BiM Cardiorespiratory Physiology

Question 1

1. Give 3 functions of blood
2. What is the most abundant protein in blood and what is it involved in
3. What is the composition of blood
4. What is the ‘Buffy coat’

Answer 1

1. Transport oxygen, CO2, nutrients, waste, hormones. Defence, homeostasis
2. Albumin - regulates blood volume and fluid levels
3. 55% plasma - water, proteins, solutes
   45% formed elements - RBCs, WBCs, PLTs
4. Portion of blood made up of WBCs and PLTs

Question 2

1. What are RBCs derived from
2. What are WBCs derived from
3. Name 4 WBCs
4. What are PLTs derived from

Answer 2

1. Erythroblasts (pro, early, intermediate, late, reticulocytes)
2. Myeloblasts/lymphoblasts/monoblasts
3. Basophil, eosinophil, neutrophil, lymphocyte, monocyte
4. Megakaryoblasts/megakaryocytes

Question 3

1. Describe the flow/direction of blood through vessels
2. What is the function of arteries
3. Briefly outline the structure of an artery
4. What is the function of an arteriole

Answer 3

1. Arteries –> arterioles –> capillaries –> venules –> veins
2. Pump blood away from heart under pressure
3. 3 layers - inner endothelium, middle elastic tissue and smooth muscle, outer connective tissue
4. Take blood from arteries and give to capillaries

Question 4

1. What are capillaries and where are they found
2. What do capillaries do
3. How is the structure of a capillary advantageous

Answer 4

1. Small vessels between arterioles and venules found in capillary beds
2. Oxygenate tissues
3. One cell thick - allows rapid oxygen/CO2 diffusion through capillaries

Question 5

1. What are venules
2. What is the function of a vein
3. Briefly outline the structure of a vein
4. What is a key component in a vein and what does this do
5. Name 4 things that support/encourage venous return

Answer 5

1. Mini veins that gather to form veins
2. Return blood back to heart in low-pressure system
3. Inner endothelium, middle elastic and smooth muscle layer (thinner than arteries - compressible), outer connective tissue
4. Valves - prevent back flow of blood
5. Gravity - from head and neck
   Blood pressure
   Skeletal muscle pump - muscle contraction squeezes nearby veins, pushing blood along veins
   Respiratory pump - diaphragm moves downwards during inhalation, creating negative pressure in thoracic cavity, drawing air and blood in, back to heart

Question 6

1. Name the heart valves, where they are found, their structure and describe their functions
2. Which valve is also known as the mitral valve
3. Describe the path of blood flow from the right atrium back again

Answer 6

1. Right AV valve - tricuspid. 3 cusps. Ensure unidirectional flow of blood from right atrium to right ventricle
   Left AV valve - bicuspid. 2 cusps. Ensure unidirectional flow of blood from left atrium to left ventricle
   Right semilunar valve - in pulmonary artery. Crescent shape. Prevent back flow into right ventricle.
   Left semilunar valve - in aorta. Crescent shape. Prevent back flow into left ventricle.
2. Left AV/bicuspid valve
3. Right atrium –> right AV valve (tricuspid) –> right ventricle –> right SL valve –> pulmonary artery –> lungs –> pulmonary vein –> left atrium –> left AV valve (bicuspid) –> left ventricle –> left SL valve –> aorta –> tissues –> vena cava –> right atrium

Question 7

1. What are chordae tendineae and what do they do
2. What are papillary muscles and what do they do
3. What are the heart sounds

Answer 7

1. Strong cords that hold AV valves closed, preventing valve from opening backwards into atrium
2. Cone-shaped protrusions of cardiac muscle that hold chordae tendinae
3. Closing of the valves - lub (AV valves close as ventricles contract), dub (SL valves close as ventricles relax)

Question 8

1. What are the 2 zones of the lower respiratory tract
2. What epithelium is found in the trachea
3. What is the function of cilia in trachea
4. What epithelium is found in the bronchi

Answer 8

1. Conducting zone - passages that bring air in and out
   Respiratory zone - where gas exchange occurs
2. Pseudostratified ciliated columnar epithelium
3. Mucociliary escalator - move mucus up and out
4. Pseudostratified ciliated columnar epithelium

Question 8

1. What are 3 functions of the respiratory system
2. Outline the pathway of air from external environment
3. What are 2 functions of the nasal cavity
4. What is the function of the Eustachian tubes
5. What is the function of the epiglottis

Answer 8

1. Gas exchange, regulate pH, protection from inhaled pathogens and irritating substances, vocalisation
2. Nose –> pharynx –> larynx –> trachea –> bronchus –> bronchioles –> alveoli
3. Warm air, molten air, trap dust
4. Drain fluid from middle ear and equalise pressure across eardrum
5. Direct water/air/food

Question 9

1. What is Dalton’s law of ventilation
2. What is Boyle’s law of ventilation
3. How do gases move
4. What are the 2 phases of respiration. Briefly describe each
5. What 2 additional muscle groups are involved in forced expiration

Answer 9

1. Total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases
   Pgas = Patm x % of gas in atmosphere
2. At a fixed temperature, the volume of gas is inversely proportional to the pressure exerted by the gas
   P1V1 = P2V2
3. From area of high to area of lower pressure
4. Insipration/inhalation - active process. Diaphragm contracts and flattens and external intercostal muscles pull ribs up and out. Air drawn into lungs due to decrease in thorax pressure (increase in volume)
   Expiration/exhalation - passive process. Diaphragm relaxes and moves up and external intercostals relax back into place. Pressure in thorax increases, lungs get smaller, air pushed out
5. Internal intercostals, abdominal muscles

Question 10

1. Define tidal volume (TV)
2. Define inspiratory reserve volume (IRV)
3. Define expiratory reserve volume (ERV)
4. Define vital capacity (VC) and how this can be calculated
5. Define residual volume (RV)
6. Define functional residual capacity (FRC)

Answer 10

1. Amount of air breathed in/out with each respiratory cycle (normal breathing)
2. Additional volume of air that can be breathed in, above tidal volume, upon forced inspiration
3. Additional volume that can be breathed out after normal tidal exhalation, during forced expiration
4. Total amount of air exhaled after maximal inhalation. VC = TV + IRV + ERV
5. Volume of air remaining in lungs after maximal exhalation (cannot be exhaled, prevents collapse of alveoli)
6. Amount of air remaining in lungs at end of normal exhalation

Question 11

1. Briefly describe how oxygen is transported
2. Briefly describe how CO2 is transported
3. What is the formula for the bicarbonate buffer reaction
4. How does blood maintain pH in relation to bicarbonate ion
5. How does gas exchange occur in the lungs
6. How does gas exchange occur at tissues

Answer 11

1. Oxygen inhaled into lungs, passes through air sacs into BVs, where it binds to haemoglobin in RBCs (oxyhaemoglobin) through diffusion (exchange with CO2). Blood carries oxygenated blood to tissues, where O2 diffuses into mitochondria.
2. CO2 produced in cells and diffuses into blood through capillary walls.
   70% combines with water to form carbonic acid in RBCs. 7% stays dissolved in plasma, 23% forms carbaminohaemoglobin
   Carbonic acid dissociates into bicarbonate and H ion
   Bicarbonate diffuses out of RBCs into plasma, taken to lungs
   In lungs, bicarbonate re-enters RBCs, in exchange for chloride
   CO2 released from RBCs into lungs, which is then exhaled
3. H2CO3 <=> H+ + HCO3-
4. Excess H ions combine with global to form reduced haemoglobin (HHb)
5. PCO2 in lung capillaries > air in lungs, so CO2 diffuses out of plasma into lungs
   PO2 in air in lungs > lung capillaries, so O2 diffuses into RBCs from lungs
6. PO2 capillaries > tissue fluid, so O2 diffuses out of blood into tissues
   CO2 carried as bicarbonate ion

Question 12

1. Very briefly describe how homeostasis will correct an increase in CO2
2. Very briefly describe how homeostasis will correct a decrease in CO2
3. Where does respiratory regulation occur
4. What happens when you hold your breath

Answer 12

1. Rise in CO2 decreases pH. Sensed by chemoreceptors on brain and circulatory system. Respiration will increase to compensate, clearing CO2 build up
2. Decrease in CO2 increases pH. Sensed by chemoreceptors on brain and circulatory system. Respiration slows to allow CO2 levels to build
3. Medulla oblongata (involuntary) and voluntary higher brain centres
4. CO2 increases due to cellular respiration. pH decreases leading to acidosis. Chemoreceptors override higher brain centres and the medulla oblongata takes over, forcing a breath

Question 13

1. What does the oxygen-haemoglobin dissociation curve measure
2. What does a shift to the right of the curve indicate. List 3 things that would cause a shift to the right
3. What does a shift to the left of the curve indicate. List 3 things that would cause a shift to the left
4. How does exercise influence the curve

Answer 13

1. The relation between the partial pressure of oxygen (x axis) and the oxygen saturation (y axis). Hemoglobin’s affinity for oxygen increases as successive molecules of oxygen bind. More molecules bind as the oxygen partial pressure increases until the maximum amount that can be bound is reached. As this limit is approached, very little additional binding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. Hence the curve has a sigmoidal or S-shape.
2. Decreased affinity of Hb for oxygen. Increase CO2, temperature, acidity (lower pH)
3. Increased affinity of Hb for oxygen. Decrease CO2, temperature, acidity (higher pH)
4. Increase exercise –> higher metabolic rate. Need more O2, produce more CO2 and lactate and temperature rises. Increase exercise causes shift of curve to the right

Question 14

1. What is VO2 max
2. What is oxygen diffusion capacity
3. How does smoking affect lung capacity
4. What is the limiting factor for the delivery of oxygen
5. Briefly describe the respiratory changes seen during exercise

Answer 14

1. Rate of oxygen usage under maximal aerobic metabolism
2. Rate at which oxygen can diffuse from pulmonary alveoli into blood
3. Decreases lung capacity
4. CVS (ventilation can be increased to greater extent than CVS)
5. Total lung capacity rises slightly, residual lung volume decreases slightly
   Tidal volume at max exertion increases
   Resp rate and pulmonary ventilation decrease at rest and submax levels (due to improved pulmonary efficiency)
   Resp rate and pulmonary ventilation increases at max exertion (due to increased tidal volume)

Question 15

1. What happens to blood Flow during exercise
2. What circulatory readjustments are made during exercise
3. What happens to the following after aerobic training
   a) CR endurance
   b) VO2 max
   c) Heart weight, volume, chamber size
   d) SV (and how)
   e) Resting HR, submaximal HR and maximal HR
4. What happens to maximal CO with age and heart disease

Answer 15

1. Large increase in blood flow to exercising muscles
2. Sympathetic activation in many tissues (increased HR and contractility), increase in arterial pressure (vasoconstriction of arterioles and small arteries, increased cardiac contractility, increased mean systolic filling pressure), increased CO (SV and CO)
3. a) Increased
   b) Decreased at rest/submax, increased at max
   c) Increased
   d) Increased (EDV increased, ESV decreased)
   e) RHR decreased, submax HR decreased, max HR decreased
4. Decreased