Neuro

Question 1

3 major proprioceptive receptors

Answer 1

Muscle spindles - changes in muscle length
Golgi tendon organs - changes in muscle tension
Ruffini corpuscles - present in joint capsule and provide info on JPS

Question 2

Location and function of FG and FC

Answer 2

Fasiculus Gracilis is more medial and has information concerning fine touch of the ipsilateral lower limb. FC is more later and have fine touch ipsilateral upper limb

Question 3

Anteriolateral modalities and pathway

Answer 3

Nociception, temperature and crude touch.

1st enter via DRG and synapse with neurons in the dorsal horn known as substantia gelatenosa. However, some can ascended or descend via Lissauer’s tract and then synapse.
2nd decussate via ventral white commissure and then ascend via spinothalamic fasciculus and synapse with cell bodies in VPL of thalamus
3rd to post central gyrus.

Remember that new fibres join the anteromedial tract at its anteromedial edge, therefore fibres from sacral region are lateral to fibres from cervical, this is to add during decussation.

Question 4

Dorsal column modalities and pathway

Answer 4

Discrete touch, pressure, conscious proprioception and vibration.

1st enter via DRG and depending on the level they entered on will ascend via FC or FG. Below T6 (LL) will ascend via FG and above via FC. They ascend to caudal medulla to synapse with cell bodies in either cuneate or gracile nuclei.
2nd then decussate (referred to as internal arcuate fibres) and then ascend to VPL of thalamus (during which referred to as medial lemniscus.
3rd to post central gyrus

Question 5

Names of the three spinocerebellar tracts and basic function

Answer 5

Anterior - Compares incoming proprioception with descending input to lower motor neurons for LL
Posterior - trunk and ipsilateral LL (C8 and below)
Cuneocerebellar - fibres from C7 and above

Question 6

Anterior spinocerebllar pathway

Answer 6

Decussates twice making it ipsilateral
1st enter via DRG and synapse with 2nd in lateral aspect of ventral horn.
2nd then decussate and ascends as the anterior spinocerebellar. Decussates again after reaching superior cerebellar peduncle.

Question 7

Posterior spinocerebllar pathway

Answer 7

1st enter via DRG and synapse with second in Clarks nucleus, however if fibres enter below L2 the ascending in FG until reaching L2 and Clark’s nucleus
2nd then ascend via ipsilateral lateral funiculus and travel through the inferior cerebellar peduncle

Question 8

Cuneocerebellar tract

Answer 8

1st enter via DRG and ascend FC to synapse in cuneate nucleus in medullar
2nd go to inferior cerebellar peduncle to cerebellum

Question 9

What is the corneal blink reflex

Answer 9

Protective reflex to remove foreign particles and lubricate the eye.

• Ophthalmic division of trigeminal CN 5 detects
• Synapses in the spinal trigeminal (nociception) and chef sensory nuclei (pain)
• Interneurons synapse bilateral (meaning bot eyes blink) with facial nucleus motor neurons
• Facial nerve CN7 innervates orbicularis oculi and causes the blink

Question 10

What is the pupillary light reflex

Answer 10

Controls the amount of light on the retina and should give a bilateral response.

• CN 2 detects bright light on eye
• Fibres travel in both tracts to LGN
• Also contralateral branch that travel through the superior colliculus and synapse in pre tectal area
• These tectal neurons project both ipsilaterally an contralaterally via the Edinger Westphal nuclei
• Parasympathetic fibres of CN 3 then synapse at ciliary ganglion
• Postganglionic neurons then innervate constrictor pupillae

Lesion can occur either at optic nerve (afferent) or oculomotor (efferent). If at CN 3 then no response in lesion side. If at CN 2 then only no response (bilateral) when lesion side is being tested.

Question 11

Structure and function of the vestibulospinal tract

Answer 11

Provide both the positional and linear acceleration of the head as well as the rotation movements of the head (ipsilateral)
Lateral vestibulospinal nuclei - muscle tone within deep back extensors in response to gravity. Therefore maintain stance and balance referred to as the vestibulospinal reflex.
Medial vestibulospinal nuclei - stabilise the head during movement (especially rotation) and travel via the medial vestibulospinal tract, perform vestibulo-cervical reflex

Question 12

Structure and function of the tectospinal tract

Answer 12

Act on the muscles of the shoulder and neck. Control reflex movements of the head and neck in response to stimuli.

Cell bodies in superior colliculus which then decussate at the level of the midbrain and decsend to motor neurns in cervial spinal cord via ventral white commisue. However, some fibers remain ipsilateral and follow the same path to inhibt the muscles on one side, while the contralateral innervate the same on the other.

Question 13

Structure and function of the rubrospinal tract

Answer 13

Cell bodies in the red nucleus, due to this location it recieves colateral fibers from the pyramidal tracts (modulated by them). The fibers then decussate right near this origin and descends through lateral funiculus of the spinal cord and ends at the level of the cervical spinal cord (brachial plexus).

Question 14

What is muscle tone

Answer 14

Muscle tone is defined as the continuous and passive partial contraction of the muscle (resistance to passive stretch) during the resting state.

Question 15

Structure and function of reticulospinal tract

Answer 15

The cell bodies are located in the medial column of the caudal pontine and rostral medullary reticular formation. Tract descend ipsilaterally (with some bilaterally) in the anteromedial aspect of the brainstem to the ventral funiculus to all levels of the spinal cord. Due to its extensor bias it provides postural and GIAT adjustments during movement, therefore meaning it helps to control balance during movement. It does that by acting on the extensor groups of all regions.

It is highly mylinated and the response provided are not sterotyped meaning it is very reactive.

Question 16

Answer 16

Question 17

Where does the bsaaal ganglia recieve blood supply from

Answer 17

Middle cerebral artery

Question 18

Input and output to basal ganglia

Answer 18

Input is prefrontal area and output is the supplementary motor cortex via the thalmus (VA and VL)

Question 19

Excitatory and inhibitory neurotransmiters used in basal ganglia loop

Answer 19

Excitatory is glutamatergic and inhibatory is GABAergic

Question 20

What is the direct pathway of the basal ganglia

Answer 20

Question 21

What is the indirect pathway of the basal ganglia

Answer 21

Question 22

What is the role of the Substainta nigra pars compact in th ebasal ganglia

Answer 22

The SNc maintians a functional equilibrium between the two pathways. Does this by using dopamine to eefect both the indirect and direct pathways. Although the effects on each pathway is different the end result is the same, reduce inhibition of thalmic neurons.

In the direct pathway it exctes the D1 recptor facilitying further disinbition to facilite the wanter motor plan.

In the indirect pathway The interneurons present within the striatum normally excite the following inhibitory neurons however, dopamine from the SNc inhibits these interneurons.Therefore the action of SNc is to decrease inhibition of the thalamus allowing for slightly more movement.

Question 23

Disorders associated with basal ganglia

Answer 23

Hyperkinetic disorders are an increased amount of involuntary movement caused by reduced activity of the indirect pathway (example is hungtintons disease)

Hypokinetic is reduce activty of voluntary movement due to reduce activity of direct and more of indirect, cased by degeneration of SNc (example is parkinsons)

Question 24

Functions of the cerebellum

Answer 24

Modulates and coordinates ongoing movements. Recives sensory input and the original motor plan to modulate and evaluate any discrepencies between intention and action. It does not have any direct input into the spinal cord motor neurons but instead influences theese indirectly through descending motor pathways (pyramidal and extra pyramidal)

Question 25

Afferent and efferent aspects of cerebellar peduncles

Answer 25

Superior - axons to and from midbrain

Middle - Axons from pons

Inferior - axons to and from medulla

Question 26

What are the 4 cerebellar nuclei

Answer 26

Denate (lateral) Fastigial (medial) and interposed (globose and emboliform)

Question 27

The regions associated with each cerebellar tract

Answer 27

Vestibulocerebellum (Flocculonodular lobe and fastigial nuclei)

Spinocerebellum (vermis and paravermal regions, interposed and vastigial nuclei)

Cerebrocerebellum/pontocerebellum (lateral cerebellar hemisphers and dentate)

Question 28

Difference between proprioceptive and cutaneous feedback

Answer 28

Sensations closer in nature to tactile stimuli were classified as cutaneous, and those triggering a feeling of movement or change in position were classified as proprioceptive

Question 29

Afferent and efferent tracts for vestibulocerebellar

Answer 29

Afferent - Vestibular nuclei and nerve enter via the inferior cerebellar peduncle. (vestibulocerebellar tract)

Efferent -To vestibular uclei via fastigial nuclei to influence lat/med vestibulospinal tracts, aslso via inferior cerebellar peduncle

Question 30

Afferent and efferent tracts for spinocerebellar

Answer 30

Afferent - Posterior spinocereballar and cuneocereballar tratc s(propriception) as well as input from the inferior olivary nucleus via olivocerebellar tract. All enter via ICP.

Efferent - Via the fastigial and interposed nuclei to reticulospinal (cerebroreticular), rubrospinal and vestibulspinal (cerebrovestibular) as well as the inferior olive (cerebroolivary)

Question 31

Afferent and efferent for the cerebrocerebellar tract

Answer 31

Afferent - Via the middle cerebellar peduncle. Pontocerebellar tract (pontine nuclei to cerebeullum) to contralateral cerebellum. Pontinue nuclei have input from ipsilateral cerebral cortex. These go to dentate nuclei

Efferent - Via the superior cerebellar peduncle. Denate nucleus sends to the thalamus (dentatothalmitact) and to the red nucleu (dentorubral). Dentatothalmic then goes to the cortex (thalmocortical tract)

Question 32

Functions of the different cerebellar loops

Answer 32

Vestibulo cerebellar - Influence the activity of vestibular nuclei for reflex correction. Vstibulospinal reflex (body in COG) {lateral vestibulospinl tract}, Vestibulospinal (stabalise head) {medial vestibulo spinal tract} and vestibuloocular reflex (tabalise gaze during movement) {medial vestibulo spinal tract}

Spinocerebellar - maintain muscle tone and thereofre postural control and limb control

Cerebrocerebellar - Coordinaates fast and alternating movements such as speaking and writing

Question 33

What is the feed forward mechanism of the cerebellum

Answer 33

Allows the prediction of errors based on previous expericnes. Uses the collateral tracts within each of the loops.

Question 34

Feedback mechanism of cerebellum

Answer 34

The movemetn plan is compared with the avliable sensory information resulting from the movement. Therefore can only correct errors that have already happened.

Question 35

Visual pathway lesions

Answer 35

Question 36

Corticonuclear tract

Answer 36

Originates in motor cortex in regions concerende with head and neck. Convereg and pass through the genu and posterior limb of the internal capsule where they descend into the brainstem. These fibers terminate at motor nuclei of the brainstem and provide bilateral innervation.

Functions - provide motor control of the head and neck

Question 37

Shared starting coticpinal tract

Answer 37

The fibers originate in the motor cortex where they converge and pass through corna radiata. They then descened through the posterior limb of the IC and through the crus cerbi of the anterior midbrain. They then diverge to pass hrough the pons and converge agiant to pass through the pyramids.

Question 38

Lateral corticospinal tract after decussation

Answer 38

These fibers decussate at the pyramidal decussation and descend via the lateral colum of the spinal cord. They then terminate when synpasing with LMNs in the anterior horn (manly at levels of brachial and lumbar plexus). Functions to provide skilled movements of the limbs.

Question 39

Anterior corticospinal tract after pyramids

Answer 39

Descend in anterior aspect where majoirty of fibers decussate at the level in whihc they LMN innervation is. However innervation from this trct is often bilatera meaning it functions to prvided postural stability and adjustment.

Question 40

Differences between upper and lower motor neruon lesions

Answer 40

Upper: decreeased muscle strength, increased muscle tone and reflex strength (Babinski), muscle mass maintaied. Injury often caused by stroke meaning that consequences can be nted on contralateral side (decussation has not yet occured)

Lower: decreased muscle strength, muscle tone and reflex sign. Rapid degeneration of muscle mass. Variety of causes (motor neuron disease, spinal cord injury ect)

Question 41

Initiation of horizontal saccades

Answer 41

Initited by cortical (frontal, parietal and sup eye field) or sub cortical (sup colliculus). projects to contralateral PPRF (paramedian pontine reticular formation for horixzontal) +/- ipsilateral superior colliculus which then projects to contralateral PPRF or RMRF (rostral midbrain reticular formation for vertical)

Question 42

Coordination of horizontal gaze

Answer 42

PPRF is located very close to ipsilateral abducens nuclei, PPRF gives input to this nuclei casuing a subset of neurons to travel to ipsilateral lateral rectus. Another subset of neurons travels across the midline to MLF and to contralateral occulomotor nucleus. Occulomotor neurons then inervated ipsilateral medial recuts moving the eye to contrlaateral side.

Therefore, left PPFR controls both eyes moving to the left.

Question 43

What is smooth pursuit movements

Answer 43

Used to keep an image on the fovea. Descending stimulis from the cortex goes to pontine nuclei and cerebellum. From cerebellum have input to vestibular nuclei which will then stimulate somatic fibers.

Question 44

What is the vestibulo-ocular reflex

Answer 44

Vestibular apparatus detects head movement. Vestibular nerve (CN8) to ipsilateral vestibular nuclei. Projects to contralateral abducences nuclei. Projects to ipsilateral lateral rectus and contralateral occulomotor via the MLF

Question 45

What are the three things needed to focus on a near object

Answer 45

Covergence, increased curvature of the lens to increase refractive power and focus on the fovea as well as pupillary contriction to reducce blur and increase depth of field

Question 46

Pathway for accomodation

Answer 46

CN 2 afferent neurons to bilateral LGN in the thalamus where it synpases. Nuron then goes to primary visual cortex and syunpases to continue onto visual association area to synpase. 2 projects into the pretactal area, one syapsing with EW and another to occulomotor. CN 3 somatic fibers to medial rectus and parasympathetic to constrictor pupillae and ciliary muscle.