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Neurology Systems > Week 1 > Flashcards

Week 1 Flashcards

1
Q

what are the divisions of the PNS?

A
  • sensory (afferent) division.
  • motor (efferent) division: somatic motor & autonomic (sympathetic and parasympathetic).
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2
Q

describe neurons

A
  • structural and functional unit of the nervous system.
  • excitable cells.
  • impulses carried as action potentials.
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3
Q

describe glial cells

A
  • non-excitable supporting cells.
  • much smaller than neurons.
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4
Q

Impulse transmission is by action potential which can travel:

A

in only one direction from cell body to synaptic terminal

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5
Q

what is the cytoplasm in the cell body of a neuron called?

A

perikaryon

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6
Q

what is the cytoplasm in the axon of a neuron called?

A

axoplasm

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7
Q

multipolar neurons are present in what?

A

interneurons
motor neurons

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8
Q

bipolar neurons are present in what?

A

olfactory mucosa
retinal nerve fibres

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9
Q

pseudounipolar neurons are present as what?

A

sensory neurons

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10
Q

the myelin sheath is formed by which cells?

A
  • Schwann cells in PNS.
  • oligodendrocytes in CNS.
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11
Q

white matter is composed of?

A

myelinated axons

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12
Q

grey matter is composed of?

A

neuronal cell bodies

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13
Q

what type of neuron supplies cutaneous receptors in the skin?

A

pseudounipolar > sensory neurons

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14
Q

what neuroglia are present in the PNS? and what is their function?

A
  • satellite cells > surround neuronal cell bodies.
  • schwann cells > myelination.
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15
Q

which neuroglia are present in the CNS?

A
  • ependymal cells.
  • astrocytes.
  • oligodendrocytes.
  • microglia.
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16
Q

what is the function of ependymal cells in the CNS?

A
  • line ventricles.
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17
Q

what is the function of microglia in the CNS?

A
  • phagocytosis.
  • scar tissue formation.
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18
Q

what is the function of oligodendrocytes in the CNS?

A

myelination

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19
Q

what is the function of astrocytes in the CNS?

A
  • have endfeet that surround synapses and capillaries.
  • help in K+ buffering.
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20
Q

what is the function of the blood-brain barrier?

A
  • is a protective mechanism that helps maintain a stable environment for the brain and prevents harmful amino acids & ions present in the bloodstream and blood cells from entering the brain.
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21
Q

where in the brain is the blood brain barrier absent?

A
  • parts of hypothalamus.
  • posterior pituitary.
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22
Q

what do drugs have to be in order to be delivered to the CNS?

A

lipid soluble or use suitable vectors

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23
Q

label the areas of the brain and their functions

A
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24
Q

label these prominences

A
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25
Q

label this muscle

A
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26
Q

label this

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27
Q

label this

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28
Q

label this

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29
Q

label this

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30
Q

label this

A
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31
Q

in which part of the brain do the lateral ventricles lie?

A
  • C-shaped cavities which lie in the cerebral hemispheres.
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32
Q

what connects the lateral ventricles with the 3rd ventricle?

A

interventricular foramen (of Munro)

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33
Q

in which part of the brain does the 3rd ventricle lie?

A
  • within the diencephalon.
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34
Q

in which part of the brain does the cerebral aqueduct lie?

A

midbrain

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35
Q

in which part of the brain does the 4th ventricle lie?

A
  • diamond-shaped ventricle lies in the hindbrain, between pons + medulla (in front) and cerebellum (at back).
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36
Q

label the ventricles of the brain

A
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37
Q

label the meninges

A
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38
Q

describe the subdural space

A
  • a potential space which is traversed by blood vessels penetrating into the CNS.
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39
Q

what does the subarachnoid space contain?

A

CSF

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40
Q

where is CSF present?

A
  • the fluid inside the cavity of the brain (i.e. ventricles) and central canal of spinal cord.
  • is also present surrounding the brain and spinal cord in the subarachnoid space.
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41
Q

where is CSF formed?

A

choroid plexus in the lateral, third and fourth ventricles.

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42
Q

where is CSF absorbed?

A

The CSF from the subarachnoid space is eventually reabsorbed through outpouchings into the superior sagittal sinus (SSS) known as the arachnoid granulations or villa.

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43
Q

label the surface features of the cerebral cortex

A
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44
Q

which collection of neuronal cells bodies is found buried in white matter of the brain?

A

basal ganglia

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45
Q

is grey matter on the surface or inside of the cerebral cortex?

A

surface

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46
Q

```

~~~

what is the large fissure seperating the left and right hemisphere of the brain called?

A

median longitudinal fissure

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47
Q

label this

A
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48
Q

label this

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49
Q

label this

A
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50
Q

the frontal part of the cerebral hemisphere is responsible for which functions?

A

motor function
intellect

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51
Q

the medial portions of the cerebral hemisphere have what function?

A

limbic system - storage and retrieval of information.

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52
Q

`

the temporal lobe is responsible for which sensory functions?

A

hearing and smell

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53
Q

the occipital lobe is responsible for what?

A

vision

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54
Q

the parietal lobe contains which sensory cortex?

A

somatosensory cortex

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55
Q

describe area 4 of the frontal lobe

A
  • Precentral gyrus > primary motor cortex.
  • somatotopic representation of contralateral half of body (motor homunculus).
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56
Q

describe areas 44 and 45 of the frontal lobe

A

inferior frontal gyrus > Broca’s area of motor speech.

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57
Q

what is function of the prefrontal cortex?

A

cognitive functions of higher order-intellect, judgement, prediction and planning.

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58
Q

describe areas 3, 1 and 2 of the parietal lobe

A
  • post-cental gyrus > primary sensory area.
  • recieves general sensations from contralateral half of body.
  • somatotopic representation (sensory homunculus).
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59
Q

what is the function of the superior parietal lobule?

A
  • interpretation of general sensory information (sensory association area) and conscious awareness of contralateral half of body.
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60
Q

what is the function of the inferior parietal lobule?

A
  • interface between somatosensory cortex and auditory association areas.
  • in dominant hemisphere, contributes to language functions.
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61
Q

a parietal lobe lesion can manifest as?

A
  • hemisensory neglect(reduced awareness of stimuli on one side of space, even though there may be no sensory loss).
  • right-left agnosia (inability to recognise and identify objects).
  • acalculia (inability to process numbers and perform calculations).
  • agraphia (inability to write letters, symbols, words or sentences).
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62
Q

describe Brodmann’s areas 41 and 42

A
  • superior temporal gyrus > primary auditory cortex (Heschl’s convolutions).
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63
Q

what is the function of Wernicke’s area?and what hemisphere is it present in?

A
  • auditory association area, posterior to areas 41, 42.
  • crucial for understanding of spoken word.
  • is present in the dominant hemisphere.
  • has connections with other language areas.
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64
Q

what is the function of the inferior surface of the temporal lobe?

A
  • recieves fibres from olfactory tract.
  • concious appreciation of smell.
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65
Q

describe area 17 of the occipital lobe

A
  • on the medial surface of the occipital lobe, on either side of the calcarine fissure.
  • primary visual cortex.
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66
Q

describe Brodmann’s areas 18 & 19

A
  • visual association cortex.
  • interpretation of visual images.
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67
Q

what structures compose the limbic lobe?

A
  • cingulate gyrus
  • hippocampus (medial aspect of temporal lobe)
  • parahippocampal gyrus
  • amygdyla (subcortical grey matter close to temporal pole).
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68
Q

what is aphasia?

A

problem with speech due to damage to one or more speech areas in the brain.

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69
Q

what are features of Broca’s aphasia?

A
  • understands speech, misses small words and aware of difficulties in speech.
  • damage to frontal lobe.
  • weakness/paralysis of one side of body.
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70
Q

what is the function of commisural fibres in the white matter?

A

connect corresponding areas of the two hemispheres (corpus callosum).

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70
Q

what are features of Wernicke’s aphasia?

A
  • fluent speech, with new meaningless words, can’t understand speech, unaware of mistakes.
  • damage to temporal lobe.
  • no paralysis.
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71
Q

what is the function of association fibres in the white matter?

A

connect one part of the cortex with the other. They may be short or long.

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72
Q

what is the function of projection fibres of the white matter?

A
  • run between the cerebral cortex and various subcortical centres.
  • they pass through the corona radiata and the internal capsule.
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73
Q

describe tractography

A
  • 3D modelling technique that maps functional white matter tracts using MRI.
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74
Q

describe the internal capsule of the brain,what structures is it located between and what is its blood supply?

A
  • composed of projection fibres passing to and from the cerebral cortex.
  • narrow area between the thalamus and caudate nucleus medially and the lentiform nucleus laterally.
  • derives blood supply from middle cerebral artery > frequently affected in stroke.
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75
Q

label the structures surrounding the internal capsule of the brain

A
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76
Q
  • describe the basal ganglia
  • what structures are involved?
A
  • subcortical nuclei (collection of neuronal cell bodies - grey matter) deep within each cerebral hemisphere.
  • composed of caudate nucleus, putamen and globus pallidus last two collectively form lentiform nucleus).
  • substantia nigra in midbrain is functionally part of them although not anatomically.
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77
Q

label this

A
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78
Q

what does the putamen and globus pallidus form?

A
  • a lens like structure > lentiform nucleus.
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79
Q

what are the individual basal ganglia called?

A
  • caudate nucleus
  • putamen
  • globus pallidus
  • substantia nigra
  • subthalamic nuclei
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80
Q

label this

A
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81
Q

label this

A
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82
Q

what is the function of the basal ganglia?

A
  • help to regulate, initiate and terminate movements.
  • often referred to as ‘extrapyramidal system’.
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83
Q

what are some pathologies affecting the basal ganglia?

A
  • parkinsons disease.
  • Huntingtons disease.
  • athetosis etc.
84
Q

label the cross-sectional anatomy of the spinal cord

A
85
Q

which neurons have their cell bodies in the ventral horn

A

motor neurons

86
Q

are ascending pathways sensory or motor?

A

sensory

87
Q

what are the names of two important ascending tracts?

A
  • lateral spinothalamic
  • dorsal column
88
Q

what is the name of an important descending tract?

A

corticospinal

89
Q

what is the function of the corticospinal/pyramidal descending tract?

A

carries motor impulses from motor cortex to skeletal muscles > control of voluntary skilled movements

90
Q

what is the function of the posterior/dorsal column ascending tract?

A

carries information about touch, tactile localisation, vibration, sense and proprioception from the periphery to the cerebral hemispheres.

91
Q

what is the function of the lateral spinothalamic ascending tract?

A

carries information about pain and temperature from the periphery to the cerebral hemispheres.

92
Q

where does the corticospinal/pyramidal descending tract start from?

A

left precentral gyrus > motor cortex (area 4)

93
Q

which part of the internal capsule do motor fibres pass down through?

A

posterior limb of internal capsule

94
Q

what is the blood supply of the internal capsule?

A

supplied by a branch of the middle cerebral artery

95
Q

where does the decussation of corticospinal fibres occur?

A

pyramids in the medulla oblongata forming the lateral corticospinal tract

96
Q

upper motor neurons are present in the..

A

primary motor cortex

97
Q

lower motor neurons originate from the…

A

in spinal cord/cranial nerve nucleii

98
Q

describe the transmission of the signal in the posterior/dorsal column ascending tract

A
  • 1st order neuron travels from skeletal muscles into the spinal cord and travels up to the lower part of the medulla, where it synapses with the cell body of the 2nd order neuron.
  • 2nd order neuron decussates in the medulla.
  • tract is now called medial lemniscus and passes through the medulla, pons and midbrain to reach the thalamus.
  • synapses with 3rd order neuron which starts from the thalamus and passes axons through the internal capsule and radiate to the post-central grus (area 2,1,3).
99
Q

discuss the lateral spinothalamic tract pathway

A
  • 1st order neurons enters into grey matter and ends at the same level as it synapses with 2nd order neurons.
  • 2nd order neurons crosses over at the level of entry to reach the lateral column > now called spinothalamic lateral spinothalamic tract.
  • 2nd order neurons synapse in thalamus and 3rd order neurons pass through the internal capsule, radiating to reach post-central gyris (area 2,1,3).
100
Q

what is a reflex?

A
  • involuntary stereotyped pattern of response brought on by a sensory stimulus.
  • many reflexes are mediated at the level of the spinal cord (spinal reflex).
  • they may be monosynaptic (e.g. stretch reflex) or polysynaptic (e.g. flexor reflex).
101
Q

what is the stretch reflex important in?

A

control of muscle tone and posture

102
Q

label the steps of the stretch reflex

A
103
Q

what is the importance of the flexor (and crossed extensor) reflex?

A

helps protect the body from painful stimuli.

104
Q

label the steps in the flexor (and crossed extensor) reflex

A
105
Q

what happens to reflexes when there is a upper motor neuron (UMN) lesion that causes paralysis?

A
  • reflexes are exaggerates in UMN lesions.
  • lower-motor neurons mediate reflexes.
106
Q

what are the consequences on muscle tone when there is a UMN lesion compared to a LMN lesion?

A
  • UMN lesion > increased tone (spasticity).
  • LMN lesion > decreased tone (flaccidity).
107
Q

what are the consequences of a left UMN lesion at the level of the internal capsule?

A
  • right-sided paralysis.
  • hyper-reflexia.
  • increased tone.
108
Q

what are the consequences of a left UMN lesion at the level of the upper cervical spinal cord?

A
  • left-sided paralysis.
  • hyper-reflexia.
  • increased tone.
109
Q

what are the consequences of a left LMN lesion?

A

left-sided paralysis
absent reflexes
flaccid

110
Q

discuss motor neuron disease

A
  • group of diseases affecting th lower motor neuron in the ventral horn of the spinal cord.
  • the neuron dies and as a result the muscle supplied by it atrophies.
  • progressive, incurable disease.
111
Q

if a lesion is above the level of decussation then signs and symptoms are?

A

contralateral

112
Q

if a lesion is below the level of decussation then signs and symptoms are?

A

ipsilateral

113
Q

what is Brown-Sequard syndrome?

A

Brown Se’quard syndrome is an incomplete pattern of injury showing a hemisection of the spinal cord which results in weakness and paralysis on one side of the damage and loss of pain and temperature sensations on the opposite side.

114
Q

what embryological structure does the nervous system develop from?

A

embryonic ectoderm

115
Q

at what stage of gestation does the CNS appear?

A

beginning of the 3rd week

116
Q

what gives rise to the neural plate?

A

thickening of ectoderm anterior to the primitive node

117
Q

what gives rise to the neural folds?

A

the edges of the neural plate thicken and move upwards

118
Q

what gives rise to the neural tube?

A
  • neural folds migrate towards each other and fuse at midline forming the neural tube
119
Q

describe the closing of the anterior and posterior neuropores of the neural tube

A
  • neural tube initially remains open at anterior and posterior ends.
  • anterior (cranial/rostral) neuropore closes 18-20 somite stage (25 days).
  • posterior (caudal) neuropore closes day 27.
120
Q

list congenital abnormalities that occur due to failure of the neural tube to close properly > neural tube defects (NDTs)

A
  • anencephaly
  • encephalocoele
  • spina bifida
121
Q

describe exencephaly/anencephaly (meroencephaly)

A
  • 1:1500 births (4x more common in females)
  • failue of anterior neuropore to close.
  • skull fails to form.
  • brain tissue degenerates
122
Q

what is craniorachischisis?

A
  • NDT
  • failure of neural tube closure along entire neuroaxis
123
Q

describe encephalocoele

A
  • 1:4000 births
  • failure in closure of rostral neural tube.
  • herniation of cerebral tissue through a defect in skull.
  • most frequent in occipital region.
  • variable degree of neurological deficits.
124
Q

describe spina bifida

A
  • defective closure of the caudal neural tube.
  • affects tissues overlying the spinal cord.
  • spina bifid = non-fusion of vertebral arches.
  • neural tissue may or may not be affected.
  • severity ranges from minor abnormalities to major clinical symptoms.
125
Q

describe spina bifida occulta

A
  • most minor form of spina bifida.
  • failure of embryonic halves of vertebral arch to grown normally and fuse.
  • occurs in L5 and L6 vertebrae of 10% of otherwise healthy people.
  • usually no clinical symptoms.
  • may result in dimple with small tuft of hair.
126
Q

describe spina bifida cystica

A
  • protrusion of spinal cord/and or meninges through the deficit in vertebral arches.
  • 1:1000 live births.
127
Q

describe spina bifida with meningocele

A
  • rarest form of spina bifida cystica.
  • protrusion of meninges and CSF.
128
Q

describe spina bifida with meningomyelocle

A
  • nerve roots and/or spinal cord included in the sac.
  • neurological deficits - loss of sensation and muscle paralysis.
  • area affected determined by level of lesion.
  • often associated with hydrocephalus.
  • most severe form myeloschisis > spinal cord in affected area open due to failure of neural folds to fuse.
129
Q

which supplement decreases the risk of developing spina bifida by 50-70%

A

folic acid 400 ug/day

130
Q

discuss the prenatal diagnosis of NTD

A
  • maternal blood screening: high levels of Indicated by high levels α-fetoprotein (AFP) in serum – AFP from foetal liver leaks into amniotic fluid then into maternal blood. Best detected 16 - 20 weeks.
  • amniocentesis high levels AFP in amniotic fluid.
  • ultrasound anencephaly from 12 weeks, spina bifida from 16-20 weeks.
131
Q

what are risk factors in developing NTD?

A
  • genetic predisposition.
  • nutritional (e.g. too little folate, too much vitamin A).
  • environmental (e.g. hyperthermia; taking certain drugs > sodium valproate).
132
Q

the brain and spinal cord are distinct at which pair of somites?

A

4th pair of somites

133
Q

what are the three primary brain vesicles formed during the 4th week of gestation?

A
134
Q

what are the 5th secondary brain vesicles that develop during the 5th week of gestation?

A
135
Q

at which stage of gestation does the cephalic flexure form? which structures is it located between?

A
  • end of 3rd week
  • between midbrain (mesencephalon) and hindbrain (rhombencephalon).
136
Q

at which stage of gestation does the cervical flexure form? which structures is it located between?

A
  • end of 4th week.
  • between hindbrain and spinal cord.
137
Q

at which stage of gestation does the pontine flexure form? what structures is it between?

A
  • 5th week.
  • between metencephalon and myelencephalon.
138
Q

label the flexures that form during folding of the CNS

A
139
Q

which structures are formed from the prosencephalon (forebrain)?

embryology

A
  • diencephalon > thalamus, hypothalamus, pituitary gland, pineal gland.
  • telencephalon > cerebral hemispheres, hippocampus, basal ganglia.
140
Q

what structures are formed from the mesencephalon (midbrain)?

embryology

A

superior and inferior colliculi

141
Q

what structures are formed from the rhombencephalon (hindbrain)?

embryology

A
  • metencephalon > cerebellum, pons.
  • myelencephalon > medulla.
142
Q

what is the function of cortical folding?

A
  • space saving > minimises brain volume.
  • brings together brain regions that would otherwise be far apart > optimises brain wiring and functional organisation.
143
Q

what is Lissencephaly?
what are the consequences?

A
  • ‘smooth brain’
  • caused by defective neuronal migration.
  • gyri and sulci fail to develop.
  • results in severe mental impairment, FTT, seizures and abnormal muscle tone.
  • many affected children die before age 10.
144
Q

what embryological structure gives rise to the ventricular system?

A

lumen of neural tube

145
Q

at which week of gestation does CSF begin to form?

A

during 5th week

146
Q

discuss hydrocephalus

A
  • accumulation of CSF.
  • results in enlarged brain and cranium.
  • frequently due to blocked aqueduct.
  • prevents CSF from lateral and 3rd ventricles from passing into the 4th ventricle > can’t drain properly.
147
Q

what are causes of hydrocephalus?

A
  • genetic
  • Prenatal viral infection or intraventricular haemorrhage.
  • spina bifida cystica.
148
Q

what type of epithelium is present in the neural tube?

A

pseudostratified epithelium

149
Q

which cells differentiate to form most cells of the CNS?

A

neuroepithelial cells of the neural tube
- EXCEPT for microglia, which are mesenchymal cells that migrate into CNS,.

150
Q

what emryological structure gives rise to the peripheral nervous system?

A
  • neural crest cells.
151
Q

what do thoracic and lumbar crest cells form?

A

sympathetic ganglia

152
Q

what do cervical and sacral crest cells form?

A

parasympathetic ganglia

153
Q

what embryological structure gives rise to the motor neurons of the spinal cord?

A

neural tube

154
Q

what embryological structure gives rise to the dorsal root ganglion (cell bodies) and dorsal horn of the spinalo cord?

A

neural crest cells

155
Q

what happens to the spinal nerves as the vertebral column and dura matter grow more rapidly during development?

A
  • cord at progressively higher levels (newborn: L2 or L3, adult: L1).
  • initially spinal nerves found at the level of orgin, growth > spinal nerves become elongated forming cauda equina.
  • pia mater form terminal filum.
156
Q

describe steps 1-8 of synaptic transmission

A
  1. Synthesis and packaging of neurotransmitter (usually) in presynaptic terminals
  2. Na+ action potential reaches terminal
  3. Activates voltage gated Ca2+ channels
  4. Triggers Ca2+-dependent exocytosis of pre-packaged vesicles of transmitter
  5. Transmitter diffuses across cleft and binds to ionotropic and/or metabotropic receptors to evoke postsynaptic response
  6. Presynaptic autoreceptors inhibit further transmitter release
  7. Transmitter is (usually) inactivated by uptake into glia or neurons
  8. Transmitter is metabolised within cells
157
Q

how do local anaesthetics reduce synaptic transmission?

A
  • block voltage-gated Na+ channels
158
Q

how does botulinum toxin reduce synaptic transmission?

A
  • blocks release machinery (prevents exocytosis of neurotransmitters).
159
Q

how does black widow spider venom reduce synaptic transmission?

A

blocks voltage-gated Ca2+ channels.

160
Q

how do SSRIs potentiate synaptic transmission?

A
  • block uptake of transmitter.
161
Q

how do anti-cholinesterases potentiate synaptic transmission?

A

they block the breakdwon of transmitter

162
Q

how do benzodiazepenes potentiate synaptic transmission?

A
  • potentiate effects of transmitter on receptor.
163
Q

list the monoamine neurotransmitters

A

noradrenaline
dopamine
serotonin (5-HT)

164
Q

list the amino acid neurotransmitters

A

glutamate
GABA
glycine

165
Q

list the categories of neurotransmitters

A
  • acetylcholine
  • monoamines
  • amino acids
  • purines
  • neuropeptides
  • nitric oxide
166
Q

which dopamine signalling pathway is involved in reward and addiction?

A
  • mesolimbic: projects ventral tegmental area to nucleus accumbens and other limbic structures.
167
Q

which dopamine signalling pathway is involved in executive function?

A
  • mesocortical: projects to prefrontal cortex.
168
Q

which psychological functions are affected by dopamine?

A
  • voluntary movement
  • emotions/reward
  • vomiting
169
Q

what is the anatomical distribution of dopamine in the brain?

A
  • brain stem.
  • basal ganglia.
  • limbic system and frontal cortex.
170
Q

what is the pathology of parkinsons disease?

A
  • degeneration of dopaminergic neurons in the substantia nigra (nigrostriatal pathway).
  • causes dopamine deficiency in the basal ganglia.
171
Q

what is the pathway of dopamine synthesis?

A
172
Q

what type of receptors are dopamine receptors?

A
  • 5 subtypes of metabotropic (G-protein) coupled receptors named D1-D5.
173
Q

what are the key enzymes involved in dopamine breakdown?

A
  • Monoamine oxidase B (MAO-B).
  • Catechol-O-methyltransferase (COMT).
174
Q

what is dopamine broken down into by MAO-B and COMT?

A

homovanillic acid

175
Q

what are symptoms of parkinsons disease?

A

stiffness
slow movements
change in posture
tremor

176
Q

what are some dopaminergic drugs used in the treatment of PD?

A
  • DA precursor > Levodopa.
  • DA agonists: Ergots > bromocriptine. Non-ergots > ropinirole. Apomorphine.
177
Q

give the names of some MAOB inhbitors used in the treatment of PD

A

selegiline
rasagiline
safinamide

178
Q

give the names of some COMT inhibitors used in the treatment of PD

A

entacapone
opicapone

179
Q

dopaminergic drugs can cause what side effects in PD

A
  • nausea
  • vomiting
  • psychosis
  • impulsivity/abnormal behaviours
180
Q

give an example of a DA antagonist that doesn’t cross the BBB

A

domperidone

181
Q

what are dyskinesias and what drugs can cause them?

A

= abnormal involuntary movements.
- can be caused by dopaminergic drugs.

182
Q

describe the vestibular system

A
  • a sensory system essential in the control of posture and balance.
  • found in the inner ear, it is a series of fluid-filled membranous tubes (labyrinths), which are embedded in the temporal bone.
183
Q

what structures compose the semi-circular canals?

A
  • vestibular apparatus consists of 3 semi-circular canals, the utricle to which the semi-circular canals all connect and the saccule.
184
Q

which parts of the vestibular apparatus contain sensory hair cells?

A
  • the ampulla (swellings) at the base of the semi-circular canals.
  • utricle.
  • saccule.
185
Q

what are the utricle and saccule collectively known as?

A
  • otolith organs.
186
Q

what is the role of the utricle in balance?

A
  • has sensory receptors (maculae) for back/front tilt and horizontal acceleration.
187
Q

what is the role of the saccule in balance?

A
  • has sensory receptors for vertical acceleration.
188
Q

what is the role of the semi-circular canals in balance?

A
  • has sensory receptors (cristae) in the ampulla for rotational acceleration.
189
Q

discuss the sensory receptors in the semi-circular canals

A
  • sensory receptors embedded in ampulla.
  • hair cells are embedded in a flexible gelatinous structure called the cupula which becomes distored by the movement of the ednolymph fluid within the canals.
190
Q

what is the fluid within semi-circular canals called?

A

endolymph

191
Q

how are sensory hair cells in the ampulla activated? and what nerve do they communicate with?

A
  • movement of endolymph pushes on the gelatinous cupula and activates the receptor cells.
  • the cilia of the hair cells embedded within the cupula synapse directly with the sensory neurons of the vestibular nerve (CN VIII).
192
Q

how do the sensory organs of the semi-circular canals detect rotational acceleration?

A
  • when skull is rotated, the ampulla moves instantly whereas the endolymph does not at first.
  • this produces drag > bends cupula and the embedded cilia, the opposite direction to the movement.
193
Q

what causes the sensationg of dizziness after suddenly stopping after rotating at a constant velocity?

A
  • will cause endolymph to continue to move due to momentum creating a continuing sense of movement and dizziness.
194
Q

what are the two types of cilia present on hair cells?

A
  • a single very large kinocilium.
  • a set of progressively smalled stereocilia.
195
Q

what does distortion of the cilia in the direction of the kinocilium cause?

A
  • depolarisation and increased discharge of APs in the vestibular nerve.
196
Q

what does distortion of the cilia away from the kinocilium cause?

A
  • hyperpolarisation and decreased discharge of APs in the vestibular nerve.
197
Q

what is the collective name for the sensory apparatus of the utricle and saccule?

A

maculae

198
Q

what is the orientation of the macula in the utricle?

A

horizontal

199
Q

what is the orientation of the macula in the saccule?

A

vertical

200
Q

what is embedded in the otlith membrane of utricles and saccules?

A

CaCO3 crystals called otoliths

201
Q

how does the utricle detect head tilting?

A
  • detected by the macula in the utricle (horizontal plane).
  • tilting the head moves the otoliths and the otolith membrane in which they are embedded.
  • this distorts the jelly and moves the cilia.
202
Q

what does a backwards tilt of the head cause?

A
  • moves otolith in the direction of the kinocilium causing depolarisation and increased discharge of action potentials.
203
Q

describe tonic labyrinthine reflexes

A
  • keep the axis of the head in a constant relationship with the rest of the body.
  • use info from maculae and neck proprioceptors.
204
Q

describe the dynamic righting reflexes

A
  • rapid postural adjustements that are made to stop you falling when you trip.
  • long reflexes, involving extension of all limbs.
  • most profound in cats.
205
Q

describe vestibular nystagmus

A
  • a series of saccadic eye movements that rotate the eye against the direction of passive rotation of the head and body so that the original direction of gaze is preserved despite head rotating.
  • a vestibulo-ocular reflex.
206
Q

what does cold water in the right ear cause?

A

left sided nystagmus

207
Q

what does warm water in the right ear cause?

A

right-sided nystagmus

208
Q

describe labyrinthitis

A
  • acute interference with normal vestibular function as a result of infection = all ANS symptoms + vertigo +/- nystagmus.
  • vertigo can cause gross impairment of posture and balance.

Neurology Systems (14 decks)

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