Week 3(2) Cardiac Physiology Flashcards
What are the THREE basic components of the circulatory system?
1. Heart
- serves as a pump that established the pressure gradient needed for blood to flow to tissues
2. Blood Vessels
- passagewats through which blood is distributed from heart to all pasts of body and back to heart
3. Blood
-transport medium within which materials being transported are dissolved or suspended.
BASIC HEART ANATOMY
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EXCITATION IN THE HEART (Anatomy)
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Electrophysiology in the heart
How does it work? (Generally)
The heart generates its own electrical activity
The ACTION POTENTIAL originates in teh Sino-Atrial Node (SAN)
It is then conducted through the Atrio-ventricular node, after a delay
It is then carried down into the ventribles by the budles of His.
The SA Node
What does it do?
How does it do it?
generates regular action potentials.
These are CALCIUM action potentials
Each action potential is separated by a period of DIASTOLIC DEPOLARISATION which beings the membrane back to threshold for another AP
What controls the SA node?
The SA Node is innervated by the Parasympathetic and Sympathetic Nervous System
Parasympathetic - releases Ach which acts as muscarinic receptors to slow heart rate
Sympathetic - releases noradrenaline which acts via Beta receptors to increase heart rate.
Contraction of the HEART MUSCLE
How does it work? How does it differ from skeletal muscle?
It is the same as skeletal muscle (sliding filament)
Triggered by a rise in intracellular calcium (same as skeletal muscle)
The calcium comes largely from internal stores (different from skeletal mucle which is ENTIRELY from reserves)
The calcium release is cause by calcium influx INTO the cells (unlike skeletal)
Control of Ventricle Stroke Volume
Sympathetic stimulation = noradrenaline/adrenaline - acts as B receptos
B receptors increase cAMP
cAMP stimulates kinase
kinase phosphorylates calcium channels
calcium influx increases so contraction force increases
What is Frank-Starling law?
The output of the heart has to match the input (that is the 2 sides have to match each other)
What are the different Atrioventricular (AV) valves?
Positioning, role, different types and names
POSITIONING - right and left AV valves are positioned between the atrium and ventricle on the right and left sides
ROLE:- prevent backflow of blood from ventricles into atria during ventricular emptying
Right AV Valve: AKA Tricuspid Valve
Left AV Valve: Bicuspid OR Mitral Valve
Also note controlled by CHORDAE TENDINAE
What are the semilunar valves?
- aortic and pulmonary valves
- lie at juncture where major arteries leave ventricles
- prevented from everything by anatomic structure and positiong of cusps
Where are heart valves NOT located and why?
No valves between atria and veins
Why - artial pressure are usually not much higher than venous pressures
How is the heart nourished?
It gets blood supply from the CORONARY ARTERY
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What are some characteristics of the coronary artery?
*high intrinsic tone
*high extraction at rest
*Sympathetic influence only small
*Flow is reduced during systole.
