Physiology Flashcards
1
Q
What is a dendrite?
A
- receives electrical signals
- passively transfers to the soma
2
Q
Electrical signals pass _____ from the dendrite to the soma?
A
- passively
3
Q
What does the soma contain?
A
- nucleus
- ribosomes
- mitochondria
- endoplasmic reticulu,
4
Q
What is the axon hillock?
A
- site of graded potential
- all or none
- from the soma to axon
5
Q
What are axons?
A
- conduct output signals as action potentials
6
Q
What is a pseudo unipolar neurone?
A
- one neurite the bifrucates
7
Q
What causes the ‘upstroke’ of the action potential?
A
- entry of NA+
8
Q
What causes the downstroke repolarisation of action potentials?
A
- efflux of K+
9
Q
Action potentials have a __varied/constant__ amplitude
A
- constant
10
Q
Why do passive signals diminish as they spread?
A
- cell membrane is leaky
11
Q
What is the length constant?
A
- the longer the length constant the further the local current spread
12
Q
How could you increase passive current spread?
A
- decrease axial resistance (increasing axon diameter)
- increasing membrane resistance (myelin)
13
Q
What is the node of ranvier?
A
- where ion channels are concentrates
14
Q
Explain saltatory conduction
A
- the jumping of action potentials from one node of ranvier to the next
15
Q
Name 3 different types of synapses?
A
- axodendritic
- axosomatic
- axoaxonic
16
Q
Name an excitatory neurotransmitter/_
A
- Glutamate
17
Q
Name an inhibitory neurotransmitter?
A
- GABA
- Glycine
18
Q
What is the effect of the neurotransmitter glutamate
A
- causes post-synaptic cells to become more positive
19
Q
Explain spatial summation
A
- many axon inputs converge
20
Q
Explain temporal summation?
A
- a single axon input
21
Q
Explain ionotropic receptors?
A
- direct gating
- rapid
- membrane depolarisation
- excitatory
22
Q
Explain metabotrophic receptors?
A
- indirect gating
- g-protein coupled
- slower hyperpolarisation
- GABA and glutamate can activate (glycine cannot)
23
Q
Where is glutamate synthesised?
A
- in the brain
24
Q
Ionotropic and metabotropic glutamate receptors discriminate what in the retinal pathways?
A
- On or off
25
Non-NMDA (AMPA) receptors activated by glutamate cause ___fast/slow___ transmissions?
- fast
- Na+ opening
- ionotrophic
26
NMDA receptors activated by glutamate cause ___fast/slow___ transmission?
- slow
| - metabotrophic
27
What is the somatosensory tract responsible for?
- fine touch
- proprioception
- temperature
- pain
- itch
28
How many neurones are involved in the somatosensory pathway?
- 3 neurones
29
Where is the 2nd neurone of the somatosensory pathway?
- dorsal horn
30
Where is the 3rd neurone of the somatosensory pathway??
- thalamus
31
Define modality?
- type of stimulus
32
Define threshold
- intensity of stimulus required for excitation
33
What are the 3 different types of adaptation rates?
- slowly adapting
- fast adapting
- very fast adapting
34
Define receptive field?
- the target territory from which sensory unit can be excited
35
Explain 2 point discrimination
- 2 sharp simultaneous points at different sites
| - subject reports where they are felt
36
What is interesting about the pattern of shingles?
- dermatomal
| - due to infection within the dorsal root ganglion
37
What does grey matter contain?
- cell bodies of neurones
38
What does white matter contain?
- axonal fibre tracks
39
Nociceptors are part of the spiothalamic tract and the fibres decussate _____
- at every spinal layer
40
Proprioception fibres decussate at ____
- the medulla
41
Gracile tract if from what spinal level?
- T6 and below
42
Cuneate tract is from what spinal lever?
- T6 and above
43
DCML fibres travel within what?
- the medial lemniscus
44
Describe lateral inhibition
- when one neurone is activate to a greater amplification it inhibits the activity of neighbouring neurons by inhibitory interneurons
45
What is the function of lateral inhibition?
- sharpens stimulus perception
46
Explain the 3rd order neurons in the trigeminal system?
- relay information to the cortex via thalmocorticlal neurons
47
The somatosensory cortex can be divided into what areas?
- brodmann areas
48
Describe the homunculus?
- scale is by density of sensory innervation
49
How many layers is the somatosensory cortex composed of?
- 6 layers
50
Where do thalamic inputs enter the somatosensory cortex?
- layer 4
| - internal granular layer
51
Describe how the somatosensory cortex is divided?
- 6 layers
| - columns (of body part)
52
describe the posterior parietal cortex?
- combines somatosensory cortex information with visual and auditory areas
53
What cell is important in the transduction of sound?
- hair cells
54
What cation entry enters the cilia?
- potassium
55
What are the tip links of hair cells?
- Gate TMC1 channel dependant on tilt of cilia
56
What is sound?
- repetitive variations in a medium
57
Define sound frequency
- number of cycles
58
Amplitude of sound affects what of hearing?
- loudness
59
Where is sound perceived?
- in the auditory cortex
| - superior temporal gyrus
60
What is the middle ear responsible for?
- sound amplification
61
What is the area ratio of footplate to tympanic membrane?
- 20:1
62
How is sound amplified in the middle ear (3 reasons)
- tympanic membrane area ratio
- lever action of ossicles
- buckling of the ear drum
63
Where does the organ of corti live?
- basilar membrane
64
What fluid fills the scala vestibuli and scala tympani?
- perilymph
65
What fluid fills the scala media?
- endolymph
66
Where does the scala tympani and vestibular connect?
- helicotrema
67
In the cochlea the oval window vibrates onto what first? the scala tympani or vestibuli?
- scala vestibuli
68
Tectorial membrane movement from the basilar membrane causes?
- relative displacement of sterocilia
69
If the sterocilia are tilted towards the kinocilium____
- tip links open
- potassium enters
- depolarisation
70
If the sterocilia are tilted away from kinocilium ____
- tip links close
| - hyperpolarisation
71
When channels are open in the hair cells what way does potassium move?
- moves into the cell!
| - from endolymph
72
Mutations in potassium channels in the ear may cause?
- deafness
73
What determines the distance a frequency travels in the basilar membrane?
- width and flexibility
- high frequency = closer to oval window
- low frequency = closer to helicotrema
74
Define tonotopy?
- spatial arrangement of where sound of different frequency is processed
75
What are the inner hair cells responsible for?
- source of afferent signals to auditory nerve
76
What are the outer hair cells responsible for?
- amplify membrane vibration
77
What motor protein is associated with outer hair cells?
- prestin
78
What drug inactivates prestin?
- furosemide
79
Outer hair cells receive ___convergent/divergent___ signals from ganglion cells?
- divergent
80
Inner hair cells receive ___convergent/divergent___ signals from ganglion cells?
convergent
81
What does the place code refer to?
- location on the basilar membrane
82
What is the medial superior olive for?
- computes sound arrival at the 2 ears
| - places a specific side that the sound comes from
83
What is the lateral superior olive?
- measures the difference in sound intensity between 2 different ears
84
What detects angular acceleration?
- semicircular canals
| - head rotation
85
What detects linear acceleration?
- saccule and utricle
86
What makes up the otolith organs and what is its role?
- saccule and utricle
| - linear acceleration
87
What fills the semicircular canals?
- endolymph
88
What is the crista of the semicircular canals?
- sheet of cells where hair cells are clustered
89
Kinocilium are all oriented in ___different/same___ direction
- same
| - all excited or inhibited together
90
Movement of the head to the left causes endolymph to move to the ___
- right
91
Movement of endolymph towards the right as a result of head movement to the left causes what to the rate of firing?
- movement of sterocillia to the left
- increased firing on the left
- decreased firing on the right
92
What is otoconia?
- found in otolith organs (utricle and saccule)
- crystals of calcium carbonate
- causes sterocillia to bend towards or away from kinocilium
93
What are 3 vestibular reflexes?
- vestibulo-ocular
- vestibulo-colic
- vestibulo-spinal
94
Explain vestibulo-colic
- keeps head still in space when you walk
95
Stereocilia towards the kinocilium _____ the cell and ___increases/decreases___ afferent activity
- depolarises
| - increases
96
Explain a central pattern generator circuit
- alternating rhythmic inhibition and stimulation
- as flexors are stimulated, interneurons inhibit extensors
- non-conscious
97
What are the 3 layers of motor control?
- strategy
- tactics
- execution
98
What is the role of the vestibulospinal tract
- posture and balance
| - originates at the vestibular nuclei
99
What is the role of the rubospinal tract
- flexor muscles
- originates at the red nucleus
- ventral tegmental decussation
100
What is the role of tectospinal tract
- orientating eyes and head towards sound
| - originates superior colliculus
101
What is the role of reticulospinal tract
- muscle tone
- medial (pontine) = ipsilateral = increases tone
- lateral (medullary) = bilateral = reduces tone
102
Where does the reticulospinal tract originate?
- reticular formation
103
What is the somatic motor system
- skeletal muscle and the elements that control them
104
Lower motor neurons receive input from what?
- UMNs
- proprioceptors
- interneurons
105
What are alpha motor neurons important for?
- muscle force
106
What are gamma neurons important for?
- sensory (muscle spindles)
107
Where are the cell bodies of LMNs located?
- in the ventral horn of the spinal cord
108
What composes the spinal nerve
- ventral and dorsal roots
| - mixed nerve
109
Define motor unit?
- a specific alpha Motor neuron and all the skeletal muscle fibres it innervates
110
Define a motor unit pool
- collection of alpha motor neurons that innervate a single muscle
111
How is muscle force graded?
- frequency of action potential discharge
| - recruitment of additional motor units
112
Within the ventral horn where are muscle innervation neurons located?
- Medially
- Laterally
- Dorsally
- Ventrally
```
Medially = proximal muscles
Laterally = distal muscles
Dorsal = Flexor muscles
Ventral = extensor muscles
```
113
2 main types of muscle fibres?
- slow (Type I)
| - Fast (Type IIa and IIx)
114
What colour is slow type I muscle?
- red
| - resistant to fatigue
115
Running a marathon would recruit what muscle fibre type?
- Type IIa
116
Antigravity muscles recruit what muscle fibre?
- Type I
| - Slow-oxidative
117
During use of burst power e.g. weight lifting what muscle fibre is recruited?
- Type Iix
118
What muscle fibre is recruited first and why?
- slow oxidative type I before type IIa and IIx
| - lower threshold = easier activation
119
Describe the myotatic reflex
- when a skeletal muscle is pulled it pulls back
120
Gamma motor neurons innervate ____ fibres
- intrafusal fibres
121
Alpha motor neurons innervate ___ fibres
- extrafusal fibres
122
No reflex seen... what manoeuvre is used for a patella reflex?
- jendrassik manoeuvre
| - pulling clasped hands apart
123
During voluntary movement what fibres are activated?
- intra and extrafusal contract in parallel
| - activated by higher centres
124
Describe the route from photoreceptor to the visual cortex?
- photoreceptor
- bipolar cell
- ganglion cell
- axon
- visual cortex
125
What neurotransmitter is released from bipolar cells?
- glutamate
126
What are the 2 lateral connections in the visual pathway?
- horizontal cells (from photoreceptors to bipolar)
| - amacrine cells (from bipolar to ganglion)
127
Explain the effect of a dark current
- in the dark
- depolarising current
- more glutamate released
128
What is the membranes response to light
- hyper polarisation (less positive)
| - less glutamate released
129
Light converts 11 cis-retinal to ______
- all trans retinal
130
What is the activated form of retinal?
- all trans-retinal
131
Info about Rods____
- seeing in dim light
- high convergence
- most numerous
- increased sensitivity
- decreased acuity
132
Info about cones___
- seeing in normal day light
- low convergence
- highest concentration in fovae
133
What are the different types of cones?
- short wave = blue
- middle wave = green
- long wave = red
134
Centre-surround organisation describes what?
- lateral inhibition
| - maximum APs when the centre and surround are opposite
135
Off pathway in the retina is what receptors?
- AMPA
- Ionotropic receptors
- glutamate = excitatory
136
'On bipolar pathway' in the retina is what receptors?
- MGlutR6
- Metabotropic
- glutamate = inhibitory
137
In the retina metabotropic (on) receptors are __inhibitory/excitator__ to glutamate?
- inhibitory
| - less neurotransmitter
138
What cell in the retina is responsible for lateral inhibition?
- horizontal cells
139
What are the 3 different types of receptive fields?
| Ganglion cells
- m - movement
- p - form and colour
- nonM - nonP - colour
140
On type bipolar cells ___oppose/copy___ the same general hyper polarisation/depolarisation to light as cones?
- Opposite effect to cones
| - light causes depolarisation
141
How many layers are there to the lateral geniculate nucleus?
- 6 layers
142
Axons from the M type of ganglion cells project into what layers of the LGN?
- Layers 1 and 2
- right eye - layer 1
- left eye - layer 2
143
Axons from the P type of ganglion cells project into what layer of LGN?
- Layers 3,4,5,6
- layer 3 - right eye
- layer 4 - left eye
- layer 5 - right eye
- layer 6 - left eye
144
M type ganglion axons reach what final destination in the primary visual cortex?
- Layer 4C alpha
145
P type ganglion cell axons reach what final destination in the primary visual cortex?
- layer 4C beta
146
Non M and Non P type ganglion axons enter what part of LGN and primary visual cortex
- LGN = Koniocellular layers (between layers)
| - blobs within the primary visual cortex (layers 2 and 3)
147
What separates the upper and lower visual field in the primary visual cortex?
- calcarine sulcus
148
What region of the retina takes up the largest proportion of the primary visual cortex?
- fovea
149
Explain cortical receptive fields
- selective for the orientation or direction of motion of a stimulus
- peak frequency depends on able, preferred orientation
150
What is the competition hypothesis in the eye?
- sensory deprivation early in life can alter the structure of the cerebral cortex
- reduced number of branches of axons when eye deprived
151
Name a tract of the descending lateral pathway
- subdivision is the rubrospinal
152
Name some subdivisions of the descending ventromedial (anterior) pathway?
- tectospinal (head and eye movement)
- vestibulospinal (posture and balance)
- reticulospinal (tone)
