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105 Cards in this Set
- Front
- Back
What do the eyes form from? |
The optic vesicles of the diencephalon |
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How is transparency maintained in the cornea? |
There is regular arrangement of collagen in the stroma, no blood vessels and endothelium pump keeps aqueous humour out. |
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How many layers are in the retina? |
10 |
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Where are the nerve fibres in the retina? |
Near the top |
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What the optic disc? |
Blind spot, as its where the optic nerve leaves the eye |
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Where is the highest visual acuity? |
Fovea/Macula - highest density of rods and cones |
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What ensures the lens is transparent? |
It doesn't have blood vessels |
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What is the difference between the segments and chambers of the eye? |
Segments - in front of/behind the lens Chamber - iris |
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Where is aqueous humour produced? |
In the posterior chamber by the ciliary bodies |
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Where does AH get filtered? And what drains it? |
Filtered through the trabecular meshwork and drained by schlemm's canal
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What is the conjunctiva? |
Thin vascular membrane that covers inner surface of eyelid and sclera |
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What is the autonomic innervation of the lacrimal apparatus? |
Parasympathetic |
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Where do tears drain? |
Into lacrimal sac and then into the inferior meatus of the nasal cavity |
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What is the role of tears? |
Keeps cornea moist, washes away foreign bodies, kill microbes and provides smooth surface for refraction |
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What parts of eye refract light? |
Cornea, lens, AH and VH |
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What 3 things allow accommodation? |
Lens can change shape, pupil can constrict and eyes can converge |
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How does the lens change shape? |
Paraympathetic nerevs cause ciliary muscles to contract, ligments slacken and lens becomes thicker |
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How does the pupil constrict? |
PS innervation from oculomotor n (III) causes sphincter pupillae to contract |
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How do the eyes converge? |
Medial recti contract due to PS innervation from CN III |
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How do we see? |
Energy from visible light stimulates photorecepter cells on the retina. Rods and cones generate an AP using the energy from the light |
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What is phototransduction? |
The conversion of light energy to an electrochemical response by photoreceptors |
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What are the visual pigments in rods and cones? |
Rhodopsin and S, M and L cone opsin |
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What is rhodopsin made up of? |
Opsin and 11-cis retinal
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How does light energy affect rhodopsin? |
It causes 11 cis retinal to change to all-trans retinol, which causes rhodopsin to split. This results in bleaching of the visual pigment and the start of the phototransduction cascade |
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What happens in the pigment epithelial cells? |
All trans retinol is regenerated into 11 cis retinal |
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How does Vitamin A play a part? |
AT retinol can be formed from Vit A in the diet so can help prevent blindness |
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What rhyme is used to remember the actions of the extrinsic eye muscles? |
RADSIN - Recti adduct, superiors intort |
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What is the visual pathway? |
Retina Optic nerve Optic chiasma Optic tracts Lateral geniculate body Optic radiation Primary visual cortex |
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What would occur if the right optic nerve is damaged? |
Blindness in right eye |
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What would happen if optic chiasma is disrupted in the middle? What can cause this? |
Bitemporal hemianopia Pituitary tumour |
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What would happen if right optic tract or optic radiation is damaged? |
Contralateral homonymous hemianopia |
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What is the pathway of the PS fibres that elicit the pupillary reflex? |
Sensory fibres leave the optic tract to go to the mid-brain and synapse with CN III via EWN. The pre-ganglionic fibres synapse then in the ciliary ganglion. |
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What syndrome causes unequal pupil size, ptosis (eyelid drooping) and loss of sweating on affected side? |
Horner's Syndrome - caused by pancoast tumour of the lung |
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Which glial cells are found in the CNS? |
Ependymal - line ventricles Microglia - phagocytosis Oligodendrocytes - myelination Astrocytes - surround synapses and capillaries |
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Which glial cells are found in the PNS? |
Schwann - Myelination Satellite - Surround neuronal cell bodies |
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What disease can cause loss of the myelin sheath? |
Multiple Sclerosis |
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What three parts does the neural tube split into after 4 weeks? |
Prosencephalon - Forebrain Mesencephalon - Midbrain Rhombencephalon - Hindbrain |
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What structures does the pronsencephalon form? |
Cerebral cortex, basal ganglia, thalamus, hypothalamus |
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What does the mesencephalon form? |
The midbrain |
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What does the rhombencephalon form? |
Pons, cerebellum and medulla |
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Where is CSF found in the spinal cord? |
Subarachnoid space |
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Where is CSF produced? And where is it absorbed? |
Produced by choroid plexus and absorbed by arachnoid villi |
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Where is there no blood brain barrier? |
Vomiting center of the medulla and the hypothalamus |
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What does the brainstem contain? |
The midbrain, pons and medulla |
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What functions are contolled in the medulla? |
Blood pressure, breathing, swallowing and vomiting |
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What tracts are found in the medulla? |
Ascending somatosensory tracts and descending corticospinal tracts |
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What is the function of the pons? |
Acts as a relay station for information transfer between the cerebrum and cerebellum and also helps coordinate control of breathing |
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What is the function of the midbrain? |
Controls eye movement and also relays signals for auditory and visual reflexes |
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What is the function of the cerebellum? |
To process sensory information and coordinate the execution of movement |
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Where does the cerebellum receive sensory input from? |
Somatic receptors in the periphery of the body and receptors for balance located in the inner ear |
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What does the diencephalon contain? |
Thalamus, hypothalamus, pituitary and pineal glands |
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What does the thalamus do? |
Acts as a relay station for sensory information for lower parts of the CNS |
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What does the hypothalamus do? |
It is a center for homeostasis and contains centers for behavioural drives such as hunger and thirst |
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What does the pineal gland secrete? |
Melatonin |
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What Brodmann areas are found in the frontal lobe? |
Area 4 - Precentral gyrus - Primary Motor Cortex Area 44/45 - Inferior frontal gyrus - Broca's Area of motor speech Prefrontal cortex |
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What is the motor homunculus? |
Somatotopic representation of contralateral half of body |
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What does a frontal lesion cause? |
Intellectual impairment, personality change, urinary incontinence, monoparesis or hemiparesis. Left sided lesions cause Broca's Aphasia |
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What is broca's aphasia? |
Can't construct sentences, but know what they want to say. |
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What brodmann's areas are found in the parietal lobe? |
Area 3/1/2 - Post central gyrus - Primary sensory area Superior parietal lobule - interpretation of general sensory info and conscious awareness of other half of body Inferior parietal lobule |
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What does a parietal lesion cause? |
Contralateral sensory loss/neglect Agraphaethesia Homonynous field defect Right - Dressing apraxia, failure to recognise faces Left - Limb apraxia |
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What areas are found in the temporal lobe? |
Primary auditory complex Wernicke's area - key for understanding speech Inferior surface - used to understand smellq |
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What would a temporal lesion cause? |
Left - Acalculia, alexia (can't read), agraphia, wernicke's aphasia, right-left disorientation and homonymous field defect Right - Confusion, failure to recognise faces and homonymous field defect |
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What is main function of the occipital lobe? |
Contains primary visual cortex |
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What would an occipital lesion cause? |
Visual field defects and visuospatial defects |
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What types of fibres are found in the white matter of the brain? |
Commisural - connect 2 hemispheres Association - connect one part of cortex to another Projection - Run between cerebral cortex and subcortical areas |
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What fibres make up the internal capsule? |
Projection fibres |
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What three make up the Basal Ganglia? |
Caudate nucleus, putamen and globus pallidus |
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What is the major function of the BG? |
Initiation and Termination of movements |
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What sensations does the posterior column associate with? |
Touch, pressure and proprioception |
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Touch, pressure and proprioception |
Moves up posterior column and synapses in medulla. Switches to other side here and then synapses in thalamus. Then moves up to the primary sensory cortex |
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What tract is associated with pain and temperature? |
The lateral spinothalamic tract |
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The lateral spinothalamic tract |
1st order neurons enter spinal cord and synapse in grey matter. They cross over to other side and move up LS tract. They synapse in medulla and move up to primary sensory cortex |
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Where do motor/descending tracts switch over? |
In the medullary pyramids |
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What is an example of a descending tract? |
Corticospinal tract |
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What happens to the muscle tone and reflexes if the UMN becomes damaged? |
They become exaggerated as the inhibitory action of the UMN is lost |
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What type of receptors are used to detect touch, pain, deep pressure and warmth? |
Touch - tactile corpuscle Pain - free nerve ending Deep pressure - lamellated corpuscle Warmth - Ruffini corpuscle |
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What type of fibres mediate cutaneous sensation? |
A beta A gamma C |
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Talk about A beta fibres |
They are large myelinated fibres for touch, pressure and vibration |
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Talk about A gamma fibres |
They are small myelinated fibres for cold, fast pain and pressure |
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Talk about C fibres |
They are unmyelinated fibres for warmth and slow pain |
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What activates signal transduction in nociceptors? |
pH, heat and local chemical mediators such as bradykinin, histamine and prostaglandins |
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What is the gate control theory of pain receptors? |
Activity in A beta neurons activate inhibitory interneurones which inhibit a gamma and C fibres. Descending pathways also activate the inhibitory interneurones. |
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How do the inhibitory interneurones work? |
When activated they release opioid peptides (endorphins) that inhibit transmitter release from the A gamma and C fibres |
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How do NSAIDs work? |
They inhibit prostaglandin formation, which reduces the sensitivity of nociceptors to bradykinin |
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How do local anaesthetics work? |
They block Na+ action potentials |
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How does Trans cutaneous electric nerve stimulation work? |
Using the gate control method as it activates A beta fibres |
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How do opiates work? |
It reduces sensitivity of nociceptors, blocks transmitter release and activates descending inhibitory pathways |
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What are the 12 Cranial nerves? |
Olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory and hypoglossal |
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What is the pathway of the olfactory nerve? |
Olfactory epithelium in nose --> nerve fibres pass through cribriform plate --> enter olfactory bulb |
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What type of nerve is the olfactory? |
Special sensory |
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How can the olfactory nerve be affected clinically? |
A fractured cribriform plate can tear the fibres and cause anosmia |
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How can the optic nerve be affected clinically? |
Increased CSF pressure can cause papilloedema Sections of optic tract - |
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What does the oculomotor nerve do? |
Innervates extraocular muscles and eyelid. Also brings PS fibres to pupil and ciliary muscles |
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How can CN III be affected clinically? |
Eyelid drooping (ptosis) No pupillary reflex Eyeball abducted and pointing down No accommodation of the lens |
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What does trochlear nerve palsy occur as? |
Diplopia when looking down |
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Which of the trigeminal branches is both sensory and motor? |
Mandibular |
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What the symptoms of damage to a branch of the trigeminal nerve? |
Paralysis of the muscles of mastication Loss of corneal reflex Loss of sensation in face Trigeminal neuralgia |
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What are the symptoms of abducens palsy? |
Medial deviation of the affected eye, which causes diplopia |
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What is facial palsy also known as? |
Bell's Palsy? |
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What are the symptoms of bell's palsy? |
Cannot frown, close eyelid or bare teeth |
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What are the symptoms of VIII damage? |
Tinnitus, deafness, vertigo and nystagmus |
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What are the symptoms of glossopharyngeal damage? |
Loss of gag reflex and taste from back of tongue. Often present with symptoms of X and XI damage |
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What are the symptoms of vagus damage? |
Difficulty in swallowing or difficulty in speaking |
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What does accessory damage present as? |
Weakness in turning head and shrugging shoulders |
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What are the clinical aspects to consider with the hypoglossal nerve? |
Can be damaged during tonsillectomy. Presents as paralysis and atrophy of ipsilateral side of tongue. |