Niyogi Lectures 5-7 Flashcards by Alexandra Cook

Why do some animals need circulatory systems?

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

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

prevents dehydration, protection, and support

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

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

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

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

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

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What are the functions of insect hemolymph? (4)

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

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What is hemolymph? What is it composed of?

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).

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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

suspended in hemolymph in invertebrates

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What colour is oxygenated and deoxygated hemolymph?

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

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All vertebrates and some invertebrates (cephalopods) have these.

close circulatory systems

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

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

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Cardiovascular systems in vertebrates have varying designs:

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

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

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

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

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What is the four-chambered pump of the mammalian heart

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

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Blood is pumped in what two separate circuits?

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

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

Open and close through pressure and prevent backflow

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

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

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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.

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

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

bottom upwards

What is systolic and diastolic pressure in Systemic circulation?

Systolic: 120 mm Hg
Diastolic: 80 mm Hg

Describe the heart conduction pathway

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.

Summarize the steps of cardiac muscle action potential.

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

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

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

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

200

Why do newborn babies have a much higher heart rate?

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.

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

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.

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

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

Compare the hearts of vertebrates.

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

70 ml/beat and 75 beats/min

How do you determine cardiac output?

Stroke volume x Heart rate

How is the heart rate controlled/monitored?

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.

What are arterioles?

Small branches of arteries that deliver blood to capillaries

What are venules?

Collect blood from capillaries to veins

How are blood vessels classified?

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.

True or false? Arteries and veins have backflow valves.

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

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

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

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

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

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

Limb muscle pumps and valves

How are capillaries adapted to their function?

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.

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

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

What are the functions of the lymphatic system?

- 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

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

- 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)