Week 4

Question 1

Outline proprioception

Answer 1

Proprioception = Awareness of position of body parts in space.
Kinaesthetic = sense of movement

Abnormal can arise = demyelination diseases, stroke, Gillian barre, leprosy and cerebellar disease

Allows:
- movement - performing accurate w/o visual control
- Adjustment - of motor control patterns
- coordination - multi limb tasks

Question 2

Scheme of proprioception

Answer 2

Center motor commands —> joint angles or central somatosensory integration

Joint angles —> muscles spindles, Golgi organs, joint receptors, skin mechanoreceptors —> central somatosensory cortex

OR joint angles —> body position —> vestibular organ —> processed in cerebellum —> central somatosensory integration

ALL end —> proprioception (position, movement, posture, force)

Question 3

Describe the relative contributions of peripheral receptors responsible for proprioception

Answer 3

(Ia) spindle - detects change in muscle length and velocity; muscle length is different from combined muscle tendon length

(II) spindle - detects change in muscle length

(Ib) Golgi tendon organ - detects changes in force; measured at point of muscle/tendon attachment.

Articular - detects changes in joint angle; sensitive to joint capsule tension

Cutaneous - changes in applied to skin, as well as skin displacement

Subcutaneous - detects changes in applied pressure to skin

Question 4

Muscle spindle arrangement

Answer 4

Muscle spindles parallel with muscle fibres. Golgi tendon organs are arranged in series

This anatomical arrangement helps to determine the types that each provide.

Muscles spindles parallel with skeletal muscles = detect changes in length.

Golgi tendon organs lie between the muscle and the tendon = detect changes in force

Question 5

Skin mechanoreceptors

Answer 5

Superficial and deep.
Can be described as slow-acting or fast acting:

Superficial:
- Meissner corpuscles (fast acting)
- Merkel receptors (slow acting)

Deep:
- pacinian corpuscles (fast acting)
- Ruffini corpuscles (slow acting)

Question 7

Joint receptors

Answer 7

Different types:
- free nerve endings (similar to Golgi tendon organs)

Some respond to flexion, some to extension, some to compression and some to stress.

Can respond to damaging stress placed on joints such as high capsule tension.

Question 8

Describe how proprioceptive information is processed by the CNS

Answer 8

DCML tract:
Receptors (cutaneous, muscle and joint) —> dorsal column medial leminiscus (DCML) —> ipsilateral dorsal column nuclei synapses with second order neurons (medulla) —> second order neurons deccusate and ascend through medial leminiscus —> thalamus —> 2nd order synapse with 3rd order —> primary somatosensory cortex OR secondary somatosensory cortex OR posterior parietal area

Spinocerebellar tract:
Proprioceptive input —> ascends dorsal and ventral spinocerebellar tracts —> cerebellum for processing and coordination

Question 9

Using proprioceptive illusions as an example explain how other sensory input is processed in conjunction with proprioception

Answer 9

Pinocchio illusion:
- tendon vibration can lead to detection of anatomically impossible joint angles
- vibration of biceps tendon while touching nose
- when vibrated, brain receives 2 points of info:
Hand is moving away from face
Fingers in contact with the nose
- individual perceives nose is growing

Rubber hand illusion:
- vision tends to dominate other sensory modalities
- participant places hand below table, rubber hand is above table.
- second person strokes the rubber and actually hand simultaneously
- person perceives rubber hand as their own

Question 10

Describe the anatomy of the eye

Answer 10

Anterior segment -1/6 = corneal, lens, iris, cilliary body
Posterior segment - 5/6 = retina, choroid, optic nerve
- two segments join at the limbus

Cornea - transparent outer covering of eye, responsible for focusing light

Lens - flexible, transparent structure behind iris that focuses light onto the retina

Iris - coloured part of eye that controls size of pupil and regulates amount of light entering eye

Ciliary body - structure containing muscles that control shape of lens to focus light on retina; also regulates accomodation

Retina - light sensitive layer at back of eye, contains photoreceptor cells, converts light to electrical signals

Choroid - vascular layer behind the retina. Provides nutrients and oxygen to retina

Optic nerve - transmit visual information from retina to the brain for processing

Question 11

Layers (tunics) of the eye

Answer 11

Fibrous tunica - outermost, composed of cornea and sclera, provides structural support and protection

Vascular tunica - middle, consists of choroid, ciliary body and iris responsible for nourishing eye and regulating light entry

Nervous tunica - innermost, containing the retina, senses light and sends visual info to the brain via optic nerve.

Question 12

Ophthalmoscopic eye anatomy

Answer 12

Optic disc - area where optic nerve exits the eye, lacking photoreceptor cells, creates blind spot

Macula - small central area of the retina responsible for central vision and high visual acuity.

Fovea - black spot, central depression within the macula, containing densely packed cones for detailed and coloured vision

Question 13

Outline how light is transduced within the retina

Answer 13

Light enters eye, reaches retina, absorbed by photopigments in these cells, triggers biochemical cascade that generates electrical signals.

Signals are then transmitted through intermediate neurons in the retina before being conveyed via the optic nerve to the brain for processing into visual perception.

Question 14

Describe the visual pathway from the retina to the primary visual cortex.

Answer 14

Light rays reach retina —> stimulation of visual receptors (rods and cones) —> synapse with bipolar cells in outer-Lexi form layer —> synapse with retinal ganglion cells (RGCs) in inner plexiform layer —> axons of RGCs form optic nerve which impulses pass through

—> impulses reach optic chiasm (some cross) —> impulses reach optic tract —> optic tract goes to either superior colliculus or the LGN in thalamus.

LGN pathway:
impulses synapse in lateral geniculate nucleus (LGN), relaying to thalamus —> optic radiation —> fibres terminate in primary visual cortex (V1 area 17) for true image formation —> fibres travel to association area 18 for interpresentation

Superior colliculus (eye and head movement)
—> portion terminates
—> SC projects to thalamus in pulvinar nucleus
—> pulvinar nucleus to visual cortex in occipital lobe for further processing

Question 15

What is contained in the retina

Answer 15

Several layers

Specialised cells: rods for low light vision and cones for colour and detail perception located in outermost layer.

Beneath photoreceptors are several layers of interneurons such as bipolar cells, ganglion cells which process and transmit visual information to the brain via optic nerve.

Retina has supporting cells: Muller and horizontal cells contributing to structural integrity and function.

Question 16

Photo receptors of the retina

Answer 16

Rods - responsible for lowlight vision and peripheral vision

Cones - responsible for colour vision and high acuity in bright light conditions

Question 17

Retinal cell types

Answer 17

Bipolar - interneurons in retina that transmit signals from photoreceptor cells to ganglion cells

Ganglion - neurons in the retina that receive visual information from bipolar cells and transmit it to the brain via optic nerve

Interneurons - neurons in retina integrate and process visual information locally before transmitting it to ganglion cells

Horizontal - interneurons in retina that facilitate lateral communication between photoreceptor cells and bipolar cells

Amacrine - interneurons in retina that modulate and integrate visual information from bipolar and ganglion cells

Question 18

Layers of the retina

Answer 18

Vertical - contains photoreceptors, bipolar cells and ganglion cells

Horizon tall - contains interneurons, horizontal cells and amacrine cells

Question 19

Describe how disruption at various points within the visual pathway present in terms of visual deficits

Answer 19

Homonymous hemianopia - loss of vision in the same Half of the visual field in both eyes

Scotoma - small areas of decreased or lost vision within the visual field

Quadrantanopia - loss of vision in one quarter of the visual field

Cortical blindness - complete or partial loss of vision despite intact eyes and optic nerves due to damage to the visual cortex

Unilateral vision loss - vision loss occurring in only one eye

Bilateral vision loss - occurring in both eyes

Question 20

Describe the anatomy of the ear

Answer 20

3 segments: external, middle and inner.

Structures:
- auricle/pinna: external part of ear made of cartilage and skin, collects sound waves
- external auditory canal: tube like structure. Leads from auricle to eardrum, conducting sound to middle
- tympanic membrane: thin membrane separating external auditory canal from middle ear. Vibrates in response to sound waves
- tympanic cavity: air filled space, contains ossicles that transmit sound vibrations to inner ear
- bony labyrinth: complex system of hollow cavities within temporal bone of skull containing cochlea, vestibule, and semicircular canals
- membranous labyrinths: soft membranous structure within bony labyrinth containing fluid and structures crucial for hearing and balance
- cochlea: spiral shaped, fluid filled structure within inner ear responsible for converting sound vibrations into electrical signals to brain

Question 21

Ossicles of the middle ear

Answer 21

Transmit and amplify sound vibrations from typanic membrane to inner ear.

Maellus (hammer) - attached to tympanic membrame
Incus (anvil) - transmits vibrations from malleus to the stapes
Stapes (stirrup) - trnasmits vibrations from incus to inner ear through oval window

Question 22

Muscles of inner ear

Answer 22

Tensor tympani - dampens the malleus in response to loud auditory stimuli

Stapedius - dampens the stapes in response to loud auditory stimuli

Question 23

Bony labyrinth vs membranous labyrinth

Answer 23

Bony - network of bony passages within temporal bone containing cochlea, vestibule, semicircular canals. Filled wit fluid called perilymph

Membranous labyrinth - lies suspended within bony labyrinth. 4 parts: cochlear duct, utricle, saccule, and semicircular canals. Contains receptors for hearing and equilibrium. Filled with fluid called endolymph.

Question 24

Describe the cochlea and what’s apart of it

Answer 24

Spiral, fluid filled structure located within inner ear.
Converts sound vibrations into electrical signals.

Contains specialised hair cells that can detect different frequencies of sound and transmit corresponding neural impulses to auditory nerve.

Cochlea duct suspended between the Scala tympani and vestibuli.

Components:
- perilymph: fluid surrounding membranous labyrinth
- endolymph: fluid within membranous labyrinth. Essential for maintaining electrical potentials involved in hearing and balance
- hair cells: sensory cells, responsible for converting mechanical sound vibrations/head movements itno electrical signals
- organ of corti: contains hair cells and associated structures, crucial for transducing vibrations
- stereocilia: microscopic projections on hair cells that detect and transmit mechanical stimuli such as sound waves/head movements to brain

Question 25

Explain auditory transduction

Answer 25

Traduced within cochlea through process involving specialised hair cells. Sound waves enter cochlea through oval window cause vibrations in fluid filled cochlea duct. Vibrations are transmitted through basilar membrane causing displacement of hair cells. As hair cells move they convert mechanical energy from vibrations into electrical signals. Electrical signals then transmitted via auditory nerve to brain for interpretation.

Question 26

Outline neural pathway involved in hearing

Answer 26

Sound waves —> outer ear —> auditory canal —> vibration on tympanic membrane —> vibration transmitted to ossicles —> vibrations transmitted to oval window —> initiates fluid movement within cochlea —> vibrations transmitted to basilar membrane —> displacement of air cells —> mechanical stimuli into electrical signals —> transmitted via auditory nerve —> brainstem —> auditory cortex in temporal lobe —> sound perceived and processed

Question 27

Describe role of utricle and saccule in proprioception

Answer 27

Known as otolithic organs. Role in proprioception, body position and movement. Utricle and saccule contain hair cells which are embedded in a gelatinous matrix containing tiny calcium carbonate crystals called otoliths. When head moves, otoliths move stimulating hair cells providing information about linear acceleration and head position relative to gravity. Utricle: fluid filled sac in inner ear, involved in detecting linear acceleration and head tilt Saccule: fluid filled sac in inner ear, detects vertical acceleration and head position. Otoliths: tiny calcium carbonate crystals within utricle and saccule that enhance detection of gravitational forces and linear acceleration

Question 28

Neural pathway of balance

Answer 28

primarily involves vestibular system which includes vestibular nuclei located in brainstem. Information about head position and movement is received by vestibular receptors in inner ear, particularly: otolith organs and semicircular canals. —>These receptors send signals via vestibulocochlear nerve to the vestibular nuclei. —> signals sent from vestibular nuclei to various brain regions such as cerebellum, thalamus and cerebral cortex to integrate and process balance information. —> motor commands generated to adjust posture and maintain equilibrium. Involves pathways that connect to spinal motor neurons and muscles throughout body

Question 30

Anatomical structures of balance

Answer 30

Vestibular nuclei - central processing and integration of vestibular signals Semicircular canals - detect angular head movements to maintain rotational balance Otolith organs - detects linear and vertical acceleration and head tilt to maintain postural stability Cerebellum - coordinates and fine tunes balance and postural adjustments Thalamus - relays balance information to higher brain centres for conscious perception Cerebral cortex - integrates balance info with other sensory inputs for conscious balance control

Question 31

Differentiate between sensioneural and conductive hearing loss

Answer 31

Sensioneural hearing loss: - caused by damage to the inner ear or the auditory nerve pathways to the brain - can result from ageing, prolonged exposure to loud noises, genetic factors, infections, trauma. - often experience difficulty hearing faint sounds, understanding speech in noisy environments, issues with sound localisation. Conductive hearing loss: - sound waves are obstructed or impeded from reaching inner ear - typically occurs within outer or middle ear structures such as ear canal, tympanic membrane, or ossicles. - transmission of sound vibrations to the cochlea, organ responsible for converting sound in neural signals is hindered, results in diminished auditory perception

Question 32

Prelingual vs post lingual hearing loss

Answer 32

Prelingual = loss occurring before the development of language, typically in infancy or early childhood. Can impact speech and language acquisition Postlingual hearing loss = occurs after the acquisition of language, can result from age, noise exposure, infections, medical conditions leading to difficulty in communication and social interaction. Both types necessitate different approaches to intervention and management.

Question 33

List otologic symptoms upon taking patient history

Answer 33

Earache - primary (from ear), regional (nearby structures) or referred (from distant structures) Discharge - clear or purulent; offensive or inoffensive Swelling/erythema - lesions on the skin on or surrounding ear Hearing loss - bilateral or unilateral; worsens in response to loud noises Imbalance/dizziness - syncope or vertigo Tinnitus - pulsation or non pulsation; does it interfere with sleep patterns.

Question 34

Clinical signs of hearing loss

Answer 34

Involves assesment of both medical history and diagnostician tests. Otoscopy is used to visualise ear and tympanic membrane. Further tests such as imaging or a specialised assesment may be warranted Clinical signs: Rinne’s test (-) = abnormal bone conduction compared to air conduction during tuning fork examination. Webers test (+) = lateralisation of sound to one ear during tuning fork placement on midline of skull. Gross hearing = inability to hear whispered words Otoscopy = visualisation of perforation, retraction or fluid behind the eardrum Nystagmus = involuntary, rhythmic eye movement that indicates a malfunctioned CN VIII

Question 35

What is vertigo

Answer 35

Dizziness is described as impairment of spatial perception and stability. Vertigo is the illusion of movement or rotation of the self or environment; often coexists with nystagmus.

Question 36

Causes of vertigo

Answer 36

BPPV - brief episodes of vertigo triggered by specific head movements, typically due to displaced inner ear crystals. Ménière’s disease - disorder of inner ear characterised by episodes of vertigo, hearing loss, tinnitus, and ear fullness; caused by endolymph build up Labyrinthitis - inflammation of the inner ear structures causing vertigo, hearing loss and sometimes nausea or vomiting Cerebellar stroke - stroke effecting cerebellum, leads to vertigo, coordination difficulties, imbalance and other neurological symptoms.

Question 37

Explain BPPV - benign paroxysmal positional vertigo

Answer 37

Characterised by brief episodes of vertigo triggered by specific head movements Typically caused by specific displacement of small calcium carbonate crystals known as canaliths within the semicircular canals of the inner ear. When these crystals become dislodged from usual position and migrate into the fluid filled canals, they can trigger abnormal sensations of spinning.

Question 38

Describe basic principles of clinical examination fro vertigo

Answer 38

Cranial nerve exam (particularly CNVIII), neurological examination (upper and lower), Dix-hallpike manoeuvre. Symptoms/signs: - hearing loss - more common in menieres or labyrinthitis, uncommon in BPPV - infective symptoms - labyrinthitis, uncommon in BPPV and Minieres - episode length - shorter = BPPV, longer = Menieres - Dix-Hallpike manoeuvre - positive in BPPV - DANISH mnemonic - dysmetria, ataxia, nystagmus, intention tremor, slurred speech, headache; red flags suggesting cerebellar stroke leading to vertigo - movement dependence - BPPV movement dependent, others occur at rest

Question 39

What is the Epley manoeuvre used for

Answer 39

Canalith repositioning procedure Series of specific head movements to treat BPPV Guiding displaced canaliths within inner ears semicircular canals back into the utricle. Aims to alleviate vertigo symptoms by preventing inappropriate stimulation of vestibular system.

Question 40

Discuss olfactory epithelium

Answer 40

Thin sheets of cells high up in nasal cavity; contain 3 types of cells: - olfactory receptors: detect odours, transmit to brain - supporting cells: structural + metabolic support - basal cells: progenitor cells to regenerating olfactory receptor cells Olfactory receptors die and regenerate in a 4-8 week cycle. Number of receptors dictates sensitivity to nasal cavity to odour.

Question 41

Discuss the neural pathways involved in olfaction

Answer 41

Odorant molecule —> olfactory receptor in olfactory epithelium —> olfactory receptors bundle to form olfactory nerve —> passes through cribiform plate —> olfactory nerves enter olfactory bulb where they synapse with neurons in bulb —> axons from bulb neurons form olfactory tract —> carries info to primary olfactory cortex in temporal lobe for primary processing —> projects to secondary areas of brain: either hippocampus OR amygdala OR orbitofrontal cortex Secondary targets: Amygdala —> processes emotional aspects of smell Hippocampus —> memory formation related to smell via associated cortical areas Orbitofrontal cortex —> conscious perception of odour

Question 42

Describe factors that influence sense of smell

Answer 42

Common cold - nasal congestion inhibits odour detection Head injury (trauma) - damage to olfactory nerves impairing smell perception Temporal lobe epilepsy - seizures disrupt olfactory processing Radiation exposure - radiation can cause damage to olfactory receptors Pregnancy - irregular hormonal changes affect olfactory sensitivity Neurodegeneration - degeneration of olfactory neurons reduces smell perception

Question 43

What is gustation

Answer 43

Taste perception. Detection of chemicals in mouth by taste buds on tongue. Taste buds contain receptor cells that respond to different qualities such as: sweet - sugars and carbohydrates, energy rich sour - acidity, spoiled or unripe foods salty - recognises sodium ions, essential for functions bitter - detect potential toxins, plant-based alkaloids Unami - savoury flavours, amino acids such as glutamate

Question 45

Explain tongue anatomy including papillae

Answer 45

Papillae = small structures found on surface of tongue that contain tastebuds Each papillae contains from one to several hundred taste buds. Can also contain basal cells surround taste cells and gustatory afferent axons Different types: Fungiform - mushroom shaped scattered across tongue surface Foliate - leaf like structures located sides of tongue Circumvallate - large, circular papillae arranged in row at back of tongue, surrounded by trench. Filliform - small, threadlike structures covering entire tongue surface, devoid of taste buds aid in tactile sensation and food manipulation.

Question 47

Key anatomical structures involved in gustation

Answer 47

Taste receptors - detect chemical stimuli on tongue and transmit taste information Gustatory nucleus - processes taste signals in the brain stem Thalamus - relays taste information to higher brain regions for further processing Gustatory cortex - integrates taste signals and contributes to the perception of flavour

Question 48

Taste receptor cells: how often replaced? What is their anatomy? How do they work? What cranial nerves involved?

Answer 48

Constantly replaced every 10-14 days Feature long thin microvilli extending into taste pores at the apical end near the tongues surface allowing them to contact substances in mouth. Taste receptor cells are not neurons, they form synapses with endings of gustatory afferent nerves at the base of the taste bud, facilitating transmission of taste information to brain. 3 cranial nerves innervate distinct regions of the tongue and throat that also receive from taste receptor cells also.

Question 49

Discuss the neural pathway of gustation

Answer 49

Particle to be tasted —> dissolved with saliva —> detected by taste receptors —> synpase with first order neurons which are cranial nerve VII, IX, X VII —> taste information for anterior 2/3rds of tongue IX —> taste info from posterior 1/3rd of tongue X—> transmits taste info from the epiglottis and pharynx Cranial nerves transmit signals to nucleus of solitary tract (NST) in the medulla —> synapse in NST to 2nd order neurons —> project to thalamus —> synapse with 3rd order neurons in the ventral posteromedial nucleus (VPM) of thalamus —> relates to the gustatory cortex in insula —> concious perception of taste. Taste can also be relayed to orbitofrontal cortex, amygdala. If lesion: Lesion —> transmission to gustatory cortex —> aguesia

Question 50

What is MS

Answer 50

Chronic neurological condition characterised by damage to the myelin sheath, the protective covering of nerve fibres in the CNS. Damage disrupts flow of electrical impulses along nerve fibres leading to wide symptoms such as: - muscle weakness - vision problems - difficulties with coordination and balance - sensory problems, confusion, headaches etc. Autoimmune disorder where body’s systems attacks own tissues targeting brain and spinal cord.

Question 52

Pathophysiology of MS

Answer 52

1. Immune activation: CD4+ T helper cells (specifically Th1 and Th17) become activated and cross the BBB releasing cytokines (IL-1, IL-17, IFNg, TNF). These recruit other immune cells such as B cells, neutrophils, monocytes, macrophages and dendritic cells to attack myelin. 2. Demyelination: B cells and macrophages cause demyelination. Results in plaques commonly in white matter, spinal cord and optic nerves. CD8 T cells exhibit cytotoxicity against Oligodendrocytes. 3. Neurodegeneration: prolonged inflammation and demyelination lead to axonal damage contributing to irreversible neurological deficits + worsening disability 4. Remyelination: body attempts to repair myelin. In later stages however impaired Oligodendrocytes function and chronic inflammation prevents this as a result of CD8 T cells attacking them. 5. BBB breakdown: becomes leaky, allowing immune cells to infiltrate CNS exacerbating immune response.

Question 53

Clinical features of multiple of MS

Answer 53

Motor control: muscular spasms, weakness, poor coordination, balance Fatigue: general tiredness, heat sensitivity Neurological symptoms: vertigo, pins and needles, neuralgia, visual disturbances Incontinence: bladder and bowel Cognitive symptoms: memory loss, depression, thought and cognitive impairment

Question 54

Distinguish between various MS disease courses

Answer 54

Progressive-relapsing: steadily worsening symptoms with occasional flare ups. Secondary progressive: gradual worsening of symptoms after an initiation relapsing-remitting phase. Primary progressive: continuous progression of symptoms from the onset without without periods of Relapsing remitting: periodic flare ups of symptoms followed by periods of partial or complete recovery

Question 55

Discuss clinical investigation of MS

Answer 55

Gadolinium MRI - gadolinium visualises progression, used to visualise damage in MS CSF analysis - drainage via LP, presence of IgG antibodies indicates MS Autopsy - histopathological analysis can indicate characteristic scattered lesions

Question 56

First line pharmacological management of MS

Answer 56

Corticosteroids used for acute attacks - not effective in preventing disease Plasmapheresis is used for treating severe attacks Beta-interferon: inhibits MHCII expression, and subsequently inhabiting CD4+ T cells activity. - side effects - flulike symptoms, liver damage Glatiramer acetate: amino acid copolymer, unknown mechanism of action. Dimethyl fumarate: anti-inflammatory, activates Nrf2 and reduces oxidative stress

Question 57

Second line pharmacological treatment of MS

Answer 57

natalizumab: monoclonal antibody against the a4 integrity, can lead to allergies. Rituximab; ocrelizumab: monoclonal antibodies against CD20 expressed on B cells, can lead to allergies Daclizumab: monoclonal antibody against CD52 that activates NK cells which can kill auto reactive T cells. Fingolimod: antagonist of the sphigosine-1 phosphate receptor, sequesters lymphocytes and lymphoid organs Cladribine: synthetic deoxyadenosine analogue, cytoxic to lymphocytes; unknown safety beyond 2 years.

Question 58

Third line treatment of MS

Answer 58

Autologous HSC transplant: HSC harvested from marrow, kill immune cells and reset immune cells

Question 59

Discuss clinical investigation of MS

Answer 59

Gadolinium MRI - gadolinium visualises progression, used to visualise damage in MS CSF analysis - drainage via LP, presence of IgG antibodies indicates MS Autopsy - histopathological analysis can indicate characteristic scattered lesions