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)