Bio 270 Lecture Exam #2 (ch.8-13)

series arrangement of circulation

(one leads to another) in the way blood moves from lungs --> heart --> body --> lungs, etc.

contractile cells

- 99% of cardiac muscle cells - do mechanical work of pumping - normally do not initiate own action potentials

electrocardiography (EKG/ECG)

- recording of overall spread of electrical activity throughout heart during depolarization and repolarization (not a recording of a single action potential in a single cell at a single point in time) - comparisons in voltage detected by electrodes at two different points on body surface, not the action potential - different parts of ECG recorded can be correlated to specific cardiac events

twitch summation

- results from sustained elevation of cytosolic Ca2+ - more Ca2+ means more forceful contraction - cell is stimulated so quickly that it doesn't have time to fully relax after initial stimulation causing the force generated to add up

atrioventricular (AV) valves

- right and left AV valves positioned between atrium and ventricle on right and left sides - prevent back-flow of blood from ventricles into atria during ventricular emptying - right AV valve = tricuspid valve - left AV valve = bicuspid valve or mitral valve

Transverse tubules (T tubules)

- run perpendicularly from surface of muscle cell membrane into central portions of the muscle fiber - action potential on surface membrane spreads down into T-tubule due to membrane being continuous with surface membrane - spread of action potential down a T tubule triggers release of Ca2+ from sarcoplasmic reticulum into cytosol

cardiac action potential and excitation contraction coupling

- Ca2+ induced and Ca2+ release - Ca2+ enters cytosol from ECF through openings of L-type Ca2+ channels during action potential --> triggers release of more Ca2+ from SR - extra supply of Ca2+ plus slow removal of Ca2+ back into SR --> long period cardiac contraction

circuit of blood flow

- sides of the heart: function as two separate pumps - right side part of pulmonary circulation (deoxygenated) - left side part of systemic circulation (oxygenated)

locations of non-contractile cells capable of autohymicity

- sinoatrial node (SA node) - atrioventricular node (AV node) - bundle of HIS (atrioventricular bundle) - Purkinje fibers

sinoatrial node (SA node)

- specialized region in right atrial wall near opening of superior vena cava - pacemaker of the heart

sliding filament/cross bridge cycling model

- states that muscle contraction involves the sliding movement of the thin filaments (actin) past the thick filaments (myosin) - contraction results in 'sarcomere shrinking' - the sarcomere decreases in length

rigor mortis

- stiff muscles result when ATP is broken down to form cross bridges - no more ATP makes it so the cross bridges cannot break --> muscle tension - starts 3-4 hrs after death - complete in 24 hrs - resolution after a few days due to protein decomposition

skeletal muscle structure

- striations - sacromere - myosin - actin - tropomyosin and troponin

skeletal muscle metabolism

- supplying ATP during muscle contraction 1. transfer of high-energy phosphate from creatine phosphate to ADP 2. glycolysis 3. oxidative phosphorylation

oxidative phosphorylation (citric acid cycle and electron transport system)

- takes place within muscle mitochondria if sufficient O2 is present - relatively slower but more energy is released from fat stores - actively supported this way is "aerobic" (endurance type exercise) - starts to be used after 20 min of exercise

tropomyosin

- threadlike molecules that lie end to end alongside groove of actin spinal - covers actin sites blocking interaction with myosin that leads to muscle contraction

atria

- upper chambers - receive blood returning to heart (from body - right, and from lungs - left) and transfer it to lower chambers

glycolysis

- using glucose directly - lactic acid produced as a by product is O2 is in short supply (muscle soreness during exercise) - anerobic use of glucose only last 15 mins or so

venae cavae (cava)

- veins returning blood to the right atrium from the body - oxygen has been extracted from this blood and carbon dioxide has been added to it

relaxation of skeletal muscle

- acetylcholinesterase breaks down ACh at neuromuscular junction - muscle fiber action potential stops - Ca2+ moves back into sarcoplasmic reticulum through active transport (why it takes longer) - relaxation depends on reuptake of Ca2+ into sarcoplasmic reticulum

slow fiber

- aerobic - endurance running - slow oxidative - red muscle

fast fiber

- anaerobic - sprinting - fast glycolytic - white muscle

intermediate fiber

- anaerobic (mostly) - fast running, medium endurance - fast oxidative - white muscle

semilunar valves

- aortic and pulmonary valves - lie at juncture where major arteries leave ventricles - prevented from everting by anatomic structure and positioning of cusps

smooth muscle

- appears throughout the body systems as components of hollow organs and tubes - unstriated - spindle shaped cells with a single nucleus - involuntary - hormonal control (nitric oxide and adenosine) - ANS control (ex. GI tract innerved by ParaNS) - cells arranged in sheets within muscle - built for slow and sustained contractions - syncytium

role of calcium in skeletal muscle contraction

- binds troponin which causes tropomyosin to move away from myosin binding site on actin - amount of Ca2+ determines how many cross bridges can be formed - determines the amount of contractility a muscle cell will have for a muscle contraction

parallel arrangement of circulation

- blood moves to 2 different organs simultaneously - can control which tissues get ore or less blood based on need - arterioles at each capillary bed will constrict or dilate to limit or let more blood through respectively

Bundle of HIS (atrioventricular bundle)

- cells originate at AV node and enters inter-ventricular septum - divides to form right and left bundle branches which travel down septum; curve around tip of ventricular chambers, travel back toward atria along outer walls

skeletal muscle fibers

- classified based on ATP hydrolysis and synthesis - fast, slow, and intermediate - based on myosin ATPase activity - oxidative v. glycolytic - red vs. white

myosin

- component of thick filament - protein molecule consisting of two identical subunits shaped somewhat like a golf club (tail ends are intertwined around each other and globular heads project out at one end) - tails oriented toward center of filament and globular heads protrude outward at regular intervals - heads from cross bridges between thick and thin filaments

muscle

- comprises largest group of tissues in body - 3 types: skeletal, cardiac, smooth - striated or unstriated - voluntary or involuntary

myofibrils

- contractile elements of muscle fiber - regular arrangement of thick and thin filaments - displays alternating dark and light bands giving appearance of striations

important sites of cross bridges

- critical to contractile process 1. an actin-binding site 2. a myosin ATPase (ATP-splitting site) - to release energy

heart

- hollow, muscular organ about the size of a clenched fist - positioned between sternum and vertebrae - position makes it physically possible to manually drive blood from heart when it is not pumping effectively (CPR) - serves as pump that establishes the pressure gradient needed for blood to flow to tissue - 2 chambers

power stroke in skeletal muscle

- how the filaments move across each to actually contract muscle 1. activated cross bridge bends toward center of thick filament, "rowing" in thin filament to which it is attached 2. sarcoplasmic reticulum releases Ca2+ into sarcomere 3. myosin heads bind to actin 4. myosin heads swivel toward center of sarcomere 5. ATP binds to myosin head and detaches it from actin 6. ATP breaks cross bridge 7. hydrolysis of ATP transfers energy to myosin head and reorients it 8. contraction continues if ATP is available and Ca2+ level in sarcoplasm is high

motor unit recruitment

- increase strength of contraction - more and more motor units are recruited (stimulated to contract)

action potential of cardiac contractile cells

- initiated by auto-rhythmic cells - exhibit prolonged plateau phase accompanied by a prolonged period of contraction (ensures adequate ejection time) 1. rising phase due to opening voltage-gated Na+ channels 2. only thing different is plateau phase due to activation of slow L-type Ca2+ channels and decrease in K+ permeability (closed channels) 3. falling phase due to the closing of Ca2+ channels and the opening of K+ channels

stroke volume (SV)

- volume of blood ejected by each ventricle each minute (measured in liters per minute) - influenced by two types of controls - increase stroke volume by increasing strength of heart contraction 1. intrinsic control 2. extrinsic control SV=EDV-ESV

role of ATP in skeletal muscle

- it can cause the cross-bridge to be broken - hydrolysis gives energy for myosin to extend and get ready for the next binding - needed for relaxation

troponin

- made of three polypeptide units: 1. one binds to tropomyosin 2. one binds to actin 3. one binds with Ca2+ - when not bound to Ca2+, it stabilizes tropomyosin in blocking posistion over actin's cross-bridge binding sites - Ca2+ binds to it, helping move tropomyosin away from blocking site - allows actin and myosin to bind at the cross-bridge resulting in muscle contraction

skeletal muscle

- makes up muscular system - striated - voluntary

sarcoplasmic reticulum

- modified endoplasmic reticulum - not continuous but encircles myofibril throughout its length - major source of Ca2+ to muscle cell (sequestered Ca2+)

striations

- muscle consists of a number of muscle fibers lying parallel to one another and held together by connective tissue - multincleated - large, elongated, and cylindrically shaped - fibers usually extend entire length of muscle

tetany

- occurs if muscle fiber is stimulated so rapidly that it does not have a chance to relax at all between stimuli - maximal force is generated at this point

muscle twitch

- one action potential causes one muscle twitch - too short and too weak to be useful - normally does not take place in body

motor unit

- one motor neuron and the muscle fibers it innervation - muscle fibers varies among different units - precise, delicate movement contain fewer fibers and vis-versa

valves

- one-way prevent back-flow at the heart - assures when pressure is generated by the heart the flow of blood is unidirectional

arterioles

- primary sites of regulation of vascular flow - drugs/therapies have more direct effects on blood pressure and blood flow

actin

- primary structural component of thin filaments - spherical shape - works with tropomyosin and troponin - has special binding site for attachment with myosin cross bridge that results in contraction of muscle fiber

flow rate

- proportional to radius (to the 4th power) - inversely proportional to viscosity and length

functions of controlled muscle contractions

- purposeful movement of the whole body or parts of the body - manipulation of external objects - propulsion of contents though various hollow internal organs - emptying of contents of certain organs to external environment

Wiggar's diagram

1. atria depolarizes 2. atrial contraction - pressure increases 3. ventricle topped off - filled - 15-20% of ventricular blood volume is due to atrial contraction - important with fast heart rates where ventricle may not have ample time for filling 4. ventricle depolarized 5. ventricle contraction - pressure increases because of contraction against closed valves - isovolumetric contraction - AV valve closure = first heart sound 6. aortic valve opening 7. ventricular ejection of blood 8. ventricular repolarization 9. aortic (or pulmonary) valve closure - 2nd heart sound 10. isovolumetric relaxation - all valves are closed but muscle is relaxing 11. AV valve opens 12. passive ventricular filling - 3rd heart sound

spread of cardiac excitation

1. cardiac impulse originates at SA node 2. action potential spreads throughout right and left atria via interatrial pathway 3. impulse passes from atria into ventricle through AV node 4. AV node delay (ensures atrial contraction precedes ventricular contraction to allow complete ventricular filling) 5. impulse travels rapidly down interventricular septum by means of bundle of His 6. impulse rapidly disperses throughout myocardium by means of Purkinje fibers 7. rest of ventricular cells activated by cell-to-cell spread of impulse through gap junctions

pacemaker potential and action potential

1. decreased permeability of K+ due to closing of K+ channels (Na+ channels stay unchanged) 2. opening of transient voltage gated Ca2+ channel (T type Ca2+ channel) --> further depolarization to threshold --> action potential 3. opening of longer lasting voltage gated Ca2+ channel (L-type Ca2+ channel) 4. falling phase of action potential due to opening of voltage gated K+ channels

why does relaxation time take longer than contraction time?

Takes time to bring all the Ca2+ back into sarcoplasmic reticulum and to break the cross bridges, using a lot of ATP (going against concentration gradient) and using active transport rather than diffusion

why is their a latent period

Takes time to get electrical potential in the cell to trigger release of Ca2+ from sarcoplasmic reticulum, bind to troponin, the movement of tropomyosin off of the active site, formation of cross bridges, and taking up any slack found in the muscle

thick filaments

myosin (protein)

general trend for cardiac cycle

electrical event --> contraction event --> pressure generated --> movement of blood

determinants of blood pressure

cardiac output, stroke volume, systemic vascular resistance

arteries

carry blood away from ventricles to tissues

systemic circulation

circuit of vessels carrying blood between heart and other body systems

pulmonary circulation

closed loop of vessels carry blood between heart and lungs

transfer of high energy phosphate from creating phosphate to ADP

first energy storehouse tapped at onset of contractile activity - lasts only a few minutes

electrical activity of the heart

heart beats rhythmically as result of action potentials it generates by itself (autorhythmicity)

blood vessels

passageway through which blood is distributed from heart to all parts of body and back to heart

Z lines

connects thin filaments of two adjoining sarcomeres

I band

consists of remaining portion of thin filaments that do not project into A band

cardiac cycle

contraction (systole), relaxation (diastole), changes of blood flow through the heart

systole

contraction and emptying of ventricles

excitation-contraction coupling in skeletal muscle

contraction coupling-exciting the neuron causes muscle to contract

syncytium

coordination of tissue

H zone

lighter area within middle of A band where thin filaments do not reach

ventricles

lower chambers which pump blood from heart (right goes to the lungs, left goes to the aorta and ultimately the body)

A band

made up of thick filaments along with portions of thin filaments that overlap on both ends of thick filaments

how to increase the force of a muscle contraction

recruitment and summation

tropomyosin and troponin

regulatory proteins bound to actin

diastole

relaxation and filling of ventricles

systolic BP (SBP)

result of heart ejection into arteries and the lack of compliance of those vessels

abnormalities in rhythm

rhythm - regularity or spacing of ECG waves arrhythmia - variation from normal rhythm and sequence of excitation of the heart myopathies - damage to the heart muscle myocardial ischemia - inadequate delivery of oxygenated blood to heart tissue acute myocardial infarction (heart attack) - occurs when blood vessel supplying area of heart becomes blocked or ruptured, necrosis (death of heart muscle)

abnormalities in rate

tachycardia - rapid heart rate of more than 100 bpm bradycardia - slow heart rate of fewer than 60 bpm

blood

transports medium within which materials being transported are dissolved or suspended

isovolumetric contraction

valves closed, isometric contraction of cardiac muscle (no change in ventricular volume)

isovolumetric relaxation

valves closed, isometric relaxation of cardiac muscle (no change in ventricular volume)

pathway of blood

venae cavae --> right atrium --> right AV valve --> right ventricle --> pulmonary semilunar valve --> pulmonary artery --> capillary beds of lungs --> pulmonary veins --> left atrium --> left Av valve --> left ventricle --> aortic semilunar valves --> aorta --> body

veins

vessels that return blood from tissues to the atria

end diastolic volume (EDV)

volume of blood in ventricle at end of diastole

end-systolic volume (ESV)

volume of blood left in ventricle after systole

level of organization for skeletal muscle

whole muscle --> muscle fiber (cell) --> myofibril --> thick and thin filaments --> myosin and actin

thin filaments

actin (protein)

muscle fiber

single skeletal muscle cell

atrioventricular node (AV node)

small bundle of specialized cardiac cells located at base of right atrium near septum

purkinje fibers

small, terminal fibers that extend from bundle of His and spread throughout ventricular myocardium

autorhythmic cells

- do not contract - specialized for initiating and conducting action potentials responsible for contraction of working cells - spontaneously depolarizing so do not have steady resting potential - pacemaker potential - slowly depolarizes until threshold reached --> action potential

blood pressure

- for blood to flow there needs to be a pressure gradient - the heart spends twice as much time in diastole as systole

cardiac muscle

- found only in the heart - striated - cells interconnected by gap junctions - intercalated discs - syncytium - involuntary, innervated by ANS

sarcomere

- functional unit of skeletal muscle - found between two Z lines - 4 regions: A band, H zone, M line, I band

intercalated discs

- gap junctions found here - help interconnect cells and form functional syncytium

events of skeletal muscle contraction

1. Myosin binds and hydrolyzes (breaks it down) ATP into ADP and Phosphorus (P) 2. The myosin head extends and has 'potential energy' stored 3. Depolarization of muscle membrane and travels down T tubules to all parts of muscle 4. voltage gated Ca2+ channels opening 5. Ca2+ rushes into cell from the outside 6. causes Ca2+ from SR released into myocyte cell. 7. Ca2+ binds to troponin 8. Troponin causes tropomyosin to expose the myosin binding site on the actin filament 9. Myosin binds actin forming a 'Crossbridge' between actin and myosin 10. ADP and Phosphate are released from myosin which causes myosin head to "cock" - myosin uses the potential energy it gained from ATP breakdown 11. the actin and myosin fibers slide across each other. 12. The muscle fiber shortens as contraction occurs. 13. cross bridge breaks when ATP binds myosin again. 14. This process continues at a number of actin-myosin cross bridge sites along the myofilaments so the muscle uses a tremendous amount of ATP. - As long as calcium ions and ATP are present, this walking continues until the muscle fiber is fully contracted.

what do all 3 muscle types have in common

1. sliding filaments (actin and myosin) 2. response to Ca2+ - protein 'calmodulin' for SM to contract is activated by Ca2+ - SM requires extracellular Ca2+ more than other muscle types for poorly developed sarcoplasmic reticulum and T tubules 3. require ATP

M line

extends vertically down middle of A band within center of H zone