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Physiology Flashcards

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1
Q

What does the somatosensory system mediate?

A 
Fine discriminatory touch
Joint & muscle position sense (proprioception)
Temperature
Pain
Itch
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2
Q

Name the 3 divisions of the somatosensory system.

A

exteroceptive
proprioceptive
enteroceptive

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3
Q

Which division of the somatosensory system registers information from the surface of the body?

A

exteroceptive division

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4
Q

Which somatosensory division monitors postures and movement? Where are its receptors found?

A

proprioceptive

sensors in muscle, tendons and joints

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5
Q

Which division of the somatosensory system reports upon the internal state of the body?

A

enteroceptive division

- closely related to autonomic function

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6
Q

The primary sensory afferent neurone in the somatosensory pathway is normally found in the CNS.
T/F?

A

false - in PNS

cell body in either dorsal root ganglia or cranial ganglia

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7
Q

Where are the cell bodies of 2nd order somatosensory neurones found?

A

dorsal (post) horn of spinal cord or brainstem nuclei

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8
Q

Where are the cell bodies of 3rd order somatosensory neurones found?

A

thalamic nuclei

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9
Q

How is the receptor potential elicited?

A

stimulus (mechanical, thermal. chemical) opens cation-selective channels in peripheral terminal of primary sensory afferent neurone -> depolarising receptor potential

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10
Q

How is the amplitude of the receptor potential related to stimulus intensity?

A

graded and proportional to stimulus intensity

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11
Q

What triggers ‘all or none’ action potentials?

A

a supra-threshold receptor potential

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12
Q

The frequency of ‘all or none’ action potentials produced is proportional to the receptor potential amplitude.
T/F?

A

true

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13
Q

What happens when action potentials arrive at the central terminal?

A

the graded release of neurotransmitter on to the 2nd order neurones

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14
Q

What is the term used to describe how primary afferent neurones are especially tuned to respond to a specific type of energy?

A

the adequate stimulus

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15
Q

Name the 2 different threshold units in sensory receptors.

A

low threshold units

high threshold units

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16
Q

What types of threshold unit responds to fine discriminatory touch?

A

low threshold mechanoreceptors (LTMs)

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17
Q

What kind of threshold unit responds to cold-hot?

A

low threshold thermoreceptors

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18
Q

What is the response by low threshold units to increasing stimuli strength?

A

increased rate of firing of Low threshold mechanoreceptors (LTMs) + perception of increasing intensity

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19
Q

If the stimuli to low threshold mechanoreceptors (LTMs) is of extreme intensity, the qualitative character of the stimulus changes to emphasise the signal.
T/F?

A

False - the qualitative character (e.g. pressure) does not change (e.g. to pain), provided only LTMs are activated.

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20
Q

What type of threshold units are nociceptors?

A

high threshold (HT) units - respond to high (noxious, potentially damaging), nut not (normally) low intensity stimuli

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21
Q

What do thermal nociceptors respond to ?

A

high intensity to extreme degrees of heat (>45 or <10-15 degrees)

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22
Q

What do polymodal nociceptors receptors respond to ?

A

AT LEAST 2 of the HT unit category:
High intensity mechanical stimuli
Extremes of heat
Substances in tissue e.g. inflammatory-like response

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23
Q

What is adaptation?

A

determines whether sensory units change their firing rate in response to a stimulus of changing intensity, or fire continuously throughout a constant stimulus.

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24
Q

Slow adaptation (SA) or tonic/static response is used by which sort of receptors and why?

A

e.g. stretch receptors - continuous information to CNS - provides information about position, degree of stretch or force.

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25
What are the characteristics of a slowly adapting response?
sensory units fire APs continuously throughout a constant stimulus and increase firing rate with increasing stimulus
26
Describe fast adapting responses.
the stimulus strength is detected and the number of impulses is proportional to rate of change of stimulus
27
What is an example of a very fast adapting sensory unit response?
vibration of different intensities e.g. Pacinian corpuscle
28
Which sensory receptors have the fasted conduction velocity?
proprioceptors of skeletal muscle (group A-alpha)
29
Which sensory receptors have the slowest conduction velocity?
group C - temperature, pain, itch
30
What is the receptive field (RF)?
the target territory from which a sensory unit can be excited
31
RF size varies greatly over the body and is inversely related to ....?
innervation density and sensory acuity
32
Areas with high density of innervation will have what size of RF and what type fo acuity?
small RF and high acuity
33
Areas with low density of innervation will have what size of RF and what type fo acuity?
large RF and low acuity
34
Which skin mechanoreceptors respond to touch and are abundant in areas of high 2-point discrimination?
meissner's corpuscles
35
Which skin mechanoreceptors are deep in dermis and joint capsules and respond to deep pressure?
ruffini endings
36
What is an Iggo dome?
multiple Merkel cells grouped together and innervated by a single myelinated fibre
37
Describe Pacinian corpuscles.
unmyelinated ending of sensory nerve cell surrounded by a capsule - response to pressure. Found in dermis and sometimes in fascia
38
What is found at the border of dry skin and mucous membranes?
Krause end bulbs
39
What do two-point thresholds match the diameter of?
the corresponding receptive field
40
Describe the laminae found in grey matter.
10 distinct laminae of Rexed found from dorsal to ventral (I-X) horns
41
In which grey matter laminae are nociceptors found and which fibre class are they?
``` laminae I and II fibre class A-delta/C ```
42
In which grey matter laminae are LTMs found and which fibre class are they?
``` laminae III to VI fibre class A-beta ```
43
in which grey matter laminae are Proprioceptors found and which fibre type are they?
laminae VII to IX | A-alpha fibres
44
Sensory input to which dermatomes travels in the gracile tract (fasciculus gracilis)?
T6 and below (legs and lower trunk)
45
Sensory input to which dermatomes travels in the cuneate tract (fasciculus cuneatus)
input above T6 (arms and upper trunk)
46
describe contrast enhancement.
as information is conveyed from one neurone to the next in a sensory pathway, differences in the activity of adjacent neurones are amplified --> contrast enhancement
47
Describe lateral inhibition.
When one neurone is active, it inhibits activity of its neighbours via inhibitory interneurones & contrast enhancement = lateral inhibition
48
What effect does lateral inhibition have on stimulus perception?
it sharpens stimulus perception
49
What are Brodmann areas? Where does it get input from?
These areas are found and make up the S1 area immediately posterior to the central sulcus BA 1, 2, 3a and 3b input from VP thalamus
50
Which type of input does area Ba 3a receive?
proprioceptors (muscle spindles)
51
Which type of input does area BA 3b receive?
cutaneous - touch (texture, shape, stimulus size)
52
Which type of input does area BA 2 receive?
joint afferents, golgi tendon organs, deep tissues --> pressure & joint position; object perception
53
Which type of input does area BA 1 receive?
cutaneous - texture discrimination
54
A deficit in texture and shape discrimination would indicate a small lesion in which BA region?
3b
55
A loss of texture discrimination would indicate a small lesion in which BA region?
1
56
Impaired grasping and size and shape discrimination would indicate a small lesion in which BA lesion?
2
57
what does astereognosis mean?
impaired size and shape discrimination
58
How many cell layers does the somatosensory cortex have?
``` 6 cell layers (I-VI) 1 - molecular 2 - external granular 3 - external pyramidal 4 - internal granular 5 - internal pyramidal 6 - multiform white matter ```
59
Thalamic inputs to SI terminate mainly on neurones within which layer of the somatosensory cortex?
layer 4 - internal granular
60
neglect syndrome is usually the result of damage to the .... cortex?
right parietal cortex - patients believe the left side of the world does not exist and may even disclaim the existence of the left side of their body.
61
Describe the hierarchy of motor control.
involves at least 3 levels, e.g. high, middle and low. hierarchy from top (forebrain) to bottom (spinal cord). Motor control is initiated by multiple sensory inputs and a need to move using internal mechanisms.
62
What is the function of high level in motor control hierarchy? Which structures are involved?
Function = strategy; | neocortical association areas; Basal ganglia
63
What is the function of the middle level in motor control hierarchy? Which structures are involved?
Function = tactics | Motor cortex, cerebellum
64
What is the function of low level in motor control hierarchy? Which structures are involved?
Function = execution | Brain stem, spinal cord
65
LMNs supply input to UMNs to modulate their activity. | T/F?
False - UMNs supply input to LMNs to modulate their activity.
66
Where do LMNs get input from and what is their role?
input: UMNs, proprioceptors, interneurones | They command muscle contraction and form the 'final common pathway'.
67
What is the role of alpha-motor neurones (a-MNs)?
innervate bulks of fibres within muscle that generate force.
68
What do gamma-MNs do?
innervate sensory organ with muscle aka. muscle spindle
69
Do axons of LMNs exit the spinal cord via dorsal or ventral roots?
ventral roots (or via cranial nerves)
70
Where in the spinal cord would you find a greater number of motor neurones?
cervical enlargement (C3-T1) and lumbar enlargement (L1-3)
71
Describe the distinct distribution of LMN soma in the ventral horn.
LMNs to axial muscles are MEDIAL to those innervating distal muscles. LMNs to flexors are DORSAL to those supplying extensors.
72
Name the 3 sources of input regulating the activity of an alpha-MN.
Central terminals of DRG cells whose axons innervate muscle spindles. UMNs in the motor cortex & brainstem. Spinal interneurones.
73
alpha-MN + all the skeletal muscle fibres it innervates --> ?
motor unit
74
Muscle contraction results from...?
Individual and combined action of motor units which must be co-ordinated.
75
The collection of alpha-MNs that innervate a single muscle = ?
motor neurone pool
76
What are the 2 principle mechanisms which grade the force of muscle contraction by alpha-MN?
Frequency of AP discharge of the a-MN | The recruitment of additional, synergistic, motor units.
77
Activation of muscle fibres depends on ?
The firing rates of the LMNs involved; The number of LMNs that are simultaneously active; The co-ordination of the movement.
78
Fibre size and phenotype are important factors in determining ?
force production by innervated muscle fibres
79
What is the result of a single AP in an alpha-MN?
causes muscle fibre to twitch
80
How do slow twitch and fast twitch skeletal muscle fibres differ?
In how quickly myosin ATPase splits ATP to provide energy for cross bridge cycling. They also express different myosin heavy chains (MHC)
81
Time to develop peak tension is a reflection of...
myosin ATPase activity
82
Describe slow-oxidative (type 1 ) fibres.
ATP from oxidative phosphorylation Slow contraction and relaxation Fatigue resistant
83
Describe type IIa (fast oxidative) fibres.
ATP from oxidative phosphorylation Fast contraction and relaxation Fatigue resistant
84
Describe type IIb (fast glycolytic) fibres.
ATP from glycolysis (anaerobic) | Fast contraction - not fatigue resistant (not much ATP produced)
85
What colour are each type of skeletal muscle fibres?
type 1 and type IIa = red | type IIb = pale
86
Fast fatiguing motor units are connected with which type of muscle fibres?
IIb/IIx | = burst power
87
Fatigue resistant motor units are connected with which type of muscle fibre?
type IIa | = sustained locomotion
88
Slow motor units are connected with which muscle fibre type?
type 1 fibres | = antigravity, sustained movement
89
Describe the Henneman Size Principle.
The susceptibility of an a-MN to discharge action potentials is a function of its size. i.e. slow (& small) motor units are more easily activated - have a lower threshold than larger ones.
90
What does recruitment of alpha motor neurones by size allow for?
the fine and graded development of muscle force - motor units are recruited in order of their size. This type of activation allows for fine control of muscle force across a wide range of tensions developed.
91
What is the myotonic reflex?
when a skeletal muscle is pulled, it pulls back.
92
What does the muscle spindle register?
change in length (& rate of change)
93
What does a muscle spindle consist of?
A fibrous capsule Intrafusal muscle fibres Sensory afferents - innervate the intra-fusal fibres (Ia class) Gamma motor neurone efferents - innervate infra-fugal fibres
94
How can the myotonic reflex be reinforced?
the Jendrassik manoeuvre - ask patient to interlock fingers and try pull hands apart when instructed. tap tendon immediately - the reflex is usually exaggerated.
95
During voluntary movement, alpha and gamma MNs are normally co-activated. T/F?
True - so that the intra-fusal muscle fibres contract in parallel with the extrafusal fibres. Maintains the sensitivity of the spindle to stop it from 'going slack' when the extrafusal fibres contract

Neurology (11 decks)

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