Sensory Systems Flashcards
What are examples of sensory receptors?
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Nociceptors
Proprioceptors
How does the nerve endings of different sensory receptors differ?
May have free nerve endings or complex structures
What are examples of sensory receptors that have free nerve endings?
Nociceptors
Cold receptors
What are examples of complex structures at the end of sensory receptors?
Pacininan corpuscle
Meissner’s corpuscle
What is the specific area that sensory receptors respond to stimulus over called?
Receptive field
How do sensory receptors tranduce their adequate stimulus?
Into depolarisation, the receptor (generator) potential
This evokes firing of action potentials for long distance transmission
Gives information on modality, intensity and location of the stimulus
What does the size of receptor potential encode?
Intensity of stimulus
What does the frequency of action potentials encode?
Intensity of stimulus
What does the receptive field encode?
Location of stimulus
What determines acuity?
Density of innervation and size of receptive fields
What are action potentials from sensory receptors transmitted to the CNS by?
Axons
What are the 3 types of primary afferent fibres that mediated cutaneous sensation?
What are Aß fibres also known as?
Large myelinated
What is the speed of Aß fibres?
30-70m/s
What kinds of sensory information is transmitted by Aß fibres?
Touch, pressure, vibration
What are Aσ fibres also known as?
Small myelinated fibres
What is the speed of Aσ fibres?
5-30m/s
What kind of information is transmitted by Aσ fibres?
Cold, “fast” pain, pressure
What are C fibres also known as?
Unmyelinated fibres
What is the speed of C fibres?
0.5-2m/s
What kind of information is transmitted by C fibres?
Warmth, “slow” pain
What are the 2 types of primary afferent fibres that mediate proprioception?
Aa and Aß (such as muscles spindles, golgi tendon organs etc)
What do proprioceptors give information about?
Position and movement
What do all primary afferent fibre types enter the spinal cord through?
Dorsal root ganglia (or cranial nerve ganglia for the head)
What fibres transmit information from mechanoreceptors?
Aa and Aß fibres
Explain the pathway of mechanoreceptor (Aa and Aß fibres)?
1) Project straight up through ipsilateral dorsal columns
2) Synapse in cuneate and gracile nuclei
3) The 2nd order fibres cross over midline in the brain stem and project to reticular formation, thalamus and cortex