Blood and Heart BIOL252

A patient is prescribed a calcium channel blocker to prevent angina (chest pain) by decreasing the demand for oxygen. What is the explanation for this pharmacological effect?

A drug that inhibits the entry of calcium ions into the cytoplasm of cardiac cells decreases the force of myocardial contractility, thereby decreasing the oxygen demand, relieving the chest pain.

- The pressure that the ventricle has to overcome to force open the semilunar valves - Results from blood pressure in aorta

Afterload

Where does the left ventricle pump blood?

Aorta

- Prevents back flow from the aorta into the left ventricle after contraction - Valve between left ventricle and aorta

Aortic semilunar valve

- Cells that initiate and distribute action potentials throughout the heart. - Generate its own AP independent of NS. - Intrinsic source of excitation for cardiac tissue - Have unstable resting/pacemaker potentials

Autorhythmic cells

Asystole is the total absence of ventricular electrical activity. Would defibrillation be effective in this situation?

Defibrillation would not be effective: it interrupts chaotic electrical activity in the heart, and if there is no electrical activity, then there is nothing to interrupt.

- Adhesive junctions that bind one cell to the other forming a tight barrier. But it is not the tightest we can get. These cells start to die because of lack of nutrients.

Desmosomes

Relaxation phase of the cardia cycle

Diastole

T OR F: Cardiac muscle has more mitochondria and depends less on a continual supply of oxygen than does skeletal muscle.

False

- Collection of autorhythmic cells that can generate action potentials faster than any other part of the heart - Pacemaker

SA node

Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?

SA node

The order of impulse conduction in the heart, from beginning to end, is:

SA node, AV node, bundle of His, bundle branches, and Purkinje fibers.

- Amount of blood ejected per heartbeat

Stroke volume

Blood returning form the systemic circuit first enters what part of the heart?

Superior vena cava

Which circuit carries blood from heart to the tissues?

Systemic circuit

Contraction phase of the cardiac cycle

Systole

If the length of the absolute refractory period in cardiac muscle cells was the same as it is for skeletal muscle cells ________.

Tetanic contractions might occur, which would stop the heart's pumping action

T OR F: As pressure in the aorta rises due to atherosclerosis, more ventricular pressure is required to open the aortic valve.

True

The amount of blood returned to the heart by the vein

Venous return

Describe the innervation of cardiomyocytes

cardiomyocytes are connected by desmosomes to allow the electrical signal from one nerve ending to spread throughout many cardiac muscle cells

What is cardiac reserve?

difference between maximum cardiac output and resting cardiac output

What is an example of extrinsic regulation?

emotional excitation results in sympathetic innervation, so norepinephrine is released, which depolarizes membranes of SA nodal cells, and increases the heart rate. greater heart rate increases cardiac output.

Which of the following would increase heart rate?

epinephrine

What effect do adrenal medulla hormones have on heart rate?

epinephrine and norepinephrine depolarize membranes of SA nodal cells and raise the heart rate

Norepinephrine acts on the heart by ________.

causing threshold to be reached more quickly

What is the plateau portion of the action potential on contractile cardiac muscle cells due to?

maintained depolarization caused by an influx of calcium ions competing with potassium flowing out

What is albumin important for?

maintaining optimal osmolarity and fluid balance

What occurs in ventricular fibrillation?

many pacemakers take over, and the ventricles fail to function as pumps, so circulation stops and brain death occurs

How does the action potential of cardiac cells compare to that of skeletal muscle cells?

much longer in cardiac cells

What makes the myocardium an effective muscle for pumping?

myocardium has organized bundles of cardiac muscle fibers swirling diagonally around the heart that generate the strong pumping action of the heart

Are the autorhythmic myocardial cells the first to contract?

no! the contractile cardiomyocytes in the ventricular wall are the first to contract, the autorhythmic cells just propagate the signal causing the contraction

How would the sympathetic nervous system increase contractility?

sympathetic nerves secrete NE, activates adrenal medulla to secrete NE and epinephrine. these stimulate calcium channels to open in cardiac muscle, and an increase of intracellular calcium means more myosin-actin interactions, and thus a stronger contraction

If the vagal nerves to the heart were cut, the result would be that ________.

the heart rate would increase

What does Frank Starling's law say?

the more stretched the resting fibers, the more forceful the contraction

If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid, ________

threshold is reached more quickly and heart rate would increase

T OR F: The left side of the heart is considered the systemic circuit pump.

true

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

ventricular diastole

Which phase of the cardiac cycle is longest?

ventricular diastole

After the bundle branches, where does the signal spread to?

ventricular walls via purkinje fibers, causing ventricular muscle cells to contract

When does most ventricular filling occur?

when all four chambers are in diastole and AV vales are open, so without effort from the heart, blood flows passively through valves into ventricles- accounts for more than 2/3 of ventricular filling ( occurs between T wave once AV valves have opened and P wave when atria contract)

The tricuspid valve is closed ________.

when the ventricle is in systole

What is the nature of acetylcholine's inhibitory effect on heart rate?

- Acetylcholine causes opening of potassium channels in the sinoatrial node thereby hyperpolarizing it

What is accomplished by the delay of action potential transmission through the AV node?

- Allows the atria to start and complete their contraction before the ventricles contract

Define autorhythmic cells and contractile cells of the heart

- Autorhythmic-initiate ap without stimulus, have unstable resting/pacemaker potentials a specialized cardiac muscle fiber that is self-excitable - Contractile muscle fibers respond to depolarization (not from neurons!) and perform the mechanical pumping of the heart.

Why is it important to prevent tetanic contractions in cardiac muscle, but not in skeletal muscle?

- Long refractory period in cardiac muscle ensures a rhythm of contraction and relaxation for cardiac muscle -. In the skeletal muscles, tetanic contractions can occur because AP last very shorty (short spikes, no plateau) compared to muscle cell contraction. Thus, in skeletal muscle, many AP can be generated during one contraction, and the contraction is thus sustained

Fibrillation is abnormal, rapid contractions of different parts of the heart that prevent the heart muscle from contracting as a single unit. Explain why atrial fibrillation does not immediately cause death but ventricular fibrillation does.

- Main pumps to eject blood to the body and the brain are the ventricles, so when atria don't contract properly, active ventricular filling is impaired. however, most ventricular filling is passive so the ventricles still get enough blood to pump out. when ventricles don't contract properly, it doesn't matter how much blood they have, if they can't squeeze it all out, the brain won't get enough blood and will shut down due to lack of oxygen

What does an ECG measure?

- Measures the electrical activity on the body surface - RECORDS Sum of all APs in heart

How do parasympathetic neurons regulate cardiac output?

- Parasympathetic innervation releases acetylcholine, which hyperpolarizes membranes of SA nodal cells and lowers the heart rate. - Heart rate is directly proportional to cardiac output, so decrease in HR= decrease in CO

The heart is subjected to both intrinsic and extrinsic regulation. Give one example of each in describing how cardiac output can be regulated.

- Preload (more stretched=more forceful contraction from more blood; happens during exercise) - Autonomic innervation (parasympathetic system releases ACh, hyperpolarizes membranes of SA, lowers heart rate)

When and how does erythropoietin regulate hematopoiesis?

- Production of RBCs is stimulated by the hormone EPO, which is produced in the kidneys and targets bone marrow. - EPO levels rise when blood oxygen levels fall below normal, thus stimulating RBC.

How is oxygen delivered in the blood?

- RBCs carry oxygen bound protein called hemoglobin. - Hemoglobin consists of 4 polypeptide chains called globins. - Each globin has a non-protein heme group bound to it, a carbon-nitrogen ring with an iron atom in the center - Oxygen molecule binds to each iron; therefore each hemoglobin can carry up to four oxygen

Increased venous return increases the stroke volume in two ways. What are those?

-An increase in the volume or speed of venous return will increase preload and, through the Frank-Starling law of the heart, will increase stroke volume. - EDV (amount of blood in a relaxed ventricle)

What are the major differences between the myocardium and the skeletal muscle and how do these differences contribute to the ability of the heart to function as an effective pump?

-Myocardium is involuntary with gap junctions and skeletal is not because you control movements but heart always has to be working -Action potential and twitch of heart is longer (enough force for heart to push stronger) for myocardium -Longer absolute refractory period so there's enough room and time for ventricles to fill up

Define systole and diastole. When does most ventricular filling occur?

-Systole (contraction of heart muscle) -Diastole (relaxation of heart muscle) - Atrial diastole - Most of ventricular filling occurs prior to atrial contraction as blood passively flows from the pulmonary veins, into the left atrium, then into the left ventricle through the open mitral valve.

What are the three major roles of the plasma proteins?

1. Carries to shuttle molecules through circulation *Many molecules in blood aren't soluble 2. Keep water in the bloodstream (contribute to osmotic pressure) 3. Role in clotting (fibrinogen, clotting factors) *To make sure blood doesn't leave blood vessel

Which of the following is not part of the conduction system of the heart? AV valve SA node AV node bundle of His

AV Valve

Where does the impulse go after the AV node?

AV bundle and branches

- Slows down impulses so that the atria can contract to fill the adjacent ventricles with blood - Cluster of autorhythmic cells in the interatrial septum, acts as the gateway for all electrical signals headed for the ventricle, delays the signal allowing ventricles to fill

AV node

- Prevents blood in arteries to spill back into the ventricles - valves between atria and ventricles - Right side: tricuspid valve - Left side: Bicuspid valve

AV valves

Increased pressure in the ventricles would close what valve(s)?

AV valves only

What happens if the papillary muscles fail to contract?

AV vavles would not be able to close

- Amount of blood ejected from the left ventricle into the aorta in ONE MINUTE

Cardiac output

What does contractions of the papillary muscles accomplish?

Closes the AV valves, pulls the chordae tendinae

- Respond to depolarization (not from neurons!) and perform the mechanical pumping of the heart. - Cardiomyocytes that contract in the heart wall upon receiving stimulus

Contractile cells

-AMOUNT of blood in a fully relaxed ventricle (120 ml)

EDV

- Amount of blood left in the ventricle after contraction (50 ml)

ESV

- Hormone that stimulates the production of red blood cells, produced in the kidneys and liver and targets bone marrow, levels rise when blood oxygen falls below normal

Erythropoietin

- Gets converted into fibrin, which traps blood cells and platelets - one of the major categories of plasma proteins, soluble precursor of fibrin, a stick protein that forms the framework of a blood clot

Fibrinogen

What is an example of intrinsic regulation?

Frank-Starling mechanism- if you increase the amount of tension of the ventricular muscle before it contracts (preload), the contraction will be more forceful, and you will have greater stroke volume, and thus greater cardiac output

- Enable the heart muscle cells to contract in unison - Action potentials generated by the autorhythmic cells spread to the contractile cells through _____________. - Allow ions to flow from one cell directly into the cytoplasm of the next, thus enabling electrical excitation to spread rapidly from cell to cell

Gap junctions

- Number of heartbeats per minute

Heart rate

- Blood cell formation - production of formed elements in the bone marrow

Hematopoiesis

- Composed of 4 globins bound to heme, each heme bears an atom of iron, which binds on oxygen, carries oxygen in the blood

Hemoglobin

How does arterial pressure affect stroke volume?

Increased arterial pressure --> increased afterload --> decreased blood volume ejected into artery --> increased ESV --> decreased SV * ESV = amount of blood left in the ventricle after contraction

Where is the biscuspid valves located

Left atrium

A 55-year-old male was admitted to the hospital with heart failure. He complains of increasing shortness of breath on exertion, and of needing to sleep on three pillows at night. On physical assessment, the nurse determines that his ankles and feet are very swollen. Which of these symptoms either reflect left-sided and/or right-sided heart failure?

Left side failure results in shortness of breath. Right side failure results in edema in the extremities

An artificial device for stimulating the heart muscle and regulating its contractions.

Pacemaker

- Attach to the cusps of the atrioventricular valves (also known as the mitral and tricuspid valves) via the chordae tendineae - Contract to prevent inversion or prolapse of these valves on systole (or ventricular contraction).

Papillary muscles

- The amount of TENSION of the ventricular muscle before it contracts - Volume of blood in the ventricles at the end of diastole. *EDV - Don't want to have a lot

Preload

The papillary muscles function to __________.

Prevent the AV valves from reversing into the atria

Which circuit carries blood from lungs to the heart?

Pulmonary circuit

Where does the right ventricle pump blood?

Pulmonary semi-lunar valve

Prevents blood from the pulmonary artery backflowing into the right ventricle after the ventricles contract valve between right ventricle and pulmonary trunk

Pulmonary semilunar valve

What blood vessel brings oxygenated blood to the heart?

Pulmonary veins

What blood vessels bring de-oxygenated blood from systemic circulation?

Pulmonary veins

Starling's Law of the heart

The more stretched the resting fibers, the more forceful the contraction

A patient was admitted to the hospital with chest pains. On admission, his pulse was 110 and blood pressure was 96/64. According to his history, his normal pulse rate is usually between 80 and 88 and his blood pressure runs from 120/70 to 130/80. Why did these changes in BP and HR occur?

To maintain the same cardiac output, the heart rate would need to increase to compensate for a decreased stroke volume.

Which AV valve is located on the side of the heart that receives blood form the superior vena cava?

Tricuspid

Cardiac muscle cells share similarities with skeletal muscle cells. Which of the following is not a similarity? a. all cardiac muscle cells are innervated by a nerve ending b. calcium ions are stored in the sarcoplasmic reticulum c. cardiac muscle cells contain sarcomeres d. contractile cardiac muscle fibers become depolarized when sodium ions enter the cytoplasm

a. all cardiac muscle cells are innervated by a nerve ending

If communication between the SA node and the AV node becomes blocked which is most certainly affected: a. the ventricles will contract at a slower rate b. afterload will increase c. the atria will contract at a slower rate d. stroke volume will increase e. all of the above

a. the ventricles will contract at a slower rate

Which control system will increase contractility?

activation of sympathetic nervous system will increase contractility of the muscle

In a healthy individual which of the following would be low?

afterload

The plateau portion of the action potential in contractile cardiac muscle cells is due to a. an increased potassium permeability. b. an influx of calcium ions. c. an influx of sodium ions. d. exit of calcium ions from the sarcoplasmic reticulum

b. an influx of calcium ions.

What causes afterload?

blood (arterial) pressure in the aorta/how strongly the backflow pushes the valves

According to Starling's Law of the heart, cardiac output is directly related to: a. the size of the ventricles b. the heart rate c. amount of blood returning to the heart d. end-systolic volume (amount of blood left in ventricle after contraction) e. cardiac reserve

c. amount of blood returning to the heart *Cardiac Output: amount of blood ejected from the left ventricle into the aorta in one minute

Your heart seems to "pound" after you hear a sudden, loud noise. This increased contractility is... a. because you were startled. b. because when a gasp of surprise is emitted, the Frank-Starling law of the heart is evident. c. due to norepinephrine-mediated increases in contractile cardiac cell intracellular calcium promoting enhanced cross-bridge binding. d. because acetylcholine release is inhibited.

c. due to norepinephrine-mediated increases in contractile cardiac cell intracellular calcium promoting enhanced cross-bridge binding.

What is osmolarity?

concentration of particles that cannot pass through the walls of the blood vessels

What is the nature of acetylcholine's inhibitory effect on heart rate? a. acetylcholine induces depolarization in the sinoatrial node b. acetylcholine causes closing of sodium channels in the sinoatrial node c. acetylcholine causes opening of fast calcium channels in contractile cells d. acetylcholine causes opening of potassium channels in the sinoatrial node thereby hyperpolarizing it

d. acetylcholine causes opening of potassium channels in the sinoatrial node thereby hyperpolarizing it

How would a decrease in blood volume affect both stroke volume and cardiac output?

decreased stroke volume and no change in cardiac output

What is fibrinogen important for?

forming blood clots

How are cardiocytes connected?

gap junctions

What is globulin important for?

immunity, and transport

How do cardiac muscles prevent tetanus?

in cardiac muscle, during an action potential the voltage remains elevated for about 200 ms, which produces a prolonged contraction of the myocardium, which prevents the cardiomyocytes from being stimulated again too soon - Tetanus: painful muscle contraction; violent spasm and stiffness of muscle

How can you increase stroke volume?

increase EDV or decrease ESV

How would EDV affect preload?

increase in EDV= increase in preload

How does increased venous return affect cardiac output?

increased venous return --> increased ventricular filling --> increased preload --> increased ventricular stretch --> increased force of contraction --> increased SV --> increased CO

What is important about the AV bundle?

it is the only electrical connection between the atria and ventricles

What is extrinsic regulation?

nervous and hormonal mechanisms of regulation

Isovolumetric contraction ________.

refers to the period during ventricular systole when the ventricles are completely closed chambers

What is intrinsic regulation?

regulation that is contained in the heart

What is the function of desmosomes?

to make sure when one cell contracts, another does not detach