Niyogi Lectures 5-7

Question 1

Why do some animals need circulatory systems?

Answer 1

to provide tissues of bodies too many cell layers thick for diffusion alone with adequate oxygen, nutrient, and waste elimination needs

Question 2

What is the purpose of impermeable skin for animals that evolved to have circulatory systems instead of simple diffusion?

Answer 2

prevents dehydration, protection, and support

Question 3

What purposes does the circulatory system serve in terms of homeostasis and metabolism?

Answer 3

Question 4

How do the circulatory systems of different animals [sponge, insect, fish, and mammal] compare?

Answer 4

Sponges and cnidarians: is the simplest, uses water currents to circulate nutrients and waste

Invertebrates: open circulatory systems with ‘blood’ pumped by large heart in an open fluid space; blood vessels open to the animals body cavity which is filled with hemocoel
when blood and interstitial fluid mixes forms hemolymph

Question 5

Why are insects able to have open circulatory systems despite them having limited ability to alter the direction or velocity of blood flow?

Answer 5

Insect circulatory systems are not involved in oxygen transport so the low rate of oxygen transfer of open circulatory systems is irrelevant

Question 6

What are the functions of insect hemolymph? (4)

Answer 6

Transports nutrients, hormones, waste products and immune molecules
Hemolymph cells involved in wound repair and immune response
Hydraulic skeleton (specifically in larvae)
Heat transfer/circulation

Question 7

What is hemolymph? What is it composed of?

Answer 7

A fluid that acts as the ‘blood’ in vertebrates. For many animals, contains hemocyanin which is a metalloprotein with 2 copper atoms that is a major transporter of oxygen in invertebrates (excluding insects).

Question 8

Oxygen is
(a) bound to blood cells in in hemolymph having invertebrates
(b) suspended in hemolymph in invertebrates
(c) diffused through the skin
(d) synthesized from consumed biocarbonate

Answer 8

suspended in hemolymph in invertebrates

Question 9

What colour is oxygenated and deoxygated hemolymph?

Answer 9

colourless Cu(I) deoxygated
blue Cu(II) oxygated

Question 10

All vertebrates and some invertebrates (cephalopods) have these.

Answer 10

close circulatory systems

Question 11

What defines a closed circulatory system and why are they ideal for larger animals?

Answer 11

blood flows in a continuous circuit of tubes

Blood reaches all cells: capillary beds allow fine control of blood distribution that can increase delivery of oxygen to tissue very rapidly

Question 12

Cardiovascular systems in vertebrates have varying designs:

Single circulation is seen in __________
Parallel circulation in ________________
and double circulation in _______, __________, and ___________

Answer 12

Single circulation: fish
Parallel circulation: amphibians
Double circulation: mammals, birds, and crocodiles

Question 13

Why is blood pressure relatively low for the single circuit circulatory systems of fish?

Answer 13

Although, higher than in open system, blood pressure is low to avoid fluid leakage

Question 14

What is the four-chambered pump of the mammalian heart

Answer 14

Two atria at the top and two ventricles at the bottom
Atrioventricular (AV) valves between atria and ventricles
Semilunar (SL) valves between ventricles and aorta/pulmonary arteries

Question 15

Blood is pumped in what two separate circuits?

Answer 15

Pulmonary circuit (right heart)
Systemic circuit (left heart)

Question 16

What is the purpose of heart valves and how do they work?

Answer 16

Open and close through pressure and prevent backflow

Question 17

The initiation of the cardiac cycle varies for different animals. Compare neurogenic and myogenic hearts.

Answer 17

Neurogenic hearts (in some crustaceans) beat under control of the nervous system
Myogenic hearts (all other animals) contractions initiated within the heart

Question 18

The cardiac cycle can be divided into diastole and systole. What do these terms mean? Describe what is occurring in the heart during a cardiac cycle.

Answer 18

Diastole is a state of relaxation of the heart muscles where the chambers fill with blood
- muscles relax and AV valves open
- right atrium fills from vena cava and left atrium fills from pulmonary veins
Sinoatrial node (pacemaker) causes atriums to contract
- tricuspid and mitral valves respectively open so blood fills ventricles
(first and second diastole period)

Systole is a state of contraction where fibre branches send electrical impluses that cause ventricles to contract, thus,
- semilunar valve and aorta valve

Question 19

How do ventricles contract?
(a) entirely
(b) fibrously
(c) bottom upwards
(d) left to right

Answer 19

bottom upwards

Question 20

What is systolic and diastolic pressure in Systemic circulation?

Answer 20

Systolic: 120 mm Hg
Diastolic: 80 mm Hg

Question 21

Describe the heart conduction pathway

Answer 21

Conduction pathways are specialized cardiac muscle cells that coordinate heart cycles by changing speed of conduction.

Cardiac muscle (myocardium) is striated with special cell to cell connections that allows AP from the pacemaker to spread to all muscle cells of the heart. Pacemaker cell depolarizes slowly until muscle cell reaches threshold.

The SA node starts the sequence by causing the atrial muscles to contract. That’s why doctors sometimes call it the anatomical pacemaker. Next, the signal travels to the AV node, through the bundle of HIS, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract.

Question 22

Summarize the steps of cardiac muscle action potential.

Answer 22

Question 23

What is a ECG trend and how does it show heart contractions?

Answer 23

Question 24

A cycle repeats ____ to _____ times per minute at rest. Compare bradycardia and tachycardia.

Answer 24

60-100 times
Bradycardia: heartbeat of less than 60 beats per minute
Tachycardia: a heart rate over 100 beats per minute

Question 25

Heart rate may exceed _____ times/minute during intense exercise.

Answer 25

200

Question 26

Why do newborn babies have a much higher heart rate?

Answer 26

Due to rapid tissue growth the metabolic requirement is much greater, and therefore, the oxygen requirement is also greater.
Furthermore, compare the body size of an infant and adult human: the newborn has higher surface area to body ratio, so there is faster heat loss in the bodies of infants.

Question 27

Many professional athletes have a much lower resting heart rate than a regular person. How so?

Answer 27

The heart is more efficient because exercise strengthens the cardiac muscles and they have greater circulatory force. Therefore, a slower heart rate is required to meet oxygen needs.

Question 28

What is an advantage of a completely divided (double circuit) circulatory system?

Answer 28

Means high velocity to systemic tissue and supports high rates of cellular respiration (metabolism).

Question 29

Compare the hearts of vertebrates.

Answer 29

Question 30

The volume of blood ejected by the ventricle during each contraction (stroke volume) is ____ ml/beat and heart rate is ____ beats/min

Answer 30

70 ml/beat and 75 beats/min

Question 31

How do you determine cardiac output?

Answer 31

Stroke volume x Heart rate

Question 32

How is the heart rate controlled/monitored?

Answer 32

Chemoreceptos and baroreceptors in blood vessels monitor blood pressure, pH, CO2 levels, etc. and send these neurological signals to the medulla oblongata (brain stem) for processing.

Heart rate is controlled by the two branches of the autonomic (involuntary) nervous system. The sympathetic nervous system (SNS) releases the hormones (catecholamines - epinephrine and norepinephrine) to accelerate the heart rate. These electrochemical messages are sent through the spinal cord and then sympathetic nerve to the SA node (pacemaker).

The parasympathetic nervous system (PNS) releases the hormone acetylcholine to slow the heart rate. These signals are directly sent to the SA node by the parasympathetic vagus nerve from the cardiac centre in the medulla ob.

The Cerebrum and hypothalamus, above the medula, can indirectly influence heart rate by processing potential threats and causing hormonal or electrochemical messages to be sent to the medula to thus increase heart rate.

Question 33

What are arterioles?

Answer 33

Small branches of arteries that deliver blood to capillaries

Question 34

What are venules?

Answer 34

Collect blood from capillaries to veins

Question 35

How are blood vessels classified?

Answer 35

Arteries are much narrower than the veins because movement through veins occurs at a much lower pressure.

Arterial walls are much thicker as well, this is because the smooth muscle fibres contrict to regulate blood flow and these are not needed in veins to move blood at very low pressure.

Question 36

True or false? Arteries and veins have backflow valves.

Answer 36

False. Arteries do not need backflow valves because of the high pressure blood movement.

Question 37

What blood vessels act as pressure reservoirs and which act as blood reservoirs?

Answer 37

Arteries and aterioles act as pressure reservoirs
Veins and venules act as blood reservoirs

Question 38

What does the statement “velocity of blood flow is inversely related to total cross-sectional area” mean?

Answer 38

The more blood flow is dispersed between multiple blood vessels, the slower the blood move. This is due to decreased blood pressure.

Question 39

What two structures aid in venous return of blood to the heart?

Answer 39

Limb muscle pumps and valves

Question 40

How are capillaries adapted to their function?

Answer 40

Walls (endothelial cell layer) is one cell thick, so it is very thin and very near body cells.
Blood flow through a capillary bed is also highly regulated through a number of mechanisms, including the autonomic nervous system.

Question 41

What is the lymphatic system? What are it’s components?

Answer 41

An extensive network of vessels that collects excess interstitial fluid (becomes lymph) and returns it to the venous blood. This is a key component of the immune system.

Includes:
lymphs, lymphatic vessels, lymphatic tissues, lymphatic nodules and nodes, tonsils, the spleen, and the thymus

Question 42

What are the functions of the lymphatic system?

Answer 42

• Helps maintain fluid homeostasis
• Fat absorption from digestive tract to the venous circulation (left subclavian vein)
• Defends (aids immune system): microorganisms and other foreign substances are filtered from lymph by lymph nodes, and from blood by spleen, lymphocytes destroy microorganisms and other substances

Question 43

What major changes occur in our cardiovascular system during intense exercise?

Answer 43

• Increase in heart rate/ cardiac output (large) and stroke volume (small)
• Increased blood flow to the lungs (pulmonary circulation), skeletal muscle, heart and skin (vasodilation)
• decreased blood flow to GI tract and kidneys (vasoconstriction)