Sensory receptors Flashcards
Define the terms sensory unit and receptive field Explain the classification of sensory stimuli into modalities Define the terms adequate stimulus and lateral inhibition Explain how sensory information is coded by pacinian corpuscles Explain the difference between phasic and tonic receptors Give examples of cutaneous, visceral and special senses Briefly describe the sensory pathways and the locations of specific sensory areas in the cortex
What are the 5 types of receptors?
Mechanoreceptors (most common) - skin Nociceptors Photoreceptors - eye (retina) Thermoreceptors - heat Chemoreceptors - olfactory (nose) and taste
How can a receptor be stimulated appropriately?
By its own modality (type of sensation)
With sufficient quantity
What is an adequate stimulus?
A stimulation that is sufficient to evoke a reaction (correct modality)
What is a sensory unit?
A sensory unit is a single afferent neuron with all its receptor endings
What is a receptive field?
The receptive field is a portion of sensory space that can elicit neuronal responses when stimulated - overlap
What is lateral inhibition?
Repeated stimulation - the smaller signals are inhibited to the bigger ones can be targeted
What type of receptor is a Pacinian corpuscle?
Mechanoreceptor
Describe the structure of a pacinian corpuscle: (3)
Outer lamellae (detect pressure) Inner fluid filled capsule of membranes Nodes of ranvier along the axon out
What happens when lamellae are deformed?
Na+ influx into the axon across the membrane, causing depolarisation, action potential propagated
Why do we not constantly feel pressure?
Pacinian corpuscles sensitive to CHANGES in pressure not ABSOLUTE pressure therefore we cannot feel constant pressures
How do we phase out constant sounds?
The hair receptors work with the muscle spindle. The muscle spindles constantly react but hair and PCs are blockers and phase out the noise
What are the 3 categories of sensory input?
Cutaneous - external (heat, pain, touch) terminates S1
Visceral - internal (homeostasis) terminates S1
Special senses - vision hearing taste smell
What is S1?
S1 is a primary somatic nervous sense in the somatosensory cortex
Describe the specific pathway: (5)
Chain of 3-5 specific neurones receptors (type 1 or 2) Spinal cord Brainstem Thalamus Cortex area
Describe the non-specific pathway:
APs travel through lots of different channels to alert brain to potential danger
