Cardiovascular 2

Question 1

Extrinsic vs intrinsic peep

Answer 1

PEEP = Positive End Expiratory Pressure. Equivalent to a constant pressure applied throughout the respiratory cycle.
.
Intrinsic PEEP = unintentional or un-measured end-expiratory hyperinflation

2019 march Q20 cicm wrecks

Question 2

what does PEEP do do intrahoracic pressure

Answer 2

Cardiovascular effects: Causes constant ↑ intrathoracic pressure (ITP) throughout respiratory cycle

2019 march Q20 cicm wrecks

Question 3

What does peep do to cardiac output

Answer 3

o ↓ C.O. and ↑ Central venous pressure
▪ ↓ Renal blood flow, ↓ Glomerular Filtration Rate and urine output
▪ ↑ ADH and Angiotensin II levels
▪ ↑Hepatic venous pressure → ↓ Hepatic Blood Flow
o ↑ CVP and ↓ venous return
▪ ↑ Intracranial pressure

2019 march Q20 cicm wrecks

Question 4

What does peep do to central venous pressure

Answer 4

o ↓ C.O. and ↑ Central venous pressure
▪ ↓ Renal blood flow, ↓ Glomerular Filtration Rate and urine output
▪ ↑ ADH and Angiotensin II levels
▪ ↑Hepatic venous pressure → ↓ Hepatic Blood Flow
o ↑ CVP and ↓ venous return
▪ ↑ Intracranial pressure

2019 march 20 cicm wrecks

Question 5

What does peep do to venous return

Answer 5

o ↓ C.O. and ↑ Central venous pressure
▪ ↓ Renal blood flow, ↓ Glomerular Filtration Rate and urine output
▪ ↑ ADH and Angiotensin II levels
▪ ↑Hepatic venous pressure → ↓ Hepatic Blood Flow
o ↑ CVP and ↓ venous return
▪ ↑ Intracranial pressure

2019 march Q20 cicm wrecks

Question 6

What does peep do to intracranial pressure

Answer 6

o ↓ C.O. and ↑ Central venous pressure
▪ ↓ Renal blood flow, ↓ Glomerular Filtration Rate and urine output
▪ ↑ ADH and Angiotensin II levels
▪ ↑Hepatic venous pressure → ↓ Hepatic Blood Flow
o ↑ CVP and ↓ venous return
▪ ↑ Intracranial pressure

2019 march Q20 cicm wrecks

Question 7

What does peep do to pulmonary vascular resistance

Answer 7

Transmitted alveolar pressure increases pulmonary vascular resistance

2019 march Q20 deranged specific answer

Question 8

What does peep do to right ventrciular afterload

Answer 8

Increased pulmonary vascular resistance increases right ventriular afterload

2019 march Q20 deranged specific answer

Question 9

What does peep do to right ventricular stroke volume

Answer 9

Thus, increased afterload and decreased preload has the net effect of decreasing the right ventricular stroke volume.

2019 march Q20 deranged specific answer

Question 10

what does peep do to left ventricle preload and afterload and stroke volume

Answer 10

• Decreased preload by virtue of lower pulmonary venous pressure
• Decreased afterload due to a reduction in LV end-systolic transmural pressure and an increased pressure gradient between the intrathoracic aorta and the extrathoracic systemic circuit
• Thus, decreased LV stroke volume

2019 march Q20 deranged specific answer

note; I think the easiest trick to remember this is that if there is decreased preload there will be lower stroke volume

Question 11

examiner comments

Describe the cardiovascular effects of positive pressure ventilation on a patient who has received a long-acting muscle relaxant.

Answer 11

Describe the cardiovascular effects of positive pressure ventilation on a patient who has received a long-acting muscle relaxant. 2019 march Q20 examiner comment

33% of candidates passed this question. Structured answers separating effects of positive pressure on right and left ventricle, on preload and on afterload were expected. Overall there was a lack of depth and many candidates referred to pathological states such as the failing heart. Simply stating that positive pressure ventilation reduced right ventricular venous return and/or left ventricular afterload, without some additional explanation was not sufficient to achieve a pass level.

Question 12

The ECG device detects and amplifies the small electrical changes on the skin that are caused when the heart muscle depolarizes (x mV).

Answer 12

The ECG device detects and amplifies the small electrical changes on the skin that are caused when the heart muscle depolarizes (0.5 – 2 mV). This is reflected as rises and falls in the voltage between two electrodes placed either side of the heart which is displayed either on a screen or on paper. Usually more than 2 electrodes are used and they can be combined into a number of pairs (For example: Left arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairs LA+RA, LA+LL, and RA+LL).

2016 march Q9 examiners comment

Question 13

ECG; The output from each pair is known as a?

Answer 13

Usually, more than 2 electrodes are used and they can be combined into a number of pairs (For example: Left arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairs LA+RA, LA+LL, and RA+LL). The output from each pair is known as a lead. Each lead is said to look at the heart from a different angle.

2016 march Q9 examiners comment

Question 14

ECG Electrodes are commonly made of?

Answer 14

Electrodes are commonly made of silver or silver chloride components that are attached to the main unit of the machine. Most ECG machines use 12 electrodes. Better answers made mention of the two lead types: unipolar and bipolar. Methods to reduce artefact include improving signal detection (conductive paste, skin preparation (dry, no hair, etc.)) and minimizing external electrostatic forces (common earthed environment, diathermy, etc.,) or patient environment (avoid shivering).

2016 march Q9 examiners comment

Question 15

Most ECG machines use how many electrodes?

Answer 15

Electrodes are commonly made of silver or silver chloride components that are attached to the main unit of the machine. Most ECG machines use 12 electrodes. Better answers made mention of the two lead types: unipolar and bipolar. Methods to reduce artefact include improving signal detection (conductive paste, skin preparation (dry, no hair, etc.)) and minimizing external electrostatic forces (common earthed environment, diathermy, etc.,) or patient environment (avoid shivering).

2016 march Q9 examiners comment

Question 16

What are the two lead types/

Answer 16

Better answers made mention of the two lead types: unipolar and bipolar. Methods to reduce artefact include improving signal detection (conductive paste, skin preparation (dry, no hair, etc.)) and minimizing external electrostatic forces (common earthed environment, diathermy, etc.,) or patient environment (avoid shivering).

2016 march Q9 examiners comment

Question 17

ECG Methods to reduce artefact include ?

Answer 17

improving signal detection (conductive paste, skin preparation (dry, no hair, etc.)) and minimizing external electrostatic forces (common earthed environment, diathermy, etc.,) or patient environment (avoid shivering).

2016 march Q9 examiners comment

Question 18

The amplifier has three essential functions:

Answer 18

The amplifier has three essential functions: High input impedance so as to minimize signal loss and reject interference (50 – 60 Hz), differential amplification, (to amplify the potential difference detected by the skin electrodes), and high common mode rejection (e.g. > 50Hz) to aid eliminating muscle artefact or electrical interference from the power grid.).

2016 march Q9 examiners comment

note; eli5, the way I remember this is high input impedance to reject interference from all others, amplification to increase signal, and high common mode rejection to eliminate interference from high frequency source

Question 19

2016 march Describe the essential components of an ECG monitor (80% of marks). Outline the methods employed to reduce artefact (20% of marks). 2016 march repeated in 2011 aug

Relation of cellular ionic events to surface ECG

Answer 19

• Relation of cellular ionic events to surface ECG
  o Extracellular charge of resting myocyte membrane is positive
  o Depolarisation makes it negative
  o This difference in charge along the myocardium produces an electric field
  o The difference between two surface measurements of electric field strength is the potential difference (voltage) measured by the ECG leads
  o Each pair of electrodes is a “lead”

deranged 2016 march Q9

Question 20

2016 march Describe the essential components of an ECG monitor (80% of marks). Outline the methods employed to reduce artefact (20% of marks). 2016 march repeated in 2011 aug

• Relation of surface ECG to events of the cardiac cycle

Answer 20

• Relation of surface ECG to events of the cardiac cycle
  o P wave: depolarisation of atrial muscle
  o PR interval: AV node onduction
  o QRS: depolarisation of the ventricular muscle
  o Peak of the R wave: beginning of isovolumetric contraction
  o T wave: ventricular repolarisation

deranged 2016 march Q9

Question 21

2016 march Describe the essential components of an ECG monitor (80% of marks). Outline the methods employed to reduce artefact (20% of marks). 2016 march repeated in 2011 aug

• Essential components of an ECG monitor

Answer 21

• Essential components of an ECG monitor
  o Signal transmission: by silver/silver chloride electrodes
   Thin and broad electrodes (10mm diameter)
   Conducting gel to improve skin contact
   Digital signal
   High sampling rate (10,000-15,000 Hz) to detect pacing spikes
  .
  o Amplification
   Low signal amplitude (0.5-2.0 mV) requires a ~ 1,000 gain factor
   Differential amplification only amplifies the difference between electrode leads, rather than the absolute voltages
   This eliminates sources of noise which affect each electrode equally (this is called common-mode rejection)
  .
  o Isolation removes mains interference and protects components
  o Earthing reduces interference
  .
  o Filtering
   Most ECG information is contained in signals 1.0-30 Hz
   Monitoring mode filter the signal frequency to 0.5-30 Hz range
   Diagnostic mode filter the signal frequency to 0.05-100 Hz range
   High input impedance of the amplifier decreases the conduction of high-frequency signals, eliminating mains interference and EMG signal
   Low pass filtering eliminates movement artifact

deranged 2016 march Q9

Question 22

Mixed venous PCO2 is usually about x mmHg, and is determined by the total oxygen content of mixed venous blood and the shape of the CO2 dissociation curve

Answer 22

Mixed venous PCO2 is usually about 46 mmHg, and is determined by the total oxygen content of mixed venous blood and the shape of the CO2 dissociation curve

deranged specific answer for 2015 august Q23

Question 23

The total CO2 content of mixed venous blood, which is usually about x ml/L, is described by the modified x equation:

Answer 23

The total CO2 content of mixed venous blood, which is usually about 520 ml/L, is described by the modified Fick equation:
VCO2 = CO × k × (PvCO2 - PaCO2)

where

VCO2 is the rate of CO2 production,
CO is the cardiac output,
PvCO2 - PaCO2 is the arteriovenous CO2 difference, and
k is a coefficient used to describe the near-linear relationship between CO2 content and partial pressure in the blood.

deranged specific answer for 2015 august Q23

Question 24

any increase in arterial CO2 will be inherited by the x CO2. This is controlled by the x

Answer 24

The CO2 content of arterial blood - any increase in arterial CO2 will be inherited by the mixed venous CO2. This is controlled by the central ventilation reflexes.

deranged specific answer for 2015 august Q23

Question 25

CO2 production in the tissues, which is related to the rate of aerobic metabolism and oxygen consumption (VO2). A low metabolic rate will cause a x in mixed venous CO2 (eg. hypothermia).

Answer 25

CO2 production in the tissues, which is related to the rate of aerobic metabolism and oxygen consumption (VO2). A low metabolic rate will cause a decrease in mixed venous CO2 (eg. hypothermia).

deranged specific answer for 2015 august Q23

Question 26

Cardiac output, which determines the rate of tissue CO2 removal.
Poor cardiac output (eg. in cardiogenic shock) will cause an x mixed venous CO2 by a “stagnation phenomenon”
I.e. an abnormally large amount of CO2 will be added to capillary blood per unit volume if the transit time is x (i.e. flow is x)

Answer 26

Cardiac output, which determines the rate of tissue CO2 removal.
Poor cardiac output (eg. in cardiogenic shock) will cause an increased mixed venous CO2 by a “stagnation phenomenon”
I.e. an abnormally large amount of CO2 will be added to capillary blood per unit volume if the transit time is increased (i.e. flow is decreased)

deranged specific answer for 2015 august Q23

Question 27

what term describes; deoxygenated haemoglobin has a higher affinity for CO2

Answer 27

deoxygenated haemoglobin has a higher affinity for CO2 (the Haldane effect).

deranged specific answer for 2015 august Q23

Question 28

the Haldane effect

Answer 28

deoxygenated haemoglobin has a higher affinity for CO2 (the Haldane effect).

deranged specific answer for 2015 august Q23

Question 29

Partial pressure of CO2 in mixed venous blood depends on the CO2 content of the mixed venous blood, which in turn represents a balance between X

Answer 29

Partial pressure of CO2 in mixed venous blood depends on the CO2 content of the mixed venous blood, which in turn represents a balance between CO2 production in the tissues and the CO2 content in arterial blood.

examiner comment 2011 Q7

Question 30

. The partial pressure of CO2 is related to the CO2 content by the x

Answer 30

. The partial pressure of CO2 is related to the CO2 content by the CO2 dissociation curve, the position of which is determined by the state of oxygenation of haemoglobin, the Haldane effect

examiner comment 2011 Q7

Question 31

alveolar ventilation under the control of x

Answer 31

alveolar ventilation under the control of chemoreceptors and the brainstem respiratory centre.

examiner comment 2011 Q7

Question 32

23 Describe the factors that affect partial pressure of CO2 in mixed venous blood 2015 august and 2011 march

2011 Briefly describe the factors that affect the partial pressure of carbon dioxide
in mixed venous blood. 2015 august and 2011 march

Answer 32

2015 august Q23.
Describe the factors that affect the partial pressure of CO2 in mixed venous blood. 15 % of candidates passed this question.
/
It was expected candidates would define key concepts, particularly ‘mixed venous’. Many candidates knew some of the elements that contributed to mixed venous PCO2 but few described all of the main factors. There was little mention of tissue capillary flow as a factor affecting mixed venous CO2.

2011 march 7
Candidates were expected to provide a definition of important terms such as mixed venous. Many candidates provided much information about the partial pressure of carbon dioxide in arterial blood without discussing the factors which alter the mixed venous pressure. Partial pressure of CO2 in mixed venous blood depends on the CO2 content of the mixed venous blood, which in turn represents a balance between CO2 production in the tissues and the CO2 content in arterial blood. Good answers demonstrated an understanding of this and provided relevant details about these aspects. The partial pressure of CO2 is related to the CO2 content by the CO2 dissociation curve, the position of which is determined by the state of oxygenation of haemoglobin, the Haldane effect. CO2 production is related to aerobic metabolism in cells and total production is defined by the metabolic rate. Examples of increased and decreased CO2 production gained additional marks. The partial pressure of CO2 in mixed venous blood is related to the partial pressure or content of CO2 in arterial blood. This is determined mainly by alveolar ventilation under the control of chemoreceptors and the brainstem respiratory centre.

examiner comment 2011 Q7

Question 33

what desecribes: increased afterload causes an increased end-systolic volume, which increases the sarcomere stretch, and leads to an increase in the force of contraction

Answer 33

o The Anrep effect: increased afterload causes an increased end-systolic volume, which increases the sarcomere stretch, and leads to an increase in the force of contraction
o the Bowditch effect, or Treppe effect: with higher heart rates, the myocardium does not have time to expel intracellular calcium, so it accumulates, increasing the force of contraction.

deranged specific answer 2018 august Q18

Question 34

what is The Anrep effect?

Answer 34

o The Anrep effect: increased afterload causes an increased end-systolic volume, which increases the sarcomere stretch, and leads to an increase in the force of contraction
o the Bowditch effect, or Treppe effect: with higher heart rates, the myocardium does not have time to expel intracellular calcium, so it accumulates, increasing the force of contraction.

deranged specific answer 2018 august Q18

Question 35

What is the Bowditch effect, or Treppe effect

Answer 35

o The Anrep effect: increased afterload causes an increased end-systolic volume, which increases the sarcomere stretch, and leads to an increase in the force of contraction
o the Bowditch effect, or Treppe effect: with higher heart rates, the myocardium does not have time to expel intracellular calcium, so it accumulates, increasing the force of contraction.

deranged specific answer 2018 august Q18

Question 36

What describes: with higher heart rates, the myocardium does not have time to expel intracellular calcium, so it accumulates, increasing the force of contraction.

Answer 36

o The Anrep effect: increased afterload causes an increased end-systolic volume, which increases the sarcomere stretch, and leads to an increase in the force of contraction
o the Bowditch effect, or Treppe effect: with higher heart rates, the myocardium does not have time to expel intracellular calcium, so it accumulates, increasing the force of contraction.

deranged specific answer 2018 august Q18

Question 37

LV systolic function is a function of its x

Answer 37

LV systolic function is a function of its contractility.
Contractility = the change in force generated independent of preload

cicmwrekcs answer 2018 august Q18

Question 38

LV diastolic function:
LV diastolic function is determined by its x

Answer 38

LV diastolic function:
LV diastolic function is determined by its compliance. LV compliance is primarily determined by myocardial characteristics and load.

Factors affecting LV diastolic function:
Normal HR and rhythm
LV systolic function
Wall thickness
Chamber geometry
Duration, rate and extent of myocyte relaxation
LV untwisting and elastic recoil
Magnitude of diastolic suction
LA-LV pressure gradient
Passive elastic properties of LV myocardium
Viscoelastic effects (rapid LV filling and atrial systole)
LA structure and function

cicmwrekcs answer 2018 august Q18

Question 39

Describe the factors affecting left ventricular function
just read

Answer 39

Answers needed to consider intrinsic and extrinsic factors affecting LV function - the latter (e.g. SNS, PSNS, hormones, drugs) was often left out. Answers needed to consider both systolic and diastolic function. An excellent answer included physiological phenomena such as the Treppe effect, Anrep effect and baroreceptor and chemoreceptor reflexes. Mention of normal conduction and pacing as well as blood supply limited by diastole scored additional marks.

examiners comments 2018 august Q18

Question 40

just read
effects of aging on cardiovascular reserve

Answer 40

Recognition that aging reduces cardiovascular reserve followed up with an outline of the effects of aging on the heart, the vasculature, endothelial function and the conducting system would be rewarded with a good mark. Few answers quantified the decrease of cardiac output with age and only even fewer ventured into the contribution of ventricular filling by atrial systole. No answer discussed endothelial changes with aging

2015 march 19 examiner comment

Question 41

Definition of diastole

Answer 41

Definition of diastole
* Diastole is the period of chamber relaxation and cardiac filling which corresponds to
o The period between the end of the T wave and the end of the PR interval
o The period during which the mitral valve/tricuspid valves are open.

deranged 2018 March Q12

note: I think this is wrong, because it starts with isovolumetric relaxation which has no valves open

Question 42

What are the key poitns to talk about for; Briefly describe the cardiac events that occur during ventricular diastole

Answer 42

electrical/ionic events
coronary blood flow
mechanical events ( opening and closing of valves, blood movement)
ECG events

examiners comments 2018 March Q12

Question 43

Isovolumetric relaxation
Briefly describe the cardiac events that occur during ventricular diastole

Answer 43

• Isovolumetric relaxation
  o This period begi
  o The ventricles relax without any change in volume
  o The pressure drops until the tricuspid and mitral valves open
  o The beginning of this period corresponds to the peak of the T-wave, and the middle (steep portion) of Phase 3 (repolarisation) of the cardiac myocyte action potential
  o The end of this period corresponds to the end of the T wave on the surface ECG, and the end of Phase 3

deragned specific answer 2018 March Q12

(note: can only imagine this is supposed to say it begins with aortic valve closing)

Question 44

Briefly describe the cardiac events that occur during ventricular diastole
* Early rapid diastolic filling

Answer 44

• Early rapid diastolic filling
  o During this period the relaxing ventricles have pressure lower than atrial pressure, and they fill rapidly
  o 80% of the ventricular end-diastolic volume is achieved during this phase
  o Coronary blood flow is maximal during this phase

deragned specific answer 2018 March Q12

Question 45

Briefly describe the cardiac events that occur during ventricular diastole
* Late slow diastolic filling

Answer 45

• Late slow diastolic filling
  o Ventricular and atrial pressures equilibrate and the atria act as passive conduits for ventricular filling
  o The end of this phase corresponds to the end of the P-wave on the surface ECG

deragned specific answer 2018 March Q12

Question 46

Briefly describe the cardiac events that occur during ventricular diastole
* Atrial systole

Answer 46

• Atrial systole
  o The atria contract (right first, then left shortly after)
  o This increases the pressure in the ventricles up to the end-diastolic pressure, and adds about 20ml of extra volume to the end-diastolic volume
  o These events start at the end of the P-wave on the surface ECG, and finish during the PR interval.
  o The end of this phase corresponds to the peak of the R wave, or the Phase 0 (rapid sodium influx) of the ventricular myocyte action potential

deragned specific answer 2018 March Q12

note; it does make sense since this is the end of diastole and the beginning of systole (isovolumetric contraction) occurs at the R wave

Question 47

deranged 2018 march and 2011 march Briefly describe the cardiac events that occur during ventricular diastole

examiner comment

Answer 47

deranged 2018 march and 2011 march Briefly describe the cardiac events that occur during ventricular diastole

2018
12.Briefly describe the cardiac events that occur during ventricular diastole. 29% of candidates passed this question.
Many answers lacked structure and contained insufficient information. Better answers defined diastole and described the mechanical events in the 4 phases of diastole. A common error was the ECG events in diastole. The electrical events and coronary blood flow should have been mentioned.

2011 march
21. Briefly describe the cardiovascular events that occur during ventricular diastole.
One possible way to answer this question is to offer a definition of the diastolic period then to split the events up for description into mechanical events, ECG events and electrical/ionic events. Few candidates defined the diastolic period, and whilst many talked about opening and closing of valves, there was generally a poor understanding of the sequence of events whereby the left ventricle comes to be filled with blood. The better answers included a description of the ionic events that occurred at the various stages of diastole. Many answers lacked any reference to the ECG events in diastole. The major weakness in answers was again the failure to include sufficient information to achieve a pass mark. This was probably as a result of the lack of a systematic approach when answering a question of this nature. Syllabus: C1b, 2d,e and C1c, 2e,f Recommended sources: Textbook of Medical Physiology, Guyton & Hall, Chp 9 – 11 and Review of Medical Physiology, Ganong, Chp 31

Question 48

What are Baroreceptors?

Answer 48

o Baroreceptors are mechanoreceptors which respond to stretch stimuli.
o This strecth deforms mechanically sensitive sodium channels (DEG/ENaC, degenerin/epithelial sodium channels)
o With sufficient stimulus, sodium current increases to the point where the membrane potential reaches the threshold of local voltage-gated sodium channels, and generates a propagating action potential

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 49

Where are baroreceptors located?

Answer 49

o Arterial baroreceptors (“high pressure baroreceptors”) are located at the junction of the intima and media of the aortic arch and carotid sinuses
o Similar “low pressure” mechanoreceptors are present in the atria, and they mediate the Bainbridge reflex

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 50

what is the Bainbridge reflex

Answer 50

In short, giving volume increases the heart rate. This makes some sort of logical sense; as you increase the rate of flow into the ventricles, the rate of flow out of the ventricles should also increase, and there’s really only two ways this can happen (increase the stroke volume or increase the heart rate).

deranged Cardiac reflexes topic

Question 51

what is the stimulus for baroreceptors/

Answer 51

• Stimulus:
  o Increased blood pressure (increased stretch, increased receptor firing rate)
  o Decreased blood pressure (decreased receptor firing rate)

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 52

what is the afferent pathway for baroreceptors

Answer 52

• Afferent pathway:
  o From the carotid sinus: carotid sinus nerve, a branch of the glossopharyngeal nerve
  o From the aortic arch: aortic nerve, a branch of the vagus nerve
  o Both of these nerves travel through the jugular foramen to enter the medulla

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 53

what is the processor for baroreceptor??

Answer 53

Processor:
o Nucleus of the solitary tract receives afferent fibres and redistributes the signal into several efferent regulatory systems:
 Excitatory glutamate-mediated neurotransmission to the nucleus ambiguus translates the afferent signal into increased vagal activity
 GABA-ergic inhibitory neurons of the caudal ventral medulla translate the afferent signal into the inhibition of the rostral ventrolateral medulla, which coordinates sympathetic tone
 Effrent fibres to the hypothalamus help coordinate the humoural response to changes in blood pressure.

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 54

What is the efferent nerves, effector and the effect of baroreceptors?

Answer 54

• Efferent nerves:
  o Sympathetic fibres to the heart and peripheral resistance vessels
  o Vagal efferents to the cardiac ganglion (heart rate)
• Effector: Myocardium, SA and AV nodes, vascular smooth muscle
• Effect:
  o In response to arterial hypotension:
   Decreased receptor discharge rate
   Thus, decreased vagal and disinhibited sympathetic efferents
   Thus, systemic vasoconstriction and tachycardia
  o In response to arterial hypertension:
   Increased receptor discharge rate
   Thus, increased vagal and inhibited sympathetic efferents
   Thus, systemic vasodilation and bradycardia

deranged specific answer to Describe baroreceptors and their role in the control of blood pressure. 2014 aug Q16 and 2007 aug

Question 55

Baroreceptor examiner comment, just read

Answer 55

Baroreceptors are stretch receptors located in the walls of the heart and blood vessels and are important in the short term control of blood pressure. Those in the carotid sinus and aortic arch monitor the arterial circulation. Others, the cardiopulmonary baroreceptors, are located in the walls of the right and left atria, the pulmonary veins and the pulmonary circulation. They are all stimulated by distention and discharge at an increased rate when the pressure in these structures rises. Better answers provided some detail on the innervation for these receptors. It was expected candidates would describe that increased baroreceptor discharge inhibits the tonic discharge of sympathetic nerves and excites the vagal innervation of the heart. This results in vasodilation, venodilation, a drop in blood pressure, bradycardia and a decreased cardiac output. Some candidates had a major misunderstanding around the purpose of “low pressure baroreceptors” with many believing that these are the ones that respond to lower blood pressures, while the “high pressure baroreceptors” respond to higher blood pressures.

• description of, and types of, baroreceptors (e.g. stretch-receptors)
• their locations (e.g. walls of the aorta, carotid sinuses, the atria etc)
• the stimulus they respond to (e.g. pressure, volume)
• short term and long term responses, alteration to set points, impulse frequency / pressure curve
• a brief description of the afferent and efferent pathways and the resultant efferent effects (e.g. alterations to heart rate, blood pressure, etc)

examiner comment 2014 aug Q16 and 2007 aug