1. Higher Human Biology Subtopic 14 The Heart
Physiology and Health
Higher Human Biology
Subtopic 14
The Heart

2. Learning Intentions To discuss the structure of the heart
To calculate cardiac output
To describe the nervous control of the heart
To describe how to measure blood pressure

3. blockbusters

4. The Heart

5. Structure of the heart 4 chambers Right and left atria
Right and left ventricle
Valves
Atrioventricular valves (tricuspid and bicuspid)
Semilunar valves
The valves prevent backflow

6. Right semi-lunar valve
Left atrio-ventricular valve
Right atrio-ventricular valve
Left semi-lunar valve

7. Right AV valve
Left AV valve

9. Calculating Cardiac Output
Heart Rate (HR)
Number of beats per minute
Stroke Volume (SV)
Volume of blood expelled by each ventricle when contracting
Cardiac Output (CO)
Volume of blood pumped out of a ventricle per minute

10. Calculating Cardiac Output
Heart rate
(bpm)
CO =
HR × SV
Cardiac output
(litres)
Stroke volume
(ml / min)

11. What is the CO of this individual? CO = 72 x 70 = 5040 ml/min
a) At rest: HR = 72bpm
SV = 70ml
What is the CO of this individual?
CO = 72 x 70
= 5040 ml/min
= 5 litres/min
b) During exercise: HR = 200bpm
SV = 150ml
CO = 200 x 150
= ml/min
= 30 litres/min

12. Factors Affecting Cardiac Output
CO can very depending on level of exercise and level of fitness
More intense exercise = higher cardiac output
Increased physical fitness level improves cardiac output

14. Cardiac cycle Systole – contraction Diastole – relaxation
The atria contract first – 0.1s
Then the ventricles contract –0.3s
Then the heart rests – diastole - 0.4s

15. Cardiac Cycle - 3 stages ATRIAL SYSTOLE
VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE
VENTRICULAR DIASTOLE

16. ATRIAL SYSTOLE 2 Atria contract simultaneously
Sends blood through open AV Valves into the ventricles
SL valves closed, ventricles fill up
First 0.1 seconds

17. At this point the ventricles are relaxed and in a state of diastole
VENTRICULAR DIASTOLE
At this point the ventricles are relaxed and in a state of diastole

18. VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE
ATRIAL SYSTOLE
VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE
VENTRICULAR DIASTOLE 18

19. VENTRICULAR SYSTOLE AV valves close, ventricles contract
Pressure inside ventricles > arteries
Forces SL valves open and blood leaves heart
Takes 0.3 seconds

20. VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE
ATRIAL SYSTOLE
VENTRICULAR SYSTOLE AND ATRIAL DIASTOLE
VENTRICULAR DIASTOLE 20

21. ATRIAL AND VENTRICULAR DIASTOLE
Blood returns from Vena Cava and Pulmonary Vein
Blood pressure in the atria increases
Begins to force AV valves open, next ATRIAL SYSTOLE begins
Takes 0.4 seconds

22. State of Ventricular Wall
Summary Table
Atrial Systole
Ventricular Systole
State of Atrial Wall
State of Ventricular Wall
State of AV Valves
State of SL Valves
Contracted
Relaxed
Relaxed
Contracted
Open
Closed
Closed
Open

23. Heart Sounds Start of v diastole (closing of SL) Start of v systole
(closing of AV)

24. Conduction of the Heart
Heart beat is regulated by the nervous system and hormones

25. Sino-atrial (SA) node
Atrio-ventricular (AV) node
Bundle of His
Right & left bundle branches
Purkinje fibres

26. The Pacemaker Called the sinoatrial node Found in right atrial wall
Initiates the heartbeat
Exhibits spontaneous excitation
Causes atria to contract

27. The steps in contraction……
Waves from SA node pass across the atria causes contraction
Signal passes to AV node
Down bundle of His
Divides into left and right bundles
Is conducted up through the pirkinje fibres
Ventricles contract (from bottom up)

28. Nervous Control
The heart is controlled by the autonomic nervous system.
There are 2 pathways that are antagonistic to one another (work in opposites).

29. Control Centre CAC - cardioaccelaratory centre
Medulla of the brain contains 2 groups of neurones which control heart rate
CAC - cardioaccelaratory centre
CIC - cardioinhibitory centre
CAC has sympathetic fibres which when stimulated increase heart rate
CIC has parasympathetic fibres that innervate the heart, stimulation of these nerves slow heart rate

30. Control Centre

31. Cardiac accelerator nerves – sympathetic fibres
CAC in medulla
Cardiac accelerator nerves – sympathetic fibres
Noradrenaline released
Innervates SA node/AV node/Myocardium
Increased Heart rate and strength of contraction

32. CIC in medulla
Parasympathetic fibres
Acetylcholine released
This innervates SA node/AV node
Decreased Heart rate and strength of contraction

33. Hormonal Regulation of the Heart
Stress / exercise causes the adrenal glands to produce adrenaline
This travels in the blood to the SA node and causes an increase in HR

34. Electrocardiogram (ECG)
ECG’s measure the electrical activity of the heart
3 waves: P
QRS T

35. Electrocardiogram (ECG)
P wave – electrical excitation over the atria
QRS wave - electrical excitation over the ventricles
T wave – electrical recovery at end of ventricular systole

36. ABNORMAL ECG’S Atrial flutter Rapid contraction of the atria
Atria contract 3 times for every ventricular contraction

37. ABNORMAL ECG Ventricular tachycardia
Ventricles beat rapidly and independently of the atria
SOLUTION
– artificial pacemaker

38. ABNORMAL ECG’S Ventricular fibrillation
Unco-ordinated electrical activity
Pumping cannot take place
Fatal if not corrected
Defibrillation

40. Blood Pressure
Blood pressure is the pressure exerted on the wall of a blood vessel
Measured in mmHg
Highest in large elastic arteries

41. How do we measure BP? Using a sphygmomanometer Systolic pressure
Maximum pressure during ventricular contraction - 120mmHg
Diastolic pressure
Minimum pressure during ventricular relaxation - 80mmHg

42. Pressure decreases as blood flows round the body
Narrow vessels cause friction and resistance that decrease pressure

43. Measuring Blood Pressure

44. Hypertension Hypertension – prolonged elevation of blood pressure
Major risk factor for many diseases including coronary heart disease.

45. Hypertension Factors Overwieght Lack of exercise Fatty diet
High salt diet
Excess alcohol
Stress

46. Learning Intentions To discuss the structure of the heart
To calculate cardiac output
To describe the nervous control of the heart
To describe how to measure blood pressure