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Flashcards in Physiology Deck (38):
1

The macula densa tissue is situated here.

Distal convoluted tubule
The macula densa is a tissue that is found on the distal convoluted tubule, and sits at the hilum of the Bowman's capsule. Its role is to monitor blood flow into the capsule, and hence it is involved in blood pressure control.

2

Ninety five percent of glucose is reabsorbed in this region.

Proximal convoluted tubule
Glucose should be completely reabsorbed from the urine in the kidneys, and if not, usually demonstrates diabetes mellitus.


3

Glomerular filtration occurs here.

Bowman's capsule
Glomerular filtration occurs in the Bowman's capsule. Water leaves the descending thin limb of the loop of Henle by diffusion. This is because of the high solute potential around the descending limb caused by active transport of sodium and chloride from the ascending limb.

4

Water leaves this via diffusion.

Descending thin limb

5

Aldosterone mainly acts on this region.

Distal convoluted tubule
Aldosterone, involving in solute balance, mainly acts on the distal convoluted tubule.

6

A 32-year-old lady is brought to the neurosurgical ward after a subarachnoid haemorrhage is confirmed on CT scan. A small middle cerebral artery aneurysm is subsequently embolised.
She later becomes drowsy and less responsive. A repeat CT head shows hydrocephalus and high cerebral spinal fluid (CSF) pressure is confirmed with an opening pressure of 26 cmH20 on lumbar puncture.
Roughly what is the normal circulating volume of CSF in an adult?
(Please select 1 option)
20mls
50 mls
150 mls
500 mls
1000 mls

150mls
This patient's hydrocephalus is caused by an interruption in circulating CSF reabsorption secondary to the bleed.

The normal volume of CSF is approximately 150 mls, although the body will make approximately 500 mls per day.

CSF is produced mainly by the choroid plexus. It flows from the lateral ventricles into the third and then fourth ventricles. It then reaches the subarachnoid space. It is reabsorbed into the venous circulation by the arachnoid villi.

7

A young man is a victim of a mugging but manages to escape his attackers and seeks police assistance. He is brought to the emergency department appearing pale but with no apparent injury.
Which of the following is not likely to be contributing to the patient's appearance?
(Please select 1 option)
Angiotensin II
Endothelin
Epinephrine
Nitric oxide
Thromboxane

Nitric oxide is a vasodilator whereas the other chemicals listed are all vasoconstrictors.

Activation of the sympathetic nervous system such as the scenario described leads to vasoconstriction.

In addition there will be

Papillary dilatation
A tachycardia and bronchodilatation.
Other vasoconstrictors include

Vasopressin
Superoxide radicals and
Norepinephrine.

8

Nitric oxide is a multifunctional compound which plays a number of roles in haemostasis.
Which of the following is a role of nitric oxide?
(Please select 1 option)
Inhibition of plasminogen activating inhibitor-1
Inhibition of platelet aggregation
Inhibition of sino-atrial node
Oxidation of LDL
Vasoconstriction

Inhibition of platelet aggregation
Nitric oxide is actually a potent vasodilator, acting through guanylate cyclase which converts guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP) within smooth muscle cells leading to smooth muscle relaxation.

Free radical generation is important in host defence mechanisms.

Nitric oxide prevents platelet aggregation and monocyte adhesion thus localising clot formation.

9

A 42-year-old woman is seen in the endocrine clinic and following investigation is diagnosed with Conn's syndrome.
Which of the features listed below is a typical finding in the diagnosis?
(Please select 1 option)
Elevated renin
Hyperglycaemia
Hyperkalaemia
Metabolic alkalosis
Reduced urinary potassium excretion

Metabolic alkalosis

In Conn's syndrome primary hyperaldosteronism, the elevated aldosterone levels suppress renin production and so plasma rennin will be low.

Measurement of both aldosterone and renin confirm the diagnosis.

Hyperaldosteronism also leads to a metabolic alkalosis and muscle cramps.

10

In relation to the oxygen dissociation curve, which of the following factors shifts the curve to the right?
(Please select 1 option)
Carbon monoxide poisoning
Fall in 2,3 DPG
Fall in pH
Fall in temperature
Rise in pH

Fall in pH

The reduced affinity of haemoglobin for oxygen as the pH falls is known as the Bohr effect. This leads to the delivery of O2 to tissues at a lower partial pressure of O2.

Other factors causing a right shift include a rise in 2,3-biphosphoglycerate (2,3-DPG) or pCO2 (the pH of blood falls as its CO2 content rises) and a rise in intracellular adenosine triphosphate (ATP).

All the other options listed are associated with a shift in the curve to the left and hinder oxygen delivery.

11

Which of the following is correct regarding angiotensin II?
(Please select 1 option)
Decreases aldosterone production
Is a decapeptide
Is a vasodilator
Is formed mainly in the kidney
Is produced when the circulating blood volume is reduced

Is produced when the circulating blood volume is reduced This is the correct answerThis is the correct answer
Angiotensin II is a potent vasoconstrictor, and is also responsible for the generation of aldosterone.

Angiotensin is an octapeptide.

Angiotensinogen is a plasma protein that gives rise to angiotensin I and then angiotensin II catabolised by angiotensin-converting enzyme (ACE) (mostly in the lungs).

Its production is induced with reduced circulating blood volume, hypotension, reduced sodium, etc.

12

In a normal adult woman weighing 60 kg which of the following is true about the extracellular fluid (ECF)?
(Please select 1 option)
Contains no protein
Forms a greater proportion of the total body weight in the obese than in the lean woman
Has a sodium concentration of 125-135 mmol/L
Has a total volume of about 12 litres
Is isotonic throughout the body

Has a total volume of about 12 litres

Total body water is about 60% of body weight (50% to 70% depending on how much fat is present). In the obese ECF is relatively contracted.

In this person total body water is approximately 36 litres (0.6 × 60), of which 1/3 is ECF (12 litres) and 2/3 (24 litres) intracellular fluid.

The simple rule is 60-40-20.

Normal sodium concentration is approximately 135-145 mmol/L.

ECF is composed of intravascular fluid and extravascular fluid. Both contain plasma proteins.

13

Which of the following does not affect resistance to flow in a blood vessel?
(Please select 1 option)
Haematocrit
Length of the vessel
Pressure
Radius of the vessel
Thickness of the vessel wall

Thickness of the vessel wall This is the correct answerThis is the correct answer
This question refers to Poiseuille's Law.

R = P/Q = 8nl/r4, where

P is the pressure gradient along the vessel
Q is the volume flow rate
r is the radius of the vessel
n is the viscosity (haematocrit) of the blood
l is the length of the blood vessel.
Thickness of the vessel wall does not affect blood flow, but the stiffness of the vessel wall does affect blood flow.

14

With respect to exercise, which of the following is true?
(Please select 1 option)
An increase in muscle blood flow begins after the first half minute of exercise
Body temperature may rise measurably
Cerebral blood flow increases if the exercise causes systolic arterial blood pressure to rise
Lymph flow from the exercising muscles decreases
Visceral blood flow increases

Body temperature may rise measurably

Exercise produces an increase in heart rate, blood pressure and muscle blood flow (after at least a minute).

Cerebral blood flow is, however, very closely controlled and is generally stable. It increases in response to increased CO2.

Capillary pressure and surface area are increased therefore more fluid leaves the bloodstream. Muscle action assists the movement of lymph.

Visceral blood flow decreases due to sympathetic increased activity with the diversion of blood to the exercising muscles.

15

Which of the following is true regarding carotid sinus baroreceptors?
(Please select 1 option)
As the blood pressure increases the discharge from these receptors is reduced
In chronic hypertension the baroreceptors reflex is reset
Similar receptors are located in the right atria
They are innervated by the carotid sinus nerve, which is a branch of the vagus
They can be found in the external carotid artery distal to the carotid body

In chronic hypertension the baroreceptors reflex is reset

The carotid sinus baroreceptors are stretch receptors (not pressure) that control blood pressure and heart rate by a feedback mechanism.

They are located in the internal carotid artery, distal to the carotid bifurcation but proximal to the carotid body, (the latter arises from the external carotid artery). Similar baroreceptors are found in the aortic arch, atria and left ventricle.

The carotid sinus nerve, which is a branch of the ninth cranial nerve, receives afferent fibres from the carotid sinus and carotid body, and ascends to the vasomotor centre.

As the distending pressure in the artery increases, the discharge rate from the baroreceptors increases, which stimulates the cardioinhibitory centre, causing a fall in blood pressure, heart rate and cardiac output.

In chronic hypertension, in order to maintain an elevated blood pressure, the reflex mechanism is reversibly reset.

16

Regarding a reduced arterial PCO2, which of the following statements is true?
(Please select 1 option)
Increases cerebral blood flow
Leads to a more acidic urine
Occurs at altitudes under 4,500 metres
Occurs in normal pregnancy
Reduces blood pH

Occurs in normal pregnancy

Reduced pO2 may be seen:

in the later stages of pregnancy
at altitude
in type 1 respiratory failure (emphysema, pulmonary embolism [PE])
in type 2 respiratory failure (muscle disease, chronic bronchitis), and
in methaemoglobinaemia.
Increased pCO2 increases cerebral blood flow and also increases acidity (respiratory acidosis) which in turn leads to urine which is more acid.

Reduced PCO2 occurs in:

normal pregnancy
hyperventilation
emphysema
PE, and
mild to moderate asthma.

17

Which of the following is true in a normal muscle fibre?
(Please select 1 option)
Calcium reuptake is a passive process
Muscle contraction is terminated by the efflux of calcium out of the sarcolemma
The action potential lasts 10 ms (milliseconds)
The resting membrane potential is -10 mV (minus 10 millivolts)
Troponin allows actin to cross link with myosin

Troponin allows actin to cross link with myosin This is the correct answerThis is the correct answer
The normal resting membrane potential is -90 mV.

Motor neurone stimulation depolarises the sarcolemma via the end-plate (the action potential lasting 2-4 ms), and calcium ions are released from the sarcoplasmic reticulum (SR).

The calcium ions bind to troponin, which results in the tropomyosin moving to reveal the myosin binding site on the actin filament.

Cross-bridge formation is energy dependent (ATP), and is inhibited by low sarcoplasmic calcium ion concentrations.

Muscle relaxation occurs by the re-uptake of calcium ions by the SR (not efflux out of the SR) and is an active process.

18

Which of the following factors shift the oxygen dissociation curve (ODC) to the left?
(Please select 1 option)
Adult haemoglobin
Anaemia
Haemoglobin S
Hypercapnoea
Methaemoglobinaemia

Methaemoglobinaemia This is the correct answerThis is the correct answer
Fetal haemoglobin, methaemoglobin and carboxyhaemoglobin all shift the curve to the left.

Haemoglobin S shifts the curve to the right.

Anaemia affects the quantity not the characteristics of the haemoglobin.

The curve is only altered if oxygen content, not saturation, is plotted on the y axis.

19

Which one of the following is correct concerning the pituitary?
(Please select 1 option)
An oral glucose tolerance test is used to assess anterior pituitary function
LH and FSH are secreted by different cells
LH, FSH and TSH share the same common alpha subunit
The anterior pituitary secretes oxytocin
The most common cell type in the pituitary is a prolactin secreting cell

LH, FSH and TSH share the same common alpha subunit

The pituitary is composed of the anterior (luteinising hormone [LH], follicle-stimulating hormone [FSH], growth hormone [GH], thyroid-stimulating hormone [TSH], prolactin [PRL] and [adrenocorticotropic hormone] ACTH) and posterior components (oxytocin and antidiuretic hormone [ADH]), and is controlled through hypothalamic regulatory hormones, controlled in turn by negative feedback.

Gonadotrophs secrete LH and FSH. The alpha subunits of both LH/FSH and TSH are identical.

The commonest cell type in the pituitary is the somatotroph - GH producing cells.

The commonest pituitary tumour is the prolactinoma - particularly microprolactinomas - common in females and treated with dopamine agonists.

The anterior pituitary function is assessed through the insulin tolerance test.

20

Which of the following is correct concerning free radicals?
(Please select 1 option)
A free radical contains no unpaired electrons
A hydroxyl free radical is the least reactive free radical
Free radical damage is implicated in aneurysm formation
Free radicals are formed through anaerobic metabolism
Nitric oxide is a free radical

Nitric oxide is a free radical This is the correct answerThis is the correct answer
Free radicals are molecules that contain one or more unpaired electrons. They are formed from aerobic metabolism and include

Superoxide
Hydroxyl ions
Nitric oxide.
They are implicated in disease processes such as atherosclerosis as well as many inflammatory conditions and disorders such as adult respiratory distress syndrome (ARDS).

The pathophysiology of aneurysm disease is most likely to be due to up-regulation of elastases in the vessel wall.

21

Following severe haemorrhage, which of the following does not occur?
(Please select 1 option)
Excretion of sodium in the urine is markedly decreased
Plasma urea concentration rises
Secretion of both ADH and aldosterone increase
The tonicity of the extracellular fluid is increased
Urine osmolality increases

The tonicity of the extracellular fluid is increased
The loss of isotonic fluid (such as blood/plasma) from the body does not lead to any change in tonicity of the body fluids, but leads to a change in volume (isotonic contraction).

As a consequence of the reduced blood volume, there is increased secretion of both ADH and aldosterone, and this in turn increases sodium reabsorption from the urine and also increased urine concentration - osmolality.

With severe haemorrhage there may be a large fall in the glomerular filtration rate (GFR), causing retention of urea and an increase in plasma urea due to under perfusion of the kidney (pre-renal failure).

22

Which of the following is an uncommon feature of metabolic acidosis?
(Please select 1 option)
High hydrogen ion concentration
High pCO2 concentration
Hyperkalaemia
Hypernatraemia
Low plasma bicarbonate concentration

High pCO2 concentration

A metabolic acidosis is associated with a low pH and hence high plasma hydrogen ion concentration.

As a buffering system, HCO3 is typically reduced and PCO2 is decreased in an effort to compensate and induce a respiratory alkalosis. Similarly, there is increased renal excretion of hydrogen ions with potassium excretion.

The increased hydrogen concentrations are also responsible for an efflux of potassium from the intracellular reservoir.

23

The oxygen-haemoglobin dissociation curve may be shifted to the right in which of the following conditions?
(Please select 1 option)
Carbon monoxide poisoning
Decrease in PCO2 concentration
Fall in temperature below 37°C
Increase in 2,3-DPG
pH increasing to 7.48

Increase in 2,3-DPG

The oxygen-haemoglobin dissociation curve is a graph that shows the per cent saturation of haemoglobin at different partial pressures of oxygen.

The normal oxygen-haemoglobin dissociation curve is said to be at equilibrium when

The pH is 7.40
The PCO2 is 40 mmHg
The 2,3-diphosphoglycerate (2,3-DPG) concentration is 15 µmol/g Hb
The temperature is 37°C.
Any alteration in these four physiological factors may result in a change in affinity of the haemoglobin for oxygen and thus the shape of the curve.

An increase in temperature (denatures the bond between oxygen and haemoglobin thus decreasing the concentration of oxyhaemoglobin), increase in CO2 concentration, increase in 2,3-DPG (2,3-DPG binds to haemoglobin which rearranges the haemoglobin into the T-state, thus decreasing the affinity of oxygen for haemoglobin) or a fall in pH (due to the Bohr effect) causes a reduction in the affinity of haemoglobin for oxygen.

All these factors cause a deviation of the curve to the right. Similarly, a decrease in the temperature, a decrease in CO2 concentration, a decrease in 2,3-DPG, or a rise in pH increases the affinity of haemoglobin for oxygen. This causes a shift of the oxygen-haemoglobin dissociation curve to the left.

Carbon monoxide poisoning shifts the curve to the left due to the inhibition of synthesis of 2,3-DPG.

24

Which of the following is correct regarding 2,3-diphosphoglycerate (2,3-DPG)?
(Please select 1 option)
Causes an increase in the affinity of the haemoglobin molecule for oxygen
Is principally manufactured in the liver
Is produced through the hexose monophosphate shunt
Production is decreased in heart failure
Production is increased in primary polycythaemia

Is produced through the hexose monophosphate shunt

2,3-DPG (http://www.gpnotebook.com/simplepage.cfm?ID=-684392408) is created in erythrocytes during glycolysis.

The production of 2,3-DPG is likely an important adaptive mechanism, because the production increases for several conditions in the presence of diminished peripheral tissue O2 availability, such as

Hypoxaemia
Chronic lung disease
Anaemia
Congestive heart failure.
High levels of 2,3-DPG shift the curve to the right, while low levels of 2,3-DPG cause a leftward shift, seen in states such as septic shock and hypophosphataemia.

25

Which of the following is correct regarding the digestive system?
(Please select 1 option)
Fructose is mainly absorbed by simple diffusion
Glucose transport into the cell depends upon the active transport of sodium ions
Lactase activity increases during childhood
One molecule of sucrose forms two molecules of glucose
Polysaccharides are broken down mainly in the small intestine

Polysaccharides are broken down mainly in the small intestine This is the correct answerThis is the correct answer
Polysaccharides are broken down mainly in the small intestine.

Glucose is a monosaccharide and sucrose are disaccharides (glucose + fructose).

Glucose/fructose enters most cells by facilitated diffusion and is dependent upon glucose-transporting proteins.

Expression of the lactase enzyme starts to decrease in most humans at the age of two years.

26

Which of the following is correct in blood pressure regulation?
(Please select 1 option)
Adrenaline acts primarily on the vasomotor centre
Angiotensinogen is inactive without modification
Bradykinin increases blood pressure
Prostacyclin raises blood pressure
Serotonin is a vasodilator

Angiotensinogen is inactive without modification

Circulating hormones such as adrenaline and angiotensin II (which is converted from angiotensin I, which itself is converted from angiotensinogen via the renin-ACE conversion pathway) are potent vasoconstrictors, but they probably have little effect on acute cardiovascular control.

In contrast, endothelium-derived factors play an important role in controlling local blood flow. These substances are either produced or modified in the vascular endothelium, and include prostacyclin and nitric oxide, both potent vasodilators.

Bradykinin is known to be vasodilatory and hence has a hypotensive effect.

Serotonin causes vasoconstriction, which is why selective serotonin reuptake inhibitors (SSRIs) can cause hypotension as a side effect.

27

Which of the following physiological changes may occur during a laparoscopic procedure in a fit patient?
(Please select 1 option)
Alteration in the left ventricular function
An increase in cardiac output secondary to direct pressure on the inferior vena cava and pelvic veins
Decrease in the systemic vascular resistance by a combination of mechanical pressure on the aorta and splanchnic vessels, and release of catecholamines
Reduction in the renal blood flow and glomerular filtration rate (GRF) due to decreased vasopressin levels
Release of inflammatory mediators as a direct result of afferent neuronal stimulation from the peritoneum

Release of inflammatory mediators as a direct result of afferent neuronal stimulation from the peritoneum

Peritoneal insufflation with or without Trendelenburg position may result in an increase in systemic vascular resistance (and therefore rise in mean arterial blood pressure) by mechanical compression of the aorta and splanchnic vessels, and the release of catecholamines, prostaglandins, renin and vasopressin.

Direct pressure on the inferior vena cava and pelvic veins leads to decreased venous return, and therefore a fall in cardiac output. (This effect may be to some extent compensated for by blood entering the central vascular space from the inferior vena cava and splanchnic bed.)

Increased renal vascular resistance, decreased cardiac output and elevated vasopressin levels all lead to a fall in renal blood flow and GFR. Left ventricular function is unaltered in fit patients.

The metabolic response to laparoscopic surgery (mediated by neuroendocrine stimulation and release of inflammatory mediators) may be caused by afferent neuronal stimulation from the peritoneum.

28

Which one of the following physiological changes does not occur in a fit patient undergoing a laparoscopic procedure?
(Please select 1 option)
Alteration in intrathoracic blood volume
Collapse of small airways, which may lead to atelectasis
Decreased functional residual capacity (FRC), due to diaphragmatic displacement and splinting
Increase in end-tidal CO2 and arterial PaCO2 during insufflation
Significant alteration in gas exchange, partly due to a reduction in lung compliance

Significant alteration in gas exchange, partly due to a reduction in lung compliance

During laparoscopic procedures the FRC is decreased by diaphragmatic displacement and splinting.

Changes in intrathoracic blood volume develop as a result of pneumoperitoneum and Trendelenburg positioning. These changes may give rise to

Collapse of small airways
Atelectasis
Pulmonary shunting
Hypoxia.
Diaphragmatic displacement also causes a reduction in total lung compliance (up to 50%).

CO2 insufflation leads to a rise in end-tidal CO2 and arterial PaCO2.

Despite all these changes, only minor modifications in gas exchange result, unless there is pre-existing cardiopulmonary disease.

29

Which of the following is correct concerning cerebrospinal fluid?
(Please select 1 option)
Containing blood increases reabsorption
Is produced at approximately 300 ml / hr by the choroid plexus
Is reabsorbed by arachnoid granulations in the superior sagital sinus
Lies in the subdural space
Proceeds from the lateral ventricles via the foramen of Monro into the fourth ventricle

Is reabsorbed by arachnoid granulations in the superior sagital sinus

Cerebrospinal fluid is produced at a rate of approximately 30ml/hr by the choroid plexus which is primarily located in the lateral ventricles.

It then passes from the lateral ventricles via the foramen of Monro to the third ventricle and then the aqueduct of sylvius into the fourth ventricle.

On leaving the ventricular system it enters the subarachnoid space, overlying the brain and spinal cord. The arachnoid granulations in the superior sagital sinus reabsorb it back into the venous circulation.

Plugging of these granulations impairs reabsorption raising intra cranial pressure, causing communicating hydrocephalus.

30

Haemorrhage produces which of the following?
(Please select 1 option)
An increase in cardiac output
Causes splenic contraction
Increased aldosterone secretion
Vasodilitation
Widespread arteriolar dilatation

Increased aldosterone secretion

Haemorrhage produces both venous and arteriolar contraction.

Cardiac output is initially reduced.

Hypovolaemia increases aldosterone secretion.

Renal reabsorption of sodium is increased and volume homeostasis is eventually achieved.

Unlike carnivores, the human spleen does not act as a significant reservoir of red blood cells and does not contract in response to blood loss.

31

In the human being, haemorrhage does not cause which of the following?
(Please select 1 option)
A fall in cardiac output
Decreased blood flow to the skin
Increased aldosterone secretion
Splenic contraction
Venous constriction

Splenic contraction

Venous constriction is a compensatory response to avoid further blood loss.

In haemorrhage blood is diverted to the 'essential organs' such as the brain and lungs at the expense of other peripheral organs such as the skin.

A fall in cardiac output is in conjunction with Starling's law.

Splenic contraction may occur in carnivores but not in humans in response to haemorrhage as it is not a reservoir.

By increasing aldosterone secretion, salt and water retention is increased, which expands the intravascular volume as a compensatory response to blood loss.

32

Which of the following is true regarding burning pain sensation?
(Please select 1 option)
Arises from stimulation of Golgi organs
Is reduced by local anaesthetics through reduction of the potassium influx into the nerve fibres
Is transmitted to the brain via the corticospinal tracts
Is transmitted to the central nervous system (CNS) by Aδ fibres
Is transmitted to the thalamus

Is transmitted to the thalamus This is the correct answerThis is the correct answer
The sense organs for pain are the naked nerve endings found in almost every tissue of the body.

Pain impulses are transmitted to the CNS by two fibre systems, which are myelinated AƒÔ fibres and unmyelinated C fibres.

The A delta fibres (Aδ fibre) conduct cold and pressure impulses.

The pain sensation is transmitted to the brain through the lateral spinothalamic tracts.

Local anaesthetics reduce the pain sensation by inhibiting the fast Na+ response.

Many fibres activated by pain end in the reticular system, which projects to the midline and intralaminar non-specific projection nuclei of the thalamus.

33

Compared with intracellular fluid, extracellular fluid has which of the following?
(Please select 1 option)
Greater osmolarity
Higher potassium ion concentration
Higher protein concentration
Lower chloride ion concentration
Lower hydrogen ion concentration

Lower hydrogen ion concentration This is the correct answerThis is the correct answer
Extracellular fluid has a lower osmolarity compared to intracellular fluid.

Intracellular fluid has a protein concentration of 55 mmol/L, whilst that of extracellular fluid is 16 mmol/L.

Intracellular fluid has a low [Cl-] whilst the extracellular fluid has a high [Cl-] with 102 mmol/L in plasma and 114 mmol/L in the interstitial fluid.

Intracellular fluid has a higher [H+] than extracellular fluid due to cellular metabolism.

The intracellular [K+] is 160 mmol/L whilst that of the extracellular fluid is about 4 mmol/L.

34

Which of the following is true at birth?
(Please select 1 option)
Pulmonary vascular resistance rises
Systemic vascular resistance falls
The cardiac output averages 5 litres per minute
The opening between the two ventricles closes
There is a reversal of flow in the ductus arteriosus

There is a reversal of flow in the ductus arteriosus This is the correct answerThis is the correct answer
When the umbilical cord is clamped, the umbilical vein closes, systemic vascular resistance is increased and this causes the ductus venosus to close.

At birth the lungs are aerated, acutely lowering the pulmonary vascular resistance.

The ductus arteriosus constricts in a response to the rising oxygen tension, thus preventing the blood from the aorta and pulmonary artery from mixing.

There is no opening between the two ventricles.

The foramen ovale is the anatomical opening between the right atrium and left atrium that closes shortly after birth.

The cardiac output for an adult is 5 litres a minute.

35

Which of the following are true regarding nerve fibre?
(Please select 1 option)
Motor function and proprioception is carried by class A-alpha fibres
Motor function to muscle spindles is provided by class C fibres
Pain, cold sensation is carried by class A-beta fibres
Postganglionic fibres are myelinated
Preganglionic autonomic fibres are unmyelinated

Motor function and proprioception is carried by class A-alpha fibres

Class A-alpha fibres provide motor function and proprioception sensation.

Class A-beta fibres carry touch and pressure sensation.

Class A-gamma fibres provide motor function to muscle spindles.

Class A-delta fibres carry pain, cold and touch sensation.

Myelinated class B nerves are autonomic preganglionic fibres.

Unmyelinated class C nerves are autonomic postganglionic fibres which also carry pain and temperature sensation.

36

Which of the following increase cerebral blood flow?
(Please select 1 option)
Acute anaemia
Inhalation of carbon monoxide
Inhalation of hyperbaric oxygen
Raised intracranial pressure
Seizures

Seizures This is the correct answerThis is the correct answer
It is likely that there is a rebound arterial dilation after hyperbaric oxygen therapy, resulting in an increased blood vessel diameter greater than when therapy began, thus improving blood flow to compromised organs.

Hyperbaric oxygen therapy has been shown to diminish cerebral blood flow by between 1-29%.

37

If one carries out a Valsalva manoeuvre against a closed glottis, which one of the following will occur?
(Please select 1 option)
A fall in heart rate
A rise in blood pressure
A rise in intrathoracic pressure
A rise in left ventricular output
A rise in right ventricular output

A rise in intrathoracic pressure

Owing to increased intrathoracic pressure there is a fall in right ventricular output because of decreased venous return to the heart.

There is therefore a fall in left ventricular output and a concomitant fall in blood pressure.

38

Bilateral gynaecomastia in a male aged 24 who underwent normal puberty at 14 years of age could be due to which of the following?
(Please select 1 option)
Primary hypothyroidism
Prostatic carcinoma
Ranitidine therapy
Testicular teratoma
Tobacco smoke

Testicular teratoma

Gynaecomastia is caused by an imbalance between testosterone and oestrogen.

This may occur with teratoma and cannabis is associated with alteration of sex hormone binding globulin.

Unlike cimetidine, ranitidine does not produce gynaecomastia.

Prostate carcinoma per se does not cause gynaecomastia but the induction of hypogonadism as treatment does.

Hyperthyroidism not hypothyroidism is associated with gynaecomastia.