Lecture 10 (Heart physiology) Flashcards
What is the main role of the cardiovascular system?
The vital role of the cardiovascular system in maintaining homeostasis depends on the continuous and controlled movement of blood through capillaries.
Numerous control mechanisms help regulate and integrate the diverse functions and component parts of the cardiovascular system to supply blood in response to specific body area needs.
Define Hemodynamics
Collection of mechanisms that influence the dynamic (active and changing) circulation of blood.
What are the 2 functions of circulation control mechanisms?
- Maintain circulation
- Vary volume and distribution of the blood circulated
Explain the difference between Pulmonary circuit and Systemic circuit
Pulmonary circuit: Takes blood to and from the lungs
Systemic circuit: Vessels transport blood to and from body tissues
Explain the difference between Atria and Ventricles
Atria: Receive blood from the pulmonary and systemic circuits
Ventricules: The pumping chambers of the heart
What is a cardiac cycle consisted of?
A contraction (systole)
A relaxation (diastole)
What are the 2 phases of any chamber of the heart? Explain
1) Systole: During systole or contraction, the chamber contracts and pushes blood into an adjacent chamber or into an artery
2) Diastole: During diastole the chamber fills with blood and prepares for the next contraction
What are the 5 phases of a cardiac cycle?
- Atrial systole
- Isovolumetric ventricular contraction
- Ventricular Ejection
- Isovolumetric ventricular relaxation
- Passive ventricular filling
What happens during Atrial Systole?
During atrial systole, atria contract completely filling the relaxed ventricles with blood.
Atrial systole ends and atrial diastole begins and continues until the start of the next cycle.
What happens during Isovolumetric Ventricular Contraction?
Occurs between the start of the ventricular systole and the opening of the SL valves.
Ventricular volume remains constant as the pressure increases rapidly.
Ventricular contraction pushes AV valves closed but does not create enough pressure to open SL valves
What happens during Ventricular Ejection?
SL valves open and blood is ejected from the heart when the pressure gradient in the ventricules exceeds the pressure in the pulmonary artery and aorta
What happens during Isovolumetric Ventricular Relaxation?
Period that occurs between closure of the SL valves and opening of the valves. A dramatic fall in intraventricular pressure but no change in volume.
Blood flows into the relaxed atria but the AV valves remain closed.
What happens during Passive Ventricular Filling?
Continuous return of venous blood from vena cava & pulmonary veins increases pressure within each atria. Blood rushes into relaxed ventricles. Rush of blood followed by a slow & continuous stream of blood. Builds pressure & volume within the ventricles.
What happens when the heart rate increases?
All the phases of the cardiac cycle are shortened
Explain the first and second sound when you listen to a heart
1st beep: Systolic sound, caused largely by the contraction of ventricules and by the closing of the atrioventricular valves. Short and sharp
2nd dupp: Caused by the vibration of closing semilunar valves
Explain the role of intercalated disks
Electrical connectors that join muscle fibers into a single unit that can conduct an impulse through the entire wall of a heart chamber without stopping.
The myocardium behaves as a single coordinated unit or functional synctium.
Name the 5 major structures of the conduction system of the heart
- Sinoatrial node
- Atrioventricular node
- Atrioventricular bundle
- Bundle branches
- Subendocardial branches
Locate and describe the SA node
Location: right atrial wall, inferior to the entrance of the superior vena cava
Initiate heartbeat and sets its pace
Impulses from the SA node (pacemaker) spread through the atria (via gap junctions)
Locate and describe the Subendocardial branches (Purkinje fibers)
Signals spread throughout ventricles.
Depolarize the contractile cells of both ventricles
Ventricular contraction almost immediately follows the ventricular depolarization wave
Locate and describe the Bundle branches
Signals from the bundle branches conducted through the ventricular walls.
By specialized muscle fibers (Purkinje fibers)
Locate and describe the AV bundle
Found in the superior part of the interventricular septum
Connects the atria to the ventricles
Splits into 2 bundle branches (conduct the impulses through the interventricular septum)
Locate and describe the AV node
Allows the atria to empty blood before ventricles contract.
AV node is located in the inferior portion of the interatrial septum above the tricuspid valve.
