have the ability to respond to a stimulus

• movement of the body
• maintain posture
• store substances
• move substances
• heat production

Location, function, appearance, and control of 

SKELETAL MUSCLE

1. Skeleton
2. Movement, heat, posture
3. Striated, mulei-nucleated (eccentric), fibers parallel 
4. voluntary

Location, function, appearance, and control of 

CARDIAC MUSCLE

1. Heart
2. Pump blood contiuously
3. Striated, one central mucleus
4. incoluntary

Location, function, appearance, and control of 

Visceral (smooth muscle)

1. G.I. tract, uterus,eye, blood vessels
2. Peristalsis, blood pressure, pupil size, erects hairs
3. No Striations, one central nucleus
4. involuntary

Organization of Muscle Tissue

(smallest to biggest)

a thick fascia that connects two muscle bellies

ex. frontal belly of the occipitolfrontalis muscle

• sarcolemma
• sarcoplasm
• myofibril
• t-tubles
• sarcoplasmis reticulum
• trian (w/ terminal cisterns)
• sarcomere

Thick filaments 

(myosin)

Thin filaments 

(actin)

Parts of sarcomere:

• A band
• I band
• Z disc
• H zone
• M line
• Zone of overlap

generate force during contraction

• myosin
• actin

help switch the contration process on and off 

• tropomyosin
• troponin

keep the thick and thin filaments in proper alignment and link the myofibrils to the sarcolemma and extracellular matrix

• titin
• alpha actinin
• myomesin
• nebulin
• Dystrophin

1. Myosin heads hydrolyze ATP and become reoriented (ADP) and energized
2. Mysoin heads bind to actin, forming crossbridges
3. Myosin crossbridges rotate toward center of the sarcomere (power stroke) using ADP
4. As myosin heads bind ATP, the crossbridges detach from actin

a synapse or site of communication between a neuron and muscle is usually named a neuromuscular junction (NMJ)

• Neuromuscular junction= axon terminal (synaptic end bulb) + motor end plate (sarcolemma under motor neuron)

Presynaptic membrane

&

Postsynaptic membrane

Presynaptic- on the neuron

Postsynaptic- and the end

• they are seperated by a space called the snaptic cleft

1. ACH is released from synaptic vesicle
2. ACh binds to ACh receptor
3. Muscle action potential is produced
4. ACh is broken down

• Curare- binds to and blocks ACh receptors (competes w/ but doesnt stimulate the ACh receptors
• Myasthenia gravis- antibodies bing and block ACh receptors, making there be no stimulus causing paralysis
• Botulism- inhibits ACh release (botox, relaxes muscles)
• tetanus- produces a toxin that blocks an inhibitory neurotransmitter (police locked up)
• Organophosphates- inhibits acetylcholinesterase (muscle spasms)

• thought process through the brain
• AP arrives at the neuromuscular junction
• regeneration of an AP on the muscle membrane
• release of Ca2+ from the sarcoplasmic reticulum
• sliding of thick on thin filaments in sarcomeres
• generation of muscle tension

Excitation-Contraction Coupling

At rest

• calcium in SR (terminal cisternae
• troponin-tropomyosin prevents myosin from binding to site on actin
• concentration of ATP in high in relaxed muscle

Excitation-Contraction Coupling

Action Potential (AP)

ACh binds to its receptor on the motor end plate

• AP will travel along the sarclemma down into T tubules
• production of AP in muscle leads to contraction

• the action potential running through the T tubules causes the sarcoplasmic reticulum's terminal cisterae to release calcium into the sarcoplasm
• the calcium will then bind to troponin
• tropomyosin changes shape so myosin binding sites on actin are uncovered
• Myosin then can bind to actin
• the calcium will also activate ATPase ability of myosin
• the ATPase activity of myosin activates its power stroke movement (pulls actin inward (H zones and I bands narrow and may disappear; A band does not change its length). At the end of power stroke, a new ATP binds to ATP binding site on the myosin cross bridge, resulting in detachment of myosin from actin. Attach, pull, detach=steps in contraction. if lack ATP- rigor mortis.)
• A relax following contraction (ACh is inactivted by acetycholinesterase (from sarcolemma surface) calcium is actively transported back into SR (ATP attaches to myosin cross bridge and it releases from actin). Troponin-tropomyosin comvers myosin cross bridges.)

ATP is required for

• power stroke- movement of myosin cross bridges pull actin inward in a sarcomere
• at end of power stroke, ATP binds to ATP binding site, resulting in detachment of myosin from actin (ATP needed to release cross bridges)
• pumping Ca2+ back into terminal cisternae of the SR

******know the steps********

Sources of Muscle Energy

Stored ATP- 3 secs

3 types of production

• Creatine phosphate ATP- 12 secs (combined with ATP-15 secs)
• Aerobis ATP production- oxygen
• Anaerobic ATP production- Glucose, 30-40 secs

• even as ATP and CP are being used, ATP is generated by aerobic respiration and anaerobic respiration
• in active contractin muscles, glucose is primary fuel supply
• anaerobic pathway: glucose-> lactic acid+2 ATP
• resting and slowly contractin muscles obtain bulk of ATP via aerobic respiration of fatty acids
• Aerobic pathway: glucose+O2->CO2+H2O+36ATP
• Aerobic produces 20X more ATP but take 2.5 times longer

Sources of Muscle Energy:

ATP from anaerobic glycolysis

muscle glycogne

to

From blood->Glucose               

to

                           2 Pyruvic acid && 2 ATP (Glycolysis)

to

              2 Lactic acid -> into blood

duration of energy provided is 30-40 sec

Sources of Muscle Energy:

ATP from creatine phoschate

ATP\/      Creatine       \/ATP\

                                  (Energy

                                   of muscle

                                     contraction)

ADP/\Reatin Phosphate/\ADP/

  relaxed             contracting

muscle                 muscle

Duration of energy provided is 15 secs

Sources of Muscle Energy:

ATP from aerobic cellular respiration

• Fatty acids liberated from adipose cels
• Amino acids from protein breakdown
• Pryuvic acid from glycolysis
• Oxygen from hemoglobin in blood or from myoglobin in muscle fibers

TO

Cellular respiration in mitochondria

Oxygen Debt or labored breathing is the amount of O2 repayment required after exercise in skeletal muscle to:

• replenish ATP stores
• replenish creatine phosphate and myoglobin stores
• convert lactic acid back into glycogen

Ina state of homeostasis- muscle uses O2 & nutrients to be balanced by the production of manageable levels of waste like: CO2, Heat, & Lactic Acid

• cardiac muscle contracts 10-15 times longer than skeletal muscle
• cardiac uses a lot of O2 whcih is generated by ATP through aerobic respiration

• deep inside organs, involuntary (digestion)
• has low capacity for generating ATP and does it through anaerobic respiration (glycolysis)

All or none principle of muscle contraction

• when an individual muscle fiber is stimulated and action potential is prolongated along its sarcolemma
• all muscle fibers must contract at the same time
• does not apply to the entire muscle, only to motor units

Motor neuron plus all the muscle cells it innervates

• High precision= fewer muscle fibers per neuon & Laryngeal and extraocular muscles
• Low precision= many muscle fibers per neuron & Thigh muscle

Skeletal Muscle Fiber Types:

Appearance

(red muscle fibers)

Red muscle fibers (dark meat)- have a high myoglobin content, more mitochondria, more energy stores, and a greater blood supply

Skeletal Muscle Fiber Types:

Appearance

(white muscle fibers)

Skeletal Muscle Fiber Types:

Slow oxidative

• Slow oxidative (SO) fibers- appear dark red (same reason), least powerful, fatigue resistant.
• used for endurance distance runners: slow contraction, aerobic respiration, more capillaries, small diameter

Skeletal Muscle Fiber Types:

Fast oxidative-glycolytic

• Fast oxidative-glycolytic (FOG) fibers are intermediate size, dark red (more myoglobin and capillaries), moderately to fatigue.
• used for walking: fast contraction, anaerobic and aerobic respiration, more mitochondria, high glycogen

Skeletal Muscle Fiber Types:

Fast glycolytic

Large, white (low myoglobin content and fewer capillaries) & powerful

• intese anaerobic activity of short duration
• rapid contraction
• anaerobic respitaion/glucose
• high glycoge
• large diameter

Mot skeletal muscle is mixed, aout 1/2 is slow oxidative

• within a unit all the fibers are the same

Endurance activities trasform fast twitch (produce more mitochondria and increase myoglobin

Latent period- AP sweeps over the sarcolemma and Ca2+ ions are released from the sarcoplasmic reticulum

contracting- during next phasethe fiber is active

relaxation- the Ca2+ ions are reseqestered into the SR and myosin inding sites are covered by tropomyosin

Refractory period- temprart loss of excitability

twitch- a stimulus that results in contraction of a sigle muscle fiber is measured over a very brief millisecond time frame

wave summation- stimuli arriving a t different times cause larger contractions

recruitment- allows a muscle to accomplish increasing gradations of contractile strength

Istonic Contractions= movement

• Concentric isotonic- muscle is contracted and shortened
• Eccentric isotonic- muscle is contracted and long

Isometric contraction=no movements

• muscle force and resistance are equal
• supporting objects in a fixed position and posture

Imbalances of Homeostasis:

exercis-induced muscle damage

• After intense exercise electrom micrographs reveal muscle damage including torn sarcolemmas and dirupted Z-discs
• blood levels of proteins normally confined only oto muscle (myoglobin & creatine kinase) increase as they are released from damaged muscle

Imbalances of Homeostasis:

Spasm and Cramp

Spasm- sudden involuntary contraction of a single mucsle (usually painless)

Cramp- involuntary and painful muscle contraction. cause by inadequate blood flow to muscle, overuse, abnormal blood electrolyte levels

Imbalances of Homeostasis:

Disease States and Disorders

Fibrosis (myofibrosis)- replacment of muscle fibers by excessive amounts of C.T. (fibrous)

Myosclerosis- hardening of muscle becuase of calcification

**both occur b/c of trauma and various metabolic disorders

Imbalances of Homeostasis:

Aging

• decrease in physical activity, you undergo a slow, progressive loss of skeletonal muscle mass that is replaced largely by fibrous C.T. tissue and adipose tissue
• muscle strength at 85 is about half compared to 25
• of the 3 fiber types the slow oxidative fibers appears to increase.