lecture 15,16-

Question 1

Why do we need circulatory system ?

Answer 1

animal cells need to be able to obtain nutrients ,exchange respiratory gases and remove waste products
1. diffusion
cells direct contacy to environment
flattened body =increase SA
larger animals no
strategy 2
cant rely on diffusion alone

Question 2

What is the circulatory systemss strategy ?

Answer 2

to transport hormones, nutrients,
respiratory gases, blood cells, waste products (etc) around the body:
o Such systems have hearts which move ECF throughout the body.
o ECF ( maintains and supports the
metabolic needs of all body cells, e.g. O2, nutrients, etc

Question 3

What can circulatory systems be ?

Answer 3

open:fluid inside the circulatory system is the same as the ECF (outside) → called hemolymph; no defined blood.
o Fluid leaves circulatory system vessels, percolates between cells/tissues, then flows back into heart or vessels

Question 4

eg of invertebrates with open circulatory systems ?

Answer 4

anthropods-spiders,crustaceans & most molluscs-clams
well developed central central heart ;moves hemolymph through discrete vessels leading to diff regions
A-hemplymph returns to heart via ostia
ostia have valves to allow hemolymph entry into relaxed heart ->1 way flow when heart contracts

Question 5

Molluscs and their open circualtory system ?

Answer 5

O2 carried by haemocyanin
-contains copper instead of iron;so oxygenated blood is blue instead of red like in vertebrates

Question 6

What do insects have ?

Answer 6

open system

Question 7

What invertebrates hasve closed circulatory system ?

Answer 7

annelid worm
from ventral vessel progressively smaller vessels transport blood to tissues—>allow gas,nutrient delivery and waste removal

Question 8

The advantages of a closed circulatory system ?

Answer 8

1. fluid can flow more rapidly through vessels than intracellular spaces–>enables rapid transport of gases ,nutrients & waste
2. can control resistance of specific vessels allowing selective direction of blood flow to specific tissues/organs
3. cells,large molecules of interest can be retained

Question 9

In fish how does vertebrate circulation occur ?

Answer 9

fish heart = 4 chambers
blood returns from body collects in sinus venosus –>atrium–>ventricle–>bulbous arteriosus
arterial blood-leaves last chambers-flows through gills–>respiratory gases exchanged ->collects in dorsal aorta then blood is distributed into smaller arteries & arterioles

Question 10

How does circulation in fish work ?

Answer 10

single circuit
unidirectional blood flow enabled by 1 way valve between heart chambers
1. heart pumps blood anteriorly into ventral aorta which gives off afferent branchial vessels to gill arches
2. blood perfuses the gill
3. blood is collected into efferent brachial vessels which empty into dorsal aorta
4. blood distributed to systemic tissues
5. great veins return deoxyblood from tissues to heart

Question 11

Whagt are lung fish ?

Answer 11

these fish can breather
air-breathing organs are derived from mouth membranes ,gut or swim bladders
adaptation ;outpocketing of the gut serves as a lung ABO
Heart partially sperates its blood flow into pulmonary & systematic circuits

Question 12

Teolast vs lung fishes circuit ?

Answer 12

lungfish-modified central circulation :blood from lungs enters left side –>deoxy & oxy kept relatively seperate pumped to lungs & systemic circuits

Question 13

Amphibians and their vertebrate ciculation ?

Answer 13

partial seperation of pumonary and systematic circuits;3 chambered heart
single ventricle pumps blood to lungs and rest of body but note that 2 atria recieve blood returning to the heart
Left atrium receives oxygenated blood from lungs; right atrium receives
deoxygenated from body.
* Blood mixing in ventricle is limited → ventricle directs deoxy. blood flow to the pulmonary circuit; oxy. heads to aorta (primarily).

Question 14

Vertebrate circulation on reptiles ?

Answer 14

can control blood flow to seperate pulmonary circuit;3 chambered heart
ventricle is incompletely divided by a
partial septum; left & right
atria receive oxygenated (from lungs)
and deoxygenated blood, resp. →
blood flows to L and R ventricle.
if air-breathing, lung circuit has lower
vascular resistance than systemic →
blood flows to lungs (from R ventricle
into pulmonary artery). Blood flow to
lungs is reduced when not breathing
→ lung vessels constrict → lung
circuit resistance increases → blood
flows mostly into right aorta instead.

Question 15

What do cephalopods & molluscs have ?

Answer 15

closed circulatory systems :lblood enters systemic heart via gills into aortae to systemic tissues as blood returns it splits into 2 paths directed to the gills via 2 weaker auxillary brachial hearts

Question 16

How does the systemic and pulmonary circulations in humans ?

Answer 16

closed loop circulatory system :blood pumped out of heart through 1 set of blood vessels returns by a different set both sides=arteries carry blood away from heart & veins carry blood back

Question 17

What is a Poiseuille law ?

Answer 17

resistance is directly proportional to fluid viscosity and vessel length and inversely proportional to the 4th power of vessel radius

Question 18

What is the heart enclosed wiithin ?

Answer 18

pericardium (protective fibrous sac) attached to epicardium ( fibrous outer membrane )
are seperated by fluid filled pericardial cavity
inner surface lined with endocardium

Question 19

What is the tricuspid valve ?

Answer 19

right AV valve
3 fibrous flaps
seperates the right atrium and right ventricle
stop blood being forced from ventricles back into atria

Question 20

What is bicuspid valve ?

Answer 20

left AV valve
2 fibrous flaps
seperates the left atrium and left ventricle
also called mitral valve

Question 21

opening and closing of atrioventricular valves ?

Answer 21

passive processes depending on presuure differences across valves :
atrium filling
* BP in atrium increases
* When BP in atrium gretaer than corresponding ventricle ,AV valve opens->blood flows into ventricle
During ventricular contraction
* BP in ventricle increases
* BP in ventricle greater than that in corresponding atrium ,AV valve force closed –> blood flows to either
1. Pulmonary circuit
2. systemic circuit

Question 22

How does the prevention of backward flow through AV valves actually work ?

Answer 22

AV valves are attached to the ventricle wall by papillay muscles and fibrous chordae tendinae that limit valves movement
stoping going inside out during ventricular contraction

Question 23

What supplies blood?

Answer 23

The myocardium heart is supplied by coronoary arteries which arise at root of aorta
moat of venous blood from this coronary circulation drains in to the right atrium via coronary sinus

Question 24

The cardiac cycle ?

Answer 24

1. Both relaxed blood flows into the atria and ventricles
2. Atria contract simultaneously ;blood flows into relaxed ventricles
3. Quickly followed by contraction of ventricles –> blood exits/ejected ;atria are relaxed so blood enters again

Question 25

atrial contraction ?

Answer 25

Occurs after P wave of ECG.
o AV valves (between atria & ventricles) open
as pressure in atria > in ventricles.
o 10-20% more blood enters ventricles.
o Semilunar valves (aortic and pulmonary)
are closed.

Question 26

isovolumetric contraction ?

Answer 26

Begins with appearance of QRS complex in ECG
o All valves are now closed:
o First heart sound (S1; “lubb”) due to
closure of AV valves.
o Ventricular pressure rises rapidly →
ventricles contract, but since all valves are closed → volume remains constant (blood cannot exit/be ejected, yet…).

Question 27

Ventricular ejection ?

Answer 27

Rapid ejection:
o AV valves remain closed.
o Semilunar valves now open:
o Blood flows rapidly from ventricles into arteries (↑ pressure in ventricles).
o Reduced ejection:
o Starts ~200 msec after QRS complex.
o Tension on ventricles reduce, thus rate of ejection falls → blood flows mainly due to kinetic energy of blood.

Question 28

Isolvolumetric relaxation ?

Answer 28

Ventricle begins to repolarise (T wave).
o All valves now closed.
o Second heart sound (S2; “dupp”)
marks the end of systole.
o Ventricles stop contracting; ventricular pressure decreases.
o Ventricular volume is constant:
o End-systolic volume (ESV) is ~50 ml
in (left) ventricle; stroke volume (SV)

Question 29

Atrial filling and ventricular filling ?

Answer 29

Stage 1 (rapid filling):
o AV valves are open.
o Semilunar valves remain closed.
o Blood flows from atria into ventricles:
o At rest, ~80% of ventricular filling
occurs before atrial contraction…
o Stage 2 (reduced filling):
o Valves as above.
o Atria contract (slide 44): atrial systole.
o Ventricular filling continues to
completion (10-20% more blood enters
ventricles; ventricular diastole).