KA.6 Structure & function of heart

Question 1

What is the pathway of blood

Answer 1

*blood from body
* Vena cava
* Right atrium
* Right ventricle
*Lungs
* Pulmonary vein
* Left atrium
* Left ventricle
* Aorta
* Blood to body

Question 2

What is Atrio-ventricular valves

Answer 2

Prevents backflow of blood from ventricles into atria

Question 3

What is semi-lunar valves

Answer 3

Prevents backflow of blood at the entrance of arteries leaving the heart (pulmonary artery, aorta) back down into ventricles

Question 4

when happens when the SL valves open during Systole

Answer 4

allows blood into arteries and close when arterial pressure exceeds ventricular pressure, muscle relaxes (diastole)

Question 5

what is heart rate

Answer 5

Number of heartbeats per minute

Question 6

what is stroke volume

Answer 6

Volume of blood expelled by ventricles on contraction

Question 7

What is cardiac output

Answer 7

Volume of blood pumped out of ventricle per minute

Question 8

How is cardiac output calculated

Answer 8

Heart rate X Stroke volume

Question 9

What is Cardiac cycle

Answer 9

Pattern of contraction (systole) (diastole) by heart during one heartbeat

Question 10

What are the 3 stages of the Cardiac cycle

Answer 10

1. Atrial and ventricular diastole (chambers relaxed and filling with blood)
2. Atrial systole ( Atria contracts, remaining blood is pushed into ventricles)
3. Ventricular systole ( ventricles contract, push out blood through aorta and pulmonary artery)

Question 11

How long can cardiac cycle last

Answer 11

0.8 seconds, based on heart rate on 75 beats per minute

Question 12

What is responsible for heart sounds

Answer 12

opening and closing of AV and SL valves, can be heard with a stethoscope

Question 13

What is Sino-atrial node

Answer 13

contains auto-rhythmic cells
located in wall of right atrium and sets the rate at which cardiac muscle cell contract

Question 14

what is a Cardiac conducting system (1)

Answer 14

The timing of cardiac cells contracting is controlled by impulses from Sino-atrial node (SAN) spreading through atria causing atrial systole

Question 15

What is a cardiac conducting system (2)

Answer 15

then travel to Atrioventricular node (AVN) located in centre of heart

Question 16

What is a cardiac conducting system (3)

Answer 16

Impulses from AVN travel down bundle of conducting fibres in central wall of heart then up through walls of ventricles causing ventricular systole

Question 17

How do Electrocardiograms work

Answer 17

Electrical activity of heart generates tiny currents that can be picked up by electrodes placed on skin surface

Question 18

What are the 3 waves of an ECG

Answer 18

P Wave
QRS wave complex
T Wave

Question 19

What is a P Wave

Answer 19

Electrical impulses spread over atria from SAN

Question 20

What is a QRS Wave complex

Answer 20

Electrical impulses passing through ventricles

Question 21

What is a T Wave

Answer 21

Electrical recovery of ventricles near the end of ventricular systole

Question 22

What does the medulla control

Answer 22

regulate the rate of SAN through antagonistic actions of Autonomic Nervous System

Question 23

How can the Autonomic Nervous System have antagonistic actions

Answer 23

1. Cardio-accelerator centre sends nerve impulses via sympathetic nerves to heart
2. Cardio-Inhibitor centre sends information via parasympathetic nerve to heart
3. two pathways are antagonistic

Question 24

How does the sympathetic nervous system control heart rate

Answer 24

sympathetic nerve results in increase in heart rate due to sympathetic accelerator nerves releasing noradrenaline

Question 25

How does the parasympathetic nervous system control heart rate

Answer 25

Parasympathetic nerve results in a decrease in heart rate due to slowing parasympathetic nerves releasing acetylcholine

Question 26

How can hormones control heart rate

Answer 26

during exercise, stress, SNS acts on adrenal glands in kidneys, making them release hormone epinephrine into bloodstream, reaching SAN causes increase of heart rate