Sensory Receptors Flashcards
Classification of receptors based on location
A. Extero - Telereceptors - Cutaneous receptors B. Intero - Visceral - Proprio
Classification of receptors based on type of stimulus
Touch receptors Thermoreceptors Chemo Baro Osmo Proprio Noci Photo
Classification of receptors based on adaptability
A. Tonic
- adapt very slowly ex: pain, body position
B. Phasic
- adapt rapidly ex: pressure, touch, smell
Classification of cutaneous receptors
Mechano
Thermo
Noci
Proprio
Types of mechanoreceptors
- Meissener’s corpuscles
- Merkel’s disc
- Krause’s end bulb
- Ruffini’s end organs
- Naked
- Pacinian corpuscles
Meisseners corpuscles
- rapidly adapting
- encapsulated and expanded ends
- A delta fibres
- fingertips, lips, nipples
- low frequency vibrations
Merkels disc
- slow adapting
- unencapsulated
- A beta fibres
- epicritic and discriminative touch
- low frequency vibration
Krause’s end bulb
- spherical
- encapsulated
- rapidly adapting
- A delta
- mucous membranes, skin of genitalia
- discriminative touch, low frequency vibration, stretch
Ruffini’s end organs
- expanded, encapsulated,
- slow adapting
- A beta fibres
- capsule of joints
- crude touch, joint movements, low frequency vibration
Naked nerve endings
- A delta and C fibres
- everywhere on skin
- itch, touch, pain, temperature, tickle
Pacinian corpuscles
- encapsulated
- rapidly adapting
- A beta
- onion like lamellated receptors
- capsule and ligaments of joints
- pressure, joint movements, HIGH frequency vibration
Thermoreceptors
- Cold - A delta; Warm - A ‘C’
- bare nerve endings
- Cold>Warm
- Cold - 5-40 C peak at 25
- Warm - 30-45 C peak at 45
- pain is felt below 5 and above 45 due to stimulation of cold fibres - paradoxical cold fibre discharge
Nociceptors
- bare nerve endings
- C unmyelinated, A delta myelinated
Properties of sensory receptors
- Specificity
- Adequate stimulus
- Doctrine of Specific Nerve Energies
- Law of projection
- Adaptation
- Localization
- Frequency discrimination
- Intensity discrimination (Weber-Fencher Law)
- Relation b/w intensity of stimulus, size of generator potential and freq. of action potentials
Doctrine of Specific Nerve Energies
- Origin of sensation is not important
- Nature of perception defined by path over which sensory info is carried
- When stimulated anywhere along the pathway, same sensation is caused
Law of Projection
A sensory pathway from a given part of body synapses with specific neurons in cerebral cortex which get conditioned to sensory impulses coming from that area
Ex: phantom limb
