Sensor Receptor Physiology Flashcards
Describe an adequate stimulus
It is when each type of receptor is specialised to respond to one type of Stimulus
Name different types of sensory receptors
- photoreceptors
- mechanoreceptors
- thermoreceptors
- osmoreceptors
- chemoreceptors
- nociceptors
What are compound sensations?
It is the perception that arises from the integration of several activated primary sensory inputs
.e.g perceptions of wetness comes from touch, pressure and thermoreceptor input. There is no such thing as a wetness receptor
What do osmoreceptors detect?
They detect stretch due to water volumes - osmotically
What stimulates chemoreceptors?
- oxygen
- pH
- organic molecules .e.g glucose
What stimulates mechanoreceptors?
- pressure (baroreceptors)
- cell stretch (osmoreceptors)
- vibration
- acceleration
- sound
What stimulates photoreceptors?
Photons of light
What stimulates thermoreceptors
Varying degrees of heat
How is receptor information conveyed to the CNS?
Via afferent neurons
Describe transduction
The energy conversion of a sensory stimulus into an action potential
What is the importance for the processing of sensory input by the brain stem?
- cortical arousal
- consciousness (allows us to be aware of the world around us)
What generates a receptor potential?
The stimulation of the receptor will change the membrane permeability by opening ion channels for sodium to move in (electrochemical gradient) and this will depolarise the cell
What is a disadvantage of a receptor potential?
As the potential moves further away from the source the weaker the signal gets
What does the amplitude and variation of a receptor/grade potential depend on?
- The strength and rate of stimulus
- The removal of the stimulus
Why must a receptor potential be converted into a action potential?
So that the transmission can be extended further along the afferent fibre
How is stimulus intensity distinguished?
- by the number of action potentials generated in the afferent neuron
- number of receptors activated within the area (size of the are stimulated)
Complete sentence: the intensity of a stimulus is reflected by….
The magnitude of the receptor potential
Describe the phenomenon - adaptation
Some receptors can get rid of their depolarisation even if there is a sustained stimulus strength
Name two receptors based in their speed of adaptation
- tonic receptors
- physic receptors
What is the trigger zone ?
It is where the receptor potential is integrated
Describe the relationship between frequency of action potentials and stimulus intensity
The frequency of action potentials are proportional to stimulus intensity
True/False : the duration of a series of action potentials is proportional to stimulus duration?
True
Why don’t tonic receptors adapt?
They need to generate action potentials continuously to relay relevant information to the CNS
Name examples of tonic receptors
- muscle stretch receptors that monitor muscle length
- joint proprioceptors that measure stretch within joint
In what situations are phasing receptors important?
When it is important to change the intensity of the stimulus rather relay information that it is switched on
Which receptors are rapidly adapting receptors ?
Physic receptors
What is the “off response” regrading phasic receptors
When a stimulus is removed the receptor will slightly depolarise
Where is the somatosensory cortex?
Post gyrus
When the afferent information reaches the spinal cord, where does it go?
Either to the:
- reflex arc
- up to the brain for further processing
What do labelled lines do?
They stop information from getting muddled until it reaches the somatosensory cortex
What are labelled lines?
They are discrete chains of neurons that convey conscious somatic sensation in a particular sequence. They do this to create more accurate processing of sensory information
Describe the pathway from the afferent neuron to the somatosensory cortex
First order sensory neuron synapses on a second order sensory neuron (in the spinal cord/medulla)
This then synapses with a third sensory neuron (in the thalamus)
This will then reach the somatosensory cortex
What is a receptive field?
It is a region on the skin surface where a somatosensory neuron will respond to a stimulus
What affects somatosensory acuity
> The size of the receptive field
-the smaller the receptive field, the greater the acuity
> lateral inhibition
Can subtle differences in a large receptive field be detected?
No as this decreases somatosensory acuity
Where in the body will you find many receptive fields that are small?
In the fingertips and the lips
What is innervation density?
It is when there is more cortical space allocated for areas with smaller receptive fields
What is lateral inhibition?
It is a mechanism that tries to figure out where the exact receptor field is
What do inhibitory neurons do?
They sit laterally to the receptive field stimulated and block off transmission so that information can be contrasted easily. It helps distinguish between wanted and unwanted information so that the main stimulus can be precisely localised
What areas in the body have the most lateral inhibition and why,
Areas of touch and visions to bring about more accurate localisation
