Heart - AP and Circulatory system

Neurogenic heart

beat under control of nervous system

Myogenic heart

Contraction initiated within the heart and the nerves going to the heart only regulate the rate of he heart beat

Cardiac muscle cells

branched, connected to one another via intercalated discs that harbor gap

Junction

allow action potentials to spread between the cardiac cells, producing uniform depolarization of the heart muscle. muscle contraction and synchronized heartbeat.

Pacemaker cells

contain a specialized cell membrane that allows Na, K, and Ca, to cross and trigger their electrical impulses. These are located in the SA node.

Cardiac Conduction system

transmits electrical impulses to cause atrial and ventricles contractions. Spreads from the SA node → atria/cardiac muscles→ AV reliefs the Bundle of His→ Purkinje fiber → ventricular heart muscle cells.

What effect does the small diameter of the conducting fibers  on the velocity of the AP?

The small diameter of the conducting fibers decreases the velocity of the action potential (AP) transmission. This slower conduction rate allows for more effective timing of cardiac muscle contractions.

Why do we want a slow AP between the atria to the ventricles?

A slower action potential (AP) between the atria and ventricles ensures sufficient time for the atria to fully contract and empty blood into the ventricles before they begin to contract. DELAY

How is the heart beat generate in the SA node?

Permeability of K decreases, Pf are open with low Pm and close with rising Pm - permeable to Na. Pf close and transient Ca open, allowing Ca in → reaching the threshold. Repolarization occurs with K channels reopening.

Pf - Funny Channels

funney current mixed with sodium potassium current. It has dual activation by voltage and by cyclic nucleotides

ECG (EKG)

Electrocardiogram is a measure of the electrical activity that is measured at the surface of your body.

What is happening at 1?

pacemaker generates a wave of signals to contract

What is happening at 2?

Signal are delayed in the region between the atria and ventricles

What is happening at 3?

AV node cells are stimulated to produce a signal that travels down the bundle of his, alms the purkinje fiber, to the bottom of the heart

What is happening at 4?

Signals spread from the bottom of the heart upward→the ventricles contract

P wave

wave of depolarization that spread from the SA node throughout the atria

QRS

the time in which the impulse in traveling within the AV node and the bundle of His. depolarization of ventricles

PR interval

time betwen the onset of atrial depolarization and the onset of ventricular depolaization

T wave

ventricles repolarize

ST interval

ventricles are COMPLETELY depolarized

QT interval

time for the ventricular depolarizations and repolarization to occur - “ventricular action potential”

Aterioles

deliver blood to capillaries

Capillaries

exchange material with interstitial fluid. Thinnest walls and has NO smooth muscle. Precapillary sphincters controls blood flow through the inside.

Arteries

carry blood away from the heart - oxygenated blood. Has three layers and can constrict and dilate the blood. Regulates the blood flow and pressure of blood that going into the capillaries

Venules

collect blood from capillaries 

Veins

return blood to the heart - deoxygenation blood. They have thin walls and act as a reservoir. Contain one way valves to prevent blood from flowing backwards

Arteriole end

Pressure of blood (hydrostatic pressure) higher than the pressure of the interstitial fluid at the hypertrophic end of the capillary bed → water and small solutes are forced out of the capillaries

Venous end

Hydrostatic pressure is dropped and is pulling fluid back into the blood. Distributes fluids between the flood and extracellular

Starling forces

The forces that regulate the movement of fluid across capillary membranes, including hydrostatic and oncotic pressures - net filration pressure and oncotic pressure.

Net filtration pressure…

is equal to the hydrostatic pressure of the blood in the capillaries - the hydrostatic pressure of the tissue fluid outside the capillaries 

Oncotic pressure

difference between colloid osmotic pressure in the plasma and interstitial fluid

Colloid osmotic pressure

osmostic pressure exerted by plasma proteins such as albumin. Greater in the plasma than in the interstitial fluid

Lymphatic system

collects excess interstitial fluid transports it to lymph ducts that empty into veins. It plays a crucial role in immune function and maintains fluid balance in the body. Acts as filter for immune response.

Tissues and organs in the lymphatic system

lymph nodes, spleen, thymus, tonsils → remove viruses/debris etc and defend the body against infection

Blood moves through veins in response to…

Numeration of smooth muscle in the walls of the veins and skeletal muscles surrounding the veins

Maintaining blood flow and pressure is regulated by…

cardiac output, degree of contribution of arterioles, and total blood volume

Autonomic nervous system and endocrine system…

interact to coordinate the mechinsims of Nitric oxide and Endothelin

Nitric oxide 

is a major inducer of vasodilation

Endothelin

peptide responsible and is a major inducer vasoconstriction

Vessel control

Contains local and central controls that help the body maintain homeostatis

Local control

helps meet the needs of a particular tissue. Will regulate the arteriole diameter

mechanism of regulating arteriole diameter

In low O2, high CO2 → concentrations in tissues dilate arteriole walls to increase the blood flow and diameter

In high O2, low CO2→ concentrations opposite

NO is released by arterial endothelial cells to increase arteriole diameter and blood flow

Central controls

MORE IMPORTANT because they meet the needs of the whole body such as maintaining blood pressure or maintaining the body temperature

Anyone hyperemia

increase in the metabolism of the tissue which makes O2 used faster→ metabolites increase→ arterioles are dilating to achieve more blood flow

Flow Autoregulation

response to a drop in blood pressure; metabolites build up→O2 depleting-.vessel walls are not as stretched→ smooth muscle surrounding the arteriole will contract less strongly → arteriole dilates → flow restores