Lower Limb 2 Flashcards
(225 cards)
0
Q
3 muscular compartments of the thigh
A
Anterior extensor, posterior flexor, medial adductor
1
Q
Hamstring muscles
A
Semimembranosus, semitendinosus and long head of biceps femoris
2
Q
Common proximal attachment and nerve supply of hamstrings
A
Ischial tuberosity and tibial nerve (L5-S2)
3
Q
Distal insertion of semitendinosus
A
Pes anserinus - proximal tibia medial to tibial tuberosity
4
Q
Distal attachment of semimembranosus
A
Posterior medial condyle of tibia
5
Q
Distal attachment of long head of biceps femoris
A
Head of fibula and lateral condyle of tibia
6
Q
Attachments and innervation of short head of biceps femoris
A
Lateral linea aspera and lateral supracondylar ridge of femur - head of fibula and lateral condyle of tibia
Common peroneal/fibular nerve L5-S2
7
Q
Function of hamstrings at the hip
A
Extend hip when trunk is fixed
8
Q
Function of hamstrings at the knee
A
ST+SM flex knee and medially rotate lower leg when knee is bent.
Long and short head of BF flex knee and laterally rotate lower leg when knee is bent.
9
Q
Nerve supply and proximal attachment of hamstring part of adductor Magnus
A
Tibial nerve.
Ischial tuberosity
10
Q
Angle of inclination
A
Angle between neck and shaft of femur-determine obliquity of the femur. Usually 126 degrees
11
Q
Q angle
A
Angle between femur and tibia. Usually 15 degrees. Allows knee to be positioned underneath hip and distributes weight evenly across the knee.
12
Q
Genu varum/ bow leg
A
Q angle
13
Q
Genu valgum/ knock knee
A
Q angle> 17 degrees
Tibia abducted with respect to femur
Lateral sided osteoarthritis
14
Q
Attachments of anterior cruciate ligament
A
Anterior intercondylar region of tibia - travels superoposteriorly - lateral femoral condyle
15
Q
Attachments of posterior cruciate ligament
A
Posterior intercondylar region of tibia - travels superoanteriorly - medial femoral condyle
16
Q
Function of posterior cruciate ligament
A
- Prevent posterior displacement of tibia
- Prevents hyper flexion of the knee
- Main stabiliser of the flexed knee when weight bearing e.g walking downhill
17
Q
Function of anterior cruciate ligament
A
- Prevents anterior displacement of tibia
2. Prevents hyper extension
18
Q
Function of menisci cartilage
A
- Increase joint congruency
- Distribute weight evenly
- Shock absorption
- Aid lubrication by facilitating movement of synovial fluid
- Assist in locking mechanism
19
Q
Function of articularis genu
A
Part of Vastus intermedius
Holds the large suprapatellar bursa in place
20
Q
How to test for suprapatellar bursitis
A
Patellar tap test.
Push any fluid in suprapatellar bursa into synovial cavity using hands.
Tap patella - if bounces/floats then test is indicative of an effusion
21
Q
What is locking of the knee
A
As knee joint approaches full extension femur undergoes a few degrees of medial rotation on the tibia.
V stable position- allows thigh muscles to relax.
22
Q
How to unlock the knee joint
A
Popliteus muscle laterally rotates the femur
23
Q
What is the unhappy triad of knee injuries
A
Torn anterior cruciate ligament
Torn tibial/medial collateral ligament
Torn medial meniscus
Caused by excessive lateral twisting of the flexed knee/ blow to lateral side of extended knee
24
What are denticulate ligaments
Lateral extensions of the pia mater
| anchors the spinal cord in the vertebral canal
25
At what level does the spinal cord terminate in an adult
L1/L2 as the conus medullar is
26
What is the filum terminale and where does it terminate
It is an extension of the pia mater starting from the conus medullaris to S2 (internum) and to coccyx (externum)
Gives longitudinal support to the spinal cord
27
What is the Cauda equina (horses tail)
Dorsal and ventral roots of lower lumbar, sacral and coccygeal segmental spinal nerves
28
How is the Cauda Equina formed
In a fetus the spinal cord terminates at the end of the vertebral canal (at coccyx) and then regresses to L1/L2 as the back straightens in an adult (L3 in a child)
The Spinal nerve roots have already left their vertebra into intervertebral foramen so are stretched into the caudal equina
29
At which levels of the spinal cord is the lateral grey horn present in a cross section
T1-L2 (sympathetic)
| S2-S4 (parasympathetic)
30
In which direction of the spinal cord does white matter increase
Increases as it ascends
Largest at cervical vertebra
Because there is sequential addition of afferent axons to the cord as it ascends, and because there are fewer descending axons as it approaches the sacral cord.
31
Where in the spinal cord is the ventral grey horn largest
VGH enlarged where motor fibres to limbs arise
Cervical enlargement: C3-T2
Lumbosacral enlargement: L1-S2
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2 groups of somaesthetic modalities
1. Essential to survival: Pain, temperature, some touch and pressure. Slow conduction, thin/unmyelinated fibres
2. Increase detail: Discriminative touch and proprioception. Fast conduction, heavily myelinated large diameter fibres
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Where do cell bodies of 1st order neurones reside
Dorsal root ganglion (PNS)
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Where do cell bodies of 2nd order neurones reside
Ipsilateral grey matter (CNS)
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Where do cell bodies of 3rd order neurones reside
Thalamus and axons project to somato-sensory cortex through internal capsule
36
What sensations does the Spinothalamic Tract transmit
Pain, Temperature, Some touch and pressure from body
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What happens to the 1st order neurone of the STT
Cell body in DRG
Enters spinal cord and ascends 1 or 2 segments
Synapses with a 2nd order neurone in DGH
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How does the 2nd order neurone of the STT cross the midline
Passes anterior to the central canal via the ventral white commisure to enter into STT and ascend
39
What is the name of the continuation of the STT at the boundary of the medulla
Spinal/lateral lemniscus
40
Where do 2nd order neurones of the STT synapse
Ventroposterolateral nucleus in the thalamus
41
What sensations does the Dorsal column tract transmit
Proprioception and discriminative/fine touch
42
What happens to the 1st order neurone of the DCT
Cell body in DRG
Enters spinal cord and ascends in ipsilateral dorsal column
Synapses in dorsal closed medulla with 2nd order neurone in ipsilateral gracile or cuneate tubercles
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In which dorsal column does info from below T6 ascend
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Gracile Fascicle (Medial)
Gracile fascicles run through entire spinal cord segments
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In which dorsal column does info from above T6 ascend
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Cuneate Fascile (Lateral)
only present in spinal cord above T6
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How do 2nd order neurones of the DCT cross the midline
Via Internal Arcuate Fibres to medial lemniscus
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Where to 2nd order neurones of the DCT synapse
VPL on thalamus
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What info does the lateral spinothalamic tract transmit
Pain and temperature.
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What info does the anterior spinothalamic tract (or ventral spinothalamic tract) transmit
Crude touch and firm pressure.
49
In what tract is sensory information from the face carried to the thalamus
Trigeminothalamic tract
| Cranial nerves 5,7,9,10
50
What are the 3 parts of the sensory trigeminal nucleus
Mesencephalic
Chief/pontine
Spinal
51
In which part of the spinal nucleus is pain and temperature received
caudal part of spinal nucleus
52
In which part of the spinal nucleus is simple touch and pressure received
Rostral parts of spinal nucleus
53
Where are the cell bodies of 1st order neurones of the TGT that carry pain and temperature
Trigeminal ganglion then enter lateral pons
Then run caudally in (lateral) spinal tract to caudal spinal nucleus to synapse and cross midline to ascend in midline TGT
54
Where are the cell bodies of 1st order neurones of the TGT that carry simple touch and pressure
Trigeminal ganglion then enter lateral pons
Then run caudally in (lateral) spinal tract to rostral spinal nucleus to synapse and cross midline to ascend in midline TGT
55
Sensory consequences of a lesion affecting the lateral medulla
Ipsilateral facial sensory loss
| Contralateral body Sensory deficit
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Where is the spinal nucleus and spinal tract
Lateral medulla
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What sensory modality does the pontine nucleus receive
Discriminative touch on the face
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What sensory modality does the mesencephalic nucleus receive
Proprioception on the face
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Which pathway is an exception to the generalisation
| that first order cell bodies are in peripheral ganglia
Mesencephalic nucleus
60
Discriminatory touch of the face pathway
1st order neurone cell body in trigeminal ganglion
Enters lateral pons and synapses in ipsilateral pontine nucleus
Crosses midline and ascends to thalamus in TGT
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Proprioception of the face pathway
Primary neuron enters pons and ascends via mesencephalic tract (lateral to mesencephalic nucleus) to its cell body in the mesencephalic nucleus in the midbrain
Synapses with 2dary neuron just outside mesencephalic nucleus whose axon crosses midline and ascends in TGT
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What other fibres do the 1st order mesencephalic neurone contact apart from the 2nd order neurone
Contact motor neurons in Trigeminal motor nucleus e.g. V3 to muscles of mastication
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Where do 2nd order neurones in the TGT synapse
Ventro postero medial nucleus of thalamus
64
Where do Facial and vestibulocochlear cranial nerves exit the skull
Internal acoustic meatus in the petrous part of the temporal bone (hardest bone in the body)
65
The names of the 3 bony ossicles in the ear
Malleus, incus, stapes
66
What fluid does the cochlea contain
Perilymph
| Similar to extra cellular fluid so has a high proportion of Na+ ions 140mmol - sets up a membrane potential
67
Why is the middle ear a high risk area
Connected to nasopharynx – prone to infection
Connected to mastoid air cells – infection may spread to middle cranial fossa (causing encephalitis)
Internal jugular vein lies inferior – thrombosis risk
Internal carotid artery lies anterior – link to pulsatile tinnitus
Traversed by chorda tympani and facial canal – infection risk
68
What fluid does the cochlear duct (membranous sac running through the cochlea) contain
Endolymph
| Intracellular like fluid containing high conc of K+ ions
69
What 2 chambers does the cochlear duct split the cochlea into
Scala vestibuli
Scala tympani
Continuous at the apex/helicotrema
70
How is hydraulic pressure changed within the cochlea
Hydraulic pressure created in the perilymph, by the vibrations of the stapes pass to the apex via the SV.
Pass through the helicotrema and descend via the ST to the round window.
As the fluid moves around the cochlea it deforms the fluid, endolymph, in the cochlear duct.
71
What is the name of the auditory receptor and how it works
The auditory receptor is the Spiral organ (of Corti) on the basilar membrane.
The spiral organ contains hair cells with the tips embedded into the tectorial membrane.
The hair cells on the spiral organ are stimulated by the deformation of the cochlear duct by the perilymph in the surrounding SV and ST and generate an action potential to the cochlear nerve
72
The path of primary auditory neurones
Axons of bipolar neuron in spiral ganglion
Forms the cochlear nerve which becomes part of vestibulocochlear nerve (CNVIII)
Enters brainstem at cerebellopontine angle
Synapse with 2o neurons in dorsal and ventral cochlear nuclei
73
Auditory centres in the dorsal brainstem (caudal to rostral)
Cochlear nuclei
Superior olivary nucleus in pons
Inferior colliculi
Medial geniculate nucleus of thalamus
74
How do fibres pass from the cochlear nuclei to the superior olivary nucleus
Via the trapezoid body
More fibres cross than don’t cross the midline at the trapezoid body to the contralateral SON but fibres still run up the ipsilateral side to the SON
The fibres then ascend up these centres
75
How do fibres from the superior olivary nucleus pass to the inferior colliculi
Via the Lateral lemniscus (Spinothalamic fibres also run in this tract)
Some fibres may synapse, cross or bypass the inferior colliculus
76
How do fibres from the inferior colliculi pass to the Medial geniculate nucleus of the thalamus
Via the inferior brachium
| Then ascends to Heschls/superior temporal gyrus
77
What is tonotopic organisation
Different regions of the basilar membrane respond maximally to sounds of different pitch
Apex responds to Low pitch
Sound information of Low pitch projects to anteroLateral part of Heschl’s gyrus
78
In which cerebral hemisphere is the auditory association area
Left hemisphere only
| Cerebral dominance
79
Function of descending auditory pathways
To co-ordinate turning your eyes and head in the direction of the sound you are hearing
Inferior colliculus -> Reflex head and eye movement CN III, VI and VI
Superior olivary nucleus -> To stapedius via CN VII and
tensor tympani via CN V3. Prevents damage during loud noise
80
Why does a unilateral lesion have virtually no effect on hearing
As the auditory pathway is bilateral
| The ability to localise sound may be impaired
81
2 types of deafness
Sensorineural (defect in function of spiral ganglion or cochlear nerve)
Conductive (defect of sound transmission up to spiral ganglion)
82
If a subject has conductive hearing loss in one ear, in which ear will the sound be loudest
The damaged ear.
| Because hearing in normal ear is inhibited by ambient sound (auditory masking)
83
If a subject has sensorineural hearing loss in one ear, in which ear will the sound be loudest
Sound heard louder in the normal ear (sound needs to be amplified)
84
What is the function of the non-neuronal layer of the retina
Contains pigmented epithelium which absorbs light
Maintains the metabolic activity of the photoreceptors which it surrounds by the way of melanin filled microvilli.
It also provides capillaries to the photoreceptors.
85
What types of cells does the neuronal layer of the retina contain
Photoreceptors
Primary Bipolar Cells (connect photoreceptors and ganglion cells)
Secondary Ganglion cells
Interneurones: amacrine (modulate ganglion cell activity) and horizontal (at level of photoreceptors and bipolar cells)
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What cells' axons make up the optic nerve
Secondary ganglion cell axons
87
Does the optic disk contain photoreceptors
No- it is the blind spot
| Where optic nerve and vasculature exit/enter eye
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Is the retina in the PNS or the CNS
CNS- it is an outgrowth of the diencephalon
so the visual pathway occurs wholly within the CNS
Eyeball has meningeal layers
89
Where to 2nd order ganglion cells synapse with 3rd order neurones
Lateral geniculate nucleus of the thalamus via optic tract
| Then 3rd order neurones travel via optic radiation to visual cortex
90
What is papilloedema
If there is increase in ICP the CSF pressure in the increases this causes compression/swelling of optic nerve and can lead to vision loss, blurriness, increased blind spot
This increase in pressure compresses the central retinal vein preventing venous drainage from the eye
91
Which retina fibres cross over and which remain ipsilateral
Temporal retinal fibres remain in the ipsilateral optic tract
Nasal retinal fibres cross over to the contralateral optic tract via the optic chasm
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2 different visual fields
Nasal: central vision, high acuity due to many photoreceptors as it hits the centre of the retina in the temporal retina
Temporal: peripheral vision, less not as focused as central vision as it doesn’t hit centre of retina it hits nasal retina
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Retinotopic organisation
Left half of visual field goes to right hemisphere
Right half of visual field goes to left hemisphere
Upper visual field goes to lower bank of calcarine sulcus
Lower visual field goes to upper bank of calcarine sulcus
Centre of visual axis (macula) goes to occipital pole
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What is the function of the upper division of the optic radiation
Projects to the upper bank of the calcarine fissure, called the cuneus
Contains input from the superior retinal quadrants, which represents the inferior visual field quadrants
Transection causes contralateral lower quadrantanopia
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What is the function of the lower division of the optic radiation
Loops from the lateral geniculate body anteriorly (Meyer's loop), then posteriorly, to terminate in the lower bank of the calcarine sulcus, called the lingual gyrus
Contains input from the inferior retinal quadrants, which represents the superior visual field quadrants
Transection causes contralateral upper quadrantanopia
96
What is the blood supply of the optic radiation
Deep branches of the middle cerebral artery and posterior cerebral artery.
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What visual field defect leads to monocular blindness
Damage to ipsilateral optic nerve
98
What visual field defect leads to heteronymous hemianopia
Tunnel vision (loss of temporal visual fields)
Lesion at the centre of the optic chiasma
Could be pituitary tumour as pituitary gland lies directly behind optic chasm
99
What visual field defect leads to homonymous hemianopia
Lesion in optic tract opposite to eye with temporal visual field loss
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90% of the optic tract fibres go to the LGN where do the other 10% go
Take a medial root to the pre-tectal area (midbrain)
Region in front of colliculi on roof of cerebral aquaduct
Involved in pupillary light reflex
101
What is the pupillary light reflex
Ability of both pupils to respond (constrict or dilate) dependant on the level of light the retina receives.
102
Which cranial nerves and their nuclei are involved in the pupillary light reflex
Optic nerve and tract (Afferent/sensory root)
| Occulomotor (Efferent/motor root) Edinger-Westphal Nucleus
103
What 2 components make up the pupillary light reflex
Direct component = light in one eye, same pupil constricts
| Consensual component = light in one eye, other pupil constricts
104
What is the accommodation reflex
Series of changes that occur when the gaze is
transferred from a distant to near object.
Controlled by parasympathetic nervous system involves CN2 (afferent limb) and 3 (efferent limb)
105
What 3 processes occur in the accommodation reflex
Accommodation (lens becomes rounded)- ciliary muscles contract
Pupil constricts – sphincter pupillae
Ocular convergence – medial rectus
106
What happens to the eyes when moving focus from a distant to a near object
The ciliary muscle contracts making the lens more convex, shortening its focal length.
The pupil constricts in order to prevent diverging light rays from hitting the periphery of the retina and resulting in a blurred image.
107
How does the lens increase refractive power
The lens then increases its curvature to become more biconvex.
108
What is convergence of the eyes
Simultaneously demonstrate inward movement of both eyes toward each other.
This is helpful in effort to make focus on near objects clearer.
Three reactions occur simultaneously; the eyes adduct, the ciliary muscles contract, and the pupils become smaller
109
What is the action of the eye muscles to cause convergence
Contraction of the medial rectus muscles of the two eyes and relaxation of the lateral rectus muscles.
The medial rectus attaches to the medial aspect of the eye and its contraction adducts the eye.
The medial rectus is innervated by motor neurons in the oculomotor nucleus and nerve
110
4 stages of general anaesthesia
Stage 1: Analgesia
Stage 2: Excitation
Stage 3: Surgical anaesthesia (4 planes/loss of reflexes)
Stage 4: Medullary depression
111
What is the main factor that determines rate of induction and recovery of anaesthesia
Blood:gas partition coefficient
A GA with a relatively low solubility in blood has a fast onset of action and recovery e.g compare nitrous oxide with halothane
A highly fat soluble agent means a longer recovery time
112
What is the cause of malignant hyperthermia
All halogenated GAs can cause it
| Treated by administration of dantrolene – inhibits release of Ca2+ from sarcoplasmic reticulum
113
Do IV GAs work faster than inhaled GAs
Yes- can work in seconds vs minutes for inhaled GAs
normally used for induction
e.g. Thiopentol, propofol
114
Examples of Local anaesthetics
Cocaine, Lidocaine
They are weak bases that have greater activity in their protonated form (binding to voltage gated sodium channels)
Often given with vasoconstrictors e.g. adrenaline
115
Why are local anaesthetics less effective in inflamed tissue
Inflammation results in local acidosis which decreases pH of surrounding tissue.
This results in more ionized drug and insufficient amounts of drug may penetrate cell membranes because the neutral/unionised form crosses cell membranes better
116
What are lower motor neurones
Neurons that originate from the brain stem & spinal cord
Ventral grey horn, Ventral roots
Peripheral nerves to motor end plates/neuromuscular junctions
Axons of LMNs pass from the ventral grey horn of the spinal cord (CNS) and cranial nerve motor nuclei brain stem (CNS) to muscles. From the spinal cord they will run in spinal nerves and from the brain stem they will run in cranial nerves.
117
What are the symptoms of LMN lesions
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Muscle wasting
Muscle weakness/reduced power
Hypotonia
Absent tendon reflexes
Fasciculation/fibrillation
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What are the causes of LMN lesions
Peripheral nerve injury (crush or cut) e.g. ALS
| Poliomyelitis
119
What are 2 types of upper motor neurones
Corticospinal (cortex to spine - spinal nerves)
Corticobulbar (cortex to brainstem - cranial nerves)
Influence LMN activity
Modify local reflex activity
Superimpose more complex patterns of movement
120
What happens if there is damage to the corticospinal tract only
Initially: flaccid paralysis of opposite limbs, Loss of tendon reflexes
After several days to a week motor function recovers but hypertonia
Long term: Spasticity, Hyperreflexia, Left with permanent inability to carry out fine movements of hands and feet
Other pathways appear to take over most “corticospinal” functions
121
3 Descending corticospinal pathways
Reticulospinal- voluntary movement/ breathing/ consciousness
Vestibulospinal- controls posture
Rubrospinal- controls (baseline) muscle tone
122
Somatotopic representation on the anterior 2/3rds of the posterior limb of the internal capsule
Descending corticospinal/bulbar fibres pass through internal capsule
Near genu = face then arm then trunk then leg
123
What happens to descending corticospinal fibres at the pyramids
Decussation of pyramids-
85% UMN fibres cross and enter lateral corticospinal tract
15% of UMNs descend cord ipsilaterally remain in anterior/ventral CST
(cross at appropriate SC level)
If lesion above pyramid then contralateral motor deficit
124
How do UMNs synapse with LMNs
UMN cross the ventral white commisure to contact LMN in contralateral VGH
LMN extend to skeletal/striated muscle via segmental spinal nerves
125
What is the corticobulbar pathway
Synapse with LMNs in cranial nerve motor nuclei (not VGH)
Fibres originate laterally within pre-central gyrus
Innervation of LMNs is largely bilateral (unlike corticospinal
pathway), with one exception
126
Corticobulbar input to cranial nerve nuclei
Cranial nerves 3, 4, 6, 5, 7, 9, 10, 11, 12 have motor fibres
Upper face facial nerve nuclei is served bilaterally
Lower face facial nerve nuclei is served contra laterally
Hypoglossal facial nerve nuclei served contralaterally
127
What are the consequences if the LMN of the facial nerve is damaged
Ipsilateral side of face will be paralysed
128
What are the consequences if the UMN of the facial nerve is damaged e.g. stroke on the int capsule (supranuclear lesion)
Contralateral lower face paralysis (the ipsilateral side of face and contralateral upper face will all function normally as they have a bilateral innervation)
129
Examples of infra nuclear lesions/ LMN facial deficit
Bell’s palsy, tumours of cerebellopontine angle, middle ear disease, parotid tumour.
130
Which motor neurons are directly responsible for the generation of force by muscle.
Alpha motor neurones
| Gamma dont generate force
131
Where in the spinal cord is the VGH area larger
Enlarged in Lumbar and sacral vertebra
| Largest in Lumbar
132
What is a motor neurone pool
Each muscle is innervated by its own group of alpha motor neurons
The motor neuron pool extends rostro-caudally along the spinal cord axis.
133
What is segmental organisation of lower motor neurons
Motor neurons that control flexors e.g. biceps brachii lie dorsal to extensors e.g. triceps brachii.
Motor neurons that control axial/postural muscles lie medial to those controlling distal muscles.
134
Why do motor units vary in size
SMALL MOTOR UNIT
e.g. extraocular muscles of the eye – innervation ratio of 3 muscle fibres per single alpha motor neurone.
rapid precise movements requiring little strength.
MEDIUM MOTOR UNIT
e.g. Soleus muscle
LARGE MOTOR UNIT
E.g. Gastrocnemius muscle - innervation ratio ranging from 1000 – 2000 muscle fibres per alpha motor neurone.
need to be able to generate large forces for sudden change in body position.
135
What are the different types of force and fatiguability in motor units
Motor units differ in the type of muscle fibres that they innervate.
Slow motor units composed of small motor units and small ‘red’ muscle fibres that generate low force, but are resistant to fatigue (e.g. muscles involved in posture).
Fast fatigable motor units composed of large motor units and larger paler muscle fibres that generate large forces, but are easily fatigued (e.g. biceps muscle).
Fast fatigue resistant motor units intermediate type, moderate force and some fatigue. e.g. heart?
136
What are the 3 main sources of input to alpha motor neurons
Sensory inputs from peripheral proprioceptors.
Local inputs from spinal interneurons.
Descending inputs from brain upper motor neurons.
137
What are muscle spindles
The spindle is the sensory apparatus of muscle.
Lies parallel to muscle fibres- Intrafusal muscle fibres.
Detects changes in muscle length.
Contributes to proprioception i.e. detection of position and movement of body in space.
Enables regulation of muscle contraction and precisely matches force generation to motor task.
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What is muscle tone
The interaction between muscle spindles and alpha motor neurons ensure muscles are always under some degree of stretch
139
What are the two main classes of muscle spindle and their innervation
Chain spindles- are innervated by Ia fibres & II afferent fibres and encode mainly the static response of the fiber i.e. continue firing as long as muscle is stretched e.g. muscle tone
Bag spindles- are innervated by Group Ia afferents only and encode mainly the dynamic response of the fiber i.e. rate-of-change during a rapid stretch.
140
The difference between intrafusal and extrafusal muscle fibres
Extrafusal fibres form bulk of muscle and generate muscle tension.
Extrafusal fibres receive their motor innervation from alpha motor neurons.
Intrafusal fibres (spindles) have a sensory function and do not generate tension.
Intrafusal fibres receive their motor innervation from gamma motor neurons.
141
What is the function of gamma motor neurones
Regulate the length of the muscle spindle
142
What is the golgi tendon organ
Mechanoreceptor.
Lies in series with muscle fibres.
Detects changes in muscle tension, as when the muscle contracts the force acts directly on the tendon.
Acts like a strain gauge i.e. monitors muscle tension & the force of contraction.
Innervated by Ib afferents.
Contributes to proprioception i.e. detection of position and movement of body in space .
143
The physiological function of muscle spindles vs. Golgi tendon organs
Spindles detect changes in muscle length whereas Golgi Tendon Organs detect changes in muscle tension.
During an isometric contraction (tension without a change in muscle length) the Ib but not the Ia afferent is active.
During an isotonic contraction (change in length but not tension) the Ia but not the Ib is active.
144
What are the symptoms of Upper motor neurone damage after a few days
The Babinski sign
Spasticity
Hyporeflexia (reduced superficial reflexes)
Loss of fine movements
145
3 functional subdivisions of the cerebellum
Archicerebellum/Vestibulocerebellum
Paleocerebellum/Spinocerebellum
Neocerebellum/Cerebrocerebellum
146
What is the function of the vestibulocerebellum
Comprises flocculonodular lobe and part of vermis
Co-ordinates muscles involved in maintaining
balance and constancy of visual fields
Receives input from vestibular apparatus of inner ear
147
What is the function of the spinocerebellum
Comprises most of vermis and adjacent region of hemispheres
| Co-ordinates muscles involved in posture and locomotion
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What is the function of the cerebrocerebellum
Comprises lateral parts of hemispheres
Co-ordinates movements of distal limbs, particularly fine,
skilled movements of hands
(Also involved in learning, linguistic and cognitive functions)
149
What is the cerebellar homunculus
Parts of cerebellum which match up to the function of the specific subdivisions
Vestibulocerebellum = small section most medially
Spinocerebllum= larger section more laterally
Cerebrocerebellum= largest section most laterally
150
How is the constancy of the visual fields maintained
Keeping your gaze constant despite movement of your head, neck, body (rubber necking)
Vestibule senses change in position of head and communicates with extraocular muscle cranial nerves
(lateral and medial rectus)
151
How does information pass from the vestibular system to the vestibulocerebellum
Passes into the vestibular nucleus in the open medulla and then synapses and passes to the cerebellum at the flocculonodular lobe via the inferior cerebellar peduncle
152
What is the medial longitudinal fasciculus
The medial longitudinal fasciculus carries information about the direction that the eyes should move.
It connects the cranial nerve nuclei III, IV and VI together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement (from cranial nerve VIII, Vestibulocochlear nerve)
153
Which half of the body does the cerebellum control
The influence of the cerebellum is ipsilateral
| ie. Right half of cerebellum co-ordinates action of muscles on the right side of body
154
What is the function of the Spinocerebellar tract
Proprioception and other sensory information from spinal cord passes into the cerebellum via the ICP
To co ordinate what movements you are going to do
155
What are cerebrocerebellar connections
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Receives input from motor cortex via:
Pontine nuclei (MCP)
Inferior olivary nucleus (ICP)
Knows about intended movements
Output to: (via SCP to contralateral)
Motor cortex (via Thalamus)
Reticular nuclei
Red nucleus
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Role of cerebrocerebellum in motor learning
Blink response:
Puff of air at cornea = blink
A sound is made before puff of air (blink)
Eventually, the sound alone will induce a blink
Damage to inferior olivary nucleus stops this:
Puff of air = blink
Sound = no blink
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What is truncal ataxia
Inability to stand or sit without falling over
Midline lesion affecting vestibulocerebellum
Most commonly due to medulloblastoma
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What is gait ataxia
Lower limbs most affected, producing staggering, wide-based gait
Lesion of spinocerebellum
Most common in chronic alcoholics due to degeneration of cerebellar neurons in paravermal areas
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What are the symptoms of cerebellar hemisphere lesion
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Inco-ordination of voluntary movement, particularly in UL
Many possible causes eg. vascular, degenerative, trauma
Patients show:
Intention tremor
Past pointing or dysmetria
Adiadochokinesia
Dysarthria
Nystagmus
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160
What is the ampulla and cupula
Ampulla: a swelling at the base of each semicircular duct that contains the cupula.
Cupula: a gelatinous membrane that contains sensory processes (hair bundles or vestibular hair cells).
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In what direction does the cupola move in when you move your head
As the head rotates, the endolymph displays inertia i.e. lags behind
As the endolymph moves due to inertial forces, the cupula displaces within it.
A movement of the head to the right will cause a displacement of the cupula to the left.
A movement of the head to the left will cause a displacement of the cupula to the right
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What is kinocilium
The sensory processes in the cupula are made up of cilia from hair cells.
Hair cells are made up of many stereocilia, but only one kinocilium.
The kinocilium in each horizontal semicircular canal is orientated towards the front of the head.
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Depolarisation and hyper polarisation of the kinocilium
As the head rotates to the right, the fluid moves to the left.
On the right side of the head, the stereocilia shear towards the kinocilium. DEPOLARISATION= Increase in firing of vestibulocochlear nerve
On the left side, fluid travels against the axis of hair cells to cause stereocilia to shear away from kinocilium. HYPERPOLARISATION = decrease in action potential frequency
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What happens to your eyes when your head moves to the right
When head rotates rightward the following occurs:
Right horizontal canal hair cells depolarize
Right vestibular afferent activity increases.
Right vestibular nucleus activity increases.
In the cranial nerves (motoneurons to extraocular muscles), neurons in the left VI (abducens) & right III (oculomotor) fire at a higher frequency.
Those in the left III and right VI fire at a lower frequency.
The left lateral rectus and right medial rectus contract.
The left medial rectus and the right lateral rectus relax.
Both eyes rotate leftward.
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What is nystagmus
Composed of a slow tracking movement of the eyes followed by a fast component. It is named after the fast component.
Hence, a slow track to the left followed by a fast flick to the right is a rightwards nystagmus.
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What is Electro-oculography
Cornea is positively charged with respect to the retina.
As eyes move the potential difference changes on the voltmeter.
This reflects movement of the eyes.
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What is coriolis illusion
The subject in a steady turn for some time
| Subject moves head forward and feels a severe tumbling sensation (like sea sickness)
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What is caloric testing
Lie patient down (horizontal canals are now vertical and subject to gravity)
Irrigate ear with cold or warm water.
Warm water will set up convection currents such that endolymph will rise and distort the cupula to increase firing of the afferents causing nystagmus in the opposite direction.
The patient experiences vertigo and nystagmus when cold water is injected
Endolymph was sinking when it was cool and rising when it was warm, and thus the direction of flow of the endolymph was providing the proprioceptive signal to the vestibular organ.
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The effect of alcohol on the vestibular system
The cupula normally has neutral buoyancy.
Cupula has an excellent blood supply. Endolymph does not.
Cupula becomes saturated with alcohol.
As alcohol is less dense than water, the cupula of the horizontal canal is displaced upwards (if lying in bed)
Any movement of the endolymph will move the cupula a lot more than normal. Eye movements become exaggerated.
There is a mismatch between vestibular and visual modalities and the brain assumes (correctly) that it has been poisoned.
170
What is the blood supply to the head of the femur
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Trochanteric anastamosis (inferior and superior femoral circumflex arteries + medial and lateral femoral circumflex arteries)
Small contribution from branch of obturator artery running along ligamentum teres
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171
What is a fragility fracture
A fracture that follows simple fall from standing height or a force that is not usually enough to fracture a bone but occurs because of other factors e.g. osteoporosis
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Risk factors for a hip fracture
Gender - F:M = 3:1
Osteoporosis
Falls
Age (old)
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Pathophysiological causes of hip fracture
Osteoporosis (mainly)
Osteomalacia (Vit D deficiency)
Bone metastases
Bronchus, breast, kidney, prostate cancer
Haematological malignancy: multiple myeloma, lymphoma
Paget’s disease
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Why can there be pain in the knee in a hip fracture
Referred pain
Nerve supply to hip is ant. division of obturator nerve
Nerve supply to knee is post. division of obturator nerve
175
What is the Garden classification of femoral neck fractures
Grade 1- incomplete impacted fracture in valgus malalignment, which is generally stable.
Grade 2- incomplete but not displaced fracture.
Grade 3- incompletely displaced fracture in varus malalignment.
Grade 4- completely displaced fracture with no engagement of the two fragments.
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What is the surgical management of hip fractures
Intracapsular Fractures: Replacement hemiarthroplasty
Extracapsular Fractures: Dynamic hip screws, cannulated screws
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What is the acetabular notch
The articular surface is crescent shaped (lunate surface)and is deficient inferiorly
178
What ligament bridges the acetabular notch
transverse acetabular ligament
179
Attachments of the fibrous hip capsule
Proximal attachment: Encircles rim of acetabulum
Distal attachment:
Neck of femur
intertrochanteric line and greater trochanter anteriorly
Deficient posteriorly
180
Description of the iliofemoral ligament
Covers hip joint superiorly and anteriorly
Strongest ligament
Prevents hyperextension of the hip during standing
181
Description of the pubofemoral ligament
Covers hip joint anteriorly and inferiorly
| Prevents excessive abduction
182
Description of the ischiofemoral ligament
Covers hip joint posteriorly
| Weakest ligament
183
What muscle is the most powerful hip flexor
Iliopsoas
Also flexes trunk when the thigh is fixed
Postural muscle that maintains stability during standing
184
What separates the two components of Adductor magnus
Adductor hiatus- also passage of femoral artery into popliteal fossa to become popliteal artery
185
What is the largest muscle in the body
Gluteus maximus
Powerful hip extensor
Used when resisting gravity e.g. standing up, going up stairs NOT used for walking on level ground
186
Function and innervation of gluteus medius and minimum
Chief hip abductors
Very important in walking and keeping pelvis level
Superior gluteal nerve
187
What is the trendelenburg test
Detects weakness of the gluteus medius and minimus
Ask the patient to stand on each leg in turn.
Observe the pelvis for any tilt. In normal individuals the pelvis will remain level
When weight bearing on the affected hip, the pelvis on the opposite side drops and the body leans away from the affected side.
Can also be due to hip dislocations or arthritis
188
In which direction is the hip most likely to dislocate
Uncommon in adult due to stability of joint
Often associated with acetabular fractures
Posterior dislocations most common (90%)
Often caused by road traffic accident
189
What nerve can be damaged in posterior dislocation of the hip
Sciatic nerve
190
Effect of Dislocation on Femoral Head Circulation
Retinacular branches may be torn or stretched
Artery of ligamentum teres may be torn
Lack of blood supply leads to avascular necrosis of femoral head
191
Which nerve is at risk of damage in internal dislocations of the hip
Obturator nerve
192
What muscles are the main stabilisers of the knee
The quadriceps, hamstrings, sartorius, gracilis and iliotibial tract
193
What muscles insert onto the pea anserinus
Sartorius, gracilis and semitendinosus
194
What bones make up to ankle joint
Formed by distal ends of tibia and fibula (malleolar mortise) and trochlea of talus
Also called talocrural joint
Surrounded by articular capsule that is weaker anteriorly and posteriorly
195
Why is the ankle joint not prone to dislocation
Good congruity between malleolar mortise and trochlea
Reinforced by strong ligamentous ties between the bones of the ankle joint including: distal part of the interosseous membrane and anterior and posterior tibiofibular ligaments
Malleoli grip the talus
196
Why is dorsiflexion the most stable position of the ankle joint
The trochlea of the talus is wider anteriorly
During dorsiflexion, the anterior part of the trochlea moves between the malleoli
This spreads the tibia and fibula slightly, increasing their grip on the talus
197
Which 3 ligaments make up the lateral ligament of the ankle joint
Anterior talofibular ligament (weakest)
Posterior talofibular ligament
Calcaneofibular ligament
198
Which 4 ligaments make up the medial/deltoid ligament of the ankle
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Ant. tibiofibular
Post. tibiofibular
Tibionavicular
Tibiocalcaneal
(attached to medial malleolus)
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199
Which muscles carry out dorsiflexion
Muscles of the anterior compartment of the leg:
Tibialis anterior
Extensor hallucis longus
Extensor digitorum longus
Fibularis tertius
Supplied by the deep fibular nerve and anterior tibial artery
200
What would damage to the common/deep peroneal nerve at the fibular neck cause?
Foot drop (unable to dorsiflex)
201
What muscles carry out plantarflexion
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Muscles in the posterior compartment of the leg (except popliteus):
Gastrocnemius* (prime mover)
Soleus (prime mover)
Tibialis Posterior
Plantaris*
Flexor Digitorum Longus* (assists)
Flexor Hallucis Longus* (assists)
Peroneus Longus and Brevis (assists)
All supplied by the tibial nerve and posterior tibial artery
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202
What 2 joints make up the transverse talar joint
Talonavicular joint
| Calcaneocuboidal joint
203
At what joint does inversion and eversion occur
Subtalar joint: between the talus and underlying calcaneus
| Some movement at transverse talar joint
204
Which muscles carry out inversion (L4-L5)
Tibialis anterior and tibialis posterior
205
Which muscles carry out eversion (L5-S1)
Peroneus longus and Peroneus brevis
206
Which direction does the ankle usually sprain in
Most ankle sprains are inversion injuries with twisting of a plantarflexed foot
The lateral ligament of the ankle is weaker than the medial, particularly the anterior talofibular part
207
What is a Pott fracture-dislocation of the ankle
This is an eversion injury that pulls on the strong medial ligament causing avulsion of the medial malleolus
The talus rotates laterally, fracturing the fibula
208
What are the 3 arches of the foot
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Medial longitudinal (MLA)
Lateral longitudinal (LLA)
Transverse (TA)
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209
What is the composition and function of the medial longitudinal arch of the foot
Comprises – calcaneus, talus, navicular, 3 cuneiforms and medial 3 metatarsals
Weight is transmitted through the talus to the calcaneus and metatarsal heads
Medial longitudinal arch is higher and more important than the lateral longitudinal arch
210
How are the longitudinal arches of the foot maintained
Passive support includes ligaments and the shape if the bones: The plantar aponeurosis and plantar ligaments are the most important factors in maintaining the arches of the foot
Dynamic support includes intrinsic and extrinsic muscles of the foot: Small intrinsic muscles reflexively contract and brace the longitudinal arch
Flexor hallucis longus and flexor digitorum longus (extrinsic muscles) also support longitudinal arches
211
Support of the transverse arch of the foot
Passive support of the transverse arch is through the shape of the bones, especially the wedge shaped cuneiforms
Dynamic support is provided by fibularis longus and tibialis posterior
The tendons of these muscles cross the plantar surface of the foot like a stirrup
212
Signs of a tibial plateau fracture on an x-ray
Lipohaemarthrosis
| Depressed tibial plateau
213
Arterial supply to medial thigh compartment
Obturator artery (branch of internal iliac)
214
Arterial supply to anterior thigh compartment
Femoral artery (continuation of external iliac)
215
Arterial supply to posterior thigh compartment
Perforating arteries of profunda femoris
216
What is the cruciate anastamosis
Anastomosis between branches of the internal iliac (inf. gluteal artery) and profunda femoris arteries (Lateral and medial circumflex femoral arteries and 1st perforating artery)
Clinically important – allows blood to bypass and blockage of the external iliac or proximal femoral arteries
217
What are the peri-articular genicular anastamoses
Maintains blood supply to the leg during knee flexion which may impinge the popliteal artery
Composed of 5 genicular branches from popliteal artery:
Superior lateral
Superior medial
Middle
Inferior lateral
Inferior medial
Additional branches include:
Descending branch of lateral circumflex artery (long)
Descending genicular branch of femoral artery (short)
Anterior tibial recurrent artery
218
Blood supply to the dorsal aspect of the foot
Dorsalis pedis artery
Continuation of anterior tibial artery
Boundary is ankle joint
219
Blood supply to plantar aspect of the foot
Medial and lateral plantar arteries
| Bifurcation of posterior tibial artery
220
What is the (deep) plantar arch
Anastomosis of deep plantar branch of dorsalis pedis artery with lateral plantar artery
221
Innervation of anterior thigh compartment
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Femoral nerve (L2-L4)
(terminates as saphenous nerve which travels through adductor hiatus)
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222
Innervation of medial thigh compartment
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Obturator nerve (L2-L4)
Divides into anterior and posterior branches that lie on either side of adductor brevis
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223
Innervation of posterior thigh compartment
Tibial division of the sciatic nerve
224
Why is the common fibular/peroneal nerve most likely to get damaged
Due to superficial position as it winds round the neck of the fibula
Paralysis of dorsiflexor muscles resulting in ‘footdrop’
