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25 Cards in this Set

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What are the 6 functions of the heart?

- provides hydrostatic pressure to drive blood through vasculature


- delivers oxygen and nutrients to cells within tissues


- removes metabolic wastes (like urea) and CO2


- removes metabolic heat produced by cells


- distributes hormones throughout body


- transports immune cells around body

What are the 3 layers of tissue of the heart?

1. Mycardium,middle layer. Myo means “muscle”


2. Endocardium,endo = within, inside


3. Epicardium,epi means upon

What are the characteristics of the Endocardium tissue?

- thin, epithelial layer (called endothelium; continuous with endothelium of vasculature (bloodvessels)


- in contact with blood within chambers of the heart, but does not get nutrients or oxygen that way

What are the characteristics of the Mycardium tissue?

- THICK middle layer-comprises most of the heart tissue-CONTRACTILE


– generates muscular tension


– made of cardiac myocytes

What are the characteristics of the Epicardium tissue?

- thin external layer of heart


- a SEROSA


- is the inner layer of the epicardial sac


- consists of a simple, squamous (flat, fried egg-shaped cells) epithelium that secretes a thin mucus


- thin mucus is slippery and allows the outer surface of the heart to slide easily (without friction) against the outer layer of the epicardial sac


- narrow space between epicardium and outer layer of epicardial sac is filled with the thin mucus (called pericardial fluid). The space is called the pericardial cavity.

What is a SEROSA?

an epithelium that secretes a thin, watery mucus-ey fluid

What are the Heart Cell Types and what are their prevalence?

Contractile cells - 99%


Pacemaker cells – 1%


Conductile cells – 1% (may also have dual function as pacemaker cells)


Endocrine cells – secrete atrial natriuretic peptide (ANP) – very small percentage but enough to regulate Na+ excretion by kidneys.

What happens in the secretion of ANP when you eat salty food?

Secretion of ANP: Eat salty food, get Na+ in blood. This makes you thirsty, and you retain water. Consequently, your blood volume increases. Because of this increase in volume, Your blood pressure goes up. The increased blood volume and pressure increases the stretch on the walls of your atria. This stretch stimulates secretion of ANP. ANP makes the kidneys excrete more Na+ into urine. Thus, your body gets rid of the extra sodium. Water follows the Na+ into the urine. Consequently your blood volume decreases

Which Heart Cell doesn't have a RMP?

Pacemaker cells (instead they have a “restless” membrane potential)

Are pacemaker cells contractile or not?

made up of non-contractile cells

Pacemaker cells are autorhythmic. What does autorhythmic mean?

autorhythmic: spontaneously generate APs;trigger APs that get conducted throughout rest of heart

A kind of pacemaker cell:


What is the Sino-Atrial Node?

Sino-Atrial (SA) Node: dominant pacemaker region of heart

A kind of pacemaker cell:


What is the Atrio-Ventricular (AV) Node?

Atrio-Ventricular (AV) Node: action potentials arriving from the SA node force the AV node to fireaction potentials at the same rate as the SA node.

How long is the delay in an Action Potential in going from the AV node to the Bundle of His?

There is a 100 ms delay

What is the Bundle of His?

The bundle of cardiac muscle fibers that


conducts the electrical impulses that regulate


the heartbeat

Now on to Conductile Cells:


What are Concuctile cells specialized for?

Specialized for conducting action potentials from SA node to rest of heart

What are modified muscle cells in the heart?

Modified muscle cells that no longer contract - not neurons.

Conductile Cells are in electrical contact with these modified muscle cells via what pathway?

In electrical contact with contractile cells via GAP JUNCTIONS

How else are Contractile cells (cardiac myocytes) also joined together?

Contractile cells (cardiac myocytes) also joined together via INTERCALATED DISCs and gap junctions

What is the Internodal pathway?

It is a pathway for signals from the SA node to the AV node that passes through the walls of the atria

What is the Interatrial pathway?

Extends from the SA node within the right atrium to the left atrium; spreads excitation so that left and right are exciting at same time.


Remember the DIAGRAM of the heart!!


*Bundle of His also involved

What are Purkinje Fibers and what do they do?

Special fibers that are located in the atrioventricular, or AV, bundle of the heart. Their function is to send nerve impulses to the cells in the ventricles of the heart and cause them to contract and pump blood either to the lungs or the rest of the body.

What is the fibrous partition between atria and ventricles called? What is it's role?

Fibrous partition between atria and ventricles - FIBROUS SKELETON OF THE HEART - this electrically isolates atria from ventricles

What is the Interventricular Septum?

the stout wall separating the lower chambers (the ventricles) of the heart from one another

What ion channels mediate APs in Pacemaker Cells?

VGCCs mediate APs in Pacemaker Cells