Paper 2 Flashcards
(46 cards)
Describe the arterial blood supply to the two (2) speech areas (Broca’s and Wernicke’s) of the brain,
starting with the brachiocephalic trunk. You may use a well-labelled diagram for your answer.
The left common carotid artery (✓) branches into the left external (✓) and internal (✓) carotid artery. The left
internal carotid artery enters the cranial cavity through the carotid foramen (✓) and branches first into the left anterior
cerebral (✓) artery before continuing as the left middle cerebral artery (✓). The middle cerebral artery branches into
superior and inferior divisions which supply Broca’s and Wernickes area respectively.
Outline how the differences in pitch (frequency) of sound waves are detected in the cochlea of
the inner ear and name the sensory structure and cell type involved in detection of acoustic
stimuli
Tonotopic organization of the cochlea: low frequencies excite cells at apex of cochlea, high
frequencies at the basis. Organ of Corti, Hair cells
List the major functional differences between the rod and cone photoreceptor systems in the
human eye.
High vs low sensitivity; sensitivity to most of the spectral range of visible light vs. selective
sensitivity – “red”, “green”, “blue” cones; generation of low definition vs high definition image
Outline the structural features that distinguish the Blind Spot from other parts of the neural
retina.
No photoreceptor cells and other neuronal cell bodies; exit point of optic nerve/retinal ganglion cell
axons
Name the anatomical structure that contains the cell bodies (somata) of primary
somatosensory neurons, and state how these neurons are classified in terms of their
morphology.
Spinal/dorsal root ganglion; pseudo-unipolar
Describe the mechanism by which the cerebellum is able to correct for motor signal errors and how
synaptic plasticity within the cerebellum circuitry contributes to motor learning.
The mossy fibre inputs to the cerebellum convey the sensory information used to evaluate the overall
sensory context of the movement. (1 mark)
The error signal is believed to be conveyed by the climbing fibre inputs. (1 mark)
Climbing fibres are known to be especially active when an unexpected event occurs, e.g. when a greater
load than expected is placed on a muscle. (1 mark)
The large divergence of input from the mossy fibres to the granule cells to the parallel fibres is believed to
create complex representations of the entire sensory context and the desired motor output. (1 mark)
When the desired output is not achieved, the climbing fibres signal this error and trigger a calcium spike in
the Purkinje cell. (1 mark)
The influx of calcium changes the synaptic connection strengths (plasticity) between parallel fibres and
Purkinje cells (1 mark).
This pairing of climbing fibre activation and parallel fibre activity leads to long-term depression of Purkinje
cell responses to parallel fibres, such that the next time the same behavioural context occurs, the motor
output will be modified to more closely approximate the desired output. (1 mark)
Primary hyperaldosteronism is a cause of hypertension.
a. List the biochemical findings associated with this condition.
List the biochemical findings associated with this condition:
* Hypernatremia (½)
* Alkalosis (½)
* Hypokalaemia (½)
List the hormonal findings associated with this condition.
List the hormonal findings associated with this condition:
* Low renin (1)
* High aldosterone (1)
Briefly outline the reason for the biochemical findings listed in question 52.
Increased aldosterone activity via the mineralocorticoid receptor → increased incorporation of epithelial
sodium channels [1] into apical membrane in distal renal tubules → increased sodium uptake (along with
water) [1], accompanied by renal loss of potassium [1] and hydrogen ions
Is there likely to be a genetic component to Mr Harvey’s stroke (½ mark), and how would you
answer his wife’s question about the risk to their daughters.
Yes – diabetes, hypertension and dyslipidaemia are all multifactorial conditions with a significant genetic
component and the fact that his 2 brothers had IHD at an early age suggest a stronger genetic component
link. As multifactorial disorders are the combination of many small genetic contributions and environment
that unless a specific single gene disorder is suggested by the clinical phenotype, genetic test are not
particularly helpful yet. Her daughters or have a somewhat higher risk so should undergo screening for
these disorders and maintain a healthy lifestyle including not smoking but a direct to consumer genetic
‘risk” test is not likely to be very helpful to them.
Is Mr Harvey’s pregnant daughter also at risk of having a baby with haemophilia A (½ mark).
Explain your answer.
Yes – her sister must be a carrier so Mrs Harvey is an obligate carrier – the older sister therefore is at 50%
risk of being a carrier so her son has a 25% risk of having haemophilia A (father not relevant to the baby
boy)
State what the risk is that the two year girl is a carrier for haemophilia A.
100%
From a public health perspective, list the type/s of prevention that should be focussed on for stroke.
Briefly explain your answer.
Most (>90%) of stroke burden is attributable to modifiable risk factors
Most of the risk factors are preventable
And achieving control of behavioural and metabolic risk factors could avert more than three-
quarters of the global stroke burden
Therefore primordial and primary prevention (2 marks)
Give a concise definition of “threshold” as applied to somatosensory cutaneous mechanoreceptors
Answer: in the somatic sensory system, “threshold” is the strength of mechanical deformation necessary for
producing a generator potential of sufficient amplitude to elicit an action potential.
Identify whether the Merkel cell is a rapidly or slowly-adapting cutaneous mechanoreceptor.
slowly-adapting receptor’
Describe how the Merkel complex converts a mechanical stimulus into an electrical signal in the afferent
neuron.
the Merkel cell is coupled to the surrounding tissue and cannot shift its position relative to the
surrounding tissue. Consequently, a force applied to the overlying skin distorts the Merkel cell for the
duration of the applied force. The distortion of the Merkel cell results in the release of a steady stream of
neuropeptides at its synaptic junctions with the primary afferent neuron. As a result the action potential
discharges produced by the Merkel complex primary afferent is slowly adapting.
List two (2) possible life threatening macrovascular diseases that Mr Abrahams is at risk of
developing if he doesn’t maintain an appropriate glucose control.
- Myocardial infarction
- Stroke/CVA
In addition to his ulcer and decreased sensation in his feet, list two (2) other end organs that are at
risk and state how you would screen for microvascular disease in each of them
- Kidney (½) /(diabetic nephropathy) – urine dipstix / urine microalbumin(½)
- Retina (½) (diabetic retinopathy) – fundoscopy (½)
Briefly explain why an increased prolactin is a common feature of primary hypothyroidism.
Reduced negative feedback → increased TRH → TRH has a stimulatory effect on prolactin
Match the single most likely thyroid hormone pattern (a – d) associated with the clinical diagnosis
listed (1 – 4) in the table below
a. Normal free T4, decreased TSH
b. Increased free T4, increased TSH
c. Decreased free T4, increased TSH
d. Increased free T4, decreased TSH
Thyroid hormone resistance b
2. Untreated primary hypothyroidism c
3. Subclinical hyperthyroidism a
4. Molar pregnancy producing excessive
amounts of hCG
d
Outline a cause for a falsely decreased level of HbA1c.
Anything that reduces red cell life span like spherocytosis
Outline what happens to extracellular potassium when insulin is administered.
It moves intracellularly and EC levels can decrease.
List three (3) counter-regulatory hormones that increase blood glucose and state what kind of
hormone they are (peptide/steroid/amino acid derivative).
Adrenaline – amino acid
Cortisol – steroid
GH – peptide
Glucagon – peptide
Define haemopoeitic growth factors.
Haemopoeitic growth factors are soluble glycoprotein hormones (½), which regulate proliferation (½) and
differentiation (½) of haemopoietic progenitor cells
