week5 Flashcards
(254 cards)
1
Q
what are the 4 somatic senses
A
Touch, temperature, proprioception, nociception
2
Q
What is the proprioception
A
Awareness of the position of the body part, relative to each other
3
Q
What is nociception
A
Pain/ itch
detection of body tissue damage/ threat to it
4
Q
What type of cells are somatosensory receptor cells
A
neurons
5
Q
Where are the cell bodies of receptors for somatic sensation below the chin located?
A
Dorsal root ganglia
6
Q
Where are the cell bodies of receptors for somatic sensation above chin (head) located
A
In the brain
7
Q
What is the part of the somatic sensory neurons that transduce touch/ pressure into electrical signals
A
Nerve endings, the tip of the fibres in the skin/ viscera
8
Q
What is “free” nerve endings
A
Found in epidermis
Detect mechanical stimuli, temperature and chemical , related to physcial damage
9
Q
Where is Merkel receptors densely concentrated?
A
Finger tips
10
Q
What is Merkel receptors
(tonic/ phasic) (work with what cell) (what do they detect)
A
Mechanoreceptor nerve endings
Tonic, constant firing AP
Work with Merkel cells, tgt detect fine texture/ steady pressure
11
Q
What are the 2 Encapsulated receptors? What are they
A
Meissner and Pacinian corpuscles
Mechanoreceptors sheathed in connective tissue
12
Q
What is Meissner? (tonic/ phasic) (Where) (detect what)
A
Located in hairless region
Phasic, detect small changes ( light touch/ low freq vibration)
13
Q
What is Pacinian corpuscles? (tonic/ phasic) (Where) (detect what)
A
Deep in skin
Phasic, detect change (high freq vibration, pressure)
14
Q
What is Merkel disks sensitive to
A
Deformation of the skin, good at detecting fine detail and texture
15
Q
What does Merkel disk signal
A
Continuous contact/ pressure, since it’s tonic
16
Q
Is most mechanoreceptor tonic/ phasic
A
Phasic
Detect changes
Depolarize shortly and return to baseline
17
Q
Where is Meissner corpuscles mainly located
A
Top of dermis
Tongue and hairless skin
18
Q
How does Meissner corpuscles detetc shearing
A
It has looping ending inside the corpuscles, which detec sideways shearing
19
Q
Why do we know the “texture” of something better, when we run out hand along the object
A
Corpuscles is phasic, so senses change in shear
20
Q
Is meissner phasic ot tonic
A
Phasic
21
Q
What is the shape of Pacinian corpuscles
A
Onion shape, sheathed in many layers
22
Q
Where is Pacinian corpuscles
A
Deep in the dermis
23
Q
What does Pacinian corpuscles senses
A
Phasic, so respond quickly to strong vibration/ fast changing stimuli
24
Q
Is receptors distribution uniformly distributed
A
No, it is more densely packed in area such as palms, fingertips and lips
25
What is fovea of the somatosensory system
Areas with more densely packed receptors, have higher acuity
26
What is 2 points discrimination
Test for acuity
If skin is touched at 2 spots simultaneously, can you tell if it's 1 or 2 contact points
27
What is thermoreceptors? (what type of nerve endings/ receptors)
Free nerve endings
28
What type of receptors are cold/ warm receptors
Phasic tonic
Can get used to temperature graudally, if temp is constant
29
What happen if out skin is exposed to above 45 degree celsius (what receptor is activated)
Pain receptor is activated, prevent harm from high temp
30
Why we get paradoxical cold ( touching a hot object feel cold briefly)
Cold fibres briefly respond to high tempearture above 45 degree celsius
31
Are there more cold or warm receptors
Cold
32
What type of receptor is Nociceptors
Free nerve ending
33
What is the role of Nociceptors, and what does it respond to
Signal potential harm/ actual damage to body, protect us from danger
Respond to mechanical stimuli, damaging heat/chemical, or chemical released from damaged cells
34
What is somatosensory afferent, what are the 2 groups
Carry sensory signal from sensory system to CNS
Small VS large
35
What are the 2 small fibers
C and A-delta
36
Where does small fibers come from
Free nerve ending
37
What is C fibers (size, myelination, speed of conduction)
Small fibers, unmyelinated, slower conduction
38
What is A-delta fibers (size, myelination, speed of conduction)
Small fibers, thicker than C
myelinated
faster conduction
39
What is the large fiber
A-beta
40
Where does A-beta come from
Merkel disks/ encapsulated mechanoreceptors ( Meissner/ Pacinian corpuscles)
41
What is A-beta fibers (size, myelination, speed of conduction)
Large, myelinated, very fast and precise conduction comparing to small fibre (C and A-delta)
42
How is large fibers projected? (from receptors to brain)
Turn upward on reaching the spinal cord
Run ipsilaterally up the medulla in dorsal columns
In medulla, synapse on cells whose axon cross the midline
43
What is dorsal column
Tract
Back part of spinal cord, between dorsal horns
44
How does small fibres project? (receptor to brain)
Synpases directly/ via interneurons on motorneurons/ dorsal horn neurons, which axons across the midline, run in the spinothalamic tracts
45
What is the tract used for large VS small fibres projection
Large: dorsal column
Small: Spinothalamic tract
46
When does large VS small fibres projection cross the midline
Large: in medulla
small: in spinal cord
47
What does large fibres do? (what info? provide to who?)
Provide feedback(texture/ shape/ etc) to brain motor cortex
Use the info to manipulate objects
This info travel a long way rapidly, so large fibre is heavily myelinated to facilitate conduction
48
What does small fibres do? (what info? provide to who?)
Simple response to specific stimuli, such as pain
Can be handles in spinal cord, no need brain interpertation
49
What is the VPL
Nucleus in the thalamus, where signals from the spinal cord is travel via
50
What is VPM
Nucleus in thalamus, where signal from the head is travelled via
51
Where do VPM and VPL pass
Both pass to S1 (primary somatosensory cortex)
52
What does S1 serve for the contralateral body surface? (area specific)
It is somatotopic, so it is the map of the contralateral body surface
53
Is the area distribution in the cortical space from S1 evenly distributed?
No, it's distorted, so areas of high sensitivity and acuity get a lot of cortical space
54
When you put ur leg into a hotbath, why you only feel the most discomfort at the line by the water surface around you leg?
Due to temperature edge, created by lateral inhibition among somatosensory nuerons
55
What is TRP?
Family of ion channels that a lot of nociceptors have
56
What does TRPV1(vanilloid receptors) respond to
Damaging heat and chemicals, such as capsaicin in chilli
57
What does TRPM8 channels respond to
Cold and methol
58
What is congenital analgesia and why is it fatal
They cannot sense pain, as their nocicieptors are not working
They die from injury/ infection as they are not aware of the pain
59
What are the 2 types of pain, and what fibres carry then
Fast: carry by A-delta (myelinated, rapid)
Slow: carry by C (unmyelinated, slower)
60
Why are both fast and slow pain needed?
Fast: quickly withdrawal from pain source
Slow: prolonged immobilization, helps healing
61
Where do nociceptive signals got sent to?
1: spinal reflex, trigger withdrawal from source of pain
2: to thalamus and limbic system, cause emotional distress/ stress response
62
How is nociceptive cell blocked? Why is it blocked?
Descending pathway originated from brainstem through thalamus block the nociceptive cells in spinal cord, reduce pain signal
Occur in emergency situation when pain needs to be ignored for survival
63
What is referred pain? why does it occur?
Pain in the internal organs are felt on the body surface
As nociceptors from internal organs and skin converge on the same ascending tract, the brain cannot tell where is the pain source
Pain is more common on skin, so brain assume the pain is from the skin
64
How does A-beta activity affect pain? (when rub a sore shoulder, why does it feel better)
In the dorsal horn, C-fibers contact the secondary neuron
Secondary neuron can be inhibited by A-beta via interneurons, so it can block and reduce pain signald
65
What is chemoreception is human? (2 example)
Smelling and taste
66
Where is olfactory receptors located?
Olfactory epithelium, which is at top of nasal cavity
67
Why is the olfactory epithelium pigmented
Unknown reason, but the coloe richness is correlates to the olfactory sensitivity
Darker color= stronger smelling
68
What type of cells is olfactory receptor neurons
Ciliated neurons
69
What is nonmotile cilia
Cilia that branches from the olfactory neurons, which increase surface area for catching odorant molecules
70
What is the specificity of olfactory receptor cell
Each cell has many copies of one type of odorant receptor molcules, so each receptor detect one type of odor only
71
What type of receptor molecules does olfactory receptor cells have
GPCR
72
What is the mechanism of action of olfactory receptor after binding to odorant molecule
1: activate G protein, Golf, increase cAMP
2: cAMP gated cation channel open
3: cation influx, depolarize receptor neurons
4: trigger AP that travel along cell axon to olfactory bulb
73
What does it mean that the olfactory receptor is pinocytotic
it keeps sipping in fluid, and sending the fluid to the brain through nerves
74
What is the life expectancy of olfactory receptor cells
short lived, degenerate and replace by new receptor cells
75
What is cribriform plate
Bone at he base of the cranial cavity
Olfactory receptor cells send their axon into the brain through the tiny holes in the cribriform
76
What is the olfactory bulb
Extension of the cerebrum, process olfactory information
77
What is olfactory nerve/ cranial nerve 1
Projection from the olfactory receptors to the bulb, through the cranial plate
78
What is the convergence of olfactory receptors? Pro and Con?
A lot of convergence occur on the olfactory bulb secondary neurons, after passing the cribriform plate
Enhance sensitivity, sacrifice spatial information, weaker odorants localization
79
Is thalamus involved in olfactory sensory signalling
NO
Olfactory bulb directly project to olfactory cortex (brain), bypassing the thalamus
80
Why does smell calls us emotional memories?
Olfactory bulb projects to the limbic system, which is concerned with motivation and emotion
81
What's amygdala
Part of the limbic system, the fear centre
82
Is our olfaction tonic or phasic
Phasic
Slowly adapt to constant odor, and focus on new odor
83
Why can't we sense our own body odor
Olfactory is phasic, so we adapt to constant odor
84
What is pheromones
chemicals released by animal into environment, which affect psl and behaviors of other members of the same species
85
What is VNO? Does it exist in human
Olfactory structure in nasal cavity, involved in behavioural response to sex pheromones
Does not exist in human, as it disappears during fetal development
86
Where are taste receptor cells located
Clustered in taste buds
87
What type of cell is taste receptor cells
Epithelial cells, not neurons
88
What is taste pore
A smalling opening, allowing the contact of taste buds to oral cavity
89
How many types of receptor cell are in a typical taste bud
5, each detect a flavour
sweet, umami, salty, sour, bitter
90
What does umai receptor cell detect
Glutamate amino acid
91
Why is bitter receptor a protective mechanism
It signal potential toxins, detec poison that's bitter
92
What does salty and sour receptor detect
Na+ and H+, ions
93
What does type 1 receptor cells sense
Salt, Na+ ion
94
What does type 2 receptor cells sense
sweet, umami, bitter
95
What does type 3 receptor cells sense
sour, H+ ion
96
Which taste receptor cell type synapse with sensory neuron? What is the neurotransmitter
Type 3, using serotonin
97
Which taste receptor cell type release ATP
Type 2, act on neurons or type 3
98
What is gustducin
G protein, involved in sweet/ bitter/ umami receptor molecules
It activates signal pathway that increase Ca2+, trigger ATP release
99
When is ion channel used for taste receptors?
For salt and sour (type 1 and type 3)
they are not linked to G protein
100
What is the taste of spicy?
Activating TRP channels vanilloid receptors by capsaicin in cilli, which is also sensitive to heat
101
How does taste signal enter brain
Receptor cells in taste buds excite several nerve fibre
These pathway synapse in medulla and thalamus, and route to the cortex
102
What is cranial nerve 5/ trigeminal
Excite by TRP receptors in the wall of the mouth, for mint/ spicy taste
103
What is in the diencephalon
Pituitary and hypothalamus, which connect brain to endocrine system
104
What control is always involved in hypothalamus
Negative feedback
105
What hormone is made by hypothalamus into anterior pituitary
"releasing hormone", which trigger release of hormone made by pituitary
106
What are the 2 types of output by hypothalamus (what influence can it exert)
Neurally/ hormonally
107
Why is feeding tightly controlled
To maintain energy balance
108
What is arcuate nucleus
In the hypothalamus, first order sensor of hunger/ satiety signals
109
What is the function of NPY Neurons?
Drives hunger
110
What is the function of POMC neurons
Promotes satiety (inhibit eating)
111
What is the function of VMH
Inhibit eating, satiety centre
112
What is the function of LH
Promote feeding, feeding centre
113
What is the inhibitory pathway during fasting state ( How does Arc-NPY inhibit satiety)
1: Arc-NPY signal suppress PVN
2: PVN activate Sympathetic system. Since PVN is inhibited, symp is also inhibited
3: Symp suppress hunger. Since symp is not inhibited, feeding behaviour is promoted (disinhibited)
114
What is PVN
satiety centre that suppress feeding by activating Symp
115
What is the promoting pathway during fasting state ( How does Arc-NPY drive feeding directly)
1: Arc-NPY stimulate LH
2: LH releases orexin
3: Orexin stimulate feeding behaviour and inhibit PVN (further inhibit symp/ satiety)
116
What is orexin?
Neuropeptide hormone
Directly encourage feeding, regulate sleep and appetite
117
What happen to the POMC neurons during postprandial state (what does it do)
Cleave POMC into alpha-MSH, and release them by synpases
118
What does a-MSH do?
Excites: PVN and VMH
Inhibit: DMH
119
What happen to DMH during fed state
DMH can inhibit sympathetic system
But DMH is inhibited during fed state, so sympathetic activity is disinhibited
120
What happen to PVN and VMH during fed state
They are excited, which increase sympathetic activity, inhibit feeding and decrease hunger
121
What is the feedback control of Arc-POMC
Positive feedback control
Arc-POMC excite sympathetic activity, sympathetic activity excite Arc-POMC
Symp is amplified, inhibit feeding further
122
How is Arc-POMC inhibited
By Arc-NPY
They suppress each other depending on the energy balance state of body
123
What is the set point for feeding? (threshold)
Target body weight
124
How does hypothalamus infers body weight?
Based on leptin level
125
What is leptin and what does it tell the body
Protein hormone released by fat cells, more fat= more circulating leptin
126
What does the receptor for leptin do
Located in feeding. anorexigenix centres of hypothalamus, detect circulating leptin level and and infer body fat storage
127
What happen if mutation occur on leptin receptor/ leptin production
Cannot detect leptin level/ receptor thought there's decrease leptin level, cause over feeding and obesity
128
For Arc-NPY, what does leptin excites/ inhibit
Excites: PVN, which increase symp and decrease feeding
Inhibit: Arc-NPY and LH
129
For Arc-POMC, what does leptin excites/ inhibit
Excites: arc-POMC and VMH
Inhibit: DMH. so disinhibit symp, inhibit feeding
130
Does the brain know when to end a meal based on leptin level?
No. leptin is too slow, need faster feedback
131
How does brain know when to end a meal
Based on blood glucose level
Increase blood glucose after eating excites Arc-POMC, and inhibit LH, inhibit further feeding
Based on sensor in the walls of stomach/ intestines, which measure nutrients/ stretch
132
What happen to gut hormones after eating a meal
Sensors in wall of small intestine detect stretch/ nutrients, and release gut hormones
gut hormones promote the whole Arc-POMC pathway
133
What is ghrelin? (from where? When to release/ stop release? what does it do)
Hunger hormone, released by stomach when it's empty
Encourage feeding by directly acting on Arc-NPY and LH, inhibit PVN
Stop releasing when stomach is stretched
134
What's rimbonabant
Drug that block CB1 receptor, decrease appetite
Can cause serious mental problem
135
Why is leptin not useful for treating obesity
Most obese patients are not leptin deficient, but leptin insensitive/ resistant
136
How long is our circadian rhythms cycle
24 hours
137
What does it mean the circadian rhythm is endogenous
It is not just response to changes in environment, but a rhythm that is generated internally, and continue even when environment is constant
138
What cells in our body have internal clock
Almost every cells have its own internal clock
139
How is all the internal clocks in different cells synchronized
By sensory signal acting through the master clock in brain
140
What is PER and per
What is their relationship
per is a gene that show 24 hours cycle, and PER is the protein product
PER repress transcription of per
141
What feedback does PER and per follow
TTFL (transcription translation feedback loop)
they drive each other's cycling
142
When is per and PER most abundant
per: transcribed mostly early in the night , mRNA most abundant at (10pm)
PER: Most abundant 6 hours after the transcription peak, ~4am
143
What happen if PER is absent
per mRNA level does not cycle
144
What is tim and TIM
tim= mRNA
TIM= protein product
oscillate similarly to per and PER
145
What does TIM do
bind to PER, form TIM/PER protein dimer complex, repressing transcription of per and tim
146
What happen if either PER or TIM is absent
Neither tim or per cycle oscillates, they are interdependence to maintain circadian
147
What is the self repression driven cycle of tim/ per and TIM/PER
per/tim mRNA increase, producing TIM/PER
at 4am, high level of TIM/PER repress tim/per and shut them off
TIM/PER level gradually fall, and tim/per is no longer repressed at 10pm, rise to peak transcription level again, and lead to another peak of TIM/PER
Each cycle takes 24 hours
148
What is CLK and CYC
They form protein dimer that binds to the DNA promoter region and promote per/ tim transcription
149
What is the mechanism of action of how TIM/PER block tim/per transcription
At, TIM/PER dimer translocate into nucleus, block CLK/CYC positive transcription factor, so per/tim transcription is repressed
150
What is DBT
Translation is quick, so PER and TIM could be generated much rapidly, making the circadian cycle shorter than 24 hours
DBT bind to PER, causing it breakdown
This slow down the rise of PER level, so they won't peak until 6 hours after, lengthens the circadian cycle to 24 hours
151
What is the human "PER/TIM"
PER/CRY
152
What is the human CLK/CYC
CLK/bmal1
153
What is the human dbt
ck1e
154
What are the key components in human circadian cycle (TIM/PER, CLK/CYC, DBT in fly, what about human)
PER/CRY block per/cry
CLK/bmal1 promote per/cry transcription
CK1e slow down circadian cycle to 24 hours
155
What is zeitgeber
"time giver"
External factors that keep the cellular clock in sync
156
What is the main zeitgeber in human
Light
157
What is melanopsin retinal ganglion cells
Sense light and project to the master clock SCN, keep internal clock in sync
158
What is SCN
the timer keeper
master clock that control body clocks
located in hypothalamus
159
What does retinal signal do to the SCN cells
they cause chemical changes in these SCN, causing to breakdown of PER/CRY
160
What happen if PER/CRY level drop when PER/CRY is already falling? What about if it occur when the level is rising
If already falling: set the clock forward (faster, running ahead)
If rising: set the clock back (slower)
161
What is "entrainment"
Nudging a clock into synchrony with another rhythm, "trainning" the clock
SCN is entrained to day/night rhythm, other clocks are entrained to SCN
162
What happen to pineal body at night (in the dark)
SCN neurons project to pineal body, leading it to release melatonin
163
What does melatonin do to reset the master clock
Act via melatonin receptor in the SCN, reset the master clock to night time, help regulate/ synchronize circadian rhythm, prepare body for sleep/ night function
164
Where is pineal found
diencephalon
165
What is diurnal VS nocturnal
Diurnal: sleep at night
Nocturnal: sleep at day, up at night
166
What happen to the LH during day light
SCN indirectly excites neuron in it so it release orexin, causing arousal
167
What happen when u lost orexin (in term of sleep)
Narcolepsy, suddenly fall asleep
168
What happen to LH during darkness
Other cells is active, which release neuropeptide melanin-concentrating hormone, induce sleep
169
What do orexin neuron and MCH neuron do to each other
Antagonistic, inhibit each other
170
How does ATP relate to sleeping
Breakdown of ATP causes a build up of adenosine, which cause sleepiness
171
How does caffeine keep us awake? What is a caffeine crash
Caffeine block adenosine receptor, but adenosine level remains high
When caffeine wear off, it cause "crash"
172
What is REM sleep
rapid eye movement sleep
Dream and eyes move, muscle tone vanishes
173
Why does aquatic animal lack REM sleep
During rem sleep, muscle tone vanished, which makes them unable to swim and drown
174
What is non-rem sleep
Dreamless sleep, has 3 stage
stage 3 is deep NREM sleep
175
What happen to our muscle during REM sleep
Paralyzed, lost muscle tone
So we don't move during our dream
176
What is simple reflex
SImplest form of motor control
Sensory neurons synapses with spinal cord motorneurons to mediate simple reflexes
177
What is the pathway for simple reflex
1: Sensory stimulus detect by sensory receptor
2: Carried into CNS by sesnory afferents
3: Process in C nervous system
4: AP in efferent neurons, produce a motor response
178
What is in charge for somatic response (perform the response)
Skeletal muscle
179
What is a monosynaptic reflex
Has a single synapse between the afferent and efferent neurons (on motor neurons)
180
What is a polysynaptic reflex
Has 2/ more synapses, involving a interneuron (afferent to interneuron, to motor neuron)
Both synapses in the CNS
181
Is stretch reflex conscious or unconscious
Unconscious
182
What is the stimulus for stretch reflex
Passive stretch of a muscle by applied load/ contraction of antagonist muscle
Stimulus is external from outside
183
What is the response of stretch reflex
Active contraction of muscle
184
What type of connect does stretch reflex uses to connect motor neurons
Monosynaptic connection, direct connection with motor neurons
185
What is the sensitivity and speed of stretch reflex
Very sensitive, very fast
186
Where is stretch reflex the strongest
In postural muscle, maintain psoture against gravity
187
What happen to stretch reflex during movement
It is suppressed, allowing us to move
188
How can we suppress all the spinal reflexes
All spinal reflexes can be inhibited by efferent signal from the brain to spinal cord
189
What is GT reflexes (golgi tendon) connection
Polysynaptic pathway, GTO afferents synapses on interneurons in intermediate zone of spinal cord
190
What does interneurons do to other motorneurons of the same muscle
It inhibits them
191
What is the stimulus for GT reflex
Active tension/ contraction in muscle
Over exertion of muscle
192
What is the response of GT reflex
Relaxation/ reduction of tension, through negative feedback
193
What is the relationship between GT and stretch reflex
GT regulate the level of stretch, complementary and inhibitory to stretch reflex
194
What is the pathway of GT reflex
Over contraction--> activate GTO--> activate interneuron
Interneurons activate motoneuron and reduce contraction, regulate amount of force-->muscle relax
195
When is GT reflex suppressed
When net motion is favoured
196
What happen when there's over activation of bicep
1: GTR activated, relax bicep, reduce bicep activity
2:Antagonistic muscle (tricep) is stretched through stretch reflex
197
What is flexion withdrawal reflex
Conscious, withdrawing urself from harm
198
What is the stimulus for flexion withdrawal reflex
Noxious injury of limb, activating pain receptor
199
What is the response of flexion withdrawal reflexes
Flexion of joint proximal to stimulus, withdrawing limb away from stimulus
Extension of the distal joint, get rid of what you are holding
200
What is the speed of flexion withdrawal reflex
Much slower conduction afferent comparing to GTR or stretch reflex
201
What is the connection of flexion withdrawal reflexes
Multi-synaptic path to motorneuron
202
What is reciprocal inhibition
Activation of one motor nucleus is coupled to inhibition of antagonistic motor nucleus
ie, tricep and bicep can't be activated at the same time
203
What happen to reciprocal inhibition, when a co-contraction of antagonists is desired
A different set of interneurons is used, which suppress default reciprocal inhibition
204
What is patellar tendon reflex
A reciprocal inhibition
When the patellar tendon is tapped, one muscle is stretched (quad), and the antagonist muscle is inhibited from contraction (hemistring)
knee jerk reflex
205
What is cross extension reflex
When step on something sharp, the leg where there's pain is flexed, and the opposing leg is extended
206
Why is there contralateral extension in cross extension reflex
To maintain/ increase postural support
207
What does commissural interneuron do in cross extension reflex
Carry signal to contralateral spinal cord, across the other side, activate opposite side interneurons, cause extension of opposite leg
208
What is the stimulus for extensor thrust reflex
Pressure on sole of foot (bottom of foot)
209
What is the response of extensor thrust reflex
Activation of leg extensors, push body against gravity and stand up
210
When does extensor thrust reflex operate
Only during stance
211
What is the pathway of extensor thrust reflex
Mechanoreceptor in foot project to intermediate zone interneurons, then project to motorneurons
212
What does corticospinal tract do?
Influence extensor thrust reflex
213
What is Babinski sign
If corticospinal tract is damaged, the reflexion pattern is switched from extensor thrust pattern to flexion withdrawal
214
What is the main purpose of vestibulo-spinal reflex
Stabilize body for balance/ spatial orientation
215
What is the stimulus for vestibulo-spinal reflex
Tilting head to one side, activating the otolith afferents
216
What is the response of vestibulo-spinal reflex
Downhill limb (leg) extension
217
Is vestibulo-spinal reflex contralateral or ipsilateral
Ipsilateral, it extend leg on the same side of head tilting
218
Pathway of vestibulo-spinal reflex, if head is tilted right
1: activate otolith on the right
2: activate vestibulo spinal tract on the right
3: activate right side motor nuceli
4: right leg extended
219
What is CPGs
Netwrok of interneurons in the spinal cord and brainstem coordinate the interaction of many different motor group
220
What is CPG responsible for
More complex posture/ movement programmed by CPGs
221
Where is CPG located primarily
spinal cord and brainstem, also hypothalamus
222
What is the order of CPGs activation?
In order or relevance, one by one, one after one
223
What is CPGs important for
locomotion and motor control, as well as behavioural responses
224
What program the step cycle during walking
CPG, network of of neurons within the intermediate zone of the lumbar cord (spinal cord)
225
What are the two stage of leg step cycle
Swing and stance
226
What is the rhythm of walk cycle
Autorhymic, autonomic cycle once you start walking
227
How many sets of CPG are there for walk cycle
2 sets
One for flexion (swing), one for extension (stance)
228
What control the 2 sets of CPG during walking (on and off)
Reciprocal inhibition
One CPG is on, the other is off
Inhibit one another mutually
229
What are the 2 half centres of CPG for walking
1: flexor burst generator, drive flexor motor nuclei
2: extensor burst generator, drive leg extension
230
What happen when there's no inhibition on the half centres for walking
Both are spontaneously active, both swing and stance at the same time, no net movement
231
how is human walking in term of metabolic energy
Relatively economical
232
Why running use more metabolic energy then walking
They use different set of CPGs
233
What is the pacemaker for walking (which generator)
Flexor burst generator
234
Where is flexor burst generator located
Intermediate zone, the interneurons
235
What is the pathway for flexor burst generator to leg swing
1: activation of flexor burst generator
2: activate flexor MN, fire AP
3: leg flexion and swing
236
What is the pathway for extensor burst generator to leg extension
1: activation of extensor burst generator
2: activate extensor MN, fire AP
3: leg extension, stance
237
What is the duration of flexion phase of swing, in different speed of locomotion
The duration is fixed, so it is constant regardless of speed of locomotion
238
What differentiate walking and running
Walking: both feet on the ground
running: both feet off the ground
239
How does flexor burst network stop activating MN
It has a build-up of inhibition, which eventually stops the burst of AP, end activation of flexor MN
240
What happen when flexor burst network is turned off
The reciprocal inhibition of extensor burst network ceases, so extensor network is now active
241
What is the sensory feedback of walking? In which phase does it take place
Stance phase
cutaneous and proprioceptive info is feedback to the system, adjusting next step, so we can walking properly
242
What is the duration of stance phase
Variable, depending on speed of walking
243
What makes you walk faster VS slower (what adjust speed of walking)
Stance phase
Shorter standing time= faster walking
244
What happen at heel strike
Heel strike= between swing and stance
As heel strike, mechanoreceptors will feed sensory information from foot to sensory feedback, adjusting step before new swing phase
245
What are the 3 phase dependent reflexes
Stretch reflex, Golgi tendon reflex, extensor thrust reflex
246
Why is sensory control essential for walking
CPG does not know condition of the ground, as each step is different
Sensory control inform CPG when it's safe for new swing phase
247
What does crossed projection do for walking
Provide correct phase-linking of CPGs on each side, right and left leg coordination, ensuring opposite phase occur on opposite leg
248
What does CPGs in cervical cord program for?
The motion of arm swings during walking
249
What does the flexion phase of arm synchronous with
Contra-lateral flexion in leg
one leg flex, opposite side arm is flex
250
What does propriospinal tract do
Phase linking the arm and leg CPGs
251
What does postural CPGs in reticular formation do
Coordinate upper body motion with spinal step cycle, balance postural stability during walking
252
What is the head angle when body is moving during walking
Head angle is maintained constant, done by combinations of reflexes
253
What does reticular formation of pons and medulla do
unconscious maintenance of centre of gravity when walking/ standing
254
What are 3 sensory sources essential for postural maintenance
1: somatosensory (proprioceptive)
2: vestibular (ear)
3: visual
