lec 22- gas exchange and circulation part 2

Question 1

what are the two types of circulatory systems?

Answer 1

open and closed

Question 2

what happens in the open circulatory system?

Answer 2

hemolymph (similar to blood, in insects and invertebrates) is pumped throughout the body in open vessels, can also come in direct contact with tissues resulting in no need for diffusion

Question 3

what happens in the closed circulatory system

Answer 3

blood flows in a continuous circuit of closed vessels, pumping action is provided by the heart, blood flow can be directed in a precise way to respond to a tissues needs

-(example: blood going to muscles during exercise)

Question 4

what are the three types of blood vessels and what do they do?

Answer 4

-Arteries: tough, thick vessels that take blood away from the heart under high pressure (small arteries are called arterioles)
-Capillaries: are vessels whose walls are just one cell thick, allowing exchange of gases and other molecules between blood and tissues in networks called capillary beds
-Veins: are thin walled vessels that return blood to the heart (small veins are called venules/ veins dont have much muscle)

Question 5

what is the aorta and how does it propel blood?

Answer 5

-a large artery that receives blood from the heart, has smooth muscle fibres and elastic muscle fibres
-the elastic fibres in its wall allows it to expand when blood enters at high pressure then propels it forward through elastic recoil

Question 6

what do the muscle fibres in arterioles do?

Answer 6

-they relax to allow the diameter to increase, reducing resistance and increasing blood flow
-when they contract, they decrease the diameter, increase resistance and slow blood flow down
-This lets blood flow to specific tissues be done with the help of signals from the nervous system

Question 7

does blood pressure drop as blood passes through arterioles into the capillary beds?

Answer 7

yes

Question 8

why do veins have thinner walls and larger interior diameters compared to arteries?

Answer 8

because the blood is under relatively low pressure as it exits tissues

Question 9

what can speed up blood flow in veins?

Answer 9

skeletal activity which compress large veins

Question 10

what do the one way valves in large veins do?

Answer 10

-prevents backflow of blood
-skeletal muscle contraction and thoracic pressure assist in venous return (contraction closes valves to prevent backflow)

Question 11

what 2 things cause interstitial fluid build up?

Answer 11

1. an outward-directed hydrostatic force in capillaries, created by the pressure on blood created by the heart
2. an inward-directed osmotic force in capillaries, created by the higher concentration of solutes in the blood plasma than in the interstitial space

Question 12

what systems drains out excess fluid from tissues?

Answer 12

lymphatic system, thin wall branching tubules called lymphatic ducts drain the fluid

Question 13

what is lymph?

Answer 13

interstitial fluid that enters the lymphatic ducts is called lymph

Question 14

what does the lymphatic system do and what happens if blocked?

Answer 14

-large vessels return excess fluid to the veins entering the heart
-if the vessels are blocked, buildup of fluid and swelling will occur in the tissues

Question 15

what are the atria of the heart?

Answer 15

they recieve blood returning from circulation (atriums)

Question 16

what are the ventricles?

Answer 16

they generate force to propel blood out of heart through the circulatory system

Question 17

what separates the atria from the ventricles?

Answer 17

the atrioventricular valves

Question 18

what does the pulmonary artery and veins do?

Answer 18

-pulmonary arteries carry blood from the heart to the lungs
-pulmonary veins return freshly oxygenated blood to the heart

Question 19

what are the two circuits of the circulatory system?

Answer 19

1. pulmonary circuit- takes blood to lungs and gills
2. systemic circuit- takes blood to the body

Question 20

how does blood overcome gravity and at what pressures are the two circuits?

Answer 20

-blood overcomes gravity by being pumped at high pressure
-systemic circuit is high pressure and pulmonary circuit is low pressure

Question 21

how does blood flow through the heart?

Answer 21

-into the heart to body: after blood has circulated through alveoli and becomes oxygenated, it returns to the heart through the pulmonary veins, the oxygenated blood then goes through the left atrium and the atrium contracts, pushing blood into the left ventricle, then the ventricle contracts sending blood at high pressure through the aorta and into the arteries of the systemic circulation
-from body to heart: deoxygenated blood flows from the superior and inferior vena cava, then into the right atrium to the right ventricles, then to the pulmonary arteries in one way due to recoil of blood closing valves

Question 22

what causes heart murmur?

Answer 22

damaged heart valves

Question 23

why does blood pressure drop in the capillaries?

Answer 23

the rate of blood flow decreases to allow sufficient time for gases, nutrients and wastes to diffuse between tissues and blood in capillaries

Question 24

what two pumps help blood in veins to go back to the heart?

Answer 24

skeletal muscle contractions and respiratory pumps (pressure changes in the thoracic cavity during ventilation draw blood back to the heart)

Question 25

what pressure does the heart have?

Answer 25

negative pressure to help suck blood back in

Question 26

what conducts the electrical signals in the cardiac muscles of the heart?

Answer 26

cardiomyocytes

Question 27

how are the electrical signals transmitted between cardiomyocytes?

Answer 27

through gap junctions

Question 28

what causes the extended plateau phase during action potential generation of cardimyocytes?

Answer 28

slow calcium influx causes complete coordinated contraction of cardiac muscle

Question 29

can the heart still beat even when the nerves are severed?

Answer 29

yes

Question 30

what cells in the heart initiate contraction?

Answer 30

pacemaker cells

Question 31

where are pacemaker cells located?

Answer 31

in the sinoatrial (SA) node

Question 32

what type of action potentials do the pacemaker cells have?

Answer 32

unsteady action potentials

Question 33

what are the characteristics of cardiomyocyte unsteady action potentials?

Answer 33

drifting membrane potential due to slow influx of Na+ and quick influx of Ca2+ during depolarization and outflux of K+ during repolarization

Question 34

what do modified cardiomyocytes do?

Answer 34

direct electrical impulses through the heart on pathways made of them, send impulse down bundle of his then into the purkinje fibers

Question 35

what are the 5 steps in electrical activation of the heart?

Answer 35

1. SA node generates electrical signal
2. signal propagates to the atrial muscle cells causing them to contract simultaneously and eject blood into ventricles
3. signal is conducted to atrioventricular (AV) node, where there is a delay before passing through ventricles so the atria can completely fill the ventricles before they contract
4. After delay, the electrical impulse is rapidly transmitted through specialized fibres in the wall that separate ventricles
   -spreads through both ventricles causing contraction as the atria relax
   -signal goes from bottom to top of the ventricles causing blood to be ejected into arteries
5. The final electrical event causes ventricles to relax and cells are restored to initial state

Question 36

what is systole?

Answer 36

contraction phase of atrium and ventricles

Question 37

what is diastole?

Answer 37

relaxation phase of atrium and ventricles

Question 38

what is systolic blood pressure?

Answer 38

blood pressure measured when at the peak of ventricular ejection into the aorta

Question 39

what is diastolic blood pressure?

Answer 39

blood pressure measured just before ventricular ejection

Question 40

what makes up the numerator and denominator of blood pressure measurements?

Answer 40

systolic pressure is numerator, diastolic pressure is the denominator

Question 41

what is hypertension?

Answer 41

when blood pressure is higher than 140/90, leads to circulatory defects like heart attack, kidney failure etc. due to stress on artery walls

Question 42

what causes lub dub sound in heart?

Answer 42

valves closing and opening

Question 43

what senses blood pressure in arteries?

Answer 43

baroreceptors

Question 44

what do baroreceptors do?

Answer 44

when they detect a change in blood pressure, they trigger electrical signals that change the hearts output (output change by changing heart rate and contraction)

Question 45

can arteries be constricted to serve blood to more vital organs?

Answer 45

yes

Question 46

can veins shift blood volume towards the heart and arteries to maintain blood pressure and flow to vital organs?

Answer 46

yes

Question 47

what causes cardiovascular disease and heart attacks?

Answer 47

high fat diets and lack of physical activity leads to buildup of fatty plaques on the walls of arteries increasing pressure and reducing diameter, complete blockage causes myocardial infarction/ heart attacks (portion of the heart tissue dies)