Perception and Sensorimotor Control Flashcards
state what it is meant by the key term - perception
perception is the process of obtaining information about the internal/external environment via sensory stimulation
state 3 basic facts to expand upon the definition of perception
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
give 3 additional (different to the basic) facts to help explain what perception actually is
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)
state what it is meant by the key term - Receptors
Receptors absorb energy and convert that energy into a neural signal. They are classified based on the source of the stimulus
state the 5 types of receptors
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
depending on the origin of the signal, the five types of receptors can be classified into what 3 types?
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
what are the two types of sensory adaptation speeds ?
Tonic (slow) or Phasic (fast) adapting receptors
state 4 facts about sensory adaption
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
state what it is meant by the key term - Somatic Receptors
Somatic Receptors are located in the skin or in MSK tissues and process information about stimuli acting on the body surface of deeper structures
what are the three sib-systems that somatic receptors process information about
1) Cutaneous - fine touch, vibration, pressure
2) Proprioception - muscle, tendon, joints
3) Pain - painful stimuli, coarse touch
what are the four types of Somatic Sensory Afferents?
1) T1 / Aa
2) T2 / AB
3) T3 / Ao
4) T4 / C
state the following for T1 somatic sensory afferents:
1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)
1) Proprioception
2) Muscle Spindle
3) Yes
4) 13 - 20 um
5) 80 - 120 m/s
state the following for T2 somatic sensory afferents:
1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)
1) Touch
2) Cutaneous
3) Yes
4) 6 - 12 um
5) 25 - 75 m/s
state the following for T3 somatic sensory afferents:
1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)
1) Pain, Touch
2) Free Nerve Endings
3) Yes
4) 1 - 5 um
5) 5 - 30 m/s
state the following for T4 somatic sensory afferents:
1) function
2) type
3) myelin?
4) diameter (um)
5 conduction speed (m/s)
1) Pain, Touch
2) Free Nerve Endings
3) No
4) 0.2 - 1.5 um
5) 0.5 - 2 m/s
state what it is meant by the key term - Musculotendineous Receptors
Musculotendineous Receptors are mechanoreceptors of five different types, situated in the various soft tissues of the MSK system
what are the 5 types of Musculotendineous Receptors ?
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)
what are Golgi Tendon Organs ? (2 points)
- a bundle of collagen fibres innervated by afferent axons
- axons branch out into the fine spaces in the collage mesh
how do GTO’s work ? (2 points)
- 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
where are GTO’s located, and what is the function of this ?
- 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
are GTO’s fast or slow adapting receptors ?
Slow Adapting Receptors - sensitive to the overall amount of force applied, and not the rate of force application
what are Muscle Spindles?
Muscle Spindles are Stretch Receptors
what is the location of Muscle Spindles, and how does this enable them to do their job?
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
what is the overall structure of Nuclear Bag and Nuclear Chain muscle spindles ? (2 points)
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)
what is the difference between nuclear bag and nuclear chain fibres structure ?
1) Nuclear Bag Fibres (one static, one dynamic) –> have nuclei in the middle
2) Nuclear Chain Fibres –> have nuclei along the whole fibre
what information do Muscle Spindles give?
give information about muscle fibre length and rate of change in length (they do not directly produce force!)
how are Muscle Spindles innervated ?
Muscle Spindles are innervated by the CNS and can control them through gamma motor neurones, type 1a and type 2 afferent axons
explain what type 1a Afferent Neurones are:
1) function
2) how they work
3) how they work
4) origin/location
- 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
explain what type 2 afferent neurones are:
1) function
2) how they work
3) origin/location
- 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
state what it is meant by the key term - Vestibular System
the Vestibular System processes sensory information related to head position, spatial orientation (with respect to gravity), and movement
give 2 basic facts about the vestibular system
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
what 3 things does the Labyrinth consist of?
- 5 sensory neurones
- 3 semilunar canals (approx. 3 mm diameter)
- 2 otolith organs (utricle & saccule)
All elements of the Labyrinth contain a fluid. What is this fluid, and what is its function?
- Endolymph
- when the head moves, it causes nerve receptors in the membraneous labyrinth to signal to the brain about the body’s motion
what are key sensitive elements for the Labyrinth?
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
what is the main part of the vestibular system?
an elaborate set of interconnected chambers called the Labyrinth (continuous and like the cochlea)
where are the Labyrinth located ?
Labyrinth are located deep in temporal bone
how do Labyrinth do their job?
Labyrinth are derived from optic placode of embryo and uses hair cells to transduce physical motion as neural stimuli
what do the utricle & saccule function to do?
what do the semilunar canals function to do?
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
what is between the walls of the Labyrinth?
Perilymph (similar to cerebrospinal fluid)
what is the function of Hair Cells ?
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
how do Hair Cells function ? (3 points)
- 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
what does the ‘Biphasic Nature’ of the hair cells mean?
- 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
where are Hair Cells located, and what are their surroundings ?
- located in Ampulla
- clustered in Crista; protected by gelatinous substance which forms a diaphragm between two different halves of the canal (capula)
explain, using 3 points, how Hair Cells function
- 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)
Explain what events occur when you tilt your head to the left in the canals
- 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
what is the semilunar canal geometry ?
one horizontal, and two at 45 degree inclinations (the head can therefore respond to different rotations)
the capula-endolymph system smooths transduction of angular accelerations into neural signals. This results in what two things?
1) results in a velocity signal at low frequencies
2) results in an acceleration signal at high frequencies
where are Hair Cells located ?
Hair Cells are located in a patch of epithelium called the ‘Macula’
state what it is meant by the key term - Otolith Inertia
Otolith Inertia is the deformation of the otolithic membrane, causing deflection of hairs
state what it is meant by the key term - Otolith
Otolith are calcium carbonate crystals which are fused together and adhere to the top of the gelatinous membrane
where do Hair Cells project from?
there is a gelatinous sheet (falitic membrane) where the hairs project from
Hair Cells have a very complex distribution and orientation. Explain it using 4 points
- 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
what is the function of the Otolith Organs (Utricle & Saccule)?
the Utricle & Saccule detect tilting & translational movements of the head
how do the Otolith Organs detect changes in head position ? (3 points)
- 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
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?
- 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