Circulatory System

Question 1

Why do simple invertebrates not need a heart?

Answer 1

They use internal cavities or intestines to expose cells directly to essential materials.

Question 2

Why did aerobes evolve circulatory systems?

Answer 2

To transport oxygen, which has limited solubility in water.

Question 3

Which organisms have open circulatory systems?

Answer 3

Sedentary organisms like molluscs and arthropods.

Question 4

Which group first evolved a closed circulatory system?

Answer 4

Annelids (segmented worms).

Question 5

What ensures unidirectional blood flow in evolved circulatory systems?

Answer 5

One-way valves.

Question 6

How do capillary beds help with gas exchange?

Answer 6

They separate high and low pressure systems for efficient exchange.

Question 7

What is the first organ to develop in embryos?

Answer 7

The heart.

Question 8

Where is the heart located?

Answer 8

Upper thorax, between the sternum and vertebrae.

Question 9

What is the average weight and shape of a human heart?

Answer 9

250–300 grams; conical in shape.

Question 10

What are the four chambers of the heart?

Answer 10

Two atria and two ventricles.

Question 11

What do the AV valves do?

Answer 11

Prevent backflow into the atria (tricuspid and bicuspid).

Question 12

What do semilunar valves prevent?

Answer 12

Backflow into the ventricles from arteries.

Question 13

What are intercalated discs and their function?

Answer 13

Connections between cardiac muscle cells that allow rapid action potential transmission.

Question 14

What are the phases of heart activity?

Answer 14

Diastole (relaxation) and Systole (contraction).

Question 15

What events are synchronized during heartbeat?

Answer 15

Atrial and ventricular contractions.

Question 16

What determines cardiac output?

Answer 16

Stroke volume × Heart rate.

Question 17

How does the sympathetic nervous system affect the heart?

Answer 17

Increases heart rate and contraction force during exercise.

Question 18

What is the myogenic mechanism?

Answer 18

Stretching of heart muscle fibers controls contraction strength (Starling’s Law).

Question 19

What happens to heart rate during exercise?

Answer 19

Sympathetic activation increases heart rate and contractility.

Question 20

What happens to heart rate at rest?

Answer 20

Parasympathetic activation slows the heart rate.

Question 21

What is a normal resting heart rate?

Answer 21

50–70 beats per minute.

Question 22

How high can heart rate go during exercise?

Answer 22

Up to 180 bpm.

Question 23

What is the stroke volume in trained athletes?

Answer 23

Increases from ~70 ml/beat to 120–180 ml/beat.

Question 24

What are the main components of the circulatory system?

Answer 24

Blood, heart, blood vessels, and capillary exchange surfaces.

Question 25

What is the function of the circulatory system?

Answer 25

Transport oxygen, nutrients, waste, and hormones; maintain homeostasis.

Question 26

What do arteries do?

Answer 26

Carry oxygenated blood away from the heart.

Question 27

What are veins responsible for?

Answer 27

Returning deoxygenated blood to the heart and acting as blood reservoirs.

Question 28

What controls blood flow in arterioles?

Answer 28

Vasoconstriction and vasodilation.

Question 29

Where does exchange of materials occur?

Answer 29

In capillaries organized into capillary beds.

Question 30

How is blood flow organized in the body?

Answer 30

In a parallel system: arteries to capillaries to veins.

Question 31

What are capillaries specialized for?

Answer 31

Gas, nutrient, and waste exchange.

Question 31

How do arteries differ from veins?

Answer 31

Arteries have thick, elastic walls; veins have valves and thinner walls.

Question 32

Where are continuous capillaries found?

Answer 32

In most tissues; they are least permeable.

Question 33

Where are fenestrated capillaries found?

Answer 33

In kidneys and endocrine glands; they have pores for larger molecules.

Question 34

What is special about discontinuous capillaries?

Answer 34

Found in liver and spleen; allow large molecules and cells through.

Question 35

What is the relationship between vessel diameter and flow?

Answer 35

Flow ∝ radius⁴ (small changes in diameter have large effects).

Question 36

Why is blood flow slower in capillaries?

Answer 36

Due to increased total cross-sectional area.

Question 37

How do arteries maintain pressure?

Answer 37

Their elastic walls expand and recoil.

Question 38

What happens to blood vessels in non-essential areas during exercise?

Answer 38

Arterioles constrict (vasoconstriction) to reduce flow.

Question 39

What causes vasodilation in active tissues?

Answer 39

Local metabolic changes like increased CO₂ and adenosine.

Question 40

What is autoregulation?

Answer 40

Local control of arteriolar diameter based on pressure and metabolic activity.

Question 41

How does the sympathetic system affect blood flow?

Answer 41

Causes vasoconstriction in non-essential areas and vasodilation in active tissues.

Question 42

What is Total Peripheral Resistance (TPR)?

Answer 42

Overall resistance of the vascular system; decreases in active areas during exercise.