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TOWSON / gender, women and sexuality studies / WGSS 222 / the membrane potential at which an action potential will definitely oc

the membrane potential at which an action potential will definitely oc

the membrane potential at which an action potential will definitely oc


School: Towson University
Department: gender, women and sexuality studies
Course: Human Anatomy and Physiology ll
Professor: Christopher oufiero
Term: Spring 2017
Cost: 50
Name: Study Guide2- Anatomy and Physiology II
Description: These are informative notes and will definitely be on our upcoming exam.
Uploaded: 03/26/2017
8 Pages 4 Views 6 Unlocks

Biol 222­ Anatomy and Physiology II ­Study Guide #2 Professor Christopher Oufiero 

what is the function of pulmonary circuit?

Cardiovascular Physiology 

Pulmonary circuit: carries blood to and from the gas exchanged surfaces of the lungs. Systemic circuit: transport blood to and from the rest of the body. 

Each circuit begins and ends at the heart! 

Cardiac muscle cells

Arteries (efferent vessels): carries blood away from the heart

Veins (afferent vessels): carries the blood to the heart

what is the function of Systemic circuit?

Capillaries (exchange vessels): interconnect smallest arteries and the smallest veins  Pericardium: air space­ lining of the pericardial cavity

what carries out blood from the heart?

Parietal pericardium: outer wall If you want to learn more check out your best friend has joined a cult called “the fellowship of feeling.” he had to spend a month in a set of increasingly severe hazing rituals; pay an $8,000 membership fee; and go along to watch older members find homeless people to harass and beat up. yo

Pericardial sac: surrounds the heart

The Heart Wall 

∙ Epicardium: visceral pericardium covers the outer surface of the heart  ∙ Myocardium: forms the atria and ventricles/ contains cardiac muscle  ∙ Endocardium: covers the inner surfaces of the heart 

Flow of blood  

Right atrium (receives blood from the system circuit)    → right ventricle (pumps blood to  the pulmonary circuit)    → left atrium (collects blood from the pulmonary circuit)    → left ventricle  (pumps blood to the systemic circuit)

* when the heart beats, the atria contract then ventricle contract at the same time* The Conducting System 

Heart contracts on its own­ Automaticity

The conducting system: cardiac muscle cells initiates and distributes electrical impulses  Steps of the conducting system: If you want to learn more check out mckenzie krich
If you want to learn more check out the passage of electrons along a series of membrane-bound carrier molecules

1. Pacemaker potential caused by slow leak of Na+ into cells, generates its own action  potential. 

2. The action potential spread through the cardiocytes of the atria causing sinoatrial (SA)  node generates 70­80 impulses per minute; atria contract.

a. The SA contains pacemaker’s cells that establish the heart rate.If you want to learn more check out uva study guide

3. The impulse which is the action potential pausing (100 msec) at the AV node so the  ventricles can fill.

4. The atrioventricular bundle connects the atria to the ventricles.  If you want to learn more check out squaring a binomial univariate

5. The AV bundle branches conduct the impulses through the interventricular septum. 6. The Papillary muscle contract closing the bicuspid and tricuspid valve 7. The purkinje fibers stimulate the contractile cells of both ventricles, starting at the apex  and to the base of the heart. Each pulse is equal to the ventricles contract.

*Bradycardia: heart rate is slower than normal. Tachycardia: heart rate is faster than normal* 

Fibrous skeleton: four dense bands of tough elastic tissues that encircle the valves, the aorta, the base of the pulmonary trunk. The fibrous skeleton electrically insulates the ventricular cells from the atria cells. 

Action Potentials in Cardiomyocytes 

The resting potential of a ventricular cell is – 90 mV. When the membrane hits threshold,  it is ­75 Mv….

1. Rapid depolarization: at threshold, the voltage­gated Na+ channels open and massive  Na+ ions rapidly depolarizes the sarcolemma.  The Na+ gates remain open for  milliseconds. 

2. Plateau: membrane potential reaches +30 Mv, the voltage­gated sodium channels closed  and actively pumps Na+ ions out of the cell. Next, the calcium channels are open slowly  and remain open for a long relatively period. Ca 2+ ions enter the cytosol. The membrane  potential is not near 0 Mv and the Ca2+ channels are closing.  If you want to learn more check out bmore opinionated

3. Repolarization: slow potassium channels open and K+ ions rush out of the cell which  restores the resting potential. 

4. Absolute refractory period: for ventricular muscle cell, it concludes plateau and the initial period of rapid depolarization. 

5. Relative refractory period: sodium channels close but it can open. May initiate another  action potential. 

    Role of Ca 2+  


Calcium concentration increase when there is an action potential that cause a contraction. 20%   of calcium is needed for contraction. The arrival of extracellular calcium triggers the release of  additional calcium from reserves in the sarcoplasmic reticulum. The cardiac muscle is sensitive  to calcium concentration of the extracellular fluid. 

Muscle twitch in the Cardiac Muscle:

∙ The action potential is longer in the cardiac muscle, the calcium ions enters the cell .  the muscle contracts until plateau ends. The absolute refractory period continue  until relaxation begins. 

∙ Summation does not occur and the heart twitch last 250 sec with 300 min  contraction per min.  The heart in tetany could not pump blood. 


* remote measure of heart’s electrical events using electrodes and lead­ can detect conduction  problems. Every time the heart beats, the depolarization wave goes through the atria, pauses at  the AV node, then spreads to the interventricular septum to the apex to the ventricular  myocardium towards the base. 

∙ P wave: atrial depolarization which cause atrial contraction 

∙ PR segment: extends from the end of the p wave to the start of the QRS complex; time  between indicate atrial depolarization and ventricles depolarization 

∙ QRS complex: ventricles depolarize. Since the ventricular muscle is bigger the electrical  signal is stronger. The aria repolarized. 

∙ R wave: atria repolarized. 

∙ ST segment: ventricles are depolarized/ contracting

∙ T wave: ventricles repolarized, may the size be smaller if starvation low cardiac energy  reserves, and or abnormal ion concentration occurs, slows the repolarization ∙ TP: repolarization of the ventricles to the atrial depolarization

∙ PR interval: extends from the start of atrial depolarization (P wave) to the start of the  QRS complex (ventricle depolarization). Depolarization travels from the SA node to the  ventricles, isovolumetric occurs 

∙ QT interval: refractory period, single cycle of ventricles undergoing depolarization and  repolarization; can be lengthened by electrolyte disturbances 

Cardiac Cycle:  

 One heartbeat

 Completed in less than one second

 Blood flows down the pressure gradients

 As volume decreases the pressure increases. Ventricle relaxes  Pressure due expanding and contracting of chambers- during systole  Heart valves help regulate blood flow, their opening and closing  determined by pressure changes  

 Process

o Systole: contraction, chambers pushes blood out to the adjacent  chamber

o Diastole: relaxation, chamber fills with blood and prepare for the  next cardiac cycle

∙ Phases:

o Atrial systole begins: atrial contraction forces a blood to the fill  the ventricles

o Atrial diastole begins and systole ends.

o Ventricle systole begins: ventricles push blood through the  pulmonary circuits and toward the atria (ventricular ejection).  The AV valves closed and semi valves does not open. Second  phase: ventricular pressure increases in the arteries and then the semi-lunar valves open and blood is injected

o Ventricle diastole: ventricles are relaxed and pressure drops.  Semilunar valves close and the blood flows into the relaxed atria. All chambers are relaxed now.

 End-diastolic: ventricle holding the maximum amount of  blood that will be carry out in the cardiac cycle

 Isometric contraction: heart valves are close, volume  

doesn’t change but pressure increases.  

Cardiac output: amount ejected by each ventricle in 1 minute:  Co: heart rate (HR) x stroke volume (SV)

Factors Affecting HR is the autonomic innervation and hormones  Factors affecting SV is end-diastolic and end-systolic volume

Heart does not need nerves to beat- innervated by sympathetic and  parasympathetic  

Vagal tone keep the heart rate lower

Human heart beats 75 beats per min. EDV-SV=ESV

Ejection fraction: % of blood leaving the heart SV/EDV= ejection fraction  Takicardio high heartrate -persistent resting  

∙ Sympathetic fibers increase heart rate by releasing  

nonephreprine – calcium goes in keep slighting depolarizes –  more rapid depolarization  

∙ Reduce repolarization- reach threshold quicker

∙ Cardiac output increase

∙ Epinephrine, thyroid increase HR affecting the SA node

∙ Thyroid hormone stimulates up-regulation

∙ Nicotine: stimulating the sympathetic neurons

∙ Caffeine: inhibit Camp breakdown, prolonging adrenergic effct

∙ Changes in K+ concentration

o Hypokalemia- diffuses out cell becomes hyperpolarizes  Slower hear rate  

∙ Parasympathetic fibers can decrease heart rate- opening potassium  channels – K+ leaving  

∙ Potassium elongated- slow depolarization  

Stroke Volume

Increase in EDV= increase in SV  

Increase in ESV = decrease in SV

EDV proportional to venous return and filling time and proportional to preload and thus SV  

Preload is the degree of stretching in ventricular muscle (heart is stretching)  during diastole

More in and More out – increases in length-tension relationship  (sarcomeres too far apart cant contract because they are  overstretched. / if they close they can contract) (slightly below just  sitting there- minimal stretching  

Increase EDV=increase Preload= increase SV

What things can affect the EDV: increase filling time and increase venous  return (how much blood coming back in)

Increases in contractility and decrease in ESV

Positive ionotropic reduce ESV

Negative ionotropic increase ESV, decrease in contractility  

Afterload( pressure in the aorta, heart overcome that pressure)- increase ,  the increase of ESV, decrease SV

Radius of the blood vessels smaller- vasoconstriction

Blood vessels and Circulation 

Layers of arteries

∙ Tunic intima (inner)

o Within most of the blood 

o Basement membrane and simple squamous

o Elastic fibers in the arteries 

∙ Tunica media(middle)

o The thickest and contain a lot of smooth muscle in the arteries but not in the vein  as much

o Elastic fibers 

∙ Tunica externa (outer layer)

o Consists of loose connective tissue 

The Flow of blood in the Circulatory System

Elastic arteries ( aorta, subclavian) experience a lot of pressure, tunic media have more elastic  fibers →muscle arteries (common carotid, brachial) thick tunic media and a lot of the smooth  muscle to alter rates of blood flow to different tissues and pressure points   → arteriole (small  arteries) and direct the blood flow to capillary beds, and control by nervous system and  endocrine system   → capillary beds: network of vessels, precapillary sphincters can regular blood flow to various beds; controlled by autoregulation   → venules: small veins     → medium sized  veins : have valves →large veins: more smooth muscle

Differences between arteries and veins

∙ Arteries have

o higher pressure 

o  thicker walls

o tunic media have more smooth muscle 

o maintain circular shape 

∙ Veins have 

o Most of the blood

o Thinner walls 

o Higher capacity for blood 

o Contain valves­ unidirectional flow of blood

o Lower pressure

o Shape collapse 

Arterial Sense Organs

∙ Carotid sinuses

o Baroreceptors: sense blood pressure change 

∙ Carotid and Aortic bodies

o Chemoreceptors monitors oxygen, carbon dioxide, and pH of blood 


 Continuous capillary: permeable to gases and lipid soluble substances pass through  Fenestrated capillary: have pores and ready for larger amount substances   Sinusoids: large gaps in the cell and permit proteins through the tissues­ liver, bone  marrow and endocrine 

 permit diffusion of substances with thin walls

Circulatory Routes

∙ Simple 

∙ Portal system

o 2 capillary beds 

∙ Anastomosis

o Venous : one vein directly into another 

o Arterial: one artery into another 

o Arteriovenous: artery to vein, no capillary 

Cardiovascular physiology: mechanisms and factors that influence and regulate blood flow, must maintain adequate blood flow to peripheral tissues and organs. Blood flow in capillaries  determine by pressure and resistance 

Flow: amount of blood moving through an organs or tissue at a given time.  Flow= difference in  pressure between beginning of the vessel and the end/ resistance 

∙ Laminar in the vessels: smooth and straight 

∙ Turbulent: random direction

∙ ∆P: change in pressure, difference in pressure at the entry of the tube and the exit of the  tube 

Perfusion: flow per given volume or mass of a tissue 


∙ Blood pressure produced by heart driving force of blood

∙ Pressure changes through systemic circuit

∙ Systolic : higher number 

∙ Diastolic: lower number on the bottom

∙ Blood pressure: from aorta to the aterioles

o Pulse pressure: systolic pressure­ diastolic pressure 

o Mean arterial pressure: average pressure driving blood forward into tissue  throughout cardiac cycle

 Diastolic + 1/3 pulse pressure

∙ Capillary pressure: arteriole end to venous end of the capillary beds ∙ Venous pressure : drops from 18mmHg to 0 mmHg in the right atrium

Resistance to Flow­ longer the tube resistance increase  

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