Neuro Flashcards
Definition of Brainstem
‘That part of the CNS, exclusive of the cerebellum that lies between the cerebrum and the spinal cord.’
What is the primary function of the superior colliculus
important in the coordination of eye and head movements at the same time (think about watching tennis)
What is the primary function of the inferior colliculus
auditory reflexes - if there is a loud bang you tend to look in the direction of the bang immediately
What are the functional subtyoes of the cranial nerves?
- General Somatic Afferent (GSA)
- Sensation from skin and mucous membranes
- General Visceral Afferent (GVA)
- Sensation from GI tract, heart, vessels and lungs
- General Somatic Efferent (GSE)
- Muscles for eye and tongue movements
- General Visceral Efferent (GVE)
- Preganglionic parasympathetic
- Special Somatic Afferent
- Vision, hearing and equilibrium (only the cranial nerves)
- Special Visceral Afferent
- Smell (CN I) and Taste (comes from THREE cranial nerves that all go back to the nucleus solitarius)
- Special Visceral Efferent
- Muscles involved in chewing, facial expression, swallowing, vocal sounds and turning the head
Which CN Nuclei are SSA ?
Vestibulocochlear
Which CN Nuclei are GSA ?
Trigeminal
What is the function of the nucleus ambiguus?
SVE - Vocalisation and swalling
What might explain the following ssymptoms?
- Vertigo
- Ipsilateral Cerebellar Ataxia - problem with gait on the same side of the body as the lesion (broad-based gate - they tend to shuffle)
- Ipsilateral loss of pain/thermal sense (face)
- Horner’s Syndrome - loss of sympathetic innervation to the head and neck
- Ptosis
- Lack of sweating around the eye
- Hoarseness
- Difficulty swallowing
- Contralateral loss of pain/thermal sense in the trunk and limbs
Lateral Medullary Syndrome
Caused by thrombosis of the vertebral artery or the posterior inferior cerebellar artery. (PICA)
How many paired spinal nerves are there?
31
At what level does the spinal cord end ?
L1/L2
Sensory fibres enter via dorsal or ventral ?
Dorsal
Motor fibres enter the spinal column via dorsal or ventral ?
ventral
What are the little protrusions of pia mater called that tether the spinal cord and hold it in the middle of the subarachnoid space
denticulate ligaments
Name two descending tracts Associated with voluntary movement. Where do thes decussate?
Lateral corticospinal tract
Anterior/Ventral corticospinal tract
Decussate in the medulla.
Which spinal tract is responsible for carrying afferent pain and temperature information ?
Where does it decussate?
Spinothalamic
Decussates immediately enters the spinal cord
Which spinal tract is responsible for carrying afferent information about touch, vibration and pressure?
Where does it decussate?
Dorsal Column (sometimes called the medial leminiscus pathway)
Decussated in the medulla
What are the two subdivision s of the dorsal columns and which carries information about upper/lower limbs?
Cueneate (medial) - arm, upper trunk
Gracile (lateral) - lower trunk
What might deficit might result form syrinomyelia ?
Syringomyelia is caused by an enlargement of the central canal called a syrinx.
Leads to loss of temperature sensation in the arms but not the legs.
The large space in the middle is selectively damaging the spinothalamic axons that are crossing over at the level of the lesion but it does not affect the fibres that have already crossed over and are travelling up in the spinothalamic tract
What arteries supply the brain anteriorly and posteriorly?
Anteriorly = Internal carotid
Posteriorly = Vertebral arteries
What links the sigmoid sinus to the cavernous sinus ?
The petrosal sinus
What si teh definition of stroke?
Rapidly developing focal disturbance of brain function of presumed vascular origin lasting more than 24 hours
What is the definition of a TIA ?
Rapidly developing focal disturbance of brain function of presumed vascular origin that resolves copletely within 24hrs
What proportion of strokes are due to infarction vs haemorrhage?
85%infarct 15%haemorrhage
Which arteries supply the following areas?
Disturbance of which artery would cause paralysis for the contrlateral leg?
Anterior Cerebral artery
Disturbance of which artery would cause paralysis for the contrlateral arm ?
Middle Cerebral artery
Disturbance of which artery will result in aphasia?
Left middle cerebral artery
Describe homonymous hemianopia
homonymous hemianopia, is hemianopic (half) visual field loss on the same side of both eyes
What is visual agnosia
an impairment in recognition of visually presented objects.
I haemorrhagic stroke, which sort might cause immediate effects and which might cause delayed?
`Extradural - immediate - arterial
Subdural - delayed - venous
Name the 3 bones in the middle ear and the membranes they are attached to.
Malleus attaches tympanic membrane
Incus attaches malleus and stapes
Stapes attaches oval window and incus
Which nerve supplies the lacrimal glands and which parasympathetic ganglion?
Facial nerve via pterygopalatine ganglion
What type of cells line the ventricles of the brain ?
Ependymal cells
What is the route of CSF ?
Lateral ventricle
Interventricular foramina
Third ventricle
cerebral aqueduct
Fourth ventricle
Subarachnoid space
What are circumventricular organs?
Areas of the brain where capillaries lack BBB properties
What organs make up the diencephalon?
Thalamus - either side of the third ventricle
Hypothalamus
Subthalamic nuclei
What is narcolepsy and what type of neurons might be involved in this?
Rapid onset of REM sleep often triggered by emotions
The orexin neurones in the lateral hypothalamus regulate sleep/wake cycle. Patients with narcolepsy do not have a orexin neuropeptide
What receptors sense hot temperature and chilli
TRPV
What receptors sense cold and menthol
TRM8
What are the most common cutaneous receptors and skeletal muscle receptors
Cutaneous - Polymodal C-Fibre (pressure, temp, chemical stimulus)
Skeletal muscle receptor - Chemoreceptor (for lactic acid)
What is the stimulus threshold?
The weakest stimulus detectable 50% of the time. Varies by body location and person-to-person.
What is a receptive field?
The area from like to stimulus elicits neuronal response. These overlap
Explain the concept of lateral inhibition
Activation of one neuronal unit inhibits activation of adjacent neuronal units. Mediated by Interneurones within the dorsal horn spinal-cord
What is it two-point discrimination?
Ability to detect two stimuli as distinct i.e. the minimum distance required between two stimuli in order to perceive they’re separate. Relies on:
- Peripheral mechano receptors
- Spinal posterior column
- Cortical function
What results from the loss of function mutation NaV1.7?
Born with an inability to feel pain- very rare
What type of receptor responds rapidly to neural adaptation?
Phasic receptors
What type of receptor responds slowly to neural adaptation?
Tonic receptors
What is neural adaptation?
If a stimulus of constant strength is maintained for a period of time the frequency of action potentials diminishes
What are the different nerve fibre types and their function?
α- Proprioception, somatic motor
β- Touch, pressure
γ- Motor to muscle spindle
δ- Pain, cold, touch
What is the function of C-type nerve fibres
Dorsal root- Pain, temperature, mechanoception
Sympathetic- Postganglionic sympathetic
Which nerve fibre transmits fast painful stimuli?
A-δ
What is the Gate Control Theory?
A non-painful stimulus can inhibit transmission of a painful stimulus. Ie large Aß fibres can reduce transmission of Aδ and C fibres within the dorsal horn
What are the different types of pain? (6)
Nociceptive
Muscle
Superficial somatic
Visceral
Referred
Neuropathic
What is Brown-Sequard syndrome?
Hemisectio nof the spinal cord. reduces sensation on one side and loss of pain sensation on the other.
How does Ketamine cause ‘dissociative analgesia’?
Ketamine = NMDA antagonist. Long tem potenitation of NMDA = hypersensitivity to pain . Glutamate (acts on NMDA) is the major NT in the spinal cord.
What is the WHO analgesic ladder for cancer pain relief?
1) Paracetamol, aspirin and ibuprofen
2) Codeine and tramadol
3) Morphine
What is myalgia
muscular pain
What is the wind-up phenomenon?
Where repetitive stimulation of wide dynamic range neurones induces increased evoked response and post-discharge with each stimulus
Related to neuropathic sensitization
Describe neuropathic pain?
Pain in an area of neurological dysfunction. Has poor response to normal analgesic drugs. Can last after the area has healed completely
- sharp
- burning
- electric shock
- squeezing
What is ALLODYNIA
Stimulus does not normally provoke pain
PARAESTHESIA
Abnormal sensation but not normally painful eg tingling
What is Complex Regional Pin Syndrome?
Severe form of neuropathic pain with neurogenic inflammation.
Overexpression of nociceptive endings
Treated with medication and spinal cord stimulation
Allodynia.
Temperature Asymmetry
Skin Colour Change
Sumomotor changes / oedema
What drugs are used to treat neuropathic pain?
Antidepressants
Anticonvulsants
Opiod trial
Hybrid (Tapentadol)
Topical (e.g. Capsaicin)
How do capsaicin patches work to treat neuropathic pain?
Capsaicin binds to TRPV1 receptor on nerve endings allowing influx of calcium. Capsaicin has direct toxicity to mitochondria, which reduces the number of nerve endings
In the hierarchical organization of the motor cortex, what makes up levels 4, 3, 2, and lowest?
Level 4 - Assocaition cortex
Level 3 - Motor cortex
Level 2 - Brain stem
Lowest = Spinal cord (reflexive movements)
What funciton does the Assocaition cortex have in integrating movement?
Contains the parietal and frontal cortex. Influences the planning and execution of movements
What funciton does the Motor cortex have in integrating movement and what are the component parts ?
Primary motor cortex
Premotor cortex
Supplementary Motor Area
This is where voluntary movements are initiated
What is level 2 and what is its role in movement ?
Brainstem - Integration of inputs from the vestibular systme, visual and auditory system
What are Betz cells and wehre are they found?
Pyramidal cells - long axon
Found in 5th layer of grey matter. Where the descending motor mathways originate from
What is the name of the descending motor pathway?
Corticospinal tract
What are the 2 division of the corticospinal tract and what does each innervate
Lateral corticospinal tract - (decussates in the medulla) - Arms and Legs
Anterior cortical spinal tract (decussates spinal cord) - Trunk and proximal part of arms and legs
What is broadman’s area 4 and what is its funciton
Primary motor cortex, also known as M1
Control of fine, discrete, voluntary movements.
What is in Broadmann’s area 6? Where are they located and what are their function?
- *Premotor Cortex**
- Located anterior to the primary motor cortex
- Involved in planning movements; regulates externally cued movments
- *Supplementary Motor Area**
- Also anterior to the primary motor cortex, but more medial
- Involved in planning complex movements and programming sequencing of movements. Regulates internally driven movements (e.g. speech)
What are the positive and negative signs of an upper motor neuron lesion?
Initial Loss of function (-)
- Paresis: graded weakness of movements
- Paralysis (plegia): complete loss of muscle activity
After a few weeks…
Increased abnormal motor function (+) (due to loss of inhibitory descending inputs)
- Spasticity: increased muscle tone
- Hyperreflexia: exaggerated reflexes
- Clonus: abnormal oscillatory muscle contraction
- Babinski’s sign
What is Babinki’s sign
Normally if you stroke the plantar side of the foot = flexion
In upper motor lesion = extensor plantar response. Toes will fan and the big toe will go up
What are the symptoms of a lower motor neuron lesion?
- Weakness
- Hypotonia (reduced muscle tone)
- Hyporeflexia (reduced reflexes)
- Muscle atrophy
- Fasciculations: damaged motor units produce spontaneous action potential resulting in a visible twitch
- Fibrillations: spontaneous twitching of individual muscle fibres, recorded during needle electromyography examination
What is Motor neurone disease
Progressive neudegenerative disorder characterised. Can affect upper, lower mn or both .
What structures form the basal ganglia?
A number of structures on top of the brainstem :
- Striatum: caudate and putamen
- Globus pallidus externa (GPe) and globus pallidus interna (GPi)
- Substantia nigra pars compacta (SNc) and pars reticulata (SNr)
- Subthalamic nucleus (STN)
What is the funciton of the basal ganglia ?
- Elaborating associated movements (e.g. swinging the arms when walking, facial expression matching emotions)
- Moderating and coordinating movement (suppressing unwanted movements)
- Performing movements in order
What are the two pathways of the basal ganglia and which is inhibitory/excitiatory ?
Direct pathway - no project to STN excitatory
Indirect pathway - do project to STN - Inhibitory
Name two disorders of the basal ganglia
Hypokinetic (parkinson’s disease)
Hyperkinetic (Huntington’s)
What causes Parkinson’s and list some of the symptoms
Degeneration of dopamine neurons in Substantia Nigra
Bradykinesia - Slowness of movement / shuffling gait
Hypomimic face - expresionless
Akinesia - Difficulty in the initiation of movements
Rigidity
Tremor at rest
What is Huntington’s disease?
Neurodegenerative genetic disorder
Abnormality in chromosome 4. Autosomal dominant
Degeneration of GABAergic neurons in the striatum (caudate first then putamen later)
What are the main signs of Huntington’s disease?
Choreic movements (chorea): rapid jerky involuntary movements of the body. Hands and face affected first then legs and the rest of the body
- Speech impairment
- Difficulty swallowing
- Unsteady gait
Later on, cognitive decline and dementia
What are the three horizontal lobes of the cerebellum?
Anterior
Posterior
Flocculonodular
What are the three sagital zones of the cerebellum?
Vermis
Intermediate hemisphere
Lateral hemisphere
What are the 3 funcitonal divisions of cerebellum
Vestibulocerebellar
Spinocerebellar
Cerebrocerebellar
What is the function of th vestibulocerebellum
The flocculonodular lobe
Function:
- regulation of gait, posture and equilibrium
- coordination of head movements with eye movements
What parts of the cerebellum make up the spinocerebellum? What inputs project into each area?
What is the function of the spinocerebellum?
Vermis and Intermediate hemisphere.
Vermis: Spinal afferents from axial portions of the body, trigeminal, visual and auditory inputs
Intermediate hemisphere.Spinal afferents from the limbs
Function:
Coordination of speech
Adjustment of muscle tone
Coordination of limb movements
What part of the cerebellum makes up the cerebrocerebellum? What is the function of this area?
The lateral hemisphere
Coordination of skilled movement
Cognitive function, attention processing of language
Emotional control
What results from flocculonodular/Vestibulocerebellar Syndrome?
causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when sitting with eyes open)
What are the syndromes of spinocerebellar syndrome ?
affects mainly the legs, causes abnormal gait and stance (wide-based)
What are the symptoms of cerebrocerebellar Syndrome?
Damage affects mainly arms/skilled coordinated movements (tremor) and speech
What cells make up the olfactory epithelium?
Bipolar olfactory neurons
Sustentacular cells
Basal cells
What is the olfactory neural pathway
Olfactory bulb
♦
Olfactory tract
Medial Lateral
♦ ♦
Olfactory stria
♦ ♦
Orbitofrontal cortex Pirifrom
♦
Connections to brainstem and higher autonomic reflexes
Where is the limbic system found and what structures does it compise?
A rim of cortex adjacent to the corpus callosum and diencephalon
Olfactory bulb
Hypothalamus
Amygdala
Hippocampus
Thalamus
What is the limbic system responsible for?
- Maintainance of homeostasis
eg modulation of pituitary hormone release and initiation of feeding and drinking - Agonistic (defence and attack) behaviour
- Sexual and reproductive behaviour
- Memory (to previous situations modifies our response)
What is the Papez circuit?
a neural circuit for the control of emotional expression
Mammilary bodies (hypothalamus)
(MTT MAMMILO-THALAMIC TRACT)
Ant Thalamic Nucleus
Cingulate gyrus
Hippocampus
(FORNIX )
MATCH
Name four types of mechano receptors
`Merkel disc
Pacinian corpuscle
Meissner’s corpuscle
Ruffini ending
What and where is the locus coeruleus?
is a nucleus in the pons (part of the brainstem) involved with physiological responses to stress and panic.
What structures make up the basal ganglia circuit
What is another name given to lower motor neurons?
Alpha motor neurons/ventral horn cells.
What are extrafusal and intrafusal skeletal muscel fibres?
Extrafusal - innervate skeletal muscle
Intrafusal - Skeletal muscle fibres that serve as specialist sernsory organs (proprioceptors) that detect amount and rate of change in length.
How are the alpha motor neurons organised in the ventral horn?
Flexor muscles- posterior part of the horn
Extensor muscles- anterior part of the horn
Distal muscles- lateral part of the horn
Proximal part of the horn- medial part of the horm
Define a motor unit:
A single motor neuron together with all the muscle fibres that it innervates
What are the 3 types of motor unit?
-
Slow (S, type I)
Small dendritic trees, small diameter cell body.
Small amount of force but don’t fatigue easily. Also postural muscles.
- Fast, fatigue resistant (FR, type IIA)
Moderate tension but fatigue resistant
- Fast fatiguable (FF, type IIB)
High tension. Easily fatigued.
What are the 2 mechanisms by which the brain regulates how much force a single muscle can produce.
- *Recruitment** - of more motor units. Smaller units are recruited first (generally slow twitch)
- *Rate coding -** The rate of AP’s down a the nerves, generally slower units fire at lower frequencies.
What is the size principle of motor recruitment ?
Smaller units are recruited first, hence why you can only use fine control at low levels of force.
What fibre type changes can occur in muscle? (plasticity of motor units)
Training: Type IIB to IIA (fatiguable to fatigue resistant)
Spinal cord injury/microgravity: Type I to type II
What muscel type changes occur with age?
Aging: loss of type I and type II fibres; preferential loss of type II fibres- larger proportion of type I fibres in aged muscle
Which motor tracts are responsible for voluntary movement and what are these called?
1 Pyramidal tracts
1A) = Lateral corticospinal tract
1B) Anterior corticospinal tract
Which motor tract is responsible for automated arm movements in response to changes in balance and what is this called?
Extrapyramidal tract 2A - Rubrospinal Tract
Which motor tract is responsible for cordinating automated movements eg. in response to posture, and what is this called?
Extrapyramidal tract 2B - reticulospinal tract
Which motor tract is responsible for regulating posture to maintain balance and what is this called?
Extrapyramidal tract 2C Vestibulospinal tract
What are the components of a reflex arc?
1) Sensory receptor
2) Sensory neuron
(3 Interneuron -sometimes)
4) Motor neuron
5) Effector (muscle or gland)
What is the time interval between stimulus and response of a single synapse reflex ?
~0.7ms
What are the two waves seen in a Hoffman reflex when you stimulate a nerve and in which order do they appear?
Direct motor response going from the motor neurone that has been stimulated, directly to the muscle causing contraction
This is the M wave (motor wave)
A short time later you will see another response in the EMG and there will be another twitch
This is caused by the action potential in the sensory neurone going back to the spinal cord and exciting the motor neurone = H wave
Name a polysynaptic reflex
Flexion withdrawal and crossed extensor
What higher centres and pathways are involved in supraspinal control of reflexes?
- Cortex- corticospinal (fine control of limb movements, body adjustments)
- Red nucleus- rubrospinal (automatic movements of arm in response to posture/balance)
- Vestibular nuclei- vestibulospinal (altering posture to maintain balance)
- Tectum- tectospinal (head movements in response to visual information
What is the function of gamma motor neurons?
Adjust the spindle so it remain taught thoroughout contraction, regardless of muscle length, thus maintaining senstivity. = GAMMA REFLEX LOOP
What are the semicircular canals stimulated by?
Angular velocity = head rotation
What are the otolith organs stimulated by?
Linear acceleratino of the head, and tilt.
How do the semi-circular canals send signals about rotation ?
If head turned towards the right - Right horizonatal canal is activated and Left horizontal canal is disfalicitated.
If FWD tilt - anterior canal is activated.
If perfect horizonatal tilt = Ant. and POst. both activated on that side
What is the vestibulo-ocular reflex?
Superior and medial neurons project to motor nuclei supplying extraocular muscles in order to stabilise the eyes when there is head movement
What are the result of a lesion in CN VIII eg due to herpetic virus.
CN VIII supports tonic activity, so if it is lost on one side the remaining input from the other is the equivalent signal of a head turn
Results in:
- Imbalance which righting reflex tries to correct
- vestibular nystagmus - ie the eyes are continutally drifting to the side, then corrected.
What test might be used to examina patient with labyrinth lesion?
Head rotation test. The head is rotated toward the side with the lesion . The patient’s eyes lose fixation, go with the head and after the movement the patien makes saccades back to the fixation point.
