KA.6 Structure & function of heart Flashcards
What is the pathway of blood
*blood from body
* Vena cava
* Right atrium
* Right ventricle
*Lungs
* Pulmonary vein
* Left atrium
* Left ventricle
* Aorta
* Blood to body
What is Atrio-ventricular valves
Prevents backflow of blood from ventricles into atria
What is semi-lunar valves
Prevents backflow of blood at the entrance of arteries leaving the heart (pulmonary artery, aorta) back down into ventricles
when happens when the SL valves open during Systole
allows blood into arteries and close when arterial pressure exceeds ventricular pressure, muscle relaxes (diastole)
what is heart rate
Number of heartbeats per minute
what is stroke volume
Volume of blood expelled by ventricles on contraction
What is cardiac output
Volume of blood pumped out of ventricle per minute
How is cardiac output calculated
Heart rate X Stroke volume
What is Cardiac cycle
Pattern of contraction (systole) (diastole) by heart during one heartbeat
What are the 3 stages of the Cardiac cycle
- Atrial and ventricular diastole (chambers relaxed and filling with blood)
- Atrial systole ( Atria contracts, remaining blood is pushed into ventricles)
- Ventricular systole ( ventricles contract, push out blood through aorta and pulmonary artery)
How long can cardiac cycle last
0.8 seconds, based on heart rate on 75 beats per minute
What is responsible for heart sounds
opening and closing of AV and SL valves, can be heard with a stethoscope
What is Sino-atrial node
contains auto-rhythmic cells
located in wall of right atrium and sets the rate at which cardiac muscle cell contract
what is a Cardiac conducting system (1)
The timing of cardiac cells contracting is controlled by impulses from Sino-atrial node (SAN) spreading through atria causing atrial systole
What is a cardiac conducting system (2)
then travel to Atrioventricular node (AVN) located in centre of heart
What is a cardiac conducting system (3)
Impulses from AVN travel down bundle of conducting fibres in central wall of heart then up through walls of ventricles causing ventricular systole
How do Electrocardiograms work
Electrical activity of heart generates tiny currents that can be picked up by electrodes placed on skin surface
What are the 3 waves of an ECG
P Wave
QRS wave complex
T Wave
What is a P Wave
Electrical impulses spread over atria from SAN
What is a QRS Wave complex
Electrical impulses passing through ventricles
What is a T Wave
Electrical recovery of ventricles near the end of ventricular systole
What does the medulla control
regulate the rate of SAN through antagonistic actions of Autonomic Nervous System
How can the Autonomic Nervous System have antagonistic actions
- Cardio-accelerator centre sends nerve impulses via sympathetic nerves to heart
- Cardio-Inhibitor centre sends information via parasympathetic nerve to heart
- two pathways are antagonistic
How does the sympathetic nervous system control heart rate
sympathetic nerve results in increase in heart rate due to sympathetic accelerator nerves releasing noradrenaline
How does the parasympathetic nervous system control heart rate
Parasympathetic nerve results in a decrease in heart rate due to slowing parasympathetic nerves releasing acetylcholine
How can hormones control heart rate
during exercise, stress, SNS acts on adrenal glands in kidneys, making them release hormone epinephrine into bloodstream, reaching SAN causes increase of heart rate
