neuro weeks 5-11

what is dysphagia?

feeding and swallowing difficulties

what are the phases of swallowing

1. oral preparatory phase (voluntary)

2. oral transport phase (voluntary)

3. pharyngeal phase (involuntary)

4. esophageal transport phase (involuntary)

what parts of the nervous system are involved in swallowing?

• cortical

  • primary motor and somatosensory

• subcortical

  • basal ganglia and limbic structures

• brain stem

• cranial nerces

what does the primary somatosensory system do for swallowing?

• receives information about the movement of the jaw joints, muscles (tongue and soft palate), lips, bolus size

what do the subcortical areas do for swallowing?

may play a role in modifying and monitoring swallowing activity

what does the brainstem do in swallowing?

• nucleus ambiguous

  • innervate the soft palate, pharynx, and larynx

• nucleus tractus solitarius

  • sensory neurons related to taste

what do the cranial nerves do for swallowing?

• trigeminal

  • motor: muscles of mastication

  • sensory: facial and mouth sensation

• facial

  • motor: muscles of lip closure

  • sensory: taste, saliva production

• glossopharyngeal

  • elevates the pharynx and larynx

  • taste in the posterior 1/3

• vagus

  • innervates the larynx, pharynx, and soft palate muscles

  • sensory feedback from the pharynx and larynx

• hypoglossal

  • muscles of tongue

what are the motor patterns in swallowing/chewing?

• voluntary

  • complex, purposeful actions

  • learnt with practice

• rhythmic

  • combines voluntary and reflexive

  • Onset and termination are voluntary

  • Once initiated, reflexive and repetitive

  • e.g. chewing (depending on the central pattern generator)

• reflex

  • involuntary, rapid

  • e.g. cough/gag

  • triggered by a stimulus

what is the swallowing central pattern generator

• located in the medulla and involves motor cranial nerves

• creates a swallowing pattern/reflex

what occurs in the gag reflex?

• stimulus from the glossopharyngeal nerve

• muscular response from the vagus nerve

• occurs in the pharyngeal stage of swallowing

what occurs in the oral preparatory stage of swallowing?

• lip closure using the facial nerve

• manipulation of the bolus via

  • lateral jaw movement (trigeminal)

  • lateral tongue movement (hypoglossal)

• elevation of tongue and soft palate resting against the tongue

what occurs in the oral transit stage of swallowing?

• oral cavity closed via tongue

• food is moved back through the mouth with squeezing action

• tongue forms a chute

• mouth floor raises

• tip of tongue reaches to palate

• central area hollows

• sides of the tongue elevate

what occurs in the pharyngeal stage of swallowing?

• closing of airway while bolus moves through pharynx

• requires sensory feedbakc to coordinate

what are the locations and functions of cortical speech production?

• pre-motor cortex

  • planning

• brocas area

  • planning

• supplementary motor area

  • programming movement sequences

  • feeds correct motor instructions in the correct sequence

• primary motor cortex

  • execution of speech

what are the functions of cranial nerves in speech?

• trigeminal: muscles of mastication

• facial: lip movement, articulation, and bilabial sounds

• glossopharyngeal: pharyngeal closure and abnormal nasal airflow

• vagus: elevation of soft palate during velopharyngeal closure

• hypoglossal: muscles of tongue and articulation of lingual sounds (f and k)

what are the types of dysarthria (difficulty speaking)?

• flaccid: LMN damage

• spastic: bilateral UMN damage

• dyspraxia/apraxia: impairment with planning or programming speech

what are the bases of speech?

• phonation: voice production

• resonance: air flow through oral or nasal cavities

• articulation: production of speech sounds

• prosody: features of speech

  • intonation

  • flow of speech

what does the the corticobulbar tract do for speech?

voluntary control of muscles for speech.

• arises from primary motor cortex

• passes through internal capsule

• synapses at the LMN in the CN nucleus in the brainstem

what are the grey matter structures of the basal ganglia?

• caudate (striatum)

• putamen (striatum)

• gobulus palidus

  • internus (GPi)

  • externus (GPe)

• subthalamic nucleus (STN)

• substantia nigra

  • pars compacta (SNpc)

  • pars reticular (SNPR)

what are the steps of the direct pathway?

1. thalamus releases excitatory glutamate to motor cortex to stimulate movement

2. globus pallidus internus and substantia nigra pars reticula send GABA to thalamus, inhibiting glutamate release

3. motor cortex sends information about movement through glutamate to the striatum

4. excited striatum releases inhibiting GABA into the GPI and SNPR, preventing GABA from being sent to the thalamus

5. thalamus is able to continue sending excitatory glutamate to motor cortex

6. movement is facilitated

7. substantia nigra pars compacta sends dopamine to the striatum, modulation the direct pathway

what are the steps of the indirect pathway?

1. GABA sent from globus pallidus externus to the subthalamic nucleus inhibits glutamate release from subthalamic nucleus

2. cerebral cortex sends excitatory information to striatum

3. striatum sends inhibitory signals to the globus pallidus externus, preventing GABA from being sent to the subthalamic nucleus

4. cerebral cortex sends excitatory signals to the subthalamic nucleus

5. subthalamic nucleus sends excitatory signals to the globus pallidus internus and substantia nigra pars reticula

6. GPE and SNPR send GABA to the thalamus

7. thalamus is inhibited, and can no longer send glutamate to the motor cortex

8. movement is inhibited

9. substantia nigra pars compacta sends dopamine to the striatum, modulating and inhibiting indirect pathway

what are the pathways used to send information from the thalamus to the cortex and from the substantia nigra pars compacta to the striatum?

• corticothalamic tract

• nigrostriatal tract

what are the basal ganglia loops?

• goal directed behaviour loop (non-motor)

• social behaviour loop (non-motor)

• emotion loop (non-motor)

  • reward direct

• motor loop (motor)

what does the basal ganglia do for movement control?

• regulates desired and inhibits undesired movements

  • voluntary movement, postural muscles, rhythmic movements

• sends information back to motor cortex via thalamus

• regulates muscle tone and force

how does the basal ganglia motor loop travel?

cortico-basal ganglia-thalamic loop

what are the pathways of the basal ganglia?

• hyperdirect pathway (irrelevant)

• direct: allows movement

• indirect: prevents undesired movement

what are the cortical layers of the cerebellum?

1. molecular: few axons

2. purkinje cells: single row of huge cells

3. granular layer: numerous packed neurons

what are the peduncles of the cerebellum and what do they do?

• Connect the rest of the CNS

• Superior cerebellar peduncle: in the midbrain, efferent fibres via thalamic nuclei to the cortex

• Middle cerebellar peduncle: in the pons, afferent fibres to the cerebellum from the cerebrum

• inferior cerebellar peduncle: in the medulla, afferent and efferent

  • afferent from the spinal cord, vestibular apparetus

  • efferent to vestibular nuclei and reticular formation

what supplys the cerebellum with blood?

• basilar artery giving rise to

  • anterior inferior cerebellar artery (AICA)

  • superior cerebellar artery (SCA)

  • posterior inferior cerebellar artery (PICA)

what does the cerebellum play a role in?

• maintaining posture and balance - through inputs from vestibular, makes postural adjustments

• coordination of voluntary movement - coordinates timing and force

• motor learning - fine tunes motor programs

• cognitive function

what are the cerebellum functional areas?

• spinocerebellum (vermis)

• vestibulocerebellum (floccolonodular)

• cerebrocerebellum (lateral hemispheres)

what does the spinocerebellum/vermis functional area do?

• input

  • movement commands from cortex

  • activity levels of spinal cord neurons

  • movement or postural adjustment from proprioceptors

• plays a role in making anticipatory, corrective, and responsive adjustments

what does the vestibulocerebellum/floccolondular area do?

• input

  • ipsilateral vestibular apparatus

  • ipsilateral vestibular nuclei in the brainstem

• output

  • vestibular nuclei and reaches motor neurons via vestibulospinal tracts

• role in head movement and position

what does the cerebrocerebellum/lateral hemisphere area do?

• input

  • cerebral cortex via pontine nucleus

• output

  • motor and premotor cortex via dentate and motor thalamus

• role in timing movements, planning movements, and coordination of voluntary movement (influences corticospinal, brainstem, and rubrospinal tracts)

what is cerebellar ataxia?

sudden inability to coordinate muscle movement due to disease or injury to the cerebellum

• can be genetic or non-genetic

• Purkinje and granule cells are vulnerable to alcohol damage

what is spinocerebellar ataxia type 1?

• autosomal dominant disease that causes loss of purkinje and granule cells

• occurs in 3rd-4th decade of life

what are the differences between cerebellar ataxia and sensory ataxia?

• cerebellar ataxia

  • caused by structural of functional change to cerebellum

  • results in ataxic movements

• sensory ataxia

  • caused by structural or functional change to the sensory nerves

  • results in interruption of sensory feedback

  • results in ataxic movements

what are the tests to distinguish sensory and cerebellar ataxia?

• rhombergs test: stand with feet together and balance for 30 secs. compare with eyes opened and closed

  • sensory: patients should be stable with eyes open and unstable with closed

  • cerebellar: unstable both open and closed

• finger nose test: patients index finger to their nose and then to examiners finger quickly and accurately

  • sensory: signs of ataxia when eyes closed

  • cerebellar: signs of ataxia both open and closed eyes

what are the types and location of dysmetria (inaccurate size of movement)?

• hypermetria: overshoots target

• hypometria: undershoots target

• damage to spinocerebellum

what is an intention tremor and where does it occur?

• involuntary, oscillatory movement

• spinocerebellum

what is dysdiadochokinesia and where does it occur?

• difficulty with rapid alternating movements (e.g. finger tapping)

• spinocerebellum

what is ocular dysmetria and where does it occur?

• eyes not able to be moved accurately to target

• vestibulocerebellum

what is nystagmus and where does it occur?

• involuntary oscillation of the eye

• vestibulocerebellum

what is movement decomposition and where does it occur?

• difficulty of movement in which gestures are broken into individual segments instead of being executed smoothly

• spinocerebellum

what is ataxic dysarthria and where does it occur?

• change in force, timing, range, and direction of movement of the articulators that gives a very slurred “drunk” sounding presentation

• cerebrocerebellum

what is ataxic gait and where does it occur?

• variability in walking pattern, increased risk of falls, slow speed

• spinocerebellum

I SKIPPED WEEK 8 UNTIL SMELL- GO OVER AGAIN PLS

what are the steps of olfaction?

1. air passes through the olfactory epithelium mucous

2. odour dissolves into mucous

3. odour reaches olfactory receptor cells

4. odour binds to surface of cilia

5. unmyelinated olfactory axons bundle together to create olfactory nerve

6. olfactory bundles penetrate the cribiform plate, travelling to the olfactory bulb

7. olfactory receptor neurons in the bulb synapse with second olfactory neuron

8. output neurons from bulb project to olfactory tract, projecting to range of areas

what are the disorders of smell called?

• anosmia: loss of smell

• hyposma: decreased sensitivity to smell

what are the structures associated with taste?

• receptor cells sit together, forming tastebud

  • chemical change in receptor cell pushes a neural impulse

• neural impuls cranial nerves

  • facial: transmits anterior 2/3 of tongue

  • glossopharyngeal: transmits posterior 1/3

  • vagus: transmits from epiglottis

• sensory information from cranial nerves is transmitted to solitary nucleus in the solitary tract of the brainstem

• second neuron in pathway transmits information to the thalamus

• final neuron synapse in the gustatory cortex

what is a loss of taste called?

ageusia

what makes up the fibrous/tunic layer of the eye?

• sclera: white part

  • provides attachment for extra-ocular muscles

• cornea: transparent structure

what makes up the vascular layer of the eye?

• choroid: capillary network of blood vessels

• ciliary body muscles: muscles, processes, and suspensory ligaments alter lens shape

• iris

  • pupillary dilator muscle (smooth muscle, sympathetic)

  • pupillary constrictor muscle (parasympathetic)

what makes up the inner layer of the eye?

• retina: houses photoreceptors

  • rods: low light, no colour

  • cones, high light, colour

• fovea

  • centre of macula

  • highest concentration of cones

  • site of sharpest vision

• macula: centre of your retina,

how does the retina work?

• pigmented epithelium that absorbs light that is passing through

• Photoreceptor cells synapse with bipolar cells

• bipolar cell synapses with ganglion cells, which then become the optic nerve, which leaves the retina

• blind spot occurs in the area where the retina meets the optic nerve (no light sensitive cells in this location)

what are the rectus muscles of the eye?

• superior: elevate cornea

• inferior: lower cornea

• medial rectus: adduct eye

• lateral rectus: abduct eye

what are the oblique muscles of the eye?

• superior oblique: elevation and abduction

• inferior oblique: depression and abduction

what is the process of the visual pathway?

1. optic tract travels from eye to lateral geniculate nuclei

2. lateral geniculate synapses with next neuron, which travels to the primary visual cortex (PVC looks for shape, size, texture)

3. information is subsequently sent to secondary visual cortex

4. information from left visual field is being projected to nasal side of left side, and temporal side of right side

5. at the optic chiasm, the information swaps to the other side of the brain

what are the types of blindness?

• lesion at optic nerve of right eye: no vision in right eye

• lesion at optic chiasm: vision impaired on lateral side of vision

• lesion behind optic chiasm: vision lost on contralateral side of body

• lesion far back, hasn’t cut the entire visual pathway: vision lost at contralateral bottom quarter of the body

what are the 3 bases of somatosensation?

• proprioception: information from musculoskeletal system

• exteroception: information from the skin (superficial or cutaneous)

• interoception: information from internal organs (stretch of bladder or stomach)

what are the types of receptors?

• nociceptors: pain

• thermoreceptors: temperature

• chemoreceptors: respond to water soluble and libid soluble substances dissolved in body fluids

• mechanoreceptors: sensitive to stimuli that distort their plasma membrane

what are the muscoloskeletal receptors?

• muscle spindles: within skeletal muscle belly

  • intrafusal fibres respond to muscle stretch

• golgi tendon organ: found in tendons in musculotendionous junction

  • detect force/muscle tension created during contraction

• joint receptosrs: respond to mechanical deformation of joint capsules and ligaments

what are receptive fields?

• cutaneous areas of skin that leads to activity in neuron

• large receptive fields cover a large area with low sensitivity

• small receptive fields cover a small area precisely

• small fields help the brain locate where a stimulus is felt with precision

what are the primary sensory neurons?

• neurons that take in somatosensory information from skin, muscles, joint capsules, and viscera

• PSN cell bodies are housed in the dorsal root ganglion (bipolar nerve)

what are the brodmanns area of the primary somatosensory cortex?

• area 3: nerve fibres carrying proprioceptive information

• areas 1 and 2: nerve fibres carrying information about texture, size, and shape

what is the brodmann’s area and function of the secondary somatosensory cortex?

• area 40

• recieves connections from the primary

• responds to stimuli bilaterally

  • less precision than primary

what are the brodmanns area of the somatosensory association cortex?

• areas 5 and 7

• receives synthesised connections from the primary and secondary cortices

• Neurons respond to several types of inputs

• involved in complex associations

  • stereogenesis and haptic perception

what are the types of ascending somatosensory tracts?

• conscious relay

• divergent relay

• non-conscious relay

what are conscious relay tracts and where are their neurons?

• transmit information about the location and type of stimuli with high fidelity

• 1st order neuron: cell body in dorsal root ganglion, travels into spinal cord/brainstem

• 2nd order: cell body in spinal cord/brainstem, axon decussates to the contralateral thalamus

• 3rd order: cell body in thalamus, axon travels up to primary sensory cortex (via internal capsule)

what are the neurons of the dorsal column medial lemniscus tract?

• 1st order: enters and ascends through dorsal column of spinal cord

• 2nd order:

  • cell bodies located in nucleus gracilis or cuneatus of spinal cord

  • axons decussate in spinal cord and ascend to thalamus

• 3rd order: cell bodies located in thalamus send their axons to the cortex via the internal capsule

• synapse to cells in the primary somatosensory cortex corresponding to the body area they originated from

what are the neurons of the spinothalamic tracts?

• 1st order: brings information into the posterior horn of the spinal cord

• 2nd order:

  • cell bodies in the posterior grey area of the spinal cord

  • axons of the secondary neurons cross at the midline and ascend from the spinal cord to the thalamus

• 3rd neuron: cell bodies in thalamus, project via thalamus to the primary somatosensory cortex (via internal capsule)

what are the nuclei of the brainstem responsible for intaking information from the trigeminal nerve?

• mesencephalic nucleus: unconscious proprioception from muscle spindles of the face

  • excessive biting, receives information about stretch from muscles of mastication

• main sensory nucleus: touch, vibration, 2 point discrimination, fine touch, conscious proprioception senses

• spinal nucleus: pain, temperature, and crude touch

what are the order of neurons that intake sensation from the face?

• 1st order: trigeminal ganglion

• 2nd order: transmit information to thalamus

• 3rd order: thalamus to cortical areas

what do divergent tracts transmit?

• slow aching pain

• information transmission is not localised, and is transmitted to many locations in the brainstem and cortex

what do unsconscious relat tracts transmit?

• spinocerebellar tract

• unconscious movement-related information in the cerebellum

  • proprioceptive and sensory

what occurs with complications of the dorsal column medial lemniscus and the spinothalamic tract?

• DCML: loss of proprioception and fine touch

  • hemisection of spinal cord: ipsilateral loss below level of lesion

  • somatosensory cortex lesion: contralateral sensory loss

• STT: loss of pain and temp sensation

  • hemi section: contralateral loss below level of lesion

  • somatosensory cortex: contralateral sensory loss

what is nociception?

the neural process of encoding noxious stimuli (neural)

what is noxious stimuli?

a stimulus that is damaging or threatens damage to normal tissue

what is pain?

perception of an aversive or unpleasant sensation arising from a specific region of the body (perception)

what are the physiological processes of nociception?

• transduction: conversion of noxious stimulus into an action potential in peripheral terminals of sensory fibres

• conduction: passage of action potentials from periphery along axons towards the CNS

• transmission: the synaptic transfer of input from one neuron to another

• perception: when the sensation is perceived by the brain

what are the tacts for the transmission of pain?

• spinothalamic: fast and slow pain, (A delta fibres)

• spinoreticular: slow, dull pain (C delta)

• reticular formation: responsible for emotion and behavuoural responses to pain

• trigeminal pathway: pain from face

  • spinal trigeminal pathway is for pain

  • cell body for first order neuron is in trigeminal ganglion

  • travels to medulla (decussation of 2nd order neuron)

what are the characteristis of A delta fibres?

• myelinated

• fast, sharp, localised pain

• lateral spinothalamic tract

what are the characteristics of C fibres?

• unmyelinated

• slow, dull, aching or burning

• poor localisation

• emotional and motivation aspects of pain

what are the classifications of pain?

• acute

  • up to 6 weeks

  • associated with tissue damage

• sub-acute

  • 4-12 weeks

  • secondary issues with tissue healing (inflammation, infection)

• chronic/persistent

  • continues past regular healing

  • 3-6 months

what are the types of pain?

• nociceptive: actual or threatened damage to non-neural tissue

  • e.g. post-op pain, injury

• neuropathic: abnormal neural activitiy secondary to disease, injury, or dysfunction of nervous system

  • related to lesion of neural tissue

  • e.g. compressed nerve, phantom limb pain, MS related pain

• nociplastic: pain arises from altered nociception despite no clear evidence of stimulus

  • no tissue damage or lesion on neural tissue

  • usually associated with chronic pain conditions such as fibromyalgia, low back pain, tension headaches

what is modulation of pain?

• alterations to pain signals that may amplify or dull them

• The same stimulus can elicit different responses in different scenarios

what is sensitisation?

• an increase in responsiveness of nociceptive neurons to their normal input, and/or recruitment of a response to normally sub-threshold stimuli

• can be peripheral or central

what are the types of pain sensitisation?

• allodynia: pain resulting from a stimulus that does not normally cause pain

• dysasthesia: unpleasant abnormal sensation, whether spontaneous or evoked

• Hyperalgesia: increased response to a stimulus that normally is painful

what are the analgesia systems?

• endogenous opioid system: excretion of natural, pain relieving chemicals

• descending inhibition: a message sent down the brain and spinal cord that blocks incoming pain messages

• gate control theory: non painful stimuli prevent pain messages in the spinal cord from reaching the brain

what is aphasia?

• impaired ability to understand or produce speech

• caused by damage to the cortical areas in the left hemisphere (broca’s and Wernicke’s)Broca’s

what is the flow of information during conversation?

1. primary auditory cortex - auditory discrimination

2. secondary auditory cortex - classification of sounds (language vs sounds)

3. wernickes area - auditory comprehension/word retrieval

4. subcortical connections - link wernickes and brocas area

5. brocas area - understanding syntax, instructions for language output

6. oral region of sensorimotor cortex - cortical output to speech muscles

what occurs during wernicke’s aphasia?

• loss of blood flow to superior temporal gyrus (MCA)

• impairment in receptive language

• fluent verbal output

• frequent word errors

• can use made up words

• impairment naming and repetition

what occurs during broca’s aphasia?

• loss of blood flow to broca’s and surrounding inferior frontal gyrus by left MCA

• limited verbal output

• good auditory comprehension

• repetition usually poor

• can co-occur with motor-speech disorders (e.g. dysarthria)

what occurs during conduction aphasia?

• legion to cortical region supramarginal gyrus and white matter pathways of arcuate fasciculus

• fluent speech with relatively intact receptive language

• poor repetition

• phonemic errors in spoken output

• naming difficulties

• awareness of errors

what occurs during global aphasia?

• extensive damage to frontal, temporal, and parietal regions

• severe receptive and expressive impairments

• almost totally absent speech

• may be able to express through facial expression, intonation, and gesture

what are the 3 domains that cause cognitive communication disorders?

• Memory: formation of records of new experiences and the use of the information to guide subsequent activities

• Attention: the concentration of awareness/focus on some phenomenon to the exclusion of other stimuli

• executive functionExecutive:

what is consciousness?

• having subjective experiences and awareness of self and environment

• can be influenced by meditation, medication, mental health conditions

what are the aspects of consciousness?

• arousal

• attention

• selection of object and attention

• motivation and initiation

what are the modulators associated with consciousness?

• serotonin: general arousal

• norepinephrine: attention

• acetylcholine: selection of the object of attention, based upon goals

• dopamine: motivation, motor activity, cognition

what is orienting attention?

• the ability to locate specific sensory information from among many stimuli

  • e.g. locating the traffic light whilst driving