Neurology Flashcards
1
Q
What is Nissl substance and where is it located?
A
Located in the Perkaryion (cell body) Combination of ribosomes and endoplasmic reticulum
2
Q
What part of the neurone mediates “all or nothing” principal?
A
Axon hillock Highest concentration of voltage gate ion receptors
3
Q
How is strength of action potential conveyed?
A
Frequency of signals NOT MAGNITUDE
4
Q
What is a golgi type 1 neurone?
A
Neurone with a long axon
5
Q
What is a golgi type 2 neurone ?
A
Neurone with short axon
6
Q
What pathology occurs through retrograde axonal transport?
A
Viruses e.g. policyelitis, herpes and rabies
7
Q
What type of neurones are lower motor neurones?
A
Multipolar cell ( three or more synapses) Lower motor neurones are the most common type of neurone
8
Q
What is an example of a unipolar neurone?
A
Peripheral autonomic neurones
9
Q
If a neurone is in the ventral horn of the spinal cord, what is its function?
A
Motor
10
Q
If a neurone is in the dorsal horn of the spinal cord, what is its function?
A
Sensory
11
Q
Where are interneurones located and what are their function?
A
CNS Connection between neurones in the CNS
12
Q
What is the role of a projection neurone?
A
Conveys action potential to higher brain structures Located in dorsal horn
13
Q
What does the peripheral nervous system comprise of?
A
31 Spinal nerves
Rami (sensory + motor) –> Spinal nerve (sensory+motor) –> root (seperated sensory and motor)
14
Q
Describe the events of how an aciton potential arrises?
A
At rest: Voltaged gated channels are closed but responsive
Depolarisation: Na+ channels open, K+ channels remain closed
Maximum depolarisation: Na+ channels inactivate, K+ channels open
Depolarisation: K+ channels remain open, channels remain inactivated
At rest again
15
Q
What is the resting membrane potential of a neurone and how is this maintained?
A
-70 mV
Efflux of potassium ions
16
Q
What is the gradient of Potassium and Sodium in a neurone?
A
Potassium high intracellular
Sodium high extracellular
Na/K pump transports 3 Na+ out of cell fo 2 K+ to entre cell
17
Q
What is the refractory period of a neurone?
A
Absolute Refractory Period
Interval of inactivation, due to voltage gated sodium channels
Another action potential cannot overcome this or triggera second action potential
This occurs over the overshootto the beginning of the undershoot
Relative Refractory Period
Interval in which a second action potential can be generated
Due to undershootbypotassium effluxfrom downstroke
A large enough action potentialcan overcome this
This occurs on the downstroke to the resting potential
18
Q
Describe the polarity of the extracellular and intracellular membranes of a neurone when an action potential moves along the neurone?
A
As the action potential moves, the polarity is reversed from + outside to - outside and from - Inside to + inside
Each action potential is associated with a influx of positively charged sodium ions
19
Q
What disease is caused by demyelination of CNS cells?
A
Multiple sclerosis
Central demyelination (olgiodendrocytes)
20
Q
What disease is caused by peripheral demyelination?
A
Guillain Barre Syndrome (Schwann cells)
21
Q
What are the features of an excitatory neurone synapse?
A
Neuotransmitter: Glutamate
Glutamate acts on postsynpatic cation selective inotropic glutamate receptors
Depolarisation induced from Na+ influx
22
Q
What are the features of an inhibitory synapse?
A
Neurotransmitter: GABA / Glycine
Acts on postsynaptic anion inotropic GABA/Glycine receptors
Influx of Chloride ions (Hyperpolarisation)
23
Q
What effect does influx of anions have on a neurone?
A
Hyperpolarisation (Neurone becomes more negative)
Inhibitory effect
24
Q
Describe how a synapse works?
A
25
What neurone transmitters are present in cells and do not require synthesis?
Glutamate
Glycine
26
What neurontransmitter requires synthesis from cells?
GABA
27
With regards to ion movement, how may depolarisation of a neurone occur?
Influx of: Na+ K+ Ca2+
Efflux of : Cl-
28
What regards to ion movement how may hyperpolarisation of a neurone occur?
Influx of: Cl-
Efflux of: Na+, K+, Ca2+
29
What are the excitatory neurotransmitters?
Acetylcholine (most widespread)
Noradrenaline
Adrenaline
5HT (Serotonin)
Dopamine
Glutamate
Aspartate
30
What are the inhibitory neurotransmitters?
GABA
Glycine
Histamine
31
What are excitatory and inhibitory neurotransmitters?
Neuropeptides:
Vasopressin
ACTH (adenocorticotrophic hormone)
Substance P
Opioids peptides
ATP
AMP
32
What is the unite for measuring neurotransmitter?
Quanta
33
What types of cells are pyramidal cells and what is their function?
Excitatory CNS Neurones
Located in:
Cerebellum (Cortex)
Hippocampus
Amygdala
34
What types of cells are purkinje cells and where are they located?
Inhibitory effect
Located in cerebellum (middle layer of cerebellum)
35
What two types of receptors are on the post synpatic neurone
Ionotropic ion receptors: Fast
Metabotropic ion receptors: Slow
36
What are the features of a ionotropic receptor?
Ligand gated channels
Fast transmision
Associated with glutamate/ GABA Neurotransmitters
37
What neurotransmitters are associated with ionotropic receptors?
Glutamate (Excitatory)
GABA (Inhibitory)
38
What neurotransmitters work on pentameric ligand gated channels?
GABA (Inhibitory)
Glycine (Inhibitory)
ACH (Excitatory)
39
What neurotransmitter works on tetrameric ionotropic receptors?
Glutamate (Excitatory)
40
What are the features of a metabotropic receptor?
Slow tranmission
Transmission through indirect gating
G protein coupled receptors (Release of GTP to activate respective ionotropic channel)
Function: Long term neuromodulation
41
What are the two types of ionotropic glutamate receptors?
(Classified according to response to N-Methyl- D- aspartate )
1. AMPA / Non-NMDA Receptors
2. NMDA receptors
42
What are the features of AMPA/Non-NMDA receptors?
Mediates fast excitatory synaptic transmission
Permeable to sodium and leads to depolarisation
They are impermeable to calcium
Tetramer receptor
43
What are the features of NMDA receptors?
Excitatory
Mediates long term neuromodulation(neuroplasticity)
Influx of Na+/Ca+
Efflux of K+
Inhibited by Mg+ ions
44
What is the function of metabotropic glutamate receptors?
Presynaptic inhibition
45
How do glutamate receptors work at the retina?
Glutamate receptors of the retina are important for the bipolar cells, in switching on and off
Inotropic glutamatereceptors switch on
Metoptropic glutmatereceptors switch off
46
What are the two major types of GABA receptors?
GABAa - Ionotropic receptor - influx of Cl- (Fast)
GABAb - Metabotropic receptor - K+ efflux (Slow)
47
How does BZD's work?
Modulate GABAa receptor (inotropic GABA receptor)
Enhance Cl- entry, leading to hyper polarisation
Enhances inhibitionin the presence of GABA
48
How does Baclofen work?
Agonist of GABAb receptor (potassium channel agonist)
Enhances potassium efflux
Increases inhibition
49
What is a excitatory post-synaptic potential ?
A depolarising change in the resting membrane potential caused by excitation
Multiple EPSPS/Large EPSPS can cause the resting membrane potential to cross over threshold and result in an action potential
50
What is an inhibitory postsynaptic potential?
Negative change in resting membrane potential causes by inhibitory action
Inhibits crossing of threshold and inhibits action potential
51
What are the sensation modalities of the somatosensory system?
Exteroceptive - Cutaneous senses
Proprioceptive
Visceral sensation
Deep sensation (muscle fascia bone)
52
How does mechanosensation work?
Greater the sensation, the greater the receptor potential is observed
Increased receptor potential elicits a greater frequency of action potentials
53
What is neural adaption?
Adaption is a feature of primary sensory neurone that allows them to change the firing rate
54
What are examples of slow adapting receptors?
Receptors that convey continuous information to the CNS e.g. Stretch receptors
55
What are examples of rapidly adapting receptors?
Receptors that detect changes in stimulus strength
e.g. muscle spindle afferents
Hair follicle afferents
56
What are examples of rapidly adapting receptors?
Pacinian capsules
57
What are the four types of sensory neurones?
A alpha fibres
A beta fibres
Adelta fibres
C fibres
58
What are the featrues of a A alpha fibre?
Thick fibres
Fast conducting
Purpose: Proprioception
59
What are the features of A beta fibres?
Medium fibre
Mechanoreceptors of skin: (touch, pressure, vibration)
60
What are the features of A delta fibres?
Thin
Purpose : Pain and temperature
Myelinated
61
What are the features of a C fibre?
Thin unmyelinated fibres
Purpose: Pain and temperature
62
What do meissner corpuscles detect?
Mechanosensation - light touch, stroking, flutter (vibration)
Rapidly adapting receptors
High frequencyin regions with a large two point discrimination
Not present in hairy skin
A beta fibres
63
What do merkle cells detect?
Detect Pressure
Slow adapting receptors
Grouped in Iggo domes
High frequency in region with large two point discrimination
Present in hairy skin
A beta fibres used
64
What do Krause end bulbs detect?
Receptors found at the border ofdry skin and mucous membrane
Detects cold
65
What do ruffini endings detect?
Located within dermis and joint capsules
Detects warmth
66
What do C mechanoreceptors detect?
Erotic touch
Stroking
67
What is the dermatomal level of the shoulder?
C4
68
What is the dermatomal level of the nipple?
T4
69
What is the dermatomal level of the xiphisternum?
T6
70
What is the dermatomal level of the umbilicus?
T 10
71
What is the dermatomal level of the thumb?
C6
72
What is the dermatomal level of the knee?
L4
73
What is the dermatomal leve of the dorsum of the foot?
L5
74
How is the grey matter organised?
Laminae of Rexxed
| (10 raminae in total)
75
Where do Nociceptors insert into the laminae of rexxed?
Laminae I and Laminae II
Used : A delta and C fibres
76
Where do mechanoreceptors insert into the laminae of rexxed?
Laminae III - VI
Fibres A beta
77
Where do proprioceptors insert into the laminae of rexxed?
Laminae VII - IX
78
What happens to white matter as you move up the spinal cord?
White matter incrases as you move up
79
What is the termination of the spinal cord called?
Connus medularis
80
What holds the spinal cord in the subarachnoid space?
Denticulate ligament
Fillum terminale
81
What is the blood supply of the spinal cord?
**3 longitudinal vessels:**
2 posterior arteris - supplies dorsal third
1 anterior artery - supplie ventral thid
**Reinforced by segmental arteries ( e.g. the artery of adamkiewicz)**
82
Describe how the spinal cord is organised?
83
What are the features of the dorsal collum medial lemniscus pathway?
Dorsal Columns
(fasiculus gracilus+ fasiculus cunetatus)
Mode: fine touch, vibration and proprioception
Cell body in dorsal root ganglion
Decussation: in medulla forming medial lemniscus
84
What are the functions of the fasiculus gascilis and the fasiculus cuneatus?
FG: carries sensory firbes of lower limbs
FC: carries sensory fibres of upper limb
85
What are the features of the lateral spinaothalamic tract?
Lateral Spinothalamic Tract
Mode: pain and temperature
Cell body in dorsal root ganglion
Decussation: in cord, at entry leve
86
What are the features of the lateral corticospinal tract?
Lateral Corticospinal Tract
Mode: motor (body)
Cell body: Primary motor cortex
Decussation: pyramidal decussation in ventral medulla
87
What are the different types of thalamic nuclei?
** Ventro posterolateral** - reciveves somatosensory body information
**Ventro posteromedial** - recieves somatosensory head information
** Lateral geniculate nucleus** - recieves visual information
**Medial geniculate nucleus** - recieves auditory
88
What is the function of the basal ganglia?
Regulation of posture, locomotion, coordination and movement
89
How do the basal ganglia send output action potentials?
Via the thalamus --\> cortex
90
What is the functional of the internal capsule?
White matter carrying axonal fibres from motor cortex to pyramids of medulla.
91
What is the function of the frontal lobe?
Cognition and memory
Executive function
Motor cortex
Dominant hemisphere: motor speech (Broca’s area)
92
What is the function of the parietal lobe?
Sensory cortex
Body orientation
93
What is the function of the temporal lobe?
Memory
Dom hemisphere: receptive language (Wernicke’s)
94
What is the function of the occpital cortex?
Visual cortex
95
Describe the route of the motor tracts?
1. Pre central gyrus
2. Internal capsule
3. Cerebral peduncle (midbrain)
4. Basis pontis (pons)
5. Decussation at pyramids of medulla
6 . Spinal cord
96
Describe the route of dorsal column?
1. Dorsal column (FG or FC)
2. Straight up cord to medulla
3. Nucleus gracillus or nucleus cunteatus (medulla)
4. Decussation at medulla via the medial lemniscus
5. Medial lemniscus through pons
6. Medial lemniscus through midbrain
7. Ventro posteriolateral nucleus of thalmus
8. Thalmus to **post central gyrus**
**(S for sensory)**
97
Describe the route of the spinothalamic tract?
1. Decussation immediately at cord entry level
2. Entry into spinothalamic tract all the way to thalamus
3. Synapse at ventro posterolateral nucleus of the thalamus
4. VPL to post central gryus
98
Describe the nuclei of the craial nerves at the brainstem?
Midbrain: 3, 4, (5)
Pons: 5, 6, 7, 8
Medulla: (5), 9, 10, 11, 12
99
What is the role of the mesencephalic nucleus of the trigmeninal nerve?
Proprioception of jaw
Motor to muscles of mastication (masseter, temporalis, ptyergoid)
100
What is the role of the spinal nucleus of the trigeminal nerve?
Senosry input: deep/crude touch, pain, and temperature from the ipsilateral face.
101
What is the function of the tactus solitarius?
Recieves stretch and chemoreceptor information from CVS and respiratory system
Taste sensation from: VII, IX, X
102
What cranial nerve nuclei are in charge of salivation?
Cranial nerves: VII + IX
103
What is the function of the nucleus ambiguus?
**Motor nucleus**
Stylopharyngeus via CN: IX
Muscles of the palate, pharynx, upper esophagus, and larynx via the vagus nerve (CN X)
104
Describe transmission of the action potential at the neuromuscular junction?
1. Presynaptic voltage-gated Ca2+ channels open → Ca2+ influx
2. ACh vesicles released from presynaptic terminal
3. ACh diffuses across cleft
4. ACh binds to nicotinic receptors on post-synaptic terminal
5. Na+ influx → depolarisation → Ca2+ release from SR → muscle contraction
6. ACh is degraded by acetylcholinesterase and choline is taken up into presynaptic terminal.
105
How may ACH action at the NMJ be blocked?
**_Blockade_**
**1. Block presynaptic choline uptake:** hemicholinium
**2. Block ACh vesicle fusion:** botulinum, Lambert eaton myasthenic syndrome (LEMS)
**3. Block nicotinic ACh receptors**
- Non-depolarising: atracurium, vecuronium
- Depolarising: suxamethonium
106
What are the dopaminergic pathways?
Mesocorticolimbic
Nigrostriatal:
Tuberoinfundibular:
107
What dopamine pathway is affected in schizophrenia?
Mesocorticolimbic
108
What dopamine pathway is affected in parkinsonism?
Nigrostriatal
109
What dopaminergic pathway is affected in hyperprolactinaemia?
Tuberoinfundibular
110
Describe the route of sympathetic neurones?
Cell bodies located in T1-L2
General visceral afferent synapse at:
Paravertebral ganglia
Prevertebral ganglia
Chromaffin cells of adrenal medulla
111
What is the NT in postganglionic and pregangionlic neurones in the sympathic nervous system?
Preganglionic neurones: NT = Ach, acts on nicotinic receptors
Postganglionic: NT= Noradrenaline, acts on adrenoergic receptors
Preganglionic neurones are myelinated
Postganglionic neurones are unmyelinated
112
What cranial nerves are parasympathetic?
3
7
9
10
113
What is the NT in preganglionic and postganglionic neurones in the parasympathetic nervous system?
Both ACh
114
What are the parasympathetic ganglia and their function?
Ciliary: ciliary muscle and sphincter pupillae
Pterygopalatine: mucus mems of nose and palate, lacrimal gland
Submandibular: submandibular and sublingual glands
Otic: parotid gland
Vagus supplies thoracic and abdo viscera
Sacral: pelvic splanchnic nerves (S2-4) innervate pelvic viscera
115
Does cranial nerves innervate the ipsilateral or contralateral side?
All cranial nerves exceptor CN IV (Trochlear) innervate ipsilateral side
Trochlea deccusates at level of the pyramids in the medulla
116
Describes the nerves invovled in the vestibulo-occular reflex?
Axons of the vestibular nerve project via the medial longitudinal fasiculus (MLF)
## Footnote
**Reflex: Head turns L → eyes turn R**
117
How can the vestibulo-ccular nerve be tested?
**Caloric Testing**
Warm and cold water is irrigated into the external auditory meatus
Warm → ↑ firing of vestibular N. → eyes turn to contralateral side c¯ nystagmus to ipsilateral side
**Remember fast direction of nystagmus – COWS**
Cold: Opposite Warm: Same
**_Absence of eye movements = brainstem damage on side being tested_**
118
Describe visual field defects caused by lesions affecting the optic nerve?
Optic nerve: Complete blindness in eye
Optic chiasm: Bitemporal hemianopia
Optic tract: Homonymous hemianopia
Lower optic radiation: upper quadrantanopia
Upper optic radiaiton: Lower quadrantanopia
Occipital cortex: Hemianopia with macula sparing
119
Describe the pupillary light reflex?
Affect: Sensory part of optic nerve
Efferent: Oculomotor nerve
**Occulomotor will also cause vasoconstrction due to Edinger - Westphall nucleus)**
120
