NEURO CONTENT Flashcards
Name the 5 Plexuses
- Cervical plexus= C1 - C4
- Brachial plexus= C5 - T1
- Intercostal Nerves= T1 - T12
- Lumbar plexus= L1 - S4
- Sacral plexus= L4 - S4
Describe Association Fibres
Association Fibres connect different parts of the same cerebral hemisphere - don’t cross midline
Describe Commissural Fibres
Commissural Fibres connect similar cortical regions of the two cerebral hemispheres. They allow each hemisphere of the brain to access information from both sides
Describe Projection Fibres
Projection Fibres project information up/between different levels of cerebral hemispheres
List the 3 levels of Sensory Cortices
- Primary Sensory Cortex (PSC) receives sensory information from the thalamus
- PSC conveys information to secondary sensory cortex for interpretation
- Multiple secondary association cortices send their sensory information to multimodal posterior association area for integration
List the 3 levels of Motor Cortices
- Motor command initiated in brain and exits brain via the primary motor cortex
- Prefrontal cortex/anterior association area generates motor commands and transfers them to Premotor Cortex and Supplementary Motor cortex for integration
- The supplementary motor cortex and premotor cortex transfer motor command to primary motor cortex for execution
State function of limbic system
Learning, memory, emotions
State structural components of the limbic system
- cingulate and parahippocampal gyri, orbitofrontal cortex, subcallosal area, hippocampus proper, dentate gyrus, entorhinal cortex, subiculum
- amygdala, hypothalamus, mammillary bodies, anterior nucleus of thalamus
- fornix, hippocampus (fornical) commissure, cingulum, unite fascicle
Describe the 5 types of neurons
1a = from muscle spindle (proprioception)
1b = from Golgi tendon organs (proprioception) and Ruffini endings (pressure)
11 = from skin receptors
111 (a delta) = free nerve endings (dendrites) for fast pain and temperature
1V (c fibres) = free nerve endings (dendrites) for slow pain and temperature
List the 6 steps of the ANTEROLATERAL PATHWAY
- 1st order neuron travels through spinal ganglia to spinal cord
- Before 1st order neuron enters grey matter to synapse, it either ascends or descends through Lissauer’s tract (white matter) until reaching desired level
- 1st order neuron synapses with 2nd order neuron in posterior horn of spinal cord
- 2nd order neuron decussates through ventral white commissure to anterolateral area
- Information then travels to different areas to synapse with 3rd order neuron, depending on function (5 divisions of anterolateral pathway)
- 3rd order neurons travel to posterior central gyrus (primary somatosensory cortex)
Function of ANTEROLATERAL PATHWAY
Controlling response to pain
Describe the SPINOTHALAMIC division of the ANTEROLATERAL PATHWAY
Travels to VPL thalamic nuclei
= conscious awareness of nociception
Describe the SPINOMESENCEPHALIC division of the ANTEROLATERAL PATHWAY
Travels to PAG thalamic nuclei
= descending pain modulation
Describe the SPINORETICULAR division of the ANTEROLATERAL PATHWAY
Travels to Reticular Formation thalamic nuclei
= arousal/attention
Describe the SPINOBULBAR division of the ANTEROLATERAL PATHWAY
Travels to brainstem nuclei
= adaptive responses
Describe the SPINOHYPOTHALAMIC division of the ANTEROLATERAL PATHWAY
Travels to hypothalamus
= automatic responses to nociception
List the 8 steps of the DORSAL COLUMN PATHWAY
- 1st order neuron travels to dorsal column
- 1st order neuron ascends through fasciculus gracilis and fasciculus cuneatus of dorsal column to medulla
- Fibres that travel through fasciculus gracilis (below T6) synapse with 2nd order neurons in nucleus gracilis of medulla
- Fibres that travel through fasciculus cuneatus synapse with 2nd order neurons in nucleus cuneatus of medulla
- 2nd order neuron decussates immediately in medulla - called the internal arcuate fibres during decussation
- Fibres then ascend through tegmenjtum, starting medially and moving laterally - called medial lemniscus
- Travels to VPL of thalamus where it synapses with 3rd order neuron
- 3rd order neuron travels to primary somatosensory cortex
Function of DORSAL COLUMN PATHWAY
Discriminate touch, vibration and conscious proprioception
List the 4 steps of the POSTERIOR SPINOCEREBELLAR TRACT
- Proprioceptive information from muscles spindles and Golgi tendon organs (1a, 1b and 11 fibres) and from skin enters spinal cord from C8 and below
- Fibres travel through fasciculus gracilis until they reach L3, where the 1st order neuron synapses with the 2nd order neuron in Clarke’s nucleus (which extends from L3 to C8)
- Fibres then ascend in posterior spinocerebellar tract through the ipsilateral lateral funiculus of spinal cord to brainstem
- Fibres then travel through inferior cerebellar peduncle to ipsilateral cerebellum (anterior lobe and vermis)
Function of POSTERIOR SPINOCEREBELLAR TRACT
Use information from skin, muscles and joints for ongoing coordination of movement to facilitate motor learning
For C8 and below
For Lower Limbs and Trunk
List the 4 steps of the CUNEOCEREBELLAR TRACT
- 1a, 1b and 11 fibres, as well as fibres from skin receptors enter spinal cord in C7 and above
- Fibres travel through fasciculus cuneatus to rostral medulla
- 1st order neuron synapses in accessory cuneate nucleus in medulla
- Fibres then travel through inferior cerebellar peduncle to ipsilateral cerebellum (anterior lobe, vermis, intermediate region)
Function of CUNEOCEREBELLAR TRACT
Use information from skin, muscles and joints for ongoing coordination of movement to facilitate motor learning
For C7 and above
For Upper Limbs
List the 4 steps of the ANTERIOR SPINOCEREBELLAR TRACT
- Proprioceptive information from 1a, 1b fibres enter spinal cord and synapse with 2nd order neuron in spinal border cells on lateral edge of anterior horn
- 2nd order neuron decussates and ascends collaterally as anterior spinocerebellar tract
- From pons, fibres enter cerebellum via superior cerebellar peduncle
- Fibres then decussate back to original side and project to anterior lobe and vermis of cerebellum
List the 7 steps of the VISUAL PATHWAY
- Begins in the eye - photoreceptors (rods and cones) in the retina
- Photoreceptors stimulate the 1st order neuron (bipolar cells)
- Bipolar cell synapses with the 2nd order neuron (ganglion cell)
- Axons of ganglionic cell exit the eye through optic disc as optic nerve
- Optic nerve travels through optic chasm and is then called the optic tract
- Optic tract synapses at LGN of thalamus
- The 3rd order neuron travels to primary visual cortex as the optic radiation
Define lateralisation of the visual field
Left and Right visual field end up in the contralateral visual cortex
Draw a diagram of the lateralisation of the visual field
See book for answers
Draw a diagram of the Lesions of the optic pathway
See book for answers
What does a lesion in the RETINA or OPTIC NERVE result in?
= monocular vision loss
What does a lesion in the CENTRAL OPTIC CHIASM result in?
= bitemporal hemianopia
What does a lesion in the LEFT or RIGHT OPTIC CHIASM result in?
= monocular ipsilateral nasal hemianopia
What does a lesion in the OPTIC TRACT or PRIMARY VISUAL CORTEX result in?
= contralateral homonymous hemianopia
What does a lesion in the PARIETAL OPTIC RADIATION result in?
= contralateral inferior quadrantanopia
What does a lesion in the TEMPORAL OPTIC RADIATION result in?
= contralateral superior quadrantanopia
Describe the function of the CORNEAL BLINK REFLEX
Blink and produce tears when something touches the eye
List the 3 steps of the CORNEAL BLINK REFLEX
- Foreign object in eye detected by opthalamic division of trigeminal nerve (CN V)
- Information travels through trigeminal nerve to spinal trigeminal nucleus (nociception) and the chief sensory nucleus (touch)
- Interneurons synapse with facial nerve motor neurons (CN V11) to innervate orbicularis oculi to blink and facial nerve parasympathetic neurons (tears to wash eye)
Describe Vertical Conjugate Eye Movements (GAZE)
- centre located in rostral midbrain, reticular formation and pretectal area
- affected by lesion in midbrain
Describe Horizontal Conjugate Eye Movements (GAZE)
- centre located in paramedian pontine reticular formation
- affected by lesion in pons and/or cortex (cortical lesion)
Describe the function of the VESTIBULO-OCULAR REFLEX
Generates fast eye movement to compensate for head movements in oder to keep the fovea fixed on an object
List the 4 steps of the VESTIBULO-OCULAR REFLEX
- Head movements are detected by the vestibular nerve (CN V111)
- This stimulates the ipsilateral vestibular nuclei at pons/medulla junction
- Projects to contralateral abducens nerve nucleus (CN V1)
- Projects to ipsilateral abducens nerve (CN V1) to innervate lateral rectus and contralateral oculomotor nucleus to the oculomotor nerve (CN 111) to innervate medial rectus
Describe the function of the ACCOMODATION REFLEX
Focusing on a near object
List the 6 steps of the ACCOMODATION REFLEX
- Optic nerve (CN 11) afferents to bilateral LGN
- Primary visual cortex
- Visual association area
- Project to pretectal area
- Oculomotor and Edinger-Westphal nuclei
- Innervates oculomotor nerve (CN 111) to innervate medial rectus, ciliary muscle and constrictor pupillae
Describe the function of the PUPILLARY LIGHT REFLEX
Controls the amount of light entering the eye
List the 7 steps of the PUPILLARY LIGHT REFLEX
- Cover one eye and shine light in other eye
- Light is detected and carried by optic nerve (CN 11)
- Collaterals carry information through brachium of superior colliculus to pretectal area
- In pretectal area, pretectal neurons project bilaterally to Edinger-Westphal nucleus and ipsilaterally through posterior commissure
- Parasympathetic fibres comes back out with the oculomotor nerve (CN 111)
- Oculomotor nerve synapses with ciliary ganglion
- Ciliary nerve innervates constrictor pupillae, causing pupil to constrict
Describe the APRAXIA
- caused by lesion to premotor or supplementary motor cortices
APRAXIA= inability to execute voluntary movement despite being able to demonstrate normal muscle function, it also includes inability to imitate a movement
Describe the origins of Corticomotor Pathways
40% = primary motor cortex 40% = supplementary motor and premotor cortices 20% = primary sensory cortices
Describe the damage to Corticomotor Pathways
Primary motor cortex lesion = paresis (muscle weakness)
Premotor/Supplementary Cortices damage = apraxia
Primary Somatosensory Cortex damages = leads to degeneration of motor actions
List the 4 steps of the CORTICONUCLEAR PATHWAY
- Input received from primary motor, premotor, supplementary motor and primary sensory cortices
- Travels to posterior limb of internal capsule
- Corticonuclear neurons are located in the very anterior posterior limb or near the genu of internal capsule
- Corticonuclear neurons then go off to different motor nuclei
List the 8 steps of the LATERAL CORTICOSPINAL PATHWAY
- Input received from primary motor, premotor, supplementary motor and primary sensory cortices
- Travels to posterior limb of internal capsule
- Corticospinal neurons keep descending through posterior limb of internal capsule
- Descends through the mid portion of crus cerebri
- Split up slightly and travel through base of pons
- Descends through medulla to medullary pyramids
- 90% of fibres decussate at caudal pons and descend through lateral funiculus of spinal cord
- When fibres reach desired spinal level, they synapse to innervate skeletal muscle for movement
List the 8 steps fo the ANTERIOR CORTICOSPINAL PATHWAY
- Input received from primary motor, premotor, supplementary motor and primary sensory cortices
- Travels to posterior limb of internal capsule
- Corticospinal neurons keep descending through posterior limb of internal capsule
- Descends through the mid portion of crus cerebri
- Split up slightly and travel through base of pons
- Descends through medulla to medullary pyramids
- 10% of fibres remain ipsilateral and descend in anterior column, either side of the ventral median fissure
- When fibres reach desired spinal level, they synapse to innervate skeletal muscle for movement
Describe UMN lesions above the midbrain and symptoms
UMN lesions above midbrain result in removal of influence of corticospinal tract (=decortication) on rubrospinal, reticulospinal and vestibulospinal tracts
symptoms:
decorticate rigidity with flexion of UL and extension of LL
Describe UMN lesions below the midbrain and symptoms
UMN lesions below midbrain result in removal of rubrospinal tract in addition to removal of influence of corticospinal tract on reticulospinal and vestibulospinal tract
symptoms:
decerebrate rigidity with extension of both UL and LL due to unopposed extensor-biased UMN activity
List the 4 steps of the RETICULOSPINAL TRACT
- Gains input primarily from motor cortex, but also the cerebellum, basal ganglia, vestibulospinal tract and tectospinal tract
- Medial reticulospinal tract originates in medial column of pontine reticular formation
Lateral reticulospinal tract originates in medial column of medullary reticular formation - Descends mainly ipsilaterally but also some bilaterally to the ventral horn of all spinal levels
- Innervates muscles for upright body posture and gait control
List the 4 steps of the VESTIBULOSPINAL TRACT
- Gains input mainly from vestibular apparatus but also from cerebellum
- Medial vestibulospinal tract originates from medial vestibular apparatus
Lateral vestibulospinal tract originates from lateral vestibular apparatus - Medial vestibulospinal tract descends bilaterally
Lateral vestibulospinal tract descends ipsilaterally - Medial vestibulospinal tract descends to cervical spinal level to innervate neck muscles
Lateral vestibulospinal tract descends to all spinal levels to innervate muscles of balance
List the 4 steps of the TECTOSPINAL TRACT
- Gains visual input from retina, auditory input from inferior colliculi and sensory input from spinal cord
- Originates from superior colliculi in tectum
- Immediately decussates into tegmentum on midbrain level and acts bilaterally
- Descends and terminates at alpha and gamma motoneurons in the cervical spinal level to innervate neck and shoulder muscles
List the 5 steps of the RUBROSPINAL TRACT
- Gains input from corticomotor tracts
- Tract originates from red nucleus
- Decussates immediately in midbrain tegmentum
- Descends contralaterally through lateral column of the spinal cord to cervical spinal level
- Innervates flexor muscles of UL
List the components of the BASAL GANGLIA and its neurotransmitters
Striatum (STR)
i. caudate nucleus= GABA and acetyl choline
ii. putamen= GABA and acetyl choline
Globus Pallidus (GP)
i. globus pallidus externus (GPe) = GABA
ii. globus pallidus internus (GPei) = GABA
Substantia Nigra (SN)
i. substantia nigra pars compacta (SNc) = dopamine
ii. substantia nigra pars reticulata (SNr) = GABA
Subthalamic Nucleus (STN) = glutamate
Describe blood supply of basal ganglia
Basal Ganglia are mostly supplied by the middle cerebral artery
Describe the function of basal ganglia
Controlling voluntary movement by selecting specific motor programs that are stored within the motor cortex
List the steps of the DIRECT PATHWAY
Cerebral Cortex
Striatum (STR)
GPi and SNr
Thalamus (VA, VL)
Describe the function of the direct pathway
Disinhibits thalamocortical tract, thus increasing thalamocortical activity
List the steps of the INDIRECT PATHWAY
Cerebral Cortex Striatum (STR) GPe STN GPi and SNr Thalamus (VA, VL)
Describe the function of the indirect pathway
Inhibits/ suppresses unwanted/competing motor plans
Describe the function of the SNc influence on the DIRECT PATHWAY
Further increases/excites the direct pathway
Describe the function of the SNc influence on the INDIRECT PATHWAY
Inhibits the indirect pathways, facilitating movement initiated by the motor cortex
Describe Huntington’s Disease including what is effected, noticeable features and symptoms
- D2 neuronal receptors are affected
- impacts the indirect pathway
- affected by lesion in striatum (caudate nucleus)
- symptoms: chorea, excessive involuntary movement
Describe Parkinson’s Disease including what is effected, noticeable features and symptoms
- substantia nigra is impacted
- impacts both direct and indirect pathways
- lightened substantia nigra is seen in Parkinson’s patients
- symptoms: slowness of movement, absence of movement
Describe the blood supply of the CEREBELLUM
Superior 1/2 = supplied by superior cerebellar artery
Inferior 1/2 = supplied by anterior and posterior inferior cerebellar artery
List the 4 Deep Cerebellar Nuclei
- Dentate Nuclei
- Fastigial Nuclei
- Emboliform Nuclei
- Globose Nuclei
Emboliform and Globose Nuclei = Interposed Nuclei
Describe Climbing Fibres
- go to Purkinje cells
- only from the inferior olivary nucleus
- inhibitory
Describe Mossy Fibres
- go to granular cells
- from everywhere
Describe the Cerebrocerebellum:
a) Structures
b) Connectivity
c) Function
a) lateral hemisphere, dentate nucleus
b) afferent fibres= contralateral premotor cortex
efferent fibres = motor cortex via thalamus and red nucleus
c) Coordinate fast and alternating movements by planning movements with regard to their direction timing and force
Describe the Spinocerebellum:
a) Structures
b) Connectivity
c) Function
a) anterior lobe, vermis, intermediate hemisphere, fastigial and interposed nuclei
b) spinal cord: posterior spinocerebellar, cuneocerebellar
c) Regulates muscle tone, posture and balance
Describe the Vestibulocerebellum:
a) Structures
b) Connectivity
c) Function
a) flocculonodular lobe, fastigial nuclei
b) Vestibular nuclei and nerve
c) Influence vestibular nuclei for error connection of the vestibulo-cervical, vestibulo-spinal and vestibulo-ocular reflex
What does a lesion to the Spinocerebellum result in?
Trunk Ataxia
What does a lesion to the Vestibulocerebellum result in?
Trunk Ataxia
What does a lesion to the Cerebrocerebellum result in?
Limb Ataxia
Draw the summary of the Cerebrocerellum loop
See book for diagram
Draw the summary of the Spinocerebellum loop
See book for diagram
Draw the summary of the Vestibulocerebellum loop
See book for diagram
What lower motoneurons are targeted by the descending pathways
- alpa and gamma motoneurons of the spinal anterior horn
- motor neurones of cranial nerves in the brainstem
What muscles does the Lateral Corticospinal pathway innervate
- upper and lower limb muscles
What muscles does the Anterior Corticospinal pathway innervate
- axial (neck and trunk) muscles
What pathways are CONSCIOUS
- anterolateral
- dorsal column
- corticonuclear
- lateral corticospinal
- anterior corticospinal
What pathways are SUBCONSCIOUS or UNCONSCIOUS
- posterior spinocerebellar
- cuneocerebellar
- anterior spinocerebellar
- reticulospinal
- vestibulospinal
- tectospinal
- rubrospinal