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Lecturer: Dr Lucy Patston

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1 Lecturer: Dr Lucy Patston

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7  A) Resting membrane potential (½) ◦ -70mV, cell more –ve inside, Na/K channels closed (½)  B) Threshold, -55mV (½), ◦ Na channels start to open (½)  C) Depolarisation (½) ◦ Na channels open, start to close (½) ◦ K channels start to open  D) Repolarisation (½) ◦ K channels have opened (½)  E) Hyperpolarisation (½) ◦ K channels slow to close cause more negativity  F) Na/K pump (½) ◦ 3 Na out/2 K in (½)  2 mark allocation for refractory periods

8 1. An action potential arrives at the terminal button (1/2) 2. Voltage-gated calcium channels open and calcium flows in to the terminal button 3. Presence of calcium elicits vesicles to move to the terminal membrane 4. Vesicles fuse with the terminal membrane, releasing neurotransmitter into the synaptic cleft (1/2) 5. Neurotransmitters bind to receptor sites on the post- synaptic receptors 6. (Ligand-gated) Post-synaptic receptors open and ions flow in to the post-synaptic cell 7. Neurotransmitters are taken back in to the pre-synaptic terminal for repackaging (process called reuptake)

9  Autoimmune disease  Attacks/reduces/damages/degrades Ach receptors at neuromuscular junction  Released ACH NTs have nowhere to bind ->  Reduction of Na2+ ions flowing into the post- synaptic membrane (muscle fibres) facilitating further APs  Muscle weakness due to lack of stimulation to muscle fibres  Ptosis in eyelids seen first as greatly used muscles weaken faster  (Answer should be limited to synaptic transmission, not symptoms/prognoses etc)

10  Drug cocaine blocks reuptake channels that normally allows neurotransmitter back into the presynaptic terminal button for repackaging  Dopamine neurotransmitter released normally but stays in the synaptic cleft  This means dopamine binds to post-synaptic receptors more/longer causing the cell to fire continuously, creating the cognitive effect of “speed” in the person

11  1 mark: recognizable picture with only LVF and information ending at right hemisphere  1 mark: nasal aspect of left eye and lateral aspect of right eye  2 marks: at least 6 of following labels: LVF, optic nerve, optic chiasm, optic tract, LGN of the thalamus, occipital lobe/cortex, right hemisphere)  1 mark: nasal going contralateral (clarity)  1 mark: lateral going ipsilateral (clarity)

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13  Marks gathered for any of the following (up to 3 marks for each plexus):  Root values stated  Major nerves stated  General course/distribution/innervation of major nerves  Comment on clinical effects of disorder to major nerves  Any other relevant piece of information related to plexus

14  The answer should only discuss the pupillary reflex (not consensual reflex) but no marks will be deducted if both are drawn/discussed. Marks are allocated for getting the following steps in order with critical labels drawn and mentioned.  Light shined into the eye elicits reflexive constriction of pupil.  The optic nerve conveys afferent information from the retina to the pretectal area of the midbrain. (2 marks)  Interneurons from the pretectal area synapse in the parasympathetic nucleus of the oculomotor nerve. (1 mark)  PS efferents travel in the oculomotor nerve (1½ marks)  and synapse at the cilary ganglion (½ mark)  The message then travels in the ciliary nerve, (1 mark)  which innervates the pupillary sphincter muscle of the pupil (1 mark)  and causes the pupil to constrict. (1 mark)

15  Trigeminal nerve (5 marks)  Facial nerve (5 marks)  Marked subjectively

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17  ½ correct nerve name  ½ x3 relevant information about the nerve

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