ALT Aqueous humour undergoes ultrafiltration in the ciliary body to provide a nearly protein free, optically clear liquid to aid vision. It also has high levels of ascorbic acid to protect against UV-radiation that can cause the formation of free radicals.

ALT B) Cornea The cornea contributes to the majority of the refractive power of the eye, with the remainder being attributed to by the lens. However, the refractive power of the cornea is fixed, whereas the lens can increase or decrease its refractive power to focus on specific objects.

ALT A 15 year old girl presents with chronic blurred vision. You suspect a refractive error. Which of the ocular structures is responsible for the greatest proportion of refractive power of an eye? A) Lens B) Cornea C) Aqueous humour D) Vitreous humour

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ALT The arcuate nucleus in the hypothalamus plays a key role in appetite regulation. It relies on neuronal, hormonal and nutritional input, primarily using the neurotransmitters neuropeptide Y, agouti-related peptide (promote hunger), POMC, CART, α-MSH and β-endorphin (suppress hunger).

ALT D) Pharyngeal and oesophageal phases The oral phase is under voluntary control, whereas the pharyngeal and oesophageal phase are under involuntary control. The involuntary phases are coordinated by the swallowing centre in the brainstem.

ALT A 75 year old man has developed swallowing difficulties after a stroke Which phase(s) of swallowing are under involuntary control? A) Pharyngeal phase B) Oral and pharyngeal phases C) Oral and oesophageal phases D) Pharyngeal and oesophageal phases

ALT Carbohydrate digestion occurs in stages before it can be absorbed. It is initiated in the mouth by salivary amylase. The majority continues in the small intestine by a pancreatic enzyme (pancreatic amylase) and digestion is completed by brush border enzymes.

ALT A) Contract gland myoepithelium Acetylcholine acts on M3 muscarinic receptors. This causes increased saliva and HCO3– secretion. Co-transmitters increase glandular blood flow and contract their myoepithelium to increase the rate of saliva expulsion.

ALT A patient taking anticholinesterase therapy presents to your clinic with sialorrhoea. What effect would you expect increased parasympathetic activity to have on saliva production? A) Contract gland myoepithelium B) Decrease production C) Decrease gland blood flow D) Increase protein secretion

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ALT The cerebral spinal fluid has many functions including providing buoyancy by creating a bath around the brain and protection by acting as a shock absorber, maintaining homeostasis by regulating the distribution of metabolites and clearing waste into the blood stream.

ALT C) Send sensory information from the PNS to the brain The ascending tracts relay sensory information from the peripheral nervous system through the spinal cord to the brain. The descending tracts send motor signals from the brain to the lower motor neurons. The limbic system is responsible for emotional regulation and prefrontal regions of the frontal lobes for executive functioning.

ALT A 25 year old woman with MS has lesions in multiple areas of the CNS What is the role of the ascending tracts in the central nervous system? A) Regulate emotions B) Send motor signals from the brain to LMNs C) Send sensory information from the PNS to the brain D) Higher order executive functions

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ALT Iron enters cells using receptor-mediated endocytosis. Its receptors are arranged in clusters with proteins such as clathrin on the cell membrane. On binding, these proteins cause this region to invaginate becoming a vesicle within the cell. This process can be hijacked by toxins such as cholera.

ALT D) Intracellular receptor Small, hydrophobic (i.e. lipid-soluble) molecules can diffuse across the plasma membrane without assistance from cell surface proteins. Therefore they can access intracellular receptors to exert their effects. These receptors are found in the cytoplasm or nucleus of the cells and can interact with DNA to affect transcription.

ALT You prescribe a steroids for an acute flare up of ulcerative colitis in a 28 year old woman To which receptor would a small, lipid-soluble molecule most likely bind to? A) Enzyme-linked receptor B) G-protein coupled receptor C) Ion channel receptor D) Intracellular receptor

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ALT Growth hormone has both direct and indirect metabolic effects by binding to receptors itself or indirectly by stimulating liver cells to produce hormones such as insulin-like growth factors (IGFs). In this way it affects almost every tissue in the body.