Peripheral Somatosensory Mechanisms Flashcards
What are the classifications of SS sensations?
- Exteroceptive division
- Interoceptive division
- Proprioceptive division
Receptors of Exteroceptive SS sensations
- Mechanoreceptors [cutaneous touch]
- Thermoreceptors [maintain homeostasis]
- Nocioreceptors [respond to harm]
Receptors of Interoceptive SS sensations
- Mechanorecptors [responds to distension]
- Nocioceptors
- Chemoreceptors
Receptors of Proprioceptive SS sensations
- Proprioceptor
What are the two major functions of the sensory neurons?
- Transduction [encodes stimuli into electrical signals]
- Transmission [propogates electrical signal to CNS]
Describe the charactersitic of sensory receptors
Each receptor is more specific for a single stimuli and has a low threshold for that stimule [adequate stimuli] and a higher or no threshold for other stimuli [inaduaqate stimuli]
What receptor is responsible for light flutters?
Meissner’s corpuscle
What receptor is responsible for sustained touch?
Merkel cell
What receptor is responsible for vibration?
Pacinian corpuscle
What receptor is responsible for skin stretch and sustained pressure?
Ruffini corpuscle
What receptor is responsible for pain, itch, tickle and temperature?
Free nerve endings
How are stimulis transduced into electrical signals?
The stimule changes receptor membrane permeability, allowing some ions to diffuse through channels. This change is called receptor [generator potential]. If the stimuli is strong then the receptor potential reaches AP thresholf and AP is generated
Characteristics of Receptor Potential
Graded
- stronger stimuli→ larger amplitude of receptor potential
- increased amplitude →increased frequcency of AP
- longer stimuli→ longer duration of receptor potential
What is sensory adaption?
- Phasic receptors adapt to constant stimuli [why we can stop paying attention to constant stimuli and only notice when it changes]
- Rapid adaptation is done by phasic receptors [Pacininan’s and Meissener’s corpuscle]
- detects change
- Slow adaption is done by Tonic receptos [Proprioceptors, Nocioceptors, Merkel cells]
- gives continous info about the stimuli
What is the effect of a mutation in Piezo2 gene?
severe deficits in repsonse to touch
What is Piezo2 channel?
non-specific cation permeable channel
Explain the process of sensory transduction in slow adapting mechanoreceptors
Skin deformation [pressure on skin] activates Piezo2 channels in Merkel cell, depolarizing it and allowing voltage-gated CaV channels in the Merkel cell to open and release neurotransmitter continuously.
Binding of the neurotransmitter further depolarizes the neurite, producing sustained firing in the axon.
What are the slow adapting touch and pressure receptors?
- Merkel cell
- Ruffini ending
What are the fast adapting touch and pressure receptors?
- Meissner Corpuscle
- Pacinian Corpuscle
- Hair follicule
What receptor is responsible for flutter and light touch?
Hair follicle
What chemoreceptor signals for thirst?
Osmoreceptors
What chemoreceptors trigger for hunger?
Hypothalamuc chemoreceptors
What neurotransmitter is implicated in itching?
Histamine
What are the different thermorecptors and to which degrees do they respond to?
