Principles of Sensory Physiology Flashcards
What is a stimulus?
A change detectable by the body
What are the 5 modalities, or energy forms, of stimuli?
Heat Light Sound Pressure Chemical
Receptors are found at the _________ end of _______________.
Peripheral end
Afferent Neuron
Receptors convert the energy from a stimulus into _________________. This is called ___________________.
Electrical signals
Sensory Transduction
Stimuli bring about _________ potentials known as ________________ in the receptor.
Graded Potentials
Receptor Potentials
Receptors are specialised to respond to ____ stimulus, the ___________________.
One stimulus
Adequate stimulus
Some receptors can respond weakly to other stimuli, this gives rise to _______________________________.
The same sensation that the receptors adequate stimulus would cause
What are the 6 types of receptors and their adequate stimuli?
Photoreceptor = light Mechanoreceptor = mechanical energy Thermoreceptor = heat and cold Osmoreceptor = changes in osmotic activity Chemoreceptors = specific chemicals Nociceptors = Tissue damage
Receptors can either be:
Specialised endings of afferent neurons
OR
Separate receptor cells closely associated with the peripheral ending of a neuron
Stimulation of a receptor results in a change in ___________________. This usually occurs due to the opening of _______________. which causes an __________ and .’. ______________.
Membrane potential
Na Channels
Influx of Na
Depolarisation
What makes the receptor potential a graded potential?
The stronger the stimulus, the greater the permeability change and .’. the larger the receptor potential.
Because receptor potential have _____ refractory periods, summation in response to rapidly successive stimuli is ________.
No
Possible
How do specialised afferent endings transmit the signal to the afferent neuron?
If depolarised to threshold, voltage gated Na+ channels open and trigger an AP that is conducted along the afferent neuron
How do separate receptor cells transmit the signal to the afferent neuron?
- Receptor potential promotes opening of voltage gated Ca2+ channels
- Ca2+ entry causes exocytosis of neurotransmitters (nts)
- nts diffuse across the synapse and bind to receptors on the afferent
- Na+ channels open = AP
Where are APs initiated in the efferent and interneurons?
Axon Hillock: region at the start of the axon next to the cell body