Lecture 3 Flashcards
WHat is the relationship between stimulus and function?
No perfect “one receptor - one function” relationship!
Receptors can often respond to several different
stimuli but will be most sensitive to a particular type.
Structure of Free Nerve Endings?
Mostly unmyelinated small diameter fibres but also some small diameter myelinated fibres.
• Usually have small swellings at distal ends called sensory terminals which have receptors that function as cation channels allowing depolarization»_space; APs
What stimulates Free nerve endings?
Temperature
Pain
Movement and pressure
Itch (histamines)
Some wrap around hair follicles (peritrichial
endings) acting as light touch receptors that detect bending of hairs
What are Tactile Merkel Discs?
Free Nerve endings located in deeper layer of epidermis.
Associated with large disc shaped epidermal cells
What neurotransmitter allows communication between the tactile epithelial cell and nerve ending?
Serotonin
Where are Tactile Merkel discs found?
Fingertips and very small receptive fields because they are good for two point discrimination and sensitive to an objects physical features.
Where are Tactile corpuscles located?
Papillary layer of dermis, especially in hairless skin.
Structure of Tactile corpuscle?
Spiralling / branching unmyelinated sensory terminals surrounded by modified Schwann cells and then by a thin oval fibrous connective tissue capsule
What does the deformation of a Tactile corpuscle capsule trigger?
Deformation of capsule triggers entry of Na+ ions into nerve terminal»_space; Action Potential
What stimulates Tactile corpuscle?
Delicate, fine or discriminative touch, light pressure and low frequency vibration.
Where are Lamellar corpuscles located?
Scattered deep in dermis and hypodermis
Structure of Lamellar corpuscles?
Single dendrite lying within concentric layers of collagen fibres and specialized fibroblasts. Layers separated by gelatinous interstitial fluid. Dendrite essentially isolated from stimuli other than deep pressure
What does deformation of Lamellar corpuscles capsule trigger?
Deformation of capsule opens pressure sensitive Na+ channels in sensory axon. Inner layers covering axon terminal relax so AP is discontinued.
What stimulates Lamellar corpuscles?
Deep pressure and vibration
Where are Bulbous corpuscles located?
Dermis and subcutaneous tissue.
Also found in Joint capsules.
