topic 4.4 - circulation

Question 1

structure of arteries

Answer 1

• thick walls as they pump blood at high pressures
• elastic fibres
• small lumen

Question 2

function of arteries

Answer 2

• carry blood away from heart to cells in body (mostly oxygenated)
• pulmonary artery is the exception where it carries de-oxygenated blood from the heart to lungs

Question 3

what happens in peripheral arteries

Answer 3

• the muscle fibres in cell wall either relax or contract to change the size of the lumen, controlling the blood flow

Question 4

structure of capillaries

Answer 4

• one cell thick
• thin walls

Question 5

function of capillaries

Answer 5

• their structure allows capillaries to fit between individual cells
• allows rapid diffusion of substances between the blood and the cells
• O2 & other molecules diffuses out of blood and waste substances such as CO2 diffuses in

Question 6

structure of veins

Answer 6

• thin walls
• large lumen
• few elastic fibres

Question 7

function of veins

Answer 7

• carry blood back towards the heart - most carry de-oxygenated blood
• pulmonary veins carry oxygenated blood from lungs to hearts

Question 8

structure of the heart

Answer 8

• four chambers - right and left atrium and ventricle
• four main blood vessels - pulmonary vein, pulmonary artery, vena cava & aorta
• atrioventricular valves - tricuspid/bicuspid
• semi lunar valves - pulmonary/aortic
• coronary arteries
• cardiac muscle

Question 9

function of :
- pulmonary vein
- vena cava (superior & inferior)
- aorta
- pulmonary artery
- cardiac muscle

Answer 9

• pulmonary vein: from lungs to left atrium
• vena cava: inferior deox blood from lower parts of body to heart and superior carries deox blood from upper part of body. Carried to right atrium
• aorta: from left ventricle to body
• pulmonary artery: right ventricle to lungs
• cardiac muscle: thoicker on left hand side becuase high pressure is needed to pump blood to whole body

Question 10

function of atrioventricular valves

Answer 10

prevent the back flow of blood

Question 11

function of pulmonary/aortic valves

Answer 11

separate arteries from ventricles

Question 12

function of coronary arteries

Answer 12

wrapped around the heart to supply blood to cardiac muscle of the heart

Question 13

what is double circulation

Answer 13

• involves two circulatory systems
• systemic circulation carries oxygenated blood from the heart to the cells in the body and carries de oxygenated blood back to the heart
• pulmonary circulation carries de oxygenated blood from heart to lungs where it is oxygenated and carries oxygenated blood back to heart

Question 14

advantages of double circulation

Answer 14

• concentration gradient is maintained as oxygenated & de-oxygenated blood don’t mix
• blood pressure to body tissues is higher
• blood pressure to lungs is lower (avoids damaging capillaries in lungs and increases time for gas exchange)
• organisms can develop larger bodies

Question 15

what is a single circulatory system (fish)

Answer 15

• heart pumps de-oxygenated blood to gills and becomes oxygenated, giving up CO2 at the same time
• blood travels around the rest of the body, giving up O2 to body cells before returning to the heart

Question 16

stages of the cardiac cycle

Answer 16

• atrial systole
• ventricular systole
• cardiac diastole

Question 17

1. atrial systole

Answer 17

• the atria contract
• this causes atrioventricular valves to open
• blood flows into ventricles

Question 18

2. ventricular systole

Answer 18

• contraction of ventricles causes AV valves to close and semi-lunar valves open
• hence blood leaves left ventricles through aorta and right ventricle through pulmonary artery

Question 19

3. cardiac diastole

Answer 19

• atria and ventricles relax
• pressure inside heart chambers decreases
• semi-lunar valves in aorta and pulmonary arteries close; preventing back flow of blood

Question 20

myogenic stimulation of the heart

Answer 20

• the heart triggers its own beat so is said to be myogenic

Question 21

myogenic stimulation of the heart - how?

Answer 21

• wall of right atrium contains SAN (aka pacemaker)
• cells in SAN depolarise (become electrically excited)
• electrical impulse is spread across the atria and atria contracts - atrial systole
• impulses cannot pass directly down to the ventricles
• between atria there is the AVN
• AVN is connected to Purkyne fibres
• AVN detects the electrical impulses passing over the atria
• after a short delay AVN transmits electrical impulses down the Purkyne fibres
• ventricles then contract

Question 22

why can impulses not be directly passed down to the?

Answer 22

• because the ventricles are separated from the atria by a layer of non-conducting tissue

Question 23

Bundle of His

Answer 23

• the Purkyne fibres bundled together are known as the Bundle of His

Question 24

what do the changes in electrical excitation of the heart cause and what are the changes measured with?

Answer 24

• causes the repeating cardiac cycle
• measured in an electrocardiogram (ECG)

Question 25

use of the electrocardiogram

Answer 25

- 12 electrodes and leads are attached to the body - skin is wiped with alcohol to remove any sweat or grease so the electrodes make good contact - as recording is made, info is fed back from each of the electrodes giving 12 views of the heart

Question 26

what is tachycardia & bradychardia

Answer 26

- tachycardia: fast heartbeat, many peaks with short gaps produced on the ECG - bradycardia: slow heartbeat, few peaks with long gaps produced on the ECG

Question 29

3 main functions of blood

Answer 29

- transport hormones - defence - formation of tissue fluid & lymph

Question 30

components of blood

Answer 30

- plasma - erythrocytes - leucocytes - platelets

Question 31

plasma - transporting & function

Answer 31

- transport digested food products from small intestine to parts of body where they are needed - nutrient molecules from storage areas to cells that need them - excretory products from cells to organs - chemical messages from where they are made to cause changes in the body - maintains a steady body temp by transferring heat around the system

Question 32

erythrocytes - function & structure

Answer 32

- contain haemoglobin - transport oxygen from lungs to all cells in the body - biconcave disc shape so large SA:V ratio so O2 diffuses in & out quickly - no nucleus so lots of space for haemoglobin to carry oxygen

Question 33

leucocytes - function & structure

Answer 33

- much larger than erythrocytes - can change their shape - contain a nucleus and cytoplasm - defend body against infection

Question 34

types of granulocytes

Answer 34

- have granules in cytoplasm of cells that take up stain and are pbvious under microscope - neutrophils - eosinophils - basophils

Question 35

type of agranulocytes

Answer 35

- do not have granules to take up stain in cytoplasm - monocytes - lymphocytes

Question 36

neutrophils

Answer 36

- part of non-specific immune system - engulf & digest pathogens by phagocytosis - multi-lobed nuclei - up to 70% of all leucocytes are nuetrophils

Question 37

eosinophils

Answer 37

- part of non-specific immune system - stained red by eosin stain - important against parasites, in allergic reactions & in developing immunity to disease

Question 38

basophils

Answer 38

- part of non- specific immune system - two lobed nucleus - produce histamines involved in inflammation and allergic reactions

Question 39

monocytes

Answer 39

- part of specific immune response - largest leucocyte - can move out of blood into tissues to form macrophages - engulf pathogens by phagocytosis

Question 40

lymphocytes

Answer 40

- small leucocytes with very large nuclei - vitally important in the specific immune response

Question 41

role of platelets in blood clotting

Answer 41

- they form a plug and release clotting factors including thromboplastin - prothrombin changes to thrombin - soluble fibrinogen forms insoluble fibrin to cover the wound

Question 42

what is atherosclerosis

Answer 42

- build up of plaque in the arteries - restricted blood flow