VTPP 427: Exam 2

Which way does blood flow in terms of pressure?

High pressure to low pressure

What does the P way represent?

Atrial Contraction

What does the QRS Complex Represent?

Ventricles contract

What does the T wave represent?

Ventricles Relax

What is the physiology during the P wave?

The pressure in the atria becomes greater due to filling/contraction of the atria. Because of that, the AV valve opens, and blood will move to into ventricles until the pressure in the ventricles becomes great enough to shut the AV valve shut.

What is the physiology during the QRS Complex?

Ventricles contract, but initially Isovolumetric contraction occurs. Then once the pressure in the ventricles becomes greater than the pressure in the aorta, semilunar valves will open and blood will move into aortic circulation.

What is the physiology of the T Wave?

Ventricles relax, but initially isovolumetric relaxation occurs. As the ventricles relax more and more, the pressure in the ventricles drop below the pressure in the atria, letting blood flow back into the ventricles.

What is isovolumetric contraction?

When the pressure inside the contracting ventricles are higher than the atria, but lower than the aortic pressure. This causes all valves to be shut, leaving the volume in the ventricle constant for a period of time.

What is isovolumetric contraction?

When the pressure inside the contracting ventricles are lower than the aortic pressure but higher than the atrial pressure. This causes all valves to be shut, leaving the volume in the ventricle constant for a period of time.

What stops the backflow of blood in the chambers of the heart?

The chordae tendinea support the valves from inverting and allowing blood to flow backwards, even if the pressure gradients are set.

What is occurring during systole and what are the 2 phases?

Ventricles are contracting. It begins with isovolumetric contraction, and then ventricular ejection of blood into aortic circulation

What is occurring during diastole and what are the 3 phases?

Ventricles are relaxing. It begins with isovolumetric relaxation, and then ventricular filling. Then atrial contraction finishes ventricular filling.

What is cardiac output and its equation?

The amount of blood pumped by the heart per minute.

CO=HR×SV

What helps increase heart rate?

Sympathetic stimulation activates β₁ receptors on the pacemaker cells. That signaling causes the pacemaker cell to have greater inward positive-ion current, particularly involving the Na⁺ and Ca²⁺ currents, allowing the slope to become steeper (membrane potential is changing more quickly toward threshold)

What helps decrease heart rate?

Parasympathetic stimulation decreases heart rate. That signaling causes the pacemaker cell to have slower inward positive-ion current, particularly involving the Na⁺ and Ca²⁺ currents, decreasing the slope (membrane potential is changing more slowly toward threshold). Increasing potassium permeability also does this by lowering resting membrane potential.

What is venous return (Preload) and how does it affect stroke volume?

Blood from the body returning to the heart. If venous return is low, stroke volume is low. If venous return is high, stroke volume is high.

How does sympathetic stimulation affect stroke volume?

By increasing strength of ventricular contraction. The stronger the contraction, the higher the stroke volume. It does that by increasing calcium influx into the cells.

T/F Sympathetic stimulation can increase both determinants of cardiac output

True

What is afterload and how does it affect stroke volume?

Arterial pressure (Aortic pressure). If afterload is high, LV has to generate more pressure and it becomes harder to eject blood. So less blood is ejected which equals smaller stroke volume.

T/F The left and right ventricles can have different cardiac outputs

False

What is starling’s law?

The law that states that cardiac output will always be the same on both sides of the heart due to regulation

Suppose the right ventricle temporarily pumps a little more blood than the left. That means there will be an increase venous return (preload), so the LV responds by producing a greater stroke volume. Therefore, the left ventricle catches up with the right.

Although venous return and preload are very similar, how are the different?

Venous return = the amount of blood coming back to the heart.

Preload = the amount of ventricular filling/stretch caused by that returning blood.

T/F Preload and force of contraction are directly related. Smaller preload, smaller force of contraction from the ventricle

True

What is ejection fraction?

The percentage of blood that was in the ventricle at the end of diastole that gets ejected during systole. (The amount of blood that is released into circulation)

What the average ejection fraction of a human?

55%

How do you calculate ejection fraction?

EF = SV / EDV x 100

How does increased preload affect ejection fraction?

Increases EF

How does increased afterload affect ejection fraction?

Decreases EF

How does increased contractility affect ejection fraction?

Increases EF

Why does Most coronary blood flow to the ventricular myocardium occurs during diastole and not systole?

When the ventricles contract, the muscles become very compress which ends up compressing coronary vessels within the myocardium. This leads to decreased blood flow.

How does coronary blood flow match myocardial workload?

If our heart is working overtime, there is an increased demand for oxygen. Local signals will cause coronary vessels to dilate which increases coronary blood flow.

What things help increase flow in the coronary arteries?

• Adenosine

• β₂ stimulation

Describe the pathogenesis of coronary artery disease

Damage to the coronary arteries endothelium allows plaque to develop. This allows the arteries to become more narrowed and eventually restrict blood flow. Less oxygen reaches the myocardium because of this which then leads to a myocardial infraction.

What is the difference between blood flow and blood velocity?

Flow is the amount of blood moving through a vessel per unit time (L/min). Velocity is how fast the blood is moving through the vessel (m/s)

What is the formula for flow?

Q = Pressure / Resistance

What happens to flow as pressure increases?

Flow increases

What happens to flow as resistance increases?

Flow decreases

What is the major determinant of resistance in a blood vessel?

Radius of blood vessel

What happens to resistance if the vessels radius shrinks?

Resistance is inversely proportional to the radius to the fourth power. This means smaller vessel radius cause HUGE increase in resistance.

What does a higher viscosity cause on overall blood flow?

Lowers blood flow

What is the physiological purpose of arteries?

They keep the blood moving during diastole. The large arteries recoil during diastole and move the pressure forward because they are elastic.

What is the physiological purpose of arterioles?

They regulate Cardiac Output to the different tissues, and if everything is normal, the organs can choose how much they want to take.

What happens to the arteries during systole and diastole?

• Systole: Arteries stretch

• Diastole: Arteries recoil

What is the equation for Mean Arterial Pressure?

MAP = Cardiac Output x Total Peripheral Resistance

What happens when when Stroke Volume increases?

• Systolic: Increases

• Diastolic: Same

• MAP: Increases

• Pulse pressure: Increase

What happens when when Heart Rate increases?

• Systolic: Increases

• Diastolic: Increases

• MAP: Increases

• Pulse pressure: Same

What is Arterial Compliance?

How easy an artery can stretch

What happens when when Arterial Compliance increases?

• Systolic: Decreases

• Diastolic: Increases

• MAP: Same

• Pulse pressure: Increase

What happens when when Total Peripheral Resistance increases?

• Systolic: Increase

• Diastolic: Increases

• MAP: Increase

• Pulse pressure: Increase

What physically causes vasodilation and what impact does it have on blood flow?

Decreased contraction of circular smooth muscle in the arteriolar wall, which leads to decreased resistance and increased flow through the vessel

What are factors that cause vasodilation in tissues?

• Tissue activity

• Low oxygen / High CO₂

• Low Sympathetic stimulation

• Heat

• Histamine Release

• Increase Nitric Oxide

• Increase Adenosine / Potassium

What physically causes vasoconstriction and what impact does it have on blood flow?

Increased contraction of circular smooth muscle in the arteriolar wall, which leads to increased resistance and decreased flow through the vessel.

What are factors that cause vasoconstriction in tissues?

• Less Tissue Activity

• High Oxygen / Low CO₂

• High sympathetic stimulation

• Cold

• ADH/Angiotensin 2

• 
  

What does Nitric Oxide do to the vascular smooth muscle of a vessel?

Causes vasodilation which increases blood flow

What does Endothelin do to the vascular smooth muscle of a vessel?

Causes vasoconstriction which decreases blood flow

What is myogenic tone control in the ?

The cardiovascular system way of maintain MAP. If arterial pressure increases, so will CO. So to make sure the MAP doesn’t just drastically increase, the smooth muscles within the arterioles will contract and increase resistance to counter the increased arterial pressure. Works vise versa.

What is capillary hydrostatic pressure and what direction does it push fluid?

Pushed fluid into tissues from the capillaries

What is plasma-colloid osmotic pressure and what direction does it push fluid?

Pulls fluid into the capillaries from the interstitial place

What is interstitial-fluid hydrostatic pressure and what direction does it push fluid?

Pushes fluid toward the capillary from the interstitial fluid

What is interstitial-colloid osmotic pressure and what direction does it push fluid?

Pulls fluid into the tissues from the capilaries

What is the new exchange pressure equation and what does the results mean?

(P_c + π_if) - (π_p + P_if)

• positive → ultrafiltration → fluid leaves the capillary

• negative → reabsorption → fluid enters the capillary

What does histamine and albumin do to cause edema?

Albumin is a protein inside of blood plasma that contributes to plasma colloid osmotic pressure. Histamine helps regulate that by increasing capillary permeability, allowing more albumin to escape which will in following, pull more water to the interstitial space. (increases interstitial colloid osmotic pressure (πif)) This will then lead to localized edema.

How does the lymphatic system work?

Basically the body's fluid cleanup/return system. The terminal lymphatics have special overlapping endothelial cells. Think of them like one-way swinging door, anything that gets taken in wont be let out. It will pick up fluids, proteins, and bacteria, and filter them out before they return back to the heart.

How does edema form due to venous obstruction?

Venous obstruction causes blood to back up. This causes an increase in venous/capillary pressure. The increases the plasma oncotic pressure means more fluid will be pushed out into the interstitial space.

How does edema form due to lymphatic obstruction?

The lymphatic system isn’t able to pick up the excess fluid in the interstitial space, causing edema.

How does edema form due to heart failure?

Blood cant be pumped back into circulation. This causes an increase in venous/capillary pressure. The increases the plasma oncotic pressure means more fluid will be pushed out into the interstitial space.

How does edema form due to malnutrition?

Malnutrition results in low blood proteins. This means that more water will go towards the interstitial space and build up.

What happens in the baroreflex response when there is a drastic increase in blood pressure?

• ↑ BP → ↑ stretch of baroreceptors

• ↑ baroreceptor firing → ↑ afferent activity to the CNS

• The medulla receives the information

• ↓ sympathetic activity / ↑ parasympathetic activity

• SA Node quits firing as fast / lowers HR

• Ventricles contractility ↓

• Arterioles/veins dilate

What is the primary cause of hypertension?

There is not a definitive cause to hypertension but there are things that help influence it.

What helps influence hypertension to occur?

• Salt-related factors

• Problems involving the Na⁺/K⁺ pump

• Pressure on the medulla

• Reduced/abnormal NO

• Digitalis-like compounds

What are secondary causes of hypertension?

• Cardiovascular problems

• Renal problems

• Endocrine problems

• Neurogenic problems

What is the primary cause of hypotension?

• Orthostatic hypotension (Associated with change in position)

• Emotional stress

What is hypovolemic shock and what causes it?

Occurs when you have too little blood/fluid volume

• Severe hemorrhage

• Excessive vomiting, diarrhea, urinary losses

What is cardiogenic shock and what causes it?

Occurs when your heart can’t pump enough blood

• Weakened Heart

What is vasogenic shock and what causes it?

Occurs when there is abnormal widespread vasodilation which leads to blood pressure drop

• Septic Shock (Infection based)

• Anaphylactic shock (Allergic Reaction Based)

What is neurogenic shock and what causes it?

Occurs when there is a loss in vascular tone

• Decrease in sympathetic activity

Which forms of shock lower cardiac output?

Hypovolemic and cardiogenic shock

Which forms of shock lower total peripheral resistance?

Vasogenic and Neurogenic shock

How does the positive feedback mechanism that causes decreased tissue prefusion lead to circulatory collapse and death during severe hemorrhage?

Since there is poor perfusion in the tissues, the bodies arterioles and capillary beds begin to constrict. This then leads to a more poor perfusion until even more cells start to die due to increased resistance. Metabolic acidosis sets into the cells and cell hypoxia occurs

How does the positive feedback mechanism that causes decreased venous return lead to circulatory collapse and death during severe hemorrhage?

Since there is less volume returning to the heart, the stroke volume is significantly decreased. This leads to lower and lower cardiac output which leads to worse BP, tissue perfusion, and increased interstitial fluid volume.

How does the positive feedback mechanism that causes decreased blood pressure lead to circulatory collapse and death during severe hemorrhage?

Since there is not as much blood in circulation, blood pressure drops drastically. This leads to decreased coronary prefusion which leads to decreased myocardial function. It also leads to decrease tissue perfusion