosis7. exocytosis8. ACh receptors on 8. ACh receptors on

motor end platemotor end plate

Neuromuscular JunctionNeuromuscular Junction

Excitation-Contraction CouplingExcitation-Contraction Coupling

Sliding filament theorySliding filament theory

1. thick myofilaments attach to thin myofilaments1. thick myofilaments attach to thin myofilaments

2. cross bridges "tilt" or swivel2. cross bridges "tilt" or swivel

3. thin myofilaments "slide" across thick 3. thin myofilaments "slide" across thick myofilamentsmyofilaments

4. Z discs are drawn together4. Z discs are drawn together

5. sarcomeres shorten5. sarcomeres shorten

Sliding filament theorySliding filament theory

Excitation-Contraction CouplingExcitation-Contraction Coupling

Power StrokePower Stroke

1. ACh stimulates motor end plate1. ACh stimulates motor end plate

2. action potential crosses 2. action potential crosses sarcolemma, T-tubules, and sarcolemma, T-tubules, and sarcoplasmic reticulumsarcoplasmic reticulum

3. Ca++ channels open3. Ca++ channels open

a. Ca++ bind T-T complexa. Ca++ bind T-T complex

b. Ca++ activate ATPaseb. Ca++ activate ATPase

4. cross bridges bind and swivel4. cross bridges bind and swivel

Cross Bridge CycleCross Bridge Cycle

Recovery stroke (muscle relaxation)Recovery stroke (muscle relaxation)

1.1. acetylcholinesterase acetylcholinesterase

2.2. calsequestrincalsequestrin

Summary of Muscle ContractionSummary of Muscle Contraction

Muscle ToneMuscle Tone

1. sustained, small contractions of motor 1. sustained, small contractions of motor unitsunits

2. few motor units contracting, others 2. few motor units contracting, others relaxedrelaxed

3. muscle firmness without producing 3. muscle firmness without producing movementmovement

4. essential for maintaining posture4. essential for maintaining posture

5. asynchronous firing of motor units5. asynchronous firing of motor units

Muscle Metabolism During Muscle Metabolism During ContractionContraction

1. aerobic1. aerobic

2. phosphagen2. phosphagen

3. glycogen-lactic acid3. glycogen-lactic acid

Phosphagen SystemPhosphagen System

What is oxygen debt?What is oxygen debt?

The difference between oxygen consumption The difference between oxygen consumption at rest and oxygen consumption following at rest and oxygen consumption following exercise.exercise.

This "debt" must be "repaid" in order to:This "debt" must be "repaid" in order to:1. replace the body's oxygen reserves1. replace the body's oxygen reserves2. replenish the phosphagen system2. replenish the phosphagen system3. oxidize accumulated lactic acid3. oxidize accumulated lactic acid4. serve the elevated metabolic rate post-4. serve the elevated metabolic rate post-exerciseexercise

Physiological Classes of Muscle Physiological Classes of Muscle FibersFibers

1. slow oxidative, slow-twitch, red, or type I fibers1. slow oxidative, slow-twitch, red, or type I fibersabundant mitochondria, myoglobin, and capillariesabundant mitochondria, myoglobin, and capillariesaerobic respirationaerobic respiration

2. fast glycolytic, fast-twitch, white, or type II 2. fast glycolytic, fast-twitch, white, or type II fibersfibers

poor in mitochondria, myoglobin, and capillaries poor in mitochondria, myoglobin, and capillaries rich in enzymes of the phosphagen and glycogen rich in enzymes of the phosphagen and glycogen

pathwayspathwaysvast sarcoplasmic reticulum (rapid Ca++ movement)vast sarcoplasmic reticulum (rapid Ca++ movement)anaerobic respirationanaerobic respirationfatigue quicklyfatigue quickly

3. intermediate fibers (at least 3 types)3. intermediate fibers (at least 3 types)

Homeostasis of Body Homeostasis of Body TemperatureTemperature

Controlled Condition-Controlled Condition- A stimulus or stress disrupts homeostasis by causing A stimulus or stress disrupts homeostasis by causing body temperature to decrease below normal.body temperature to decrease below normal.

Receptors-Receptors-Thermoreceptors, located in the skin and in the hypothalamus, Thermoreceptors, located in the skin and in the hypothalamus, detect the decreased body temperature and provide nervous input to the detect the decreased body temperature and provide nervous input to the hypothalamus.hypothalamus.

Control Center-Control Center- The hypothalamic temperature control center integrates the The hypothalamic temperature control center integrates the input, then provides output that leads to stimulation of skeletal muscles.input, then provides output that leads to stimulation of skeletal muscles.

Effectors-Effectors- In response, large skeletal muscle groups increase their muscle In response, large skeletal muscle groups increase their muscle tone involuntarily (shivering).tone involuntarily (shivering).

Return to Homeostasis-Return to Homeostasis- Due to the inefficient use of energy by contracting Due to the inefficient use of energy by contracting skeletal muscles, heat is generated, the body temperature increases, and the skeletal muscles, heat is generated, the body temperature increases, and the negative feedback loop turns off the shivering.negative feedback loop turns off the shivering.

.

BODY TEMPERATURE CONTROL

CONTROLLED CONDITIONA stimulus or stress disrupts

homeostasis by causing a decrease in body temperature

RECEPTORThermoreceptors in skin and

hypothalamus are activated and send nerve impulses to the control center

CONTROL CENTERHypothalamic control center initiates nerve impulses that lead to stimulation of skeletal

muscles

EFFECTORSLarge skeletal muscle groups increase

their muscle tone involuntarily (shivering)

end

RETURN TO HOMEOSTASISDue to inefficient use of energy by contracting skeletal muscles, heat generated raises body temperature

negative feedback

Regulation of Body TemperatureRegulation of Body Temperature

Behavior of Whole MusclesBehavior of Whole Muscles

Adjusting muscle toneAdjusting muscle tone

1. all-or-none principle1. all-or-none principle

2. threshold stimulus2. threshold stimulus

Adjusting muscle tone -- The amount of force Adjusting muscle tone -- The amount of force (tension) that a muscle can generate depends (tension) that a muscle can generate depends

upon four factors:upon four factors:

1. frequency of stimulation of muscle fibers 1. frequency of stimulation of muscle fibers by motor neuronsby motor neurons

2. length of muscle fibers before they 2. length of muscle fibers before they contractcontract

3. number of muscle fibers contracting at 3. number of muscle fibers contracting at any one time (number of activated motor any one time (number of activated motor units) -- process of recruitmentunits) -- process of recruitment

4. structural components of the muscle itself4. structural components of the muscle itself

Length Tension RelationshipLength Tension Relationship

Twitch ContractionsTwitch Contractions

1. latent period1. latent period

2. contraction period2. contraction period

3. relaxation period3. relaxation period

4. refractory period4. refractory period

Treppe contractionsTreppe contractions(staircase phenomenon)(staircase phenomenon)

Wave SummationWave Summation

1. incomplete tetany1. incomplete tetany

2. complete tetany2. complete tetany

Isotonic versus Isometric Isotonic versus Isometric ContratctionsContratctions

Cardiac MuscleCardiac Muscle

1. striated1. striated

2. single nucleus/cell2. single nucleus/cell

3. intercalated discs3. intercalated discs

4. functional syncytium4. functional syncytium

5. involuntary5. involuntary

6. self-stimulating6. self-stimulating

Smooth MuscleSmooth Muscle

1. non-striated1. non-striated

2. no sarcomeres2. no sarcomeres

3. single nucleus/cell3. single nucleus/cell

4. two types4. two types

a. visceral a. visceral

(functional syncytium)(functional syncytium)

b. multiunitb. multiunit