Perception and Sensorimotor Control Flashcards

1
Q

state what it is meant by the key term - perception

A

perception is the process of obtaining information about the internal/external environment via sensory stimulation

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2
Q

state 3 basic facts to expand upon the definition of perception

A

1) can be unconscious or conscious (i.e. - sensation) process
2) relies on specialised nerve cells which convert mechanical, visual, acoustic, or chemical energy into a neural signal
3) brings information into the brain (afferent signals) for controlling, planning, and deciding

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3
Q

give 3 additional (different to the basic) facts to help explain what perception actually is

A

1) often multimodal (integrates multiple senses)
2) can be modulated by the CNS (i.e. - how much a sensor responds to a stimulus)
3) involves motor behaviour (i.e. - move to perceive & perceive to move)

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4
Q

state what it is meant by the key term - Receptors

A

Receptors absorb energy and convert that energy into a neural signal. They are classified based on the source of the stimulus

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5
Q

state the 5 types of receptors

A

1) Photoreceptors - sensitive to light
2) Mechanoreceptors - sensitive to mechanical input
3) Chemoreceptors - sensitive to chemical substances
4) Thermoreceptors - sensitive to thermal energy
5) Nociceptors - can fall into one or more of these categories - sensitive to pain

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6
Q

depending on the origin of the signal, the five types of receptors can be classified into what 3 types?

A

1) Exteroceptors - respond to signals coming from the environment
2) Interoreceptors - respond to stimuli from within the body
3) Proprioceptors - give information about the position of the body elements in space

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7
Q

what are the two types of sensory adaptation speeds ?

A

Tonic (slow) or Phasic (fast) adapting receptors

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8
Q

state 4 facts about sensory adaption

A

1) the stronger the stimulus, the higher the firing rate in the afferent axon
2) response tends to decrease over time if the stimulus remains constant

  • slow adapting: the decline is slow
  • fast adapting: the decline is fast
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9
Q

state what it is meant by the key term - Somatic Receptors

A

Somatic Receptors are located in the skin or in MSK tissues and process information about stimuli acting on the body surface of deeper structures

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10
Q

what are the three sib-systems that somatic receptors process information about

A

1) Cutaneous - fine touch, vibration, pressure
2) Proprioception - muscle, tendon, joints
3) Pain - painful stimuli, coarse touch

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11
Q

what are the four types of Somatic Sensory Afferents?

A

1) T1 / Aa
2) T2 / AB
3) T3 / Ao
4) T4 / C

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12
Q

state the following for T1 somatic sensory afferents:

1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)

A

1) Proprioception
2) Muscle Spindle
3) Yes
4) 13 - 20 um
5) 80 - 120 m/s

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13
Q

state the following for T2 somatic sensory afferents:

1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)

A

1) Touch
2) Cutaneous
3) Yes
4) 6 - 12 um
5) 25 - 75 m/s

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14
Q

state the following for T3 somatic sensory afferents:

1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)

A

1) Pain, Touch
2) Free Nerve Endings
3) Yes
4) 1 - 5 um
5) 5 - 30 m/s

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15
Q

state the following for T4 somatic sensory afferents:

1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)

A

1) Pain, Touch
2) Free Nerve Endings
3) No
4) 0.2 - 1.5 um
5) 0.5 - 2 m/s

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16
Q

state what it is meant by the key term - Musculotendineous Receptors

A

Musculotendineous Receptors are mechanoreceptors of five different types, situated in the various soft tissues of the MSK system

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17
Q

what are the 5 types of Musculotendineous Receptors ?

A

1) Muscle Spindle - in muscles; stretch sensor (amount & speed)
2) GTO - at MT junction; force sensor
3) Golgi, Ruffini, Paciniform - connective tissue of joints (Ruffini, Paciniform) or ligaments (Golgi); similar to cutaneous sensors; position sensory (limit detectors)

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18
Q

what are Golgi Tendon Organs ? (2 points)

A
  • a bundle of collagen fibres innervated by afferent axons

- axons branch out into the fine spaces in the collage mesh

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19
Q

how do GTO’s work ? (2 points)

A
  • when a force is applied, the collagen is stretched which causes depolarisation of the sensory unit causing an action potential
  • in certain ranges of force (typically between 0.5 - 25 N), are proportional to the force applied
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20
Q

where are GTO’s located, and what is the function of this ?

A
  • at the interface between muscle fibres and the tendon
  • NOT within the tendon itself –> makes them sensitive, especially to the force developed by active force contraction and passive stretch of the muscle
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21
Q

are GTO’s fast or slow adapting receptors ?

A

Slow Adapting Receptors - sensitive to the overall amount of force applied, and not the rate of force application

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22
Q

what are Muscle Spindles?

A

Muscle Spindles are Stretch Receptors

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23
Q

what is the location of Muscle Spindles, and how does this enable them to do their job?

A

Muscle Spindles run parallel to the muscle fibre; they have a resting fibre potential which generates a firing rate as the muscle elongates and elongates the spindle with it

24
Q

what is the overall structure of Nuclear Bag and Nuclear Chain muscle spindles ? (2 points)

A

1) vary between 0.1 mm - 1 cm in length

2) a capsule of connective tissue (fusiform in shape) with several inter-connected fibres (3 - 18)

25
Q

what is the difference between nuclear bag and nuclear chain fibres structure ?

A

1) Nuclear Bag Fibres (one static, one dynamic) –> have nuclei in the middle
2) Nuclear Chain Fibres –> have nuclei along the whole fibre

26
Q

what information do Muscle Spindles give?

A

give information about muscle fibre length and rate of change in length (they do not directly produce force!)

27
Q

how are Muscle Spindles innervated ?

A

Muscle Spindles are innervated by the CNS and can control them through gamma motor neurones, type 1a and type 2 afferent axons

28
Q

explain what type 1a Afferent Neurones are:

1) function
2) how they work
3) how they work
4) origin/location

A
  • primarily respond to the rate of change in muscle length
  • when muscle lengthening ceases, the firing rate returns to almost resting rate (fast adaptation - phasic)
  • increases AP’s in a slow stretch, but not as frequent as a fast stretch
  • originates from static nuclear bag fibres, the nuclear chain fibres, but also wraps around the dynamic nuclear bag fibre
29
Q

explain what type 2 afferent neurones are:

1) function
2) how they work
3) origin/location

A
  • APs remain in high frequency for the whole duration of the stimulus
  • slow response - sensitive to the overall length status of the muscle fibre - not the rate of stretch
  • originates from the static nuclear bag fibre and the nuclear chain fibre
30
Q

state what it is meant by the key term - Vestibular System

A

the Vestibular System processes sensory information related to head position, spatial orientation (with respect to gravity), and movement

31
Q

give 2 basic facts about the vestibular system

A

1) “6th Sense” - we are unaware of it

2) key for the control of balance, eye movement, and perception of orientation in the environment while moving

32
Q

what 3 things does the Labyrinth consist of?

A
  • 5 sensory neurones
  • 3 semilunar canals (approx. 3 mm diameter)
  • 2 otolith organs (utricle & saccule)
33
Q

All elements of the Labyrinth contain a fluid. What is this fluid, and what is its function?

A
  • Endolymph
  • when the head moves, it causes nerve receptors in the membraneous labyrinth to signal to the brain about the body’s motion
34
Q

what are key sensitive elements for the Labyrinth?

A

Hair Cells are the key sensitive elements in the structure of the Labyrinth and are located in the Pulis, Canals, and the Auto Leeth Organs

35
Q

what is the main part of the vestibular system?

A

an elaborate set of interconnected chambers called the Labyrinth (continuous and like the cochlea)

36
Q

where are the Labyrinth located ?

A

Labyrinth are located deep in temporal bone

37
Q

how do Labyrinth do their job?

A

Labyrinth are derived from optic placode of embryo and uses hair cells to transduce physical motion as neural stimuli

38
Q

what do the utricle & saccule function to do?

what do the semilunar canals function to do?

A

the Utricle & Saccule specialise in translational movements of the head and static positions relative to the gravitational axis

the Semilunar Canals respond to head rotations

39
Q

what is between the walls of the Labyrinth?

A

Perilymph (similar to cerebrospinal fluid)

40
Q

what is the function of Hair Cells ?

A

Hair Cells function is based on the detection of the ‘Kinocilium’ (longest hair) and the ‘Sterocilia’ (smaller hair)

they transduce minute displacements into receptor potentials –> provides a basis for vestibular function

41
Q

how do Hair Cells function ? (3 points)

A
  • when there is a movement of the Sterocilia towards the Kinocilium, there is a depolarisation of the membrane
  • during the movement of the Kinocilium towards the Sterocilia, there is hyperpolarisation of the cell membrane
  • no response occurs when there are other types of deflection in a perpendicular motion
42
Q

what does the ‘Biphasic Nature’ of the hair cells mean?

A
  • means transduction channels are open in the absence of stimulation –> hair cells tonically release transmitter –> generates spontaneous APs in nerve cells
  • consequence –> firing rates of vestibular fibres can inc^ or dec^ in a manner that mimics the receptor potentials generated by Hair Cells –> mediated by Ca2+ entering through mechanoelectrical transduction and voltage gated ion channels –> allows hair cells to continue to signal small changes in head position, despite much larger tonic forces of gravity
43
Q

where are Hair Cells located, and what are their surroundings ?

A
  • located in Ampulla
  • clustered in Crista; protected by gelatinous substance which forms a diaphragm between two different halves of the canal (capula)
44
Q

explain, using 3 points, how Hair Cells function

A
  • when head moves it causes angular acceleration & canals actually respond to angular accelerations of the head
  • whenever the head is rotated, the canal moves together, and alongside the fluid inertia will generate deformation of the capula which will, in turn, deflect your hairs
  • depending on the direction, this will mean depolarisation (inc^ AP firing rate) or hyperpolarisation (dec^ AP firing rate)
45
Q

Explain what events occur when you tilt your head to the left in the canals

A
  • fluid presses right side of capula
  • therefore, sterocilia move towards kinocilium - inc^ AP rate
  • as continues left, reaches steady velocity, so no more effect of fluid inertia, so firing rate returns to resting value
  • at some point, left movement will have to stop due to mobility & return to static position
  • this causes deceleration
  • therefore, canal walls move clockwise & place pressure on left of capula
  • causes kinocilium to move towards sterocilia & hyperpolarise membrane, dec^ AP firing rate
46
Q

what is the semilunar canal geometry ?

A

one horizontal, and two at 45 degree inclinations (the head can therefore respond to different rotations)

47
Q

the capula-endolymph system smooths transduction of angular accelerations into neural signals. This results in what two things?

A

1) results in a velocity signal at low frequencies

2) results in an acceleration signal at high frequencies

48
Q

where are Hair Cells located ?

A

Hair Cells are located in a patch of epithelium called the ‘Macula’

49
Q

state what it is meant by the key term - Otolith Inertia

A

Otolith Inertia is the deformation of the otolithic membrane, causing deflection of hairs

50
Q

state what it is meant by the key term - Otolith

A

Otolith are calcium carbonate crystals which are fused together and adhere to the top of the gelatinous membrane

51
Q

where do Hair Cells project from?

A

there is a gelatinous sheet (falitic membrane) where the hairs project from

52
Q

Hair Cells have a very complex distribution and orientation. Explain it using 4 points

A
  • curved thread like identification that runs across the Macula - the Striola
  • hairs in Otolith point towards Striola, but in Succula they point away from the Striola
  • so, macula of the striola is about in the sagittal plane when the head is upright
  • the macula of the Otricol is perpendicular to the sagittal plane, and is tilted approx 20 - 30 degrees to the horizontal when the head is in an upright position
53
Q

what is the function of the Otolith Organs (Utricle & Saccule)?

A

the Utricle & Saccule detect tilting & translational movements of the head

54
Q

how do the Otolith Organs detect changes in head position ? (3 points)

A
  • Hair Cells embedded in Otolithic Membrane embedded in Otoconia
  • Otoconia makes otolithic membrane heavier than structures & fluids surrounding it - head tilt = gravity = membrane shifts relative to macula
  • resulting shearing motion displaces hair bundles, generating receptor potential
55
Q

Striola form an axis of mirror symmetry such that hair cells on opposite sides of the Striola have opposing morphological polarisations. What 2 things does this mean?

A
  • head tilt along striola axis excites hair cells on one side whilst inhibiting hair cells on the other side
  • the saccular macula is oriented vertically and the utricular macula horizontally, with continuous variation in the morphological polarisation of the hair cells located in the macula