THE HEART Flashcards Preview

3 ADAPTIONS FOR TRANSPORT IN ANIMALS > THE HEART > Flashcards

Flashcards in THE HEART Deck (25):
1

What is the heart?

- 2 pumps to circulate blood around the body

2

label the heart

labled drawing of the heart

3

myogenic

it can contract and relax rhythmically of their own accord

4

systole

heart contracting

5

distole

heart relaxes

6

Atrial systole (4)

- atrium walls contract
- blood pressure in atria increases
- pushes blood through bi & tri cuspid valves to ventricles
- ventricles are relaxed

7

Ventricular systole (4)

- ventricle walls contract
- blood pressure in ventricle increases
- forces blood up through semi-lunar valves into pulmonary artery and aorta
- blood cannot flow back bc tri & bi valves are closed by rise in pressure

8

Distole (5)

- ventricles relax
- volume of ventricles increases
- ventricle pressure falls
- semi-lunar valves shut to prevent backflow
- atria relax during systole so cycle can begin again with blood from vena cava and pulmonary veins

9

flow of blood through the left side of the heart (7)

- left atrium relaxes and receives oxygenated blood from pulmonary vein
- when full, pressure forces bi/tricuspid valve open
- relaxation of left ventricle drew blood from left atrium
- left atrium contracts pushing remaining blood into left ventricle through the valve
- left atrium relaxed and bicuspid valve closed left ventricle contracts
- strong muscle exerts high pressure
- pressure pushes blood out of heart through semi-lunar valves to aorta and closes bicuspid, preventing backflow

10

heartbeat (2)

- a complete contraction and relaxation of the entire heart
- atria contract at the same time, followed by the ventricles

11

what happens when a chamber of the heart relaxes/contracts (2)

- empties when contracted
- fills when relaxed

12

why is left ventricle thicker than the right? (2)

- the left has to pump blood around the entire body
- the right only has to pump the short distance to the fragile lungs

13

What are valves for?

- prevent backflow

14

when do valves open and shut in the cardiac cycle

diagram

15

sino-atrial node (3)

- cluster of cardiac cells
- acts as a pacemaker
- located in the right atrium

16

how electrical stimulation of the heart works? (7)

- electric stimulation occurs at SAN and spreads of atria causing contraction
- ventricles insulated by a thin layer of connective tissue
- so charge spreads to AVN (atrio-ventricular node)
- AVN delays impulse until atria has finished contracting
- AVN passes excitation down nerves of the bundle of His, left and right to the apex of the heart
- excitation travels through the purkinje fibres in the ventricle walls
- ventricles contract simultaneously, from the apex up

17

ECG

- electrocardiogram, voltage changes produced by heart

18

diagram explain points P, PR, QRS, T, TP (5)

- P wave shows voltage generated by SAN
- PR interval is time taken for excitation to spread from AVN to ventricles
- QRS complex shows depolarisation/contraction of the ventricles (more muscle, bigger wave)
- T is repolarisation of ventricular muscles
- TP/isoelectric line is the separating the two cycles

19

heart issues shown by ECG (4)

- Atrial fibrillation = rapid heart rate/ no P wave
- Post-heart attack = wide QRS complex
- Enlarged ventricle walls = QRS with greater voltage
- Insufficient blood supply = ST height change - could be blocked arteries

20

heart rate calculation

60/ distance between isoelectric lines = heart rate

21

pressure changes in blood vessels (7)

- highest in aorta/large arteries - rises and falls with ventricular contraction
- friction between blood and vessel causes progressive drop, also depends on whether dilated or constricted
- extensive capillary beds reduce bp as fluid leaks to surrounding tissues
- distance from the heart increases as bp lowers
- veins are not effected by ventricles so low bp
- veins have a large lumen, so blood flows faster than in capillaries
- blood is not returned to the heart rhythmically, but by massaging effect of surrounding tissues

22

Blood

45% cells in 55% plasma

23

Why are blood cells red?

- Red because pigment haemoglobin

24

Why are rbc unusual? (2)

- biconcave discs - thin middle reduces diffusion distance
- no nucleus - so more room for haemoglobin

25

Plasma (4)

- pale yellow liquid
- 90% water
- contains biological molecules, waste, hormones and proteins
- distributes heat