clinical physiology week 2

Question 1

model the cardiovascular system

Answer 1

• a pump (the heart)
• flexible, muscular vessels. (arteries and arterioles).
• a very large number of tiny vessels. (capillaries).
• large-capacity vessels. (venules and veins).

Question 2

outline systemic circulation;

Answer 2

1. left heart applies high pressure to high o2- low o2 blood.
2. systemic arteries and arterioles deliver this blood to most tissues.
   - systemic capillaries allow tissues to extract o2 from the blood and deliver CO2 to blood.

Question 3

outline pulmonary circulation;

Answer 3

1. right heart applies moderate pressure to low o2 and high co2 blood.
2. pulmonary arteries and arterioles deliver this blood to the lungs.
3. pulmonary capillaries allow lung tissue to deliver o2 to blood and extract co2 from the blood.

Question 4

outline how the heart is a 2-phase pump;

Answer 4

the heart; 2 phases.
1. relaxation; pressure within the heart drops and draws blood from veins to refill. (diastole).
2. contraction; applies pressure to the blood in the heart and ejects a proportion of it from the heart to the arteries. (systole).

Question 5

outline the four chambers of the heart;

Answer 5

left side;
- left atrium; receives blood from the pulmonary veins and passes blood to the left ventricle (atrial systole).
- left ventricle; applies pressure to blood (ventricular systole) and ejects a proportion into the arteries of the aorta.

right side;
- right atrium; receives blood from the veins of the vena cava and passes it into the left ventricle.
- right ventricle; applies pressure to the blood and ejects a proportion of it into the pulmonary arteries.

Question 6

what is flow?

Answer 6

• volume of fluid that passes through a tube per unit time.

Question 7

what is pressure?

Answer 7

• the force that the fluid exerts on the walls of its container.

Question 8

what is a pressure gradient?

Answer 8

• a difference in pressure between two areas in space.

Question 9

What does the heart do?

Answer 9

two tightly related things.
- applies pressure to blood during ventricular systole, this pressure establishes the pressure gradient that drives blood forwards in the CV system.
2. sends a proportion of its full (diastolic) volume into the arteries every single systole.

Question 10

What is cardiac output?

Answer 10

• The amount of blood pumped per minute.
• SVx HR = CO
• stroke volume in the volume of blood pumped per contraction.

Question 11

outline the role of arteries and arterioles in the CV system;

Answer 11

Arteries;
- larger more elastic vessels that conduct blood away from the heart to large organ/ tissue beds.
- pressure reservoirs.

arterioles;
- smaller more muscular vessels that feed the capillary tissue beds.
- the constrict or dilate to modify flow to each bed.

Question 12

Why does the pressure in arteries never get lower than ventricular diastole level?

Answer 12

• the arteries are full of elastic fibres within in the smooth muscular wall.
• every ventricular systole these vessels stretch which stores potential energy which is used to maintain pressure and drive the blood forwards.

Question 13

outline the pulmonary system;

Answer 13

• similar to the cardiovascular system.
• the muscular and elastic components of the pulmonary system are built to optimize flow.
• however air flows through its system not blood.
• the capillaries are built to optimize flow through the process of diffusion. however the goal is to exchange molecules between the atmosphere and the blood.

Question 14

outline the veins and venules of the CV system;

Answer 14

• veins return blood to the heart .
• systemic veins store 60% of the blood volume (5L).

Question 15

how do we control the cardiorespiratory apparatus?

Answer 15

• pressure sensors (baroreceptors).
• gas sensors (chemoreceptors) for O2 and CO2.
• pH sensors; detects H+ in the form of CO2 levels within the brain.

Question 16

what are the major baroreceptors?

Answer 16

• carotid arteries and the arch of the aorta.
• when the pressure drops a message is sent to the brain stem via nerves.
  1. activation of the sympathetic nervous system releases norepinephrine and epinephrine.
  2. E and NE elevate the heart rate and constrict arterioles to raise blood pressure.

Question 17

what are the major gas and pH sensors?

Answer 17

• peripheral; same location as baroreceptors. detects CO2 and O2.
• central (detects pH and CO2).
• central (detects pH and CO2) distributed throughout the brainstem.
• a drop in arterial O2 or a increase in arterial CO2 leads to a increase in respiratory rate and an increase in volume ventilated each breath.

Question 18

how does the cerebral cortex aid in respiratory system regulation?

Answer 18

• voluntary control of respiratory rate.

Question 19

how does the hypothalamus aid in respiratory system regulation?

Answer 19

• regulates respiratory rate based on emotional state, pain and body temperature set-points tells the brain stem to change ventilation.

Question 20

how does the proprioceptors aid in respiratory system regulation?

Answer 20

• when your muscles and joints move signals are sent to your brain stem, your ventilation changes in anticipation of increased MSK oxygen and CO2 exchange needs.

Question 21

how does the chemoreceptors (peripheral/central) aid in respiratory system regulation?

Answer 21

• increased ventilation when arterial oxygen drops and carbon dioxide increases; very strong influence on ventilation.

Question 22

How do the medulla and pons influence respiration?

Answer 22

• they regulate the activity of major muscles of ventilation.

Question 23

outline normalized values of respiratory vitals;

Answer 23

• normal heart rate at rest is between 60-100 beats per minute.