Module 1:Cardiac Anatomy & Physiology Flashcards

Question

Cardiac Output

Answer 1

= Volume of blood pumped by heart in 1 min = HR (no. of heart beats per min) x Stroke volume (Amount of blood ejected from the LV during a heartbeat (L)) Normal cardiac output in adult @ rest = 4-6 L per min

Answer 2

- Preload (STRETCH) Amount of stretch on the ventricle at the end of diastole. Amount of tension in the ventricle just before ventricle contraction. The stretching of the ventricle occurs from the total amount of blood that enters or fills the ventricle. The more blood that enters the ventricle, the greater this stretch, or preload, will be. Franklin-Stirling law of heart = Direct relationship between preload and stroke volume – the amount of blood ejected from the heart in a single contraction. The greater the volume of blood that fills the ventricle during diastole, the more the myocardium is stretched, and the greater the preload. - Afterload (RESISTANCE) Pressure in the systemic arteries is relatively high to enable blood circulation throughout the body. The left ventricle works against this arterial pressure when ejecting blood into the systemic circuit. Afterload can be thought of as the force that resists this ejection of blood. That means that an increase in afterload corresponds to a decrease in stroke volume. - Contractility (FORCE) Ability of the myocardium to contract and relax. An increase in contractility leads to an increase in stroke volume independently of preload and afterload. Contractility is controlled by the forces generated by myofibrils—the strings of protein within the cardiac muscle that contract when stimulated. Efficient relaxation of these muscle fibers results in a longer diastolic filling time and less resistance to filling. The contractile state of the myocardium is expressed clinically as the ejection fraction, which is the ratio of stroke volume to end-diastolic volume. Each ventricle normally ejects about 65% of its volume per stroke, although this amount varies with changes in metabolic need.

Answer 3

1. Ventricular systole 2. Ventricular diastole In order to create sufficient cardiac output, the atria on top is electrically activated first, which will produce atrial mechanical contractions. Next, the ventricles experience the electrical activation, resulting in a mechanical contraction that causes systole, a phase of contraction that drives blood flow out of the heart.

Answer 4

Occurs when electrically charged ions travel in and out of cardiac cells. State of contraction.

Answer 5

Cardiac cells in a state of relaxation.

Answer 6

Ability of cardiac cells to contract/ depolarise spontaneously without external influence.

Answer 7

Describes specifically how the energy within each cell is generated and used > heart contraction

Answer 8

- 5 phases ( 0-4) ``` Phase 0: Rapid upstroke Depolarisation/contraction phase Phase 1: Early rapid depolarisation Phase 2: Plateau phase Phase 3: Repolarisation Phase 4: Resting phase ```

Answer 9

During a cardiac cycle, once an action potential has begun there is a period of time in which a new action potential cannot be initiated. Occurs in Phases 0, 1, 2, and early Phase 3. During the ERP, depolarization cannot be initiated no matter how strong the impulse, because it follows the initial depolarization too closely. No matter how much the cell is stimulated during these phases, it will not depolarize. Think of flushing a toilet. Right after you flush a toilet and the water goes down, if you attempt to flush again too soon, the toilet won't flush because there is not enough water in the tank. This is analogous to the Effective Refractory Period. Without the limits ERP places on depolarization, the heart would beat so rapidly it would be unable to fill and eject blood efficiently.

Answer 10

Period following the effective or Absolute Refractory Period, during which a cardiac cell can be stimulated to depolarize, but only by a stimulus or impulse that is stronger than what is normally required for depolarization. Again, think of the toilet analogy. If you wait a bit after flushing, there will be enough water in the tank to flush again, even though the toilet may only be half way through the filling process after the last flush. This is analogous to the Relative Refractory Period. The impulse occurring during RRP is responding to high intensity stimuli, and so typically conducts more slowly than normal, and with aberrancy. This is very important to know, because we don't want to pace or stimulate the heart during this vulnerable period, potentially causing arrhythmias. Serious, life-threatening rhythm disorders can arise if a depolarization occurs within certain areas of the RRP.

Answer 11

The cardiac cells that polarize the fastest will drive the heart rate. The SA node is the fastest. The faster rate of the SA node activates the depolarization mechanism in other cells. Consequently, the impulse formation abilities of other cells are suppressed and not used. If the SA node fails to fire, the AV node generally takes the lead, beating at a rate of 40 to 60 beats per minute. If the AV node also fails to fire, the ventricular cells then have the ability to take over the rhythm, beating at a much slower rate of 20 to 40 beats per minute. This is often referred to as the "escape rhythm."

Answer 12

This group of cardiac cells sets the pace or rate, the heart will beat by sending out depolarization waves throughout the heart. When a heart cell depolarizes, all heart cells around it follow and depolarize as well, like a chain of dominos falling after the first domino falls. Other cardiac cells with slower intrinsic automaticity never have a chance to depolarize on their own because this depolarization wave causes the subsequent cells to contract before the cells' intrinsic rate kicks in. They were, in effect, "suppressed" or prevented from depolarizing on their own. cardiac cells are intimately connected to their neighbors, and when a cardiac cell depolarizes in the heart it creates an action potential. That action potential imposes a depolarization of its neighboring cells, causing a domino effect, or wavefront of depolarization.

Answer 13

- Fast pathway resulting in rapid depolarization The conduction system is a system of specialized cardiac tissue that controls the heart's activity. It controls the speed and rhythm of heart contractions using: Automaticity, the ability of conduction fibers to spontaneously depolarize, Conductivity, the ability of cardiac cells to rapidly conduct the electrical impulse. This electrical control system ensures that the heart keeps pumping, and it adjusts its pumping rate to meet the body's needs during different activities, for example, sleeping, or intense physical effort.

Answer 14

Cell-to-cell pathway- slow route

Answer 15

Is located in the upper right atrium Is known as the heart's natural pacemaker, and Produces resting rates between 60 to 100 beats per minute SA node's rate of automaticity is normally faster than other parts of the heart, and dictates the rate at which the heart beats = "sinus rate." The SA Node is a cluster of cells that generates electrical impulses on its own at a rate needed to pump sufficient blood to the body. An electrical impulse proceeds outward from the SA node > a depolarization wave and atrial contraction. Once a cardiac cell depolarizes, the electrical change in potential causes the cells around it to depolarize, causing a chain-like effect, and all cardiac cells in the atria will then depolarize.

Answer 16

Located between the atrium and the ventricles in the interatrial septum close to the tricuspid valve. The AV node receives the impulse from the SA node. Conduction is slow, allowing enough fill time for the ventricles prior to ventricular contraction. If the SA node fails to deliver an impulse to the AV node, the AV junctional tissue will deliver an impulse to the bundle of His at rates between 40 to 60 beats per minute.

Answer 17

Begins conduction to ventricles | AV junctional tissue 40-60 bpm

Answer 18

The bundle branches + the Purkinje fibers (interlacing fibres of modified cardiac muscle) The Purkinje Network distributes the electrical impulse to the cardiac muscle, allowing for depolarization, or contraction, of the ventricle. It can deliver impulses at rates between 20 to 40 beats per minute; this is known as an "escape" rhythm. There are two bundle branches—right and left. The left bundle further divides into two fascicles—Anterior and Posterior—probably because of the greater muscle mass of the left ventricle.

Answer 19

- Impulse Formation at the SA Node - Depolarization of the Left and Right Atrium - Delay at the AV Node The AV node slows impulse conduction, which allows time for the AV valves to open, and the ventricles to passively fill with blood. The slowing of the impulse also provides time near the end of ventricular filling for the atria to contract, so blood can actively be pumped from the atria to the ventricles to complete ventricular filling. This portion of ventricular filling is called the "atrial kick" and accounts for 30% of ventricular filling. Complete ventricular filling is very important in providing the appropriate cardiac output for the patient. - Conduction at The Bundle Branches - Conduction Through the Purkinje Fibers - The Mechanical Contraction of the Ventricle, or Systole - The Mechanical Relaxation of the Ventricle, or Diastole

Answer 20

SA node > AV node (slow conduction) > Bundle of His (front of His-Purkinje network) > Purkinje network > cardiac muscle for depolarisation

Module 1:Cardiac Anatomy & Physiology Flashcards

(44 cards)