Physiology III - UNIT 1 (Part 3 - Blood Flow, Heart Sounds, & the Cardiac Cycle)

What is one complete contraction & relaxation of all four chambers of the heart called?

Cardiac cycle

What are the 2 main variables that govern fluid (blood) movement?

1) Pressure causes flow and resistance opposes it

2) Pressure gradient (fluid flows form high to low pressure)

NOTE: pressure measured in mmHg

When we give blood pressure (ex: 140/90), the first number is the __________ blood pressure, while the second number is the _______ blood pressure.

1st = Systolic blood pressure (heart cx)

2nd = Diastolic blood pressure (heart rx)

What two factors regulate the flow of fluids through the heart and vessels, the opening and closing of the heart valves, and blood flow through the valves?

Blood pressure & Resistance

What is the equation relating flow to pressure and resistance? If pressure were to increase, what would happen to flow? If resistance were to increase, what would happen to flow?

Flow = change in pressure / resistance

If Pressure INCREASES, Flow INCREASES

-- same reaction

If Resistance INCREASES, Flow DECREASES

-- inverse property

Imagine we have 3 chambers (A-C) and 2 valves (1 & 2), and the blood flows in the direction of A --> C..... ex: A --(1)--> B --(2)--> C

If chamber A represents the left atrium and chamber B represents the left ventricle, name the following structures: Valve 1? Valve 2? Chamber C?

Valve 1 = Mitral valve

Valve 2 = Aortic valve

Chamber C = Aorta

Imagine we have 3 chambers (A-C) and 2 valves (1 & 2), and the blood flows in the direction of A --> C..... ex: A --(1)--> B --(2)--> C

If the pressure in chamber A is greater than the pressure in chamber B, what valve is affected and is it open or closed? If the pressure in chamber B is greater than the pressure in chamber A, what valve is affected and is it open or closed?

A > B = Valve 1 is OPEN

B > A = Valve 1 is CLOSED

Imagine we have 3 chambers (A-C) and 2 valves (1 & 2), and the blood flows in the direction of A --> C..... ex: A --(1)--> B --(2)--> C

If the pressure in chamber C is greater than the pressure in chamber B, what valve is affected and is it open or closed? If the pressure in chamber B is greater than the pressure in chamber C, what valve is affected and is it open or closed?

C > B = Valve 2 is CLOSED

B > C = Valve 2 is OPEN

Imagine we have 3 chambers (A-C) and 2 valves (1 & 2), and the blood flows in the direction of A --> C..... ex: A --(1)--> B --(2)--> C

State the relationship between pressures in chambers A, B, and C that results in both valves being CLOSED?

C pressure > B pressure > A pressure

(BOTH VALVES CLOSED)

What is the relationship between volume (space), pressure, and blood volume?

Volume (space) inversely proportional to Pressure & Blood volume

NOTE: Increased V = Decreased BV & P; Decreased V = Increased BV & P

What is any failure of a valve to prevent reflux (regurgitation), the backward flow of blood?

Valvular insufficiency (incompetence)

What valvular insufficiency is when cusps are stiffened and opening is constricted (narrowing) by scar tissue?

Valvular Stenosis

What is an abnormal hart sound produced by regurgitation of blood through incompetent valves?

Heart Murmur

Do we see stenosis or regurgitation during Systole? Diastole?

Systole (cx) = Stenosis (valve isn't fully opening)

Diastole (rx) = Regurgitation (valve isn't fully closing)

Is a murmur that occurs when blood leaves the heart (systolic murmur) generally innocent or may signal a heart problem? How about one that happens when the heart fills with blood (diastolic murmur)? One that continues throughout the heartbeat (continuous murmur)?

Systolic = Innocent

Diastolic & Continuous = May signal heart problem

What are the 4 conditions that can cause Diastolic (rx) murmurs?

1) Aortic Regurgitation

2) Mitral Stenosis

3) Pulmonic Regurgitation

4) Tricuspid Stenosis

NOTE: ARMS & PaRTS

What are the 5 conditions that can cause Systolic (cx) murmurs?

1) Mitral Regurgitation

2) Aortic Stenosis

3) Tricuspid Regurgitation

4) Pulmonic Stenosis

5) Mitral Prolapse

NOTE: MR. ASs TRaPS MvP

What is an insufficiency in which one or both mitral valve cusps bulge into atrium during ventricular contarction?

Mitral valve prolapse

What is the listening to sounds made by the body?

auscultation

What is the louder and longer "lub" sound that occurs with closure of AV valves, turbulence in the bloodstream, and movements of the heart wall?

First Heart sound (S1)

What is the softer and sharper "dub" sound that occurs with closure of Semilunar valves, turbulence in blood stream, and movements of the heart wall?

Second Heart Sound (S2)

What other heart sound is rarely heard in people over 30 (ventricular gallop) where the mitral valve opens, allowing passive filling of the L ventricle? Where does this occur in relation to S1 & S2?

S3 heart sound

-- AFTER S2

What other heart sound is almost always abnormal (atrial gallop) with a low frequency (bell at apex) sound? Where does this occur in relation to S1 & S2?

S4 heart sound

-- BEFORE S1

What is the difference between Heart Rate & Heart Rhythm

Heart Rate = Number of times heart beats in a minute (number of times it pumps to push blood round the body)

Heart Rhythm = Pattern in which heart beats

What is the volume in the ventricles at the end of filling?

End diastolic volume (EDV)

What is the volume in ventricles at the end of ejection?

End Systolic Volume (ESV)

What is the volume ejected by ventricles? How do you calculate this?

Stroke Volume

(EDV - ESV)

What is the measurement of the % of blood leaving your heart each time it contracts? How do you calculate this?

Ejection Fraction

(SV / EDV x 100)

What is the amount of blood ejected by each ventricle in 1 minute? How do you calculate this?

Cardiac Output

HR x SV

NOTE: Reminder (SV = EDV - ESV); so HR x (EDV - ESV)

If we have an End Diastolic Volume (EDV) of 120 mL, an End Systolic Volume (ESV) of 60 mL, and a Heart Rate (HR) of 75 bpm: Calculate the Stroke Volume (SV), Ejection Fraction, & the Cardiac Output?

Stroke Volume (SV) = EDV - ESV

120 - 60 = 60 mL

Ejection Fraction = SV / EDV x 100

( 60 / 120 ) x 100 = 50%

Cardiac Output = HR x SV

75 x 60 = 4500 mL/min = 4.5 L/min

What is the difference between a person's maximum and resting cardiac output?

Cardiac reserve

- increases with fitness and decreases with disease

T/F: The left ventricle must eject more blood than the right since it pumps blood to the entire body.

FALSE

BOTH ventricles must eject same amount of blood

What occurs during the Ventricular Filling phase of the Cardiac cycle? (3)

1) Ventricular pressure LOW, Volume HIGH (expand)

2) AV valves open

3) Ventricles FILL (3 phases)

The filling of ventricles during the Ventricular Filling phase occurs in what three phases?

1) Rapid ventricular filling (first 1/3)

2) Diastasis: slow filling (second 1/3)

3) Atrial systole: atria contract (final 1/3)

During the Ventricular filling phase of the Cardiac cycle, can you hear any heart sounds? Can you take any measurements? Is a part of the EKG represented during this time? Is a part of the cardiomyocyte action potential represented during this time?

Heart Sound = NONE

Measurements = ESV at BEGINNING of this phase; EDV at END of this phase

EKG = P wave occurs at END of DIASTASIS (2nd phase of ventricles filling)

Cardiomyocyte AP = NONE

What occurs during the Isovolumetric contraction phase of the Cardiac Cycle? (3)

1) Atria repolarize & relax

2) Ventricles Depolarize

3) AV valves close

NOTE: all 4 valves closed; even though ventricles contract, no ejecting of blood because pressure in aorta and pulmonary trunk still greater

What occurs during the Ventricular Ejection phase of the Cardiac Cycle? (3)

1) Ventricular pressure exceeds arterial pressure

2) Semilunar valves open

3) Blood ejected into pulmonary trunk & aorta

During the Isovolumetric contraction phase of the Cardiac cycle, can you hear any heart sounds? Can you take any measurements? Is a part of the EKG represented during this time? Is a part of the cardiomyocyte action potential represented during this time?

Heart Sounds: S1 during AV node closure

Measurements: NONE

EKG: QRS complex when Ventricles Depolarize

Cardiomyocyte AP: NONE

The ejection of blood into the pulmonary trunk & aorta during the ventricular ejection phase of the cardiac cycle occurs in what two step process?

First rapid ejection where blood spurts out of ventricles quickly

Then reduced ejection with slower flow and lower pressure

When does the ST segment of the EKG occur in the Cardiac Cycle?

Overlaps Isovolumetric contraction phase and Ventricular ejection phase since its with ventricular contraction

During the Ventricular ejection phase of the Cardiac cycle, can you hear any heart sounds? Can you take any measurements? Is a part of the EKG represented during this time? Is a part of the cardiomyocyte action potential represented during this time?

Heart Sounds: NONE

Measurements: ESV & Stroke Volume

--NOTE: ESV can be measured right after the T wave of ECG

EKG: T wave LATE in this phase

Cardiomyocyte AP: PLATEAU phase

What occurs during the Isovolumetric Relaxation phase of the Cardiac Cycle? (2)

1) T wave ends & ventricles begin to expand

2) Blood from aorta & pulmonary trunk briefly flow backward to CLOSE semilunar valves

NOTE: all 4 valves closed; semilunar valves closed and AV not yet opened... When AV valves open, ventricular filling begins again and cycle starts over

During the Isovolumetric relaxation phase of the Cardiac Cycle, can you hear any heart sounds? Can you take any measurements? Is a part of the EKG represented during this time? Is a part of the cardiomyocyte action potential represented during this time?

Heart Sounds: S2 (Semilunar valves close)

Measurements: NONE

EKG: T wave ENDS

Cardiomyocyte AP: NONE

During which two phases of the Cardiac Cycle are ALL 4 valves closed?

Isovolumetric contraction & Isovolumetric relaxation

NOTE: there is NEVER a time when all 4 valves are OPEN because this would allow blood to regurgitate and pressure gradients to be lost

In which phases of the Cardiac Cycle is there ventricular systole?

Isovolumetric contraction & Ventricular ejection

NOTE: ventricles begin to contract in isovolumetric phase to build pressure but blood does not move

In which phases of the Cardiac cycle is there Ventricular Diastole?

Isovolumetric relaxation & Ventricular Filling

NOTE: Includes Ventricular filling because wave of depolarization is slowly passing through AV node, giving time for ventricles to fill

In which phases is the Mitral (left AV) valve open? Which phases is it closed?

Ventricular filling --> OPEN

Isovolumetric contraction --> closed

Ventricular ejection --> closed

Isovolumetric relaxation --> closed

In which phases is the aortic (left semilunar) valve open? Which phases is it closed?

Ventricular filling --> closed

Isovolumetric contraction --> closed

Ventricular ejection --> OPEN

Isovolumetric relaxation --> closed

The first heart sound (S1 - lub) occurs during which phase of the cardiac cycle? The second heart sound (S2 - dub)?

S1 = Beginning of Isovolumetric contraction phase

S2 = During isovolumetric relaxation phase

What is congestive heart failure (CHF)?

Failure of either ventricle to eject blood

What is the difference between left & right CHF (Congestive Heart Failure)?

Left CHF: Left ventricle not ejecting same as right, so right ventricular output exceeds left

- Pressure backs up in lungs => pulmonary edema

Right CHF: Right ventricle not ejecting same as left, so left ventricular output exceeds right

- Pressure backs up systemically => systemic or general edema

T/F: Congestive Heart Failure eventually leads to total heart failure

TRUE

What is the surge of pressure produced by the heartbeat that can be felt by palpating a superficial artery?

Pulse

What is it called when the resting heart rate is ABOVE 100 bpm? What are some examples in which this may occur?

Tachycardia

( T = Tall or Too High)

Examples:

Stress, anxiety, drugs, heart disease, fever, loss of blood/damage to myocardium

What is it called when the resting heart rate is BELOW 60 bpm? What are some examples in which this may occur?

Bradycardia

(B = Below)

Examples:

Sleep, low body temperatures, endurance-trained athletes

What are factors that RAISE the heart rate called? What are factors that LOWER the heart rate called?

RAISE = Positive chronotropic agents

LOWER = Negative chronotropic agents

What are 7 examples of Positive chronotropic agents?

1) Sympathetic nervous system

2) Higher brain centers

3) Baroreceptors & Chemoreceptors

4) Nicotine

5) Thyroid hormones

6) Caffeine

7) Hypocalcemia

What are 5 examples of Negative chronotropic agents?

1) Parasympathetic nervous system (vagal tone)

2) Higher brain centers

3) Baroreceptors & Chemoreceptors

4) Hyperkalemia

5) Hypercalcemia

T/F: The autonomic nervous system can initiate heartbeats, and modulate rhythm & force.

FALSE

ANS can modulate rhythm and force but has NO control over initiation of heart beats

Does the sympathetic or parasympathetic pathways cause a cardiostimulatory effect? Which causes a cardioinhibitory effect?

Cardiostimulatory = Sympathetic

Cardioinhibitory = Parasympathetic (vagus)

T/F: Both the parasympathetic and sympathetic pathways control heart rate and contraction force.

FALSE

Sympathetic does both HR and cx

Parasympathetic does ONLY HR

How does the sympathetic pathways allow the heart to depolarize and repolarize faster? (4 steps)

1) Adrenergic neurons release NE & binds to B-adrenergic fibers in heart

2) activates cAMP

3) opens Ca++ channels which accelerates depolarization of SA node

4) cAMP accelerates uptake of Ca++ by SR, influencing cardiomyocyte relaxation quicker

At excessively high heart rates (>180 bpm), diastole becomes too breif for adequate filling, causing stroke volume _________ and cardiac output _______.

Reduction

Reduction

How does the parasympathetic pathway allow the heart rate to slow down? (3 steps)

1) ACh binds Muscarinic receptors

2) K+ channels in nodal cells open, causing K to leave

3) Hyperpolarization & slowing of heart

Without influence from cardiac centers, the heart has an intrinsic firing rate of what? (TQ)

100 bpm

NOTE: w/o sympathetic and parasympathetic, HR will increase, but Contractile strength will STAY THE SAME

What influence keeps the heart rate to 70-80 bpm since intrinsically its rate is 100bpm?

Vagal tone

What electrolyte condition depresses heart contraction strength, but increases heart rate? Why?

Hypocalcemia

-- decreased extracellular Ca+++ so more Ca++ goes OUT of cell

-- Decreased myocardial cx strength but increased HR because it causes SHORT PLATEAUS

What electrolyte condition causes a decrease in heart rate and the rhythm becomes irregular? Why?

Hyperkalemia

-- increased extracellular K so K goes IN cell

-- Reduce myocardial excitability because resting membrane potential more positive (+)

-- Less influx of sodium leads to depolarization taking longer and inhibition of repolarization

-- Slows heart rate & irregular rhythm

What electrolyte condition causes longer contractions (longer plateaus and stronger contractions)? Why?

Hypercalcemia

-- increased extracellular Ca++ so Ca++ moves IN cell

-- Increased strong, prolonged contractions (longer plateaus)

-- Decreases HR

What electrolyte condition causes abnormal rhythm because cells are hyperpolarized and require increased stimulation? Why?

Hypokalemia

-- decreased extracellular K so K moves OUT cell

-- Cardiomyocytes hyperpolarize so takes more to get cells to fire (depol)

-- Requires increased stimulation so fires less frequently, but it is possible that this makes pacemaker cells (SA node) more excitable

-- can lead to a fast depolarization causing an abnormal rhythm too

What are the 3 variables that influence stroke volume?

1) Preload

2) Contractility

3) Afterload

What is the amount of tension in ventricular myocardium immediately before it begins to contract?

Preload

What is Frank-Starling Law of the heart?

Stroke volume is proportional to the end diastolic volume

-- MEANING: Ventricles eject as much blood as they receive

(the more they are stretched, the harder they contract)

What term refers to how hard the myocardium contracts for a given preload?

Contractility

What are the factors that INCREASE contractility called? The factors that DECREASE contractility?

Increase = Positive Inotropic agents

Decrease = Negative inotropic agents

What are 3 examples of Positive inotropic agents?

1) Hypercalcemia

2) Catecholamines and other hormones

3) Medications

What are 2 examples of Negative inotropic agents?

1) Hypocalcemia

2) Hyperkalemia

What does chronotropic refer to? What does inotropic refer to?

Chronotropic = HR

Inotropic = contraction (cx)

What is the sum of all forces opposing ejection of blood from ventricle, or anything that impedes arterial circulation?

Afterload

NOTE: can be increased by conditions such as Lung disease, Cor pulmonale, emphysema, chonic bronchitis, black lung disease, and hypertension

The largest part of afterload is blood pressure where?

Pressure in aorta & pulmonary trunk

-- limits stroke volume because opposes opening of semilunar valves

What condition increases afterload and opposes ventricular ejection?

Hypertension (High blood pressure)

Why is exercise important for the heart?

Makes heart work harder and increases cardiac output

-- Increased muscular activity increases venous return

-- produces ventricular hypertrophy so SV increased and HR slower at rest