Neuro+ Flashcards
1
Q
Which cranial nerves do not arise from the brainstem?
A
Olfactory (CN1) and Optic (CN2)
2
Q
Which cranial nerves arise from the midbrain?
A
Oculomotor (CN3) arises from anterior midbrain and Trochlear arises from dorsal midbrain (CN4)
3
Q
Which cranial nerves arise from the pons?
A
Trigeminal (CN5) Abducens (CN6) Facial (CN7) Vestibulocochlear (CN8)
4
Q
Which cranial nerves arise from the medulla?
A
Glossopharyngeal (CN9) Vagus (CN10) Spinal accessory (CN11) Hypoglossal (CN12)
5
Q
- What is the name of Cn1?
- Where does it exit the skull?
- Sensory, motor or both?
A
Olfactory nerve
Cribriform plate of the ethmoid bone
Sensory - olfaction (sense of smell)
6
Q
- What is the name of Cn2?
- Where does it exit the skull?
- Sensory, motor or both?
A
Optic nerve
Optic canal
Sensory - vision
7
Q
- What is the name of Cn3?
- Where does it exit the skull?
- Sensory, motor or both?
A
Occulomotor
Superior orbital fissure.
Motor and parasympathetic.
8
Q
- What is the name of Cn4?
- Where does it exit the skull?
- Sensory, motor or both?
A
Trochlear.
Superior orbital fissure.
Motor
9
Q
- What is the name of Cn5?
- Where does it exit the skull?
- Sensory, motor or both?
A
Trigeminal - 3 branches: ophthalmic V1, maxillary V2, mandibular V3. Exit through Some Random ‘Oles.
V1 = superior orbital fissure - sensory
V2 = foramen rotundum - sensory
V3 = foramen ovale - sensory and motor (for mastication)
10
Q
- What is the name of Cn6?
- Where does it exit the skull?
- Sensory, motor or both?
A
Abducens
Superior orbital fissure
Motor
11
Q
- What is the name of Cn7?
- Where does it exit the skull?
- Sensory, motor or both?
A
Facial.
Internal acoustic meatus.
Both: sensory and motor and parasympathetic.
12
Q
- What is the name of Cn8?
- Where does it exit the skull?
- Sensory, motor or both?
A
Vestibulocochlear.
Internal acoustic meatus.
Sensory.
13
Q
- What is the name of Cn9?
- Where does it exit the skull?
- Sensory, motor or both?
A
Glossopharyngeal.
Jugular foramen.
Both: sensory and motor and parasympathetic.
14
Q
- What is the name of Cn10?
- Where does it exit the skull?
- Sensory, motor or both?
A
Vagus.
Jugular foramen.
Both: sensory and motor and parasympathetic.
15
Q
- What is the name of Cn11?
- Where does it exit the skull?
- Sensory, motor or both?
A
Spinal Accessory.
Jugular foramen.
Motor.
16
Q
- What is the name of Cn12?
- Where does it exit the skull?
- Sensory, motor or both?
A
Hypoglossal.
Hypoglossal canal.
Motor
17
Q
Which cranial nerves are parasympathetic nerves and where do they come from?
A
Cn 3, 7, 9 and 10, S2 -> 4
18
Q
- What does Cn1 innervate?
- What are it’s functions?
A
- Innervates: olfactory epithelium.
- Function: olfaction.
19
Q
- What does Cn2 innervate?
- What are it’s functions?
A
- Innervates: retina.
- Function: vision.
20
Q
- What does Cn3 innervate?
- What are it’s functions?
A
- Innervates: medial, superior and inferior rectus muscles and inferior oblique and levator palpebrae superioris.
- Motor function: movement of eyeball.
- Parasympathetic function: constriction and accommodation.
21
Q
- What does Cn4 innervate?
- What are it’s functions?
A
- Innervates: superior oblique.
- Functions: movement of eyeball.
22
Q
- What does Cn5 innervate?
- What are it’s functions?
A
- Sensory innervation: face, scalp, cornea, nasal and oral cavities, anterior 2/3 of tongue, dura mater.
- Motor innervation: muscles of mastication and tensor tympani.
- Sensory function: general sensation.
- Motor functions: open and close the mouth. Tenses tympanic membrane.
23
Q
- What does Cn6 innervate?
- What are it’s functions?
A
- Innervates: lateral rectus.
- Function: eye movement, abduction.
24
Q
- What does Cn7 innervate?
- What are it’s functions?
A
- Special sensory innervation: anterior 2/3 of tongue - taste.
- Motor innervation: muscles of facial expression and stapedius.
- Parasympathetic innervation: submandibular and sublingual and lacrimal glands.
- Sensory function: taste.
- Motor function: facial movement and tension of ossicles.
- Parasympathetic function: salivation and lacrimation.
25
- What does Cn8 innervate?
| - What are it's functions?
- Innervation: cochlea and vestibular apparatus.
| - Functions: hearing and proprioception of head and balance.
26
- What does Cn9 innervate?
| - What are it's functions?
- Sensory innervation: posterior 1/3 of tongue, middle ear, pharynx, carotid bodies.
- Motor innervation: stylopharyngeus.
- Parasympathetic innervation: parotid gland.
- Sensory functions: general sensation, taste, chemo/baroreception.
- Motor functions: Swallowing (larynx and pharynx are elevated).
- Parasympathetic function: salivation.
27
- What does Cn10 innervate?
| - What are it's functions?
- Sensory innervation: pharynx, larynx, oesophagus, external ear, aortic bodies, thoracic and abdominal viscera.
- Motor innervation: soft palate, larynx, pharynx.
- Parasympathetic innervation: CV, respiratory and GI systems.
- Sensory functions: general sensation.
- Motor functions: speech and swallowing.
- Parasympathetic functions: control over CV, respiratory and GI systems.
28
- What does Cn11 innervate?
| - What are it's functions?
- Innervation: trapezius and sternocleidomastoid.
| - Functions: movement of head and shoulders.
29
- What does Cn12 innervate?
| - What are it's functions?
- Innervation: intrinsic and extrinsic muscles of the tongue.
- Function: movement of the tongue.
30
How would you test CN1?
Ask patient to identify smell
31
How would you test CN2?
Visual acuity (use Snellen chart), pupillary light reflex, fundoscopy
32
How would you test CN3?
Pupillary light reflex
Stand 1m away and ask patient to follow your finger whilst you draw a H in the air. Ask about double vision, check for ptosis (eyelid drooping) & nystagmus (uncontrolled eye movements)
33
How would you test CN5?
Test sensory component: assess light touch on forehead V1, cheek V2 and jaw V3
Motor component: ask patient to clench teeth, feel bulk of masseter and temporalis bilaterally
34
How would you test CN4?
Innervates superior oblique,
Ask patient to look down and in
If damaged eye drifts upwards and patient has double vision
35
How would you test CN7?
Assess for symmetry in face at rest. Test facial expression by asking patient to: raise eyebrows, close their eyes tightly, blow out cheeks, smile, frown
36
How would you test CN8?
Weber’s test = place tuning fork in centre of forehead, should be heard equally in both ears
37
How would you test CN9?
Provides sensory supply to palate
| Test = gag reflex or touch arches of pharynx
38
How would you test CN10?
Provides motor supply to pharynx
Hoarse voice = vocal cord paralysis
Nasal voice = palate paralysis
Ask patient to say ‘aah’
1. Palate fails to rise = bilateral lesions
2. Uvula & palate not central and deviate to ‘normal’ side = unilateral paralysis
39
How would you test CN11?
Test Trapezius = ask patient to shrug shoulders
| Test Sternocleidomastoid = turn head against resistance
40
Which nerve supplies sensation and taste to the posterior 1/3rd of the tongue?
Glossopharyngeal nerve - CN9
41
How would you test CN12?
Ask patient to protrude tongue and move it from side to side. Damage to the nerve will cause paralysis of the IPSILATERAL half of the tongue - licks the lesion (tongue movement towards lesion)
42
Which part of the nervous system is responsible for the cranial nerves?
Peripheral nervous system because their axons extend beyond the brain. BUT not optic nerve!!
43
Which part of the nervous system is responsible for the optic nerve?
The second cranial nerve is not a true peripheral nerve but a tract of the diencephalon. Cranial nerve ganglia originated in the CNS.
44
Where do cranial nerves 3, 4, 5 & 6 exit the skull?
Superior orbital fissure
| CN5 = V2 maxillary branch exits in foramen rotundum and V3 mandibular branch exits via foramen ovale
45
Where do cranial nerves 7 and 8 exit the skull?
Internal acoustic meatus
46
Where do cranial nerves 9, 10 & 11 exits the skull?
The jugular foramen
47
How can you test CN9 and CN10 at the same time?
The gag reflex.
48
What are the branches of the facial nerve?
Temporal, zygomatic, buccal, mandibular, cervical
| Two Zebras Buggered My Cat
49
How does pouring warm or cold water into the internal acoustic meatus test the vestibulocochlear nerve?
It disrupts the movement of endolymph in the semicircular duct. This stimulates cristae hair cells (movement sensors). The vestibular nerve is now stimulated and via the oculogyric nuclei in the brainstem will cause nystagmus (involuntary eye movement).
50
When pouring water into the internal acoustic meatus to test the vestibular division of the vestibularcochlear nerve, does the pattern of nystagmus change with different water temperatures?
Yes! Remember - COWS
Cold water causes nystagmus in the opposite eye
Warm water will cause nystagmus in the direction of the same eye
51
What are the 2 main arteries that supply blood to the brain?
1. Vertebral arteries.
| 2. Internal carotid arteries.
52
Which arteries supply about 80% of blood to the brain?
The internal carotid arteries.
53
What are the vertebral arteries a branch of?
The subclavian arteries
54
Where do the vertebral arteries enter the skull?
Through the foramen magnum
55
What are the internal carotid arteries branches of?
The common carotids. Arise from bifurcation at the same level as the upper border of the thyroid cartilage.
56
What do the vertebral arteries supply?
The posterior cerebrum and the
| contents of the posterior cranial fossa.
57
Where do the internal carotid arteries enter the skull?
Through the carotid foramina
58
What are the terminal branches of the internal carotid arteries?
The middle and anterior cerebral arteries
59
What does the middle cerebral artery supply?
The lateral surface of the hemispheres.
60
What does the anterior cerebral artery supply?
The medial aspect of the hemispheres and the corpus callosum
61
What does the posterior cerebral artery supply?
The occipital lobe.
62
What do the two vertebral arteries form?
The basilar artery.
63
Where is a berry aneurysm likely to occur?
At branching points in the circle of willis, especially at the anterior communicating artery.
64
What is a berry aneurysm?
A sac-like out pouching that will progressively enlarge until it ruptures resulting in haemorrhage.
65
What are the two types of stroke?
1. Ischaemic.
| 2. Haemorrhagic (intracerebral or subarachnoid).
66
Which artery supplies 4/5ths of the corpus callosum?
Anterior cerebral artery
67
Which artery supplies 1/5th of the corpus callosum?
Posterior cerebral artery
68
What are the three main sinuses in the brain?
Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
69
Where do the superior sagittal sinus and the straight sinus converge?
At the confluence of sinuses
70
What forms the confluence of sinuses?
The superior sagittal sinus and the straight sinus.
71
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
72
Where do cerebral veins drain into?
Into dural venous sinuses.
73
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
74
What sinus does the great cerebral vein drain into?
The straight sinus
75
Where does the inferior sagittal sinus drain?
Into the straight sinus.
76
Where is the straight sinus located?
In the midline of the tentorium cerebelli.
77
Briefly describe the pathway of venous drainage starting at the great cerebral vein.
Great cerebral vein (along with the superior and inferior sagittal sinuses) drains into → straight sinus → transverse sinus → sigmoid sinus → internal jugular vein → jugular vein → brachiocephalic vein → SVC.
78
Structures pass through the cavernous sinus to enter the.......
orbit
79
Where is the only site in the body where an artery (internal carotid) passes completely through a venous structure?
The cavernous sinus
80
What vessels lie in the cavernous sinus?
OTOM CAT
Oculomotor nerve, Trochlear nerve, Ophthalmic branch of CNV, Maxillary branch of CNV, internal Carotid artery, Abducens nerve, Trochlear nerve.
- Cn 3, 4, 5(1), 5(2) and 6.
- Internal carotid artery.
81
Why is the cavernous sinus of clinical importance?
If this sinus is infected Cn 3, 4, 5(1), 5(2) and 6 and the internal carotid artery could be affected.
82
What are emissary veins?
Veins that allow the dural venous sinuses and veins outside the skull to communicate.
83
Which type of veins represent a possible route for infection to spread into the cranial cavity?
Emissary veins.
84
Where does venous blood in the brain collect?
Between the endosteal and meningeal layers of dura.
85
What are the five facial bones?
Zygomatic, maxilla, nasal, lacrimal and mandible
86
Anatomically, what are the two parts that the cranium is divided into?
Calvarium (roof)
| Cranial base
87
How many bones is the Calvarium made from?
Four bones: frontal bone, occipital bone and two parietal bones.
88
How many bones is the cranial base made from?
Six bones: frontal bone, ethmoid bone, sphenoid bone, temporal bone, parietal bone and the occipital bone
89
List the lobes of the brain.
1. Frontal lobe
2. Parietal lobe
3. Occipital lobe
4. Temporal lobe
5. Brainstem
6. Cerebellum
90
The cerebrum contains two cerebral hemispheres. What are they separated by?
The falx cerebri of the dura mater
91
Embryologically, what is the cerebrum derived from?
The prosencephalon
92
What is the corpus callosum?
A huge fibre bundle that connects the left & right hemispheres together
93
Frontal lobe: where is it located? What separates it from other lobes? What is is involved in?
- Most anterior part of the cerebrum
- Separated from the temporal lobe by the lateral sulcus and from the parietal lobe by the central sulcus
- Involved in motor function, problem solving, speech and writing, judgement, personality, impulse control and social and sexual behaviour
- Pre-frontal = personality
- Dominant hemisphere contains Broca's area
94
Temporal lobe: where is it located? What separates it from other lobes? What is is involved in?
- Sits beneath the temporal bone of the calvaria, inferior to the frontal and parietal lobes, from which it is separated by the lateral sulcus
- Accountable for memory and language and contains the primary auditory cortex, hippocampus, amygdala
- Wernicke’s area is located in the superior temporal gyrus of the left hemisphere
95
Occipital lobe: where is it located? What separates it from other lobes? What is is involved in?
- Is located at the posterior aspect of the brain, situated below the occipital bone
- It contains the primary visual and visual association cortex
- Function: Understanding visual images and meaning of written words
96
Parietal lobe: where is it located? What separates it from other lobes? What is is involved in?
Between the frontal lobe anteriorly and the occipital lobe posteriorly
It is separated from these lobes by the central sulcus and parieto-occipital sulcus
There are two parietal lobes, and the dominant lobe (normally the left) is important for perception, interpretation of sensory information and the formation of the idea of a complex, meaningful motor response.
The nondominant lobe (normally the right) is important for visuospatial functions.
Contains the primary sensory area
97
Where is a) the primary auditory cortex b) the primary visual cortex and c) the primary sensory area located in the brain?
```
A = temporal lobe
B = occipital lobe
C= parietal lobe
```
98
Where is Broca's area located and what is essential for?
Brodmann 44 - a region in the frontal lobe of the dominant hemisphere, usually the left, of the brain.
Linked to speech production (remember BP)
99
Where is Wernicke's area located and what is essential for?
Brodmann 22 - It is located in the temporal tobe and is (most commonly) in the left cerebral hemisphere
Is responsible for the comprehension of speech (remember WC)
100
What structure joins the two hemispheres of the cerebellum?
The vermis
101
How is the cerebellum separated from the occipital lobe?
By the tentorium cerebelli
102
How many lobes does the cerebellum have and what is its main function?
Three lobes; superior, middle & inferior
| It does the most complex of tasks and is essentially responsible for finely coordinated voluntary movement
103
Where does the cerebellum receive its input from?
Receives input from motor cortex, brain stem nuclei & sensory receptors
104
How is the cerebellum attached to the brainstem?
Through the superior, middle and inferior peundcles.
105
What do the superior peduncles do?
They connect the midbrain and the cerebellum and carry mostly efferent fibres.
106
What do the middle peduncles do?
They connect the pons and the cerebellum and they 'tell' the cerebellum about voluntary motor outputs.
107
What do the inferior peduncles do?
They connect the medulla and the cerebellum and convey muscle proprioception and vestibular inputs
108
Name the layers of the cerebellum from outer to inner.
1. Molecular layer - fibre rich
2. Purkinje cell layer
3. Granular layer - largest layer dominated by granular cells
109
Which are the two input fibres into the cerebellum?
1. Mossy fibres 2. Climbing fibres
110
Where do climbing fibres originate, how do they enter the cerebellum and which layer do they end in?
- Come from the olivocerebellar nuclei of the medulla
- Enter the cerebellum via the inferior cerebellar peduncle
- End in purkinje cell layer
111
Where do mossy fibres originate, how do they enter the cerebellum and which layer do they extend to?
- Come from the pons and cerebral cortex
- Enter via the middle cerebellar peduncle
- End in granular layer
112
Which axons carry all of the output from the cerebellum?
Purkinje cell axons.
113
Where do most of the purkinje cell axons go?
Most go to the dentate nucleus. They then pass into the superior cerebellar peduncle to decussate, and then travel to the thalamus and the red nucleus.
114
Are purkinje cell axons inhibitory or excitatory?
They are inhibitory (GABAergic). Thus, cerebellum inhibits activity in other places in the CNS.
115
Name 4 cerebellar nuclei.
1. Dentate.
2. Emboliform.
3. Globose.
4. Fastigial.
116
What is the affect on movement in cerebellar injury?
Movements are slow and uncoordinated.
117
What are some symptoms of cerebellar injury?
- Loss of coordination.
- Inability to judge distances.
- Intention tremor.
- Staggering, wide based walking.
- Weak muscles.
118
What is the only cranial nerve to emerge from the dorsal aspect of the brainstem?
The trochlear nerve (cn4)
119
What do the inferior cerebellar peduncles convey?
Ipsilateral muscle proprioception, balance and vestibular inputs - vestibulocerebellar tract and dorsal spinocerebellar tract. Also fibres from inferior olivocerebellar tract.
120
What do the middle cerebellar peduncles convey?
They send information from the primary motor cortex about the motor plan to the cerebellum - corticopontocerebellar tract.
121
What afferent signals do the superior cerebellar peduncles convey?
Ipsilateral information on proprioception and balance from the ventral spinocerebellar tract.
122
What efferent signals do the superior cerebellar peduncles convey?
Efferent signals from the dentate nucleus that go to the red nucleus and thalamus.
123
Which part of the brain produces instinctive emotional output, is responsible for emotional memory and is responsible for fear?
The amygdala
124
Name the parts of the brainstem.
1. Midbrain (mesencephalon)
2. Pons (metencephalon)
3. Medulla oblongata (myelencephalon)
125
Which cranial nerve nuclei are located in the brainstem?
All of the cranial nerve nuclei, except those associated with olfaction and vision (cn1, cn2)
126
What is the tectum?
```
The tectum (Latin: roof) is the dorsal (top) part of the midbrain (mesencephalon)
Contains the inferior and superior colliculus
```
127
What is the tegmentum?
Ventral part of the midbrain, located between cerebral aqueduct and the substantia nigra and forms the ‘floor’.
Includes the RED NUCLEUS
128
What are the 3 meningeal layers?
1. Dura mater (outermost).
2. Arachnoid mater.
3. Pia mater (inner most).
129
What are the 2 connective tissue sheets of dura mater?
1. Endosteal layer - lines the cranium.
| 2. Meningeal layer.
130
Name 3 locations where the dura mater folds inwards as dural reflections?
1. Falx cerebri.
2. Tentorium cerebelli.
3. Falx cerebelli.
131
Describe the dura mater.
Fibrous outer layer
Has two layers – the endosteal and the meningeal
For the most part the two layers are fused but sinuses are formed in spaces between these layers
132
What exists between the arachnoid and pia mater?
The subarachnoid space which contains CSF and arteries.
133
Describe the arachnoid mater.
Spaces exists between arachnoid and pia called subarachnoid cisterns/space (full of CSF)
Has arachnoid villi which are little protrusions that extend upwards through the dura into the sinuses – allow CSF to exit subarachnoid space
Avascular and not innervated
134
Describe the pia mater.
Indistinguishable with naked eye
Closely adherent to underlying tisuue
Forms part of the BBB – highly vascular
Fuses with ependymal cells of the choroid plexus in the ventricles
135
Which meningeal layers are vascular?
The dura and pia mater = highly vascularised.
| The arachnoid mater is avascular and not innervated!
136
Define meninges.
The membranous coverings of the brain and spinal cord. There are three layers known as the dura mater, arachnoid mater and pia mater.
137
What is the blood-brain barrier?
A semipermeable membrane separating the blood from the cerebrospinal fluid in the central nervous system and constituting a barrier to the passage of cells, particles, and large molecules.
138
Name the 3 elements that make up the blood-brain barrier.
1. Capillary endothelial cells.
2. Basement membrane.
3. Astrocytic end-feet.
139
Name some key features of the blood-brain barrier.
Capillary endothelial cells, continuous basement membrane, astrocyte end-feet, pericytes, endothelial tight junctions and specific transport proteins.
140
What are the parts of the brain that lack the blood-brain barrier called and give an example of one of these areas?
CIRCUMVENTRULAR ORGANS e.g. posterior pituitary - they are highly permeable need to be able to secrete hormones directly into the blood stream
141
How many vertebra are there?
7 cervical vertebra, 12 thoracic vertebra, 5 lumbar vertebra, 5 saccrum vertebra (fused), 4 coccyx vertebra (fused) = 33 vertebra in total
142
How many spinal nerves are there?
31 = 8 CERVCAL, 12 THORACIC, 5 LUMBAR, 5 SACRAL & 1 PAIR OF COCCYGEAL NERVES
143
Where do the spinal nerves exit the vertebral canal?
Through the intervertebral foramina
144
Where do the cervical segments of the spinal nerves exit?
Approx. 1 vertebra HIGHER their corresponding vertebra [EXCEPT C8, which below one vertebra]
145
Where do the thoracic segments of the spinal nerves exit?
1-2 vertebra BELOW their corresponding vertebra
146
Where do the lumbar segments of the spinal nerves exit?
3-4 vertebra BELOW their corresponding vertebra
147
Where do the sacral segments of the spinal nerves exit?
Around 5 vertebra BELOW
148
What type of nerves are spinal nerves?
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body
149
What do the dorsal roots of the spinal nerves carry?
Afferent (SENSORY) neurons & cell bodies in the dorsal root ganglion
150
What do the ventral roots of the spinal nerves carry?
Efferent (MOTOR) neurons & cell bodies in the grey matter Each nerve then divides to form a a small dorsal/posteriori ramus and a larger ventral/anterior ramus
151
What is C1 called?
The atlas
152
What is C2 called?
The axis
153
What is the odontoid peg?
A projection superiorly on C2 that provides an axis around which the neck can rotate. It represents the vertebral body of C1, which has fused with the body of C2.
154
Define spinal cord.
A major column of nervous tissue that extends from the medulla oblongata to the L1/L2 junction of the vertebral column
155
Where does the spinal cord end in an adult?
Between the L1/L2 junction.
156
Where does the spinal cord end in a newborn baby?
L3
157
When does the spinal cord run the entire length of the vertebral canal?
At 3 months of foetal life
158
What is the corda equina?
A bundle of spinal nerves and spinal nerve rootlets, consisting of the L2-L5 lumbar nerve pairs, the S1-S5 sacral nerve pairs, and the coccygeal nerve, that hang obliquely downwards below the termination of the spinal cord.
159
Describe the shape of the vertebral column.
Sinusoidal
160
Describe the movements of the vertebral column .
o Forward flexion - 40o
o Extension - 15o
o Lateral flexion - 30o
o Rotation - 40o
161
Where is flexion limited in the vertebral column?
In the thoracic area due to the presence of the ribcage
162
Which parts of the vertebral column is rotation maximal and minimal?
```
Maximal = thoracic region
Minimal = lumbar region
```
163
What shape is the vertebral column in the foetus?
C-shaped
164
After birth secondary curvatures with convexity develops in the cervical and lumbar regions. What action of the child initiates this process at each location.
Cervical region = when the child holds up their head
| Lumbar region = when the legs begin weight-bearing
165
What is the conus medullaris?
The tapered, lower end of the spinal cord. In the shape of a cone.
166
What is the filum terminale?
A fibrous strand that proceeds downwards from the apex of the conus medullaris.
167
What is the inferior colliculus responsible for?
Auditory processing
168
What is the superior colliculus responsible for?
Visual processing
169
What are afferents?
Axons taking information towards the central nervous system e.g. sensory fibres
170
What are efferents?
Axons taking information from the central nervous system to another location e.g. motor fibres
171
Define dermatome.
An area of skin with a sensory nerve supply from a single root of the spinal cord.
172
What is the dermatome for the thumb?
C6
173
What is the dermatome for the knee?
L3
174
What is the dermatome for the big toe?
L5
175
What is the dermatome for the nipple?
T4
176
What is the dermatome for the umbilicus?
T10
177
What is the dermatome for the small toe?
S1
178
What is the dermatome for the middle three toes?
L5
179
What is the dermatome for the ring and little finger?
C8
180
What is the dermatome for the index and middle finder?
C7
181
Where does the spinal cord end in the embryo?
It runs the entire length of the vertebral column.
182
Where would you insert a lumbar puncture needle?
At the L3/L4 level in the sub-arachnoid space in order to take CSF.
183
Where would you insert an epidural needle?
Between the dura mater and vertebrae in order to inject anaesthesia.
184
What type of joints are intervertebral discs?
Secondary cartilaginous joints (hyline & fibrous cartilage)
185
What are the two parts that make up the intervertebral discs?
1. The nucleus pulposus
| 2. The annulus fibrosus
186
What do the intervertebral discs function as?
1. Ligaments to hold the vertebrae together
| 2. Shock absorbers for the spine
187
What are the ANATOMICAL divisions of the nervous system?
1. The central nervous system (brain and spinal cord)
| 2. The peripheral nervous system (mainly cranial and spinal nerves that connect the CNS to the rest of the body)
188
What are the FUNCTIONAL divisions of the nervous system?
The peripheral nervous system can be subdivided into
1. The somatic nervous system
2. Autonomic nervous system
189
Briefly describe the somatic nervous system.
Associated with voluntary control of body movements via skeletal muscles
190
Briefly describe the autonomic nervous system.
A control system that acts unconsciously and regulates bodily functions - supplies smooth muscle and glands, and thus influences the function of internal organs.
191
What 3 categories can the autonomic nervous system be further divided into?
1. Sympathetic nervous system - FIGHT-OR-FLIGHT response.
2. Parasympathetic nervous system - stimulation of "REST-AND-DIGEST" or "FEED AND BREED”
3. Enteric nervous system- mesh-like system of neurones that governs the function of the gastrointestinal tract.
192
How do somatic motor neurones differ from autonomic motor neurones?
Somatic motor neurone leaves the spinal cord and synapses straight onto the effector. Autonomic motor neurones have a pre-ganglionic and post-ganglionic component and so synapse at the ganglia and then at the effector.
193
Name some of the features of somatic motor neurones.
Voluntary effectors = striated/skeletal muscles
Single motor neurone from spinal cord to target muscle
NT always stimulatory
ACh released at synapse
No firing at rest
Effector at rest is flaccid
Axons are well myelinated by Schwann cells, conducts impulses rapidly
194
Name some of the features of the autonomic motor neurones.
Involuntary effectors = smooth & cardiac muscle
Usually two neurones (pre-ganglionic and post-ganglionic) with synapse (ganglion) between spinal cord and target muscle
NT stimulatory or inhibitory
ACh and NE released at synapses
Baseline firing – speeds up when stimulated
Effector at rest has intrinsic tone
Conduction is slower due to thinly or unmyelinated axons
195
Define neurone
Basic cellular unit of the nervous system
196
Neurones account for 50% of the cells in the CNS, what accounts for the remaining 50%?
Glial cells - surround the soma (cell body), axon and dendrites of neurones and provide them with physical & metabolic support
197
What is the general structure of a neurone?
1) Cell body (soma) - genetic and metabolic centre
2) Axons - conducting systems of neurones, used to transmit information, myelinated with nodes of Ranvier
3) Dendrites - receive information is transmitted to cell body (soma) via dendrites and they create connections between neighbouring neurones.
198
What are the three functional classes of neurones?
1. Afferent - sensory
2. Efferent - motor
3. Interneurones - within the CNS
199
Which type of glial cells are found in the peripheral nervous system and NOT the central nervous system?
Schwann cells
200
What type of glial cells are the most numerous type of glial cells in the CNS?
Astrocytes
201
What is the tentorium cerebelli?
Tough dura mater that separates the occipital lobe from the cerebellum
202
What separates the frontal and parietal lobe?
Central sulcus
203
What separates the temporal lobe from the parietal and frontal lobes?
The lateral sulcus (sylvius fissure)
204
Where is the primary motor cortex located?
In the precentral gyrus of the frontal lobe
205
Where is the somatosensory cortex located?
In the postcentral gyrus of the parietal lobe
206
What is the homunculus?
An inverted somatotrophic representation of body in the motor and somatosensory cortex. The size of the area of the cortex is proportional to the degree of innervation to that part of the body.
207
What type of cells are the ventricles and and spinal cord lined by which regulate the production & flow of cerebrospinal fluid (CSF)?
Ependymal cells
208
What is the neuronal resting potential?
-70mV
209
How is neuronal resting potential maintained?
3Na+ are pumped out of the cell for every 2K+ pumped in. Both ions have to move against their respective concentration gradients, it is therefore an active transport process and requires ATP. There are many Na+/K+ transport pumps.
210
In neuronal resting potential, what are the relative concentrations of potassium and sodium inside/outside the cell?
High intracellular K+ concentration
| High extracellular Na+ concentration.
211
Describe the sequence of events in generating an action potential.
1. Impulse reaches axon, causing partial depolarisation
2. -60mv threshold reached → Na+ channels open
3. Influx of Na+ into the cell → depolarisation
4. +30mV threshold reached → Na+ channels closes and K+ channels open
5. Efflux of potassium out of the cell → repolarisation
6. Hyperpolarisation → potential becomes more negative to prevent another impulse
7. Na/K+ pump returns ions to original concentration.
212
What is neuronal threshold potential for sodium channels to open?
-60mV
213
What is neuronal threshold potential for sodium channels to close and potassium channels to open?
+30mV
214
What is hyperpolarisation?
When the charge in the neurone is more negative than it was at it's resting potential (>-70mV). It is caused by slow potassium channels.
215
What are the 2 components of a refractory period?
The absolute refractory period which is followed by the relative refractory period
216
How long does the refractory period last?
5-10ms
217
What is the absolute refractory period?
Occurs during the period when the voltage-gated Na+ channels are either already open or have proceeded to their inactivated state– so a second stimulus, no matter how strong, will not produce a second action potential
218
What is the relative refractory period?
Follows the absolute refractory period and is an interval whereby a second action potential can be produced – but only if the stimulus strength is considerably greater than usual
219
What is saltatory conduction?
Is the propagation of action potentials along myelinated axons that leap from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
220
What two main factors do propagation speeds depend on?
1. Fibre diameter
| 2. Myelination
221
Why do larger fibre diameters increase propagation speeds?
A larger fibre offers less internal resistance to local current meaning adjacent regions of the membrane are able to reach threshold faster
222
Why do myelinated axons have greater propagation speeds than non-myelinated axons?
Because there is less “leakage” of charge across the myelin meaning a local current can spread faster along an axon
Also, the concentration of Na+ channels in the myelinated region of the axon is low. Therefore, action potentials only occur at the nodes of Ranvier, where the myelin coating is interrupted and the concentration of voltage- gated Na+ channels is high
223
What are nodes of Ranvier?
A gap in the myelin sheath of a nerve, between adjacent Schwann cells that serves to facilitate the rapid conduction of nerve impulse
224
Define synapse.
An anatomically specialised neuronal junction between two neurones at which the electrical activity in a presynaptic neurone influences the electrical activity of a postsynaptic neurone. Involved in the transmission of electric nerve impulses between two neurones.
225
What is the function of myelin?
Insulates and allows rapid conduction of action potentials along an axon.
226
Neurones communicate via 2 types of synapses. What are they?
1. Chemical (majority)
| 2. Electrical
227
Describe electrical synapses.
There is a direct physical connection between the plasma membranes of the presynaptic and postsynaptic neurones, which are called a gap junctions
Communication via electrical synapses is extremely rapid
228
Describe chemical synapses.
The presynaptic and postsynaptic neurones are separated by a SYNAPTIC CLEFT which prevents direct propagation of the current from the presynaptic neurone to the postsynaptic cell
Instead, signals are transmitted across the synaptic cleft by means of a chemical messenger known as a neurotransmitter which is released by the presynaptic axon terminal.
229
Do electrical synapses use neurotransmitters?
No! There is a physical connection between the plasma membranes of the pre-synaptic and post-synaptic neurones (gap junctions)
230
Define neurotransmitter.
A type of chemical messenger which transmits signals across a chemical synapse from one neurone to another "target" neurone, muscle cell, or gland cell.
231
Explain the process of neurotransmitter release.
1. Calcium ion channels open when an action potential reaches the pre- synaptic terminal
2. Ca2+ ions cause vesicles (containing neurotransmitter) to fuse with the presynaptic cell membrane and discharge their contents
3. Neurotransmitter diffuses across the synaptic cleft and attaches to receptor sites on the post-synaptic membrane
4. Neurotransmitter binding - post synaptic sodium channels open = post synaptic depolarisation
232
Define neuromodulator.
A subset of neurotransmitter and a messenger released from a neurone in the CNS or PNS that affects groups of neurones, or effector cells that have the appropriate receptors.
233
Define neuromodulation.
The process by which nervous activity is regulated by way of controlling the physiological levels of several classes of neurotransmitters.
234
Give 2 examples of fast neurotransmitters. Do fast neurotransmitters have short or long lasting effects?
- Ach, GABA.
| - Short lasting effects.
235
Give 3 examples of neuromodulators. Do neuromodulators have short or long lasting effects?
- Dopamine, serotonin, noradrenaline.
| - Long lasting effects.
236
What is a neuromuscular junction?
A chemical synapse formed by the contact between a motor neurone and a muscle fibre.
237
What are the three main neurotransmitters in the CNS?
1. Glutamate (excitatory)
2. GABA (inhibitory)
3. Dopamine (modulatory)
238
What are the two main neurotransmitters in the PNS?
1. Noradrenaline (sympathetic)
| 2. Acetylcholine (parasympathetic)
239
What are the two types of Ach receptor?
1. Nicotinic (found at neuromuscular junction)
| 2. Muscarinic
240
What are the 5 fundamental processes of neurotransmission/ synaptic transmission?
1. Manufacture
2. Storage - vesicles
3. Release - action potential
4. Interaction with post-synaptic receptor - diffusion across synapses
5. Inactivation - break down or re-uptake
241
Explain the concept of synaptic integration.
In most neurones, one excitatory synaptic event by itself is NOT enough to reach threshold in the postsynaptic neurone
Thus, an action potential can only be generated by the combined effects of many excitatory synapses
These combined effects can be achieved by two means: temporal and spatial summation
242
What is spatial summation?
Impulses from multiple neurones cause depolarisation
243
What is temporal summation?
Multiple impulses from one neurone cause depolarisation
244
With reference to axonal neurotransmission, how do local anaesthetics prevent pain from being felt?
They block NA channels thereby preventing the neurones from depolarising meaning threshold isn't met and thus no action potential is developed to be propagated
This results in pain relief since pain isn't transmitted
245
In the CNS which cells form myelin?
Oligodendrocytes
246
In the PNS which cells form myelin?
Schwann cells
247
Define upper motor neurone.
A neurone that is located entirely in the CNS. Its cell body is located in the primary motor cortex and it synapses onto a lower motor neurone.
248
Define lower motor neurone.
A neurone that carries signals to effectors. The cell body is located in the brain stem or spinal cord. Directly innervates the muscles to produce movement.
249
Define motor unit.
An ALPHA MOTOR NEURONE (type of spinal lower motor neuron) and all of the EXTRAFUSAL skeletal muscle fibres it innervates
250
Define motor end plate.
Connection between the synapse and muscle fibre.
251
Define motor pool.
All individual motor neurones that innervate a single muscle.
252
Which CN nerve innervates tensor tympani?
CN 5
253
Which type of neurones account for the majority of neurones and are located entirely within the CNS?
Interneurones
254
True or false: all neuromuscular junctions are excitatory??
True!!
255
Which CN nerve innervates stapedius?
CN 7
256
Where are Cn 1 nuclei located?
Olfactory bulb.
257
Where are Cn 2 nuclei located?
Lateral geniculate body.
258
How does the cerebellum control coordination, precision and timing of movements?
It compares the brain's intentions with actual actions and makes any necessary modifications.
259
Which type of neurones innervate extrafusal fibres (the highly contracting fibres that supply the muscle with its power)?
Alpha motor neurons
260
Which type of neurones innervate intrafusal fibres (fibres that only contract slightly)?
Gamma motor neurons
261
What type of receptors do muscle spindles contain?
Stretch receptors that monitor muscle LENGTH & rate of change of muscle length
262
What type of neurones innervate muscle spindles?
Gamma motor neurones.
263
What are muscles spindles composed of?
Intrafusal fibres. (They are embedded in muscle - extrafusal fibres).
264
What type of receptors do golgi tendon organs contain and what do they detect?
Mechanoreceptors that measure changes in tension of a muscle.
265
What nerve fibres innervate golgi tendon organs?
Afferent type 1b sensory nerve fibres (inhibitory).
266
Muscle spindles have two types of stretch receptor. What are they called?
1. Nuclear chain fibres (respond to how much the muscle is stretched)
2. Nuclear bag fibres (respond to how much the muscle is stretched and the speed at which it is stretched)
267
Define muscle tone.
The degree of contraction of a muscle or the proportion of motor units that are active at any one time
268
What are golgi tendon organs?
Specialised receptors that are located between the muscles and the tendons.
269
What are some of the characteristics of slow twitch fibres? What are they used for?
Innervated by small motor neurones and generate less force than the fast-twitch fibres, but they are able to maintain these levels of force for long periods.
Used for maintaining posture and making other low-force movements.
270
Fibres that are innervated by intermediate motor neurones and generate more force than slow-twitch fibres, but they are not able to maintain the force as long as the slow-twitch fibres, are called what?
Fast twitch, fatigue resistant fibres
271
What are some of the characteristics of fast twitch, fatiguable fibres? When are they used?
Innervated by the largest motor neurones, produce large amounts of force but fatigue VERY quickly.
Used when needing to generate a burst of large amounts of force, such as in an escape mechanism.
272
With reference to motor neurones, explain the size principle and the law on which it is based.
States that with increasing strength of input onto motor neurones, smaller motor neurones are recruited and fire action potentials before larger motor neurones are recruited.
Why? Ohm's Law - a small amount of synaptic current will be sufficient to cause the membrane potential of a small motor neurone to reach firing threshold, while the large motor neurone stays below threshold.
273
Define reflex.
An action that is performed without conscious thought as a response to a stimulus. Unlearned and instinctive: unconditioned responses.
274
What is a reflex arc?
A neural pathway that controls a reflex.
275
What are the main components of a reflex arc?
1. A receptor – muscle spindle
2. An afferent fibre – muscle spindle afferent (sensory) axon
3. Integration centre – lamina of spinal cord
4. An efferent fibre - alpha- motoneurones
5. An effector – muscle
276
What is the response of golgi tendon organs if they detect a change in tension?
They inhibit alpha motor neurones to prevent muscle contraction if the force gets too great.
277
What is the stretch reflex?
A very simple, monosynaptic reflex. If a muscle is stretched it responds by contracting e.g. knee jerk
278
What is the function of the stretch reflex?
A protective measure for the muscles, to prevent tearing. The muscle spindle is stretched and the impulse is also immediately received to contract the muscle, protecting it from being pulled forcefully or beyond a normal range
279
Briefly describe the stretch reflex.
The muscle is stretched and intrafusal muscle fibres are stimulated -> sends afferent impulses along 1a neurones -> alpha motor neurone -> efferent impulses to extrafusal muscle fibres -> contraction.
280
What makes the stretch reflex different to all other reflex arcs?
They are MONOSYNAPTIC - the afferent fibres synapse directly with the motor neurones without any interneurones.
All other reflex arcs are are POLYSYNAPTIC - they have at least one interneurone, and usually many, between the afferent & efferent neurones.
281
What is the withdrawl reflex?
Polysynaptic reflex that occurs in response to noxious (usually painful) stimulation
282
Briefly describe the withdrawal reflex.
The limb is withdrawn from noxious stimuli. Afferent fibres synapse on motor neurones in spinal cord. The response is ipsilateral flexion (same side as noxious stimuli) and contralateral extension.
283
Withdrawal reflex: what does reciprocal innervation of antagonistic muscles explain?
It explains why the contraction of flexor muscles induces the relaxation of extensor muscles; this permits the execution of smooth movements.
284
Explain the crossed-extensor reflex element of the withdrawl reflex.
The stimulus causes the opposite response on the contralateral leg; motor neurones to the extensors are activated while the flexor muscle motor neurones are inhibited. This enables the contralateral leg to the support the body’s weight as the injured foot is lifter by flexion.
285
Define pain.
An unpleasant sensory and emotional experience associated with actual potential tissue damage or described in terms of such damage.
286
Define acute pain.
Short term pain of less than 12 weeks
287
Define chronic pain.
Continuous long-term pain of more than 12 weeks
288
Define nociceptive pain.
Pain that arises from actual or threatened damage to non- neuronal tissue and is due to the activation of nociceptors
Used in conjunction with a normally functioning somato-sensory system
289
Define neuropathic pain.
Pain initiated or caused by a primary lesion/dysfunction of the nervous system e.g. due to spinal nerve root compression
290
How many neurones are there between the sensory receptor located in the periphery and the perception of sensation at the level of the cerebral cortex ?
Three. First order (primary afferent), second order and third order neurones.
291
What are tonic receptors?
Slow adapting receptors. They will respond to the stimulus as long as it persists and produce a continuous high frequency of action potentials.
292
What are phasic receptors?
Rapidly adapting receptors. They will respond quickly to stimuli but stop responding upon continual stimulation. The receptor remains sensitive to a change in stimulus energy or removal of the stimulus.
293
What are nociceptors?
Phasic receptors, which respond to noxious stimuli (stimuli that would cause tissue injury if they were to persist) and result in the sensation of pain.
294
What are the four subcategories of nociceptors?
Mechanical – stimulated by the distension of skin (stretch) and pressure e.g. in inflammation
Thermal – stimulated by extremities of temperature
Chemical – stimulated by exogenous and endogenous chemical agents, such as prostanoids, histamines etc.
Polymodal – can respond to more than one stimuli (most C fibres are polymodal)
295
What type of fibres transmit pain?
Alpha-delta fibres and C fibres.
296
What are the characteristics of alpha-delta fibres?
```
Carries fast pain information
Myelinated with nodes of Ranvier
Primary afferent neurone terminals release glutamate as neurotransmitter
Diameter - 1-5 micrometres
Medium conduction speed
```
297
What are the characteristics of type C fibres?
Carries slow pain information
Primary afferent neurone terminals release glutamate and substance P as neurotransmitters
Diameter - 0.2-1.5 micrometres
Slowest conduction speed
298
What is substance P? What type of pain is it involved in transmitting?
Peptide neurotransmitter involved in pain transmission, it is also a vasodilator and remains bound to receptors for a longer time thereby transmitting long-lasting pain.
299
What are mechanoreceptors?
Located in joint capsules, ligaments, tendons, muscle and skin, and respond to deformation by the means of pressure, touch, vibration or stretch.
300
What are the tonic receptors present in skin, near the border of the dermis and epidermis, that respond to pressure and help to differentiate texture and shape of objects called?
Merkel’s discs
301
What are the phasic receptors, consisting of Aβ fibres, they enable two-point discrimination (fine touch) called?
Meisseners corpuscles
302
What are the largest category of mechanoreceptors called? What do they respond to?
Pacinian corpuscles and they respond to pressure changes and vibration.
303
What are Ruffini end-organ? Where are they located and what do they respond to?
These are tonic receptors present in the dermis and respond to stretch.
304
What are thermoreceptors?
Phasic receptors found within the skin, liver, skeletal muscle and hypothalamus that respond to changes in temperature.
Warm temperatures = C fibres
Cold temperatures = C and alpha-delta fibres
305
What is the difference between analgesia and anaesthesia?
```
Analgesia = the selective suppression of pain with-out effects on consciousness or other sensations
Anaesthesia = the uniform suppression of pain - NO PAIN IS FELT AT ALL, and sometimes consciousness is lost
```
306
What is the Melzack-Wall Pain Gate?
States that non-painful input closes the “gate” to painful input, thereby preventing pain sensation from travelling to the somatosensory cortex to be perceived and thus felt
Non-noxious stimuli can prevent pain as the large fibres can override the small pain fibres.
307
What concept is a physiological explanation for why 'rubbing it better' can help?
Melzack-Wall Pain Gate.
308
Where in the brain does pain reach consciousness?
In the thalamus.
309
What part of the brain is involved in our emotional response to pain?
The cingulate gyrus.
310
Which part of the brain contributes to the subjective perception of pain and is where the degree of pain is judged?
The insula
311
Where is the insula located?
Deep in the lateral sulcus.
312
Where is substance P released and the primary control centre of the descending pain pathway?
The periaqueductal grey matter
313
Where is substance P released and the primary control centre of the descending pain pathway?
The periaqueductal grey matter
314
Stimulation of which part of the brain can result in profound analgesia? Why?
The periaqueductal grey matter.
Contains opioid receptors that when activated, result in a reduction in PRE-SYNAPTIC neuronal sensitivity (thereby reducing Substance P release) which in turn results in reduced pain sensation.
315
What are the 3 primary vesicles?
1. Prosencephalon (forebrain).
2. Mesencephalon (midbrain).
3. Rhombencephalon (hindbrain).
316
When can the 3 primary vesicles be identified?
By the 5th week of embryonic development
317
What are the sub-divisions of the prosencephalon?
- Telencephalon.
| - Diencephalon.
318
What are the sub-divisions of the rhombencephalon?
- Metencephalon
| - Myelencephalon
319
How many secondary vesicles are they? What are they named?
Five.
1. Telencephalon
2. Diencephalon
3. Mesencephalon
4. Metencephalon
5. Myelencephalon
320
By which week of embryonic development have the secondary vesicles developed?
7th week
321
What is a morula?
A solid ball of 16 cells (blastomeres) that the ovum develops into following fertilisation
322
Briefly describe the process of blastulation.
Process in which the morula develops into a blastula (more than 16 cells) with a fluid cavity in the middle called a blastocele
323
What is gastrulation?
The process in which a single layer blastula develops into tri-laminar disc (gastrula).
324
What are the layers of the trilaminar disc?
1. Endoderm (most internal)
2. Mesoderm
3. Ectoderm (most external)
325
What do each of the layers of the trilaminar disc form?
1. Endoderm = lining of the gut and other internal organs
2. Mesoderm = muscle, the skeletal system, and the circulatory system
3. Ectoderm = skin, brain, and nervous system
326
What is the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube called?
Neurulation
327
From which layer of the tri-laminar disc is the neural tube formed from?
Ectoderm
328
Describe how the neural tube is formed.
Notochord in mesoderm signals the ectoderm to form a thickened neural plate. Mitosis forms a neural groove. There are neural folds either side of the groove. These fuse at the midline forming the neural tube.
329
What are the pluripotent stem cells that lie within the neural folds?
Neural crest cells
330
What do neural crest cells develop into?
Schwann cells, pigment cells, adrenal medulla, dorsal root ganglia, Cn 5, 7, 9 and 10.
331
When should the neural tube fuse?
By the end of the 4th week
332
What vitamins are needed to ensure the neural tube fuses.
B9 (folic acid) and B12.
333
Define neural tube.
A tube formed by the closure of ectodermal tissue in the early vertebrate embryo that later develops into the brain, spinal cord, nerves, and ganglia
334
What are the derivatives in the adult brain of the Telencephalon?
Cerebral hemisphere & Lateral ventricles
335
What are the derivatives in the adult brain of the Diencephalon?
Thalamus, Hypothalamus & Third ventricle
336
What are the derivatives in the adult brain of the Mesencephalon?
Midbrain (colliculi) & Aqueduct
337
What are the derivatives in the adult brain of the Metencephalon?
Cerebellum, Pons & Upper part of fourth ventricle
338
What are the derivatives in the adult brain of the Mylencephalon?
Medulla oblongata & Lower part of fourth ventricle
339
What do the rostral (superior) and caudal (inferior) parts of the neural tube develop into? Which part grows faster?
```
Rostral = brain and CNS (grows faster!)
Caudal = spinal cord
```
340
Which neonatal reflex is the only permanent reflex?
Blinking reflex = flash of light/puff of air = closes eyes
341
What type of sensation is present at 19 weeks?
C-fibre connection (noxious (painful) stimuli)
342
When does the dorsal root ganglion connect to the spinal cord? Does it result in nociceptive pain?
From 8 weeks
| No, is non- noxious (i.e. no pain is detected)
343
Where do connections develop in an embryo of 24 weeks?
Connections from the thalamus to the cortex
344
Describe the Babinski reflex in terms of stimulation, response and point of disappearance.
Sole of foot stroked
Fans toes out and twists foot in
9m-1y
345
Describe the grasping reflex in terms of stimulation, response and point of disappearance.
Palms touched
Grasps tightly
1y
346
Describe the rooting reflex in terms of stimulation, response and point of disappearance.
Cheek stroked, side of mouth touched
Turns towards source, opens mouth and sucks
3-4 m
347
Describe the tonic-neck reflex in terms of stimulation, response and point of disappearance.
Placed on back
Makes fists and turns head to the right
2m
348
Describe the swimming reflex in terms of stimulation, response and point of disappearance.
Placed face down in water
Makes coordinated swimming movements
6-7m
349
What are neonatal reflexes?
Inborn behavioural patterns that develop during uterine life. They should be fully present at birth and are gradually inhibited by higher centres in the brain during the first three to 12 months of postnatal life
350
Where is CSF produced?
Produced by ependymal cells in the choroid plexuses of the lateral ventricles (mainly)
351
Where does CSF circulate?
Circulates through the subarachnoid space (around the brain and spinal cord) and within ventricles
352
What is CSF absorbed by?
Absorbed via arachnoid granulations (VILLI) e.g. in the superior sagittal sinus
353
How many choroid plexuses are there in the brain?
Four, one in each of the ventricles.
354
Approximately how much CSF do we have?
120ml
355
Name 4 substances contained within the CSF.
1. Protein.
2. Urea.
3. Glucose.
4. Salts.
356
What is hydrocephalus?
An accumulation of CSF in the ventricular system. Often due to a blockage in the cerebral aqueduct.
357
How many ventricles are there in the brain?
Four: lateral (paired), third ventricle, fourth ventricle.
358
How do the ventricles and the subarchnoid space connect?
Via cisterns.
359
Embryologically, what is the ventricular system is derived from?
The lumen of the neural tube
360
Where is the location of the third ventricle?
Between the right and the left thalamus
361
Where are the lateral ventricles formed in the embryo?
Telencephalon.
362
Where is the 3rd ventricle formed in the embryo?
Diencephalon.
363
Where is the 4th ventricle formed in the embryo?
Rhombencephalon.
364
Where is the 4th ventricle situated?
It lies within the brainstem, at the junction between the pons and medulla oblongata.
365
What is the function of the cerebral aqueduct (of Sylvius) and where is it located?
Connects the third ventricle to the fourth and contains CSF. It is located within the midbrain.
366
What is the name of the matter that surrounds the cerebral aqueduct?
Periaqueductal grey matter
367
What are the three sites that CSF can leave the 4th ventricle and enter the subarachnoid space?
1. The foramen of Magendie (median aperture)
2. The left foramen of Luschka (lateral aperture)
3. The right foramen of Luschka (lateral aperture)
368
Name 3 functions of CSF.
1. Protection – acts as a cushion for the brain
2. Buoyancy – by being immersed in CSF, the net weight of the brain is reduced. This prevents excessive pressure on the base of the brain.
3. Chemical stability – allows for proper functioning of the brain, e.g. maintaining low extracellular K+ for synaptic transmission.
369
The lateral ventricles are connected to the third ventricle by.....
The interventricular foramen of Monro
370
Describe the flow route of CSF
Choroid plexus → lateral ventricle → interventricular foramen of Monro → 3rd ventricle → cerebral aqueduct of sylvius → 4th ventricle → two foramen of Luschka → one foramen of magendie → subarachnoid space → the arachnoid granulations → dural sinus → venous drainage
371
Name 4 ascending spinal pathways.
1. Dorsal column medial lemniscus
2. Spinothalamic.
3. Spinocerebellar.
4. Spinoreticular.
372
What sensations does the Dorsal Column Medial Lemniscus pathway convey?
Fine touch, vibration, 2-point discrimination and proprioception.
373
What sensations does the spinothalamic pathway convey?
```
Anterior = crude touch and pressure
Lateral = pain and temperature
```
374
What is the function of the spinocerebellar tracts?
They carry unconscious proprioceptive information to the ipsilateral cerebellum.
Help with balance and co-ordination.
375
What sensation does the spinoreticular tract convey?
Deep/chronic pain.
376
Describe the dorsal column medial lemnicus pathway.
Fine sensation is detected by touch or proprioception receptors.
Afferent signals are carried along 1st order neurones to the dorsal columns and up to the medulla where they synapse.
2nd order neurones decussate in the medulla and travel up to the thalamus where they synapse.
3rd order neurones then travel through the internal capsule to the somatosensory cortex.
377
Where does the dorsal column medial lemnicus pathway begin and end?
```
Begins = sensory organ with touch/proprioception receptors
Ends = primary somatosensory cortex on the opposite side of the stimulus
```
378
Where do first order neurones from the DCML pathway synapse?
Signals from the upper limb (T6 and above) = synapse in the nucleus cuneatus of the medulla oblongata
Signals from the lower limb (below T6) = synapse in the nucleus gracilis of the medulla oblongata.
379
Which dorsal column would an afferent signal from the upper limb use?
The cuneate fasciculus (lateral part of dorsal column). They then synapse at the cuneate nucleus of the medulla.
380
Which dorsal column would an afferent signal from the lower limb use?
The gracile fasciculus (medial part of dorsal column). They then synapse at the gracile nucleus of the medulla.
381
Where do neurones decussate in the DCML pathway?
Lower medulla to form medial lemniscus
382
Where does the spinothalamic pathway begin and end?
```
Begins = nociceptors / thermoreceptors in spinal cord
Ends = primary somatosensory cortex
```
383
Describe the spinothalamic pathway
Nociceptors or thermoreceptors detect pain, temperature or crude touch.
1st order neurones carrying these signals enter the spinal cord and ascend 2-3 spinal levels before synapsing in the dorsal horn of grey matter.
2nd order neurones decussate either through the anterior or lateral tracts and then travel up to the thalamus where they synapse.
3rd order neurones travel through the internal capsule to the primary somatosensory cortex.
384
Where do fibres of the spinothalamic tract decussate?
At level of entry or 2-3 levels above.
385
What sensations is the lateral spinothalamic tract responsible for?
Pain and temperature
386
What sensations is the anterior spinothalamic tract responsible for?
Crude touch and pressure
387
What is the function of the spinocerebellar tracts?
Unconscious proprioceptive information from lower limbs to ipsilateral cerebellum.
388
Where do the spinocerebellar tracts begin and end?
```
Start = golgi organs and muscle stretch organs
End = cerebellum
```
389
What are the subdivisons of the spinocerebellar tracts?
1. Posterior (dorsal) spinocerebellar tract
| 2. Anterior (ventral) spinocerebellar tract
390
Through which peuncles do the posterior (dorsal) spinocerebellar tract enter the cerebellum?
Through the INFERIOR cerebellar peduncles
391
Through which peuncles do the anterior (ventral) spinocerebellar tract enter the cerebellum?
Through the SUPERIOR cerebellar peduncles
392
Where do fibres decussate in the spinocerebellar tracts?
Posterior/dorsal - they don't!
| Anterior/ventral - cross in spinal cord before entering tract and then cross again within cerebellum (double cross)!!
393
Name 5 descending pathways.
1. Corticospinal.
2. Vestibulospinal.
3. Rubrospinal.
4. Tectospinal.
5. Reticulospinal.
394
For the DCML and spinothalamic pathway, how many neurones does it take to get from the sensory receptors to the somatosensory cortex?
Three
395
Where in the thalamus do the DCML and spinothalamic tracts synapse?
In the ventral posterio-lateral division (VPL) of the nucleus of thalamus.
396
What descending pathways are described as pyramidal?
Corticospinal and corticobulbar tracts - responsible for voluntary control.
397
What descending pathways are described as extrapyramidal?
Vestibulospinal, rubrospinal, tectospinal, reticulospinal - responsible for involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion.
398
Are there any synapses within the descending pathways?
No. At the termination of the descending tracts, the neurones synapse with a lower motor neurone. (All the neurones within the descending motor system are UMNs).
399
What are the corticospinal tracts responsible for?
The control of voluntary muscles. Anterior - axial (trunk) muscles. Lateral - limb muscles.
400
Where do the corticospinal tracts begin and end?
Start: motor cortex
End: lower motor neurones
401
What are the two subcategories of the corticospinal tract?
Anterior corticospinal tract and lateral corticospinal tract.
402
Describe the lateral corticospinal tract.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the medullary pyramids. 90% decussates here and becomes the lateral corticospinal tract. It terminates in the ventral horn.
403
Describe the anterior corticospinal tract.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the medullary pyramids. Remaining 10% that do not decussate here forms the anterior corticospinal tract. It terminates in the ventral horn.
404
Describe the corticobulbar tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the brainstem. The fibres terminate on motor nuclei of cranial nerves. They synapse with LMN's which carry motor signals to the face and neck.
405
Where do the extrapyramidal tracts originate?
The brainstem
406
Vestibulospinal tracts: where do they originate, end and what are they responsible for?
Originate: vestibular nucleus.
End: motor neurones
Function: Responsible for muscle tone and postural control. - Remains ipsilateral.
407
Reticulospinal tracts: where do they originate, end and what are they responsible for?
Originate: reticular formation in midbrain
End: motor neurones
Function: responsible for spinal reflexes
408
Tectospinal tracts: where do they originate, end and what are they responsible for?
Originate: tectum in mid-brain
End: motor neurones
Function: responsible for head turning in response to visual and auditory stimuli.
409
What tracts are known as the ventrolateral/anterolateral system?
Spinothalamic tracts.
410
What tracts are known as the dorsomedial system?
DCML.
411
What would be the signs of a complete spinal cord lesion?
- Weakness in all muscle groups below the lesion.
- Complete sensory loss below lesion.
- Spasticity and hyperreflexia.
412
What is Brown-Sequard syndrome?
Hemi-section of the spinal cord.
413
What would be the signs of Brown-Sequard syndrome?
- Ipsilateral weakness and loss of motor function below the lesion.
- Ipsilateral loss of proprioception, 2-point discrimination and fine touch.
- Contralateral loss of pain and temperature sensation 2-3 spinal segments below the lesion.
414
Where do the rubrospinal tracts originate, end and what are they responsible for?
Originate: Red nucleus in midbrain
End: Motor neurones
Function: rudimentary motor function.
415
Where does the anterior corticospinal tract decussate?
At level of exit/they don't
416
Where does the lateral corticospinal tract decussate?
In the medulla oblogata
417
What is the basal ganglia comprised of?
- The striatum: putamen and caudate nucleus.
- Globus pallidus: internal and external segments.
- Subthalamic nucleus.
- Substantia nigra.
418
How does the basal ganglia connect to inputs of the brain?
By recurrent loops
419
What is the function of the basal ganglia?
It is connected and configured to serve as a specialised action selection mechanism. It determines WHAT you do via a system of inhibition and disinhibition.
420
Why is the term basal ganglia technically a misnomer?
Because ganglia are collection of cell bodies outside of the central nervous system. Since a collection of subcortical cell bodies inside the nervous system are known as nuclei, the name basal nuclei is more accurate
421
Name 4 disorders associated with basal ganglia dysfunction.
1. Huntington's disease.
2. Parkinson's disease.
3. ADHD.
4. OCD.
422
Why does the substance nigra appear black?
Due to neuramelanin that is produced as a by-product of dopamine production
423
Briefly describe how dopamine is produced.
Tyrosine -> L-dopa -> dopamine.
424
What is the function of the limbic system?
Has a role in learning & the regulation and translation of our emotional state into appropriate behaviour
Considered to be the epicentre of emotional and behavioural expression
Important in the 4 F’s: fight, flight, feeding, fornicating (breeding)
425
Which systems does the limbic system influence?
The endocrine system and the autonomic nervous system, and is highly interconnected with the brains pleasure centres (the nucleus accumbens - has a role in sexual arousal and the high experienced with recreational drugs)
426
What structures are contained within the limbic system?
Hippocampus, amygdala, fornix, mammillary bodies, cingulate gyrus, anterior nuclei of thalamus, hypothalamus.
427
What is the papez circuit?
A circuit that connects the main structures of the limbic system. It is involved in memory and emotions.
THALAMUS (ANTERIOR THALAMIC NUCLEUS) - ANTERIOR LIMB OF INTERNAL CAPSULE - CINGULATE GYRUS - CINGULIM - PARAHIPPOCAMPAL GYRUS - FORNIX - MAMILLARY BODIES - MAMILLOTHALMIC TRACT - THALAMUS (ANTERIOR THALAMIC NUCLEUS)
428
Where is the limbic system?
A complex set of structures that lies on both sides of the thalamus, just under the cerebrum.
429
Where is the hippocampus located?
Located within the brain's medial temporal lobe
430
What are the main functions of the hippocampus?
Converts things that are “in your mind” at the moment (in short-term memory) into things that you will remember for the long run (long-term memory)
Critical for episodic memory
431
Where in the brain is the hypothalamus?
Below the thalamus and is part of the limbic system
432
What is the function of the hypothalamus?
To link the nervous system to the endocrine system via the pituitary gland
The hypothalamus controls body temperature, hunger, important aspects of parenting and attachment behaviours, thirst, fatigue, sleep, and circadian rhythms.
433
Where in the brain is the thalamus?
Midline, paired symmetrical structure in the brain - located just above the brain stem between the cerebral cortex and the midbrain.
434
What is the main function of the thalamus?
To RELAY MOTOR AND SENSORY SIGNALS to the cerebral cortex.
435
Where are the lateral geniculate nucleus and medial geniculate nucleus located?
In the thalamus.
436
Where does the substantial nigra project to?
The striatum
437
Where is the red nucleus?
In the midbrain and is involved in motor coordination
438
Nucleus accumbens: where is it? what does it do?
- Part of the striatum in the basal ganglia
- Plays a central role in the reward circuit. Its operation is based chiefly on two essential neurotransmitters: dopamine, which promotes desire, and serotonin, whose effects include satiety and inhibition.
439
How many layers are nerve fascicles/tracts covered by and what are they?
EPINEURIUM: the outermost layer around the entire nerve
PERINEURIUM: covers each fascicle, composed of several layers of pavement epithelium bound by tight junctions
ENDONEURIUM: a layer of delicate connective tissue (reticular collagen) around the myeline sheath of each myelinated nerve fibre - surrounding individual Schwann cells
440
Where is working memory stored?
In the pre-frontal cortex
441
What is the septum pellucidum?
A thin transparent membrane located in the brain between the body and anterior horns of the lateral ventricles.
442
What is the fornix?
C-shaped bundle of nerve fibres in the brain that acts as the major output (efferents) tract of the hippocampus.
The fornix also carries some afferent fibres to the hippocampus from structures in the diencephalon and basal forebrain
443
What shape is the hippocampus often described to look like?
A seahorse
444
What is the direct pathway of the basal ganglia?
When we want to make movement. The motor cortex excites the striatum which inhibits the globus pallidus internal meaning the thalamus is no longer inhibited and can send excitatory signals to the motor cortex = MOVEMENT
445
What is the indirect pathway of the basal ganglia?
When we want to inhibit movement. The motor cortex excites the striatum which inhibits the globus pallidus external meaning the subthalamic nucleus is no longer inhibited. The globus pallidus internal is therefore excited and the thalamus inhibited = reduced movement!
446
What is the lentiform nucleus?
A collective name given to the putamen and globus pallidus, both of which are nuclei in the basal ganglia.
447
What is the reason behind the signs of Parkinson's?
Not enough dopamine.
448
What is the reason behind the signs of Huntington's?
Too much dopamine.
449
What are the signs of Parkinson's disease?
1. Tremor.
2. Bradykinesia.
3. Rigidity.
450
What are some of the symptoms of Huntington's disease?
1. Chorea (jerky, involuntary movements).
2. Dementia.
3. Personality change.
451
In huntington's disease what area of the basal ganglia and what neurotransmitter are affected?
- Striatum (caudate nucleus).
| - GABA.
452
What neurotransmitter is in deficit in huntington's disease?
GABA.
453
In Parkinson's disease what area of the basal ganglia and what neurotransmitter are affected?
Substantia nigra
| Dopamine
454
Compare parkinson's and huntington's in terms of muscle tone, movements and dopamine levels.
```
Parkinson's = Increased muscle tone, reduced movements, too little dopamine
Huntington's = decreased muscle tone, overshooting movements, too much dopamine.
```
455
What is hydrocephalus?
Abnormal accumulation of CSF in the ventricular system, which leads to a build up of pressure which can damage brain tissue.
456
What is the most common cause of hydrocephalus?
Blocked cerebral aqueduct.
457
Give 4 features of pain.
1. Pain is always subjective.
2. It is a sensation.
3. It is always unpleasant.
4. It is an emotional experience.
458
If UMN were damaged, what would the pattern of weakness look like?
Broad
Minimal atrophy
Increased muscle tone→ Spasticity
Clasp-knife response: Initial higher resistance to movement is followed by a lesser resistance
Increase in deep tendon reflexes (e.g. biceps) and decrease in superficial reflexes (e.g. abdominal)
Flexors weaker than extensors in the legs
Extensors weaker than flexors in the arms
459
If LMN were damaged, what would the pattern of weakness look like?
Decreased muscle tone
Muscle paralysis
Weakness and wasting (atrophy)
Arreflexia (absence of the relevant reflex)
Fasciculation’s (twitching)-result from random and spontaneous depolarization of a motor neurone or axon
460
What is the clinical presentation of Brown-Sequard syndrome?
* Ipsilateral upper motor neuron paralysis
* Ipsilateral loss of proprioception
* Contralateral loss of pain and temp sensation
461
Define sound.
The displacement of air particles following a sinusoidal pattern of compression and refraction.
462
Define hearing range.
20 to 20,000 Hz
463
Which parts of the ear make up the outer ear?
The pinna/auricle, the external auditory canal and the tympanic membrane
464
Describe the passage of sound through the outer ear.
The pinna/auricle helps to direct sound waves towards the external auditory canal. The first sound wave enters thee ear via the auditory canal and vibrates the tympanic membrane.
465
What nerve provides general sensation to the outer ear?
CN10
466
What 3 bones make up the ossicular chain in the middle ear?
Malleus, incus and stapes
467
What are the two main muscles in the middle ear?
Stapedius and tensor tympani.
468
What do the muscles in the inner ear protect us from?
Stapedius and tensor tympani act reflexively to continuous loud noise – protect delicate receptor apparatus in inner ear. But cannot protect against sudden intermittent noise.
469
What type of joints are the joints in-between the ossicles?
Synovial joints
470
Which nerve provides general sensation to the inner ear?
Cn 9
471
Which nerve innervates stapedius?
CN VII
472
Which nerve innervates tensor tympani?
Mandibular division of CN5 (V3)
473
Which ossicle does tensor tympani attached to?
The malleus
474
Which ossicle does stapedius attach to?
The stapes
475
How does the tympanic membrane transmit sound to the inner ear?
Travels through three ossicles and then to the oval window.
476
What is the membrane covered opening between middle and inner ear called?
The oval window.
477
Through which mechanism is the middle ear ventilated/exposed to atmospheric pressure?
The eustachian tube.
478
Is the eustachian tube usually open or closed?
Closed, only opens with muscle movements like yawning, swallowing or sneezing.
479
Why does an increase in altitude cause ear pain?
External auditory meatus pressure changes, middle remains at same pressure because eustachian closed = stretches tympanic membrane = pain
Pain relief when yawning as this opens tube thereby allowing the pressure in the middle ear to equalise with the external atmospheric pressure
480
What is the inner ear called?
The cochlea
481
What structure contains the sensory receptors of the auditory system?
The cochlea duct
482
What are the 3 cavities of the cochlea and where are they in relation to the cochlea duct?
1. Scala vestibuli - above the cochlear duct and begins at the oval window
2. Scala media - houses organ of corti
3. Scala tympani - below the cochlear duct and connects to the middle ear via a second-membrane covered opening, the round window
483
Which of the cavities of the cochlea are filled with perilymph?
Scala vestibuli and the scala tympani
484
What is the scala media filled with?
Endolymph
485
What is the function of the round window?
It vibrates with opposite phase to vibrations entering the inner ear through the oval window. This moves the fluid in the cochlea which means that hair cells of the basilar membrane will be stimulated and that audition will occur.
486
Which cavity of the cochlea is the oval window in?
Scala vestibuli
487
Which cavity of the cochlea is the round window in?
Scala tympani
488
What is the helicotrema?
Where the scala tympani and scala vestibuli meet
489
What is the organ of Corti?
A specialised sensory epithelium that allows for the transduction of sound vibrations into neural signals.
490
What does the organ of corti sit on?
The basilar membrane
491
Basilar membrane: The stiff parts = vibrates best with high frequency sounds
The floppy parts – vibrates best with low frequency sounds
What is this called?
The tonotopic axis
492
Where is the basilar membrane most rigid and widest?
* Narrow at base and wide at apex
| * Stiff at base and floppy at apex
493
What is the stria vascularis?
A structure involved in the active transport of K+ into the scala media.
494
What is the potential of the scala media?
+80mV.
495
What are the 3 structures that make up the organ of corti?
1. Hair cells
2. Supporting cells
3. Auditory nerve fibres
496
What neurotransmitter is released by the hair cells in the organ of corti?
Glutamate
497
Organ of corti: How many rows are there of:
a) Inner hair cells?
b) Outer hair cells?
a) 1 row of IHC's.
| b) 3 rows of OHC's.
498
What is present on the inner and outer hair cells?
Stereocilia
499
What structures connect adjacent stereocilia?
Tip-links
500
Briefly describe the release of neurotransmitter in the organ of corti.
When the stereo-cilia waft forwards mechanically gated K+ channels OPEN, resulting in an influx of K+ from the surrounding endolymph (K+ rich) thereby depolarising the membranes
This change in voltage triggers the opening of voltage-gated Ca2+ channels near the base of the cell, which in turn triggers neurotransmitter release
501
What closes voltage gated Ca2+ channels in the organ of corti?
Bending of the hair cells in the opposite direction. Allows the cell to rapidly repolarise.
502
What is the function of the vestibular system?
Balance and spatial orientation.
503
What makes up the vestibular apparatus?
- 3 membranous semi-circular canals
| - 2 saclike swellings: utricle and saccule
504
What type of organs are the utricle and saccule known as?
OTOLITHIC organs
505
What do the semicircular canals detect?
Angular acceleration during rotation of the head.
506
What do the otolithic organs (utricle and saccule) detect?
Linear acceleration and changes in head position in relation to gravity.
507
Where are stereo-cilia located in the vetibular apparatus?
In the utricle in the saccule and in 3 capula at the ampullae at the base of the semi-circular canals.
508
What are the relative positions of the hair cells in the utricle and saccule?
The hair cells of the saccule project at right angles to those of the utricle
509
In what plane do hair cells in the utricle respond to linear accelerations and head-tilts?
In the horizontal plane
510
In what plane do hair cells in the saccule respond to linear accelerations and head-tilts?
When you move from lying to a standing position or to accelerations in the vertical plane like those produced when jumping on a trampoline
511
What are the two types of hearing loss?
1. Conductive hearing loss
| 2. Sensorineural hearing loss
512
When does conductive hearing loss occur?
When there is a problem transferring sound waves anywhere along the pathway through the outer ear, tympanic membrane, or middle ear (ossicles)
513
When does sensorineural hearing loss occur?
The root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII)
514
Describe the I'm Auditory pathway.
Inferior colliculi -> inferior brachium -> medial geniculate body.
515
How many coats does the eye have? What are they?
Three. Outer coat, middle coat (uvea), inner coat.
516
What is the difference between perilymph and endolymph?
Perilymph has composition similar to cerebro-spinal fluid (CSF) and ECF: rich in sodium and poor in potassium and calcium
Endolymph: main componant is potassium and has a potential of ~80-90 mV more positive than perilymph due to a higher concentration of K compared to Na.
517
What does the outer coat of the eye consist of?
The cornea and sclera
518
What does the middle (uvea) coat of the eye consist of?
The iris, ciliary body and choroid
519
What does the inner coat of the the eye consist of?
The retina
520
Which cranial nerve innervates the retina?
Cn 2
521
What are the functions of cones in the retina?
Cones are important for visual acuity and colour vision.
522
What are the functions of rods in the retina?
Important to vision in dim lighting - very sensitive to light, also important for peripheral vision
523
What are rods and cones?
Photoreceptors
524
What are photoreceptors?
Cells in the retina that respond to light.
525
How many layers are in the tear film?
Three
1. Anterior lipid (oils) - hydrophobic barrier to prevent the aqueous layer evaporating
2. Middle aqueous (water, electrolytes & proteins) - secreted by lacrimal glands.
3. Posterior mucous - secreted by goblet cells, provides a hydrophilic layer.
526
Which artery passes into the optic nerve?
Central retinal artery
527
Describe the passage of the fibres from the nasal portion (closest to the nose) of the retina.
They carry the temporal visual fields and cross at the optic chiasm which is located JUST ANTERIOR to the PITUITARY INFUNDIBULUM.
528
Describe the passage of the fibres from the temporal portion (furthest from nose) of the retina.
They carry the nasal visual fields and remain ipsilateral.
529
Where do the optic tracts carry the fibres?
Around the cerebral peduncles to terminate at the lateral geniculate bodies of the thalamus
530
After the lateral geniculate body, what do the optic radiations split into?
1. Meyer's loop
| 2. Baum's loop
531
Describe Meyer's loop.
The fibres carrying information from the inferior portions of the retina (and thus the SUPERIOR VISUAL FIELDS) travel by looping laterally through the TEMPORAL LOBE to the visual cortex.
532
Describe Baum's loop.
The fibres carrying information from the superior portions of the retina (and thus the INFERIOR VISUAL FIELDS) travel by looping superiorly through the PARIETAL LOBE to the visual cortex
533
What type of visual defect will damage to the left optic nerve result in?
Essentially, no vision through the left eye
534
What type of visual defect will damage to the optic chiasma result in?
Loss of vision of the temporal visual fields - this is called HEMIANOPIA
535
What type of visual defect will damage to the left optic tract result in?
Loss of vision of the temporal field of the left eye & the loss of the nasal field of the right eye - another type of hemianopia
536
What type of visual defect will damage to the left Meyer's loop result in?
Carries information from the inferior retina and thus the SUPERIOR VISUAL FIELD so causes loss of vision in the superior nasal field of the left eye and the superior temporal field of the right eye
537
What type of visual defect will damage to the left Baum's loop result in?
information from the superior retina and thus the INFERIOR VISUAL FIELD resulting in loss of vision in the inferior temporal field of the right eye and the inferior nasal field of the left eye.
538
On their way to the visual cortex, where do the cell axons pass through?
Superior colliculus & Lateral geniculate body
539
Where do the fibres reaching the lateral geniculate body come from?
Cone-rich areas of the eye, representing high visual acuity
540
Where do fibres reaching the superior colliculus come from?
Rod-rich areas in the peripheral zones of the eye, where visual acuity is less but detection of movement is greater.
541
Where are the inferior and superior colliculi located?
In the tectum (roof) of the midbrain
542
Eye movement: what is internal rotation known as, which muscles will do this?
INTORTION (towards mid-line)
| Superior rectus and superior oblique will intort
543
Eye movement: what is external rotation known as, which muscles will do this?
EXTORTION (away from mid-line)
| Inferior rectus and inferior oblique will extort
544
Which eye muscles are innervated by the oculomotor nerve CN3?
Superior rectus, medial rectus, inferior rectus and inferior oblique
545
What movement is superior rectus responsible for?
Look laterally and upwards
546
What movement is inferior rectus responsible for?
Look laterally and downwards
547
What movement is lateral rectus responsible for?
Look laterally
548
What movement is medial rectus responsible for?
Look medially
549
What movement is inferior oblique responsible for?
Look medially and upwards
550
What movement is superior oblique responsible for?
Look medially and downwards
551
A 30-year-old man presents with increased muscle tone, brisk reflexes and fasciculations. Which spinal tract is likely to be affected?
Corticospinal (UMN and LMN weakness).
552
A man is feeling very distressed as he woke up being unable to feel the right side of his face and his right arm and leg. What lobe is affected?
The parietal lobe (somatosensory cortex). Feel is the key word here.
553
A woman presents to the stroke unit being unable to move/feel her left leg/foot. Which artery has been affected?
Right anterior cerebral artery (supplies most midline portions of the frontal lobes = primary motor cortex and superior medial parietal lobes = somatosensory cortex)
554
A man presents to the stroke unit being unable to move/feel his right arm, right sided facial drooping and slurred speech. Which artery has been affected?
Left middle cerebral artery (supplies temporal lobe = speech production - wernicke's area)
555
A woman presents to the stroke unit with complete right sided visual field loss. Which artery has been affected?
Left posterior cerebral artery (supplies occipital lobe = vision)
556
A 40-year-old removal man felt immediate back pain and a popping sensation after lifting a heavy box. The next day he noticed he was tripping over his right foot as it was dragging along the floor. What is affected?
Lower motor neurones (he has a slipped disc. The LMN nerve roots coming out of the spinal cord have been damaged).
557
An elderly patient presents with a stiff flexed arm, and a stiff extended leg (both on the left) which the patient finds difficult to bend. What is affected?
Upper motor neurone – this patient has had a stroke and so the UMN’s are affected.
558
You are carrying out an eye examination on a patient who is looking at the tip of your nose. Behind you, on your left hand side, is a tall medical student. What would be the patients’ retinal representation of the image of this students’ face?
The retinal image is converted from right to left and reversed. The students face is now in left lower corner.
(Medical student is stood on your left but that is the patients right).
