Circulation

Question 1

Functions of the cardiovascular system

Answer 1

allows the bulk flow of materials:

• gases
• nutrients
• hormones
• waste

Temp regulation
homeostasis
host defence
reproduction

Question 2

how is the CVS regulated

Answer 2

Autonomic nerves and Hormones

Question 3

what is the function of the parallel arrangement of vessels

Answer 3

– Allows independent regulation of blood flow to different organs
- adapts to metabolic demands of the tissues

Question 4

aspects of the microcirculation

Answer 4

– Arterioles, precapillary sphincters, capillaries, venules

Question 5

how much blood passes through your circulation every minute

Answer 5

5 litres

Question 6

normal passage of blood

Answer 6

VC
RA
RV
Pulmonary Trunk 
Pulmonary Arteries 
Lung capillaires 
Pulmonary veins 
LA 
LV 
Aorta
Arteries 
Arterioles
Capillaries 
Venules
Veins

Question 7

Arterioles

Answer 7

– Smallest diameter muscular walled arteries

Question 8

Precapillary sphincters

Answer 8

– Rings of smooth muscle which control entry of blood from arteriole into each capillary

Question 9

Capillaries

Answer 9

– Smallest diameter blood vessel: simple tube, one cell thick, of flattened endothelial cells
– Allows for diffusion of nutrients, waste etc in/out tissues

Question 10

Venules

Answer 10

– Smallest diameter vessels which drain blood back to the larger true veins

Question 11

% of blood flow to brain

Answer 11

13%

Question 12

% of blood flow to heart

Answer 12

4%

Question 13

% of blood flow to skeletal muscle

Answer 13

20%

Question 14

% of blood Flow to skin

Answer 14

9%

Question 15

% of blood flow to kidneys

Answer 15

20%

Question 16

% of blood flow to abdominal organs

Answer 16

24%

Question 17

Atrioventricular (cuspid) valves

Answer 17

– Fairly ‘flimsy’
– Attached to chordae
tendineae and papillary muscles which stop eversion of the valves during systole

Question 18

Semiluminar valves

Answer 18

tricuspid
– More ‘heavy duty’
– Smaller openings, higher pressure  more stress and physical abrasion

Question 19

cardiac muscle cells

Answer 19

branch, and are connected together by desmosomes at the junction between cells (intercalated disks)

Question 20

intercalated disks

Answer 20

contain gap junctions that directly connect the cytoplasm and permit the easy transfer of ions between cells

Question 21

cardiac muscle features

Answer 21

Striated
– Similar to skeletal muscle
– Thick and thin filaments of myosin and actin
– Smaller fibers with individual nucleus

Connected via intercalated discs
– “Branching” of individual cells connected into a network

Electrical connection through gap junctions
– Allow passage of ions permitting action potentials to spread
– Functional syncitium

Desmosomes
– Strong, cell-to-cell adhesion molecules – Junctional complexes

Question 22

Conduction in cardiac muscle

Answer 22

Functional syncitium
– Cells of atrial myocardium are all electrically connected – Depolarise and contract synchronously
– Ventricles are similar but are a separate functional unit

Question 23

“Pacemaker” activity

Answer 23

– Sinoatrial node (SAN) is the intrinsic pacemaker – Other areas have pacemaker ability

Question 24

Autonomic innervation

Answer 24

– Sympathetic nerves increase the rate of SAN depolarisation

– Parasympathetic nerves decrease the rate of SAN depolarisation