sensory transduction, pain and local anaesthesia Flashcards
name the process to detect environmental stimuli
sensory transduction
dysfunction and pain can arise through [6]
spinal injuries
neuronal damage
genetic disorders (e.g. congental anaesthesia)
inflammation
cancer (primary symptom in palliative care)
adverse effects of drugs
name the 6 sensory systems
1) Visual (sight)
2) Auditory (hearing)
3) Vestibular (balance)
4) Olfactory (smell)
5) Gustatory (taste)
6) Somatosensory (touch, heat, pain)
compare how sight/sound/balance are detected compared to taste/touch/pain
sight/sound/balance have specialised cells as receptors ; they use a neurotransmitter to send an impulse down a afferent neuron
taste/touch/pain have modified nerve terminals as receptors ; impulse sent down sensory afferent neuron
some sensations are due to
several receptors working together
function of pacinian corpuscle
vibration and rapid movement
describe the process of sensory transduction
receptor potential = local circuit current flow = depolarisation of 1st node = exceeds AP threshold = AP initiation = propagation
How much pressure is
needed to result in generation of
an action potential?
(this is called encoding)
receptor generator potential > threshold
what is sensitivity ?
ability to encode and detect a wide range of stimuli strength
propagated information is encoded by AP frequency not their amplitude
how is sensitivity increase (i.e how do we detect weak stimuli)?
variety of neurones with different AP thresholds used
population encoding (large number of neurone)
how do we detect strong stimuli ?
via adaptation
when there is little adaptation ; summation of membrane potentials needed to produce a receptor potential
when there is fast adaptation, a single membrane potential can result in a receptor potential
sensitivity is gained through …
adaptation
what are noxious stimuli ?
stimuli above normal range so capable of causing damage
describe the 2 types of specialised pain nerve fibres
myelinated (a delta fibres) - detect fast, sharp pricking acute pain
mainly mechanical pain
unmyelinated ( or C fibres) - detect slow,dull ache ; they are polymodal so mechanical and thermal
how do local anaesthetics work
what is the region of the pain block
block nervous conduction at the level of the AP
specific order of block:
unmyelinated > small myelinated > large myelinated
region of block limited to nerve trunk
