00-neuroanat-02
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- symptoms of voluntary motor pathway lesion
- decrease in speed and strength of contraction, loss of fine motor control, impaired muscle tone
- overall result of voluntary motor pathway lesion
- disturbs ability to perform motor tasks
- overriding function of voluntary motor path
- modulates and directs musc. action, esp. sm. musc. of hand
- vestibulospinal pathway – role
- coordinate postural movements that maintain balance
- sensory input- vestibulospinal path
- semicirc. canals, CNVIII-vestibular nucleus of medulla
- neurons within mostly lateral (some medial) vestibular nucleus send axons where
- caudally in ventral funinculus of spinal cord
- purpose of vestibulospinal path neurons
- excitatory innervation to extensor ‘antigravity’ musc.
- where does the reticulospinal pathway originate
- in the reticular formation of the pons/medulla
- what type of musc. mainly served by vestibulospinal pathway
- extensors
- where do the pontine reticular formation neurons pass?
- caudally in ventral funinculus with vestibulospinal path neurons
- function of reticulospinal path neurons
- also provide innervation to lower motor neurons to antigravity neurons, but primarily to flexors
- what is the reticular formation important for
- wakefulness, arousal
- what inhibits the vestibulospinal and pontine reticulospinal systems to excite LMN of trunk?
- the cerebrum and cerebellum inhibit the vestibulospinal/reticulospinal systems (which innervate the “antigravity musclesâ€)
- what occurs in midbrain lesion where cerebrum cannot inhibit vestibulo/reticulospinal systems
- no inhibition = hypertonia, hyperflexia of extensors
- decerebrate posture
- hyperextension of spine and limbs
- what cures decerebrate rigidity
- destroying the lateral vestibular nucleus
- hemiplegia
- half-sided paralysis
- condition where paralyzed limbs are limp, then later become spastic
- “spinal shockâ€
- spastic
- hypertonia, stiffness
- what generally occurs with an upper motor neuron lesion after the spinal shock has resolved?
- tendon reflexes greatly exaggerated
- do muscles atrophy with upper motor neuron lesion?
- no. the lower motor neurons are still passing growth factors to muscles
- fasciculations
- small twitches
- normal plantar response (negative babinsky sign)
- normally, toes flex when sole of foot stroked firmly
- babinsky sign
- if upper motor neuron lesion, toes extend up and fan out = “positive babinsky signâ€
- other symptoms of decerebrate rigidity
- back arched, hyperextended, unconscious (never regained.)
- which pathway in the spine is responsible for pain, temperature, and simple touch
- spinothalamic pathway
- where does the pain, temp, simple touch pathway reside
- lateral portion of spinal cord
- where is the spinal pathway for descriminating touch
- dorsal column pathway
- what disease knocks out the pathway for discriminating touch
- syphillis
- if dorsal column pathway is damaged what is the gross motor result
- difficult to walk, impossible to run
- what is discriminating touch
- texture size shape, but also footsteps
- in what tract do the fibres of the spinothalamic pathway pass
- Lissauers tract
- arrangment of fibres in spinothalamic path
- somatotropic, sacral outermost
- how many neurons in a typical spinothalamic path
- 3
- 3 paths of spinothalamic path
- 1. lissauers tract in 2. cross midline to lateral leminiscus up to thalamus, 3 thalamic neurons to parietal cortex
- spinothalamic senses
- pain temperature and simple touch
- dorsal column path & purpose
- discriminating touch and conscious proprioception
- # of neurons in dorsal column pathway
- usually three
- three neurons of dorsal column pathway
- 1. into root, up in dorsal column to lower medulla: nucleus gracilis and nucleus cuneatus2. 2nd neurons decussate as internal arcuate fibres, pass upwards in medial lemniscus to ventral posterolateral thalamus 3. thalamus parietal cortex
- negative symptom
- loss of feeling – deadness
- positive symptom
- pins and needles (paresthesia) burning feeling
- spinothalamic lesion produces
- lack of awareness of pain and temperature
- result of spinothalamic lesion
- cold-blue extremities, hair loss, painless burns
- dorsal column lesions produce?
- descriminatory sensory loss, loss of two point descriminatory touch, may not be able to distinguish items held in hand
- inability to descriminate items found in hand
- astereognosis
- burning sensation (sometimes sock/glove distribution)
- can be due to peripheral nerve problems – assoc. w/diabetes
- if can’t sense where limbs are, suspect?
- dorsal column problem – disturbed proprioception
- ignoring one half of body
- perceptual rivalry – sensory inattention
- if loss of descriminatory sense, sensory inattention, but not pain and temperature loss, suspect?
- contralateral parietal cortex lesion
- selective deficit of face/arm leg or trunk, suspect?
- selective lesion of cortex
- if hemisensory loss of all modalities, suspect
- contralateral thalamic lesion
- if all problems are on one side, suspect
- problem above the brainstem
- if losing cranial nerve function on one side, and losing opposite side of body, suspect?
- brainstem problem
- lesion of pons would cause
- complete sensory loss to contralateral limbs, loss of pain and temp on opposite side (alternating lesion)
- if pain temp and simple touch lost below a certain level, suspect?
- contralateral spinothalamic tract lesion below the given level
- if all modalities are lost below a certain level and pain and temp on opposite side, loss of proprioception on same side
- partial cord lesion (half of cord)
- if bilateral loss of pain and temp, but proprioception spared, suspect
- central cord lesion
- main functions of frontal lobe
- voluntary motor control, personality, intellect, verbal communication
- main function of parietal lobe
- somatesthetic perception (body, cutaneous/musc., sensations, understanding and utterance of speech
- temporal lobe functions
- audio and visual memory, interpretation of audio sensations
- occipital lobe functions
- conscious seeing, integration of movements, focus eye, correlation of visual images with previous visual experience and other sensory stimuli
- insula
- memory, integration of cerebral activities
- what and where is broca’s area
- motor speech area, left inferior gyrus of frontal lobe – just anterior to lateral sulcus
- what do parahippocampal gyrus and cingulate gyrus do?
- relay necortex info- hippocampus and limbic system
- function of the basal ganglia
- maintain muscle tone and program subconscious sequential postural adjustments
- hypothalamus is near what?
- 3rd ventricle
- what does the pineal gland produce
- melatonin – related to diurnal or nocturnal cycles
- what is the diencephalon comprised of
- thalamus, hypothalamus, pineal gland (3rd ventricle is within)
- what are the cerebral peduncles?
- long descending tracts of white matter from the cortex to the pons and medulla
- where is the tegmentum
- immediately behind the peduncels
- what cranial nerves live within the pons
- V, VI, VII, VIII
- cranial nerves assoc. with medulla
- VIII – XII
- which is the largest subdivision of the CNS?
- cortex
- three ways the cortex can be divided
- functional areas, cortico-thalamic and thalamo-cortical connections and histological differences
- what neurons relay information vertically within the cortical columns
- stellate interneurons
- what neurons inhibit spread of signals laterally within cortical columns
- non spiny interneurons
- another name for central sulcus
- fissure of rolando
- how are non spiny neurons insulated
- GABA inhibitory neurotransmitter (stops lateral spread of info signals out of column)
- what causes epileptic seizures
- break down of non-spiny gabargenic neurons
- what is another name for giant pyramidal cells
- betz cells – control voluntary movement contralateral on anterior wall of central sulcus
- where are motor versus sensory cortex areas in relation to central sulcus
- motor-precentral gyrus, sensory -post central
- what area of frontal cortex is responsible for contralateral conjugate deviation of eyes
- frontal eye field of posterior part of middle frontal gyrus
- famous yorkshire lunatic asylum neurologist
- hewlings-jackson
- how does a focal seizure cause symptoms?
- spreads through brain, disrupts normal function, activating motorneurons and muscle – causes convulsions
- what breaks down during an epileptic seizure
- GABA – localized inhibitory surround
- how is it possible to tell the site of the epileptic focus in the cortex?
- first sign of abnormal motor convulsion or sensation occurs here: i.e. hand or foot
- name given to obvious seizure spread slowly across cortex
- Jacksonian march
- Jacksonian seizures probably occur after many focal seizures why?
- Gabargenic response- gradually breaks down insulative barrier – change in excitability – facilitates increasingly easier seizures over time
- 3rd ventricle within which part of brain
- midbrain
- 4th ventricle within which part of brain
- hindbrain
- function of cerebral lobes
- voluntary movement, higher intellectual processes and personality
- basal nuclei do what
- muscle coordination during body movement
- which structures monitor respiratory rates
- pons and medulla
- which part of brain concerned with hearing and seeing
- midbrain-superior colliculi, hearing:inf. colliculi
- seritonin function
- influences body temperature, sensory perception and sleep regulation
- end of spinal cord called
- conus medularis
- where the apneustic and pneumotaxic centres
- within the pons
- where is the breathing rhythmicity area?
- medulla
- what structure regulates vasoconstriction
- medulla
- what system generates emotions
- limbic
- which system alerts brain
- RAS
- term for progressive ease of seizures
- kindling
- most effective means of producing kindling effect
- electrical impulses to limbic system
- significance of kindling
- treat seizures early
- what lobes does the middle cerebral artery pass between
- temporal and parietal through lateral fissure
- middle artery supplies?
- internal capsule, basal nuclei, temporal, frontal and parietal lobes on lateral surfaces
- middle cerebral artery damage – what effects?
- contralateral hemiplegia, hemianasthesia, aphasia (loss of language), neglect of contralateral limbs
- anterior cerebral artery supplies?
- medial side of hemispheres, runs above optic nerve, follows corpus collosum, branches to internal capsule and basal nuclei: medial orbital frontal, parietal
- one half of body mostly not working, but leg spared – why?
- middle cerebral artery occlusion – anterior cerebral serves medial frontal lobe where leg is mapped.
- path for speech
- cochlea – prim. aud. cortex – wernickes area – arcuate fasciculus – broca’s – motor cortex
- path for reading written word
- primary visual cortex – angular gyrus – wernickes area
- wernickes area – function
- associates visual form of word with corresponding auditory pattern
- auditory area – where
- superior temporal gyrus
- damage in what area might damage arcuate fasciculus
- supramarginal gyrus
- which areas of cortex included in zone of language
- brocas, facial motor cortex, angular gyrus, wernickes, auditory cortex
- loss of capacity for spoken language
- aphasia
- what artery supplies all cortical areas involved in speech
- middle cerebral
- what does main artery thrombosis of the middle cerebral artery give rise to?
- global aphasia
- what is language?
- formulation, comprehension and use of words and symbols as part of a rule bound socially shared code
- what is speech
- motor process involving production of sounds for the purpose of transmitting language
- creation of new words
- neologisms
- what are aphasias usually caused by
- lesion in one or more areas of dominant cerebral hemisphere
- where is the supramarginal gyrus
- above the lateral fissure
- what might a lesion to Broca’s area cause
- transient aphasia or sometimes apraxia of speech
- what is apraxia
- faulty programming of speech musculature for sequential movements required by speech
- what is the basic cause of apraxia
- higher programming level which effects motor production
- what are speech difficulties caused by muscular disturbances called
- dysarthria
- what might effect muscles that control speech
- paralysis, weakness, incoordination, varying speed
- what might be a sign of mild dysarthria
- chronic hoarsness
- difference between apraxia and dysarthria
- disarthria speech errors are consistent and regular, not predictable. Language itself is not impaired – only speech.
- cranial nerves associated with midbrain
- III, IV
- cranial nerves associated with pons
- V, VI, VII, VIII
- cranial nerves associated with medulla
- IX, -XII
- if an alternating lesion, where is it
- brainstem
- describe alternating lesion characteristics
- weakness on same side for the cranial nerve, weakness on opposite side below the lesion
- upper motor neuron path
- cortex – internal capsule – brainstem
- what % of substantia nigra needs to be involved for motor problems
- 75%
- significance of separate motor and sensory roots for CN V
- can cut motor root without effecting sensory
- which cranial nerve roots used in speech
- 5, 7-12
- bells palsy symptoms
- no forehead lines, can’t close eye, no naso-labial folds, drooping mouth: LMN Lesion