Questions for SBAs Flashcards
How does a fasciculation occur (3)
- Motor neuron dies, and so muscles fibres of the motor unit lose their nerve supply (denervation)
- Axons of the remaining motor unit grow and reach out to the denervated muscles fibres (reinnervation).
- The resulting new motor unit is larger and less stable and prone to ectopic generation of electrical stimuli in the distal axon that cause contraction of the muscle fibres ( a fasciculation).
Name 2 signs of an UMN lesion (seen in the patient) (2)
Tone increased spastic, clonus present, power weakness (pyramidal distribution flexors stronger than extensors UL and extensors stronger than flexors
in LL), reflexes brisk, extensor plantar responses, no wasting and no fasciculations.
Name 2 signs of a LMN lesion (seen in the patient) (2)
LMN: Tone flaccid, power weakness (distal weaker than proximal), no clonus, reflexes reduced or absent, flexor plantar responses, wasting may be present, fasciculations may be present.
What pathways are affected in NMS (1)
Pyramidal tracts (these are the corticospinal and corticobulbar tracts)
Describe how the counter-current mechanism is established and why its useful (4)
- The counter-current mechanism is established by Na+ reabsorption (ascending limb of LoH)
- urea recycling
- and the countering direction of flow of vasa recta.
- The counter-current mechanism is useful in enabling water reabsorption/removing more urea using less water/concentrates urine
How does vasopressin aid in the counter-current multiplication for water reabsorption (2)
Boots UT-A1 and UT-A3 numbers (apical and basolateral membrane of collecting duct)
What factors stimulate ADH release (2)
Increased osmolarity
Hypovolaemia
Decrease in BP
Nausea
Angiotensin II
Nictotine
What factors inhibit ADH release (2)
Decreased osmolarity
Hypervolaemia
Increase in BP
Ethanol
ANP (atrial natriuretic peptide)
How does ADH affect aquaporins (2)
ADH up/downregulates AQP2 (apical) & AQP3 (basolateral) numbers as required
How does ADH support Na+ reabsorption at the kidney (3)
- Thick ascending limb: Increase Na+/K+/2Cl- symporter
- DCT: Increase Na+/Cl- symporter
- CD (principle cell): Increase Na+ channel
What is the role of the kidney to maintain acid-base balance (3)
Secretion + excretion of H+
Reabsorption of HCO-3
Production of new HCO-3
Describe how increased tubular sodium affects GFR (3)
High tubular sodium -> Increased sodium/chloride uptake via triple transporter
Adenosine release from Macula Densa cells -> Detected by extraglomerular mesangial cells -> Reduces renin production
Promotes afferent SMC contraction -> Reduces perfusion pressure and so GFR
Where are the low pressure baroreceptors located (3)
Atria
Right ventricle
Pulmonary vasculature
Where are the high pressure baroreceptors located (3)
Carotid sinus
Aortic arch
Juxtaglomerular appartus
What is potassium secretion stimualted by (4)
Increased: Plasma K conc Tubular flow rate Aldosterone Plasma pH
Causes of hypokalaemia (5)
Inadequate dietary intake (too much processed food)
Diuretics (due to increase tubular flow rates)
Surreptitious vomiting
Diarrhoea
Genetics (Gitelman’s syndrome; mutation in the Na/Cl transporter in the distal nephron)
Causes of hyperkalaemia (5)
Severe diabetes Elderly ACE inhibitors Seen in response to K+ sparing diuretics Kidney disease
How does a prolactinoma cause infertility (4)
- Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus
- Inhibits kisspeptin release.
- Decreases in downstream GnRH/LH/FSH/T/Oest
- Oligo-amenorrhoea/Low libido/Infertility/Osteoporosis
Describe process of plaque formation (4)
- Damage occurs to endothelial lining (due to high BP, smoking, diabetic glycosylation end products etc.) especially at vascular branching points (as a result of turbulent flow → endothelial stress)
- Lipids leak through damaged endothelium and accummulate in intima → oxidised by free radicals
- Macrophages scavenge the oxidised lipids → turn into foam cells and deposit in blood vessel walls
- Foam cells secrete growth factors (like platelet derived growth factor) that result in smooth muscle proliferation + extra-cellular matrix deposition → plaque formation
How are DVTs are often precipitated by Virchow’s triad (3)
- Blood stasis (eg. like a long haul flight or bed rest)
- Endothelial damage (eg. traumatic vessel injuries)
- Hypercoagulability (eg. oral contraceptive use, pregnancy)
Cellular pathology of MS (4)
Inflammation
Demyelination
Axonal loss
Neuro degeneration
Types of MS (4)
Relapsing-remitting
Primary progressive
Secondary progressive
Progressive-relapsing
Name and describe the paradox seen involving angiogenesis and cardiovascular disease (3)
The Janux paradox. Angiogenesis (within vaso vasorum of the adventita) promotes plaque growth Therapeutic angiogenesis (revascularisation) prevents damage post-ischemia
Describe how early onset pre-eclampsia affects the fetus (4)
Shallow trophoblast invasion
Maladation of materal spiral artery
Poor placental perfusion
Fetal growth reduction
What is recurrent pregnancy loss/recurrent miscarriage (1)
(In the UK, defined by) 3 or more pregnancy losses (consecutive or non-consecutive
What signalling pathways might underpin RPL/RM (2)
Reduced levels of LIF in the uterine secretions of sub fertile women
Non-selective uterus hypothesis in those patients - uterus permits implantation of poor quality embryos and changes in uterine mucin expression in women with RM/RPL
What is the major cause of early clinical pregnancy loss (<12 weeks gestation) (1)
Aneuploidity
How does this increase with age (2)
Cohesion proteins are lost, leading to loss of cohesion between chromatids with increasing age of the oocytes
Chromatids can seperate and drift during meiotic division, rather than being segregated accurately by the spindle
Risk factors for ectopic pregnancy (5)
Prior ectopic pregnancy Prior fallopian tube surgery Certain STIs Pelvic inflammatory disease Endometriosis
How does smoking increase the risk of ectopic pregnancy (3)
Continine, a component of cigarette smoke, regulates the expression of PROKR1, a regulator of fallopian tube smooth muscle contractabiltiy
Conitinine also induces pro-apoptosis protein expression in fallopian tube explants
It is hypothesised that tobacco smoke inhibits ciliary function therefore reducing tubal transit of the embryo
What is an ectopic pregnancy (1)
Implantation of the embryo at a site other than the uterine endometrium
What are two ways in which cannabis may affect the fallopian tube (2)
Cannabionoid receptor CB1 levels are reduced in ectopic pregnancy patients
Alter the endocannabionoid tone (balance) in the tube leading to a disrupted embryo environment
What is stigma (1)
Stigma refers to challenges faced by people with mental illness related to knowledge, attitudes, and behaviour of people they meet
What are the types of stigma (3)
•Intrapersonal stigma
Direct effect on the individual
Internalised discrimination
Compounded by direct effects of illness
•Interpersonal stigma
Family
Friends
Colleagues
•Structural stigma
Poor resources and funding
Access to physical health care
What are the consequences of stigma (3)
Barrier to care
Abuse
Rejection + Isolation
Causes of mental health stigma (3)
- Poor understanding of mental health
- Negative attitude
- Social exclusion
Pathophysiology of Achondroplasia (3)
Inhibition of chondrocyte proliferation in proliferation zone of physis (secondary)
Defect in endochondral bone formation
Long bones affected
Describe the formation of a plaque (4)
- Damage occurs to endothelial lining (due to high BP, smoking, diabetic glycosylation end products etc.) especially at vascular branching points (as a result of turbulent flow → endothelial stress)
- Lipids leak through damaged endothelium and accummulate in intima → oxidised by free radicals
- Macrophages scavenge the oxidised lipids → turn into foam cells and deposit in blood vessel walls
- Foam cells secrete growth factors (like platelet derived growth factor) that result in smooth muscle proliferation + extra-cellular matrix deposition → plaque formation
SSSS described how in most and why
Neonates
Exfoliative toxin
Kidneys cannot excrete it quickly
Pathophysiology of Osteogenesis Imperfecta? (2)
Decreased type 1 collagen due to decreased secretion and production of abnormal collagen
Insufficient osteoid production
What two things contribute to developing proteinuria (2)
Hyperglycaemia
Glomerular HTN
FIX Describe the mechanism of damage in retinopathy (4)
Mitochondrial superoxide free radicals in endothelium
Glycated plasma proteins -> AGEs advanced glycated end products
Inflammatory pathways
Damaged endothelium
What happens in compation? (5)
Cells start pressing up against the zona pellucida
Go from spherical to wedge-shaped
Outer cells connect to each other through tight gap junctions and desmosomes
Forms barrier to diffusion between inner and outer embryo
Outer cells become polarised
Describe the structure of the primary chorionic villi and outline the stages in its development (5)
Developed from cytotrophoblast which form finger-like projections through the syncitiotrophoblast layer into the maternal endometrium
Terminal villus - convoluted knot of vessels and vessel dilation
Primary development - outgrowth of the cytotrophoblast and branching of these extensions
Secondary - growth of the fetal mesoderm into the primary villi
Tertiary - growth of the umbilical artery and umbilical vein into the villus mesodderm, providing vasculature
