Physiology Flashcards
1
Q
Function of dendrites Soma (perikaryon) Axon hillock and initial segment Axon Synapse
A
Received input from other neurones and conveys graded electrical signals passively to the soma
Integrated incoming signal that are then conducted passively to the axon hillock
site of initiation of the all or none AP
Conducts output signal as action potentials to other neurones. between soma and presynaptic terminal (anterograde direction) vice versa is retrograde direction
Point of chemical communication between neurones or other cells
2
Q
What do viruses take advantage of in axons
A
retrograde direction is used to infect neurones - herpes, polio, rabies
3
Q
Give examples of unipolar neurones
pseudo unipolar neurone
bipolar
multipolar
A
peripheral autonomic neurone
dorsal root ganglion
retinal bipolar neurone
LMN
4
Q
Input
Integrative
Conductive
Output
A
dendrites
soma
axon
leading to secretion of neurotransmitter
5
Q
Golgi type 1
Type 2
A
long axon
short axon
6
Q
how does an action potential work
A
sodium channels open for sodium influx for the upstroke
potassium channels open up for a potassium outflow for the downstroke
7
Q
normal resting membrane potential
threshold
peak
undershoot
A
-70mV
-60mV
+40mV
-80mV
8
Q
Why does an undershoot take place in AP
A
Some potassium channels remain open for a small period of time
9
Q
What is the problem with passive conduction
A
leaky membrane - passive signals do not spread far from their site of origin due to current loss across the membrane
10
Q
How can passive conduction be improved
A
decreasing axial resistance of the axoplasm by increasing axon dm
increasing membrane resistance by adding an insulating material
11
Q
How does an AP move forward
A
at the peak of the AP outside is negative and the inside is positive - cyclic current which generates an AP -> AP moves forward
12
Q
The difference between larger dm axon and smaller dm axon
A
larger has low resistance so more APs can be produced and vice versa
13
Q
What are the insulating materials in CNS
PNS
A
Oligodendrocytes - one surrounds many axons
Schwann cells - many surround one axon
14
Q
What is saltatory conduction
A
AP jump from one nice of ranvier to the next rather than flowing constantly
15
Q
Give three types of synapses in order of frequency
A
axodendritic - very common
axosomatic - common
axoaxonic - uncommon
16
Q
Describe an excitatory synapse
A
glutamate activates postsynaptic cation selective inotropic glutamate receptors generating a local graded excitatory depolarising response - excitatory postsynaptic potential
17
Q
describe an inhibitory synapse
A
GABA or glycine activates postsynaptic anion selective inotropic GABA or glycine receptors generating a local graded inhibitory hyperpolarizing - inhibitory postsynaptic potential
18
Q
what are the three major amino acid neurotransmitters in the CNS
A
glutamate
GABA
glycine
19
Q
What separates pre and post synaptic membranes
A
synaptic cleft
20
Q
what stores NT within the presynaptic terminal
A
vesicles
21
Q
difference between pre synaptic membrane and post
A
pre - active zones around which vesicles cluster
post- NT receptors
22
Q
what holds the post and pre synaptic membranes together
A
a matrix of fibrous extracellular protein within the cleft
23
Q
What are amino acids and amines released from
What are peptides released from
A
synaptic vesicles
secretary vesicles
24
Q
Give examples of amino acids
A
Glutamate, GABA, glycine
25
gives examples of amines
Each, DA, NA, 5-HT
26
give examples of peptides
CCK, Enk, Neuropeptide Y, somatostatin, TRH, VIP
27
What ion channels fores glutamate, GABA, glycine, ACh and 5-HT activate
inotropic which mediate fast neurotransmission
28
what do all except glycine activate
metabrotropic G protein coupled receptors
| mediate slow neurotransmission
29
exteroceptive sensations
proprioeceptive sensations
visceral sensations
deep sensations
from the surface of the body
concerning posture and movement
from the internal organs
from fascia, muscles and bone
30
the higher the amplitude of the stimulus and the longer the duration means what
more APs fired and more neurotransmitter released
31
```
list the stimulus and physiological receptor for the following
touch, pressure, vibration
proprioception
pain
itch
```
mechanical forces on skin. skin mechanoreceptors
mechanical forces on joins and muscles. joint and muscle mechanoreceptors
heat. thermoreceptors
strong mechanical force on skin, viscera, heat. mechanical, thermal and polydymas nociceptors
irritant. itch receptors
32
list the two types of low threshold units
low threshold mechanoreceptors - mediate touch, vibration, pressure
low threshold thermoreceptors - medical cold, cool, indifferent, warm, hot
33
list the 4 kinds of high threshold units (nociceptors)
high threshold mechanireceptors- high intensity mechanical stimuli
thermal nociceptors - extreme degrees of heat >45 or <10
chemical - substances in tissues
polymodal - respond to at least two of the above
34
Slowly adapting neurones
rapidly adapting
very rapidly adapting
carry on firing APs - stretch receptors
number of impulse proportional to rate of change of stimulus - some muscle spindles, hair follicle afferents
only 1 - vibration - responds to very fast movement
35
A alpha
A beta
A weird one
C
thick myelinated - proprioceptors of skeletal muscle
moderately myelinated - mechanoreceptors of skin
think - pain, temp
none - temp, pain, itch
36
what is receptive field
region that when stimulated with an adequate stimulus causes a response in that neurone
37
list what the skin is innervated with
free nerve endings
meissners corpuscles - esp where 2 point disc is, not in hair skin
merkels - same as meis, but only in hairy skin
hair end organs
krause end bulbs
pacinial corpuscles
38
```
Meissners
merkel
pacinial
ruffini
hair G - guard(long)
hair d - down (short)
c mechanoreceptor
```
```
Ab - stroking, fluttering RA
Ab - pressure, texture SA
Ab - vibration , VRA
Ab - skin stretch - SA
Ab - stroking, fluttering
A weird one - light stroking
C - stroking, social and erotic touch
```
39
What is grey matter divided into
dorsal and ventral horn and 10 laminae of rexed
40
where are these afferent terminals in the dorsal horn
nociceptors A weird one/C
LTMs Ab
Proprioceptros Aa
laminae 1-2
laminae 3-6
laminae 6-9
41
dorsal column first order neurone carries what
| spinothalmic tract carries what
touch, pressure, vibration, conscious proprioception
pain, thermosensation, crude touch, itch, tickle
42
what is the dorsal column divided into and then further divided into
medial fasciculus gracilis (lumbar and sacral)
| lateral fasciculus cuneatus (cervical and thoracic)
43
what are the capabilities of the dorsal column (5)
```
stereogenesis
fine touch
conscious proprioception
vibration detection
weight discrimination
```
44
where is the somatosensory cortex located
in the post central gyrus of the parietal cortex immediately posterior to the central sulcus and adjacent to the posterior parietal cortex
45
list the inputs for brodmans area 1
2
3a
3b
1-cutaneous mechanoreceptors, BA 3b [texture discrimination]joint afferents, golgi tendon organs, deep tissues, BA 3a and 3b [object perception]
2-joint afferents, golgi tendon organs, deep tissues, BA 3a and 3b [object perception]
3a-proprioreceptors [body position]
3b - cutaneous SA and RA, BA 3a [touch]
46
list the layers from the surface to white matter of the somatosensory cortex
```
molecular
external granular
external pyramidal
internal granular
internal pyramidal
multiform
-white matter -
```
47
loss of a receptive field - finger is cut off (e.g. D3)
area formerly representing D3 will respond to stimulation of the adjacent digits - their cortical representation expands into what was D3
48
Na channels open
Ca channels
Cl channels
K channels
```
flows inwards (depolarization, excitatory)
flows inwards (depolarisation, excitatory)
flows inwards (hyperpolariazation, inhibitory)
flows outwards (hyper, inhibitory)
```
49
where does the AP depolarise?
what channels does the depolarisation open?
entry of the substance then triggers what?
where does the NT diffuse and bind?
what does the binding do?
axon terminal
Ca channels
calcium entry triggers exocytosis
synaptic cleft and receptors on the post synaptic cell
initiates a response in the post synaptic cell
50
what are the three ways of inactivating neurotransmitters
NT can be returned to axon terminals for reuse or transported into glial cells
enzymes inactivate them
Nt can diffuse out of the synaptic cleft
51
what are the two modes of action by NT on ion channels
direct by inotropic receptors
| indirect by activation of metabrotropic receptors
52
what are the two major families of ligand gated channels and the difference between the two
GABA, glycine and Ash - pentamers
| Glutamate receptors channels are tetramers
53
what packages are NT released in and how can this affect the outcome of neurotransmission
quanta's - varying quanta may be released
54
difference between spatial summation and temporal
spatially distributed by times together
| EPSPs occur in temporal sequence such that threshold is triggered
55
nociceptive pain
inflammatory pain
pathological pain
acute pain
prolonged
neurogenic (IBS, fibromyalgia)
56
what order neurones are nociceptors
first order neurones
57
two fires in nociceptors
A delta - mechanical/thermal, thinly myelinated, mediate first or fast pain
C fibres - unmyelinated, polymodal, mediate second or slow pain
58
describe the two types of A delta fibres
Type 1 - HTM - strong mechanical stimuli, activated by noxious heat >53, show sensitisation to prolonged stimuli, mediated first pain to mechanical stimuli
Type 2 - mechanical, heat 43-47, sensative to capsaicin. shows adaption. mediated first pain to heat
59
describe the 4 types of C fibres
C-MH - mechanical stimuli and heat 39-51, capsaicin, shows sensitisation to repeated stimuli
C-M - mechanical just
C-H - heat, sensative to capsaicin
C-MiHi-normally insensitive to both but acquires sensitivity following sensitisation by inflammatory mediators. sensitive to capsaicin and other algesic or pro algesic substances
60
difference between central terminal and peripheral in bidirectional nociceptors
central - not responsive to environmental stimuli. Ca dependant transmitter release. targeted by endogenous molecules that regulate activity
peripheral - responsive to environmental stimuli, site of release of molecules that influence local tissue environment. targeted by endogenous molecules that regulate sensitivity
61
where do nociceptive A delta and C fibres terminate
superficially in lamina I and II and also V for A delta
62
what cells receive input form only A beta fibres
proprioceptive
63
peripheral sensitisation
| central
mediated by nociceptors at site of injury
causes primary hyperalgesia
major role in heat and lesser of a role in mechanical sensitivity
reflects an increase in CNS neurones activity and properties
causes secondary hyperalgesia and allodynia
plays a major role in mechanical sensitivity
64
physiological controlling of the gate
| medical
open - C/a delta
closed - A beta fibres active
open - extent of injury, insufficient medication
closed - sufficient medication
65
thermosensation at the skin
| is it uniform over the body
no - hot and cold spots
66
what kind of potential has been implicated in thermosensation
transient receptor potential (TRP)
67
input of LMNs
UPMs
| proprioceptors and internuroens
68
what do LMNs compromise of
alpha MNs - innervate bulk of fibres within muscle that generate force
Gamma MNs - inneverate sensory organ within muscle known as a muscle spindle
69
biceps brachii and brachialis work together how
| what group of muscles are these antagonists to
synergists
| triceps brachii and anconeus
70
where do axons of the LMNs exit
spinal cord in ventral roots or via CNs
71
where are the nerves that innervate distal and proximal musculature
and where are the ones that innervate the axial musculature
mainly in the cervical and lumbar sacral segments of the spinal cord
all levels
72
what does alpha MN and all of the muscle fibres it innervates called
motor unit
73
what is a collection of alpha MNs that all supply a single muscle called
motor neurone pool
74
how is force of muscle contraction graded by alpha MNs
frequency of AP discharge of alpha MN
| recruitment of additional, synergistic, motor units
75
LMNs innervating axial muscles are what to those innervating distal muscle
LMNs innervating flexors are what to those supplying extensors
medial
| dorsal
76
sources of input to alpha MNs
central terminals of dorsal root ganglion cells whose axons innervate the muscle spindles
UMNs in the motor cortex and brain stem
spinal interneurones
77
what does muscle strength depend on
firing of LMNs
number of LMNs that innverate the muscle
co ordination of the movement
fibre size
fibre phenotype
78
what are small motor units innervated by
small alpha MNs and vice versa
79
what if the force of contraction of each motor unit dependant on
the size
80
where is the motor axon innervating a muscle fibre
at endplate (neuromuscular junction) which is usually at the centre of the fibre
81
slow fibres
| fast fibres
slow - aerobic, red, slow contraction, fatigue resistant
fast - type 2A fast contraction, aerobic, fatigue resistant
type 2B - anaerobic, fast contraction but not fatigue resistant, white
82
the three types of motor units
slow - most numerous - lowest threshold
fatigue resistant
fast fatiguing - large and have a high threshold
83
what is the myotonic reflex
when a skeletal muscle is pulled it pulls back
84
how does a myotonic reflex occur
change in length and rate of change is registered by a sensory organ within the muscle - contributes to non conscious proprioception
85
what do muscle spindles consist of
fibrous capture intramural muscle fibres
sensory afferents - innervate intrafusal fibres
gamma MNs - efferents - innervate intrafusal fibres
86
stretch of muscle spindle - what happens next
activation of la afferent - activation alpha MN - contraction of muscle
87
```
supinator - wrist
biceps
triceps
quadriceps
ankle
```
```
C5-C6
C5-C6
C7
L3-L4
S1
```
88
what consists of intrafusal fibres
stimulation from what causes the spindle to contract
non contractile region - innervated by la
contractile - receive efferents from alpha MNs
gamma MNs
89
what happens during voluntary movement in intrafusal fibres
alpha and gamma MNs co activated so intrafusal fibres contract in parallel with the extra fusal fibres
90
where are golgi tendon organs
what do they monitor
what are they innervated by
how do they act to regulate muscle tension
junction of muscle and tendon
changes in muscle tension - in series with extrafusal fibres
lb
protect muscle from over load and regulate muscle tension to an optimal range
91
where do lb enter and synapse under what and where and what do they lead to
spinal cord
synapse under inhibitory interneurone which then synapse on alpha MNs of the homonymous muscle forming the basis of the reverse myotonic reflex
92
what is the polysynaptic pathway
in which an inhibitory internueone is interposed between the lb afferent and alpha MN
93
where are proprioceptive axons
what do they respond to
free nerve endings
golgi type endings
paciniform
ruffini
CT of joints
angle, directions nd velocity of movement in a joint
HT SA, nociceptive function
HT SA protective role
LT SA acceleration detectors
LT SA static position and speed of movements
94
where does proprioceptive information arise form
muscle spindles
golgi tendon organs
joint receptors
95
what do inhibitory interneurones mediate
inverse myotonic response
| reciprocal inhibition between extensor and flexor muscles
