CH 9.1 Types of Muscle Tissue

Muscle Functions1. Muscles make up half of body mass2. Transforms chemical energy (ATP) into mechanical energy3. Homeostatic Heat Production

a. Consumes most energy from muscle contraction Muscle Types

1. Skeletal Musclea. Produces movement by acting on the skeletonb. Maintains posturec. Stabilize joints control internal movementd. Generates heate. Contains

i. Connective Tissue Layers1. Epimysium2. Perimysium3. Endomysium

ii. Blood Vessels and Nerves1. Enter the CT and branch in the cell

2. Cardiac Musclea. Found on the heart wallb. Pumps blood through the circulatory system

3. Smooth Musclea. Found in the skin

i. Associated with hair folliclesb. Internal Organsc. Blood Vessels

i. Critical component to regulate blood pressured. Internal Passageways

i. Eg. Peristalsis in the intestines Skeletal Muscle Organization (basic levels)

1. Tendon2. Fascicle3. Muscle Fiber (Cell)4. Myofibril5. Sarcomere6. Microfilament7. Actin and Myosin

Skeletal Muscle Layers with CT (superficial to deep)Long, multi nucleated cells. Connective tissue layers highlighted.

1. Epimysium Connective Tissuea. Outer covering of fascicles

2. Fasciclesa. Bundles/groups of muscle fibers

3. Perimysium Connective Tissuea. Covers each fascicle bundle

4. Endomysium Connective Tissuea. Covers each muscle fiber (muscle cell)

5. Muscle Fibers (muscle cells)a. Many fibers makes up a single fascicleb. Nuclei are found herec. Many myofibril makes up a single muscle fiberd. Surrounded by sarcolemmae. Filled with sarcoplasm

6. Myofibrilsa. Mitochondrion found hereb. Sarcoplasmic reticulum

i. Surrounds the myofibrilii. Form of endoplasmic reticulum

iii. Many actin and myosin filaments make up a myofibril7. Myosin and Actin filaments

a. Creates banding striationsb. Forms the sliding filament mechanism

Excitability

1. Plasma membranes change electrical statesa. Polarized to depolarized

2. Sends an action potential along the membrane3. Influenced by

a. Nervous systemi. Cardiac and skeletal muscle

b. Hormones and local stimulii. Can also influence cardiac and skeletal muscle

Muscle Basic Characteristics

Skeletal Muscle

1. Contractions for body movement2. Voluntary3. Long, cylindrical, striated cells4. Multi nucleated5. Contracts rapidly, tires easily6.

Smooth Muscle

1. In walls of organs and blood vessels2. Involuntary3. Spindle-shaped, non-striated cells4. Mono nucleate5. Slow, sustained contractions

Cardiac Muscle

1. In heart wall2. Amitotic3. Involuntary4. Striated, branching cell5. Mono or binucleate6. Intercalated discs7. Self-initiating contractions

CH 9.2-3 Physiologic Functions of Muscle

Major Physiologic Functions of Muscle

1. Movementa. Molecular motors cause movement of fibersb. Causes movement of cells and bones

i. Changes bone positionc. Moves material through tubes

i. Peristalsis2. Heat Production

a. All energy not converted to mechanical energyb. Much converted to heatc. Large amounts of muscle in the body, creates large amounts of heat

3. Communicationa. Muscles control

i. Facial expressionii. Gesturing

iii. Writingiv. Typingv. Speaking

Muscle Power Efficiency

1. Power comes from ATPa. Generated by cellular metabolism

2. Biochemical efficiency for movement is 25-40%a. Balance of energy produced during contraction released as heat

CH 9.4 Muscle Properties

Major Muscle Properties1. Contractibility

a. Ability to shorten its lengthb. Requires energyc. Skeletal muscle contractions

i. Pulls bones through attached tendonsd. Smooth muscles contractions

i. Generates pressureii. Capable of forcing liquids through hollow structures (blood vessels)

2. Elasticitya. Capacity to return stretched muscle to original length

3. Excitabilitya. Capacity of muscle to respond to a stimulus to contractb. Skeletal

i. Responds to nervous systemc. Smooth and cardiac

i. Affected by nervous systemii. Also responds to physical stimulations and hormones

4. Extensibilitya. Ability to return to its original length

i. Still responds to stimulusb. Returns by

i. Elastic recoilii. Actions of other muscles

iii. Gravityiv. Fluid under pressure within a vessel

Muscle Contraction Process (basic)

1. Skeletal and Cardiac (striated muscles)a. Protein fibers: Actin is pulled by Myosin when

i. Specific binding sites shielded by proteins troponin and tropomyosinii. Exposed in response to interactions between calcium ions and proteins

2. Smooth Musclea. Protein fibers: Actin is pulled by Myosin when

i. Calcium ions activates enzymesii. Enzymes activates myosin heads to pull actin fibers

3. All muscles require ATP to continue process of contraction4. All muscles relax when calcium ions are removed and actin binding sites are re-shelided

Differences Among Three Muscle Types1. Actin and Myosin protein arrangement

a. Skeletal and Cardiac Musclei. Regular protein arrangement creating a pattern: Striations

b. Smooth Musclei. Irregular protein arrangementii. Uniform, non-striated appearance

2. Nucleia. Skeletal

i. Multinucleatedb. Cardiac

i. One or two nuclei per cellc. Smooth

i. Single nucleus3. Connections between cells

a. Cardiaci. Physically and electrically connected to each otherii. Entire heart contracts at once

b. Skeletal and Smooth Musclei. Not connected to pass electrical impulses

CH 9.5 Skeletal Muscle

Skeletal Muscle1. Ability to contract and cause movement

a. Produces movementb. Stops movement

i. Resists gravity to maintain posture2. Holds the body upright

a. Small, constant adjustments3. Prevents excess movement of the bones and joints

a. Preventing damage to joints (misalignment)b. Keeps joints stable

4. Located at openings of internal tractsa. Anus, mouthb. Controls movement of various substances for voluntary control

i. Swallowingii. Urination

iii. Defecation5. Protects internal organs

a. Abdominal and Pelvic organsb. Acts as external barrier to shield from traumac. Supports weight of organs

6. Contributes to homeostasisa. Generates heat when ATP is broken downb. Exercise causes body temp to risec. Extreme cold causes shivering

i. Random skeletal muscle movement to generate heat7. Richly supplied by blood vessels

a. Nourishment and oxygen deliveryb. Waste removal

8. Somatic Motor Neuron Innervationa. Each muscle supplied by an axon branch of a motor neuronb. Signals the muscle to contractc. Only way to contract is through the nervous system (unlike cardiac and smooth)

9. Contains various integrated tissuesa. Muscle fibers (cells)b. Blood vesselsc. Nerve fibersd. 3 layers of Dense Irregular Connective Tissues

3 layers of Dense Irregular Connective Tissues (-mysia)1. Epimysium

a. Outer most CT layer, surrounding the entire muscleb. Allows the muscle to contract powerfully while maintaining the structural integrityc. Separates the muscle from other tissues and organs

i. Allows the muscle to move Independent of the surrounding tissues2. Perimysium

a. Middle CT layer, surrounding individual fascicles (fiber bundles)b. Arrangement allows for the nervous system triggering of a specific movement of a subset of

fibers3. Endomysium

a. Inner most CT layer, covering individual muscle fibers (cells)b. Thin CT layer of collagen and reticular fibersc. Contains the extracellular fluid: Sarcoplasmd. Contains cellular nutrients supplied via the blood

Tendons and Muscles

1. Skeletal muscles work with tendons to pull on bones for movement2. Collagen fibers in all 3 CT layers (mysia) intertwined with collagen of a tendon3. Opposite end of tendon fuses with periosteum of the bone4. Tension from movement transferred through mysia to pull the bone

Aponeurosis

1. Broad tendon-like sheet that fuses with mysia 2. e.g. Lower back: latissimus dorsi fuses is an example of aponeurosis

Fascia

1. Connective tissue between the skin and bones

Skeletal Muscle Organization1. Tendon2. Fascicle3. Muscle Fiber (Cell)4. Myofibril5. Sarcomere6. Microfilament7. Actin and Myosin

CH 9.6 Skeletal Muscle Fibers (cells)

Skeletal Muscle Fibers (Muscle Cells)A skeletal muscle fiber is surrounded by a plasma membrane called the sarcolemma, which contains sarcoplasm, the cytoplasm of muscle cells. A muscle fiber is composed of many fibrils, which give the cell its striated appearance.

1. Long and cylindrical2. Large for human cells

a. Up to 100mcm in diameterb. Up to 30cm (11.8 in) in the Sartorius of upper leg

3. Terminologya. Sarco: FLESH

4. Sarcolemmaa. Plasma membrane of muscle fiber (cell)

5. Sarcoplasma. Cytoplasm of the muscle fiber (cell)

6. Sarcoplasmic Reticulum (SR)a. ER of the muscle fiberb. Stores, released and retrieves calcium ions

7. Sarcomerea. Functional unit of the muscle fiberb. Highly organized arrangement of contractile myofilaments

i. Actin (thin) filamentsii. Myosin (thick) filaments

Embryonic Development

1. Embryonic myoblast cells, each with single nucleus fuse with up to 100's of other myoblasts forming a multinucleated skeletal muscle fiber (cell)

2. Multiple nucleia. Contain multiple copies of genesb. Allows for large amounts of protein and enzyme production

i. Needed for muscle contraction

CH 9.7 The Sarcomere

The SarcomereThe region from one Z-line to the next Z-line, is the functional unit of a skeletal muscle fiber.

1. Functional unit of the muscle fiber (cell)2. Striated appearance due to arrangement of myofilaments

a. Actin (thin)b. Myosin (thick)

3. Myofilaments situated in sequential order from one end of the fiber to another4. Sarcomeres are bundled to make up a myofibril, running the length of the fiber 5. Myofibril (in-line sarcomere group) contraction is muscle contraction6. Each sarcomere is 2mcm in length7. Z-discs (or Z-lines)

a. End borders of sarcomere8. Actin filaments

a. Thin strandsb. Has a troponin-tropomyosin complexc. Anchored to end border Z-discsd. Project inward from ends

9. Myosin filamentsa. Thick strands with multiple headsb. Projects from the center of the sarcomere

CH 9.8 The Neuromuscular Junction

Neuromuscular Junction1. Site where a motor neuron's terminal end meets the muscle fiber (cell)2. Region where muscle fiber responds to nervous stimuli3. Every skeletal muscle is innervated by a motor neuron at the NMJ4. Excitation signal from neuron is only way to activate fiber to contract

CH 9.9 -11 Excitation-Contraction Coupling

Excitation-Contraction CouplingThe initiation of a muscle contraction by a neural stimulus (Excitation), to initiate an action potential (wave of electrical signal along the sarcolemma/membrane). This is Coupled to a muscle Contraction by the release of calcium ions from the Sarcoplasmic Reticulum, facilitating the contraction and release of actin and myosin proteins within the Sarcomere. The calcium ions interact with shielding proteins, troponin and tropomyosin, moving them aside to expose actin binding sites. With the binding sites available, the myosin heads can attach and pull the actin filaments in towards the center of the sarcomere, causing the muscle fiber to shorten.

1. Membrane Potentials/Electrical Gradientsa. Inside of cell is usually -60 to -90 relative to outside (multipolar motor -70)

i. Electrical differences created by ions2. Membrane potential used to generate electrical signals

a. Movement of ions across the membrane channel proteinsi. Channels open and close

b. Creates electrical current3. Forms the basis of neural signaling to muscle contraction

Action Potential

1. Special type of electrical signal that travels along a cell membrane2. Allows signal to be quickly transmitted over long distances

Acetylcholine (ACh)

1. Neurotransmitter or chemical messenger Resting Membrane Potential

1. Normal voltage between sides of the sarcolemma (membrane) Depolarize

1. Becomes less negativea. Muscle fiber has a RMP of -70mV and moves closer to zero

Graded Summation / All-or-none AP

1. Depolarization of +15mV to threshold of -55mV (from RMP of -70mV) Sarcolemma

1. Phospholipid bilayer of the muscle fiber (cell) T-Tubules

1. Periodic invaginations of the sarcolemmaa. Occasional entryways into the cell

Triad

1. Arrangement of T-tubule with SR on either sidea. Surrounds the myofibril

Sarcomere

1. Cylindrical structure of the myofibril2. Contains actin and myosin filaments

a. Sliding mechanism in 6:1 ratio Tropomyosin

1. Protein that winds around the chains of the actin filament2. Prevents binding of the myosin head

Troponin

1. Part of the troponin-tropomyosin complex2. Troponin has a binding site for Ca2+

a. Ca2+ causes movement of the complex, exposing the actin binding site for the myosin head to attach

Motor End-Plate and InnervationThe Generation of an Action Potential Across a Neuro Muscular Junction

1. The nerve receives a stimulus that generates an action potential to propagate along the axon.2. The AP reaches the axon terminal

a. Depolarization of the axon membrane opens Na+ and Ca2+ voltage gated channels.b. Ca2+ influx into the axon terminal from the surrounding extracellular fluid

3. Ca++ ions promote the fusion of synaptic vesicles containing acetylcholine (ACh) with the axon terminal membrane

4. Synaptic vesicles release the ACh into the synaptic cleft by exocytosis a. ACh diffuses across the synaptic cleft to bind to ACh receptors on the motor end plateb. Leftover ACh is degraded by the enzyme acetylcholinesterase (AChE)

i. Prevents unwanted extended muscle excitation5. Binding of Ach to Ach receptors on the sarcolemma opens chemically gated Na+ channels

a. Na+ ions diffuse rapidly into the cell causes a change in the membrane potential (voltage) to become less negative

b. Resting membrane potential (RMP)decreases= depolarization at motor end platec. Meanwhile, sodium potassium pumps (Na+ K+) restore ion concentration between

membrane sides back to RMP6. Propagation of the action potential

a. Waves spreads along the sarcolemma to adjacent areas opening more Na+ voltage gated channels

7. Repolarization occurs immediately after the depolarization wave passesa. Na+ channels close (preventing the increase of voltage inside the cell)b. K+ diffuses out of the cellc. Polarized state of the membrane is restored to RMP

8. Action potential continues down the T-tubules, deep into the musclea. This is the depolarization/repolarization wave

9. Action potential triggers release of Ca2+ ions from the terminal cisternae into the sarcoplasm

The Sliding Filament MechanismContinuation of the Action Potential from the Nero Muscular Junction

10. Newly available Ca2+ ions from the SR, binds to troponina. Troponin is attached to tropomyosin and blocks the attachment site for myosin filament

heads to attach. This is known as the troponin-tropomyosin complexb. The troponin changes shape and moves the tropomyosin, exposing the actin binding site

11. Activated myosin heads attach to actin binding sitesa. This is in preparation for the power stroke

12. Myosin heads pivot = Power Strokea. High energy to low energy release

i. ADP and Pi (inorganic phosphate) are releasedb. Actin filament is pulled toward the center of the sarcomere at the M Line

13. New ATP molecule binds to myosin heada. Causes detachment from actin

14. Myosin head prepares for next strokea. ATP hydrolysis into ADP + Pi

b. High-energy state or "cocked" position

End of Muscle Contraction1. Stops when signaling from motor neuron ends

a. Sarcolemma and T-Tubules repolarize (decrease in voltage to RMP)b. Voltage gated Ca2+ channels in the Sarcoplasmic Reticulum close

i. Ca2+ ions pumped back into the SRc. Lack of Ca2+ causes re-shielding of the actin binding sites

i. Shielded by the troponin-tropomyosin complex2. Stops upon ATP depletion

a. Muscles fatigue3. Stops upon death

a. Lack of ATP prevents myosin head releasei. Rigor mortis: permanent muscle contraction

CH 9.11 Sources of ATP

Sources of ATP1. ATP is the energy source for muscle contraction2. Directly involved in the cross-bridge cycle of the sliding filament mechanism3. ATP provides energy to power the active transport Ca2+ pumps in the SR4. ATP storage in muscle is low

a. Only a few seconds worth of contractions Mechanisms for ATP regeneration

1. Creatine Phosphatea. Molecule with energy storage in phosphate bondsb. Resting muscles stores excess ATP by transfer to creatine

i. Produces ADP and creatine phosphatec. Acts as energy reserve to quickly create ATPd. When ATP is needed

i. Creatine phosphate transfers phosphate back to ADP to form ATPii. Reaction catalyze by enzyme creatine kinase

e. Quick reaction time powers first few seconds of muscle contraction: up to 15 seconds worth of energy

2. Glycolysisa. Anaerobic process: non-oxygen dependentb. Initiated when ATP is depleted from creatine phosphate

i. Glycolysis results in a slower rate of ATP availability than CPc. Breaks down glucose as energy source

i. Glucose provided by bloodii. Can metabolize glycogen stores in muscle?

d. One glucose molecule yields:i. Two ATP molecules

ii. Two pyruvic acid molecules1. Can be used in aerobic respiration if oxygen is available2. If no oxygen is available, then converts to lactic acid

a. Lactic acid contributes to muscle fatigue3. Conversion of pyruvic acid to lactic acid allows recycling of NAD+ enzyme from

NADHa. Necessary for glycolysis to continueb. Occurs during strenuous/high energy exercise with low oxygen delivery to

musclese. Glycolysis can only sustain approximately 1 minute of muscle activityf. Useful in short bursts of high-intensity output

3. Aerobic Respiration

a. Breakdown of glucose in the presence of sustained supply of oxygeni. Muscles store O2 in myoglobin proteins as compensation mechanism

b. Produces ATP, CO2 and waterc. Approximately 95% of the ATP required for resting or moderate activity takes place in the

mitochondriad. Inputs for aerobic respiration

i. Glucose from the blood streamii. Pyruvic acid from glycolysis

iii. Fatty acidse. One glucose molecule yields:

i. 36 ATPf. Aerobic training increases efficiency of the circulatory system in order to deliver more O2

quickly

Muscle FatigueOccurs when muscle can no longer contract from neural signaling

1. Depleted ATP reserves decrease muscle function2. Lactic acid buildup

a. Lowers intracellular pHi. Affects enzyme and protein activity

3. Excessive membrane depolarizationa. Causes Na+ and K+ imbalances

i. Results in disruption of Ca2+ flow from4. Long periods of sustained exercise

a. May damage SR and sarcolemmai. Impairs Ca2+ regulation

Oxygen DebtAmount of oxygen needed to compensate for ATP production without oxygen during muscle contraction: Glycolysis and Creatine Phosphate mechanisms

1. Oxygen is required to restore ATP and creatine phosphate levels2. Oxygen converts lactic acid to pyruvic acid3. Oxygen converts lactic acid into glucose or glycogen in the liver

These combined processes result in an increased breathing rate that remains elevated during and after exercise until the oxygen debt has been met.

CH 9.12 Relaxation

Relaxation of a Skeletal Muscle1. Relaxation begins with the motor neuron

a. Stopes the release of ACh into the synapse at the NMJ2. Repolarization of the muscle fiber occurs

a. Muscle fiber again becomes more negativei. Muscle goes back to its RMP of about -70mV

b. Ca2+ gates in the SR close3. Active (ATP driven) pumps moves Ca2+ out of the sarcoplasm back into the SR4. Re-shielding of the actin binding sites occurs with the lack of available Ca2+

a. Troponin-Tropomyosin complex blocks these sites5. Lack of ability to form cross-bridges between actin and myosin causes lack of tension and

subsequently relaxation

Muscle Strength1. Number of muscle fibers in a muscle is determined by genetics2. Muscle strength is directly related to amount of myofibrils and sarcomeres within each fiber (cell)3. Hypertrophy: Increased mass in skeletal muscle

a. Increased production of sarcomeres and myofibrilsb. Caused by

i. Hormonesii. Stress

iii. Artificial anabolic steroids4. Atrophy: Decreased mass in skeletal muscle (muscle fibers numbers remain intact)

a. Decreased sarcomeres and myofibrilsb. Caused by

i. Decreased use Muscle Contraction Concept Review

1. Sarcomere is the smallest contractile portion of the muscle2. Myofibrils are complex of thick and think (myosin and actin) filaments3. Troponin and tropomyosin are regulating proteins that block actin binding sites4. Sliding filament mechanism is directly responsible for contraction5. Ach is a neurotransmitter that binds to receptors at the NMJ to initiate depolarization (becomes

less negative), starting the Action Potential6. The action potential released Ca2+ from the SR7. Ca2+ causes the un-shielding of the acting binding sites to facilitate cross-bridging of the myosin

and actin fibers8. The Power Stroke occurs once the myosin heads attach to the actin fiber binding sites, followed by

a ratcheting movement powered by ATP9. Sarcomeres, Myofibrils and Muscle Fiber shortening, define a contraction to produce movement

CH 9.12 Nervous Control of Muscle Tension

Nervous System Control of Muscle Tension1. Muscle Tension

a. The force generated by the contraction of the musclei. Shortening of the sarcomere

2. Isotonic and Isometric Contractionsa. Contractions against a load that does not moveb. Most actions of the body are a combination of Isotonic and Isometric Contractions

Isotonic Contractions

1. Constant muscle tension throughout the contraction2. Two types of isotonic contractions

a. Concentric Contractioni. Muscle shortens to move the load (lifting up)

ii. e.g. Biceps brachii muscle contracting in a curl lift1. Angle of the elbow joint decreases as forearm is moved closer to the body

b. Eccentric Contractioni. Muscle lengthens and tension diminishes (lifting down)

ii. e.g. Biceps brachii muscle lengthens1. Angle of the elbow joint increases as forearm is extended2. e.g. Weight is slowly lowered

Isometric Contractions1. Muscle produces tension without changing the angle of a skeletal joint2. Involves sarcomere shortening and increased tension3. Does not move a load4. Active in maintaining posture and bone and joint stability

a. Holding the head upright under normal conditions

CH 9.13 Motor Units & Length Tension

Motor Units: GROUP of muscle fibers in a muscle innervated by a single motor neuronMotor neuron axons will BRANCH to form synaptic connections at their individual NMJ's

1. Muscle contraction depends on innervation by the axon terminal of a motor neuron2. Each muscle fiber (cell) is innervated by one motor neuron3. Size of a motor unit depends on the nature of the muscle

a. Small motor unitsi. Single motor neuron supplies a SMALL number of muscle fibers

ii. Permits fine motor control1. e.g: extraocular eye muscle (eyeball movement)

iii. Each muscle has thousands of muscle fibers1. Single motor neuron supplies about every six muscle fibers by individual

branches stemming from a single axonb. Large motor units

i. Single motor neuron supplies a LARGE number of muscle fibersii. Axon splits into thousands of branches

iii. Concerned with simple or gross movementsiv. e.g: Back or thigh muscles

Motor Units Wide Range of Control Over the Muscle

1. Combinations of small and large motor units gives a wide range of control2. Recruitment: Increasing activation of motor units3. Small motor units

a. More excitable firing because of a lower thresholdb. Fires first to the smaller fibersc. Results in a small degree of strength/tension

4. Large motor unitsa. Fires when more strength is neededb. Bigger muscles with a higher threshold

5. Recruitmenta. Nervous system uses recruitment as an efficiency mechanismb. Increasing activation of motor unites produces an increase in powerc. Contraction grows stronger with increased recruitmentd. Some large motor units will produce 50x more power than small

i. Allows for soft and strong function from the same musclee. Maximum Muscle Force

i. Max amount of motor units recruited simultaneously for max forceii. Short timespan due to energy requirements

iii. Generally, not all motor units fire at once1. Prevents completes complete fatigue

Length-Tension Range of a SarcomereSarcomere length directly effects the force generated upon shortening

1. Cross-bridges (myosin head/actin fibers connection) can only occurs where there are actin/myosin overlap within the sarcomere

2. Ideal sarcomere length to produce max tension is at 80%-120% of its resting length3. 100% of Length is when the medal edges of the myosin and actin fibers are even

a. This length maximizes overlap of actin-binging sites with myosin heads4. Beyond 120% filaments do not overlap sufficiently 5. Under 80% has a reduced overlap range

a. H Zone is reduced in length

CH 9.13 Motor Neuron Frequency

Muscle TwitchAn isolated, muscle contraction from a single action potential from a motor neuron

1. A twitch can last from a few to 100 milliseconds depending on muscle2. Tension produced can be measured by a myogram

a. Instrument that measures tension over time.3. Each Twitch undergoes 3 phases

a. Latent Periodi. Action Potential propagates along sarcolemma

ii. Ca2+ ions released from SRiii. Excitation and contraction coupling

1. No contraction yetb. Contraction Phase

i. Ca2+ ions in the sarcoplasm have bound to troponinii. Tropomyosin has shifted exposing actin binding sites

iii. Sarcomeres are shortening to max tensionc. Relaxation Phase

i. Tension is decreasing as contraction stopsii. Ca2+ ions are pumped back in the SR

iii. Cross-Bridge cycling stopsiv. Muscle fibers return to resting state

Graded Muscle ResponseAllows for a variation in muscle tension

1. Twitch does not produce significant muscle activity2. Graded Muscle Response

a. A Series of sustained action potentials to the muscle fibersb. Necessary to produce workc. Can be modified by the nervous system, producing various amounts of forced. Frequency of AP and number of transmitting motor neurons affect the tension produced in

skeletal muscle Wave SummationOverlapping muscle fiber stimulation produces a stronger contraction

1. Fibers are stimulated as a previous twitch is occurring2. The second twitch is the stronger of the two

a. Motor signaling is SUMMEDb. Additional Ca2+ ions becomes available to the sarcomeres

3. Summation results in greater contraction of the motor unit.

TetanusThe fusion of contractions, producing a single contraction

1. Increased frequency of motor unit signaling continues until it peaks2. Incomplete tetanus

a. This tension is 3-4 times greater than a single twitchb. Muscle has quick cycles of contraction/relaxation

3. Complete tetanusa. Results what stimulus frequency is high enough that relaxation disappears completely

b. Contraction becomes continuousc. Increased Ca2+ contractions allows all sarcomeres to form cross bridges and shortend. Continues until muscle fatigues

Treppe (aka: Staircase effect)

1. Muscle has been dormant for extended amount of time is activated2. Initial contractions are half the force of subsequent contractions3. Increased in a graded matter resembling stairs4. Increased concentration of Ca2+ with steady stream of APs5. Maintained with adequate ATP

CH 9.14 Muscle Tone & Fiber Types

Muscle ToneThe maintenance of contractile proteins produce tension to stabilize joints and maintain posture

1. Skeletal muscles are rarely relaxed2. Small contractions maintain contractile proteins: muscle tone3. Accomplished by interaction between the nervous system and skeletal muscles

a. Activation of few motor units at a time in a cyclical manner preventing fatiguei. Some recover, while others are active

Hypotonia or Atrophy

1. Can result from CNS damagea. Cerebellum damageb. Loss of innervation to a skeletal muscle

i. e.g. Poliomyelitis c. Muscles display flaccid appearanced. Functional impairments like weak reflexes

Hypertonia (excessive muscle tone)

1. Accompanied by hyper-reflexiaa. Excessive reflex response

2. Often results of damage to upper motor neurons in the CNS3. Muscle rigidity

a. e.g: Parkinson's disease4. Spasticity

a. Phasic change in muscle toneb. Limb snaps back from passive stretching

i. Seen in some strokes

CH 9.14 Skeletal Muscle Fiber Types

Classifying Muscle Fiber Types1. Speed of contraction

a. Dependent on how quickly myosin's ATPase hydrolyzes ATP to produce the cross-bridge actioni. ATP causes detachment of myosin head to actin after the power stroke

2. How ATP is produced / Primary metabolic pathwaya. Aerobic Respiration - Oxidative

i. Glucose and Oxygenii. More ATP produced in each cycle

1. More mitochondria than glycolytic fibersa. ATP produced here with oxygen

iii. More resistant to fatigueb. Anaerobic Respiration - Glycolytic

i. Glycolysisii. Less ATP produced in each cycle

iii. Fatigue at a quicker rate Three Types of Skeletal Muscle FibersMost skeletal muscle contains all three types in varying proportions.(Shown in order of least to most fatiguing and slow to fastest fibers)

1. Slow Oxidative (SO) Fibera. Aerobic Respiration to produce ATP

i. Glucose and Oxygenb. Slow Contractionsc. Fatigues least of all fibers

2. Fast Oxidative (FO) Fibersa. Aerobic Respiration to produce ATP (primary source)

i. Glucose and Oxygenb. May switch to Anaerobic Respiration for ATP

i. Glycolysisc. Fast Contractionsd. Fatigues faster than SO fibers

3. Fast Glycolytic (FG) Fibersa. Anaerobic Respiration (primary source) of ATP b. Fastest contractions (fast or fastest?)c. Fatigues faster than SO and FO

Slow Oxidative (SO)Fibers

1. Useful in:a. Maintaining postureb. Producing isometric contractionsc. Stabilizing bones and joints

2. Sustained muscle activity over long periods of time3. Fibers have a small diameter

4. Does not produce large amount of tension5. Capable of contracting for long periods (less fatigue) due to large ATP amount6. Oxidative (SO) fibers have more mitochondria than in glycolytic fibers

a. Produces the most ATP per cycle7. Extensively supplied with blood capillaries for oxygen requirement8. SO fibers store Myoglobin

a. Oxygen carrying molecule b. Give SO fibers a Red Color

Fast Oxidative (FO) Fibers

1. Useful in:a. Walkingb. Functions more than posture, but less than sprinting

i. More tension than SO fibersii. More fatigue resistant than FG fibers

2. Also called Intermediate Fibersa. Characteristics between slow and fast fibers

3. Produce ATP more quickly than SO fibers4. Primarily Aerobic, but also used Anaerobic metabolic pathways5. Producing high amounts of tension6. Does not have significant amount of Myoglobin

a. Gives FO fibers a lighter color than SO fibers Fast Glycolytic (FG)Fibers

1. Useful in sprinting and quick, and short movementsa. Rapid forceful contractionsb. Fatigues quickly

2. Primarily use Anaerobic Respiration (Glycolysis) as ATP source3. Large diameter fibers4. High levels of tension5. High amounts of glycogen

a. Used in glycolysis to quickly produce ATP6. Insignificant amounts of mitochondria and myoglobin

a. Gives FG fibers a lighter color than FO fibers

Slow Oxidative Fast Oxidative Fast Glycolytic

Metabolic Pathway Aerobic Aerobic/Anaerobic Anaerobic

Contraction Speed Slow. Fast. Fastest.

Strength/Tension Low. Med. High.

Endurance High. Med. Low.

Fiber Size Small. Med. Large.

Myoglobin/Color Red Pink White

CH 9.14 Smooth Muscle

Smooth Muscle1. Named due to lack of striations2. Spindle shaped (thin-wide-thin)3. Single nucleus4. Produce endomysium CT5. 30 to 200 mcm (1000's times shorter than skeletal fibers (cells)6. Stimulated by:

a. Pacesetter cells by the autonomic NSb. Hormonesc. Spontaneouslyd. Stretching

7. Some smooth muscle cells have latch-bridgesa. Slow-cycle cross-bridgesb. No need for ATP

8. Present in:a. Walls of hollow organs

i. Urinary bladderii. Uterus

iii. Stomachiv. Intestines

b. Walls of passagewaysi. Arteries

ii. Veins of the circulatory systemc. Tracts of:

i. Respiratory systemii. Urinary system

iii. Reproductive systemd. Eyes

i. Changes size of irisii. Alters shape of the lens

e. Skini. Erects hair for fear / temperature

Smooth Muscle Cell Makeup

1. Actin and Myosin filaments are present, not in striated patternsa. Thin and thick contractile proteins present in random order

2. Dense bodies anchor thin actin filaments at endsa. Analogous to Z-Discs of a sarcomere in skeletal and cardiac muscle

3. Calveoli: SR membrane indentationsa. Calcium ions supplied by SR from extracellular fluid through calveoli

4. Calmodulina. Regulatory protein controls the cross-bridge formationb. Troponin is absent in smooth muscle

Smooth Muscle Fiber Contractions

1. Ca2+ ions pass through calcium channels in the sarcolemmaa. Additional Ca2+ released from SR

2. Ca2+ binds to Calmodulin3. Calcium-Calmodulin Complex

a. Activates Myosin Kinase4. Myosin (light chain) Kinase

a. Activates Myosin headsi. Converts ATP to ADP and Pi

ii. Pi attaches to the myosin head5. Myosin head attached to actin binding sites and pulls actin filaments6. Actin filaments (attached to dense bodies), are pulled center

a. Dense bodies are tethered to the sarcolemma7. Entire muscle fiber is contracted by ends pulled center

a. Midsection bulges center in corkscrew motion Single Unit Smooth Muscle

1. Contains Gap Junctionsa. Synchronizes membrane depolarizationb. Muscle contracts as a single unit

2. Permits muscle to stretch, contract and relax as the organ expands3. Found in:

a. Walls of the viscera (visceral muscle). Organs Multiunit Smooth Muscle

1. Cells DO NOT have Gap Junctions2. Contracting does not spread between cells

CH 9.15 Interactions of Skeletal Muscles

Interactions of Skeletal Muscles1. Skeleton movement is created by the contraction of muscle fibers (cells)2. Skeletal muscles have an origin and an insertion3. Tension is transferred from muscle to tendons to move bone

a. Tendons are strong bands of dense regular CTb. Attaches muscle to bone

4. Most skeletal muscles must be attached to a fixed part of the skeleton5. Facial muscles (produce facial expressions) do not attached to bone

a. Insertions and Origins are in the skinb. Muscles contract to:

i. Smile or frownii. Form sounds and words

iii. Raise the eyebrows6. Other skeletal muscles that do not move the skeleton

a. Tongueb. External urinary sphincterc. External anal sphincterd. Diaphragm

i. Contracts and relaxes to change the volume of airii. Does not move the skeleton

Key Terms for Skeletal Muscle Movement

1. Insertiona. Moveable end of muscle, attached to the bone being pulled

2. Origina. End of muscle that is fixed / stabilized to a bone

3. Prime Mover / Agonista. Principal muscle used in movement

i. Multiple muscles can be involved in a movement action4. Synergist

a. Assists the Agonist5. Fixator

a. A synergist that makes the insertion site more stableb. Stabilizes a bone that is the attachment point for the prime mover

Antagonista. Muscle with the opposite action of the prime moverb. e.g.: extending the knee

i. Quadriceps are activated = Agonist1. Pulls lower leg straight at the knee

ii. Hamstrings are activated = Antagonist1. Releases tension keeping the leg bent

c. Antagonist play two rolesi. Maintains body or limb position

1. Holding the arm out

2. Standing erectii. Control rapid movement

1. Shadowboxing without landing a punch2. Ability to check the motion of a limb

Muscle Compartmental OrganizationSkeletal muscle is enclosed by CT at three levels:

1. Endomysiuma. Covers each muscle fiber (cell)

2. Perimysiuma. Covers each fascicle (bundled group of muscle fibers)b. Fascicle

i. Bundled group of muscle fibersii. Fascicle arrangement is correlated to the force generated by the muscle

iii. Affects the range of motion of the muscle3. Epimysium

a. Covers the entire muscle

Classifications of Common Fascicle ArrangementsEach arrangement has its own range of motion and ability to do work

1. Parallela. Fascicles arranged in the same direction of the muscle of the long axisb. Majority of skeletal muscles are arranged in this fashionc. e.g. Sartorius

i. Fusiform / belly1. Central Body

a. Plump with a large mass in the middle between insertion and originb. Ends are tapered

2. Circular (sphincters)a. Concentrically arranged bundlesb. When relaxed, opening size is increased c. When contracted, opening shrinks to closure

i. e.g. Orbicularis oris (mouth)1. Contracts: oral opening is smaller (pucker, whistle)

ii. e.g. Orbicularis oculi (eye)1. Surrounds each eye

3. Convergenta. Widespread, expanded muscle, at a smaller common attachmentb. Attachment points: tendon, aponeurosis (flat, broad tendon), or a raphe (slender tendon)

i. e.g. Pectoralis major (large chest muscle)1. Converges on the greater tubercle of humerus via tendon

ii. e.g. Temporalis of the cranium4. Pennate (feathers)

a. Fascicles blend into a central tendon that runs the length of the muscleb. Muscle fibers can only pull at an angle, only allowing a small movementc. Holds more muscle fibers, producing more tension for its sized. 3 Sub types:

i. Unipennate1. Fascicles located on one side of central tendon

a. e.g. Extensor digitorum (forearm)ii. Bipennate

1. Fascicles on both sides of central tendoniii. Multipennate

1. Muscle fibers wrap around the tendon, forming individual fascicles2. Allows for movement in multiple directions

a. e.g. Deltoidi. Fibers cover the shoulder, but have a single tendon insertion on the

deltoid tuberosity of the humerusii. Deltoid abducts

iii. Deltoid abducts and flexes when anterior fascicles are stimulated: abducts and flexes (arm raises and moves anteriorly)

5. Triangular

Lever System of Muscle and Bone Interactions

1. Muscles are arranged in pairs based on functions2. Muscle to bone connection depends on:

a. Forceb. Speedc. Range of motion

CH 9.16 Naming Skeletal Muscles

Naming Skeletal Muscles1. Named based on

a. Location and sizei. e.g. Gluteus maximus and gluteus minimus

b. Bone association and location in the bodyi. e.g. Tibialis anterior

c. Fascicle directioni. e.g. Abdominal muscles

1. Rectus (straight) abdominis2. Oblique (angle) abdominis3. Transverse (across) abdominis

d. Origin/how many originsi. Biceps brachii

1. Bi: muscle has two originsii. Triceps brachii

1. Tri: muscle has three originse. Insertion

i. Pectoralis majorf. Shape

i. Orbicularisg. Length

i. Brevis: shortii. Longus: long

h. Position relative to the midlinei. Lateralis: outside of midline

ii. Medialis: toward the midlinei. Location of a muscles attachments

i. Origin is always named first, then insertion1. Sternocleidomastoid

a. Dual Origin: Sternum and Clavicleb. Insertion: Mastoid process of the temporal bone

j. Movementi. Flexor

1. Decreases angle at joint (flexes)ii. Extensor

1. Increases angle at joint (extends)iii. Abductor

1. Moves bone away from the bodyiv. Adductor

1. Moves bone toward the midlinek. Groups, Number of muscles

i. Quadriceps1. Group of 4 muscles in the anterior thigh

Mnemonic Device for Latin Roots

Example Latin or Greek Translation

Mnemonic Device

ad to; toward ADvance toward your goalab away from n/asub under SUBmarines move under water.

ductor something that moves

A conDUCTOR makes a train move.

anti against If you are antisocial, you are against engaging in social activities.

epi on top of n/aapo to the side of n/a

longissimus longest “Longissimus” is longer than the word “long”

longus long Longbrevis short Brief

maximus large Maxmedius medium “Medius” and “medium” both begin

with “med”minimus tiny; little Minirectus straight To RECTify a situation is to straighten it

outmulti many If something is MULTI-colored, it has

many colorsuni one A UNIcorn has one hornbi/di two If a ring is DIcast, it is made of two

metalstri three TRIple the amount of money is three

times as muchquad four QUADruplets are four children born at

one birthexternus outside Externalinternus inside Internal