Block 12 - Musculoskeletal and nervous system (nervous 1) Flashcards
Where is information from the eye processed?
Lateral geniculate nucleus in the thalamus
Thalamus neurones –> Primary visual cortex and striate cortex (myelinated)
How does light get to the fovea?
Light –> Cornea –> Pupil –> Lens –> Fovea
Explain the visual fields of the eye, how they are seen and how they are processed by the brain
The left visual field of both eyes is seen by the right side of each eye and processed by the right side of the brain
What are the 3 layers of the eye?
What does each layer contain?
- Fibrous layer: Outer layer made from clear cornea and white sclera
- Vascular layer: Iris (colour), Ciliary bodies (muscles to change lens shape) Choroid (vessels at the back of the eye)
- Neural layer: Inner later containing retina (neurones send info to the optic nerve)
What are the 2 classes of movement of the eye?
What do they allow to happen?
Conjugate: Eyes move in the same direction
Disconjugate: Eyes move in opposite directions
Allows the image to stay on the fovea (increases resolution)
Define the 4 types of conjugate movements?
Vestibulooccular: Eye fixes whilst head rapidly moves (vestibular)
Optokinetic: Eye fixes whilst head slowly moves (visual)
Saccade: Eye directed towards various targets
Smooth pursuit: Allows you to follow a moving target
Define the 1 type of disconjugate movement
Vergence: Adjusts the eyes by convergence/divergence for objects far/close
What are the 2 movements of gaze stabilisation?
Vestibuloochlear
Optokinetic
What are the 3 movements of gaze shifting?
Saccade
Smooth pursuit
Vergence
Define adduction and abduction of the eye
Adduction: Eye moves towards the nose
Abduction: Eye moves away from the nose
Define intorsion and extorsion of the eye
Intorsion: Top of the eye moves towards the nose and the bottom of the eye moves away from the nose
Extorsion: Top of the eye moves away from the nose and the bottom of the eye moves towards the nose
What are the 8 areas of the brain which centrally control eye movements?
What are their roles
Supplementary eye field (decision and planning) Frontal eye field (execution) Prefrontal cortex (decision and planning) Caudate nucleus (modify motor commands) Posterior parietal cortex (visuospacial integration) Superior colliculus (sensory integration) Reticular formation (coordination) Brainstem nuclei (final common pathway)
Give 2 examples of muscular structures which open and close the eye
Iris and ciliary body
How is the ciliary body attached to the lens?
Ciliary body atatched to zonule fibres which are attached to the lens
How do sympathetic nerves control the pupil?
Superior cervical ganglion > Carotid plexus > Opthalamic nerve
How do parasympathetic nerves control the pupil?
Edinger-Westphal + occulomotor nucleus > Occulomotor nerve > Ciliary ganglion > Sphincter muscle
What is the pathology in Anisocoria?
One pupil is unable to constrict
What is the purpose of the accommodation reflex?
To increase resolution
What happens to the lens, ciliary muscles and suspensory ligaments when looking at a distant object and a close object?
What does this allow to happen?
Distant object (decrease focus): lens flat and thin, muscles relaxed, ligaments tense
Close object (increase focus) lens round and thick, muscles tense, ligaments relaxed
What is another word for ‘clouding’
Opacification
6 risk factors for cataracts
Age, trauma, diabetes, UV
Smoking, genetic
Explain how aqueous humour is produced
Aqueous humour produced in the ciliary processes behind the ciliary body in the anterior chamber (between lens, iris and cornea)
Where is the anterior chamber angle?
Between the iris and cornea
Where does aqueous humour circulate?
lens > iris > pupil > anterior chamber > trabecular meshwork > schlemm’s canal
What is the cause of the 2 types of glaucoma?
Primary open-angle: Trabecular meshwork clogged causing gradual vision loss
Acute angle-closure: Iris bows so anterior chamber angle closes and blocks drainage
4 risk factors for glaucoma
Hypertension, LT corticosteroid use, Increased intraoccular pressure, Severe myobia (nearsightedness secondary to eye injury/surgery)
How do you measure the intraoccular pressure?
How do you look at the retina?
Tonometry
Optical coherance tomography
What are the inner and outer vessels in the eye?
Inner = Retinal vasculature Outer = Chonocapillaries
What are the 9 cells/layers of the retina?
What does each layer do
Optical nerve fibres (ganglion cell axons)
Ganglion cells (send axons to the optic nerve)
Amacrine & Horizontal cells (integrate info across eye)
Bipolar cells (info from photoreceptors > ganglion cells)
Photoreceptors (rods and cones)
Pigment epithelium (outer layer supplies photorecep)
Bruch’s membrane
Choroid
What causes mild colourblindness?
If 2 cones see similar wavelenths of light
What are dichromats
What are the 3 types?
They only have 2 cone types
Protanopes = no red
Deutrenaopes = no green
Tritanopes = no blue
What are trichromats?
They have 3 cone types but the sensitivity of one is shifted towards the other
What are the 2 parts of the lateral geniculate nucleus?
Magnocellular: Bottom layer, input from A ganglion cells to see in greyscale and see WHERE
Parvocellular: Top layers, input from B ganglion cells to see in colour and see WHAT
Where is the central and peripheral visual field projected onto in the brain?
Central = back of the brain Peripheral = anterior brain
What are the 2 specialised visual fields of the occipital lobe?
What happens if there is a lesion?
V4: Ventral surface to see colour (lesion = achromatopsia)
V5: Lateral surface to see motion (lesion = akinetopsia)
What do the magno and parvo regions send information to?
What happens if there is a lesion in one of these areas?
Posterior parietal cortex: Lesion > optic ataxia (balints)
Do not know WHERE things are
Inferotemporal cortex: Lesion > visual agnosia
Do not know WHAT the object are
What 3 things make up the cerebral cortex?
Lobes, Pons and Brainstem
Define dyspraxia/apraxia
Inability to plan and sequence events
What happens to the eyes if there is a lesion in the frontal lobe?
Eyes deviated to the side of the distraction, away from the side of irritation (e.g. stroke in left, eyes to left)
Where do the primary motor neurones originate from?
Area 4 (Brodmans)
How are the corticospinal tract neurones arranged in the brain and spinal cord?
Brain = Cervical lateral and Sacral medial
Spinal cord = Cervical medial and Sacral lateral
Where are the cranial nerve motor nuclei?
Midbrain: 3,4
Pons: 5, 6, 7
Medulla: 9, 10, 11, 12
Where will the weakness be if there is a lesion to the cranial nerve nuclei?
Ipsilateral LMN weakness
What side will homonymous hemianopia affect?
Contralateral side to the lesion
What is the role of the frontal lobe? (9)
Intellectual, Motor praxis (planning and sequencing), Inhibition, Motor function, Personality, Social behaviour Language expression (Broca's), Bladder continence, Saccidic (voluntary) eye movement
What is the role of the occipital lobe? (2)
Sees visual information (doesn’t interpret)
Hand-eye coordination
What is the role of the temporal lobe? (4)
Primary senses and emotion (linked to autonomic = cry)
Memory
Facial recognition
What is the role of the parietal lobe? (4)
What is the role of the dominant and non-dominant lobe?
Interprets sensory information
Language reception (Wernicke’s)
Object recognition
Learned skills
Dominant: numbers
Non-dominant: Body image & environment awareness
Define sensory dyspraxia
Reduced visuospacial skills, ‘tone deaf’, can see a word but cannot interpret it (dyslexia)
Clumsy, vomiting, difficulty walking
Signs of a:
- dominant parietal lobe lesion (4)
- non-dominant parietal lobe lesion (2)
- signs found in both (4)
- Dyslexia, Acalculia (maths), Finger agnosia (cannot distinguish fingers), Poor left-right discrimination
- Sensory extinction, Visuospacial apraxia (don’t recognise half of the body)
- Agraphaesthesia (can’t write), Alterogenesis (can’t feel), Reduced 2 point discrimination, Stimuloagnosia (can see an object but it’s not in the right setting)
What do spinothalamic tracts sense?
How do they travel to the brain?
Pain and temperature
Cross the midline at the level they enter and ascend contralaterally to the thalamus > internal capsule > sensory parietal cortex
What do posterior column tracts sense?
How do they travel to the brain?
Joint position, deep pressure and vibration
Ascend ipsilaterally and decussate in the medulla > thalamus > sensory parietal cortex
What happens to the spinothalamic and posterior columns there is a lesion in the:
- upper brain sensory tracts?
- left spinal cord?
- Contralateral sensory deficit
- Contralateral spinothalamic loss below the level of the lesion
- Ipsilateral posterior column loss below the level of the lesion
Which cranial nerve nuclei originate in the medial brainstem and lateral brainstem?
Medial = motor Lateral = sensory
What do lesions in the red nucleus cause?
What does the red nucleus normally do with (2)?
Contralateral tremor (involved in motor coordination along with the basal ganglia and thalamus)
What system is involved in wakefulness?
Reticular activating system
Explain what happens in Weber (midbrain) Syndrome (2)
Ipsilateral occulomotor (III) palsy Contralateral motor dysfunction
Explain what happens in Wallenburg (lateral medullary) Syndrome (6)
Impaired gag reflex, Altered taste, Vertigo, Checkerboard sensory loss (ipsilateral face, contralateral body
Ipsilateral ataxia, Horners
What are the 3 parts of the cerebellum?
Vermis (vestibulocerebellum): Balance and equilibrium
Paravermis (spinocerebellum): Postural tone
Cerebellar hemispheres (ponto/neocerebellum): Fine coordiantion
Do cerebellar lesions present insilaterally or contralaterally?
Ipsilaterally
What does VANISH’D stand for?
Vertigo, Ataxia, Nystagmus, Intention tremor, Slurred Staccato Scanning Speeh, Hypotonia, Dysmetria (can’t control tone), Dysdiadochokinesis
What is the role of the thalamus?
Processes sensory and motor information
Give 3 examples of thalamic lesions
Ventroposterior lesion: Severe pain syndrome
Ventral posterolateral lesion: Surgery and deep pain stimulation for parkinsons
Anterior and contromedian lesion: Mood and behaviour disorders
What word describes pupil dilation and constriction?
Miosis = constriction Mydriasis = dilation
5 symptoms of a thalamic stroke
What area is impacted to case each?
Posterior = sensation Lateral geniculate = vision Medial geniculate = auditory Anterior lateral = movement control Anterior medial = limbic
Give an example of a tumour of the optic nerve
Glioblastoma
Positive and negative symptoms of vision
Negative = no vision Positive = irritation of visual structures
3 symptoms of a CNIII lesion
Eye down and out Pupil dilated (parasympathetic) Partial ptosis from levator palpebrae superioris lesion
6 causes of Horner’s
Idiopathic abnormal sympathetic supply Cluster headaches Internal carotid pathology Lateral medullary patholoy Pancoast syndrome C8/T1 pathology
Which fibres run on the outside of the nerve?
Parasympathetic
Is pupil constriction and dilation controlled by sympathetic or parasympathetic nerve innervation?
Constriction = parasympathetic Dilation = sympathetic
1 symptoms of a CNIV palsy
Can’t look down and in
2 causes of a CNVI palsy
3 symptoms
Pontine lesion or ischaemic mononeuritis (loss of blood to eye) in the elderly
Double vision
Neck ache and headache (tilt head to see normally)
Define diplopia
Double vision
Explain the difference between a LMN lesion and an UMN lesion in the facial nerve
LMN = weakness on the same side as the insult UMN = weakness on the opposite side of the insult (forehead sparing)
5 signs of a LMN facial nerve palsy
Ipsilateral Hyperacussis Lacrimation reduced Incomplete closure of the eye Abnormal taste and sensation to the anterior tongue
What are the 2 muscles which are paralysed in an accessory nerve palsy?
Right trapezius
Sternocleidomastoid
5 symptoms of a LMN lesion of the hypoglossal nerve
Tongue wasting Fasiculations Weakness Dysarthria Tongue deviated to the side of the lesion
Define dysarthria
Reduced speech
Explain the stages of grading muscle power
0: no movement
1: flicker of movement
2: movement with gravity removed
3: movement against gravity
4: movement against resistance
5: normal movement
What happens to \_\_\_\_ in a UMNL / LMNL? muscle bulk posturing fasiculations tone power reflexes (and plantar response)
Muscle bulk: reduced in both
Posturing: spastic in upper
Fasiculations: in lower (not upper)
Tone: increased in upper and decreased in lower
Power: reduced in both
Reflexes: increased in upper an decreased in both
Plantar: in upper
Explain what happens in decerebrate posturing
Upper brain stem damage (BAD)
Arms adducted and extended
Wrists pronated with finger flexes
Legs stiffly extended and feet plantar flexed
Explain what happens in decorticate posturing
Corticospinal tract damage (BETTER) Arms adducted and flexed Wrists and fingers flexed on chest Legs stiffly exttended and internally rotated Feet plantar flexed
3 things which degrade in motor neurone disease
What signs do they cause?
Degradation of corticol motor neurones (UMN signs)
Degradation of brainstem motor nuclei (LMN cranial nerve signs)
Degradation of anterior horn cells (LMN limb signs)
How are the cervical and sacral tracts tonographically organised in spinothalamic and posterior column tracts?
Spinothalamic = sacral lateral and cervical medial
Posterior columns = sacral medial and cervical lateral
Where does the spinal cord end in children and adults?
Adults = L1/L2 Children = L3/L4
What are the 3 signs in Brown-Sequard?
Ipsilateral motor and posterior column signs (UMN weakness and reduced position and vibration)
Contralateral spinothelamic signs (reduced pain and temperature)
Cervical disc prolapse (4)
Ipsilateral LMN signs at lesion
Ipsilateral UMN signs below lesion
Altered sensation of C5/6 dermatome
Weakness and wasting of biceps muscle and reduced biceps tendon reflex
Lumbar disc prolapse (4)
Positive straight leg raise sign
Ipsilateral weakness of L4/L5 muscles and dermatome
Ipsilateral loss of knee reflex
What is a syrinx?
What can happen to it?
What 2 things can this cause?
What 2 things are spared - why?
A cord within the spinal cord filled with CSF
Usually closes as we develop but can remain and tear in trauma
Causes hung sensory loss in the band affected and UMN signs below if lesion more medial and affects motor tracts
(spinothalamic and posterior not affected as lesion is medial)
3 things a lesion in the anterior spinal artery causes
Bilateral motor loss below
Bilateral spinothalamic loss below
Bilateral posterior retained
What are the 4 symptoms of parkinsons?
T: tremor at rest
R: rigidity
A: akinesia (no/slow movement)
P: postural instability
What causes a high steppage or antalgic gait?
Sensory loss in the feet
2 features of a cerebellar gait
Broad base and unsteady
What causes a waddling gait?
Proximal leg muscle weakness
What causes an atasia-abasia gait?
Psychological
Explain how to carry out Romberg’s test
What do the results mean?
Patient stands with feet together, looks ahead then closes eyes
Wobble = reduced sensory awareness in feet/ vestibular dysfunction
Define posture
Position of body parts with respect to each other, the environment and gravity
Define postural equilibrium
What is the difference between static and dynamic?
When all the forces acting upon the body are balanced
Static = balance when still
Dynamic = balance when moving
What do you need to maintain posture?
Extensor tone
What is the role of ventromedial tracts?
Where do they run from and to?
Run from the brainstem to the spinal cord
Tells the muscles information about posture so they can control posture through axial or proximal muscle movements
What do ventromedial tracts synapse with in the spinal cord?
Alpha LMN in the ventral horn
Describe the somatotropic arrangement of ventromedial tracts
Medial = postural control through axial/proximal muscles Lateral = voluntary control through distal muscles
What are the names of the 4 ventromedial tracts?
Vestibulospinal
Tectospinal
Pontine reticulospinal
Medullary reticulospinal
Which tracts keep the head balanced on the shoulders as the body moves to control head and neck posture?
Vestibulospinal
Tectospinal
What is the pathway of the vestibulospinal tract?
What is its role?
Vestibular labyrinth > medulla vestibular nuclei > spinal cord
Maintains upright posture through extensor motor neurones in the legs
What is the pathway of the tectospinal tract?
What is its role?
Retina > superior colliculus in midbrain > spinal cord
Directs the head and eyes to move to a particular location
What inputs are the pontine and medullary reticulospinal tracts controlled by?
Controlled by cerebellum and cortex inputs
Where does the pontine reticulospinal tract originate?
What is its role?
Pontine reticular formation > spinal cord
Increases antigravity reflexes of the spinal cord
Maintains standing posture against gravity by facilitating lower limb extensors
Where does the medullary reticulospinal tract originate?
What is its role?
Medullary reticular formation
Liberates antigravity muscles
Allows posture adjustment
(opposite to pontine)
What does the superior colliculus do?
Integrates sensory information to localise objects and orientate the body
What is the vestibular system?
What are the 2 parts?
Sensory system in the inner ear to detect gravity and control balance and motion
Otolith organs
Semi-circular canals
Where and how does the vestibular system send information to?
Hair cells (in otolith organs and semi-circular canals) convert motions to neural signals > vestibular branch of CN VIII
What are the 2 otolith organs
Utricle and Saccule
Define macula
Sensory epithelium in the otolith organs containing matrix and hair cells
How is the macula orientated in the utricle and saccule?
What movement does it sense?
Utricle = horizontal (senses horizontal movement) Saccule = vertical (senses vertical movement)
Explain how Otolith organs send neural signals
Hair cells penetrate into a gelatinous cap
The cap is covered in a layer of crystals
When the head tilts, gravity pulls the crystals and cap down causing the hair cells to bend
What causes a hair cell to depolarise/hyperpolarise?
Depolarise: hair cell bends towards longer kinocilium
Hyperpolarise: hair cell bends away from kinocilium
What is the centre of the utricle/saccule called?
Striola
How are the hair cells orientated towards the striola in the utricle/saccule?
How are they depolarised
Utricle = kinocilia towards the striola Saccule = kinocilia away from striola
Depolarised = hair bends towards the striola
What are the semi-circular canals sensitive to?
What are they called?
Head rotation and acceleration
Anterior, Posterior, Horizontal
Explain how the semi-circular canals work
Head rotation > cupula (gelatinous cap with cilia) bend in the opposite direction due to inertia of the endolymph
Hair cells bend then depolarise
Explain the purpose of the vestibulo-ocular reflex
When the head turns, the eyes move in the opposite direction to compensate for head movement
Explain how the vestibulo-ocular reflex works
(when the head turns to the left)
Semi circular canal > vestibular nuclei > occulomotor and abducens nuclei
Abducens: flexes R lateral rectus
Occulomotor: flexes L medial rectus
Eyes to the right
What is the vestibular-ocular reflex test called?
Caloric testing
What are the 2 postural reflexes?
Protective reflexes
Limb placing reflexes
What is the role of protective reflexes
Example
How do they work?
Maintains CoM over BoS
e.g. extends the hands and dorsiflexes head when you fall
Semicircular canals detect > medial vestibular nucleus > head position through neck muscles + lateral vestibular nucleus > trunk/limb muscles
Explain the 2 limb placing reflexes
Positive supporting action: Reflex to stiffen a limb when you place it on the ground
1a afferents and alpha motor neurones increase limb tone
Hopping reaction: If the feet are destabilised the body hops to a stable position
Give an example of adaptation of postural control
Vestibular system adapts e.g. sailors adapt to the motion of the sea
Explain the pathophysiology of Meniere’s syndrome
3 symptoms
Sudden decrease in endolymph disrupts the labyrinth in the inner ear
Vertigo, deafness, tinnitus
What is the treatment for Meniere’s syndrome?
No cure but can treat vertigo and nausea with antihistamines and prochorperazine (severe)
Define the feedforward/anticipatory response?
What brain area is important?
Postural adjustments made before voluntary movements
Reticular formation
Define the feedback/compensatory response?
What brain area is important?
Responses to sensory stimuli following the postural disturbance
Vestibular nuclei
Explain the pathophysiology of benign paroxysmal positional vertigo
3 symptoms
Crystals dislodge from otolith organs disrupting endolymph in semi circular canals
Nausea, vomiting, dizzy when moving head or rolling over
What is the treatment for benign paroxysmal positional vertigo?
Epley/Semont manovure to position the crystals in the cap
Define sound
An oscillation of pressure through a compressible medium
What is pitch?
Frequency
What is normal human frequency?
20 - 20,000 Hz
What is the amplitude of the sound wave called?
Intensity (volume)
Which bone makes up the ear?
Petrous part of the temporal bone
What is the role of the outer ear?
To convert sound waves (acoustic energy) to kinetic energy
What is the ear canal called?
External auditory meatus
What provides protection in the external auditory meatus?
Hair
Sebaceous glands
Cervminous glands
What shape is the eardrum?
What is it made from?
Concave
Collagen
What are the ossicles attached to?
Malleus attached to eardrum > Incus > Stapes attached to the oval window
What is the role of the middle ear?
Convert kinetic energy to hydraulic energy
Which bone does the tensor tympanii muscle attach to?
Malleus
What is the role of the acoustic/attenutation reflex?
To reduce the sound of your own voice during speaking (stapedius) or chewing (tensor tympanii)
What are the 2 branches of the facial nerve which run to the middle ear?
What are their roles?
Stapedial nerve > stapedius muscle
Chord tympanii > over tympanic membrane to anterior 2/3 tongue
What does the mandibular branch of the trigeminal nerve innervate?
Tenso tympanii muscle
What frequency does bone conduction hear better?
Lower
What is the role of the inner ear?
Convert hydraulic energy > electrochemical signals
What is the bony labyrinth of the inner ear made from?
Temporal bone
What is the membranous labyrinth of the inner ear made from?
Bony labyrinth filled with endolymph (contains K) separated by perilymph (contains Na)
Scala media = endolymph (middle)
Scala vestibuli and tympani = perilymph (either side)
What are the 2 membranes in the inner ear?
What do they separate?
Reissner’s membrane: separates the vestibuli and media
Basilar membrane: Separates the media and the tympani
What is the organ of corti?
Sensory epithelia on the basilar membrane containing hair cells which convert vibrations to nerves
Outer hair cells > Inner hair cells > Nerve
Draw the cochlea
Find an image dumbass i cannot afford pro
Define ultrasound and infrasound
Ultrasound: Frequency above the human hearing range
Infrasound: Frequency below the human hearing range
Explain how a sound wave passes through the cochlea
Stapes > Perilymph > Down cochlea along scala vestibuli (upper part) > Basilar membrane > Back up cochlea along scala tympani (lower part) > Round window
Explain the pathway of the vestibulocochlear nerve
What is the mnemonic?
Ear > Cochlear nuclei in brainstem >(DECUSSATE)> Superior olivary complex > Lateral lemniscus > Inferior colliculis > Medial geniculate nucleus > Auditory cortex in the temporal lobe
SLIM
Explain how sound is localised in the vertical plane
Pinna, Head, Shoulders, Torso
Use the way sound bounces off them to work out where the sound is
Explain how sound is localised in the horizontal plane
Decussation allows soumd inputs to be compared in the superior olivary nuclei
Medial: detects differences in TIME (low freq sound)
Lateral: detects differences in INTENSITY (high freq)
Define low and high frequency
Low less than 800
High more than 1000
(middle by both mechanisms)
Give 7 examples of sensioneural hearing loss
Age, Childhood/Inflammatory disease Congenital, Meniere’s, Noise, Ototoxic drugs, Physical trauma
Is disruption of the tympanic membrane a conductive or sensorineural hearing loss?
Conductive
Which test is Rinne’s test and which is Weber’s
Mastoid process = Rinne
Forehead = Weber
What does it mean if the normal ear sounds louder in Weber’s test?
Why?
Sensioneural
Sound travelling directly to inner ear via skull bones is masked by ambient noise entering the middle ear
What does it mean if the defective ear sounds louder in Weber’s test?
Why?
Conductive
Reduced sound travelling through the middle ear so sound travelling from tuning fork to inner ear via skull is louder
Why does Rinne’s test not distinguish between normal and sensioneural?
Air and bone conduction are both bad in sensioneural
