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Neuroscience > Neuro Anatomy > Flashcards

Neuro Anatomy Flashcards

0
Q

Where does CN XI enter the cranium?

A

Foramen magnum

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1
Q

What muscles does hypoglossal innervate?

A

Intrinsic and extrinsic muscles of tongue except palatoglossus

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2
Q

What type of nerve is CN XII?

A

Somatic motor

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3
Q

Where does CN XI exit the cranium?

A

Jugular foramen

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4
Q

Where does CN XII exit?

A

Hypoglossal foramen

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5
Q

What type of nerve is CN XI?

A

Somatic motor

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6
Q

Which reflex tests medulla function?

A

Gag reflex

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7
Q

What part of brainstem does gag reflex test?

A

Medulla

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8
Q

What CN provides taste to posterior 1/3 of tongue?

A

Glossopharyngeal (IX)

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9
Q

What nerve is responsible for sensory input of gag reflex?

A

CN IX glossopharyngeal - sensory to pharynx

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11
Q

What nerve type is the most important component of vagus?

A

Visceral motor but also has bronchial motor, somatic sensory, visceral special sensory and visceral sensory components

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12
Q

What CN innervates the vocal cords?

A

Vagus (recurrent laryngeal branch)

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13
Q

What CN provides sensory input from pharynx?

A

IX glossopharyngeal

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14
Q

What CN provides visceral motor to parotid gland?

A

Glossopharyngeal

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15
Q

What muscle does glossopharyngeal innervate?

A

Stylopharyngeus (muscle of soft palate)

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16
Q

How many vestibular nuclei are there?

A

4

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17
Q

What muscles does spinal accessory innervate?

A

Trapezius and sternocleidomastoid

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17
Q

Where does CN IX exit the skull?

A

Jugular foramen

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19
Q

What nerve is responsible for motor output of gag reflex?

A

CN X vagus - motor to pharynx

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19
Q

How cochlear nuclei are there?

A

2 - dorsal and ventral

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20
Q

Which CN is responsible for taste at anterior 2/3 of tongue?

A

Facial

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21
Q

What are the 2 nerves that form the facial nerve?

A

Facial nerve proper and nervus intermedius

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23
Q

What is the visceral efferent component of CN VII?

A

Parasympathetic to lacrimcal, sublingual and sublingual glands (not parotid gland!)

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24
Q

What CN innervates stapedius muscle?

A

Facial

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25
Q

Where does facial nerve exit the skull?

A

Internal acoustic meatus

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26
Q

Through which foramen does facial nerve enter the face?

A

stylomastoid foramen

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27
Q

What are the 5 terminal branches of facial nerve?

A 
Temporal
Zygomatic
Buccal/maxillary
Mandibular
Cervical
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28
Q

Which CN passes through the parotid gland?

A

Facial

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29
Q

Which CN innervates the parotid gland?

A

Glossopharyngeal

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30
Q

Which reflex tests pontine function?

A

Corneal blink reflex

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31
Q

What is the motor output to eyelid of the corneal blink reflex?

A

CN VII - facial

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32
Q

Which CN supplies the branchial motor component to the muscles of mastication?

A

Trigeminal

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33
Q

What is the motor component of facial nerve?

A

innervates muscles of facial expression and stapedius muscle

“Seventh for Stapedius”

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35
Q

Where does CN VII exit the skull?

A

Internal acoustic meatus

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35
Q

What portion of brainstem does corneal blink reflex test?

A

Pons

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35
Q

What is the somatic sensory component of trigeminal nerve?

A

sensory to face up to apex of the head

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36
Q

What muscles does trigeminal innervate?

A

muscles of mastication

tensor tympani in middle ear (Trigeminal for Tensor)

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37
Q

Which CN supplies sensory to the face?

A

Trigeminal

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38
Q

What are the 3 major sensory divisions of CN V?

A

V1 - opthalmic
V2 - maxillary
V3 - mandibular

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39
Q

Which trigeminal nuclei are responsible for sensory to face and head?

A

Chief sensory nucleus

Spinal trigeminal nucleus (STN)

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40
Q

Which trigeminal nucleus is responsible for proprioception?

A

mesencephalic nucleus

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41
Q

How many nuclei does trigeminal nucleus consist?

A

4 running from midbrain to upper spinal cord

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42
Q

Where does CNV V1 exit the skull?

A

superior orbital fissure

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43
Q

Which division of trigeminal exits foramen ovale?

A

V3 - mandibular

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44
Q

Where does the sensory root of trigeminal travel to?

A

trigeminal ganglion

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44
Q

Where does CNV V2 exit the skull?

A

foramen rotundum

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45
Q

Which trigeminal division exits the superior orbital fissure?

A

V1 - opthalmic

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47
Q

What is the sensory input of the corneal blink reflex?

A

Opthalmic division (V1) of trigeminal

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48
Q

Where does CNV V3 exit the skull?

A

foramen ovale

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49
Q

What is the sensory input of the pupillary light reflex?

A

optic

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50
Q

Which division of trigeminal exits foramen rotundum?

A

V2 - maxillary

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51
Q

What is the motor output of pupillary light reflex?

A

Oculomotor

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52
Q

Which muscle is innervated by CNIII during pupillary light reflex?

A

sphincter pupillae

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53
Q

Which CNs exit cribiform plate?

A

CNI

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54
Q

Which CNs exit optic canal?

A

CNII

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55
Q

Which CNs enter the orbit via the superior orbital fissure?

A

CNIII,IV,V1,VI

oculomotor, trochlea, opthalmic division of trigeminal, abducens

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56
Q

Which CNs exit auditory canal?

A

CNVII, VIII

facial, vestibulocochlea

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57
Q

Which CNs exit jugular foramen?

A

CNIX, X, XI

glossopharyngeal, vagus, spinal accessory

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58
Q

Which CNs exit hypoglossal foramen?

A

CNXII - hypoglossal

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59
Q

What extraocular muscles does oculomotor supply?

A

4 out of 6
sup and inf rectus
medial rectus
inf oblique

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60
Q

Which CN elevates the eyelid?

A

oculomotor

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61
Q

Which CN depresses the eyelid?

A

facial

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62
Q

Which CN constricts the pupils?

A

oculomotor

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63
Q

What is the visceral motor component of oculomotor?

A

constrict pupils

focusing via ciliary muscles

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64
Q

What extraocular muscle does abducens innervate?

A

lateral rectus (LR6)

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65
Q

Which extraocular muscle does trochlea innervate?

A

superior oblique (SO4)

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66
Q

Where do the nerves to the extraocular muscles exit the skull?

A

superior orbital fissure

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67
Q

Where does olfactory nerve exit the skull?

A

cribiform plate of ethmoid bone

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68
Q

Where does optic nerve exit?

A

optic canal

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69
Q

Which column in brainstem is nucleus solitarius located?

A

visceral sensory

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70
Q

Which CNs provide inputs to nucleus solitarius?

A

CNVII, IX, X

facial, glossopharyngeal, vagus

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71
Q

What are the 3 columns of sensory nuclei

A

from medial to lateral:
visceral sensory
somatic sensory
special sensory

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72
Q

Which CNs send outputs to nucleus ambiguous?

A

CN IX, X

glossopharyngeal, vagus

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73
Q

Which column in brainstem if nucleus ambiguous located?

A

branchial motor

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74
Q

Where does nucleus ambiguous lie?

A

behind inferior olive in medulla

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75
Q

What are the 3 motor columns in the brainstem?

A

From medial to lateral:
somatic motor
branchial motor
visceral motor

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76
Q

Where are the motor nerve nuclei located?

A

close to the midline

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77
Q

Where are the sensory nerve nuclei located?

A

lateral

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78
Q

How many layers of neurons are in the cortex?

A

6

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79
Q

What is contained within grey matter?

A

Cell bodies

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80
Q

What is the function of myelin and what cell is responsible for myelinating axons?

A

provides electrical insulation for neurons - accelerate conduction
oligodendrocytes are responsible for myelinating axons in the CNS and Schwann cells are responsible for myelinating axons in the PNS

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81
Q

What is contained within white matter?

A

Myelinated axons

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82
Q

Where are cells of the choroid plexus located?

A

ventricles

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83
Q

What forms CSF

A

choroid plexus

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84
Q

Where are ependymal cells located and what do they do?

A

line central canal of spinal cord and ventricles

aid CSF flow

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84
Q

What are the passive support functions of astrocytes?

A
  • NT uptake and degradation (i.e. glutamate transporters)
  • potassium homeostasis
  • neuronal energy supply
  • maintenance of BBB
  • injury response and recovery
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85
Q

What are the active functions of astrocytes and how do they act?

A

-modulate neuronal function:
glia show modulations in intracellular calcium
calcium waves inhibit neurons
-modulate blood flow by regulating vascular tone
astrocytes surround arterioles and venules
calcium wave within astrocyte causes vasoconstriction or vasodilation

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87
Q

How do oligodendrocytes compare to Schwann cells?

A

Oligodendrocytes extend processes that wrap around parts of several axons whereas a Schwann cell wraps around one axon

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88
Q

How are neurons morphologically distinct from other cells?

A

cytoskeleton contains actin, intermediate filaments and microtubules
cell body is the metabolic centre of the cell
cell body gives rise to axons - major output site- and dendrites -major input site
high proportion of total cell volume consists of axons and dendrites

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89
Q

What are the immune cells of the CNS?

A

microglia derived from bone marrow and of macrophage origin - part of the innate immune system

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90
Q

What are the boundaries of the brainstem?

A

extends from mammillary bodies rostrally to pyramidal decussation caudally

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91
Q

What are peripheral nerve fibres composed of?

A
  • one or more fascicles of nerve fibres
  • each fascicle surrounded by perineurium CT
  • epineurium surrounds multiple fascicles
  • endoneurium (loose vascular CT) surrounds each nerve fibre and Schwann cell within each fascicle
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91
Q

What are autonomic ganglia?

A

cell bodies of post-ganglionic neurons

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92
Q

Where in the cranium if the brainstem located?

A

posterior cranial fossa

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94
Q

What are the gross anatomical features of the medulla oblongata?

A

dorsal columns and gracile and cuneate tubercles - dorsal

inferior olives and pyramids - ventral

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95
Q

What are the gross anatomical features of the pons?

A

linked with cerebellum by cerebellar peduncles

limited by 4th ventricle

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96
Q

What are sensory ganglia?

A

Cell bodies of sensory neurons

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97
Q

What comprises the tectum?

A

colliculi

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98
Q

At what level do the spinal nerves end?

A

C2

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99
Q

What are the gross anatomical features of the midbrain?

A 
superior colliculi (eye movements) and inferior colliculi (hearing) - dorsal
cerebral peduncles - ventral
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100
Q

What does the tegmentum contain?

A

Cranial nerves and caudal reticular formation (reflexes and autonomic functions)

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101
Q

What is the embryological origin of sensory cranial nerve nuclei?

A

Alar plate

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102
Q

What is the embryological origin of motor cranial nerve nuclei?

A

basal plate

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103
Q

What are the 2 major ascending long fibre tracts and where do they cross?

A

dorsal column-medial lemniscus system (fine touch and proprioception) crosses in medial lemniscus in medulla

anterolateral system (pain) crosses in spinal cord

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104
Q

What are the orbital margins and what are they formed by?

A

Supraorbital margin formed by frontal bone

Infraorbital margin formed by zygomatic bone and maxilla

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105
Q

What bones form the floor of the orbit?

A

maxilla, zygomatic and palatine orbital plates

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106
Q

What is the main descending long fibre tract and where does it cross?

A

corticospinal tract (motor function) crosses at pyramidal decussation in medulla

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107
Q

What bones form the lateral wall of the orbit?

A

Zygomatic orbital plate and greater wing of sphenoid

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108
Q

What do the dorsal aspects of the brainstem contain?

A

cranial nerve nuclei and reticular formation

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109
Q

What forms 5/6t of the eyeball?

A

sclera

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110
Q

What bones form the medial wall of the orbit?

A

maxilla orbital plate, lacrimal bone, ethmoid bone, body of sphenoid

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111
Q

What are the functions of sclera?

A

maintains shape of globe
provides attachments for extraocular muscles
protection: collagen confers toughness

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112
Q

What bones from the roof of the orbit?

A

frontal bone and lesser wing of sphenoid

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113
Q

What are the important features of the cornea?

A

avascular and transparent
5 histological layers
endothelial layer controls water balance within eye

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114
Q

What are the key structures in the anterior chamber angle?

A

cornea
trabecular meshwork
canal of Schlemm
ciliary body

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115
Q

What forms 1/6th of the eyeball?

A

cornea

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116
Q

Why is the cornea transparent?

A

Highly organised structure provides transparency:
Collagen fibrils are uniform in diameter, evenly spaced, and run parallel to each other in bundles (lamellae)
all fibrils within a lamella run parallel while adjacent lamellae lie at angles to each other

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117
Q

How does sclera confer protection?

A

Collagen is whirled

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118
Q

Where is the anterior chamber angle?

A

Junction between iris and cornea where aqueous humour drains out of eye into the venous supply

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119
Q

What are the functions of the ciliary body?

A
  • ciliary epithelium forms aqueous humour
  • ciliary processes tether lens
  • ciliary muscles accommodate the eye
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120
Q

What is the function of aqueous humour?

A

maintains heath of lens and cornea

creates intraocular pressure

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121
Q

What components accommodate/focus the eye?

A
  • ciliary muscle

- zonules (ligaments) that attach to lens and ciliary processes

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122
Q

How does the eye focus?

A

Ciliary muscles relax to view objects in the distance

Ciliary muscles contract to view objects close up

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123
Q

What is presbyopia and what causes it?

A

Loss of accommodation with age caused by reduced flexibility in the lens capsule and zonules

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124
Q

What are the components of the middle layer of the eye?

A

ciliary body, choroid and iris

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125
Q

What is the iris?

A

aperture of the eye

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126
Q

What muscles control pupil size and what is their innervation?

A

sphincter pupillae - constricts pupil (parasympathetic)

dilator pupillae - dilates pupil (sympathetic)

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127
Q

Where is the choroid located and what is its function?

A

Underneath retina

supplies nutrients to retina

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128
Q

How many layers make up the choroid and which layer is most important?

A

3 layers of blood vessels

choriocapillaris is most important because it sits immediately deep to retina

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129
Q

What are the components of the retina?

A 
Optic nerve/disc
Fovea
Macula
Posterior pole
Orra serrata
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130
Q

What are the features of the fovea?

A
  • avascular (nutrients derived from choroid) so thin layered
  • high density of cones (high visual acuity)
  • no rods
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131
Q

What are the components of the optic nerve?

A
  • lamina cribosa
  • central retinal artery and vein
  • dura
  • sclera
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132
Q

What is the lamina cribrosa made of and what is its function?

A
  • band of dense CT

- seive-like structure which transmits nerve fibres

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133
Q

What is a consequence of glaucoma on lamina cribrosa?

A

High pressure can displace lamina cribrosa and damage axons

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134
Q

What is the main blood supply to the orbit?

A 
branch of ophthalmic artery:
central retinal artery
long posterior ciliary artery
short posterior ciliary artery
anterior ciliary artery
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135
Q

Which ciliary artery does not pierce the globe?

A

anterior ciliary artery

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136
Q

What is the blood supply to the retina?

A

Central retinal artery supplies inner retina

posterior ciliary arteries supply photoreceptors

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137
Q

What CN innervates levator palpebrae superiosis?

A

CNIII

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138
Q

Which muscle elevates the upper lid?

A

levator palpebrae superiosis

139
Q

Which muscle depresses the upper lid?

A

orbicularis oculi

140
Q

Which CN innervates orbicularis oculi?

A

CNVII

142
Q

What do the long posterior ciliary arteries supply?

A

photoreceptors far from optic nerve head

supplies more anterior structures like iris and ciliary body

143
Q

What are the 3 basic layers of the eyeball and what are their functions?

A

Outer coat: sclera and cornea - strength
Middle coat: uvea - nutrition
Inner coat: retina - vision

144
Q

Which structure of the eye is important for central vision?

A

macula - centre of macula is fovea

145
Q

What it visual acuity?

A

ability to resolve fine detail

146
Q

What optical factors affect visual acuity?

A
  • pupil size (appature)
  • clarity of optical media (e.g. corneal opacities and cataracts impair)
  • refractive errors
147
Q

What are the 6 types of neurons in the retina?

A 
rods and cones (photoreceptors)
horizontal cells
bipolar cells
amacrine cells
ganglion cells
148
Q

What are the two synaptic layers of the retina?

A

outer plexiform and inner plexiform

149
Q

Which neuron in the retina is the last to receive light information?

A

photoreceptors

150
Q

How many types of cones are there and what are they?

A

3 types which allow colour vision

red, green and blue cones

151
Q

Which photoreceptor is densest in the fovea?

A

cones

152
Q

Which photoreceptor is absent in the fovea?

A

rods

153
Q

Which photoreceptor is more numerous in the retina?

A

rods outnumber cones by 20:1

154
Q

What is necessary to resolve fine detail?

A

good optical system and small, closely

160
Q

What do the short posterior ciliary arteries supply?

A
  • photoreceptors relatively close to optic nerve

- optic nerve head

161
Q

What is the sequence of the “through” pathway in the retina?

A

Photoreceptors connect to bipolar cells which connect to ganglion cells. Ganglion cells send message to brain

162
Q

Which retinal neuron can modulate signals in the outer retina?

A

horizontal cells

163
Q

Which retinal neuron can modulate signals in the inner retina?

A

amacrine cells

164
Q

What are the different bipolar cells and how many of each are there?

A

10 different bipolar cells:
1 rod bipolar cell
9 cone bipolar cell

165
Q

What are the functions of bipolar cells?

A

spatial vision and colour vision

166
Q

Which bipolar cell hyperpolarises when light falls on the retina?

A

OFF bipolar cells

167
Q

Which bipolar cell depolarises when light falls on the retina?

A

ON bipolar cells

168
Q

How do ON bipolar cells respond when light hits the retina?

A

They always depolarise

169
Q

How do OFF bipolar cells respond when light hits the retina?

A

Hyperpolarise

170
Q

Which neurons input onto horizontal cells and which neurons do horizontal cells send output to?

A

Photoreceptors input to horizontal cells

Horizontal cells output to photoreceptors

171
Q

How do horizontal cells respond to light?

A

Hyperpolarise

172
Q

Which neurotransmitter do horizontal cells release in response to light?

A

Release GABA to photoreceptors

173
Q

What sort of signals do amacrine cells send?

A

Inhibitory cells that release inhibitory neurotransmitters glycine and GABA

174
Q

Which neuron in the retina fires action potentials?

A

ON ganglion cell depolarise and fire action potentials

175
Q

What is receptive field?

A

the area of retina that, when stimulated with light, changes cell membrane potential

176
Q

What protein do rods contain?

A

rhodopsin

177
Q

What protein do cones contain?

A

one of three different types of cone-opsins

178
Q

Which vitamin do opsins bind?

A

Vitamin A

179
Q

How do photoreceptors respond to dark?

A

cGMP gates sodium channels and allows continuous influx of sodium ions causing depolarisation

180
Q

How do photoreceptors respond to light?

A

Phosphodiesterase breaks down cGMP to GMP
Sodium channels close
Influx of sodium ceases
Cell becomes hyperpolarised and releases glutamate

181
Q

What is the sequence of the “through” pathway in the retina?

A

Photoreceptors connect to bipolar cells which connect to ganglion cells. Ganglion cells send message to brain

182
Q

What creates the centre-surround phenomenon?

A

Some ganglion cells depolarise when light is shone on the centre of the receptive field while some ganglion cells hyperpolarise when light is shone on the peripheral part of receptive field

183
Q

What is the surround response?

A

Light shone on peripheral part of receptive field
Surround photoreceptors hyperpolarise releasing glutamate
Horizontal cells receive input, become hyperpolarised releasing GABA
GABA causes central photoreceptors to depolarise
Eventually ganglion cells become hyperpolarised

184
Q

What is the centre response?

A

Light shone to centre of receptive field
Photoreceptors hyperpolarise releasing glutamate
Causing the depolarisation of ON bipolar cells
Which causes depolarisation of ganglion cells

185
Q

What do M ganglion cells encode?

A

Motion

186
Q

What do P ganglion cells encode?

A

Colour vision and visual acuity

187
Q

What forms the optic chiasm and where does it lie?

A

fibres from left and right optic nerves combine to form optic chiasm
optic chiasm lies at the base of the brain, anterior to pituitary and is surrounded by the carotid arteries

188
Q

Where do nasal fibres of optic nerve cross?

A

Optic chiasm

189
Q

Which fibres pick up light from the temporal visual field?

A

All the cells at nasal half of retina

190
Q

Where do temporal fibres cross?

A

Temporal fibres from each eye travel through chiasm and don’t cross

191
Q

Which hemisphere interprets information from the left visual hemifield?

A

Right hemisphere

192
Q

Where do most ganglion cell axons involved in vision terminate?

A

Lateral geniculate nucleus in the thalamus

193
Q

How many layers are within the LGN and which cell types make up the layers?

A

6 layers within LGN:
Layers 1 and 2 are magnocellular layers
Layers 3-6 are parvocellular layers

194
Q

Where do M and P ganglion cell axons terminate in the LGN?

A

M cells target magnocellular layers of LGN (layers 1-2)

P cells target parvocellular layers of LGN (layers 3-6)

195
Q

T/F

Inputs from each eye mix at the LGN

A

False
Inputs from each eye are segregated
Mixing of info from each eye does not occur at LGN

196
Q

Where do LGN neurons project to?

A

Primary visual cortex in the occipital lobe around the calcarine fissure

197
Q

What are the optic radiations?

A

Ganglion cell axons that exit the LGN form white matter tracts which travel to occipital lobe

198
Q

Where is central vision encoded?

A

Encodes at the most posterior (occipital) part of the primary visual cortex

199
Q

Where is peripheral vision encoded?

A

More anterior part of the primary visual cortex, along the banks of the calcarine fissure

200
Q

If a lesion only affect vision in only 1 eye, what is the location of the lesion?

A

In the eye itself or in the ipsilateral optic nerve

before the optic chiasm

201
Q

If a lesion impairs vision in both eyes in some form or another, what is the location of the lesion?

A

The lesion may be at the chiasm or posterior to the chiasm

202
Q

What is the location of a lesion causing a bitemporal hemianopia - affecting opposite sides of the visual field?

A

At the optic chiasm

203
Q

What is the location of a lesion causing vision impairment in half the eye on the same side of both eyes - affecting same side of the visual field?

A

Optic tracts

204
Q

What is the location of a lesion which impairs vision in 1 quadrant of each eye on the same side of the visual field?

A

Optic radiations

205
Q

What is the general location of a lesion that impairs vision on the same side of the visual field?

A

Post chiasm

206
Q

What is the location of a lesion which causes visual impairment in half of each eye on the same side of the visual field but has macula sparing?

A

Visual cortex:

Macula sparing means normal central vision and is indicative of a vascular problem in the visual cortex

207
Q

What are melanopsin ganglion cells?

A

Intrinsically photosensitive ganglion cells in the retina

208
Q

What visual pigment do ipGCs contains?

A

melanopsin

209
Q

How do ipGCs respond to light?

A

Activation of melanopsin causes depolarisation of ipGCs

210
Q

Which muscle causes the pupil to constrict and what is its innervation?

A

Sphincter pupillae innervated by parasympathetic fibres which travel with CN III

211
Q

Which muscle causes pupil dilation and what is its innervation?

A

Dilator pupillae innervated by sympathetic fibres

212
Q

What is the pathway controlling pupil response?

A

ipGC process travels down optic nerve through the chiasm
Travels to optical pretectal nucleus in the midbrain
Then sends a process to each Edinger Westfal nucleus
A process from each Edinger Westfal nuclues heads back towards the eye which synapses at ciliary ganglion which travels to iris

213
Q

Where is the location of a lesion causing an afferent pupil defect?

A

Lesion can be from ipGC to pretectal nucleus in the midbrain

214
Q

What is the location of a lesion causing an efferent pupil defect?

A

Lesion can be located anywhere from the Edinger Westfal nucleus to the ciliary ganglion

215
Q

Where do ipGCs project to control circadian rhythm?

A

Suprachiasmatic nucleus in the hypothalamus

216
Q

What is the pain pathway for migraine and how are ipGCs involved?

A

Pain signal from dura is carried by trigeminal nerve to the brainstem and to the posterior nucleus of the thalamus
ipGCs also project to posterior thalamic nucleus
the posterior thalamic nucleus is light sensitive and becomes excited

217
Q

Which retinal neuron can modulate signals in the outer retina?

A

horizontal cells

218
Q

Where does superior oblique insert?

A

Inserts far behind the equator at an oblique angle to lateral rectus

219
Q

Where does the tendon of superior oblique run through?

A

The tendon runs through a fibrocartilage pulley (trochlea)

220
Q

What is the primary action of superior oblique?

A

Torsion - depression

221
Q

Where does inferior oblique insert?

A

Behind the equator, close to lateral rectus

222
Q

What is the primary action of inferior oblique?

A

torsion - elevation

223
Q

What is the effect of contracting superior rectus?

A

Superior rectus elevates the globe an also imposes a twisting action as well as a pulling action outward

224
Q

How to test superior rectus in isolation?

A

Abduct the eye, then look up

225
Q

How to test inferior rectus in isolation?

A

Abduct eye then look down

226
Q

How to test superior oblique in isolation?

A

Adduct eye then look up

227
Q

How to test inferior oblique in isolation?

A

Adduct eye then look down

228
Q

How to test medial rectus in isolation?

A

Adduct eye

229
Q

How to test lateral rectus in isolation?

A

Abduct eye

230
Q

Which extraocular muscle does trochlear nerve innervate?

A

Contralateral superior oblique

231
Q

Which brainstem centre is responsible for horizontal gaze control?

A

Pontine paramedian reticular formation

232
Q

Which brainstem centre is responsible for vertical gaze control?

A

Midbrain paramedian reticular formation

233
Q

What are the neuron types in the pontine reticular formation?

A

Burst neurons and omnipause neurons

234
Q

What are the functions of burst neurons?

A
  • Fire at high frequency just before a horizontal eye movement
  • excite ipsilateral abducens
  • suppress contralateral abducens
235
Q

What are the functions of omnipause neurons?

A
  • fire continuously during saccade except when burst neurons activated
  • GABAergic neurons that project to contralateral abducens nucleus
236
Q

What is the neural pathway for looking to the left?

A

Cortex signals to pontine paramedian reticular formation
In left eye,
Excitatory burst neurons input to left abducens nucleus to cause contraction of left lateral rectus and the right abducens nucleus sends inhibitory signals via medial longitudinal fasciculus to left oculomotor nucleus to cause relaxation of left medial rectus

In right eye,
Inhibitory burst neurons signal to right abducens nucleus to cause relaxation of right lateral rectus and the left abducens nucleus sends excitatory signals via MLF to right oculomotor nucleus to cause contraction of right medial rectus

237
Q

In what direction do frontal eye fields control saccades?

A

Contralateral direction

238
Q

Which UMNs drive brainstem gaze centres?

A

Frontal eye fields
Posterior parietal cortex
Superior colliculus
Basal ganglia

239
Q

What do semicircular canals detect?

A

Head position

240
Q

What do otolith organs detect?

A

Linear acceleration

241
Q

What is the pathway for the vestibular-ocular reflex when turning the head to the right?

A

Information must be coordinated with CNIII, VI, and VIII:

242
Q

What is parallel processing?

A

When cones are hyperpolarised by light, this hyperpolarising signal is communicated to both ON and OFF bipolar cells

243
Q

Which retinal neuron can modulate signals in the inner retina?

A

amacrine cells

244
Q

What are the different bipolar cells and how many of each are there?

A

10 different bipolar cells:
1 rod bipolar cell
9 cone bipolar cell

245
Q

What are the functions of bipolar cells?

A

spatial vision and colour vision

246
Q

Which bipolar cell hyperpolarises when light falls on the retina?

A

OFF bipolar cells

247
Q

Which bipolar cell depolarises when light falls on the retina?

A

ON bipolar cells

248
Q

What are saccadic eye movement?

A

Fovea shifts rapidly to a new visual target

249
Q

How do ON bipolar cells respond when light hits the retina?

A

They always depolarise

250
Q

How do OFF bipolar cells respond when light hits the retina?

A

Hyperpolarise

251
Q

Which neurons input onto horizontal cells and which neurons do horizontal cells send output to?

A

Photoreceptors input to horizontal cells

Horizontal cells output to photoreceptors

252
Q

How do horizontal cells respond to light?

A

Hyperpolarise

253
Q

Which neurotransmitter do horizontal cells release in response to light?

A

Release GABA to photoreceptors

254
Q

What sort of signals do amacrine cells send?

A

Inhibitory cells that release inhibitory neurotransmitters glycine and GABA

255
Q

Which neuron in the retina fires action potentials?

A

ON ganglion cell depolarise and fire action potentials

256
Q

What is receptive field?

A

the area of retina that, when stimulated with light, changes cell membrane potential

257
Q

What protein do rods contain?

A

rhodopsin

258
Q

What protein do cones contain?

A

one of three different types of cone-opsins

259
Q

Which vitamin do opsins bind?

A

Vitamin A

260
Q

How do photoreceptors respond to dark?

A

cGMP gates sodium channels and allows continuous influx of sodium ions causing depolarisation

261
Q

How do photoreceptors respond to light?

A

Phosphodiesterase breaks down cGMP to GMP
Sodium channels close
Influx of sodium ceases
Cell becomes hyperpolarised and releases glutamate

263
Q

What creates the centre-surround phenomenon?

A

Some ganglion cells depolarise when light is shone on the centre of the receptive field while some ganglion cells hyperpolarise when light is shone on the peripheral part of receptive field

264
Q

What is the surround response?

A

Light shone on peripheral part of receptive field
Surround photoreceptors hyperpolarise releasing glutamate
Horizontal cells receive input, become hyperpolarised releasing GABA
GABA causes central photoreceptors to depolarise
Eventually ganglion cells become hyperpolarised

265
Q

What is the centre response?

A

Light shone to centre of receptive field
Photoreceptors hyperpolarise releasing glutamate
Causing the depolarisation of ON bipolar cells
Which causes depolarisation of ganglion cells

266
Q

What do M ganglion cells encode?

A

Motion

267
Q

What do P ganglion cells encode?

A

Colour vision and visual acuity

268
Q

What forms the optic chiasm and where does it lie?

A

fibres from left and right optic nerves combine to form optic chiasm
optic chiasm lies at the base of the brain, anterior to pituitary and is surrounded by the carotid arteries

269
Q

Where do nasal fibres of optic nerve cross?

A

Optic chiasm

270
Q

Which fibres pick up light from the temporal visual field?

A

All the cells at nasal half of retina

271
Q

Where do temporal fibres cross?

A

Temporal fibres from each eye travel through chiasm and don’t cross

272
Q

Which hemisphere interprets information from the left visual hemifield?

A

Right hemisphere

273
Q

Where do most ganglion cell axons involved in vision terminate?

A

Lateral geniculate nucleus in the thalamus

274
Q

How many layers are within the LGN and which cell types make up the layers?

A

6 layers within LGN:
Layers 1 and 2 are magnocellular layers
Layers 3-6 are parvocellular layers

275
Q

Where do M and P ganglion cell axons terminate in the LGN?

A

M cells target magnocellular layers of LGN (layers 1-2)

P cells target parvocellular layers of LGN (layers 3-6)

276
Q

T/F

Inputs from each eye mix at the LGN

A

False
Inputs from each eye are segregated
Mixing of info from each eye does not occur at LGN

277
Q

Where do LGN neurons project to?

A

Primary visual cortex in the occipital lobe around the calcarine fissure

278
Q

What are the optic radiations?

A

Ganglion cell axons that exit the LGN form white matter tracts which travel to occipital lobe

279
Q

Where is central vision encoded?

A

Encodes at the most posterior (occipital) part of the primary visual cortex

280
Q

Where is peripheral vision encoded?

A

More anterior part of the primary visual cortex, along the banks of the calcarine fissure

281
Q

If a lesion only affect vision in only 1 eye, what is the location of the lesion?

A

In the eye itself or in the ipsilateral optic nerve

before the optic chiasm

282
Q

If a lesion impairs vision in both eyes in some form or another, what is the location of the lesion?

A

The lesion may be at the chiasm or posterior to the chiasm

283
Q

What is the location of a lesion causing a bitemporal hemianopia - affecting opposite sides of the visual field?

A

At the optic chiasm

284
Q

What is the location of a lesion causing vision impairment in half the eye on the same side of both eyes - affecting same side of the visual field?

A

Optic tracts

285
Q

What is the location of a lesion which impairs vision in 1 quadrant of each eye on the same side of the visual field?

A

Optic radiations

286
Q

What is the general location of a lesion that impairs vision on the same side of the visual field?

A

Post chiasm

287
Q

What is the location of a lesion which causes visual impairment in half of each eye on the same side of the visual field but has macula sparing?

A

Visual cortex:

Macula sparing means normal central vision and is indicative of a vascular problem in the visual cortex

288
Q

What are melanopsin ganglion cells?

A

Intrinsically photosensitive ganglion cells in the retina

289
Q

What visual pigment do ipGCs contains?

A

melanopsin

290
Q

How do ipGCs respond to light?

A

Activation of melanopsin causes depolarisation of ipGCs

291
Q

Which muscle causes the pupil to constrict and what is its innervation?

A

Sphincter pupillae innervated by parasympathetic fibres which travel with CN III

292
Q

Which muscle causes pupil dilation and what is its innervation?

A

Dilator pupillae innervated by sympathetic fibres

293
Q

What is the pathway controlling pupil response?

A

ipGC process travels down optic nerve through the chiasm
Travels to optical pretectal nucleus in the midbrain
Then sends a process to each Edinger Westfal nucleus
A process from each Edinger Westfal nuclues heads back towards the eye which synapses at ciliary ganglion which travels to iris

294
Q

Where is the location of a lesion causing an afferent pupil defect?

A

Lesion can be from ipGC to pretectal nucleus in the midbrain

295
Q

What is the location of a lesion causing an efferent pupil defect?

A

Lesion can be located anywhere from the Edinger Westfal nucleus to the ciliary ganglion

296
Q

Where do ipGCs project to control circadian rhythm?

A

Suprachiasmatic nucleus in the hypothalamus

297
Q

What is the pain pathway for migraine and how are ipGCs involved?

A

Pain signal from dura is carried by trigeminal nerve to the brainstem and to the posterior nucleus of the thalamus
ipGCs also project to posterior thalamic nucleus
the posterior thalamic nucleus is light sensitive and becomes excited

299
Q

Where does superior oblique insert?

A

Inserts far behind the equator at an oblique angle to lateral rectus

300
Q

Where does the tendon of superior oblique run through?

A

The tendon runs through a fibrocartilage pulley (trochlea)

301
Q

What is the primary action of superior oblique?

A

Torsion - depression

302
Q

Where does inferior oblique insert?

A

Behind the equator, close to lateral rectus

303
Q

What is the primary action of inferior oblique?

A

torsion - elevation

304
Q

What is the effect of contracting superior rectus?

A

Superior rectus elevates the globe an also imposes a twisting action as well as a pulling action outward

305
Q

How to test superior rectus in isolation?

A

Abduct the eye, then look up

306
Q

How to test inferior rectus in isolation?

A

Abduct eye then look down

307
Q

How to test superior oblique in isolation?

A

Adduct eye then look up

308
Q

How to test inferior oblique in isolation?

A

Adduct eye then look down

309
Q

How to test medial rectus in isolation?

A

Adduct eye

310
Q

How to test lateral rectus in isolation?

A

Abduct eye

311
Q

Which extraocular muscle does trochlear nerve innervate?

A

Contralateral superior oblique

312
Q

Which brainstem centre is responsible for horizontal gaze control?

A

Pontine paramedian reticular formation

313
Q

Which brainstem centre is responsible for vertical gaze control?

A

Midbrain paramedian reticular formation

314
Q

What are the neuron types in the pontine reticular formation?

A

Burst neurons and omnipause neurons

315
Q

What are the functions of burst neurons?

A
  • Fire at high frequency just before a horizontal eye movement
  • excite ipsilateral abducens
  • suppress contralateral abducens
316
Q

What are the functions of omnipause neurons?

A
  • fire continuously during saccade except when burst neurons activated
  • GABAergic neurons that project to contralateral abducens nucleus
317
Q

What is the neural pathway for looking to the left?

A

Cortex signals to pontine paramedian reticular formation
In left eye,
Excitatory burst neurons input to left abducens nucleus to cause contraction of left lateral rectus and the right abducens nucleus sends inhibitory signals via medial longitudinal fasciculus to left oculomotor nucleus to cause relaxation of left medial rectus

In right eye,
Inhibitory burst neurons signal to right abducens nucleus to cause relaxation of right lateral rectus and the left abducens nucleus sends excitatory signals via MLF to right oculomotor nucleus to cause contraction of right medial rectus

318
Q

In what direction do frontal eye fields control saccades?

A

Contralateral direction

319
Q

Which UMNs drive brainstem gaze centres?

A

Frontal eye fields
Posterior parietal cortex
Superior colliculus
Basal ganglia

320
Q

What do semicircular canals detect?

A

Head position

321
Q

What do otolith organs detect?

A

Linear acceleration

322
Q

What is the pathway for the vestibular-ocular reflex when turning the head to the right?

A

Turning head right causes rotation of hair cells in right horizontal semicircular canal which excites right vestibular nucleus, and it causes opposite rotation of hair cells in left horizontal semicircular canal which sends inhibitory signals to left vestibular nucleus.

Right vestibular nucleus sends excitatory input to left abducens nucleus and right oculomotor nucleus and sends inhibitory input to right abducens nucleus:

Excitation of left abducens nucleus causes excitation of left lateral rectus leading to contraction, and excitation of right oculomotor nucleus via MLF leads to contraction of right medial rectus (indirect route)

Excitatory input to right oculomotor nucleus causes contraction of right medial rectus (direct route).

Inhibitory input to right abducens nucleus via right vestibular nucleus causes relaxation of right lateral rectus.

Right abducens nucleus also sends inhibitory input to left oculomotor nucleus to cause relaxation of left medial rectus.

Net result is eyes counteract the right-going head movement by moving in the opposite direction: lateral rectus of right eye and medial rectus of left eye relax and lateral rectus of left eye and medial rectus of right eye contract so that eye movements are left-going.

323
Q

What is parallel processing?

A

When cones are hyperpolarised by light, this hyperpolarising signal is communicated to both ON and OFF bipolar cells

329
Q

What are saccadic eye movement?

A

Fovea shifts rapidly to a new visual target

330
Q

What is the smooth pursuit eye movement?

A

Image of moving target remains on the fovea

331
Q

Which layer do M ganglion cells terminate in primary visual cortex?`

A

Layer 4C alpha

332
Q

Which layer do P ganglion cells terminate in the primary visual cortex?

A

Layer 4C beta

333
Q

Where does mixing on visual information occur?

A

Primary visual cortex, not the LGN

334
Q

Where do cells in layer 4C alpha project to?

A

Project to layer 4B

335
Q

What do the neurons in layer 4B respond to?

A

these neurons are directionally selective and only respond to bars of light that move in a particular direction. The stimulus must be moving.

336
Q

What is the dorsal stream of visual processing?

A

Info carried from M cell pathway from V1, V2 and V3 is carried to Area MT which processes object motion and location

337
Q

What are characteristics of Area MT?

A
  • neurons have large receptive fields
  • neurons respond to movement
  • majority of the neurons are directionally selective
  • direction-of-motion columns
338
Q

How is colour detected?

A

The colour information sent to the retina comes from all the cones combined. Detection of colour is based on relative response levels of each cone. Every cone reacts to a certain extent to each wavelength of light. Colour perception is dependent on comparison.

339
Q

How do P ganglion cells detect colour?

A

Some P ganglion cells are excited by red/green on their receptive field centre and others are excited by blue/yellow.

P ganglion cells that are excited by blue light directed at the centre of their receptive field and inhibited by yellow light directed at the periphery. When blue light hits the receptive field centre, blue cones become excited and hyperpolarise which excites ON bipolar cells nd causes them to depolarise. ON ganglion cells then become depolarised causing them to fire action potentials.
Info is carried to LGN and down to V1 by P ganglion cells.

340
Q

How are ON ganglion cells maximally inhibited?

A

P ganglion cells that are excited by red light will be maximally inhibited when green light is directed at the receptive field periphery and vice versa.

P ganglion cells that are excited by blue light will be maximally inhibited when yellow light is directed at the receptive field periphery and vice versa.

341
Q

What is the mechanism by which ganglion cells are maximally inhibited?

A

If green light is shone at the peripheral part of a P ganglion cell receptive field that is excited by red light, green cones in the periphery will be stimulated and hyperpolarise. Glutamate is sent to horizontal cells which respond by hyperpolarising and sending inhibitory signals to red cones in the receptive field centre. As a result, ganglion cells hyperpolarise and are maximally inhibited.

342
Q

What happens when light shines over the entire receptive field?

A

If light covers the entire receptive field, an in-between response is generated and the brain will delete the signals because it can only interpret maximal stimulation and maximal inhibition, nothing in between.

343
Q

Where is Area IT located?

A

Medial aspect of inferior temporal lobe

344
Q

What is a major input to Area IT?

A

Area V4

345
Q

What does Area IT process?

A

Object recognition - perception of faces

346
Q

What are the three groups of colour vision deficiency?

A

Monochromacy - having only 1 type of cone
Dichromacy - having only 2 functional cones
Anomalous trichromacy - having all 3 cones but one expresses abnormal pigment

347
Q

What is the ventral stream?

A

P pathway:
Info from P cells go down inferior part of temporal lobe to Area V4 which inputs to Area IT to process shape and colour (not motion)

348
Q

How is sound basically transmitted as a neural response?

A

Pinna localises sound
Sound travels through the external acoustic meatus to tympanic membrane which vibrates and moves auditory ossicles
Movement of the ossicles is transmitted to the oval window and the cochlea transforms the physical motion of the oval window into a neural response

349
Q

What is the function of the ossicles?

A

Matches impedance of air to impedance of fluid within inner ear

350
Q

How does the basilar membrane respond to sound waves?

A

Base is stiff and narrow and responds to high frequencies
Apex is wide and responds to low frequency
Basilar membrane is tonotopically coded - adjacent hair cells pick up increasing frequencies

351
Q

Where is the Organ of Corti and what does it do?

A

Sandwiched between basilar membrane and reticular lamina

Contains inner and outer hair cells which are the auditory receptors which transduce mechanical sound to neural impulses

352
Q

How do hair cells transduce neural impulses?

A

Shearing forces occurring across the tectorial membrane is transferred to stereocilia on the hair cells. Movement of hair bundle towards the kinocilium (tallest sterocilium) causes opening of potassium channels, depolarisation and opening of voltage-gated calcium channels leading to the release of glutamate. Hyperpolarisation of the hair bundle causes closure of potassium channels. Potassium ion concentration must be high in the endolymph of the scala media in order for potassium to flow into the cell

353
Q

How do inner hair cells compare to outer hair cells?

A

Inner hair cells are the sensory receptors whose nerve bundles project to brainstem nuclei
Outer hair cells receive efferent inputs from superior olivary complex in order to amplify movements of the basilar membrane

354
Q

How do outer hair cells respond to stimuli?

A

They change length in response to voltage change which accentuates the movement of the basilar membrane and amplifies the signal sent to inner hair cells.
When hair cells are depolarised (influx of potassium), the cell contracts and when the hair cells are hyperpolarised, the cell elongates

355
Q

How do certain drugs affect outer hair cells?

A

Certain antibiotics and high doses of aspirin are ototoxic. Antibiotics and cause a loss of hair cells and aspirin can inhibit length changes to outer hair cells. As a result, movement of basilar membrane is reduced by 100-fold and loss of hearing may occur

356
Q

What is the auditory pathways?

A

Sound mechanical vibration displaces hair cells within the cochlea causing voltage changes which is transmitted as release of glutamate to vestibulocochlea nerve. Cochlear nerve synapses at cochlear nucleus in medulla which sends inputs to superior olivary complex and travels through lateral lemniscus, inferior olive in midbrain, to medial geniculate nucleus in the thalamus which sends any input to auditory cortex

357
Q

What are the components of the superior olivary complex and what are the functions of each?

A

Lateral superior olive localises sound by measuring time delay
Medial superior olive localises sound by sensing intensity differences

358
Q

What is the Duplex theory?

A

There is a time difference that low frequency sound action potentials reach each ear which is detected by medial superior olive

There are intensity differences (loudness) between high frequency sound reaching each ear which is detected by lateral superior olives and trapezoid bodies

359
Q

How does auditory cortex process sound?

A

Neurons within auditory cortex are sensitive to sound frequency
Neurons are organised into columns which that cells within a column are tuned to same frequency
Receives excitatory input from one ear and inhibitory input from opposite ear
Complex sounds are asymmetrically represented in the hemispheres

Neuroscience (9 decks)

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