PHYSIOL [A] nervous Flashcards
(131 cards)
0
Q
what is the motor homunculus?
A
motor cortex with body plan of muscles mapped into it
1
Q
what is the hierarchical levels in direct motor control in the CNS?
A
cerebral cortex(frontal lobe motor area)
brain stem
spinal cord
2
Q
how do nerves attached to muscles get to the motor cortex?
A
gather in tracts through spinal cord and project to neighbouring neurons in the cortex
3
Q
what 3 main things does the brain stem contribute to motor control?
A
1) integration (visual, vestibular(sense of balance in inner ear) & somatosensory(touch, vibration, pain))
2) maintains flow of excitatory stimuli to spinal cord => posture control
3) vital responses eg. yawning, head movements
4
Q
how does information move up/down spinal cord?
A
within space inside vertebra are columns of neuronal structures(axons) clustered together
carry info up and down through afferent and efferent tracts
5
Q
dorsal side?
A
“back entry” for spinal neurons
information comes INTO this “door” and goes to brain
6
Q
ventral side?
A
“door” for information(signals) going from spinal cord out to body
7
Q
what is the dorsal root ganglion
A
neuronal cell bodies
axons may be in your finger but cell body is located all the way back near dorsal spinal cord
8
Q
what is the spinal cords role in motor control?
A
autonomic & stereotyped reflexes
withdrawal from painful stimuli
alternating activation of flexor and extensor(helps set proper motor pace)
9
Q
where are the cell bodies of sensory neurons located in the PNS?
A
just outside the spinal cord
dorsal root ganglion
10
Q
what is the function of motor neurons?
A
control contraction of skeletal muscle
11
Q
where are the cell bodies of motor neurons located?
A
within spinal cord
12
Q
how do sensory and motor neurons connect?
A
within grey matter of spinal cord via inter-neuron
13
Q
what influences modulation of motor control?
A
cerebellum
basal ganglia
14
Q
so info is processed in motor cortex but then where does it go before becoming final motor command?
A
motor cortex -> basal ganglia & cerebellum -> motor cortex ->
brain stem -> spinal cord
15
Q
role of basal ganglia in modulation of motor control
A
- 80% of total dopamine
- balance muscle tone
- suppress unwanted patterns of movement
- coordinate slow sustained contractions(maintaining posture)
16
Q
what is Parkinson’s disease?
A
- up to 90% of the dopamine containing neurons die
- symptoms include tremor, difficulty in initiating movement, rigid posture
17
Q
which area of the brain is parkinsons mostly associated with?
A
basal ganglia as it contains up to 80% of total dopamine and controls posture/unwanted patterns of movement
18
Q
what could improve the symptoms of parkinsons disease?
A
prescription of L-DOPA which crosses blood-brain barrier and is converted into dopamine in the brain, aiding to better control movements and posture
-> lots of side effects though
19
Q
what is the cerebellum?
A
the weird thing that hangs off the end of the brain heh
10% of total brain volume - its so fat
50% of total neurons - thats why it has so many folds!
20
Q
functions cerebellum?
A
- coordinates motor programs by modulating the output of the higher brain centres
- “experience” drives improvement
ie. motor performance benefits from training eg. elite athletes - intended movements(motor cortex) vs. sensory info(from muscles)
21
Q
so does the cerebellum directly control movement?
A
nope! does not directly control motor nerves..
BUT damage disrupts the coordination/accuracy of movements of limbs and eyes - impairs balance - BUT does not control loss of specific muscle
eg. think of touching your nose diagram
22
Q
brainstorm(lol pun not intended) some symptons of cerebellum impairment:
A
- uncoordinated walk/unsteady
- slurred speech
- difficulty with repeated patterns of movement(“experience” part dodgey)
- errors in judging distance(eyes effected)
23
Q
whats locomotion?
A
the process of movement
the spinal cord controls this, alternating activation of flexor and extensor muscle
24
describe connections between neurons of the PNS and flexor/extensor muscles:
sensory neurons - flexor muscle
| motor neurons - flexor and extensor
25
function of motor neurons in muscle movement?
simply follow orders and cause muscle contraction
26
what is the function sensory neurons in the movement of muscles?
they attach to flexor muscle - provide feedback
- stimulate contraction of a stretched muscle
- can inhibit motor neurons control of flexor muscle
27
what is the overall goal of the cerebellum?
constantly compares INTENDED MOVEMENTS set by motor cortex, with SENSORY INFO received back from joints and muscles
28
so what do the modulatory(basal ganglia, cerebellum) areas of the brain actually do?
The modulatory systems alter the output of the motor pathway in order to adjust the direction and degree of force
29
The control of motor function:
(A) involves the motor cortex, brainstem and spinal cord
(B) involves modulatory areas, which are the cerebellum and basal ganglia
(C) is organised into a pattern known as a somatotopic map (motor homunculus).
(D) answers A and B only
(E ) all of the above (A-C)
E) all
30
Cerebellum:
sensory feedback allows correction for errors between ______and _____ setting the______and _____of movements;
intent and performance
| range and force
31
What are the 4 attributes of sensory stimulus?
1) Modality
2) Intensity
3) Duration
4) Resolution
32
Modality is an attribute of sensory stimulus...um what does it mean?
"type" of sensory stimulus
| eg. eye nerves different to ear nerves
33
Intensity is an attribute of sensory stimulus...um what does it mean?
the "strength" of the stimulus
| eg. brightness of light, how loud a sound is
34
Duration is an attribute of sensory stimulus...um what does it mean?
how long does it persist?
| eg. flashes of light or consistently the same level of light
35
Resolution is an attribute of sensory stimulus...um what does it mean?
position of stimulus
eg. Think of compass experiment! can only feel one point when there's 2!
ability to distinguish between closely spaced stimuli
36
what are the 5 main sensory modalities?
| modes of senses
1. Photoreception: Light
2. Chemoreception: Taste, smell, O 2 and CO 2
3. Mechanoreception: Hearing, vibration, touch, muscle stretch
4. Osmoreception: Solute concentrations
5. Nociception Pain: temperature eg. fast pricking pain, slow burning pain, heat and cold
37
where is sensory info routed through?
all sensory input pathways are routed through the thalamus and project to specialised areas of the cerebral cortex from there
38
how can array of sensory info remain interpretable?
info is mapped
- routed through afferent pathways
- retains spatial organisation
39
where are each of the following systems mapped?
```
somatosensory = parietal cortex - somatosensory homunculus
visual = occipital cortex - retinotopic map
auditory = temporal cortex - tonotopic map
```
40
what actually are nerves?
collected axon tracts, which carry signals from adjacent receptive fields throughout the body
41
how do peripheral nerves enter CNS?
through spinal nerve dorsal roots to spinal cord
| OR directly into brain stem via cranial nerves
42
what are Dermatomes?
body regions for each peripheral spinal nerves
| **think of diagram of spine, different area = different body areas
43
what are the 4 dermatomes?
cranial
thoracic
lumbar
sacral
44
state somatosensory pathway FROM receptor TO cortex:
receptor ending -> dorsal root ganglion -> spinal cord -> medulla -> midbrain -> thalamus -> cortex
45
whats the difference between the pathway for pain and touch from receptor to cortex?
pathways for pain cross midline at spinal cord level
| pathways for touch cross midline at brainstem(medulla) level
46
how do photoreceptors exit the eye?
through the optic nerve, AFTER signals are detected and processed by the retina
47
explain visual map
left field of vision for BOTH individual eyes is mapped in the right occipital cortex
48
layers of retina from outer most to inner most
pigment epithelium
photoreceptors
ganglion cells
optic nerves
49
where is light captured in the eye?
in Rhodopsin in photoreceptors which are at the back of the eye agains the retinal pigment epithelium
50
after photoreceptors capture light and send info to neurons in local network in retinal layer what intergrates all this info?
ganglion cells intergrate the info thats to be sent out of the eye through optic nerve
51
explain the concept of "seeing" light:
dark: cGMP-gated channels are open - steady influx of Na+ ions causing depolarisation and continuous neurotransmitter release
let there be LIGHT(lol): decrease in polarising current => hyperopolarisation => reduced neurotransmitter release - which is interpreted by the nervous system as the perception of light
52
what is the inner ear for?
hearing and balence
53
what area of the inner ear is responsible for sensing sound?
the cochlea(snail thingo) it contains hair cell tuned to specific frequencies vibrated by the basilar membrane
54
what is the name/function of loops coming off the cochlea?
vestibular apparatus
| sense of balance
55
how does info get from inner ear to brain?
cochlea and vestibular apparatus each have ganglion to which they send their info, which is then relayed through axons to the thalamus and then to the auditory cortex
56
what happens to the signal after the basilar membrane vibrates the hair cells in the cochlea?
hair cells have mechanoreceptors that change the vibration into electrical stimulus
57
describe the basilar membrane:
changes in thickness. thinnest at the tip the increases in thickness the further you spiral in
depending where the hair cell sits on the basilar membrane will determine what frequency it picks up.
higher frequency at thinner basilar membrane
58
True or False: Light is detected by closure of cGMP-gated cation channels in the photoreceptors, which results in hyperpolarisation and a decrease in transmitter release.
TRUE!
59
True or False: The cell bodies of somatosensory neurons are located at the site of stimulus detection, for example in the skin surface, and do not use axons to conduct the signals.
False! still need to get info from periphery to central!
60
what is resting potential?
difference in charge inside and outside the membrane, voltage drop
-60mV
61
what are transporters and channels in cell membranes?
proteins!
62
describe layers of membrane
phospholipid bilayer
cholesterols
protein transporters/channels
63
what type of channel spans entire memebrane?
intergral membrane protein
64
describe the phospholipid bilayer part of membrane
two parts:
hydrophobic(repel or fail to mix with water) heads with oily tails
only lipid soluble agents can pass
65
how do polar molecules cross the membrane?
through protein transporters
66
what ions are in high concentrations inside/outside cell
K+ high in
| Na+ and Cl- high out, Ca2+ also slightly higher out
67
what substances can directly flux across membrane?
alcohol, steroids, gases
68
what is simple diffusion?
influx directly related to external substrate concentration(linear)
69
what is facilitated diffusion?
influx is a constant maximum limited capacity of cell to contain substrate
70
what channels are open when membrane is at rest? and which way is the ion transport?
K+ out
| Cl- into
71
explain ions "dual" nature:
ELECTRICAL - interaction of charges with voltage -> membrane potential
CHEMICAL - concentration gradient high to low
72
what does the magnitude of an ionic gradient depend on?
1) concentration
| 2) voltage (membrane potential)
73
why are Cl- and K+ channels open at rest but Ca2+ and Na+ aren't?
as their diving forces are at equilibrium
whereas Ca2+ and Na+ both have very strong inwards driving forces, so pathways are closed and only opened for limited periods of time - very controlled
74
what does open Na+ and Ca2+ channels do?
drive positive changes in membrane that are excitatory
| ...generate excitable signals!
75
what do open K+ and Cl- channels do?
help maintain negative resting level
76
what is membrane potential?
source of potential energy cell uses to do work
77
how does H2O move across membrane?
passive diffusion
78
what drives the passive diffusion of H2O?
osmotic gradient..low salt to high salt content
| "water follows salt"
79
what units measure osmotic pressure?
mm mercury
80
what extra feature allows balance of osmotic pressure?
```
A-
why?
K+ and Cl- channels open
Na+ on outside of membrane cannot pass
A- balances positive cannot pass charge
```
81
functional purpose of K+ channels?
```
Kv = voltage gated, driven by membrane potential
Kir = "leak" channel, active @ rest - maintains resting potential
```
82
functional purpose of Na+ channels?
cause excitatory responses!
open in response to depolarisation
ball on string comes and blocks excitatory response
83
why does the excitatory response of Na+ channels need to be kept brief?
to allow cell to recover
84
functional purpose of Ca2+ channels?
regulates: neurotransmitter release(in synapse), muscle contraction(upon release), secretion of hormones
voltage gated channel
Ca2+ important 2nd messenger, coupling stimuli to responses
85
what type of transport removes leaked ions from inside cell?
active transport via ATP pump
86
what does one pump of ATP get?
1 ATP used pumps
3 Na+ out
2 K+ in
every high energy use
87
how does active ATP pump contribute to membrane potential?
in one ATP pump, 3 Na+ go out and only 2 K+ come in...meaning gain of one net negative charge inside cell
88
what does Ouabain do?
blocks the Na+ pump by competing for the K+ binding site
89
what does Digitalis do?
blocks Na+ pump
| lethal at high doses, but at low doses it is used as a cardiac stimulant
90
how does Na+ work as a co-transporter?
Na+ has strong inward driving force, works as co-transporter by utilising potential energy in Na+ gradient to do work.
91
example of Na+ being a co-transporter?
coupling with glucose and absorbing it across the gut membrane against a concentration gradient
92
how does Na+ work as a counter-transporter?
utilising potential energy of Na+ gradient to move ions against electrical driving force
93
example of Na+ working as counter-transporter:
utilises gradient to export protons(H+) to increase intercellular pH level
export Ca2+ ions after response
94
what is the approx. internal and external ionic concentration of
K+, Na+, Cl- and Ca2+
K+ internal: 150 external: 5
Na+ internal: 15 external: 150
Cl- internal: 15 external: 150
Ca2+ internal: 0.0001 external: 2.5
95
describe(in order) what happens after an excitatory response(Influx of Na+):
influx of Na+ causes positive shift in membrane potential, depolarisation( to around +50)
negative recovery response = repolarisation
Inhibition follows, where membrane potential drops below resting = hyperpolarisation, period in which no new signals can be conducted
96
what equation would you use to calculate the particular voltage needed to balence membrane potential?
Ex = 60 log ([Xo]/[Xi])
where "Ex" is voltage at which chemical and electrical forces are equal and opposite(balenced)
and ([Xo]/[Xi]) is the concentration gradient
97
how does the voltage calculation based on Nernst differ for cation and anions?
```
Ex = 60 log ([Xo]/[Xi]) for cation
Ex = 60 log ([Xi]/[Xo]) for anion
```
98
what does Em stand for?
membrane potential
99
what is the significance of the Nernst equation?
- at any point other than Ex a driving force for net movement of X across membrane will exist (Em - Ex)
- greater the diff. between membrane potential and Ex -> greater the driving force
- however, actual flux required open channels!
100
what 2 factors are required for an ionic gradient to be used to change the membrane potential?
1) driving force
| 2) permeability(open channels)
101
driving force is the difference between _____ and ______:
membrane potential and the equilibrium potential
102
what does an action potential actually do?
amplifies an input signal
| that can be conducted over long distances
103
what is an action potential?
event triggered by THRESHOLD depolarisation
rapid positive change in membrane potential (depolarisation)
rapid recovery (repolarisation)
undershoot(hyperpolarisation)
104
where are action potentials found?
only in specialised cells with excitable membranes
105
what is meant by action potentials have a stereotypic pattern?
voltage waveform
| mexican wave in da cells yo
106
describe ion movement at each stage of action potential conduction:
```
depolarisation = influx of Na or Ca in some tissues(eg. muscles)
repolarisation = efflux of K
hyperpolarisation = too much K ions leave, membrane potential drops below resting
```
107
out of all ions which one sets membrane potential?
Most permeable ion sets membrane potential
108
where are the equilibrium potentials(Ex) set?
at positive and negative limits
Ena = +60
Ek = -90
109
what is the positive feedback loop and how is it limited:
Na channels bring positive change
| are limited by inactivation mechanism of ball on chain
110
what is the downstroke of activation potential determined by?
1) inactivation of Na channels
| 2) activation of Kv channels
111
how does tetrodotoxin affect action potential?
blocks Na channel
SO blocks entire upstroke...meaning there wont be a downstroke..MEANING there wont be an action potential at all, only a small passive response
112
how does tetraethylammonium affect action potential?
it blocks Kv channels (voltage gated)
no effect on Na channels so normal upstoke
BUT not as many Kv channels to restore resting so action potential will be prolonged
113
what are dendrites?
"antennae" off the cell body (or soma) of the neuron
| recieve transmitters from other neurons
114
are all synaptic inputs equal in amplitude?
nope!
further away you are the smaller your input
ie. amplitude of effect decays with distance
115
what happens at soma?
```
integrates info(voltage signals) received in dendrites
summed together, if response is large enough an action potential is initiated at the axon hillock
```
116
where are action potentials initiated?
at the axon hillock of neurons
117
how do action potentials only go one way?
limiting the positive feedback loop: INACTIVATION
| ball on chain blocks Na channel, initiating recovery period where it cannot be excited
118
what is the refractory period?
where inactivation of Na channels have taken place
| no response to stimuli as too few Na channels are avaliable to carry current
119
what is myelin?
living extensions of the glial cells
| it insulates axons to increase conduction distance, speed and efficiency
120
what are oligodendrocytes?
octopuses that myelinate axons in CNS
121
what are Schwann cells?
myelinate axons in PNS
122
where are voltage gated Na channels located along the axon?
they are clustered within the NODES between segments of myelin
123
what is demyelination?
occurs in patients with multiple sclerosis
| the myelin sheath covering axon is destroyed with inflammation and scarring
124
describe what happens in a demyelinated axon after AP is applied:
depolarisation occurs at site of applied AP
| but ions leak from axon due to no myelin, meaning theshold is not reached to conduct next signal in wave
125
function of Astrocytes:
blood brain barrier
126
function of microglia:
play role in defence of brain as phagocytic scavengers
| release nerve growth factor
127
location and function of ependymal cells:
line the internal, fluid filled cavities of the CNS
contribute to formation of cerebrospinal fluid
serve as neural stem cells with potential to form new neurons and glial cells
128
what connects the left and right side of the cerebrum?
corpus callosum
129
what neurotransmitter is released from the vesicles?
Acetylcholine
130
What is the name of the specific type of ligand-gated receptor?
nicotinic acetylcholine receptor (nAChR)
