Neurophysiology* Flashcards
Divisions of the nervous system?
CNS (brain and SC)
PNS - sensory and motor division (CN and SN)
Motor division is split into ANS (motor invol) and SNS (motor voluntary)
ANS split into para and sympathetic
Cell types of the neural cells of the brain and their function? (v basic)
Neurones - propagate impulse
Glial cells - supporting cell, aid with BBB and produce myelin
Anatomy, function and cell characteristics of a neurone - myelination and its function? Multiple sclerosis?
Dendrites
Nucleus
Axon
Cell body
Myelin sheath
Schwann cell
Node of ranvier
Axon terminals
Transmits impulses as AP
Cell characteristics:
- dendrites receive impulses and axons transmit them
- nuc loose chromatin
- high meta rate (mito)
Myelination:
- unmyelinated only have 1 layer of glial cell, appear grey (grey matter)
- myelinated have many layers of glial cells form MS, appear white (white matter)
- faster AP conduction, protection and prevent AP passing to adj cell bodies
MS:
- autoimmune against Schwann and oligodendrocytes
- muscle weakness, memory and problem solving issues
Organisation of neurons in the NS - CNS and PNS? upper and lower motor neurons relation to CNS and PNS?
CNS:
- cell bodies and unmyelinated axons form grey matter
- myelinated axons form white matter
PNS:
- myelinated axons form nerves
- cell bodies form ganglia
Upper:
- in CNS, leading from grey matter in brain synapsing with the grey matter of grey matter
Lower:
- in PNS, leading from grey matter in PC to voluntary muscle outside of the CNS
Development - neural tube - 3 layers? top layer develop? form of tube? function of neural crest cells?
Ectoderm, mesoderm and endoderm Top layer (surface ectoderm) develops a thickening called a neural plate Neural plate thickens and folds over to form the neural tube Neural crest cells migrate away and form other structures
Development - vesicle formation - neural tube division? 3 primary and 5 secondary names? 2nd –> brain structures? cerebral hemisphere further development?
Neural tube divides into 3 primary vesicles:
- forebrain, midbrain and hindbrain (4w)
and then into secondary vesicles:
- telencephalon and diencephalon (forebrain)
- mesencephalon (midbrain)
- metencephalon and myelencephalon (hindbrain) (5w)
Brain structures:
- telencephalon forms cerebral cortex and basal ganglia
- diencephalon forms thalamus and hypothalamus
- mesencephalon forms midbrain
- metencephalon forms the pons and cerebellum
- myelencephalon forms medulla
Cerebral hemisphere:
- from telencephalon
- C-shaped covering diencephalon and brainstem
Ventricles of the brain - relation to vesicles? location?
Ventricles of the brain:
- telencephalon = lateral ventricles
- diencephalon = 4rd ventricle
- mesencephalon = cerebral aqueduct
- rhombencephalon = 4th ventricle
Lateral ventricles are c-shaped and lie in the cerebral hemisphere
Interventricular foramen connects LV with 3rd ventricle
Cerebral aqueduct lies in midbrain
4th ventricle diamond shaped and in hindbrain
CT covering of the CNS - dura mater (function, location and extension?) arachnoid mater (location, function and extension?) and pia mater (location, function and extension?)
Dura mater: protection and outer
- septa between brain hemispheres and encloses intracranial venous sinuses
- extends to S2
Arachnoid mater: middle, cushioning
- not follow convolutions of brain
- extends to S2
Pia mater: innermost and impermeable to fluid
- follows convolutions
- form choroid plexus form CSF
- extends to coccyx as fibrous strand (filum terminale)
Extradural space - definition? bleeding? Subdural space - definition? bleeding? Subarachnoid space - definition?
Extradural:
- def: space between dura and skull
- bleeding: involving middle meningeal artery (ECA), called and extradural haematoma
Subdural:
- between dura and arachnoid
- bleeding from haemorrhage of veins draining brain
- haematoma is sickle
shaped
Subarachnoid:
- between arachnoid and pia
- filled with CSF
- all BV supplying brain and CN pass through
- haemorrhage can be spont due to aneurysm or trauma (vertebral and ICA branches (cirlce of WIllis)
Protection of brain dural folds - structures?
falx cerebri
tentorium cerebelli
falx cerebelli
diaphragma sellae
CSF - colour? specific gravity? pH group? cells? normal Pa? increased Pa? circulation passage (synth by? passage between via foramen?) arachnoid granulation function/
Clear and transparent fluid
1.004-1.007 SP
Alkaline and doesn’t coagulate
No cells
60-150 mm Pa
Increased Pa when standing coughing, sneezing, crying and compressing IJV
Circulation:
- synth by the choroid plexus in the lateral ventricle
- from lateral ventricle to 3rd ventricle via interventricular foramen
- from 3rd ventricle to 4th ventricle via cerebral aqueduct
- from 4th ventricle to the subarachnoid space around brain and SC via foramen of magendie and foramen of luschka
Arachnoid granulation:
- allows passage of CSF into the venous system from the subarachnoid space
Blood brain barrier - definition? content? function?
Definition: circumventricular organ - protective mechanism that helps maintain a stable environment for the brain and prevents harmful aas and ions present in the bloodstream and blood cells from entering the brain Content: - endothelium with tight junctions - thick basal lamina - foot processes of astrocytes Function: - drug delivery to CNS, but need to be lipid sol or vector
Cerebrum - size? located? 2 parts? sulci definition? gyri definition?
Size:
- largest part of the brain
Located:
- in the anterior and middle cranial fossae and the whole concavity of the vault of the skill
2 parts:
- cerebral hemispheres (left and right)
- diencephalon (consists of thalamus and hypothalamus)
Gyri:
- increases Sa of the brain the cerebral hemispheres are thrown into folds
Sulci:
- gyri separated from each other by fissures
Grey matter and white matter - brain and SC? 5 types of cells in the grey matter of the cerebral cortex? 6 different cortical layers?
Brain: - inside white (nerve fibres) - outside grey (nerve cells) SC: - inside grey (nerve cells) - outside white (nerve fibres) 5 cells: - horizontal - stellate - fusiform - cells of Martinolli - pyramidal 6 layers: - molecular layer - external granular layer - external pyramidal layer - internal granular layer - internal pyramidal layer - multiform layer
White matter - composition? supported by? Commissural fibres - function? examples? Association fibres - function? short/long fibre location and function? Projection fibres - function? examples?
Composition:
- myelinated nerve fibres
Supported by:
- neuroglia
Commissural fibres:
- connects corresponding regions of 2 hemispheres
- corpus callosum (rostrum, genu, body and splenium) and fornix
Association fibres:
- connects various cortical regions within same hemisphere
- short fibres located beneath cortex and connects adjacent gyri
- long fibres arranged into named bundles (fasciculi)
Projection fibres:
- afferent and efferent nerve fibres passing to and from the brainstem to the cerebral cortex
- internal capsule, corona radiata and optic radiation
Thalamus - contains nucs? grey matter? receives tracts? function? 3 parts? split by?
Nuclei: - anterior, medial and lateral Grey matter: - large ovoid mass Tracts: - receives main sensory tracts (except olfactory pathway) Function: - integrates information it receives and relays to the cerebral cortex and subcortical regions - integrates visceral and somatic function Part: - anterior nuclear group - medial nuclear group - lateral nuclear group Split by: - internal medullary lamina
Hypothalamus - location? function? homeostatic roles? important nuclei? nuclei run into? hypothalamo-hypophyseal portal system function?
Location:
- part of the diencephalon that extends from the optic chiasma to the post border of the mammillary bodies
- lies below thalamus and separated by the hypo sulcus
Function:
- main visceral control centre and homeostasis
Homeostasis:
- autonomic control
- body temp reg
- reg food intake
- reg water and thirst
- reg sleep cycle
- control endocrine
Important nuclei:
- supraoptic
- paraventricular
Run:
- axons running down into post lobe of the pituitary
Hypothalamo-hypophyseal portal system:
- carry neurosecretions into the anterior lobe of pituitary gland
Pituitary gland - anatomy? part development?
Anatomy:
- stalk
- anterior part
- posterior part
Development:
- pituitary stalk and post pituitary derived from diencephalon
- anterior pituitary from ectodermal (Rathke’s pouch)
Pineal gland - located? age changes? function? indirect function?
Located:
- projects backwards to lie post to midbrain
Age changes:
- progressive calcification
Function:
- produces melatonin for circadian rhythm influenced by light
Indirect function:
- controls function of other endocrine organs
Basal ganglia - function? pathology?
Function:
- help reg initiation and termination of movements
- role in controlling motor system referred to as extrapyramidal system
Pathology:
- Parkinson’s and Huntington’s
Limbic system - located? function? components?
Located: - surrounds corpus callosum and the diencephalon Function: - behavior, emotion and memory Components: - cingulate and subcallosal gyrus - septal area and olfactory bulb - hippocampal formation (hippo gyrus, dentate gyrus and parahippo gyrus) - amygdaloid body and mammillary body - anterior nuc of thal - hypothal
Spinal tracts - lateral pathways (function, higher centre control and examples?) ventromedial pathways (function, higher centre control and examples?)
Lateral pathways:
- control voluntary movements of distal muscles (under direct cortical control)
- corticospinal and rubrospinal tracts
Ventromedial pathways:
- control posture and locomotion (under brainstem control)
Lateral pathway - 2 tracts? area 4/6? the rest are? SC junction what occurs? brain relation with body? synapse of CST axon? RST starts where? loss of function with lesions in CST and RST or CST alone? CST control of spinal motor nerves?
Tracts:
- corticospinal and rubrospinal
Area 4/6:
- frontal motor cortex and the rest are somatosensory
Junction:
- CST crosses over at SC
Relation:
- right motor cortex response for left side and vice versa
Synapse:
- on ventral horn motor and interneurons to control muscles
RST:
- starts in red nic of midbrain
Lesions:
- CST and RST; loss of fine movement of arms and hands also can’t move shoulders, elbows, wrists and fingers independently
- CST alone; same as above but functions re-appear as RST takes over
Control:
- pyramidal neurons in motor cortex
- monosynaptically excite pools of agonist spinal motoneurons
- same pyramidal branch and via interneurons inhibit them
Ventromedial pathways - function with example? pontine and medullary reticulospinal tracts (origin? function? innervates?) use of lateral and ventromedial to cause one action?
Function:
- stabilise head and neck (VST)
- eye stability as body moves (TST)
Tracts:
- origin from brainstem
- use sense about balance, body pos and vision
- reflexly maintain balance and body position
- innervates trunk and antigrav muscles in limbs
Action:
- motor cortex can signal via both lateral and ventromedial to form a response
Human cortex - area 4 role and function? area 6 role, function and split into with their functions? area 5 and 7 function and inputs? prefrontal and parietal cortex role and relation to area 6?
Area 4:
- innervate specific contralateral muscles
- primary motor cortex
Area 6:
- drive complex movements on either side of body
- premotor area (PMA) and supplementary motor area (SMA)
- SMA innervates distal motor units
- PMA innervate proximal motor units via reticulospinal
Area 5/7: post parietal cortex
- form mental image of body in space formed from somatosen, proprio and visual inputs
P and P:
- decisions are taken about what actions to take
- axons converge to area 6 and encode the actions which is converted to how it’ll be carried out
- axons from area 6 go to area 4 for the action to be performed
Basal ganglia - motor loop definition? input to area 6? anatomy? motor loop process and end product? Primary motor cortex - initiation of vol move (neurones? inputs? encode? precision encoded by?
Loop:
- information loop cycles from cortex through thalamus basal ganglia back to SMA
Area 6:
- input comes from ventral lateral nuc in dorsal thalamus called the VLo (from the basal ganglia)
Anatomy:
- putamen
- substantia nigra
- subthalamus
- globus pallidus
- VLo
- SMA
Process:
- cortex to putamen (excite)
- putamen to globus (inhib)
- globus to VLo (inhib)
- VLo to SMA (excite)
- positive feedback loop (‘Go’ signal for voluntary movement)
PMC:
- by pyramidal neurons
- inputs from thalamus
- burst of activity before and after to encode force and direction
- precision encoded by population of neurons
- larger population input creates finer control
Cerebellum - lesions cause? layer, area 4/6 and somatosense cortex form? connections across the brain? function? Lateral cerebellum (motor loop addition?)
Lesions:
- ataxia
Form:
- corticopontocerebellar projection
Connections:
- connect cortex, pontine nuc and cerebellum
- back to cortex via ventrolateral thalamus
Function:
- instruct direction, timing and force of movements
Lateral:
- move through basal ganglia and VLo via involve of feedback loop via pons, cerebellum, thalamus back to cortex
Cell bodies of cranial nerves - sensory? motor? autonomic?
Sensory - dorsal root ganglion Motor: - in CNS Autonomic - pre (in CNS) and post (in ganglion) ganglion
CN I - function? pathway of the nerve? Fractured cribriform?
Function: - smell Pathway: - recep in olfactory epith of nasal cavity, olfactory nerve passes through the cribriform plate of ethmoud and enter olfactory bulb in ant cranial fossa Fractured: - loss of smell tearing nerve
CN II - function? pathway of nerve? Increased CSF Pa? Damage to the R optic nerve, optic chasm and optic tract?
Function: - vision Pathway: - enters optic canal, nerves join forming optic chains, fibres cross to form the optic tract Increased: - causes papilloedema R optic nerve: - blindness of R eye Optic chaisma: - loss of peripheral vision (bitemporal hemianopsia) Optic tract: - causes blindness in left temp and right nasal fields (left homonymous hemianopsia)
CN III - function (somatic - muscles? autonomic?) pathway of nerve? drooping? pupil problems? eyeball movement?
Functions: - somatic via extraocular muscles (sup, medial, inf erectus and inf oblique) and eyelid (levator palpebrae superioris) - autonomic motor - parasymph to pupil causing constriction to ciliary muscles Pathway: - merges from midbrain and exits via SOF Drooping: - ptosis Eyeball movement: - abducted and pointing down - no pupillary reflex - no accomodation of lens
CN IV - function (somatic - muscles?) pathway of the nerve? diplopia?
Function:
- somatic motor of extraocular (superior oblique moves eye down)
Pathway:
- emerges form the dorsal surface of mid brain and exits via SOF
Diplopia: when looking down
- double vision
CN VI - functions (somatic - muscle)? pathway of nerve? diplopia?
Function:
- somatic extraocular; lateral erectus abducts eye)
Pathway:
- emerges between pins and medullary exits via SOF
Diplopia: medial deviation
- double vision
CN V - ophthalmic - pathway? innervated?
Pathway:
- emerges from the pins, travels via the trigeminal ganglion and exits via SOF
Innervates:
- cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavities and sinuses
CN V - maxillary - pathway? Innervates?
Pathway:
- emerges from the pins, travels via the trigeminal ganglion and exits via the foramen rotundum
Innervation:
- face over maxilla, maxillafybteeth, TMJ, mucosa of nose, maxillary sinuses and palate
CN V - mandibular - pathway? Innervates (sensory and motor?) damage can cause?
Pathway:
- emerges from the pond, travels via the trigeminal ganglion and exits via the foramen ovale
Innervates:
- sensory; face over mandible, mandibular teeth, TMJ, mucosa kd mouth and ant 2/3 of tongue
- motor; mastication, tensor veli palatini and tensor tympani
Damage:
- paralysis of masticatory muscles
- loss of corneal or sneezing refelx
- loss sensation to face
- trigeminal neuralgia
CM VII - functions (somatic motor? autonomic motor? special sensory? general sensory?) pathway of the nerve? Bell’s palsy?
Fucntions:
- somatic; muscles of facial expression, scalp, stapedius
- autonomic; submand and sublingual glands, lacrimal, nose and palate glands
- special; taste from ant 2/3 of tongue and soft palate
- general; EAM
Bell’s palsy:
- can’t frown, clear eyelids or bare teeth
Pathway:
- emerges from between pons and medulla and exits via IAM, dividing into vestibule and cochlear nerves
CN VIII - innervation (special and general sensory?) nerve pathway? Ringing in ear? Deafness? Loss of balance? Nystagmus?
Innervation:
- special; vestibular sensation from semicircular ducts, cuticle, saccule fibes sense of position and movement
- general; hearing from spinal organ
Pathway:
- emerges from between pons and medulla and exits via IAM, dividing into vestibule and cochlear nerves
Ringing: tinnitus
Deafness: conductive or sensorineural
Loss of balance: vertigo
Nystagmus: involuntary rapid eye movements
CN IX - innervations (special? general? visceral? autonomic motor? somatic motor?) pathway of nerve? loss of gag and taste from back of tongue?
Innervations:
- special; taste from post 3rd of tongue
- general; sensations from middle ear and post oral cavity
- visceral; sensation from carotid body and sinus (Pa)
- autonomic; parasymph of parotid
- somatic; to stylopharyngeus helps with swallowing
Pathway:
- emerges from medulla and exits via jugular foramen
Loss of:
- assoc with injuries to X and IX (jugular foramen syndrome
CN X - innervates (special? general? visceral? autonomic motor? somatic motor?) pathway nerve? Damage to pharyngeal branch or laryngeal branch?
Innervations:
- special; taste from epiglottis and palate
- general; sensation from auricle and EAM
- visceral; pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach and intestine
- autonomic motor; para innervation of muscles in bronchi, gut and heart
- somatic; pharynx, larynx, palate and oesophagus
Pathway:
- emerges from medulla and exits via jugular foramen
Pharyngeal:
- difficult in swallowing
Laryngeal:
- difficult in speaking
CN XI - innervates (somatic - muscles?) Loss of function? pathway of nerve?
Innervates:
- somatic motor; striated muscle of soft palate, pharynx and larynx also SCM and trapezius
Pathway:
- medulla and large spinal roots exit via jugular foramen
Loss of function:
- weakness in head turning and shrugging shoulder
CN XII - innervates (somatic motor - muscle?) pathway? tongue paralysis?
Innervates:
- somatic motor to muscles of tongue
Pathway:
- from the medulla and exits via the hypoglossal canal
Tongue:
- atrophy of ipsilateral half of tongue, tip deviates towards affected side
Different types of stimuli causing different types of pain?
Tissue damage - nociceptive pain
Inflammatory pain - inflammatory mediators
Nerve injury - neuropathic pain
Dysfunctional pain has an unknown stimuli (lower back pain)
Pain pathway via dorsal root ganglia (stim? AP? DRG? Ascending tracts? Higher brain centres?)
Stimulus detected by sensory nerve endings and AP is propagated
Passes to the dorsal root ganglion and passes into the SC via synaptic transmission
Processing and plasticity in the spinal dorsal horn
Trvalss up the SC vis the spinothalamic and spinoparacbtachial tract into the limbic, thalamus and cortex
Primary afferent fibres - Adelta? C fibres?
Diameter? Myelination? Conduction speed? Act threshold? Sensation on stim?
Adelta: thermal and mechanical pain - small - thin - 5-15ms - high and low - rapid sharp and localised pain - initial pain C fibres: mechanical, thermal and chemical - smallest - unmyelinated - <2ms - high - low, diffuse and dull pain - delayed pain
Peptide production from the pain fibres? (What are they?
From NGF - adelta produce CGRP and sub P
From GDNF - c fibres non-peptergic
Enter different pain of the brain
Trigeminal ganglia ascending pathway? (TRG? Passage to the brain? Nuc?)
Starts at the trigeminal ganglion entering the pons
Drops into the medulla where the spinal nucleus of V is present
Rises through the pons and medulla to the ventroposteromedial nuc of trigeminal to the primary sensory area
Allodynia and hyperalgesia definitions?
Allodynia:
- increased response to normally non-painful stimuli
Hyperalgesia:
- exaggerated response to normally painful stimuli
Mechanisms of pain signalling - peripheral and central sensitisation?
Peripheral in the skin and muscles
Central is in the dorsal horn
Cell signalling in peripheral sensitisation - upregualting of existing receptors? Upregulati f I’d new receptors?
Receptors: in response to stimuli - ligands-gated chs - GPCR (PGE2 and bradykinin) - tyrosine kinase receptor New receptors: - volt-gated chs And so the area becomes super-excitable due to upregulatuon (Receptor and channel sensitisation with gene expression)
Cell signalling in the central sensitisation - definition? 2 phases? New receptor expression?
Def:
- increase in the excitabiltuy of neurons within the central nervous system so that normal inputs begin to produce abnormal responses
2 phases:
- immediate but relatively transient phase
- slower onset but longer-lasting phase
Expression:
- presynaptic release of glutamate, sub P and CGRP
- greater receptor expression such as NMDA
- lower threshold and opening chs therefore increasing excitabiltiy
Referred pain from the teeth - pain source? Vice versa? Mechanism of pain?
Source:
- pain can originate from the maxillary sinus due to their close proximity
Vice:
- previous treatment can also cause maxillary sinus pain
Mexh:
- nerve damage or long-term sensitisation
Gate control theory of pain - inhibition? C fibres? Abeta fibres?
C fibres activated synapsing and sending pain stimuli to the brain
Abeta can also be stimulated such as rubbing which activates the inhibitory internecine which inhibits the C fibres post synaptic connection and so inhibiting the pain stimuli to the brain
Inhibition of pain stimulation - gate theory example? Rubbing?
Rubbing activates Abeta which activates inhibitory interventions that inhibit 2nd order dorsal horn neurons inhibiting pain signalling
Descending inhibition pathway for pain modulation - evidence found? Mechanism of action?
Electrim stim of periaqueductal grey reduces pain severity
Morphine produces the same reaction
Naloxone administration inhibits both 1 and 2
Mechanism:
- morphine binds to opioid receptors
- release of endorphins/enkephalins
- naloxone blocks opioid receptors
Descending pain regulatory pathway - pain stimuli? PAG? Opiate blocking?
Pain:
- causes pain from sensory 1st order neurons
- passes into dorsal horn and synapses to another neurons to the thalamus
PAG
- stimulated to activate an opiate interneurone which inhibits the signalling of the 1st order sensory neurons
Opiate:
- block NuT reelase from 1st order afferent pre-synapic
- inhibit 2and order afferent post synaptic
Higher brain centre regulation of PAG - centres example?
Centre: emotion/stress/arousal - cortex - hypothalamus - thalamus Can either activate or inhibit PAG
Common analgesic targets - NSAIDs pathway (examples? Mechanism of action?) Low effectivity?
Examples - aspirin - paracetamol - ibuprofen Mechanism: - action to inhibit COX to stop the conversion of arachidonic acid to prostaglandins Low: - due to bradykinin which increases the synthesis of prostaglandins
Defintion of proprioception? Types of proprioceptors? Trigeminal proprioceptor types?
Defintion: - awareness of position of body parts in relation to each other and surroundings Type: - muscle spindles - golgi tendon organs - joint receptors Trigeminal: - muscles of mastication (spindles) - PDLMs - TMJ receptor
Structure of muscle (fibre types, supplies by and constituents?)
Extrafusal: - bulk of fibre and contractile - supplies by a-motor neurons Intrafusal: - spindle, specialised within a CT capsule
Function of muscle spindles? Example (glass filling with drink?
Information about muscle length Act to maintain muscle length Load compensation Example: - glass filling - bicep spindle stretch - increased motor neuron drive to bicep - muscle length maintained
Masticatory muscle spindle - cell body location? Afferent synapse location?
Cell body: - trigeninal mesencephalic nuc Afferent: - V motor nic - cerebellum and cerebral cortex
Gamma motor neurons - functions?
Cause contraction of intrafusal
Maintain tension in spindle and afferent activity
Alpha and gamma co-activation
Golgi tendon organs - found? Function?
Found:
- in tendons in series with muscle fibres
- role in inhibitory reflex prevention of CS stretch of muscles
Types of joint receptors - location and function?
Pacinian - ligaments- acceleration
Golgi - ligament- position
Ruffini - capsule - movement
Anatomy of muscle spindle - head, centre and tail (innervation, function and stimuli)?
End portions are contractile
- head innervated by afferent II (activated by stretch, detects fibre length)
- tail innervated by gamma efferent
- middle is the non-contractile central portion which can be stretched and is innervates by Ia (afferent - detects length of fibre and speed of change)
Description of a reflex arc - reflex latency (conduction time)?
Receptor to afferent neurons Synapses in SC To an efferent neurons and effector Latency: - time relayed to speed and distance - delay at synapse (0.2ms)
Jaw reflexes - vertical and horizontal (direction and movement?)
Vertical:
- move mandible relative to maxilla in vertical plane
- jaw jerk (opening and unloading)
Horizontal:
- move mandible relative to maxilla in protrusive, recursive or lateral direction
Jaw jerk reflex - Type of reflex? Stimulus? Response? Monosynaptic? (Clinical stimulus? Receptor? Synapse? Effect? Latency?) Role of jaw-jerk (phasic and tonic?)
Reflex: - phasic stretch Stimuli: - sudden jaw opening Response: - activation of jaw closing muscle Monosynaptic: - jaw closing muscle spindles - jaw closing motorneurones Clinical stimulus: - chin tap Receptor: - muscle spindle Synapse: - 1 in V motor nuc Effect: - contraction of masseter muscle Latency: - 8ms Role: - phasic: load compensation during chewing and stabilise jaw during vigour head movement - tonic: resist gravity and maintain posture
Jaw jerk - postural position (resting position? Maintained? edentulous? Reference for?)
Resting with teeth apart
Maintained:
- minimal muscle activity or governed by muscle elasticity
Remains reproducible throughout life in dentate and edentulous subjects
Important reference for position and height for dentures
Mech of mandibular posture - clinical relevance?
Active - stretch reflex Passive - tissue elasticity Relevance: - altered jaw relationships - vertical jaw relationship
Inhibitory jaw reflex - stimuli? Responses? Pathways (trisynaptic or polysynaptic? - neurons type? And receptors?)
Stimuli: - mech or noxious stimuli in mouth - noxious around mouth or elsewhere in body Responses: - act of jaw opening (sub-primates only) - inact of jaw closing Pathway: - trisynaptic or polysnaptic - mechanoreceptive or nociceptors - interneurones - jaw closing and opening motorneurones
Inhibitory jaw reflex pathway?
Nociceptors and mechanoreceptors recieve stimulus
Passes to trigeminal ganglion
Both interaction with supratrigeninal nuc
Reticular formation
Act inhibitory on V motor nic
Causing muscle
Function of inhibitory jaw reflexes?
Protective:
- restrain buildup of forces between teeth during mastication
- prevent overloading of periodontium, muscle and TMJ
Facilitate jaw opening to expel noxious material and minimise damage to lips
Jaw unloading reflex - stimulus? Response? Pathway neurons?
Stimulus: - sudden jaw closure following hard biting Response: - inact of jaw closing muscles - activation of jaw opening muscles Pathway: - jaw closing muscle spindles - interneurons - jaw muscle motor neurons
Jaw unloading reflex - pathway? during loading? Loading removed? Function?
Pathway:
- jaw closing muscle activates and synapses with V mesencepahlic nuc act V motor nuc
- activates jaw opening muscles
During laoding:
- jaw opening muscle is not stimulated
Loading removed:
- jaw closing muscle doesn’t stimulate the reflex
Fucntion:
- protection of antagonist teeth against each other
Horizontal jaw reflexes - response to? Role for?
Reflex horizontal movements of jaws in response to mechanical stimuli
Roles in canine guidance
Trigeminal system - pain? innervation it provides? branches?
Pain:
- common reason for people to seek dental treatment
- prevents people from obtaining optimal dental care
- big impact on life
Innervation:
- sensory innervation to the face and mucous mem
- motor innervation to muscles of mastication
Branches:
- ophthalmic, maxillary and mandibular
General sensory pathway - neurone pathway?
Primary afferent neurons to 1st synapse
1st synapse to thalamus then to the cerebral cortex
Studying the CNS - tracer? electrophysiological? neurological?
Tracer: - HRP and fluorescent dyes Electrophysiological: - exciting the nuc from peripheral stimuli Neurological: - happens if nuc destroyed by disease
Trigeminal sensory pathway - neurons pathway?
Trigeminal primary afferent neurons synapses with the trigeminal sensory nuc (trigeminal ganglion present)
From the nuc to the thalamus via the trigeminothalamic tract (synapses with the thalamus)
Thalamus to the somatosensory cortex
Main sensory nucleus (found? primary afferents? second order neurons? function?)
Found:
- brainstem
Primary afferents:
- V1, V2 and V3 (large myelinated afferents)
Second order neurons:
- cross the midline to join VTTT and terminate in VPM of thalamus
- don’t corss midline and joint DTTT and terminate in VPM of thalamus
Function:
- processing discriminative tactile and proprioceptive sensation
Discriminative touch pathway from the head - first/second and third order?
First: - axons from face in trigeminal ganglion Second: - pontine trigeminal nuc Trigeminal lemniscus Third: - ventral post thalamic nuc Neuron reaches the sensory cortex
V spinal trigeminal nucleus - subdivisions? extension?
Subdivisions: - V nuc oralis - V nuc interpolaris - V nuc caudalis Extension: - both nuc and tract extend caudally to about the third cervical segment of the SC
V nucleus caudalis - located? primary afferent? second order neurons? function?
Located:
- most caudal part, extending from SC to obex
Primary afferent:
- small, turn caudally and join spinal trigeminal tract (V1, V2 and V3)
Second order neurons:
- cross midline to joint TTT and terminate in VPM of thalamus
Function:
- processing pain and temp from the face, mouth and nose
Convergence, divergence and straight through?
For knowledge
Pain and temperature from the head - pathway neurons (first, second and third order?)
First: - axon from face in the trigeminal ganglion to the second Second: - within the spinal trigeminal nuc Spinal lemniscus Third: - in ventral post thalamic nuc Leading to the sensory cortex
V nucleus Oralis and Interpolaris - primary afferents? second order neurons? functions?
Primary afferent:
- small, turn caudally and join STT (V1, V2 and V3)
Second order neurons:
- some to contralateral VPM and some to cerebellum
Functions:
- tactical information
- pain and temp from the teeth and intraoral structures
- reflexes (corneal)
Arrangement of afferents and their endings in spinal trigeminal system - (rostral-caudal) ophthalmic? mandibular? maxillary? (for different divisions) pain-temp sensation?
Ophthalmic: - spinal tract fibres most ventral Mandibular: - spinal tract fibres most dorsal Maxillary: - spinal tract fibres in between Pain-temp: - area near centre of face more rostral - area towards the back of head more caudal
Trigeminal mesencephalic nuc - located? cell bodies found? primary afferents? synapse? second order neurons? function?
Located: - most rostral part Cell bodies: - jaw muscle spindles afferents - some mechanoreceptive afferents from PDL Primary afferents: - cell bodies within CNS - parent axon in V motor root (V3) Synapse: - in V motor nuc Second order neurons: - V motor neurons Function: - reflexes - nonconscious proprioception
Functions of trigeminal sensory nuclei - main sensory nuc? nucleus oralis? nucleus interpolaris? nucleus caudalis?
Main sensory: - sensation of touch - conscious proprioceptive sensation - reflexes Nuc oralis: - tactile touch - sensation of pain - reflexes Nuc interpolaris: - reflexes Nuc caudalis: - sensations of hot, cold and pain
Trigeminal motor nucleus - located? inputs from? afferent? damage to nuc?
Located: - medial to MSN in pons Inputs: - Vms - motor cortex - hypothalamus Afferents: - exit via mtor root to mandibular division - supply muscles of mastication Damage: - ipsilateral muscle atrophy
Mechanism of ingestion - different stages?
Transport: - food from lips to cheek teeth Mastication Transport: - food from cheek teeth to back of tongue Swallowing
Functions of mastication - Related to health?
Functions:
- breakdown food
- stim salivary flow
- contribute to taste and smell by releasing chemicals
- growth and maintenance of oro-facial tissues
Health:
- poor dentition = poor mastication
- poor mastication can lead to gut disorders
- poor diet = poor dentition
The chewing cycle - time? phases? 1 full cycle? during open? during closing?
Time:
- 0.5-1.2 sec
Phases:
- opening
- closing (fast - crushing) (slow - grinding)
- intercuspal (tooth to tooth)
Full cycle:
- opening + closing + power stroke
During opening:
- working side head: rotates and moves slightly (Bennett Movement)
- balancing side head: moves downwards, forwards and medially
During closing:
- working side head: moves medially (back to normal position in glenoid fossa), rotates back to normal orientation
- balancing side head: moves upwards, backwards and laterally (back to normal position in glenoid fossa)
Lateral jaw movements - working side and balancing side?
Working side: functional - to which mandible moves - where food is located Balancing side: non-functional - from which mandible moves
Chewing cycle - food consistency? quality and quantity of tooth contact? present or absent of pain? sequence of muscle activation (opening and closing?)
Food consistency:
- tough or brittle
Quality and quantity of tooth contact:
- tall cusps and deep fossae (vertical chewing stroke)
- flattened or worn teeth (broader chewing stroke)
Presence or absence of pain:
- TMJ pain (shorter, slower and irregular pathway)
Sequence:
- opening; mylohyoid, digastric and lateral pterygoid
- closing; lateral pterygoid, temporalis, masseter and medial pterygoid
Masticatory performance - definition?
Definition:
- the ability to breakdown food morsels into small particles
- number of chewing strokes required to prepare a mouthful for swallowing
- correlated with total occlusal contact area
Control of mastication - voluntary? reflex and cyclical?
Voluntary: - result of deliberate effort of will Reflex: - given sensory input evokes a stereotypes motor response Cyclical: - N/A
Central pattern generator theory of mastication - brain centres and responses?
Peripheral influences act jaw and tongue reflexes that act masticatory muscle motor neurons which activate mastication
Peripheral influences can also act the central neural pattern generator of the brainstem or high centres that act mastication downstream
