Neurophysiology Flashcards
1
Q
what is the node of ranvier
A
gap in myelin sheath on the axon of certain neurons
2
Q
What is the axon hillock and initial segment
A
site of initiation of the ‘all or none’ action potential
3
Q
local interneurone
A
e.g. between neurones in CNS
4
Q
3 types of neurone
A
sensory
motor
interneurone
5
Q
what causes the upstroke/rapid depolarisation of the neurone action potential
A
voltage gated sodium channels open, allowing sodium influx
6
Q
what causes the downstroke of neurone action potential
A
potassium leaves cell and sodium channels inactivate
7
Q
why do passive cells not spread far from their site of origin?
A
the nerve cell membrane is ‘leaky’ (imagine the axon is a leaky garden hose)
8
Q
what is the relationship between the diameter of axons and the resistance
A
the bigger the diameter, the lower the resistance, so faster conduction
9
Q
strategies to increase passive current speed
A
- increase axon diameter
- myelin
10
Q
what is myelin produced by?
A
Schwann cells in PNS
Oligodendrocytes in the CNS
11
Q
is conduction faster in myelinated or nonmyelinated axons of the same diameter
A
myelinated
12
Q
name 2 demyelinating disorders
A
- multiple sclerosis (CNS)
- Guillain-Barre syndrome (PNS)
13
Q
what are the 8 steps of chemical neurotransmission
A
- uptake of precursor
- synthesis of transmitter
- storage of transmitter
- depolarisation by action potential
- Ca2+ influx through voltage-activated Ca2+ channels
- Ca2+ induced release of transmitter (exocytosis)
- Receptor activation
- Enzyme-mediated inactivation of transmitter or reuptake of transmitter
14
Q
where are vesicles found and what do they store
A
- presynaptic terminal
- neurotransmitter
15
Q
acetylcholine, amino acids and amines are released from _______ vesicles
A
synaptic
16
Q
peptides are released from ______ vesicles
A
secretory
17
Q
do inotropic ligand-gated ion channels mediate fast or slow neurotransmission?
A
fast
18
Q
do metabotropic G-protein-coupled receptors mediate fast or slow neurotransmission?
A
slow
19
Q
direct gating is by ______ receptors
A
inotropic
20
Q
indirect gating is mediated by activation of _________ receptors
A
metabotropic
21
Q
AMPA and kainate are examples of which type of receptors
A
Non-NMDA
(fast)
22
Q
What are non-NMDA receptors?
A
a class of ionotropic glutamate receptors found in the CNS
23
Q
do NMDA receptors contribute a slow or a fast component to the excitatory synaptic potential
A
slow
24
Q
what is the main inhibitory neurotransmitter in the CNS
A
GABA
25
What 2 types of receptors does GABA act on
- inotropic GABA A receptor
- metabotropic GABA B receptor
26
are these neurotransmitters excitatory or inhibitory:
a) glutamate
b) GABA
a) excitatory
b) inhibitory
27
where are purkinje cells found
cerebellum
28
where are the inhibitory basket cells commonly found
- cerebellum
- hippocampus
- cortex
29
what is the calyx of held synapse
a giant terminal, something to do with the auditory system
30
true or false, a neurone typically has multiple synaptic contacts from multiple cells
true
31
what is transduction
conversion of physical stimulus into electrical signal
32
For a sensation to arise, what four events typically occur?
1. stimulation of the sensory receptor
2. transduction of the stimulus
3. generation of nerve impulses
4. integration of sensory input
33
graded potentials (not APs) vary in amplitude depending on what?
the strength of the stimulus that causes them
34
what do nociceptors respond to
painful stimuli
35
which sensory receptors detect chemicals in the mouth (taste), nose (smell) and body fluids
chemoreceptors
36
what do osmoreceptors detect?
the osmotic pressure of body fluids, particularly the concentration of dissolved ions and solutes, such as sodium and glucose, in the blood and CSF
37
Where does the pyramidal corticospinal pathway originate
Motor cortex
38
Lateral corticospinal tract - where do upper motor neurons decussate
Pyramids
39
Anterior/ventral corticospinal tract - where do upper motor neurons decussate
Levels of spinal cord
40
Which spinal tract regulates fast and fine (skilled) movements
Corticospinal (lateral and anterior/ventral)
41
What does a lower motor neuron connect?
Upper motor neuron to the skeletal muscle it innervates
42
Where does the cell body of a LMN lie?
Within the ventral horn of the spinal cord or the brainstem motor nuclei of the cranial nerves which have motor modalities
43
LMNs exit spinal cord via _________ roots
Ventral/anterior
44
The anterior/ventral corticospinal tract is responsible for the control of the ___________ musculature
Proximal
45
The lateral corticospinal tract is responsible for the control of the __________ musculature
Distal
46
Where do UMNs originate
a) in the pyramidal tracts
b) in the extrapyramidal tracts
a) cerebral cortex
b) within nuclei in the brainstem
47
What tracts are included in ‘extrapyramidal motor tracts’
- rubrospinal
- reticulospinal
- vestibulospinal
- tectospinal tracts
48
What do extrapyramidal motor tracts regulate
- axial muscles that maintain balance and posture
- muscles controlling coarse movements of the proximal portions of limbs
- head, neck and eye movement
49
Where does the rubrospinal tract originate
Red nucleus of the midbrain
50
What would excitation of the rubrospinal tract typically cause
Excitation of flexor muscles
Inhibition of extensor muscles
51
Where do the vestibulospinal tracts originate
Vestibular nuclei
52
Which type of tract is involved in posture, and in supporting the body against force of gravity, mainly targeting extensors
Vestibulospinal
53
Where do the tectospinal tracts originate
Superior colliculi (paired structures located in the midbrain of the brainstem)
54
What do the tectospinal tracts mediate
Orienting towards visual targets
55
Where does the reticulospinal tract originate
Reticular formation
56
What is the reticular formation
A diffuse collection of neurons in the pons and medulla where the reticulospinal tract originates
57
The reticulospinal tract is involved in balance, true or false
True
58
What are betz cells
Upper motor neurons that send their axons down to the spinal cord via the corticospinal tract
59
Of the three motor cortex areas, stimulation of which area requires the least amount of electrical current to elicit a movement
Primary motor cortex
60
What can primary motor cortex neurons encode?
The force of a movement
The direction of a movement
The extent of a movement
The speed of a movement
61
What are 3 forms of pain
Nociceptive
Inflammatory
Pathological
62
What does PAG stand for
Periaqueductal grey
63
what do low threshold mechanoreceptors mediate
touch, vibration, pressure
64
what do high threshold mechanoreceptors (aka mechanical nociceptors) respond to
high intensity mechanical stimuli
65
what do chemical nociceptors (chemoreceptors) respond to
substances in tissue e.g. prostaglandins, bradykinin, serotonin, histamine, K+, H+ and ATP and many others.
play a crucial role in pain
66
alpha fibres
first fast pain.
stabbing
67
c fibres
second slow pain
68
are alpha fibres myelinated or unmyelinated
thinly myelinated
69
are c fibres myelinated or unmyelinated
unmyelinated
70
nociceptive c and Adelta fibres mostly terminate superficially in which laminae?
I and II
also V for Adelta fibres
71
where does perception of light signal occur
cortex
72
direction of signal in the retina
photoreceptors ---> bipolar cells ----> ganglion cells
73
horizontal cells
a type of specialized neuron found in the retina of the eye
receive input from photoreceptors and project to other photoreceptors and bipolar cells
74
direction of light in retina
ganglion cells ---> bipolar cells ---> photoreceptors
75
where does the light signal go after the ganglion cells
makes its way through optic nerve to cortex via lateral geniculate nucleus
76
each photoreceptor has its own receptive field, true or false
true
77
which photoreceptor is more numerous
rods
78
which photoreceptors help you see in dim light
rods
79
a single ganglion cell only receives signal from from rod cell, true or false
false - many rods will send their signal onto a single ganglion cell
80
what happens when a photoreceptor detects light
it stimulates G-protein coupled receptor which activates cGMP
81
what photoreceptor is best. seeing in daylight
cones
82
where are cone cells most numerous
fovea
83
is there more convergence in cone or rod system
rod
(increasing sensitivity, while decreasing acuity)
84
what are the 3 types of cones
short-wave
middle-wave
long-wave
85
which has high visual acuity, rod or cone cells?
cones
86
what does center-surround organisation/lateral inhibition do
serves to emphasise areas of contrast i.e. it sharpens the boundary between objects of different luminance
(when a neuron is activated, it not only sends signals to the brain but also inhibits the activity of neighboring neurons. This inhibition serves to sharpen the contrast between the stimulated neuron and its neighboring neurons)
87
what is the striate cortex
the part of the visual cortex that is involved in processing visual information
88
hearing: a brief overview
1. sound ---> vibration of air
2. vibrate the eardrum, the malleus, the incus, and the stapes
3. the vibration spreads to the cochlea
4. vibration of air is converted to movement/vibration of fluids in the cochlea
5. the vibration in the cochlea is captured by hair cells
6. transduction (physical vibration is transduced to neural energy)
7. perceived in the auditory cortex
89
a) where is reissner's membrane?
b) what does it separate?
a) inside the cochlea, inner ear
b) scala media from scala vestibuli
90
a) where is basilar membrane?
b) what does it separate?
a) inside the cochlea, inner ear
b) scala media from scala tympani
91
where do scala tympani and scala vestibuli connect
helicotrema
92
where does amplification occur in the ear
middle ear (through banging of the stapes, and added force from buckling of the tympanic membrane
93
where are hair cells located
organ of corti in the cochlea
94
what are the 2 types of hair cell
inner and outer
95
which of the scala contain perilymph and which contain endolymph
scala vestibuli - perilymph
scala media - endolymph
scala tympani - perilymph
96
a) inner hair cell function
b) outer hair cell function
a) detect sound and transmit it to brain
b) perception of sound. Amplifer
97
interesting fact about the sodium/potassium levels in endolymph
higher K concentration than normal. K comes into the cell! (normally goes out)
lower Na than normal
98
what do hair cells of the ear sit on
basilar membrane
99
VIII nerve: branches ---> 3 cochlear nuclei:
- Dorsal Cochlear Nucleus (DCN)
- Posteroventral Cochlear Nucleus (PVCN)
- Anteroventral Cochlear Nucleus (AVCN)
100
auditory system super basic pathway
cochlea --> brainstem ---> cortex
101
what does tonotopy mean
The spatial arrangement of where sound is perceived, transmitted, or received.
102
what is the function of the semicircular canals
detect head movements via rotatory acceleration
103
what are the semicircular canals filled with?
endolymph
104
what do the otolith organs do?
sense linear acceleration and gravity
105
what are the two otolith organs
utricle (movement in the horizontal plane)
saccule (movement in the vertical/sagittal plane)
106
what are the 3 major vestibular reflexes?
- vestibulo-ocular
- vestibulo-colic
- vestibular-spinal
107
which vestibular reflex keeps the eyes still in space when the head moves
vestibulo-ocular
108
which vestibular reflex keeps the head still in space or on a level plane when you walk
vestibulo-colic
109
which vestibulo reflex adjusts posture for rapid changes in position
vestibulo-spinal
