Chapter 11: Muscular Tissue

Properties of Cardiac Muscle

(1) It must contract with a regular rhythm; (2) it must function in sleep and wakefulness, without fail or need of conscious attention; (3) it must be highly resistant to fatigue; (4) the cardiomyocytes of a given heart chamber must contract in unison so that the chamber can effectively expel blood; (5) each contraction must last long enough to expel blood from the chamber.

A Bands

(dArk) Results from thick filaments lying side by side -Especially dark when thick and thin filaments OVERLAP

Process of Contraction/Sliding Filament Theory

10) Myosin head must have ATP molecule bound to it to initiate contraction. Myosin ATPase, an enzyme in the head, HYDROLYZES THIS ATP into ADP and Phosphate. This energy release "COCKS" the head into an extended, HIGH-ENEGY position -Head keeps ADP and Phoshate bound to it 11) COCKED myosin binds to an exposed ACTIVE SITE on the THIN FILAMENT, forming a CROSS-BRIDGE between the MYOSIN and ACTIN 12) Myosin releases the ADP and Phosphate and flexes into a BENT, LOW-ENERGY position, tugging the thin filament along with it (POWER STROKE) 13) Binding of a new ATP to myosin DESTABILIZES myosin-actin bond, BREAKING the CROSS-BRIDGE. -Myosin undergoes a RECOVERY STROKE; hydrolyzes new ATP, recocks, and attaches to a new active site farther down the thin filament, ready for another power stroke

PROCESS OF RELAXATION

14) Axon terminal stops releasing ACh 15) As the ACh separates from its receptor, AChE breaks it down into fragments that cannot stimulate the muscle -Axon terminal reabsorbs these fragments for recycling 16) Reabsorption of Calcium Ions by Sarcoplasmic Reticulum -Through ACTIVE TRANSPORT (ATP needed) 17) Loss of calcium ions from troponin 18) Tropomyosin moves back into position where it blocks the active sites of the actin filament. BOTH RELAXATION AND CONTRACTION REQUIRE ATP!!!

Aerobic Respiration is typically used when exercising longer than how many seconds?

40

Excitation-Contraction Coupling Process?

5) Action potentials propagated down T tubules and INTO the cell 6) Action potentials open VOLTAGE-GATED ion channels in the T Tubules AND saroplasmic reticulum; -CALCIUM DIFFUSES out of the SR, down its concentration gradient, and INTO the CYTOSOL! 7) Calcium binds to the troponin of the thin filaments 8)Troponin-tropomyosin complex changes shape and EXPOSES the ACTIVE SITES on the ACTIN FILAMENTS -MYOSIN HEAD binds to ACTIVE SITE on THIN FILAMENT

Within a sarcomere, the overlap of actin and myosin produce the _______ band?

A

M line

A dark, transverse protein complex that connects thick filaments in the middle of the H Band.

Electrical potential (Voltage)

A difference in electrical charge from 1 point to another

Synaptic Cleft

A narrow space between an axon terminal and the membrane of the postsynaptic cell, across which a neurotransmitter diffuses

Synaptic Vesicles

A spheroidal organelle in an axon terminal containing neurotransmitter, which are filled with acetylchonline (ACh)

Smooth Muscle Tone

A state of continual tonic contraction achieved by the skeletal cells by its fatigue resistance and latch-bridge mechanism of smooth muscle

Muscle Tone

A state of partial contraction of muscles -Makes muscles ideally ready for action -Maintained by CNS

Neuromuscular Junction (NMJ) OR Motor End Plate

A synapse between a nerve fiber and a muscle fiber

What do muscle contractions rely on?

ATP

Phosphagen system

ATP and CP; -Provide nearly all the energy used for SHORT BURSTS of INTENSE ACTIVITY

Autorhythmic

Ability to contract rhythmically and independently; the heart

How does muscle return to its resting length?

Achieved by some PULLING FORCE on the muscle and stretching it

Regulatory Proteins

Act like a switch determining when the fiber can contract, and when it cannot -Tropomyosin and Troponin

I Bands are composed primarily of WHICH protein?

Actin

Movement in Smooth muscle cell

Actin filaments attach to the intermediate filaments as well as directly to the dense bodies, so their movement (powered by myosin) is transferred to the sarcolemma and shortens the cell.

Long-Term Energy

Aerobic Respiration -Occurs after 40 seconds -Metabolizes glucose and fatty acids

Cardiac muscle relies mainly on what type of ATP Production?

Aerobic respiration

Immediate Energy (Short, intense exercise... 100m Dash)

Aerobic respiration using oxygen from MYOGLOBIN -Oxygen quickly depleted; catches up later (~40 sec) -Body borrows phosphate groups (Pi) from other muscles and transfers them to ADP 2 Enzymes control this: 1) Myokinase 2) Creatine Kinase

Striations

Alternating Light and Dark transverse bands, reflecting an overlapping arrangement of their internal contractile proteins

Dystrophin

An enormous protein that is located between the Sarcolemma and the outermost myofilaments -Leads to the fibrous endomysium surrounding the muscle fiber -When the thin filaments move, it pulls on the dystrophin, which pulls on the extracellular tissues leading to the tendon -Assists in movement of muscle fiber

Myosin light-chain kinase

An enzyme that adds a phosphate group to a small regulatory protein on the myosin head -Activated by calmodulin -This then activates myosin ATPase, enabling it to bind to actin and hydrolyze ATP (Power and Recovery strokes)

Acetylcholinesterase (AChE)

An enzyme that breaks down ACh after the ACh has stimulated the muscle cell

Short-Term Energy

Anaerobic fermentation is achieved -Production of lactate

Calmodulin

Associated with the myosin, it's where calcium binds (IDENTICAL TO TROPONIN) (Calcium Modulating Protein)

Example of internal/external/contraction phase

At first, internal tension would only stretch the rubber band. Then, as the rubber band became taut, external tension would lift the weight.

Somatic Motor Fibers

Axon of a somatic motor neuron

Somatic Motor Fibers and Muscle Fibers

Axons reach multiple muscle fibers; but each muscle fiber is supplied by ONLY 1 MOTOR NEURON

Z Disk (Z Line)

Bisects each Light I Band; Provides anchorage for the thin and elastic filaments

Tropomyosin

Blocks the active sites of 6 or 7 G actins and prevents myosin from binding to them -Prevents motion --Has Troponin

Cross-Bridge

Bond between myosin and actin

WHAT CAUSES CONTRACTION IN ALL MUSCLE CELLS??

CALCIUM IONS!!!!!!! Ca2+

MEMBRANE IS POLARIZED. What is more negative, cell interior or exterior?

CELL INTERIOR

Calsequestrin

Cal = Calcium; Sequestr = To Separate A protein in the sacroplasmic reticulum that binds calcium

What stimulates smooth muscle?

Calcium

Control of Contraction of Muscle Fibers

Calcium ions are released into sarcoplasm to activate contraction; calcium binds to troponin; troponin is bound to tropomyosin; and tropomyosin blocks the active sites of actin, so that myosin cannot bind to it when muscle is NOT stimulated

Aerobic respiration

Can be used to extract energy from other organic compounds besides glucose, including FATTY ACIDS

Cadiac Muscle Name?

Cardiomyocytes

Significance of DRYSTOPHIN??

Causes Motion of Cell?

Factors of Muscle Strength

1) Muscle Size -Greater size = more myosin-actin cross bridges; more tension can be generated 2)Fascicle Arrangement 3) Size of active motor units -Larger motor units produce stronger contractions THAN smaller ones 4) Multiple motor unit summation 5) Temporal Summation -Greater frequency of stimulation, the stronger the muscle contraction 6) Length-Tension Relationship -Muscle resting at optimum length is prepared to contract more forcefully than a muscle that's contracted/stretched 7) Fatigue -Rested muscles contract more strongly than fatigued ones

Excitation Process?

1) Nerve signal ARRIVES at the AXON TERMINAL, and opens VOLTAGE-GATED CALCIUM CHANNELS. -CALCIUM IONS ENTER TERMINAL 2) Calcium stimulates the synaptic vesicles to release acetylcholine (ACh) into the synaptic cleft 3) ACh diffuses across synaptic cleft and binds to receptors on the sarcolemma -Receptors are LIGAND-GATED Ion channels 4) 2 ACh molecules must bind to EACH receptor to open the channel. When it opens... -NA+ flows quickly INTO the cell -K+ flows OUT of cell -LEADS TO END-PLATE POTENTIAL (EPP) 5) Areas of sarcolemma next to end plate have voltage gated ion channels that open in response to EPP. -Some allow Na+ to enter cell; others allow K+ to leave ACTION POTENTIAL formed by movements of these ions

Reasons for fatigue in high-intensity, short-duration exercise

1) Potassium accumulation -Each action potential releases K+ from the sarcoplasm to the ECF --Results in Hyperpolarization ---Interferes w/ release of calcium from Sarcoplasmic reticulum 2) ADP/Pi Accumulation -ADP slows cross-bridge cycling mechanism of contraction -Pi inhibits calcium release from the SR

5 Components of Muscle Fiber?

1) Sarcolemma 2) Sarcoplasm 3) Myofibril (Made of Myofilaments) 4) Glycogen 5) Myoglobin

Twitch strength

DEPENDs ON STRENGTH OF STIMULUS; Greater stimulus, greater tension developed (More muscle cells excited) IF STIMULUS IS CONSTANT... TENSION INCREASES WITH... -Depends on stimulus FREQUENCY -Greater with better hydration -Greater with higher temps -Becomes weaker as muscle fatigues -Depends on how stretched the muscle was just before it was stimulated

Latent Period

Delay between the onset of stimulus and onset of twitch

Excess Post-exercise Oxygen Consumption (EPOC)

Difference between the elevated rate of oxygen consumption at the end of an exercise and the normal rate at rest

Terminal Cisterns

Dilated end sacs of the sacroplasmic reticulum

Internal Tension

Force generated that causes no shortening of the muscle; not seen on myogram

How does Smooth muscle cell get most of its calcium?

Has Sparse SR; therefore, its gets if from the EXTRACELLULAR FLUID THRU GATED CALCIUM CHANNELS IN THE SARCOLEMMA

Unlike skeletal and cardiac muscle, smooth muscle can..

Hypertropgy, mitotically divide and hyperplasia (Cell Division)

Striation Drawing

I A I H Z Z I = I Band A = A Band H = H Band Z = Z Disk

Advantage of having multiple motor units in each muscle cell?

Muscle fibers fatigue when subjected to continual stimulation; allows other motor units to take other and stimulate other cells , while the fatigued ones recover

White muscles

Muscles composed mainly of FG Fibers -Due to lack of myoglobin content

Red Muscles

Muscles composed mainly of SO Fibers -Due to abundant Myoglobin

Myoblast

Myo = Muscle; Blast = Make/Precursor Stem cells that fuse to produce a muscle fiber

Satellite Cells

Myoblasts that remain unspecialized between the muscle fiber endomysium. -Regenerate damaged skeletal muscle

Single-Unit (unitary) Smooth Muscle

Myocytes of this type of muscle are electrically coupled to each other by gap junctions -Nerve varicosities are not associated with a specific myocyte, but stimulate several of them at once when they release a neurotransmitter -Visceral Muscle --Found in Blood vessels, digestive, respiratory, and urinary tracts

Basal Lamina

Separates muscle fiber and nerve ending from surrounding connective tissue -Also passes through synaptic cleft and virtually fills it

Why do muscle fibers have many nuclei?

Several Stem Cells called Myoblasts FUSE TOGETHER to produce EACH MUSCLE FIBER, with each myoblast contributing 1 nucleus

How is skeletal muscle different from the other types of muscle?

Skeletal muscle has MULTIPLE NUCLEI

If a muscles nerve connections are severed, a muscle is...?

Paralyzed

Creatine Phosphate

Phosphate-storage molecule; donates it to creatine kinase

What special terms are given to the plasma membrane, cytoplasm, and smooth ER of a muscle cell?

Plasma Membrane: Sarcolemma Cytoplasm: Sarcoplasm Smooth ER: Sarcoplasmic Reticulum

Anaerobic Threshold (Lactate Threshold)

Point at which muscles transition to anaerobic fermentation to Generate ATP by GLYCOLYSIS -Increase in blood lactate

Excitation

Process in which action potentials in the nerve fiber lead to action potentials in the muscle fiber

Define responsiveness, conductivity, contractility, extensibility, and elasticity. State why each of these properties is necessary for muscle function.

Responsiveness: Refers to cell's ability to become excited; creates membrane potential upon being excited Conductivity: Muscle cells transmit impulse that excites them. Extensibility: Muscle cells ability to elongate Elasticity: Ability of muscles cell to return back to original size after extending/contracting

Striations:

Results from excessive concentration of myosin and actin

How to remember Sodium-Potassium Pump?

SALTY BANANA -Na+ on outside -K+ on inside

Triad

The T tubule and 2 cisterns associated with it

Myogram

The TIMING and STRENGTH of a muscle's CONTRACTION

Intercalated Discs

The branches that join cardiomyocytes together -Have ELECTRICAL GAP JUNCTIONS, allowing each cardiomyocyte to directly stimulate its neghbor and MECHANICAL JUNCTIONS that keep the cardiomyocytes from pulling apart when the heart contracts

Threshold

The minimum voltage necessary to generate an action potential in the muscle fiber

Connective tissues of endomysium, perimysium, and epimysium are CONTINUOUS with COLLAGEN FIBERS of TENDONS and those, in turn, with the COLLAGEN of the bone matrix

Thus, when a muscle fiber contracts, it pulls on those collagen fibers and typically moves a BONE

Why Junctional Folds?

To increase S.A. of ACh-sensitive membrane

Myokinase

Transfers Pi from one ADP to another, converting the latter to ATP that myosin can use

What happens when calcium ions bind to troponin?

Tropomyosin moves off the active site on actin; allowing myosin to bind to it and cause contraction

Transverse (T) Tubules

Tubular in-foldings of the sarcolemma that penetrate through the cell and emerge on the other side -Closely associated with 2 terminal cisterns running alongside it, 1 on each side

Complete (Fused) Tetannus

Twitches fuse into a single, nonfluctuating contraction -Doesn't happen in body; motor neurons don't fire that fast

Temporal Summation

Two stimuli arriving close together in time

Fine motor control requires which of the following?

Small motor units

Size Principle

Smaller, less powerful motor units with smaller, slower nerve fibers are activated first. If more power is needed, then larger motor units with larger, faster nerve fibers are SUBSEQUENTIALY activated

Excess of what ion in ICF?

K+

Resting membrane potential (RMP)

Electrical charge of cell -Negative value

Elastic Filament

-Run through core of each THICK Filament and anchors it to structures called the Z Disk at 1 end AND M line at the other -Stabilizes thick filament, centers it between thin filaments, and prevents over-stretching, recoils like a spring after a muscle is stretched Made of protein called TITIN

Purpose of AChE?

-Stops cell from contracting

Depolarization:

Electrical potential in cell becomes less negative -IE: Na+ rushing into cell

Latch-Bridge Mechanism

Enables the myosin to remain attached to the actin for a prolonged time WITHOUT consuming more ATP -What causes muscle cells to be very slow to relax

Myosin ATPase

Enzyme in the head of the myosin that HYDROLYZES ATP into ADP and phosphate

Excitation-Contraction Coupling

Events that link action potentials on the sarcolemma to ACTIVATION of the MYOFILAMENTS, thereby preparing them to CONTRACT

Small Motor Units are beneficial for?

When fine Control is needed -Usually supplied by small, relatively sensitive neurons -IE: Found in hand/eye

Large Motor units

When strength is more important than fine control -Muscle fibers innervated by LESS SENSITIVE neurons w/ larger cell bodies -IE: Found in calves of leg

Thin Filaments

-Composed primarily of 2 intertwined strands of a protein called Fibrous (F) Actin --Each F actin is like a bead necklace ---String of subunits called Globular (G) actin (Active site where myosin binds) -Consists of Protein called Tropomyosin

Thick Filaments

-Made of several hundred molecules of a protein called MYOSIN -15 nm in diameter -Bare Zone in middle of thick filament; no heads

Why EPOC occurs?

-O2 is needed to regenerate ATP aerobically -Make myoglobin -Dispose of lactate -B/c exercise raises body temp; consumes more oxygen

Modes of smooth muscle stimulation

1) Autonomic nerve fibers and neurotransmitters 2) Chemicals -Hormones, CO2, O2, low pH, oxytocin 3) Temperature -Cold induces contraction of smooth muscle 4) Stretch -Stomach and urinary bladder contract when stretched by food or urine 5) Autothythmicity: -Present in those found in stomach and intestines

2 Forms of isotonic contraction

1) Concentric Contraction 2) Eccentric Contraction

What happens when a nerve or muscle cell becomes stimulated?

1) Depolarization: Ion channels in plasma membrane open and Na+ instantly flows INTO the cell -Goes down its electrochemical gradient 2) Repolarization -When the electrical potential in the inside of the membrane becomes NEGATIVE again

Name and define the three layers of collagenous connective tissue in a skeletal muscle.

1) Endomysium: Fibrous connective tissue surrounding muscle fibers 2) Perimysium: Fibrous connective tissue surrounding groups os muscle fibers; creates fascicles 3) Epimysium: Connective tissue surrounding whole skeletal muscle

Functions of Muscle

1) Excitability (Responsiveness): -When stimulated by chemical signals, stretch, and other stimuli, muscle cells respond with ELECTRICAL CHANGES across the plasma membrane 2) Conductivity: -Stimulation of a muscle cell produces more than a local effect. Local electrical excitation sets off a wave of excitation that travels RAPIDLY from CELL TO CELL and initiates processes leading to contraction 3) Contractility: -Muscle cells SHORTEN (CONTRACT) substantially when stimulated. Allows them to pull on bones and other organs to create movement 4) Extensibility: -Ability of cells to be able to STRETCH AGAIN between contractions 5) Elasticity: - Ability of a STRETCHED STRUCTURE to return to its original dimensions when tension is released

4 Phases of muscle contraction and relaxation?

1) Excitation 2) Excitation-Coupling 3) Contraction 4) Relaxation

Fatigue from low intensity, long-duration exercise

1) Fuel depletion -Not enough glycogen and blood glucose 2) Electrolyte loss -Loss of electrolytes through sweating alters ion balance of ECF; enough to reduce muscle excitability 3) Central Fatigue -Exercising muscle generates ammonia, which is absorbed by the brain and inhibits motor neurons of the cerebrum

Myocyte Structure (Smooth Muscle Cell)

1) Fusiform 2)Endomysium, NO PERIMYSIUM, FASCICLES, or EPIMYSIUM 3) 1 nucleus 4) Scanty SR 5) NO T-TUBULES 6) No Striations, sarcomeres, or myofibrils 7) Dense bodies

Effects of Stimulus frequency on Muscle Tension

1) Temporal Summation 2) Wave Summation 3) Incomplete Tetanus

3 Types of Myofilaments?

1) Thick Filaments 2) Thin Filaments 3) Elastic Filaments

2 Types of Fast-Glycotic Fibers?

1) Type IIA 2) Type IIB -Described up above previously

Troponin

A calcium-binding protein found on tropomyosin

Titin

A huge springy protein

H Band

A lighter region within the middle of the A Brand; thin filaments don't reach here; Thick filaments linked to each other through the M line

Basal Lamina

A mat of collagen and glycoprotein

Myosin

A motor protein that constitutes the thick myofilaments of muscle, and has globular, mobile heads of ATPase that BIND to actin molecules; serves contractile functions in multiple cell types -Protein that looks like a golf club -2 chains intertwined to form a shaftlike tail, and a double globular head projecting from it an angle

Eccentric Contraction

A muscle lengthens as it maintains tension -Dropping Dumbbell -More prone to injury

Concentric Contraction

A muscle shortens as it maintains tensions Lifting dumbbell

Acetylcholine (ACh)

A neurotransmitter released by somatic motor fibers, composed of choline and an acetyl group

Myofilament:

A protein microfilament RESPONSIBLE for the CONTRACTION of a MUSCLE CELL; composed mainly of ACTIN or MYOSIN

Twitch

A quick cycle of contraction and relaxation

Action Potential

A rapid voltage change in which a plasma membrane briefly reverses electrical polarity; has a self-propagating effect that produces a traveling wave of excitation in nerve and muscle cells -Negative RMP, Positive RMP, Negative RMP

Type IIA Fiber (Intermediate Fibers)

Combine fast-twitch response with aerobic fatigue-resistant metabolism -Typically not in humans

Cross-Training

Combines endurance and resistance exercise

Resistance Exercise

Contraction of muscles against a load that RESISTS movement -Causes muscle fibers to enlarge

Isotonic Contraction

Contraction with a change in length -Muscle shortens and moves the load

Sarcoplasm

Cytoplasm of muscle fiber

How does neurotransmitter travel from neuron?

Exocytosis; Neurotransmitter functions as a chemical messenger from nerve cell to muscle cell

Sacroplasmic Reticulum (SR)

Forms a network around each myofibril

Pacemaker

Found in heart; rhythmically sets off waves of electrical excitation, which travels through the muscle and triggers the contraction of the heart chambers

Glycogen-Lactate System

Glycogen/glucose is metabolized to lactate -Generated a net yield of 2 ATP for each glucose consumed

Overall Contracting Effort

Muscle Shortens B/c its individual sarcomeres shorten and pull the Z discs closer to each other, and dystrophin and the linking proteins pull on the extracellular proteins of the muscle -As Z discs are pull closer (Sarcomere shortens), they pull on the sarcolemma to achieve overall shortening of the cell

Endurance (Aerobic) Exercise

Improves fatigue resistance of muscles by enhancing the use and delivery of oxygen -Jogging, swimming

Which type of contraction maintains joint stability and posture?

Isometric!

Junctional Folds

In-foldings within the sarcolemma

Fibrous (F) Actin

Intracellular protein that provides cytoskeletal support and interacts with myosin to cause cellular movement

When the muscle fiber is stimulated, what happens?

Ion gates in the SR membrane OPEN and Ca2+ floods into the cytosol to ACTIVATE CONTRACTION

Isometric Contraction

Iso = Same; metr = Length; ic = Pertaining to -Contraction without a change in length -PRELUDE TO MOVEMENT

Myofibrils

Long protein cords that MAINLY OCCUPIES the sacroplasm -1µm in diameter

Sliding Filament Theory

Mechanism of Contraction -Myofilaments don't become shorter during contraction; thin filament movement pulls Z discs behind them, causing EACH sarcomere as a WHOLE to shorten

Smooth muscle regenerates through...

Mitosis

Wave Summation:

One wave of contraction is added to another -Muscles only relaxes partially between stimuli

What is the difference between a myofilament and a myofibril?

Myofilaments make up myofibrils

List five proteins of the myofilaments and describe their physical arrangement.

Myosin: Makes up thick filaments; looks like golf club; motor protein Fibrous Actin (F) and Globular Actin (G): Makes up Thin Filament; G actin = subunits that consist of active site that binds MYOSIN; consists of Tropomyosin: Found on G actin; blocks active sites from myosin; prevents contraction Troponin: Calcium-binding protein; found on tropomyosin Titin = Spongy protein found in Elastic Filaments which run through core of each thick filament and anchor it to Z discs

ICF has what charge?

NEGATIVE

Smooth muscle

NO STRIATIONS, myocytes are small (Allows for fine control of tissues); Can remain contracted for a long time; FUSIFORM

Lactate has an affect on muscle fatigue

NO; removed very quickly

Excess of what ion in ECF?

Na+

Involuntary

Not under conscious control; NEVER attached to bones -Cardiac and smooth muscle tissue

Caveolae

Numerous little pockets found in the sarcolemma where a smooth muscle cell's calcium channels are concentrated

Creatine Kinase

Obtains Pi from a phosphate storage molecule, (Creatine Phosphate (CP)), and donates it to ADP to make ATP

Motor Unit

One motor neuron and all the muscle fibers innervated by it -Muscle fibers contract simultaneously

Nerve Fiber and excitation of muscle fiber

One nerve fiber stimulates the muscular fiber at SEVERAL points within the NMJ -Forearm and fingertips = Branching of Neuron; pressing fingertips into clay

Muscle Fibers (Myofiber):

One skeletal muscle cell -VERY LONG

Muscle Fatigue

Progressive weakness and loss of contractility that results from prolonged use of the muscles

Dense Bodies

Protein plaques that serve the purpose of the Z-discs

ACh receptors

Proteins found in a muscle fiber's membrane across from the axon terminal that bind to ACh

Contractile Proteins

Proteins that do the work of Shortening the Muscle Fiber -Myosin and actin

Myoglobin

Red oxygen-binding pigment that provides some of the oxygen needed for muscular activity -Stores Oxygen

What is longer; Contraction phase of Relaxation phase?

Relaxation phase

What muscle fiber makes up small motor units?

SO muscle fibers -Produce more precise movements

Sarcolemma

Sacro = Muscle/Flesh; Lemma = Husk Plasma membrane of a muscle fiber

How is the RMP maintained?

Sodium-Potassium pump -Ions going UP their GRADIENT

Glycogen:

Starchlike carbohydrate that provides ENERGY for the cell during HEIGHTENED levels of exercise

Describe a Cardiomyocyte

Striated, short, thick, 1 or 2 nuclei, NO PERIMYSIUM OR EPIMYSIUM, large T-Tubules (Admit more Ca2+ from ECF)

Globular (G) Actin

String of subunits of F Actin -Has an Active Site that can bind the HEAD OF A MYOSIN MOLECULE

Voluntary:

Subject to conscious control; we control our bones

Electrochemical Gradient

Substance traveling down its concentration gradient and charge gradient

Incomplete Tetanus

Sustained fluttering contraction -Results from high frequency stimuli

Significance of T Tubule and calcium release?

T Tubule SIGNALS the Terminal Cisternae WHEN to release these CALCIUM BURSTS

Explain movement of Filaments in sliding filament theory

THIN FILAMENT slides over the THICK FILAMENT

Contraction Phase

Tension developed that can move a resisting object, or load, such as a body or limb

External Tension

Tension developed that can move a resisting object, or load, such as a body or limb

Multiunit Smooth Muscle

Terminal branches of a nerve fiber synapse with individual myocytes to form a motor unit -Each varicosity is associated with a particular myocyte, and each myocyte responds independently of all the others—hence the name multiunit.

Why is the Transverse Tubule closely associated with the terminal cisterns?

The electrical excitation spreading down the T tubule must EXCITE the opening of calcium gates in the terminal cisterns

Explain why filament doesn't slide back into position after the POWER STROKE of the myosin?

The myosin heads don't all stroke at once but contract sequentially. -Some are bound to the thin filament making sure it doesn't go back into its original place, while the other half are extending forward to GRASP IT farther down

Maximum Oxygen Uptake (Vo2 max)

The point at which the rate of oxygen consumption reaches a plateau and increases no further with an added workload

Synapse

The point where a nerve fiber meets any target cell

Sarcomere

The portion of myofibril from one Z disc to the next; constituting ONE CONTRACTILE UNIT -Functional, contractile unit of muscle fiber -Thousands of them line up to form a myofibril

Recruitment OR Multiple Motor Unit (MMU) Summation

The process of bringing more motor units into play -Causes more muscle fibers to contract; develops greater tension

End-Plate Potential (EPP)

The rapid up-and-down fluctuation in voltage at the motor end plate -Caused by Na+ entering cell (Depolarization) and K+ leaving cell (re-polarization)

Electrophysiology

The study of the ELECTRICAL ACTIVITY of cells

Axon Terminal

The swollen tip at the distal end of an axon; the site of synaptic vesicles and neurotransmitter release

Length-Tension Relationship

The tension generated by a muscle, and therefore the FORCE of its contraction, depends on how stretched/contracted it was at the outset

Length/Diameter of Muscle cells

Usually 100 µm in diamter and 3 cm long

Skeletal Muscle (Multinucleate or not?) (Voluntary Vs. Involuntary) (Striated vs Un-Striated?)

Voluntary, striated muscle that's attached to 1 or more bones -Exhibits STRIATION -Multiple nuclei

Denervation Atrophy

Weakening of muscle that does not have a nerve.

Slow-Twitch Fibers, Type I Fibers, Slow Oxidative (SO), Red Fibers (B/c of High myoglobin content)

Well adapted for endurance and fatigue resistane -Due to Aerobic Respiration --Thus, they are surrounded by lots of blood vessels, rich in mitochondria, and have high concetration of myoglobin ---Thin (minimizes distance traveled by O2) ----Slow release of Ca2+ by Sarcoplasmic reticulum

Fast-Twitch Fibers, Fast Glycotic (FG), Type II Fibers, WHITE FIBERS (LACK OF MYOGLOBIN)

Well adapted for quick responses -Dependent upon anaerobic fermentation (Produces ATP more quickly) BUT less efficiently THAN AEROBIC RESPIRATION -Important in eye/hand muscles. -Sarcoplasmic reticulum releases Ca2+ fast -Myosin has quick ATP hydrolysis and cross-bridge cycling -Less myoglobin (WHITE FIBERS)

Power Stroke

When Myosin releases ADP and Phosphate and flexes into a bent, LOW-ENERGY position, TUGGING THE THIN FILAMENT ALONG WITH IT

Relaxation Phase

When the Ca2+ level in the cytoplasm falls, myosin releases the thin filaments and MUSCLE TENSION DECLINES

Contraction

When the muscle fiber develops TENSION and may shorten

Recovery Stroke

When the myosin hydrolyzes a new ATP, recocks, and attaches to a new active site farther down the thin filament

Relaxation

When the nerve fiber stops stimulating a muscle fiber, the muscle fiber relaxes and RETURNS to its RESTING LENGTH

Varicosities

When the nerve releases a flood of neurotransmitter into the tissue