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Medicine > Lower Limb 2 > Flashcards

Lower Limb 2 Flashcards

0
Q

3 muscular compartments of the thigh

A

Anterior extensor, posterior flexor, medial adductor

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1
Q

Hamstring muscles

A

Semimembranosus, semitendinosus and long head of biceps femoris

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2
Q

Common proximal attachment and nerve supply of hamstrings

A

Ischial tuberosity and tibial nerve (L5-S2)

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3
Q

Distal insertion of semitendinosus

A

Pes anserinus - proximal tibia medial to tibial tuberosity

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4
Q

Distal attachment of semimembranosus

A

Posterior medial condyle of tibia

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5
Q

Distal attachment of long head of biceps femoris

A

Head of fibula and lateral condyle of tibia

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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

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7
Q

Function of hamstrings at the hip

A

Extend hip when trunk is fixed

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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.

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9
Q

Nerve supply and proximal attachment of hamstring part of adductor Magnus

A

Tibial nerve.

Ischial tuberosity

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10
Q

Angle of inclination

A

Angle between neck and shaft of femur-determine obliquity of the femur. Usually 126 degrees

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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.

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12
Q

Genu varum/ bow leg

A

Q angle

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13
Q

Genu valgum/ knock knee

A

Q angle> 17 degrees
Tibia abducted with respect to femur
Lateral sided osteoarthritis

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14
Q

Attachments of anterior cruciate ligament

A

Anterior intercondylar region of tibia - travels superoposteriorly - lateral femoral condyle

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15
Q

Attachments of posterior cruciate ligament

A

Posterior intercondylar region of tibia - travels superoanteriorly - medial femoral condyle

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16
Q

Function of posterior cruciate ligament

A
  1. Prevent posterior displacement of tibia
  2. Prevents hyper flexion of the knee
  3. Main stabiliser of the flexed knee when weight bearing e.g walking downhill
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17
Q

Function of anterior cruciate ligament

A
  1. Prevents anterior displacement of tibia

2. Prevents hyper extension

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18
Q

Function of menisci cartilage

A
  1. Increase joint congruency
  2. Distribute weight evenly
  3. Shock absorption
  4. Aid lubrication by facilitating movement of synovial fluid
  5. Assist in locking mechanism
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19
Q

Function of articularis genu

A

Part of Vastus intermedius

Holds the large suprapatellar bursa in place

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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

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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.

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22
Q

How to unlock the knee joint

A

Popliteus muscle laterally rotates the femur

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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

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24
Q

What are denticulate ligaments

A

Lateral extensions of the pia mater

anchors the spinal cord in the vertebral canal

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25
Q

At what level does the spinal cord terminate in an adult

A

L1/L2 as the conus medullar is

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26
Q

What is the filum terminale and where does it terminate

A

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

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27
Q

What is the Cauda equina (horses tail)

A

Dorsal and ventral roots of lower lumbar, sacral and coccygeal segmental spinal nerves

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28
Q

How is the Cauda Equina formed

A

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

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29
Q

At which levels of the spinal cord is the lateral grey horn present in a cross section

A

T1-L2 (sympathetic)

S2-S4 (parasympathetic)

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30
Q

In which direction of the spinal cord does white matter increase

A

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.

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31
Q

Where in the spinal cord is the ventral grey horn largest

A

VGH enlarged where motor fibres to limbs arise
Cervical enlargement: C3-T2
Lumbosacral enlargement: L1-S2

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32
Q

2 groups of somaesthetic modalities

A
  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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33
Q

Where do cell bodies of 1st order neurones reside

A

Dorsal root ganglion (PNS)

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34
Q

Where do cell bodies of 2nd order neurones reside

A

Ipsilateral grey matter (CNS)

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35
Q

Where do cell bodies of 3rd order neurones reside

A

Thalamus and axons project to somato-sensory cortex through internal capsule

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36
Q

What sensations does the Spinothalamic Tract transmit

A

Pain, Temperature, Some touch and pressure from body

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37
Q

What happens to the 1st order neurone of the STT

A

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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38
Q

How does the 2nd order neurone of the STT cross the midline

A

Passes anterior to the central canal via the ventral white commisure to enter into STT and ascend

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39
Q

What is the name of the continuation of the STT at the boundary of the medulla

A

Spinal/lateral lemniscus

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40
Q

Where do 2nd order neurones of the STT synapse

A

Ventroposterolateral nucleus in the thalamus

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41
Q

What sensations does the Dorsal column tract transmit

A

Proprioception and discriminative/fine touch

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42
Q

What happens to the 1st order neurone of the DCT

A

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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43
Q

In which dorsal column does info from below T6 ascend

A 
Gracile Fascicle (Medial)
Gracile fascicles run through entire spinal cord segments
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44
Q

In which dorsal column does info from above T6 ascend

A 
Cuneate Fascile (Lateral)
only present in spinal cord above T6
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45
Q

How do 2nd order neurones of the DCT cross the midline

A

Via Internal Arcuate Fibres to medial lemniscus

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46
Q

Where to 2nd order neurones of the DCT synapse

A

VPL on thalamus

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47
Q

What info does the lateral spinothalamic tract transmit

A

Pain and temperature.

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48
Q

What info does the anterior spinothalamic tract (or ventral spinothalamic tract) transmit

A

Crude touch and firm pressure.

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49
Q

In what tract is sensory information from the face carried to the thalamus

A

Trigeminothalamic tract

Cranial nerves 5,7,9,10

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50
Q

What are the 3 parts of the sensory trigeminal nucleus

A

Mesencephalic
Chief/pontine
Spinal

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51
Q

In which part of the spinal nucleus is pain and temperature received

A

caudal part of spinal nucleus

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52
Q

In which part of the spinal nucleus is simple touch and pressure received

A

Rostral parts of spinal nucleus

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53
Q

Where are the cell bodies of 1st order neurones of the TGT that carry pain and temperature

A

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

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54
Q

Where are the cell bodies of 1st order neurones of the TGT that carry simple touch and pressure

A

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

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55
Q

Sensory consequences of a lesion affecting the lateral medulla

A

Ipsilateral facial sensory loss

Contralateral body Sensory deficit

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56
Q

Where is the spinal nucleus and spinal tract

A

Lateral medulla

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57
Q

What sensory modality does the pontine nucleus receive

A

Discriminative touch on the face

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58
Q

What sensory modality does the mesencephalic nucleus receive

A

Proprioception on the face

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59
Q

Which pathway is an exception to the generalisation

that first order cell bodies are in peripheral ganglia

A

Mesencephalic nucleus

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60
Q

Discriminatory touch of the face pathway

A

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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61
Q

Proprioception of the face pathway

A

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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62
Q

What other fibres do the 1st order mesencephalic neurone contact apart from the 2nd order neurone

A

Contact motor neurons in Trigeminal motor nucleus e.g. V3 to muscles of mastication

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63
Q

Where do 2nd order neurones in the TGT synapse

A

Ventro postero medial nucleus of thalamus

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64
Q

Where do Facial and vestibulocochlear cranial nerves exit the skull

A

Internal acoustic meatus in the petrous part of the temporal bone (hardest bone in the body)

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65
Q

The names of the 3 bony ossicles in the ear

A

Malleus, incus, stapes

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66
Q

What fluid does the cochlea contain

A

Perilymph

Similar to extra cellular fluid so has a high proportion of Na+ ions 140mmol - sets up a membrane potential

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67
Q

Why is the middle ear a high risk area

A

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

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68
Q

What fluid does the cochlear duct (membranous sac running through the cochlea) contain

A

Endolymph

Intracellular like fluid containing high conc of K+ ions

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69
Q

What 2 chambers does the cochlear duct split the cochlea into

A

Scala vestibuli
Scala tympani
Continuous at the apex/helicotrema

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70
Q

How is hydraulic pressure changed within the cochlea

A

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.

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71
Q

What is the name of the auditory receptor and how it works

A

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

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72
Q

The path of primary auditory neurones

A

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

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73
Q

Auditory centres in the dorsal brainstem (caudal to rostral)

A

Cochlear nuclei
Superior olivary nucleus in pons
Inferior colliculi
Medial geniculate nucleus of thalamus

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74
Q

How do fibres pass from the cochlear nuclei to the superior olivary nucleus

A

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

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75
Q

How do fibres from the superior olivary nucleus pass to the inferior colliculi

A

Via the Lateral lemniscus (Spinothalamic fibres also run in this tract)
Some fibres may synapse, cross or bypass the inferior colliculus

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76
Q

How do fibres from the inferior colliculi pass to the Medial geniculate nucleus of the thalamus

A

Via the inferior brachium

Then ascends to Heschls/superior temporal gyrus

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77
Q

What is tonotopic organisation

A

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

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78
Q

In which cerebral hemisphere is the auditory association area

A

Left hemisphere only

Cerebral dominance

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79
Q

Function of descending auditory pathways

A

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

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80
Q

Why does a unilateral lesion have virtually no effect on hearing

A

As the auditory pathway is bilateral

The ability to localise sound may be impaired

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81
Q

2 types of deafness

A

Sensorineural (defect in function of spiral ganglion or cochlear nerve)
Conductive (defect of sound transmission up to spiral ganglion)

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82
Q

If a subject has conductive hearing loss in one ear, in which ear will the sound be loudest

A

The damaged ear.

Because hearing in normal ear is inhibited by ambient sound (auditory masking)

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83
Q

If a subject has sensorineural hearing loss in one ear, in which ear will the sound be loudest

A

Sound heard louder in the normal ear (sound needs to be amplified)

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84
Q

What is the function of the non-neuronal layer of the retina

A

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.

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85
Q

What types of cells does the neuronal layer of the retina contain

A

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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86
Q

What cells’ axons make up the optic nerve

A

Secondary ganglion cell axons

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87
Q

Does the optic disk contain photoreceptors

A

No- it is the blind spot

Where optic nerve and vasculature exit/enter eye

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88
Q

Is the retina in the PNS or the CNS

A

CNS- it is an outgrowth of the diencephalon
so the visual pathway occurs wholly within the CNS
Eyeball has meningeal layers

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89
Q

Where to 2nd order ganglion cells synapse with 3rd order neurones

A

Lateral geniculate nucleus of the thalamus via optic tract

Then 3rd order neurones travel via optic radiation to visual cortex

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90
Q

What is papilloedema

A

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
Q

Which retina fibres cross over and which remain ipsilateral

A

Temporal retinal fibres remain in the ipsilateral optic tract
Nasal retinal fibres cross over to the contralateral optic tract via the optic chasm

92
Q

2 different visual fields

A

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

93
Q

Retinotopic organisation

A

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

94
Q

What is the function of the upper division of the optic radiation

A

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

95
Q

What is the function of the lower division of the optic radiation

A

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
Q

What is the blood supply of the optic radiation

A

Deep branches of the middle cerebral artery and posterior cerebral artery.

97
Q

What visual field defect leads to monocular blindness

A

Damage to ipsilateral optic nerve

98
Q

What visual field defect leads to heteronymous hemianopia

A

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
Q

What visual field defect leads to homonymous hemianopia

A

Lesion in optic tract opposite to eye with temporal visual field loss

100
Q

90% of the optic tract fibres go to the LGN where do the other 10% go

A

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
Q

What is the pupillary light reflex

A

Ability of both pupils to respond (constrict or dilate) dependant on the level of light the retina receives.

102
Q

Which cranial nerves and their nuclei are involved in the pupillary light reflex

A

Optic nerve and tract (Afferent/sensory root)

Occulomotor (Efferent/motor root) Edinger-Westphal Nucleus

103
Q

What 2 components make up the pupillary light reflex

A

Direct component = light in one eye, same pupil constricts

Consensual component = light in one eye, other pupil constricts

104
Q

What is the accommodation reflex

A

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
Q

What 3 processes occur in the accommodation reflex

A

Accommodation (lens becomes rounded)- ciliary muscles contract
Pupil constricts – sphincter pupillae
Ocular convergence – medial rectus

106
Q

What happens to the eyes when moving focus from a distant to a near object

A

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
Q

How does the lens increase refractive power

A

The lens then increases its curvature to become more biconvex.

108
Q

What is convergence of the eyes

A

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
Q

What is the action of the eye muscles to cause convergence

A

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
Q

4 stages of general anaesthesia

A

Stage 1: Analgesia
Stage 2: Excitation
Stage 3: Surgical anaesthesia (4 planes/loss of reflexes)
Stage 4: Medullary depression

111
Q

What is the main factor that determines rate of induction and recovery of anaesthesia

A

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
Q

What is the cause of malignant hyperthermia

A

All halogenated GAs can cause it

Treated by administration of dantrolene – inhibits release of Ca2+ from sarcoplasmic reticulum

113
Q

Do IV GAs work faster than inhaled GAs

A

Yes- can work in seconds vs minutes for inhaled GAs
normally used for induction
e.g. Thiopentol, propofol

114
Q

Examples of Local anaesthetics

A

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
Q

Why are local anaesthetics less effective in inflamed tissue

A

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
Q

What are lower motor neurones

A

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
Q

What are the symptoms of LMN lesions

A 
Muscle wasting
Muscle weakness/reduced power
Hypotonia
Absent tendon reflexes
Fasciculation/fibrillation
118
Q

What are the causes of LMN lesions

A

Peripheral nerve injury (crush or cut) e.g. ALS

Poliomyelitis

119
Q

What are 2 types of upper motor neurones

A

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
Q

What happens if there is damage to the corticospinal tract only

A

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
Q

3 Descending corticospinal pathways

A

Reticulospinal- voluntary movement/ breathing/ consciousness
Vestibulospinal- controls posture
Rubrospinal- controls (baseline) muscle tone

122
Q

Somatotopic representation on the anterior 2/3rds of the posterior limb of the internal capsule

A

Descending corticospinal/bulbar fibres pass through internal capsule
Near genu = face then arm then trunk then leg

123
Q

What happens to descending corticospinal fibres at the pyramids

A

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
Q

How do UMNs synapse with LMNs

A

UMN cross the ventral white commisure to contact LMN in contralateral VGH
LMN extend to skeletal/striated muscle via segmental spinal nerves

125
Q

What is the corticobulbar pathway

A

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
Q

Corticobulbar input to cranial nerve nuclei

A

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
Q

What are the consequences if the LMN of the facial nerve is damaged

A

Ipsilateral side of face will be paralysed

128
Q

What are the consequences if the UMN of the facial nerve is damaged e.g. stroke on the int capsule (supranuclear lesion)

A

Contralateral lower face paralysis (the ipsilateral side of face and contralateral upper face will all function normally as they have a bilateral innervation)

129
Q

Examples of infra nuclear lesions/ LMN facial deficit

A

Bell’s palsy, tumours of cerebellopontine angle, middle ear disease, parotid tumour.

130
Q

Which motor neurons are directly responsible for the generation of force by muscle.

A

Alpha motor neurones

Gamma dont generate force

131
Q

Where in the spinal cord is the VGH area larger

A

Enlarged in Lumbar and sacral vertebra

Largest in Lumbar

132
Q

What is a motor neurone pool

A

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
Q

What is segmental organisation of lower motor neurons

A

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
Q

Why do motor units vary in size

A

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
Q

What are the different types of force and fatiguability in motor units

A

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
Q

What are the 3 main sources of input to alpha motor neurons

A

Sensory inputs from peripheral proprioceptors.
Local inputs from spinal interneurons.
Descending inputs from brain upper motor neurons.

137
Q

What are muscle spindles

A

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.

138
Q

What is muscle tone

A

The interaction between muscle spindles and alpha motor neurons ensure muscles are always under some degree of stretch

139
Q

What are the two main classes of muscle spindle and their innervation

A

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
Q

The difference between intrafusal and extrafusal muscle fibres

A

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
Q

What is the function of gamma motor neurones

A

Regulate the length of the muscle spindle

142
Q

What is the golgi tendon organ

A

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
Q

The physiological function of muscle spindles vs. Golgi tendon organs

A

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
Q

What are the symptoms of Upper motor neurone damage after a few days

A

The Babinski sign
Spasticity
Hyporeflexia (reduced superficial reflexes)
Loss of fine movements

145
Q

3 functional subdivisions of the cerebellum

A

Archicerebellum/Vestibulocerebellum
Paleocerebellum/Spinocerebellum
Neocerebellum/Cerebrocerebellum

146
Q

What is the function of the vestibulocerebellum

A

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
Q

What is the function of the spinocerebellum

A

Comprises most of vermis and adjacent region of hemispheres

Co-ordinates muscles involved in posture and locomotion

148
Q

What is the function of the cerebrocerebellum

A

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
Q

What is the cerebellar homunculus

A

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
Q

How is the constancy of the visual fields maintained

A

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
Q

How does information pass from the vestibular system to the vestibulocerebellum

A

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
Q

What is the medial longitudinal fasciculus

A

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
Q

Which half of the body does the cerebellum control

A

The influence of the cerebellum is ipsilateral

ie. Right half of cerebellum co-ordinates action of muscles on the right side of body

154
Q

What is the function of the Spinocerebellar tract

A

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
Q

What are cerebrocerebellar connections

A 
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
156
Q

Role of cerebrocerebellum in motor learning

A

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

157
Q

What is truncal ataxia

A

Inability to stand or sit without falling over
Midline lesion affecting vestibulocerebellum
Most commonly due to medulloblastoma

158
Q

What is gait ataxia

A

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

159
Q

What are the symptoms of cerebellar hemisphere lesion

A 
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
160
Q

What is the ampulla and cupula

A

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).

161
Q

In what direction does the cupola move in when you move your head

A

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

162
Q

What is kinocilium

A

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.

163
Q

Depolarisation and hyper polarisation of the kinocilium

A

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

164
Q

What happens to your eyes when your head moves to the right

A

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.

165
Q

What is nystagmus

A

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.

166
Q

What is Electro-oculography

A

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.

167
Q

What is coriolis illusion

A

The subject in a steady turn for some time

Subject moves head forward and feels a severe tumbling sensation (like sea sickness)

168
Q

What is caloric testing

A

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.

169
Q

The effect of alcohol on the vestibular system

A

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
Q

What is the blood supply to the head of the femur

A 
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
171
Q

What is a fragility fracture

A

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

172
Q

Risk factors for a hip fracture

A

Gender - F:M = 3:1
Osteoporosis
Falls
Age (old)

173
Q

Pathophysiological causes of hip fracture

A

Osteoporosis (mainly)
Osteomalacia (Vit D deficiency)
Bone metastases
Bronchus, breast, kidney, prostate cancer
Haematological malignancy: multiple myeloma, lymphoma
Paget’s disease

174
Q

Why can there be pain in the knee in a hip fracture

A

Referred pain
Nerve supply to hip is ant. division of obturator nerve
Nerve supply to knee is post. division of obturator nerve

175
Q

What is the Garden classification of femoral neck fractures

A

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.

176
Q

What is the surgical management of hip fractures

A

Intracapsular Fractures: Replacement hemiarthroplasty

Extracapsular Fractures: Dynamic hip screws, cannulated screws

177
Q

What is the acetabular notch

A

The articular surface is crescent shaped (lunate surface)and is deficient inferiorly

178
Q

What ligament bridges the acetabular notch

A

transverse acetabular ligament

179
Q

Attachments of the fibrous hip capsule

A

Proximal attachment: Encircles rim of acetabulum
Distal attachment:
Neck of femur
intertrochanteric line and greater trochanter anteriorly
Deficient posteriorly

180
Q

Description of the iliofemoral ligament

A

Covers hip joint superiorly and anteriorly
Strongest ligament
Prevents hyperextension of the hip during standing

181
Q

Description of the pubofemoral ligament

A

Covers hip joint anteriorly and inferiorly

Prevents excessive abduction

182
Q

Description of the ischiofemoral ligament

A

Covers hip joint posteriorly

Weakest ligament

183
Q

What muscle is the most powerful hip flexor

A

Iliopsoas
Also flexes trunk when the thigh is fixed
Postural muscle that maintains stability during standing

184
Q

What separates the two components of Adductor magnus

A

Adductor hiatus- also passage of femoral artery into popliteal fossa to become popliteal artery

185
Q

What is the largest muscle in the body

A

Gluteus maximus
Powerful hip extensor
Used when resisting gravity e.g. standing up, going up stairs NOT used for walking on level ground

186
Q

Function and innervation of gluteus medius and minimum

A

Chief hip abductors
Very important in walking and keeping pelvis level
Superior gluteal nerve

187
Q

What is the trendelenburg test

A

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
Q

In which direction is the hip most likely to dislocate

A

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
Q

What nerve can be damaged in posterior dislocation of the hip

A

Sciatic nerve

190
Q

Effect of Dislocation on Femoral Head Circulation

A

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
Q

Which nerve is at risk of damage in internal dislocations of the hip

A

Obturator nerve

192
Q

What muscles are the main stabilisers of the knee

A

The quadriceps, hamstrings, sartorius, gracilis and iliotibial tract

193
Q

What muscles insert onto the pea anserinus

A

Sartorius, gracilis and semitendinosus

194
Q

What bones make up to ankle joint

A

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
Q

Why is the ankle joint not prone to dislocation

A

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
Q

Why is dorsiflexion the most stable position of the ankle joint

A

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
Q

Which 3 ligaments make up the lateral ligament of the ankle joint

A

Anterior talofibular ligament (weakest)
Posterior talofibular ligament
Calcaneofibular ligament

198
Q

Which 4 ligaments make up the medial/deltoid ligament of the ankle

A 
Ant. tibiofibular
Post. tibiofibular
Tibionavicular
Tibiocalcaneal
(attached to medial malleolus)
199
Q

Which muscles carry out dorsiflexion

A

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
Q

What would damage to the common/deep peroneal nerve at the fibular neck cause?

A

Foot drop (unable to dorsiflex)

201
Q

What muscles carry out plantarflexion

A 
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
202
Q

What 2 joints make up the transverse talar joint

A

Talonavicular joint

Calcaneocuboidal joint

203
Q

At what joint does inversion and eversion occur

A

Subtalar joint: between the talus and underlying calcaneus

Some movement at transverse talar joint

204
Q

Which muscles carry out inversion (L4-L5)

A

Tibialis anterior and tibialis posterior

205
Q

Which muscles carry out eversion (L5-S1)

A

Peroneus longus and Peroneus brevis

206
Q

Which direction does the ankle usually sprain in

A

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
Q

What is a Pott fracture-dislocation of the ankle

A

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
Q

What are the 3 arches of the foot

A 
Medial longitudinal (MLA)
Lateral longitudinal (LLA)
Transverse (TA)
209
Q

What is the composition and function of the medial longitudinal arch of the foot

A

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
Q

How are the longitudinal arches of the foot maintained

A

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
Q

Support of the transverse arch of the foot

A

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
Q

Signs of a tibial plateau fracture on an x-ray

A

Lipohaemarthrosis

Depressed tibial plateau

213
Q

Arterial supply to medial thigh compartment

A

Obturator artery (branch of internal iliac)

214
Q

Arterial supply to anterior thigh compartment

A

Femoral artery (continuation of external iliac)

215
Q

Arterial supply to posterior thigh compartment

A

Perforating arteries of profunda femoris

216
Q

What is the cruciate anastamosis

A

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
Q

What are the peri-articular genicular anastamoses

A

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
Q

Blood supply to the dorsal aspect of the foot

A

Dorsalis pedis artery
Continuation of anterior tibial artery
Boundary is ankle joint

219
Q

Blood supply to plantar aspect of the foot

A

Medial and lateral plantar arteries

Bifurcation of posterior tibial artery

220
Q

What is the (deep) plantar arch

A

Anastomosis of deep plantar branch of dorsalis pedis artery with lateral plantar artery

221
Q

Innervation of anterior thigh compartment

A 
Femoral nerve (L2-L4)
(terminates as saphenous nerve which travels through adductor hiatus)
222
Q

Innervation of medial thigh compartment

A 
Obturator nerve (L2-L4)
Divides into anterior and posterior branches that lie on either side of adductor brevis
223
Q

Innervation of posterior thigh compartment

A

Tibial division of the sciatic nerve

224
Q

Why is the common fibular/peroneal nerve most likely to get damaged

A

Due to superficial position as it winds round the neck of the fibula
Paralysis of dorsiflexor muscles resulting in ‘footdrop’

Medicine (7 decks)

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