POST-MIDSEM Flashcards
Why do we have arches in the foot?
- space for tendons and neurovascular structures
- stops compression of the nerves/blood vessels/tendons
- increases speed of locomotion (i.e. running requires bigger arch)
- allows for deformable foot which can accomodate different surfaces
What does the navicular drop test assess?
the integrity of the medial longitudinal arch
what is the most commonly fractured tarsal fracture?
= navicular
Describe the distal/inferior tibiofibular joint
is a syndesmosis
between:
- ant. tibiofibular ligament
- post. tibiofibular ligament
- interosseous membrane
Describe the talocrural joint
Synovial hinge joint
Describe the Calcaneopedal unit and what movements it links
- 3D motion of the head of the talus in acetabulum formed by calcaneus, navicular and spring ligament
- links foot pronation and internal rotation
Describe plantar fascia and its function in the foot
- deepest portion of plantar fascia= plantar aponeurosis
- the plantar fascia has twice the tensile strength than other plantar ligaments
- we require a rigid foot for push-off during gait; the plantar fascia pushes the calcaneal tuberosity posteriorly and MTP hyperextension which tenses the plantar aponeurosis which holds the foot rigid for push-off
What is the core control system of the foot? What are the 3 sub-systems?
- control=stability, movement 3 Subsystems: Neural Passive Active
Describe the active subsystem of the core control system of the foot
active subsystem= plantar intrinsic foot muscles
- control the rate and extent of deformation of the arch
- local stabilisers provide a stable base for the large extrinsic muscles, with greater PCSA and moment arms to produce gross motion
- or to resist large external movements during late stance and push off phases
Generally describe the dorsal column pathway
- discriminative touch (localised and 2 point discrimination)
- pressure
- vibratory sense
- conscious proprioception
Generally describe the anterolateral pathway
- nociception
- temperature
- crude touch
Describe Lissauer’s Tract
- some 1st order neurons enter the dorsal horn and synapse
- others divide into ascending and descending branches which travel in the dorsolateral tract before entering the dorsal horn and synapsing
Describe the spinothalamic pathway and where it travels
= spinothalamic to VPL
- conscious awareness of nociception (pain)
Describe the spinomesencephalic pathway and where it travels
= spinomesencephalic to PAG
- descending pain modulation
Describe the spinoreticular pathway and where it travels
= spinoreticular to RF
- arousal/attention
Describe the spinobulbar pathway and where it travels
= spinobulbar to brainstem nuclei
- adaptive responses
Describe the spinohypothalamic pathway and where it travels
= spinohypothalamic to hypothalamus
- autonomic response to nociception
Describe the spinocerebellar tract
- information from skin, muscles and joints to the cerebellum for coordination of movement and to facilitate motor learning
List and describe the 6 steps of the DORSAL COLUMN PATHWAY
- Axons enter the spinal cord from the spinal ganglion and pass directly to ipsilateral posterior column. Caudal fibres (below T6) enter fasciculus gracilis (medial) and rostral fibres (above T6) enter fasciculus cuneatus to ascend.
- These axons terminate in the nucleus gracilis and nucleus cuneatus. From these nuclei, axons of secondary neurons cross the midline as internal arcuate fibres and form the medial lemniscus
- In the rostral medulla, the fibres travel as the medial lemniscus adjacent to the midline
- In the caudal pons, the medial lemniscus flattens horizontally
- As the medial lemniscus continues to ascend through the rostral pons and midbrain; it moves laterally and vertically
- The medial lemniscus terminates in the VPL of the thalamus. From the thalamus, fibres project through the internal capsule and corona radiate to terminate in the primary somatosensory cortex (post central gyrus)
List and describe the 5 steps of the ANTEROLATERAL PATHWAY
- Axons enter the spinal cord from the spinal ganglion, travel up or down 1-2 segments in the Lissauer tract, and then synapse in the posterior horn
- Anterolateral tract in the caudal medulla
- In the rostral medulla, the anterolateral tract lies between the inferior olivary nucleus and the nucleus of the spinal tract of the trigeminal nerve
- In the pons and midbrain, the anterolateral tract lies lateral to the medial lemniscus
- The anterolateral tract terminates in the VPL of the thalamus. From the thalamus, fibres project through the internal capsule and corona radiate to terminate in the primary somatosensory cortex (post central gyrus)
Where does lateralisation of the visual field occur?
in the optic chiasm
Give the degrees of normal external tibial torsion
20 - 40 degrees
Where do tibial stress fractures occur
- the posteromedial tibia near the junction of the middle and distal third of the bone, this is where the cortex of the shaft is narrow
Compare the relative length of the metatarsals and phalanges of the foot with the metacarpals and phalanges of the hand
- MC are relatively shorter than MT
- phalanges of the hand are longer than phalanges of the foot
- all MC have relatively same thickness/diameter
- 1st MT is thickest of the MT
Compare the mobility and function of the 1st ray and hallux with that of the thumb
- thumb= saddle joint for opposition
- 1st MT= synovial condyloid joint for less movement that thumb
What bones make up the Medial Longitudinal Arch
- 1st, 2nd and 3rd ray
- cuboid
- calcaneus
What bones make up the Lateral Longitudinal Arch
- calcaneus
- 5th ray
What bones make up the Transverse Arch
- 1st to 5th MT
The stability of the inferior tibiofibular joint is crucial to the integrity of the talocrural joint. Explain this
- inferior tibiofibular joint permits slight movements so that the lateral malleolus (bone outside talocrural joint) can rotate laterally during dorsiflexion of the ankle
Explain the usual mechanism of injury of the inferior tibiofibular joint and the structures involved
- most commonly, extreme external rotation of dorsiflexion of talus
Which ligament is most commonly injured in an ankle sprain? Explain how and why?
= anterior tibiofibular ligament
ER of foot relative to the leg turn the talus within the mortise (bony arch formed by tibial plafond and the two malleoli). This forces separation of the distal fibula and tibia which tears the anterior tibiofibular ligament and can potentially fracture the fibula
Describe the articulations and the 3 ligaments of the Subtalar Joint
between: the talus and the posterior articular facet of the calcaneus
ligaments:
- calcaneofibular
- tibiocalcaneal
- interosseous ligament within the sinus tarsi
Describe the articulations and the 2 ligaments of the Talocalcaneonavicular Joint
between: the head of the talus and the anterior and middle calcanael facets and the navicular and the spring ligament
ligaments:
- dorsal calcaneonavicular
- plantar calcaneonavicular (spring) ligament
Describe the 3 ligaments of the Calcaneocuboid Joint
ligaments:
- dorsal calcaneocuboid ligament
- plantar calcaneocuboidal ligament
- long plantar ligament
What 2 ligaments provide substantial support for the Lateral Longitudinal Support of the Foot
- plantar calcaneocuboidal ligament
- long plantar ligament
Define Calcaneal Valgus
= lateral eversion of rear foot at subtalar joint
Define Calcaneal Varus
= medial inversion of rear foot at subtalar joint
Define Hallux Valgus
= lateral deviation of the 1st digit
Compare and contrast the bone and joint structure and function of the ankle and the wrist
function of wrist = optimise hand function function of ankle = up/down, side-to-side movements, maintain balance, adapt to undulations on the ground
Compare and contrast the bone and joint structure and function of the foot and hand
hands= optimised for manipulation of objects foot= weight-bearing, also to function as a somewhat flexible structure to conform to undulations on the ground
What does the trigeminal ganglion contain
= the trigeminal ganglion is homologue to the dorsal root ganglia as it contains cell bodies of (pseudo) unipolar sensory neurons
List the 4 Steps of the Corneal Blink Reflex
- Foreign object is detected in the eye by the ophthalmic division of the trigeminal nerve (CN5)
- Synapse in spinal trigeminal (nociception) and chief sensory (touch) nuclei
- Interneurons synapse bilaterally with facial nerve nucleus motor neurons
- Facial Nerve (CN7) innervates orbicularis oris leading to to blinking
List the 6 Steps of the Pupillary Light Reflex
- Shining a bright light in one eye (while the other eye is shielded) stimulates the optic nerve (CN2)
- Fibres travel in both optic tracts
- Collaterals through brachium of superior colliculus to pretectal area
- Pretectal neurons project bilaterally via the posterior commissure to Edinger-Westphal nucleus
- Oculomotor nerve (CN3) parasympathetic fibres to ciliary ganglion
- Post-ganglionic neurons innervate constrictor pupillae
What is the difference between the Pupillary Light Reflex and all the other reflexes
The Pupillary Light Reflex is the only reflex that when it occurs in one eye, it will automatically happen in the other as well
List the 5 Steps of the Accomodation Reflex
- Optic nerve (CN2) afferents to bilateral LGN (thalamus)
- Then to primary visual cortex and visual association cortex
- Then project to pretectal area
- Then to oculomotor and Edinger-Westphal nuclei
- Then to oculomotor nerve (CN3) whose somatic fibres innervate medial rectus and the parasympathetic fibres innervate ciliary muscle and constrictor pupillae
List the 6 Steps of the Vestibulo-Ocular Reflex
- Vestibular apparatus detects head movement
- Travels along vestibular nerve (CN8)
- Ipsilateral vestibular nuclei at pons/medulla junction
- Project to contralateral abducens nucleus (pons)
- Projects to ipsilateral abducens nerve (CN6) to innervate lateral rectus and contralateral oculomotor nucleus, midbrain via the MLF
- Stimulates oculomotor nerve (CN3) for medial rectus muscle
Explain how the structure of a lumbar intervertebral disc aids its role in WEIGHT-BEARING
- nucleus pulposus is incompressible
- vertical compression of nucleus pulposus (decreases vertical height)
- expands radially and exerts pressure on annular fibres
- annular fibres resist tension
- exert pressure back onto nucleus puplosus
- nucleus pulopsus and annular fibres share the pressure
- pressure exerted onto vertebral endplates
- transmits load to inferior vertebrae
Explain how the structure of a lumbar intervertebral disc aids its role in FACILITATING MOVEMENT
- the intervertebral disc interposed between two flat articular surfaces permits rocking of superior vertebrae
= movement and stability - deformation of intervertebral discs contributes to intervertebral motion
- ratio of intervertebral disc height to vertebral body height; if low= low mobility/greater stability
Explain how the structure of a lumbar intervertebral disc aids its role in RESISTING MOVEMENT
- collagen fibres in annulus fibrosus resist tension
- in flexion, extension and lateral flexion; compression of intervertebral disc leads to restriction of these movements
What does the anterior longitudinal ligament resist?
= extension
What does the posterior longitudinal ligament resist?
= flexion
What does the interspinous ligament resist?
= flexion
What does the supraspinous ligament resist?
= flexion
What does the intertransverse ligament resist?
= lateral flexion
What does ligamentum flavum resist?
= flexion
How does the vertebral body resist compression
- inner portion is cancellous bone, the vertical trabecular, supported by horizontal trabecular, withstand compressive forces
How does the articular processes and zygapophysial joint resist compression
- some compression forces may be transmitted from the inferior articular process of the superior vertebra to the superior articular process or pars interarticularis of the vertebra below.
What is the pars interarticularis
= lamina between articular processes
Explain the mechanism causing a pars interarticular defect
- fatigue fracture caused by repetitive loading and unloading of this region of the vertebra from physical activity; as a result L5 body slips forward on the S1 vertebral body
(also common at L4 and L5 levels)
Define spondylolysis
= fracture in pars interarticularis. Vast majority of cases occur in lower lumbar (L5), but also can occur in cervical region
Define spondylolisthesis
= slipping of vertebrae, most cases at lower lumbar region
What is the intervertebral motion segment
= when the superior vertebrae moves on the inferior vertebrae
Explain the bilateral movements of the head and neck when the sternocleidomastoid contracts concentrically
- upper cervical extension
- lower cervical flexion
Explain the unilateral movements of the head and neck when the sternocleidomastoid contracts concentrically
- ipsilateral lateral flexion
- contralateral axial rotation
Where does the lower visual field travel through
= parietal optic radiation
Where does the upper visual field travel through
= via the Meyer Loop through the temporal lobe
What are the 3 requirements of the Accomodation Reflex
- Convergence so that the object falls on both fovea
- Increase curvature of the lens to increase refractive power to focus the image on the fovea
- Pupillary constrict reduces blur and increases depth of field
What are the articulations of the Transverse ligament of Atlas and what movements does it resist
articulations:
- between the inner (medial) surface of each lateral mass
resists:
- forward translation of C1 and C2
What are the articulations of the Alar ligament of Atlas and what movements does it resist
articulations:
- from posterior odontoid process to margins of foramen magnum
resists:
- flexion, lateral flexion, axial rotation of head and C1 on C2, is also a secondary restraint to anterior translation of C1 and skull on C2
What are the articulations of the Atlanto-Occipital Joint and what movements does it allow
articulations:
- between convex occipital condyles and deep concave superior articular facets of C1
allows:
- movements of flexion and extension
What are the articulations of the Atlantoaxial Joint and what movements does it allow
articulations:
> (1) Median Atlantoaxial joint: between odontoid process and osseo-ligamentous ring
> (2) Lateral Atlantoaxial joint: between convex inferior articular facets of C1 and convex superior articular facets of C2
allows:
- movements of axial rotation
Describe the 3 column weight transmission in the lower cervical vertebral column
- from C2 and below there are three pathways that share the load transfer
36% through vertebral bodies and discs
2 x 32% through zygopophyseal joints on the lateral sides of the vertebral column
Define Apraxia
= inability to execute a voluntary motor movement despite being able being able to demonstrate normal muscle function; it also includes inability to imitate a movement
Describe the cortical origin of the corticospinal pathways
- although the origin of the corticospinal tract is often shown as the primary motor cortex, note that it originates from the following different cortical areas:
40% from the primary motor cortex
40% from the supplementary and premotor cortices
20% from the primary sensory cortex
What does a lesion in the primary motor cortex lead to:
- leads to paresis (muscle weakness)
What does a lesion in the premotor cortices (SMC and PMC) lead to
- leads to lack of skilled movement (apraxia)
What does a lesion in the primary sensory cortex lead to
- leads to degeneration of motor actions
In a cross-section of spinal cord, what is the function of fasciculus gracilis
= sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
In a cross-section of spinal cord, what is the function of fasciculus cuneatus
= sensory (fine touch, vibration, proprioception) from ipsilateral upper limb
In a cross-section of spinal cord, what is the function of the spinocerebellar tract
= proprioception from limbs to cerebellum
In a cross-section of spinal cord, what is the function of the lateral corticospinal tract
= motor to ipsilateral anterior horn (mostly limb musculature)
In a cross-section of spinal cord, what is the function of the spinothalamic tract
= pain and temperature from contralateral side of the body
In a cross-section of spinal cord, what is the function of the anterior corticospinal tract
= motor to ipsi and contralateral anterior horn (mostly axial musculature)
In a cross-section of spinal cord, what is the function of the anterior white commissure
= pain and temperature fibres cross.
= Anterior corticospinal tract fibres cross
Where do the fibres originate and terminate in the lateral corticospinal tract
originate: from the motor cortex
terminate: ventral horn of the spinal cord at the cervical/thoracic and lumbosacral levels to innervate the upper and lower limbs
What percentage does that Lateral Corticospinal Tract make up, what does it innervate and where is its target location
- 90%
- innervates the limbs (distal more than proximal)
- therefore, it targets alpha-motoneurons that feed into the brachial and lumbosacral plexuses
What percentage does that Anterior Corticospinal Tract make up, what does it innervate and where is its target location
- 10%
- innervates axial muscles (neck, thoracic and abdominal)
- therefore, it synapses with alpha-motoneurons that are located at spinal levels C1-C4 and T2-T12
Discuss an UPPER motor neurone lesion: what does it interrupt and what does it affect
= interrupts the descending influences on the LMN
affects include:
- increased spasticity and spastic paralysis
- increased muscle tone
- increased tendon reflexes
- long term disuse atrophy
- extensor plantar response
Discuss an LOWER motor neurone lesion: what does it interrupt and what does it affect
= interrupts the motor input to muscle affects include: - flaccid paralysis (complete) weakness - decreased resistance to passive strength - decreased tendon reflexes - acute muscle atrophy
What is Poliomyelitis
- neurons of the anterior horn are specifically affected by polio virus
Give an example of a motor neuron disease and list the affects
= Amyotrophic Lateral Sclerosis (ASL) or Lou Gehrig’s Disease
- fatal, progressive neurodegenerative disease
- degeneration of upper and low motoneurons
- genetic and sporadic forms
- leads to muscle weakness and atrophy
Name the 3 corticomotor tracts
- Lateral Corticospinal tract
- Anterior Corticospinal tract
- Corticobulbar (corticonuclear) tract
Name the 4 Extrapyramidal tracts
- Tectospinal tract
- Rubrospinal tract
- Reticulospinal tract
- Vestibulospinal tract
What happens if the pyramidal system is immature (babies) or destroyed (stroke patients)?
- if the input of the pyramidal system to the rubrospinal tract is removed (i.e. lesion), the rubrospinal tract acts as a tonic flexor of the arm muscle
- it is assumed that foetuses and newborn babies, but also stroke patients, display a particularly strong flexor tone in the upper limbs owing to disinhibition of the rubrospinal tract (lack of pyramidal tract input)
Discuss an UMN lesion above the midbrain and its symptoms
UMN lesions above the midbrain result in removal of influence of corticospinal tract (=decortication) on rubrospinal, reticulospinal and vestibulospinal tracts
symptoms: decorticate rigidity with flexion of upper limbs and extension of lower limbs
Discuss an UMN lesion below the midbrain and its symptoms
UMN lesion below the midbrain result in removal of the rubrospinal tract in addition to the removal of the influence of the corticospinal tract on reticulospinal and vestibulospinal tract
symptoms: decerebrate rigidity with extension of both upper and lower limbs due to unopposed extensor-biased UMN activity
Where do the corticonunclear and corticospinal pathways originate from?
= primary motor cortex, supplementary motor cortex and premotor cortex
Which other neutrons travel through the posterior limb of the internal capsule?
= ascending fibres from VPL and VPM
What proportion of fibres decussate at the pyramidal decussation?
Where will they descend in the spinal cord and what is this tract called?
Which spinal cord levels and what is the specific location of the lower motor neuron cell bodies that they synapse with?
What is their function?
- 90% of fibres decussate through to the lateral funiculus, called the lateral corticospinal tract
- synapse in the ventral horn between levels C5-T1 and L1-S3 and decussate here as well
- innervates distal limb muscles
What proportion of fibres DO NOT decussate at the pyramidal decussation?
Where will they descend in the spinal cord and what is this tract called?
Which spinal cord levels and what is the specific location of the lower motor neuron cell bodies that they synapse with?
What is their function
- 10% of fibres do not decussate and instead descend through the anterior column of the spinal cord, called the anterior corticospinal tract
- synapse in the ventral horn between levels C1-C4 and T1-T12
- innervates axial muscles
Describe the extensor plantar response
= touching the sole (bottom) of the foot with something sharp causes the toes to respond
Describe the pathway of the Corticonuclear tract
motor cortex to posterior limb of internal capsule to crus to cranial nerve nuclei
Describe the pathway of the Lateral Corticospinal tract
motor cortex to posterior limb of internal capsule to crus through pyramidal decussation to lateral funiculus
Describe the pathway of the Anterior Corticospinal tract
motor cortex to posterior limb of internal capsule to crus through pyramidal decussation to anterior column
List all the tracts that travel through the lateral column of the spinal cord
- Rubrospinal tract
2. Corticospinal tract
List all the tracts that travel through the anterior column of the spinal cord
- Tectospinal tract
- Reticulospinal tract
- Vestibulospinal tract
Why does the rubrospinal tract get collateral input from the corticospinal pathway?
Due to the pyramidal tract alpha motoneurons which innervates skeletal muscles
so the rubrospinal tract isn’t always on
Describe the action and function of the reticulospinal tract when you lift and weight in front of your body
- reflex causes back, hip and ankle to extend
- avoids forward postural sway
What reflexes does the lateral vestibulospinal tract control?
= vestibular spinal reflex (to control antigravity muscles for balance and posture)
What reflexes does the medial vestibulospinal tract control?
= vestibular ocular reflex
= vestibular cervical reflex (for head movement)
All ascending pathways pass through the ?? of the brainstem
= tegmentum
All extrapyramidal tracts descend through the ?? of the brainstem
= tegmentum
The corticospinal tracts descend through the ?? of the brainstem
= base
All brainstem nuclei (apart from pontine and tectal nuclei) are located in the ?? of the brainstem
= pons
List the site of decussation and whether the CORTICOSPINAL PATHWAY stays ipsilateral
decussation site= pyramidal decussation
stays ipsilateral= contralateral
List the site of decussation and whether the CORTICONUCLEAR PATHWAY stays ipsilateral
decussation site= most pons, some midbrain
stays ipsilateral= mostly bilateral
List the site of decussation and whether the TECTOSPINAL PATHWAY stays ipsilateral
decussation site= midbrain
stays ipsilateral= bilateral
List the site of decussation and whether the RUBROSPINAL PATHWAY stays ipsilateral
decussation site= midbrain
stays ipsilateral= contralateral
List the site of decussation and whether the RETICULOSPINAL PATHWAY stays ipsilateral
decussation site= some in spinal cord
stays ipsilateral= mostly ipsilateral, some bilateral
List the site of decussation and whether the LATERAL VESTIBULOSPINAL PATHWAY stays ipsilateral
decussation site= NA
stays ipsilateral= ipsilateral
List the site of decussation and whether the MEDIAL VESTIBULOSPINAL PATHWAY stays ipsilateral
decussation site= cervical spinal cord
stays ipsilateral= bilateral
Describe the following of the Corticonuclear pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Primary motor cortex (cerebral hemispheres)
b) Lower Motor Neurons of cranial nerve nuclei in brainstem
c) brainstem
d) Conscious motor control of skeletal muscles
Describe the following of the Lateral Corticospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Primary motor cortex (cerebral hemispheres)
b) Lower Motor Neurons of anterior grey horns of the spinal cord
c) Pyramids of medulla oblongata
d) Conscious motor control of skeletal muscles
Describe the following of the Medial Corticospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Primary motor cortex (cerebral hemispheres)
b) Lower Motor Neurons of anterior grey horns of the spinal cord
c) Level of lower motor neuron
d) Conscious motor control of skeletal muscles
Describe the following of the Vestibulospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Vestibular nuclei (at the border of the pons and medulla oblongata)
b) Lower Motor Neurons of anterior grey horns of the spinal cord
c) None
(uncrossed)
d) Subconscious regulation of balance and muscle tone
Describe the following of the Tectospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Superior Colliculus
b) Lower Motor Neurons of anterior grey horns of cervical spinal cord
c) Brainstem
d) Subconscious regulation of eye, head, neck and upper limb position in response to visual and auditory stimuli
Describe the following of the Reticulospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Reticular Formation
b) Lower Motor Neurons of anterior grey horns of the spinal cord
c) None
(uncrossed)
d) Subconscious regulation of reflex activity
Describe the following of the Rubrospinal pathway:
a) origin (location of UMN)
b) destination
c) site of decussation
d) function
a) Red nuclei
b) Lower Motor Neurons of anterior grey horns of the spinal cord
c) Brainstem
d) Subconscious regulation of upper limb muscle tone and movement
Describe the 8 step process of the Corticospinal Pathway
- Primary motor, premotor and supplementary and primary sensory cortices
- Posterior limb of internal capsule
- Corticospinal neurons keep descending through the posterior limb of the internal capsule
- Descend through the mid portion of the crus cerebri
- Split up slightly as they travel through the base of the pons
- Descend through the medulla to the pyramids of the medulla
- Decussation at the caudal pons:
- 90% decussate and descend through the lateral funiculus of the spinal tract (lateral corticospinal tract)
- 10% remain ipsilateral and descend in the anterior column, either side of the ventral median fissure (anterior corticospinal tract) - When they get to the desired spinal level, they will synapse directly or via an interneuron to the alpha motor neurone with the cell body in the ventral horn and then out to the skeletal muscle to get movement
Describe the 4 step process of the Corticonuclear (Corticobulbar) Pathway
- Primary motor, premotor and supplementary and primary sensory cortices
- Posterior limb of internal capsule
- Corticonuclear neurons are in the very anterior posterior limb or near the genu of the internal capsule
- Corticonuclear neurons go off to different motor nuclei
Discuss the lateral corticospinal tract
- innervates the lateral motor neuron pool in the ventral horn of the spinal cord, therefore innervates mostly distal muscles of the limbs
- controls more discrete movements because it is responsible for the distal muscles
- tract terminates at the cervical/thoracic levels (brachial plexus) and lumbrosacral levels (lumbar and sacral plexuses) to innervate upper and lower limbs
- most fibres originate from the motor cortex and terminate in the ventral horn of the spinal cord (alpha neurons)
Describe the pathway of the lateral corticospinal tract (9 steps)
- medulla
- inferior olivary nucleus
- olive
- corticospinal tract
- pyramid
- decussation of the lateral corticospinal tract
- lateral corticospinal tract (90%)
- lateral funiculus of the spinal cord
- ventral horn of the spinal cord
Discuss the anterior corticospinal tract
- innervates the median motor neurone pool in the ventral horn of the spinal cord, therefore innervates the proximal limb and axial muscles
- do not decussate at the pyramidal decussation
- decussates at different spinal cord levels
Describe the pathway of the anterior corticospinal tract (8 steps)
- medulla
- corticospinal tract
- pyramid
- pyramidal decussation
- anterior corticospinal tract (10%)
- anterior funiculus of the spinal cord
- ventral horn of spinal cord
- decussation of the anterior corticospinal tract
Describe the pathway of the Reticulospinal tract (5 steps)
- Gains input mainly from the motor cortex which sends the motor plan/goal of the movement to the reticulospinal tract. Also gains input from the cerebellum, the basal ganglia, the vestibulospinal tract (collateral) and tectospinal tract (collateral)
- Medial reticulospinal tract originates in the medial column of the pontine reticular formation
- Lateral reticulospinal tract originates in the medial column of the medullary reticular formation
- Descend mainly ipsilaterally but also some bilaterally to the ventral horn of all levels of the spinal cord
- Innervates muscles for upright body posture and gait control
Describe the pathway of the Vestibulospinal tract (4 steps)
- Gains input mainly from the vestibular apparatus but also from the cerebellum
- Medial vestibulospinal tract originates from the medial vestibular nucleus and lateral vestibulospinal tract originates from the lateral vestibular nucleus
- The lateral vestibulospinal tract descends ipsilaterally. The medial vestibulospinal tract descends bilaterally
- Lateral vestibulospinal tract descends to all spinal levels. Medial vestibulospinal tract descends to the cervical spinal cord to innervate neck muscles
Describe the pathway of the Tectospinal tract (4 steps)
- Gains visual input from the retina, auditory input from the inferior colliculi and sensory input from the spinal cord (dorsal and anterolateral system)
- Originates from the superior colliculi in the tectum
- Immediately decussates into the tegmentum in the midbrain level. However, some remain ipsilateral to inhibit the muscles on one side while the contralateral muscles are excited (important for reflex). Therefore, it acts bilaterally
- Descends and terminates at alpha and gamma motoneurons in the cervical spinal cord to innervate the neck and shoulder muscles
Describe the pathway of the Rubrospinal tract (5 steps)
- Gains input from the corticomotor tracts
- Tract originates from the red nucleus
- Decussates immediately in the tegmentum of the midbrain
- Descends contra laterally through the lateral column of the spinal cord to the cervical level, accompanying the lateral corticospinal tract
- Innervates the flexor muscles of the upper limb. Does NOT innervate neck muscles because it travels with the lateral corticospinal tract which innervates upper limbs
Describe the 3 column weight transmission in the lower cervical spine
- from C2 and below there are 3 pathways that share the load transfer
36%= through vertebral bodies and discs
2 x 32%= through zygapophyseal joints on the lateral sides of the vertebral column
Describe the cortical origin of the corticospinal pathways
40% from primary motor cortex
40% from the supplementary and premotor cortices
20% from the primary sensory cortex
What is the primary cause of thoracic kyphosis?
= wedge shaped vertebrae
What limits movement in the thoracic region?
= low disc to vertebral body height ratio
= rib cage
What limits flexion and extension in the thoracic region?
= tall, coronal superior articular processes
= long, inferior sloping spinous processes also limit extension
Describe the coupling movements in the thoracic spine
- in the upper thoracic spine: lateral flexion and rotation ipsilateral coupling
- when the inferior articular process of the superior vertebra slides inferiorly it also moves posteriorly (like mid/lower cervical spine)
- rotation refers to the direction that the anterior vertebral body turns towards
List the 5 things that cause Lumbar Lordosis
- Sacrum is tilted anteriorly
- L5/S1 intervertebral disc is wedge shaped (taller anteriorly)
- L5 vertebra similarly wedge shaped
- Superior vertebra incline slightly backwards
- L1 aligned vertically over S1
Describe the iliolumbar ligament and what it resists
- between transverse processes of L5 to ileum
- resists L5 slipping anteriorly off sacrum
- resist all directions of movement of L5 on the sacrum
What features stabilise the L5/S1 articulation?
- zygapophyseal joint
- iliolumbar ligament
- longitudinal ligaments
- intervertebral disc
- muscles
What 3 things limit flexion in the lumbar vertebral column
- Impaction of anterior articular processes
- Tension in:
- zygapophysial joint capsules
- supraspinous ligament
- interspinous ligament
- ligamentum flavum
- posterior annulus fibrosis - Compression of:
- anterior annulus fibrosis
What 2 things limit extension in the lumbar vertebral column
- Compression of interspinous ligament
2. Impaction of spinous processes or inferior articular process with lamina below (tension in anterior annulus fibrosis)
What 3 things limit axial rotation in the lumbar vertebral column
- Impaction of zygapophysial joints
- Tension in posterior ligaments
- Tension in annulus fibrosus
List and describe the 4 components of Basal Ganglia
- Striatum (STR) = caudate nucleus and putamen
- Globus Pallidus (external=GPe) and (internal=GPi)
- Subthalamic Nucleus (STN)
- Substantia Nigra (pars compacta= Sac) and (pars reticulata= SNr)
What artery supplies most parts of the basal ganglia
= middle cerebral artery
List and discuss the functions of the basal ganglia
- participate in control of voluntary movement via selection of motor plans
- facilitate voluntary (desired) motor programs
- suppress unwanted (competing) motor programs
- damage results in movement disorders
What resists anterior translation of the superior vertebrae on the inferior vertebrae
= the alignment of vertical spinous processes in the coronal plane
How does the Interspinous ligament resist posterior translation of the superior vertebrae on the inferior vertebrae
= the interspinous ligament run anterior/inferiorly from the superior spinous process, thus resisting posterior translation of superior vertebrae
How does the intervertebral disc resist posterior translation of the superior vertebrae on the inferior vertebrae
= the alternate fibres of consecutive concentric annulus fibrosus rings means that 50% of the fibres (running anterior/inferiorly) resist each other
How is torsion resisted within a vertebra
= annulus fibrosus aligned at 45 degrees and therefore 50% tighten in one direction
How is axial rotation of the superior vertebra on the inferior vertebra resisted
= subsequent concentric layers of the annulus fibrosus, superior facets are aligned in the sagittal plane, impact of articular processes provides physical resistance to axial rotation
= L-shaped zygapophyseal joints also resist
Why are the articular facets so large compared with those of other vertebrae?
Because C1 articulates with occipital bone of skull
Why is it so important to diagnose and treat a fracture of the dens?
= fracture can lead to poor vascularity
Describe the transverse ligament of atlas
attached to the medial surfaces of the lateral Masses of the atlas (C1)
passes posteriorly to the dens
Describe the alar ligaments
these arise from the posterolateral aspect of the dens of the axis and attach to the margins of the foramen magnum
Which vessel does the vertebral artery arise from?
- vertebral artery is inferior to basilar artery
- vertebral artery is superior to subclavian artery
Explain the bilateral and unilateral movements of the head and neck when the sternocleidomastoid contracts
Bilaterally: - upper cervical extension - lower cervical flexion Unilaterally: - ipsilateral lateral flexion - contralateral axial rotation
Explain the bilateral and unilateral movements of the head and neck when the upper fibres of trapezius contracts
Bilaterally: - extension of head and neck Unilaterally: - ipsilateral lateral flexion of head and neck - contralateral rotation
Explain the bilateral and unilateral movements of the head and neck when the levator scapulae contracts
Bilaterally: - neck extension Unilaterally: - ipsilateral lateral flexion of neck - ipsilateral rotation of neck
What is the action of longus capitis?
- flexion of head and upper cervical spine
What is the action of longus Colli (cervicis)?
- cervical flexion
What are the bilateral and unilateral actions of the scalene muscles
Bilaterally:
- neck flexion
Unilaterally:
- ipsilateral lateral flexion
What movements occur at C0/C1?
flexion and extension
What movements occur at C1/C2?
axial rotation
Name the 4 Sub-Occipital muscles
- Rectus capitis posterior major
- Rectus capitis posterior minor
- Obliquus capitis superior
- Obliquus capitis inferior
What is the function of segmental muscles?
= proprioceptive functions
How does the structure of Longissimus pars thoracis and iliocostalis lumborum pars thoracis relate to their function
> Prime extensors of the thoracolumbar spine
- vertical line of action
- large PCSA
- large posterior moment arm
- crosses many segments
Unilateral action: LF (iliocostalis lumborum is better)
Bilateral action: E
iliocostalis pars thoracis also derotates
How does the structure of longissimus thoracis pars lumborum and iliocostalis lumborum pars lumborum relate to their function
> Unilateral action:
-vertical line of action lateral to axis=LF
Bilateral action:
-vertical line of action posterior to axis=E
-horizontal line of action=posterior shear
Other notes:
- deeper than pars thoracis
- attaches to lumbar transverse processes superiorly
How does the structure of Multifidus relate to its function
> Lateral view:
- vertical line of action posterior to axis= E and maintains lumbar lordosis
- no translation results from contraction
Posterior view:
- small horizontal component which could assist with rotation
- abdominals produce F and R: multifidus cancels out F with E
Which produce posterior shear forces on the lumbar motion segment? Is it a good thing or bad thing?
= LT and IL pars lumborum
= good because it resists anterior translation
Which muscles are the primary extensors of the thoracic and lumbar spine
= LT and IL pars thoracis
Which muscles are the primary flexors of the thoracic and lumbar spine
= IL pars thoracis
Which muscles are the primary rotators of the thoracic and lumbar spine
= external and internal obliquus; with assistance from multifidus
Which muscles are the primary lateral flexors of the thoracic and lumbar spine
= abdominals
Name the innervated structures of the Sympathetic Trunk and Grey Rami Communicantes and the nerve structure it arises from
Nerve structure= anterior vertebral plexus Innervated structures: - anterior outer annulus fibrosus - anterior longitudinal ligament - anterior vertebral periosteum - vertebrae and blood vessels
Name the innervated structures of the Sinuvertebral Nerve off Ventral Rami and the nerve structure it arises from
Nerve structure= posterior vertebral plexus
Innervated structures:
- posterior outer annulus fibrosus
- posterior longitudinal ligament
- posterior vertebral periosteum
- anterior and ventral/lateral dura and nerve root sleeves
- vertebrae and blood vessels
Name the innervated structures of the Dorsal Rami and the nerve structure it arises from
Nerve Structure= medial branch
Innervated structures:
- zygapophyseal joint above and below
- muscles: interspinales, rotatores, multifidus and semispinalis
Nerve Structure= intermediate branch
Innervated structures:
- longissimus
Nerve Structure= lateral branch
Innervated structures:
- erector spinae
How does the intervertebral disc height to vertebral body height ratio effect the movement/s available at a motion segment?
- if this ratio is low= lower mobility/greater stability
- increased separation between vertebral bodies= increased motion
How does the height of the superior articular process effect the movement/s available at a motion segment?
- flexion= anterior rotation + anterior translation
- during anterior rotation, the inferior articular processes must life over the superior articular process = difficult for high articular processes
- during anterior translation, a high superior articular process blocks the inferior articular process
= therefore, flexion is limited
How does zygapophyseal joint orientation in each spinal section effect the movement/s available at a motion segment?
Cervical:
- transverse plane
- allows all movements
Thoracic:
- coronal plane
- resists anterior translation and F/E
- allows axial rotation and LF
Lumbar:
- sagittal plane
- resists axial rotation
- allows F/E and LF
How do the ligaments effect the movement/s available at a motion segment?
- when ligaments tighten, the resist excessive movement
List all (8) the limitations to FLEXION in the vertebral column
- tall superior articular processes blocking anterior translation of the superior vertebra (e.g. thoracic)
- Zygapophyseal joints aligned in the coronal plane (e.g. thoracic)
- Compression in the anterior intervertebral disc
- Tension in the posterior annulus fibrosis fibres of the intervertebral disc
- Tension in the PLL, ligament flavour, supraspinous ligament and ligamentum nuchae
- Tension in the zygapophyseal joint capsules
- Tension in the posterior muscles/fascia
- Ribs
List all (5) the limitations to EXTENSION in the vertebral column
- Zygapophyseal joints aligned in the coronal plane
- Compression in the posterior intervertebral disc
- Tension in the anterior annulus fibrosis fibres
- Tension in the anterior ligaments (ALL)
- Tension in anterior muscles
List all (5) the limitations to LATERAL FLEXION in the vertebral column
- Compression of ipsilateral lateral intervertebral discs
- Tension of contralateral lateral annulus fibrosis fibres
- Tension of contralateral ligaments (transverse ligaments)
- Tension of contralateral zygapophyseal joints
- Tension of contralateral muscles
List all (3) the limitations to ROTATION in the vertebral column
- High superior articular processes block anterior rotation
- Zygapophyseal joints aligned in sagittal plane
- 50% of fibres tensing/resisting (fibres running in same direction)
In general, which region of the vertebral column is the most mobile?
= cervical
What structures of the intervertebral motion segment determine the type and amount of moment in the Mid/Lower Cervical Spine?
- zygapophyseal joints aligned in almost coronal plane; allowing all movements
What structures of the intervertebral motion segment determine the type and amount of moment in the Mid Thoracic Spine?
- zygapophyseal joints aligned in the coronal plane allowing axial rotation and lateral flexion and resisting anterior translation and F/E
- tall superior articular processes resist flexion in this region
- long, inferiorly facing spinous processes resist extension
- small, intervertebral disc height, limiting movement
What structures of the intervertebral motion segment determine the type and amount of moment in the Mid Lumbar Spine?
- zygapophyseal joints aligned in the sagittal plane, allowing F/E and lateral flexion and resisting axial rotation
- large intervertebral disc height, allowing movement
Which regions of the brain do the vertebral arteries supply?
- posterior regions of brain
- cerebellum
- cervical spinal cord
- brainstem
Which of the 4 sub-occipital muscles are aligned best to produce rotation of the head and C1 on C2?
= obliquus capitis inferior
Is the amygdala part of the basal ganglia ‘functionally’? Which system is it part of?
- the amygdala is not part of the basal ganglia functionally; it is however, in the same region anatomically
- the amygdala is part of the limbic system
Where is the caudate nucleus located? Is it present in all parts of the space it occupies
- the caudate nucleus is located on the lateral walls of the lateral ventricle (anterior and posterior horns as well as that of the body, but not in the posterior horn)
What are the main functions of basal ganglia?
- controlling voluntary movement and facilitating voluntary movements and inhibiting unwanted movements
- modulate functions of the pyramidal and extrapyramidal pathways
What is the major site of input into the basal ganglia?
- motor cortices (prefrontal cortex)
What is the major site of output from the basal ganglia
- motor cortices (supplementary motor cortex)
What connects the caudate nucleus and putamen
= striatal grey matter cell bridges
What separates the lentiform nucleus and the thalamus
= internal capsule
Why has the structure of the caudate nucleus evolved as a C-form shape?
= to evolve around the lateral ventricle
Which neuronal receptors are mainly affected by Huntington’s disease
= selective degeneration of D2- receptor neurons
What pathological observation can be seen in the brain of a person with Huntington’s disease
= lesion in the striatum (primarily caudate nucleus)
Describe the symptoms of Huntington’s disease
- excessive involuntary movement
- chorea
What is Parkinson’s disease characterised by?
- the degeneration of the SNc which leads by depletion of dopamine in the striatum
If lack of dopamine in striatum causes Parkinson’s disease symptoms, what is the major treatment option for Parkinson’s disease patients
- medication that stimulates production of dopamine (short-term)
- deep brain stimulation can be used to decrease the inhibition via the indirect pathway
Does the substantial nigra appear dark in Parkinson’s disease patients
= No, in Parkinson’s disease patients the substantial nigra becomes less visible (lighter)
How does the basal ganglia work with the prefrontal cortex
- higher order decision making
How does the basal ganglia work with the supplementary motor cortex
- implicated in initiating actions that are guided by internal cues, such as the performance of a sequence of movements from memory (as opposed to movements guided by external cues)
How does the basal ganglia work with the primary motor cortex
- activates muscles related to appropriate motor program
What is the function of the Direct Pathway with input from SNc
- initiates and promotes voluntary (desired) movements
- input from the SNc further excites the direct pathways, facilitating movements initiated in the motor cortex
What is the function of the Indirect Pathway with input from SNc
- inhibits and suppresses unwanted (competing) motor plans
- input from the SNc inhibits indirect pathways, facilitating movements initiated in the motor cortex
Describe the diaphragm including:
a) attachments
b) openings
c) innervation
- the diaphragm is dome shaped with a central tendon
- the right side is higher than the left
a) attachments=
L1, 2, 3 and lower 6 costal cartilages and ribs
superiorly is the central tendon
b) openings= - inferior vena cava (T8)
- oesophagus (T10)
- descending aorta pass behind (T12)
c) innervation=
phrenic nerve C3, 4, 5
Describe the primary muscles of the pelvic floor and its role
- levator ani and coccygeus
- support contents of the pelvic cavity
Name the attachments of psoas major
anterior= from vertebral bodies/ intervertebral discs of T12/lumbar vertebrae posterior= from transverse processes of T12/lumbar vertebrae insertion= less trochanter of femur
Discuss the actions of psoas major
- acts primarily as a hip flexor
- vertical orientation and close to joint axis
- therefore, when you recruit/use psoas major to flex hip it automatically compresses the lumbar spine motion segments leading to stability
- also has small moment arms for flexion or extension
Name the attachments of Quadratus lumborum
12th rib, lumbar transverse processes and posterior iliac crest
Discuss the action of Quadratus lumborum
- acts primarily as a stabiliser when contracting bilaterally
- has minimal moment arms for sagittal movements (F/E)
- has large moment arms for coronal movements (LF)
What is the innervation of Quadratus lumborum
= thoracolumbar ventral rami
Name the attachments of rectus abdominis
superior= xyphoid process and adjacent rib cartilages inferior= pubic crest and symphysis
What is the innervation of rectus abdominis
= T7 to 12 ventral rami
What is the action of rectus abdominis
= prime mover of trunk flexion
Name the attachments of Transversus abdominis
posterior= thoracolumbar fascia superior= internal aspect of lower ribs/cartilages inferior= iliac crest and inguinal ligament insertion= linea alba
What is the innervation of Transversus abdominis
= T7 to L1 ventral rami
What is the action of Transversus abdominis
= increase intra-abdominal pressure
Name the attachments of Internal Oblique Abdominal
posterior= thoracolumbar fascia inferior= anterolateral iliac crest and inguinal ligament superior= lower 4 ribs and cartilages anterior= linea alba via aponeurosis
What is the innervation of Internal Oblique Abdominal
= T7 to L1 ventral rami
What are the actions of Internal Oblique Abdominal
bilaterally= trunk flexion and increase intra-abdominal pressure unilaterally= ipsilateral rotation and LF
Name the attachments of External Oblique Abdominal
superior= external surface of posterior lower 8 ribs
inferior= linea alba via aponeurosis and anterolateral iliac crest
free posterior border
What is the innervation of External Oblique Abdominal
= T7 to 12 ventral rami
What are the action of External Oblique Abdominal
bilaterally= trunk flexion and increase intra-abdominal pressure unilaterally= contralateral rotation and ipsilateral LF
What is the rectus sheath
= layering of aponeuroses of the anterolateral abdominal muscles
What makes up the upper 3/4 of the rectus sheath
anterior= aponeuroses of:
- external oblique abdominal
- 1/2 of internal oblique abdominal
posterior= aponeuroses of:
- 1/2 of internal oblique abdominal
- transversus abdominis
What makes up the lower 1/4; below the arcuate line of the rectus sheath
anterior= aponeuroses posterior= transversalis fascia
Describe the anterior and middle layers of the Thoracolumbar Fascia
- attach to lumbar transverse processes
- envelope Quadratus lumborum
- posterior attachment for transversus abdominis and internal oblique abdominal
Describe the posterior layer of Thoracolumbar Fascia
- attaches to T/L/S spinous processes
- encloses erector spinae group
- laterally fuses with middle layer
- blends with:
>erector spinae aponeurosis (caudal tendons of LT and IL pars thoracis)
> latissimus dorsi
> gluteus maximus
Discuss how muscular co-contraction can ‘stiffen’ the vertebral motion segment
- contraction of muscles that act across vertebral motion segments imposes compression across that joint making it more difficult to move the joint
therefore, increasing stability
Discuss the role of thoracolumbar fascia attachments in stability
- extensive muscular attachments into the thoracolumbar fascia which, in turn, attach to lumbar transverse and spinous process
= possible contributions to motion segment stability
Discuss the function of the diaphragm in Respiration and its relation to stability
= contraction of diaphragm pulls central tendon inferiorly
- increases intra-thoracic volume/decreases intra-abdominal volume
- if abdominal muscles are relaxed = abdominal viscera pushed anteriorly
- if abdominal muscles are contracted = increase intra-abdominal pressure
Discuss the function of the diaphragm in Trunk Postural Control and its relation to stability
- standing at rest= diaphragm relaxed during expiration
- sitting/standing and repetitive, fast UL movements= diaphragm active throughout expiration
- this supports the argument that diaphragm contraction is related to trunk control
- postural activity of diaphragm changes when respiratory drive increases
Discuss how increased intra-abdominal pressure increases the stiffness of the lumbar spine
studies show that:
increased intra-abdominal pressure leads to increased extensor moment and increased force required to flex the lumbar spine, therefore, it can be concluded that increased intra-abdominal pressure contributes to spinal stability by stiffening the lumbar spine
How does activity in the pelvic floor muscles relate to trunk/spinal stability?
- the pelvic floor resists inferior protrusion when intra-abdominal pressure increases
- intra-abdominal pressure stabilises the vertebral column by creating force around the vertebral column
Is the Thoracolumbar Fascia different to the erector spinae aponeurosis
YES
- they blend together but are different structures
- erector spinae aponeurosis= caudal tendon of LT and IL pars thoracis
What are the functions of the Thoracolumbar Fascia
- to provide stability to the spine when tensed (caused by muscles contracting and bulging)
What is the most powerful flexor of the thoracolumbar spine and why?
= rectus abdominis
- has the largest moment arm, PCSA and vertical alignment
Which are the most powerful rotators of the thoracolumbar spine and why?
= internal and external oblique
- the most effective rotator is the unilateral contraction of the internal oblique and the external oblique on the opposite side
What muscles contribute to RIGHT TRUNK ROTATION
- contraction of the right internal oblique
- contraction of the left external oblique
How can increasing intra-abdominal pressure contribute to stability of the lumbar spine?
- increased IAP= more stability and support for the trunk
- results in increased extensor moment and increased force required to flex the spine
- when IAP increases the cavity will want to expand to compensate (prevented by muscles) - muscles have to contract in order to increase IAP
- when IAP increases, it creates force surrounding the vertebral column, causing it to stiffen
How does abdominal muscle co-contraction contribute to stability of the lumbar spine?
- one muscle contracting bilaterally or a muscle and its antagonist contracting simultaneously
- compresses the lumbar spine, resulting in stability
How does Thoracolumbar Fascia (abdominopelvic muscle attachments) contribute to stability of the lumbar spine?
- when certain muscles contract and swell, the surrounding fascia tenses, increasing stability by resisting flexion or producing extensor moment
e. g. - when the Quadratus lumborum contracts, the middle and anterior thoracolumbar fascia tenses
- thoracolumbar fascia connects to points on the vertebral column (transverse and spinous process). Therefore, when the thoracolumbar fascia tenses, it pulls the vertebral column inferiorly, compressing and stabilising it
What artery supplies the superior half of the cerebellum?
= one superior cerebellar artery
What arteries supply the inferior half of the cerebellum?
= inferior anterior and inferior posterior cerebellar artery
What are the superior and inferior anterior cerebellar arteries a branch of?
= basilar artery
What is the inferior posterior cerebellar artery a branch of?
= vertebral artery
List the 4 major cerebellar functions?
- Regulates and coordinates voluntary movements (indirectly via influencing descending pathways [pyramidal and extrapyramidal])
- Maintains balance and posture
- Involved in motor learning (trial and error based learning)
- Controls ipsilateral side of body (whereas cerebrum controls contralateral side of body)
List and describe the 3 vestibular reflexes
- Vestibulospinal reflex:
- keeps body in centre of gravity by maintaining muscle tone and activating antigravity muscles (=function of lateral vestibulospinal tract) - Vestibulocervical reflex:
- stabilises position of head (= function of medial vestibulospinal tract) - Vestibulo-ocular reflex:
- stabilises gaze during head movements (= function of medial vestibulospinal nucleus)
What does the horizontal fissure of the cerebellum separate?
= the superior and inferior cerebellum for bloody supply
Explain why the molecular layer of the cortex is exceptionally wide (thicker) than the white matter
= because the cerebellum does not commissural or association fibres; therefore, not a lot of white matter is needed.
Thus, the molecular layer is there to connect the cortex and the cerebellar nuclei
Explain the unique structure of the Purkinje cells and their orientation in the cortex:
- flat
- large dendrite trees
- stacked beside each other with no overlapping
Explain the orientation of the parallel fibres of granule cells in the cortex
- travel parallel to each other
- travel perpendicular to Purkinje cells so they can touch as many Purkinje fibres as possible
Describe Climbing Fibres
- go to Purkinje cells
- only from the inferior olivary nucleus
- inhibitory
Describe Mossy Fibres
- go to granular cells
- from everywhere
Discuss each of the following for the Cerebrocerebellum
a) structures
b) connectivity (relevant fibres)
c) function
a) lateral hemisphere, dentate nucleus
b)
afferent fibres= contralateral motor cortex (premotor)
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
Discuss each of the following for the Spinocerebellum
a) structures
b) connectivity (relevant fibres)
c) function
a) anterior lobe, vermis, intermediate hemisphere, fastigial and interposed (globose and emboliform) nuclei
b) spinal cord:
- posterior spinocerebellum
- cuneocerebellar
c) regulates muscle tone, posture and balance (with medial motor pathways)
Discuss each of the following for the Vestibulocerebellum
a) structures
b) connectivity (relevant fibres)
c) function
a) flocculonodular lobe, fastigial nuclei
b) vestibular nuclei and nerve
c) influence vestibular nuclei for error correction of the vestibulocervical, vestibulospinal and vestibulo-ocular reflexes
Describe the layers of the cerebellar cortex via a labelled diagram
- molecular cell layer
- purkinje cell layer
- granular cell layer
- White matter
What is the role of Clarke’s nucleus?
= integrates afferent information from proprioceptors and skin receptors
List the 5 sub-system Anterolateral pathways, where they travel and their main role
- Spinothalamic pathway
- travels to VPL of thalamus
- controls response to main - Spinomesencephalic pathway
- travels to PAG
- controls descending pain modulation - Spinoreticular pathway
- travels to reticular formation
- controls arousal/attention - Spinobulbar pathway
- travels to brainstem nuclei
- controls adaptive responses - Spinohypothalamic pathways
- travels to hypothalamus
- controls autonomic response to touch
List the steps of the Posterior spinocerebellar tract and briefly describe this tract
- is an ascending pathway (spinocerebellar tract)
- for fibres entering C8 and below
- for LL
- Proprioceptive info muscle and skin enter spinal cord
- Travels through fasciculus gracilis
- When reach L3; synapse in Clarke’s nucleus
- Clarke’s nucleus extends from L3 to C8
- Fibres then travel in posterior spinocerebellar tract through spinal cord and brainstem
- Fibres then travel through inferior cerebellar peduncle to ipsilateral cerebellum (ant. lobe and vermis)
List the steps of the cuneocerebellar tract and briefly describe this tract
- is an ascending pathway (spinocerebellar tract)
- for fibres entering C7 and above
- for UL
- Muscle and skin fibres enter spinal cord above C8
- Travel through fasciculus cuneatus to rostral medulla
- Fibres then synapse in accessory cuneate nucleus
- Then travel through inferior cerebellar peduncle to ipsilateral cerebellum (ant. lobe, vermis and intermediate region)
