A&P - Chapter 28 (Part 3) Flashcards
What are 4 structures that generate strong impulses?
- SA nodes
- AV nodes
- AV bundle
- bundle of His - Aubendocardial branches
- Purkinje fibres
What is the pacemaker of the heart?
SA node
What does the SA node do?
It initiates impulses/heartbeats and sets its pace
Where is the SA node?
In the wall of the RA near the opening of the superior vena cava
Where is the AV node located?
In the right atrium along the lower part of the interatrial septum
Where is the AV bundle located?
In the septum of the ventricle
Where are the Purkinje fibres located?
In the walls of the ventricles
ECG
Electrocardiogram
Electrocardiogram
The recording of the electrical impulses of the hearts conduction system
What kind of waves/deflections are on a normal ECG? (3)
- P Wave
- QRS complex
- T Wave
P wave
Represents depolarization of the atria
- triggers contraction
QRS complex
Represents depolarization on the ventricles
T wave
Represents re-polarization of the ventricles
- just before relaxation phase
What is not shown on an ECG?
Re-polarization of the aorta
- overshadowing by a large QRS complex
What will change the ECG?
Damaged heart muscles
- CVD = cardiovascular disease
What is each complete heartbeat called?
Cardiac cycle
- regular and rhythmic
What is the average beat per minute?
72
- 0.8sec long
What is each cycle subdivided into? (2)
- Systole
- contraction (lub) - Diastole
- relaxation (dub)
Stroke volume
Amount of blood that one ventricle ejects with each beat
Cardiac output
Volume of blood that flows out of a ventricle per unit of time
- mL/min
What are the 5 phases of the cardiac cycle?
- Atrial systole
- Isovolumetric ventricular contraction
- Ejection
- Isovolumetric ventricular relaxation
- Passive ventricular filing
Atrial systole
Atria contracts
- pressure gradient allows blood to flow into relaxed ventricles
Isovolumnetric ventricular contraction (2)
- Intraventricular pressure begins to increase
- AV vales close
- hearts first sound (lub)
Ejection
SL valves open
- blood leaves the house
Isovolumetric ventricular relaxation (2)
- Ventricles begin to relax
- SL valves close and AV valves open
- second heart sound (dub)
Passive ventricular filling (3)
- Intraventricular pressure drops and intra-artial pressure rises
- AV valves open
- Blood enters in
What makes the sound of a heartbeat?
Heart valves opening and closing
