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Neurology Flashcards

1
Q

What components makeup neuron

A

Dendrites
Cell body
Axon
Axon terminal/synaptic terminal

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2
Q

What does the axon hillock contain

A

High concentration of voltage gated Na+ channels

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3
Q

Function of dendrites

A

Involved in graded potentials

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4
Q

What are graded potentials?

A

Little changes in the voltage of the cell membrane to try to make the cell have the ability to generate action potentials

This is comprised of the EPSP (depolarisation) and IPSP hyperpolarisation

Takes place within ligand-gated channel of dendrites

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5
Q

Function of cell body

A 
graded potentials
protein synthesis (NT, enzymes, membrane proteins)
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6
Q

What is the name of RER in the neuron

A

Nissl bodies

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7
Q

Function of Axon

A

Conduct Action Potential
Action potential consists of a depolarisation wave followed by a repolarisation wave

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8
Q

Axonal transport

A

Retrograde: Axon terminal to the cell body
Anterograde: Cell body to axon terminal

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9
Q

Function of axon terminal

A 
Secretory region (neurotransmitter released)
Reuptake of neurotransmitter
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10
Q

How to remove neurotransmitters from a synapse (NT termination)

A

Reuptake
Degradation

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11
Q

Structural classification of neuron

A

1 multipolar (3+ dendritic extension).

  1. bipolar (1 dendritic extension). Found in the retina, olfactory epithelium, and inner ear.
  2. pseudo unipolar. Found in dorsal root ganglion + CN5
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12
Q

Functional classification of neurons

A

Sensory (afferent)

Motor (efferent)

interneurons (within CNS)

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13
Q

What is the resting membrane potential

A

The voltage difference across cells when the cell is at rest

It exists in all cells

RMP: -70mV → -90mV

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14
Q

Describe how resting potential is established

A
  1. 3Na+/2K+ ATPase channels: This causes the cell to be slightly negatively. Generate concentration gradient for ions to move
  2. Leaky K+ channels (more permeable than Na+): K+ leaves cells due to concentration gradient. Since it’s bound to an anion, it leaves it behind, increasing the negative charge in the cell.
  3. Leaky Na+ Channel: Na+ moves into the cell due to conc gradient.
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15
Q

Nernst potential

A

Same for Na+

E(K+) =61.5 x log10 (K(out)/K(in))

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16
Q

Where does graded potential occur

A

Postsynaptic neurons

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17
Q

Difference between graded potential and action potential

A

The graded potential is when potential is reached either at threshold potential or slightly above the threshold potential

why?

The ESPS produced may not be enough to reach threshold frequency as they lost their strength.

Graded potential also needs a stimulus

Summation can help to reach threshold potential

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18
Q

What is temporal summation

What is the spatial summation

A

One presynaptic neuron repeatedly stimulates a postsynaptic neuron.

Multiple presynaptic neurones firing simultaneously on one postsynaptic neuron

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19
Q

How do you get to action potential

A

RMP → T.P → Action potential

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20
Q

Describe action potential

A

Depolarisation

  1. Once the action potential reaches -55mV, the Na+ channel opens and allows Na+ to enter the axon. Na+ channels close once action potential reaches +30mV. The action potential travels down to the terminal bulb
  2. Calcium channels open when the action potential reaches +30mV. Causes the synaptic vesicles to fuse with the cell membrane. Releases contents

Repolarisation

  1. At +30mV opens up voltage-gated K+ channel. Allow for potassium to exit the cell.
  2. +30mV → -90mV
  3. The repolarisation of the K+ channels closes the Ca+ channel
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21
Q

Where can you find glial cells

A

PNS & CNS

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22
Q

What makes up nervous tissue

A

Glial cells and neurons

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23
Q

Where do you find astrocytes

A

CNS

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24
Q

What is the blood-brain barrier

A

3 layer innermost→ outermost

  1. Endothelial cells, lots of tight junctions (control permeability)
  2. Basal lamina
  3. foot processes of astrocytes

Also contains pericytes

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25
What is it called when parts of the brain lack blood-brain barrier
Circumventricular organs e.g posterior pituitary, need to be in contact with blood for the sensory role
26
What do glial cells do?
Blood-brain barrier- makes tight junctions Potassium buffer Removes excess neurotransmitter Glycogen reserve
27
Oligodendrocytes function
1. Myelinate axons in CNS + CN2 2. Myelinate 30-60 axons 3. When there is damage there is no ability to regenerate 4. Demyelination = multiple sclerosis
28
Schwann cells function
1. Myelinates axons in PNS + CN 3-12 2. Myelinate segments of one axon 3. If damaged can regenerate
29
What are spaces between Schwann cells called?
Nodes of Ranvier- concentrated with voltage-gated ion channel
30
Why does myelination increase action potential speed (permeability)
Nodes of Ranvier contain voltage-gated sodium channels allowing sodium to enter. There are no Na+ channels present where there is myelination. This means that there are periods where no depolarisation occurs until the action potential reaches another node of Ranvier to become stimulated. The same occurs with K+ leaving the axons.
31
How does myelination speed up action potential speed?
Decrease permeability at the myelin sheaths Myelination also decreases membrane capacitance
32
What increases conduction velocity
Diameter Myelination
33
What is the blood CSF barrier made up of?
1: Fenestrated Endothelial cells 2: Basal lamina 3: Ependymal cells (tight junctions)
34
Ependymal cells function
Controls the movement of substances across the blood CSF barrier
35
Microglia cells
Acts as an immune system cell Specialised macrophage cell Phagocytosis Can secrete toxins that could potentially affect neural tissue
36
Boundaries of frontal lobe
Central sulcus Lateral sulcus
37
What does the front lobe contain
Motor Cortex Broca's Area
38
Another name for primary motor cortex
Broadman area 4
39
Broca's area
Stimulating muscles of speech Right-handed → left Broca Communicates with Wernicke's area
40
Boundaries of parietal lobe
Central sulcus (ant) Lateral sulcus (inf) Parieto-occipital sulcus (post)
41
What does the parietal lobe contain
Primary somatosensory cortex Consciousness, awareness of somatic sensations Somatosensory association cortex Analysing sensations, recognition of sensations, memory storage
42
Temporal lobe boundaries
Lateral sulcus Pre occipital notch
43
The cortexes of temporal lobe
auditory cortex Wernicke's area
44
Boundaries of the occipital lobe
Parieto-occipital sulcus Pre-occipital notch
45
Occipital cortex
Primary Visual cortex Conscious awareness of visual stimuli Visual association cortex Visual stimuli → meaning + understanding
46
Components of basal ganglia
Caudate nucleus Putamen Globus pallidus (internal + external) Thalamus (VA nucleus + VL nuceus) Subthalamic nuclei Substantia nigra
47
Striatum composition
Caudate nucleus + putamen
48
Lentiform nucleus
Putamen Globus pallidus
49
Basal Ganglia function
Involved with movements: Stop Start Modulation
50
What is the purpose of direct pathway of basal ganglia
increase motor activity Neurons from the cortex move down to the striatum (Glutamate) → Globus pallidus internus (GABA) → Thalamus (GABA) → Cortex
51
Glutamate is what kind of neurotransmitter
stimulatory neurotransmitter
52
What kind of neurotransmitter is GABA
inhibitory transmitter
53
Indirect pathway of basal ganglia
Decrease unwanted motor activity Cortex → (Glutamate) Striatum → (GABA) Globulus pallidus externus → (GABA) Subthalamic nucleus → (Glutamate) Globus pallidus internus → (GABA) Thalamus VA + VL → Cortex
54
Nigrostriatal pathway
Modulation (amplify) of activity Direct pathway: neurons attach from the zona compacta of substantia nigra to the striatum nucleus via the D1 receptor (stimulatory receptor) and release dopamine. Indirect pathway: neurons from zona compacta of substantia nigra attach to the striatum via D2 receptors (inhibitory receptors)
55
What is diencephalon
A grey matter substance deep within the cerebrum
56
What makes up the diencephalon
Hypothalamus Epithalamus (Pineal gland, habenula, post commissure) Sub-thalamus
57
Hypothalamus function
Limbic system Endocrine system Autonomic NS
58
What is the limbic system involved?
Emotions and behaviours olfaction Memory and learning
59
What is the function of the mammillary bodies
Reflex with olfaction Formation of new memories
60
What kind of memory is the hypothalamus involved in
Long term memory Explicit: Conscious memory Episodic Semantic Implicit: Unconscious memory Skills and habits Conditioned reflex Emotion
61
What is the thalamus
Paired midline structure in the brain Contains multiple nuclei: Relay + Association function
62
What sensations pass through the thalamus?
All sensation except olfactory pass through it
63
Anatomy of the limbic system
Limbic lobe (Cingulate gyrus, parahippocampal gyrus) Hippocampus (Memory) Amygdala (Emotions and behaviours) Hypothalamus Thalamus Septal area Habenula
64
What is the hippocampus involved in
Memory
65
What is the amygdala responsible for
Emotions and behaviour
66
What is the fornix
Connection from hippocampus to septal area and hypothalamus
67
What is the papez circuit responsible for and how does it work?
Part of the limbic system involved in-memory processing and learning 1. Hippocampus 2. Fornix 3. Mammillary bodies 4. Mammilothalmic 5. The anterior nucleus of the thalamus 6. Internal capsule 7. Cingulate gyrus 8. Parahippocampal gyrus 9. Dentate gyrus 10. Subiculum
68
What is the midbrain consist of?
Tectum (inferior + superior colliculi) Cerebral peduncle (tegmentum + crus cerebri) Surrounds cerebral aqueduct
69
What is the medulla oblongata continuous with?
Spinal cord
70
What is pons
Bridge to cerebellum
71
Functions of cerebellum
Balance Equilibrium Motor learning coordination muscle tone
72
The internal circuitry of the cerebellum
Sensory pathway → mossy fibres → granule cells → Purkinje fibres Inferior Olives→ climbing fibres
73
Meninges
Pia mater (innermost) Subarachnoid space Arachnoid mater Subdural space Dura matter (inner: meningeal & outer: periosteal) Epidural space Skullbone Scalp
74
Dural septa
Falx cerebri Tentorium cerebelli Falx cerebelli Diaphragm sellae Important to surround and protect dural sinuses
75
Epidural hematoma
Location: Epidural space (Temporal bone fracture) Cause: Temporal bone fracture affecting middle meningeal artery Symptoms: Headache, nausea/vomiting, CN3 palsy Management: Evacuate hematoma, Maintain intracranial pressure
76
Subdural Hematoma
Location: Subdural space Cause: Motor vehicle accident, Trauma, falls Symptoms: vary, headaches, high BP, Low pulse, Confusion Management: Evacuate hematoma
77
Subarachnoid hematoma
Location: Subarachnoid space Cause: Berry (saccular) aneurysm, Ruptures Symptoms: Thunderclap headache, nausea, vomiting, neck stiffness, photophobia, delirium Management: Supportive care Decrease BP
78
Intracerebral hematoma
Location: Thalamus, Basal ganglia, Cerebellum, Pons Cause: Hypertension, amyloid deposits Symptoms: Nausea, vomiting, headache, hemiplegia
79
What are the component of CNS
Brain Spinal cord
80
What are the component of PNS
Sensory component Motor component =spinal nerves
81
Spinal cord where does it terminate
L1/L2
82
Segments of spinal cord + spinal nerves
Cervical (8 pairs of spinal nerves) Thoracic (12 pairs of spinal nerves) Lumbar (5 pairs of spinal nerves) Sacral (5 pairs of spinal nerves) Coccygeal (1 pair of spinal nerves) To remember: You have breakfast at 7, lunch at 12, dinner at 5 and a big drink and a small dessert.
83
White matter: cervical → coccygeal
Decrease in white matter
84
Grey matter: cervical → coccygeal
Increase in grey matter
85
What part of the spinal cord contains sensory neurons
Posterior/Dorsal grey horn
86
What part of the spinal cord contains motor neurons
Anterior/Ventral grey horn
87
What are group of cell bodies (axons) in CNS + PNS called
CNS: nucleus PNS: ganglia
88
What is the grey matter?
Grey matter containing unmyelinated dendrites
89
Divisions of grey matter
Posterior grey horn -Most posterior is somatic sensations, and anterior to that is visceral sensations. Lateral grey zone- Visceral motor Anterior grey horn - Somatic motor A Gray commissure connects two sides of the horn
90
Rexed laminae
10 in grey matter Laminae I-III: Substania gelatinosa Laminae VII: Clarkes Column (C8-L3) Laminae IX: motor supply
91
What is white matter
Structure of spinal cord containing myelinated axons
92
Parts of white matter
Dorsal white column Lateral white column Anterior white column Anterior white commisure
93
The tracts of the white column
Ascending tract (Sensory) Descending (motor)
94
Dorsal Column Medial Leminiscal pathway carries what sensations?
Discriminative touch Pressure & Stretch & Vibrations Proprioception
95
What tract is the DCML
Sensory Ascending tract
96
Receptors in DCML
Meissner's Corpuscles Merkel's discs Pacinian corpuscles Peritrichial nerve endings Ruffini corpuscles
97
DCML Pathway
Stimulus → Receptors → afferent neurons →Dorsal root ganglia → Either: Fasciculus gracilis (Below T6)→ Nucleus gracilis (2nd order neurons- medulla) Fasciculus cuneatus (Above T6) → Nucleus cuneatus (2nd order neurons) Medial leminiscus→ VPL nucleus of the thalamus → Posterior ⅓ Internal capsule → corona Radiata → Somatosensory cortex
98
DCML contralateral/ipsilateral
Ipsilateral at the level of spinal cord Contralateral once you get to internal arcuate fibres
99
Spinothalamic Tract Division
Ant: crude touch, pressure Lat: pain, temp
100
Receptors of Spinothalamic Tract
Nociceptors: tissue damage and extreme temp Fast pain (A-delta fibres), stimulated my mechanical stimuli, and cold temp Slow pain (C fibres), stimulated by mechanical stimuli, hot temp, chemical factors Merkel's disc stimulated by crude touch and pressure
101
Where do neurons from the spinothalamic tract enter the spinal cord
Rexed laminae crosses to contralateralside of the spinal cord to anterior white commissure
102
Spinothalamic lesions
Has ascending and descending tracts (Tract of Lisshauer) A lesion will result in 2 segments down and on the contralateral side being injured
103
Crude touch and pressure spinothalamic tract
Stimulus → Receptor → Dorsal root ganglia (1st order neuron) → Rex lemniscus (dorsal grey horn + 2nd order neuron) cross over anterior commissure ventral white column→ ventral posterior inferior thalamic nucleus → Internal capsule → corona Radiata → cortex
104
Pain and temp pathway spinothalamic tract
Stimulus → Receptor → Dorsal root ganglia → Rex lemniscus .. → Lateral Spinothalamic Tract → Ventral posterior lateral nucleus in the thalamus → internal capsule → corona Radiata → cortex
105
Pain modulation systems
Gate control theory (Melzack-wall pain gate) Descending analgesic system
106
What is the regulatory for slow pain
C fibres unmyelinated, short axon. Secrete Substance P
107
What is the regulatory for fast pain
A Delta fibre - myelinated long axon Glutamate
108
Gate control theory
Touch receptors are stimulated and travel via DCML giving off collateral stimulating inhibitory receptors to prevent inhibit pain and temp action potential
109
Spino cerebellar Tract subdivided
Dorsal Spinocerebellar Tract Ventral Spinocerebellar Tract Cuneo cerebellar Tract Spino-olivary tract (Dirty Virgins Cant Spit)
110
Spinocerebellar tract stimulus
Proprioception: Muscle spindles: Type 1a (faster) type 1b Golgi tendon organ Touch + Pressure
111
Dorsal Spinocerebellar Tract
Ipsilateral. Below L2 Stimulus → Receptor → Dorsal root ganglia → Clarke's nucleus (dorsal grey horn) → Lateral white column → Inferior cerebellar peduncle
112
Ventral Spinocerebellar Tract
Contralateral. Upper limbs (head + neck) Stimulus → Receptor → Dorsal Root ganglion → Dorsal grey horn → Cross over via anterior white commissure → Superior cerebellar peduncle → Crosses over AGAIN!!!!!
113
Cuneocerebellar tract
Ipsilateral Stimulus → Receptor → Dorsal Root Ganglia → Posterior grey horn → accessory cuneate nucleus → External arcuate fibres → Cerebellum
114
Inferior Olivary nuclei
Contralateral Stimulus → Receptor → Dorsal root ganglion → Posterior grey horn → Crosses over via anterior white commissure → Inferior Olivary nucleus → Inferior cerebellar peduncle via climbing fibres → cerebellum
115
Corticobulbar Tract
Bilateral Origin: motor cortex Destination: CN5, CN7, CN12 Nucleus ambiguous (CN9, 10, 11) Function: CN5-Muscles of mastication CN7- Muscles of Facial expression Nucleus ambiguous- Soft palate, Uvula, Pharynx, Larynx CN12-muscles of tongue
116
Corticospinal tract
control of voluntary muscles Lateral (75%): pyramidal (medulla) decussation - limb muscles Medial (25%): decussates as it leaves via the anterior white commissure (
117
Reticulospinal tract
Descending Spinal reflexes Medial pathway: Pons controls extensors to increase muscle tone thereby facilitatory voluntary movement Lateral pathway: The medulla controls flexors acting to decrease muscle tone thereby inhibiting voluntary movement
118
What is the extrapyramidal tract responsible for?
Involuntary autonomic movement Descending pathway
119
What vertebrae should a lumbar puncture be performed
L3/L4
120
What is the filum terminale
Extension of pia mater attaches onto the coccyx prevents the spinal cord from moving
121
Denticulate nucleus
When pia mater extends onto the outer dura forms these ligaments
122
Extrafusal fibres functions
Connect with tendons Generate movement
123
Intrafusal fibres function
Proprioceptors Length and velocity Consist of: Nuclear bag fibres Nuclear chain fibres
124
Nuclear bag fibres
More sensitive than nuclear chain fibers to : Length and velocity
125
Nuclear chain fibers
More specific to length
126
Nuclear bag fibres vs nuclear chain fibres
Type 1a fibres + gamma motor neurons in nuclear bag fibres type 1a + 2 fibres + gamma motor neurons in nuclear chain fibres
127
Type 1a muscle fibres sensory or motor
Sensory
128
Type 2 muscle fibres sensory or motor
Sensory
129
Gamma motor neurons sensory or motor
Motor
130
What reflex is the stretch reflex
Monosynaptic
131
Stretch receptor reflex
Ipsilateral Stimulus → type 1a + 2 fibres (sensory) → ventral grey horn → Synapses with motor neuron It also synapses with interneurons to inhibit opposite muscles (reciprocal inhibition) Both receptors act on the extra-fusal muscles
132
What do the gamma motor neurons stimulate
Muscle spindle fibres contract where the stimulus is detected Inhibits the opposite muscle spindle fibres
133
Upper motor neuron lesion leads to
134
What innervates the Golgi tendon organ
Type 1b muscle fibres
135
What does tendon connect
muscle -\> bone
136
What does the golgi tendon organ detect
Tension due to muscle contraction
137
Golgi tendon organ reflex
Muscle contraction → type 1b fibres → Dorsal root ganglia → posterior grey horn → Reciprocal Activation: Interneuron inhibitory (Glycine)→ gamma motor neuron → inhibits muscle that is experiencing contraction Autogenic Inhibition: Interneuron stimulatory (Glutamate) → Gamma motor neuron → stimulates the opposing muscle that isn't experiencing contraction
138
UMN lesions condition examples
Stroke Multiple sclerosis ALS
139
LMN lesions conditions called?
Polio Spinal muscular atrophy Cauda Equina syndrome ALS
140
Clasp knife reflex
A spasticity test A physical exam to assess the passive flexion movement. If there is spasticity there will be a lot of resistance during flexion until it does a sudden flexion movement
141
UMN lesion characteristics
Mass: ⇣15-20% Strength: Spastic paralysis Tone: ⇡ hypertonia Deep tendon reflexes: ⇡ hyperreflexia
142
LMN lesion characteristics
Mass: ⇣80% Strength: flaccid paralysis Tone: ⇣hypotonia Deep Tendon Reflexes: ⇣hyporeflexia
143
5 facial branches of the facial nerve
Temporal Zygomatic Buccal Marginal Mandibular Cervical
144
Bells palsy
The unilateral facial droop in at least lower ⅔ of face The forehead has both contralateral and ipsilateral innervation The face has only contralateral innervation LMN means paralysis of all the sides of that face, the ipsilateral side as a lesion. UMN lesions mean that lower ⅔ of the contralateral side
145
How can PNS be subdivided
Sensory Motor
146
How can motor PNS be further subdivided?
Autonomic and Somatic Autonomic is further subdivided: into SNS, PSNS, Enteric
147
What chemical does the somatic NS secrete
Ach
148
Difference between the autonomic and somatic NS
Somatic: one motor neuron to reach the effector organ Autonomic: Takes two motor neurons (preganglionic + postganglionic) to reach the effector organ
149
What is the thoracolumbar outflow
T1-L2 Contains the preganglionic fibres of the autonomic sympathetic nervous system
150
PSNS vs SNS diff in ganglion
PSNS: Long preganglionic Short postganglionic SNS: Short preganglionic, Long postganglionic
151
Fibers that release Ach are called
Cholinergic fibres
152
What chemical does SNS secrete?
Norepinephrine therefore adrenergic fibers
153
What fibres are presynaptic ganglion
Cholinergic therefore secrete Ach
154
What fibres are postsynaptic ganglion
Adrenergic → NE There are 5 subtypes of adrenergic
155
SNS on heart
Increase heart rate Increase CO Increase BP
156
Autonomic SNS effect on oesophagus + bronchioles+ lungs
Oesophagus: Decrease peristalsis Bronchioles: dilate bronchioles. Decrease secretions and vasoconstriction of brachial arteries
157
SNS effect on the stomach
Inhibit peristalsis decrease absorption and secretions
158
SNS on liver + gallbladder
Liver : Increase Glycogenolysis Gall bladder: Decrease Biliary Tree flow
159
SNS effect on the pancreas + spleen
Pancreas: Decrease insulin production Increase Glucagon production Spleen: Decrease splenic contraction
160
SNS on stomach
Decrease peristalsis Decrease absorption Decrease secretion
161
SNS effect on kidney
Decrease urine production Decrease blood flow Increase in renin release Decrease peristalsis
162
SNS on large + small intestine
Inhibit peristalsis
163
SNS on urinary bladder
Detrusor muscle: decrease contractions Internal urethral spincter: increase contractions/constriction
164
SNS on gonads
Male: Ejaculation Female: Uterine contraction (nonpregnant)
165
What parts affect SNS control
Limbic nuclei Hypothalamus
166
PNS effect on lungs (bronchi)
Bronchoconstriction Increase secretions
167
PNS on heart
SA/AV node: Decrease heart rate Decrease blood pressure
168
PNS on oesophagus
Increase peristlasis
169
PNS effect on the stomach
Increase in motility Increase secretions
170
Where would you find cholinergic receptors
PNS
171
How many subtypes of cholinergic fibres do you have?
Nicotinic: Ach + nicotine -Ion channels are ligand-gated Muscarinic: Muscarine + Ach -G protein-coupled receptors
172
What role Ach do in the brain
Increase memory Arousal Analgesia
173
Olfactory CN 1
174
Optic nerve 2
175
Oculomotor CNIII
Origin: Midbrain Structure supplying: S.Rectus, Levator palpebrae sp, I rectus, I oblique, medial rectus, pupil, ciliaris Fibres: GSE, GVE Function: Eye movement, eyelid movement, accommodation of pupil size Exit skull: Superior orbital fissure Motor
176
Trochlear nerve
177
What C1 of the cervical plexus run alongside with
CN12
178
Superficial Cervical plexus nerves
179
Brachial plexus
180
Lumbar plexus
181
Left eye visual field
Temporal - left Nasal - right
182
Right eye visual field
Nasal - left Temporal - right
183
Superior retinal fibres?
Go to parietal lobe (Baums loop)
184
Inferior Retinal fibres?
Go to temporal loop | (Myers loop)
185
Monocular Blindness
Lesion to optic nerve
186
Bitemporal Hemianopia
Lesion to the optic chiasm
187
Binasal kemianopia
Affects ipsilateral fibres
188
Visual eye fields
189
Left/Right homonymous hemianopia
190
Left inferior quadrant hemianopia
If the right superior retinal fibres are damaged you are losing vision of the inferior visual field of the left side We know that anything coming from the right side damages the left eye/visual field. But superior retinal fibres only pick up information from the inferior visual field.
191
Right superior quadrant hemianopia
Inferior retinal fibres only pick up information from the superior visual field. Therefore wont be able to see on the Superior right visual field
192
optic radiation
Parietal - inferior retinal fibres (Baum's loop) Temporal- superior retinal fibres (Meyer's loop)
193
Left homonymous hemianopia
Damage to right optic radiation There is visual field loss of the right visual field
194
Cochlear pathway
Sound wave → Oracle → External acoustic meatus → Sound wave hits the tympanic membrane (vibrates-compresses + decompresses) → ossicles (malleus → incus → stapes) → oval window → scala vestibuli → scala media → scala tympani → round window → cochlear branch of CN VIII
195
Ascending auditory pathway
Cochlear branch of CN VIII → Internal acoustic meatus → Cochlei nucleus → Cochlea nuclei → Dorsal cochlear nuclei + Posterior ventral cochlear nuclei: Cross over and ascend to the nucleus of the lateral lemniscus →Anterior Ventral nuclei Contralateral (area know as trapezoid body) + Ipsilateral → Superior Olivary Nuclei Tract joins (lateral lemniscus) → Inferior colliculus → medial geniculate nucleus → Primary auditory cortex →
196
Hearing is
Bilateral Nucleus of the lateral lemniscus cross over + inferior colliculus
197
Give 3 functions of the cranial meninges.
1. Protects the brain and spinal cord form injury. 2. Provides a framework for cerebral and cranial vasculature. 3. Provides a space for the flow of CSF.
198
What are the 3 meningeal layers?
1. Dura mater (outermost). 2. Arachnoid mater. 3. Pia mater (innermost).
199
What are the 2 connective tissue sheets of dura mater?
1. Endosteal layer - lines the cranium. 2. Meningeal layer.
200
Where are the dural venous sinuses located?
Between the endosteal layer of dura and the meningeal layer.
201
What vein do the dural venous sinuses drain into?
The internal jugular veins.
202
Name 3 locations where the dura mater folds inwards as dural reflections?
1. Falx cerebri. 2. Tentorium cerebelli. 3. Falx cerebelli.
203
Where is the falx cerebri located?
It lies in the longitudinal fissure between the cerebral hemispheres.
204
Where is the tentorium cerebelli located?
The tentorium cerebelli is a thick fibrous roof lying over the posterior cranial fossa and the cerebellum.
205
Where is the falx cerebelli located?
Between the 2 lobes of the cerebellum.
206
What lies beneath the arachnoid mater?
The subarachnoid space containing CSF and arteries.
207
What is the function of the blood-brain barrier?
It protects the brain by preventing the passage of some substances from circulation into the nervous tissue.
208
Which meningeal layers are highly vascularised?
The dura and pia mater. The arachnoid mater is avascular.
209
What are the 2 main arteries that supply blood to the brain?
1. Vertebral arteries. 2. Internal carotid arteries.
210
Which arteries supply about 80% of blood to the brain?
The internal carotid arteries.
211
What are the vertebral arteries a branch of?
The subclavian arteries.
212
Where do the vertebral arteries enter the skull?
Through the foramen magnum.
213
What are the internal carotid arteries branches?
The common carotids. Arise from bifurcation at the same level as the upper border of the thyroid cartilage (T4)
214
What do the vertebral arteries supply?
The posterior cerebrum and the contents of the posterior cranial fossa.
215
What do the internal carotid arteries supply?
The anterior and middle parts of the cerebrum and the diencephalon.
216
Where do the internal carotid arteries enter the skull?
Through the carotid foramina.
217
What are the terminal branches of the internal carotid arteries?
The middle and anterior cerebral arteries.
218
What does the middle cerebral artery supply?
The lateral surface of the hemispheres.
219
What does the anterior cerebral artery supply?
The medial aspect of the hemispheres and the corpus callosum.
220
What does the posterior cerebral artery supply?
The occipital lobe.
221
What artery passes through the foramen spinosum?
The middle meningeal artery.
222
What do the two vertebral arteries form?
The basilar artery.
223
Where is a berry aneurysm likely to occur?
At branching points in the circle of willis, especially at the anterior communicating artery.
224
What is a berry aneurysm?
A sac-like out pouching that will progressively enlarge until it ruptures resulting in haemorrhage.
225
What are the two types of stroke?
1. Ischaemic. 2. Haemorrhagic (intracerebral or subarachnoid).
226
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
227
Where do cerebral veins drain into?
Into dural venous sinuses.
228
What does the great cerebral vein drain?
Deep brain structures.
229
What sinus does the great cerebral vein drain into?
The straight sinus.
230
Where is the straight sinus located?
In the midline of the tentorium cerebelli.
231
What vessels lie in the cavernous sinus?
- Cn 3, 4, 5(1), 5(2) and 6. - Internal carotid artery.
232
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.
233
How do dural venous sinuses and veins outside the skull communicate?
Via emissary veins.
234
What is the clinical significance of emissary veins?
They represent a possible route for infection to spread into the cranial cavity.
235
Briefly describe the pathway of venous drainage starting at the great cerebral vein.
Great cerebral vein -\> straight sinus -\> transverse sinus -\> sigmoid sinus -\> internal jugular vein -\> jugular vein -\> brachiocephalic vein -\> SVC.
236
What sinuses form the confluence of sinuses?
The straight sinus and the superior sagittal sinus.
237
Where is the largest aggregation of choroid plexus?
In the lateral ventricles.
238
Where is the majority of CSF produced?
In the lateral ventricles (greatest amount of choroid plexus here`).
239
What is ependyma?
A thin-epithelial like structure lining the ventricles.
240
Tight junctions prevent the passage of fluid into the ventricles. Why is this important?
It means that the volume and composition of CSF can be closely controlled.
241
What embryonic part of the brain is the midbrain formed from?
Mesencephalon.
242
What embryonic part of the brain is the pons formed from?
Metencephalon of Rhombencephalon.
243
What embryonic part of the brain is the medulla oblongata formed from?
Myelencephalon of Rhombencephalon.
244
- What is the name of Cn1? - Where does it exit the skull? - Sensory, motor or both?
- Olfactory. - Cribriform plate of ethmoid bone. - Sensory.
245
- What is the name of Cn2? - Where does it exit the skull? - Sensory, motor or both?
- Optic. - Optic canal. - Sensory.
246
- What is the name of Cn3? - Where does it exit the skull? - Sensory, motor or both?
- Occulomotor. - Superior orbital fissure. - Motor and parasympathetic.
247
- What is the name of Cn4? - Where does it exit the skull? - Sensory, motor or both?
- Trochlear. - Superior orbital fissure. - Motor.
248
- What is the name of Cn5? - Where does it exit the skull? - Sensory, motor or both?
- Trigeminal. - V(1)-superior orbital fissure. V(2)-foramen rotundum. V(3)-foramen ovale. - Both: sensory and motor.
249
- What is the name of Cn6? - Where does it exit the skull? - Sensory, motor or both?
- Abducens. - Superior orbital fissure. - Motor.
250
- What is the name of Cn7? - Where does it exit the skull? - Sensory, motor or both?
- Facial. - Internal acoustic meatus. - Both: sensory and motor and parasympathetic.
251
- What is the name of Cn8? - Where does it exit the skull? - Sensory, motor or both?
- Vestibulocochlear. - Internal acoustic meatus. - Sensory.
252
- What is the name of Cn9? - Where does it exit the skull? - Sensory, motor or both?
- Glossopharyngeal. - Jugular foramen. - Both: sensory and motor and parasympathetic.
253
- What is the name of Cn10? - Where does it exit the skull? - Sensory, motor or both?
- Vagus. - Jugular foramen. - Both: sensory and motor and parasympathetic.
254
- What is the name of Cn11? - Where does it exit the skull? - Sensory, motor or both?
- Accessory. - Jugular foramen. - Motor.
255
- What is the name of Cn12? - Where does it exit the skull? - Sensory, motor or both?
- Hypoglossal. - Hypoglossal canal. - Motor.
256
- What does Cn1 innervate? - What are it's functions?
- Innervates: olfactory epithelium. - Function: olfaction.
257
- What does Cn2 innervate? - What are it's functions?
- Innervates: retina. - Function: vision.
258
- What does Cn3 innervate? - What are it's functions?
- Innervates: medial, superior and inferior rectus muscles and inferior oblique and levator palpebrae superioris. - Motor function: movement of eyeball. - Parasympathetic function: constriction and accommodation.
259
- What does Cn4 innervate? - What are it's functions?
- Innervates: superior oblique. - Functions: movement of eyeball.
260
- What does Cn5 innervate? - What are it's functions?
**- Sensory innervation:** face, scalp, cornea, nasal and oral cavities, anterior 2/3 of the tongue, dura mater. (FONDSAC) **- Motor innervation:** muscles of mastication and tensor tympani.(MOMTT) * *- Sensory function:** general sensation. * *- Motor functions:** open and close the mouth. Tenses tympanic membrane.
261
- What does Cn6 innervate? - What are it's functions?
- Innervates: lateral rectus. - Function: eye movement, abduction.
262
- What does Cn7 innervate?
- Special sensory innervation: anterior 2/3 of tongue - taste. (SAT) - Motor innervation: muscles of facial expression and stapedius. - Parasympathetic innervation: submandibular and sublingual and lacrimal glands.
263
- What does Cn8 innervate? - What are it's functions?
- Innervation: cochlea and vestibular apparatus. - Functions: hearing and proprioception of head and balance.
264
- What does Cn9 innervate?
- Sensory innervation: posterior 1/3 of the tongue, middle ear, pharynx, carotid bodies. (PEPC) - Motor innervation: stylopharyngeus. - Parasympathetic innervation: parotid gland.
265
- What does Cn10 innervate?
- **Sensory innervation**: pharynx, larynx, oesophagus, external ear, aortic bodies, thoracic and abdominal viscera. (O PALATE) **- Motor innervation:** soft palate, larynx, pharynx. (SLP) - **Parasympathetic innervation**: CV, respiratory and GI systems.
266
- What are the functions of Cn10?
- Sensory functions: general sensation. - Motor functions: speech and swallowing. - Parasympathetic functions: control over CV, respiratory and GI systems.
267
- What are the functions of Cn9?
- Sensory functions: general sensation, taste, chemo/baroreceptor. - Motor functions: Swallowing (larynx and pharynx are elevated). - Parasympathetic function: salivation.
268
- What are the functions of Cn7?
- Sensory function: taste. - Motor function: facial movement and tension of ossicles. - Parasympathetic function: salivation and lacrimation.
269
- What does Cn11 innervate? - What are it's functions?
- Innervation: trapezius and sternocleidomastoid. - Functions: movement of head and shoulders.
270
- What does Cn12 innervate? - What are it's functions?
- Innervation: intrinsic and extrinsic muscles of the tongue. - Function: movement of the tongue.
271
What are the characteristic features of a cervical vertebra?
- Small vertebral body. - Transverse foramen for vertebral arteries. - Bifurcation of spinous processes (except C7). - Triangular intervertebral foramen.
272
What region of the vertebral column has the greatest capacity for rotation?
The thoracic region.
273
What region of the vertebral column has the least capacity for flexion?
The thoracic region; this is due to the presence of the ribcage.
274
What are the 2 components of an intervertebral disc?
1. Nucleus pulposus. 2. Annulus fibrosus: concentric layers of collagen surrounding the nucleus pulposus.
275
What does the ligamentum flavum connect?
Connects the laminae of adjacent vertebrae.
276
Where does the spinal cord end? a) in an adult. b) at birth. c) in the embryo.
a) L2. b) L3. c) runs the entire length of the vertebral column.
277
Where would you insert an epidural needle?
Between the dura mater and vertebrae in order to inject anaesthesia.
278
Where would you insert a lumbar puncture needle?
At the L3/L4 level in the sub-arachnoid space in order to take CSF.
279
What is the conus medullaris?
The tapered, lower end of the spinal cord.
280
What is the filum terminale?
A fibrous strand that proceeds downwards from the apex of the conus medullaris.
281
What is the cauda equina?
Spinal nerves from the lower spinal cord that hang obliquely downwards.
282
Define dermatome.
An area of skin with a sensory nerve supply from a single root of the spinal cord.
283
What is the dermatome for the thumb?
C6.
284
What is the dermatome for the knee?
L3.
285
What is the dermatome for the big toe?
L5.
286
Name 4 ascending spinal pathways.
1. DCML. 2. Spinothalamic. 3. Spinocerebellar. 4. Spinoreticular.
287
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.
288
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.
289
Where is the somatosensory cortex located?
Post-central gyrus in parietal lobe.
290
What sensations is the lateral spinothalamic tract responsible for?
Pain and temperature.
291
What sensation is the anterior spinothalamic tract responsible for?
Crude touch + pressure
292
What is the function of the spinocerebellar tracts?
They carry unconscious proprioceptive information to the ipsilateral cerebellum.
293
Do the fibres decussate in the spinocerebellar tracts?
No! They go to the ipsilateral cerebellum.
294
What sensation does the spinoreticular tract convey?
Deep/chronic pain.
295
Name 5 descending pathways.
1. Corticospinal. 2. Vestibulospinal. 3. Rubrospinal. 4. Tectospinal. 5. Reticulospinal.
296
Where in the thalamus do the DCML and spinothalamic tracts synapse?
In the ventral posterio-lateral division (VPL) of the nucleus of thalamus
297
What descending pathways are described as pyramidal?
Corticospinal and corticobulbar tracts - responsible for voluntary control.
298
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.
299
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).
300
What are the corticospinal tracts responsible for?
The control of voluntary muscles. Anterior - axial muscles. Lateral - limb muscles.
301
Describe the corticospinal tracts.
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; the remaining 10% forms the anterior corticospinal tract. The anterior tract then decussates through the anterior white commissure. Both tracts terminate in the ventral horn.
302
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.
303
Where do the extrapyramidal tracts originate?
The brainstem.
304
Where do the vestibulospinal tracts originate and what are they responsible for?
1. Originate from vestibular nucleus. 2. Responsible for muscle tone and postural control. - Remains ipsilateral.
305
Where do the reticulospinal tracts originate and what are they responsible for?
1. Originate from reticular formation. 2. Responsible for spinal reflexes.
306
Where do the tectospinal tracts originate and what are they responsible for?
1. Originate from tectum nuclei (superior and inferior colliculi). 2. Responsible for head turning in response to visual and auditory stimuli.
307
Where do the rubrospinal tracts originate and what are they responsible for?
1. Originate from red nucleus. 2. Responsible for assisting motor functions. - Contralateral.
308
What tracts are known as the ventrolateral/anterolateral system?
Spinothalamic tracts.
309
Damage to the anterolateral system will present with what symptoms?
Contralateral loss of pain and temperature sensation.
310
What tracts are known as the dorsomedial system?
DCML.
311
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.
312
What is Brown-Sequard syndrome?
Hemi-section of the spinal cord.
313
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.
314
What are the 3 primary vesicles?
- Prosencephalon (forebrain). - Mesencephalon (midbrain). - Rhombencephalon (hindbrain).
315
What are the sub-divisions of the prosencephalon?
- Telencephalon. - Diencephalon.
316
What does the telencephalon form?
- The cerebral hemispheres.
317
What does the mesencehpalon form?
- Midbrain. - Colliculi.
318
What are the sub-divisions of the rhombencephalon?
- Metencephalon. - Myelencephalon.
319
What does the metencephalon form?
- Cerebellum. - Pons.
320
What does the myelencephalon form?
- Medulla oblangata.
321
Where are the lateral ventricles formed in the embryo?
Telencephalon.
322
Where is the 3rd ventricle formed in the embryo?
Diencephalon.
323
Where is the 4th ventricle formed in the embryo?
Rhombencephalon.
324
What are the pluripotent stem cells that lie within the neural folds?
Neural crest cells.
325
What do neural crest cells develop into?
Schwann cells, pigment cells, adrenal medulla, dorsal root ganglia, Cn 5, 7, 9 and 10.
326
How is the neural tube formed?
Notochord in mesoderm signals the ectoderm to form a thickened neural plate. Mitosis forms a neural groove. There are neural folds on either side of the groove. These fuse at the midline forming the neural tube.
327
When should the neural tube fuse?
By the end of the 4th week.
328
What vitamins are needed to ensure the neural tube fuses?
B9 (folic acid) and B12.
329
Approximately how much CSF do we have?
120ml.
330
What is hydrocephalus?
An accumulation of CSF in the ventricular system. Often due to a blockage in the cerebral aqueduct.
331
Name 4 substances contained within the CSF.
1. Protein. 2. Urea. 3. Glucose. 4. Salts.
332
Define axonal transmission.
Transmitting information from A to B.
333
Define synaptic transmission.
Integration/processing of information.
334
What are the 5 fundamental processes of neurotransmission?
1. Manufacture. 2. Storage. 3. Release. 4. Interaction with post-synaptic receptor. 5. Inactivation.
335
Give 2 examples of fast neurotransmitters. Do fast neurotransmitters have short or long-lasting effects?
- Ach, GABA. - Short lasting effects.
336
Give 3 examples of neuromodulators. Do neuromodulators have short or long-lasting effects?
- Dopamine, serotonin, noradrenaline. - Long lasting effects.
337
What is an endorphin?
A peptide with opiate-like effects. They inhibit the release of substance P.
338
How long does the refractory period last?
5-10ms.
339
What is the relative refractory period?
It follows the absolute refractory period. Reploarisation occurs as Na+ channels are close and K+ channels are open. A 2nd stimulus that is stronger than the first is needed to produce another AP in this case.
340
What are the 2 components of a refractory period?
The absolute refractory period which is followed by the relative refractory period.
341
What is the neuronal resting potential?
-70mV.
342
Define nociceptive pain.
Pain derived from actual damage to non-neural tissue, it is due to the activation of nociceptors.
343
Define neuropathic pain.
Pain caused by a primary lesion or dysfunction of the nervous system.
344
Describe C fibres.
- They are the smallest nerve fibres. - Unmyelinated and so have slow conduction speeds. - They have a high activation threshold meaning they detect selectively nociceptive stimuli.
345
Describe A-delta fibres.
- Small nerve fibres but larger than C fibres. - Thinly myelinated. - They have a high activation threshold.
346
What type of pain are A delta fibres responsible for?
The sensation of a quick, sharp, localised pain; 'first pain'.
347
What type of pain are C fibres responsible for?
C fibres respond to high-intensity stimuli. They are responsible for a slow, deep, spread-out pain; 'second pain'.
348
What is voluntary motor control?
Goal directed (conscious) or habitual (unconscious/automatic). E.g. running, walking talking etc.
349
Involuntary motor control examples?
Eye movements, facial expressions, posture, diaphragm etc.
350
Define motor unit.
A single alpha motor neurone and all the muscle fibres it innervates.
351
Do the finger tips have lots of muscle fibres or few muscle fibres?
Few muscle fibres. This allows for greater movement resolution.
352
Does function of a muscle affect how many muscle fibres there are?
Yes! The finger tips have few muscle fibres because they require greater movement resolution.
353
What are spinal reflexes?
- Involuntary, physiological responses to stimuli e.g. withdrawing your hand when you touch something hot. - Unlearned and instinctive: unconditioned responses.
354
Withdrawal reflex: what does reciprocal innervation of antagonistic muscles explain?
It explains why the contraction of one muscle induces the relaxation of the other; this permits the execution of smooth movements.
355
What nerve fibres innervate golgi tendon organs?
Afferent type 1b sensory nerve fibres (inhibitory).
356
What is a UMN?
A neurone that is located entirely in the CNS. Its cell body is located in the primary motor cortex.
357
What is a LMN?
A neurone that carries signals to effectors. The cell body is located in the brain stem or spinal cord.
358
What are the characteristic features of MS?
MS comes and goes and its symptoms are exacerbated after having a shower.
359
What is myasthenia gravis?
An autoimmune disease; antibodies destroy Ach receptors.
360
What are the signs of myasthenia gravis?
Weakness and tiredness. Actions like chewing become progressively much harder.
361
What does myasthenia gravis affect: LMN, UMN, neuromuscular junctions?
Neuromuscular junctions.
362
Where do the two optic nerves meet?
At the optic chiasm. The images from the two eyes are fused here.
363
Where do the optic tracts terminate?
Lateral geniculate body in the thalamus.
364
What is the dorsal stream?
The 'where' stream. It is thought to determine the objects spatial location. It travels through the parietal lobe.
365
What is the ventral stream?
The 'what' stream. It is thought to be involved in identification and recognition. It travels through the temporal lobe.
366
What occular muscles does the superior branch of Cn 3 innervate?
- Levator palpebrae superioris. - Superior rectus.
367
What occular muscles does the inferior branch of Cn 3 innervate?
- Medial rectus. - Inferior rectus. - Inferior oblique.
368
What occular muscle does Cn 4 innervate?
Superior oblique.
369
What occular muscle does Cn 6 innervate?
Lateral rectus.
370
What is the origin and insertion of levator palpebrae superioris?
Origin: common tendinous ring. Insertion: Upper eyelid.
371
What is the action(s) of the superior oblique on the eyeball?
- Intorsion. - Depression. - Abduction. (SODAbI)
372
What is the action(s) of the inferior rectus on the eyeball?
- Depression. - Extorsion. - Adduction. (IRA ED)
373
What is the action(s) of medial rectus on the eyeball?
- Adduction. (MR. A)
374
What is the action(s) of the superior rectus on the eyeball?
- Elevation. - Intorsion. - Adduction. (SIRAE)
375
What is the action(s) of inferior oblique on the eyeball?
- Extorsion. - Elevation. - Abduction.
376
What is the action(s) of lateral rectus on the eyeball?
- Abduction.
377
What is the function of the outer ear?
It gathers sound energy and focuses it on the tympanic membrane; this vibrates the tympanic membrane. The outer ear also amplifies sound.
378
What nerve provides general sensation to the outer ear?
Cn 10.
379
What 3 bones make up the ossicular chain?
Malleus, incus and stapes.
380
What is the smallest bone in the human body?
The stapes.
381
What is the function of the ossicles?
To transmit vibrations from the tympanic membrane to the oval window.
382
What nerve provides general sensation to the middle ear?
Cn 9.
383
What muscles can change the stiffness of the ossicular chain?
Stapedius and tensor tympani.
384
What nerve innervates stapedius?
Cn 7.
385
What nerve innervates tensor tympani?
Cn 5.
386
How do stapedius and tensor tympani change the stiffness of the ossicular chain?
They control the mobility of malleus and stapes and so protect the inner ear from loud noises.
387
What is the function of the round window?
It vibrates in the 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.
388
What is the function of the vestibular system?
Balance and spatial orientation.
389
What is the vestibular apparatus?
1. Otolithic organs: utricle and saccule. 2. 3 Semi-circular canals.
390
What do the semi-circular canals detect?
Angular acceleration.
391
What do the otolithic organs detect?
- Linear acceleration. - Changes in head position relative to gravity.
392
Where are vestibular hair cells located?
In the utricle and saccule and in 3 ampullae at the base of the semi-circular canals.
393
What is the function of the vestibular hair cells?
They detect changes in motion and position of the head by stereocilia transduction.
394
What are the 3 cavities of the cochlea?
1. Scala vestibuli. 2. Scala media. 3. Scala tympani.
395
Which of the cavities of the cochlea are filled with perilymph?
Scala vestibuli and scala tympani.
396
What is the helicotrema?
Where the scala vestibuli and scala media meet.
397
What is the scala media filled with?
Endolymph.
398
Which cavity of the cochlea houses the organ of corti?
The scala media.
399
What does the organ of corti sit on?
The basilar membrane.
400
What is the stria vascularis?
A structure involved in the active transport of K+ into the scala media.
401
What is the potential of the scala media?
+80mV.
402
What are the 3 structures that make up the organ of corti?
1. Hair cells. 2. Supporting cells. 3. Auditory nerve fibres.
403
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.
404
Which hair cells have 95% afferent nerve fibres?
Inner hair cell's (OHC's - efferent).
405
Is the base or the apex of the basilar membrane wider?
The apex.
406
Is the base or the apex of the basilar membrane more sensitive to high-frequency sounds?
The base.
407
What structures are present on the IHC's and OHC's?
Stereocilia.
408
What structures connect adjacent stereocilia?
Tip links.
409
What happens to the stereocilia when the basilar membrane vibrates?
They bend. This opens the hair cells' ion channels and there is an increase in auditory nerve firing.
410
True or False; antibiotics can damage stereocilia.
True!
411
Describe the I'MAuditory pathway.
Inferior colliculi -\> inferior brachium -\> medial geniculate body. - Concerned with the reflex of looking towards a loud noise.
412
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.
413
Name 4 disorders associated with basal ganglia dysfunction.
1. Huntington's disease. 2. Parkinson's disease. 3. ADHD. 4. OCD.
414
What is the reason behind the signs of PD?
Not enough dopamine.
415
What are the signs of parkinson's disease?
1. Tremor. 2. Bradykinesia. 3. Rigidity.
416
What is the reason behind the signs of HD?
Too much dopamine.
417
What are the signs of Huntington's disease?
1. Chorea (jerky, involuntary movements). 2. Dementia. 3. Personality change.
418
Briefly describe how dopamine is produced.
Tyrosine -\> L-dopa -\> dopamine.
419
What is the function of the limbic system?
The limbic system is involved with emotion, behaviour, long-term memory, olfaction and motivation. It is also thought to have a role in learning.
420
What is the papez circuit?
A circuit that connects the main structures of the limbic system. It is involved in memory and emotions.
421
How would the eye appear to the examiner if a patient is diagnosed with a lesion to Cn 3?
down and out' due to unopposed action of lateral rectus and superior oblique.
422
Why would ptosis (drooping of the eyelid) occur?
If there was a loss of innervation to levator palpebrae superioris.
423
Where are Cn 1 nuclei located?
Olfactory bulb.
424
Where are Cn 2 nuclei located?
Lateral geniculate body.
425
What structures lie anteriorly to the cerebellum?
The pons and medulla. The 4th ventricle lies in between these and the cerebellum.
426
What is the midline of the cerebellum called
The vermis.
427
What are the two fissures of the cerebellum called?
- The primary fissure. - The horizontal fissure.
428
What are the lobes of the cerebellum hemispheres called?
The anterior and posterior lobes.
429
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.
430
What are the 3 layers of the cerebellar cortex?
- Molecular (outermost). - Purkinje. - Granular.
431
What are the 2 inputs into the cerebellum?
- Climbing fibres. - Mossy fibres.
432
Where do the mossy fibres come from?
They come from the pons via the middle cerebellar peduncle.
433
Where do the climbing fibres come from?
The come from the olivocerebellar nuclei via the inferior cerebellar peduncle.
434
What do the inferior cerebellar peduncles do?
They connect the medulla and the cerebellum and convey muscle proprioception and vestibular inputs.
435
What do the middle cerebellar peduncles do?
They connect the pons and the cerebellum and they 'tell' the cerebellum about voluntary motor outputs.
436
What is the output from the cerebellum?
Purkinje cell axons.
437
Where do the purkinje cell axons go to?
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.
438
What do the superior cerebellar peduncles do?
They connect the midbrain and the cerebellum and carry mostly efferent fibres.
439
Name 4 cerebellar nuclei.
1. Dentate. 2. Emboliform. 3. Globose. 4. Fastigial.
440
What is the affect on movement in cerebellar injury?
Movements are slow and uncoordinated.
441
What are some symptoms of the cerebellar injury?
- Loss of coordination. - Inability to judge distances. - Intention tremor. - Staggering, wide-based walking. - Weak muscles.
442
What is the peripheral nervous system?
The nervous system outside the brain and spinal cord. It includes the cranial nerves (except 1 and 2) and the spinal nerves.
443
Is the CNS or the PNS protected by the blood-brain barrier?
The CNS.
444
What spinal nerves innervate the biceps reflex?
C5/6.
445
What spinal nerves innervate the ankle reflex?
S1/2.
446
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).
447
Where does the spinothalamic tract decussate?
Within the spinal cord, 2-3 spinal segments above.
448
A patient can understand what you're saying but is unable to construct sentences in response. What part of the brain is affected?
Broca's area in the dominant frontal lobe.
449
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 keyword here.
450
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.
451
A man presents to the stroke unit being unable to move/feel his right arm, with right-sided facial drooping and slurred speech. Which artery has been affected?
Left middle cerebral artery.
452
A woman presents to the stroke unit with complete right sided visual field loss. Which artery has been affected?
Left posterior cerebral artery.
453
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).
454
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.
455
A 42-year-old female has presented with weakness in her left leg. She has been seen previously in your clinic two years ago for visual disturbance and sensory loss over the left forearm. These symptoms persisted for several weeks but then gradually resolved. Her symptoms are exacerbated following a shower. What is the problem?
Multiple Sclerosis (characterised by the fact it comes and goes. Exacerbated after a shower is also a key feature of this disease).
456
A 30-year-old woman noticed that her face had become progressively droopier whilst putting her make-up on in the mornings. Weeks later she began to experience double vision, and found it progressively more tiring and difficult to chew all the food in her mouth when eating. What is the problem?
Myasthenia Gravis (characterised by progressive weakness and tiredness. Actions like chewing become much harder. It is a neuromuscular junction disease where the Ach receptors are blocked).
457
A man has presented with a history of weakness in both of his hands, he is now unable to open jars. Both of his hands show wasting in the Thenar eminence. He has developed slurred speech and difficultly swallowing over the past 3 weeks. His tongue appears spastic and he is unable to protrude it. What is the disease?
Motor neurone disease - both UMN and LMN are affected.
458
What is the only cranial nerve to emerge from the dorsal aspect of the brainstem?
Trochlear Cn 4.
459
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 patient’s retinal representation of this student’s face image?
The retinal image is converted from right to left and reversed. The student's face is now in the left lower corner. (Medical student is standing on your left but that is the patient's right).
460
What are the functions of cones in the eye?
Cones are important for visual acuity and colour vision.
461
What are the functions of rods in the eye?
Rods are important for peripheral vision.
462
Define pain.
An unpleasant sensory and emotional experience associated with actual tissue damage.
463
Where is the insula located?
Deep in the lateral sulcus.
464
What is the role of the insula in pain recognition?
The insula contributes to the subjective perception of pain. It is where the degree of pain is judged.
465
What is the role of the cingulate gyrus in pain recognition?
It provides an emotional response to pain.
466
What is the Melzack Wall pain gate?
The idea that non-painful input can close the 'gate' to painful input and so prevent it from reaching the CNS. Non-noxious stimuli can prevent pain as the large fibres can override the small pain fibres. It is a physiological explanation for why 'rubbing it better' can help.
467
What is the effect of stimulating opioid receptors?
It can reduce neuronal sensitivty and so reduce the pain sensation.
468
How can opioids be used as analgesia?
They bind to inhibitory G-protein coupled receptors in the brain/spinal cord.
469
What is a neuromuscular junction?
A chemical synapse formed by the contact between a motor neurone and a muscle fibre.
470
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.
471
What would be the affect of damage to the cerebellar vermis?
Balance problems due to loss of postural control. Difficulty in sitting and standing up.
472
What would be the affect of damage to the cerebellar hemispheres?
Ipsilateral impaired limb coordination.
473
What do the middle cerebellar peduncles convey?
They send information from the primary motor cortex about the motor plan to the cerebellum - corticopontocerebellar tract.
474
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.
475
What afferent signals do the superior cerebellar peduncles convey?
Ipsilateral information on proprioception and balance from the ventral spinocerebellar tract.
476
What efferent signals do the superior cerebellar peduncles convey?
Efferent signals from the dentate nucleus that go to the red nucleus and thalamus.
477
Give 4 treatments for pain.
1. Analgesics. 2. Acupuncture. 3. Exercise. 4. Hypnotherapy.
478
In Huntington's disease what area of the basal ganglia and what neurotransmitters are affected?
- Striatum (caudate nucleus). - GABA.
479
What site does brain stimulation affect?
Sub-thalamic nucleus.
480
What neurotransmitter is in deficit in Huntington's disease?
GABA.
481
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.
482
How do men and women differ in their response to pain?
Women report pain more readily but can tolerate more pain than men.
483
Where do sympathetic nerves come from?
T1 -\> L2 spinal nerves.
484
Where do parasympathetic nerves come from?
Cn 3, 7, 9 and 10, S2 -\> 4.
485
What neurotransmitter do sympathetic and parasympathetic nerves both use at ganglia?
Ach.
486
What week does the neural tube fuse?
Week 4.
487
What is spina bifida?
Failure of the neural tube to close in the spinal cord region.
488
What is the visual pigment in the eye?
Rhodopsin.
489
What is the function of hair cells?
Through transduction they convert mechanical stimuli into electrochemical activity and they also have a role in amplification.
490
What is the somatic nervous system?
A part of the peripheral nervous system that handles voluntary control of body movements.
491
What are the anatomical divisions of the nervous system?
The CNS (brain and spinal cord) and the PNS (cranial nerves and spinal nerves).
492
What are the functional divisions of the nervous system?
Somatic (voluntary control) and autonomic (involuntary control, further subdivided into sympathetic and parasympathetic).
493
Describe how the brain maintains its blood flow in response to hypovolemia.
Cerebral autoregulation. Hypovolemia leads to a decrease in BP and so the cerebral arterioles dilate more so as to maintain blood flow.
494
What nerve provides sensory innervation to the oropharynx?
Glossopharyngeal - Cn 9.
495
What nerve provides sensory innervation to the laryngopharynx?
Vagus - Cn 10.
496
What nerve provides sensory innervation to the nasopharynx?
Maxillary branch of the trigeminal - Cn 5(b).
497
Which part of the brain is activated in acupuncture?
Cingulate gyrus.
498
Which part of the brain has a role in addiction?
The insular cortex.
499
Stimulation of which part of the brain can result in profound analgesia?
PAG
500
Give 3 types of glial cells in the CNS.
1. Astrocytes. 2. Oligodendrocytes. 3. Microglia.
501
Neurones communicate via 2 types of synapses. What are they?
1. Chemical - majority. 2. Electrical.
502
Mutation of what protein can result in duchenne?
Dystrophin.
503
What is the function of dystrophin?
It provides structural stability to muscle cell membranes.
504
Which cranial nerve can be tested in the unconscious patient by observing pupillary constriction in response to light?
Optic - CN2.
505
What would pouring ice cold water in the external auditory meatus cause?
Convection currents in the semi-circular canals which results in nystagmus.
506
What is the entry/exit foramina for the ophthalmic artery?
Optic canal.
507
What is the entry/exit foramina for the superior ophthalmic vein?
Superior orbital fissure.
508
What is the entry/exit foramina for the labyrinthine artery?
Internal acoustic meatus.
509
What are the two types of deafness?
1. Conductive - sound is blocked from getting through. 2. Sensory neural - the problems are with the nerves.
510
Where does the substantial nigra project to?
The striatum.
511
What are the three branches of the trigeminal nerve
V1- Ophthalmic V2- Maxillary V3- Mandibular
512
What is the brain stem responsible for?
basic vital functions (breathing heart rate)
513
What is the corpus callosum
fibre bundle connecting left and right cerebral hemispheres
514
% of neurones present in the cerbellum
70%
515
How are structures connected to the cerebellum
Re-entrant loops
516
Neurons + stain
H&E: Haemotoxylin stain Nucleic acids are stained blue Eosin stains proteins red Luxor fast blue (LFB) stains myelin Cresol violet stain Nissl
517
CSF Outflow
Lateral Ventricles → interventricular Foramina (Monro) → Third ventricle → Cerebral Aqueduct → Fourth Ventricle → Apertures → Subarachnoid Space → Sinuses Liquid Inside The Cerebrum Flow Around Subarachnoid Space
518
How do local anaesthetics work?
Interrupt axonal transmission Block sodium channels preventing the neurone from depolarising, meaning that threshold frequency isn't met and therefore, no action potential is produced This results in pain, and pain isn't transmitted
519
Blood supply of eye
Internal carotid artery: Ophthalmic artery, Lacrimal Artery, Ethmoid Artery, Eyelid artery, Ciliary Artery External carotid artery: Facial artery
520
Internal rotation
Towards midline
521
Extorsion
Away from midline
522
Eye muscles (diagram)
523
Acute pain
Short term pain of fewer than 12 weeks. Chronic pain is for more than 12 week
524
What is the Periaqueductal grey
area of gray matter that surrounds the cerebral aqueduct in the brainstem
525
What is PAG best known for
analgesia, or pain reduction

Sandra phase 1 (16 decks)

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