lecture 24 - somatic sensation Flashcards
What are the two types of senses?
Somatic and special
What are somatic senses?
Senses detected by generalised receptors found throughout the body
What are special senses?
Senses detected by a special/specific organ or structure
What are the 4 key types of somatic sense receptors?
Mechanoreceptors, nociceptors, thermoreceptors, chemoreceptors
What do mechanoreceptors sense?
Touch, pressure, vibration, proprioception
What do nociceptors sense?
Noxious stimuli (pain)
What do thermoreceptors sense?
Change in temperature
What do chemoreceptors sense?
Chemicals
What senses are considered ‘special senses’?
Vision, hearing, balance, taste, smell
What is signal transduction in terms of somatic sensation?
When sensory receptors are activated, leading to the opening of ion channels and a change in membrane potential causing a receptor potential which will cause an action potential if the threshold is reached.
How are mechanoreceptors stimulated?
By physical forces that distort their plasma membrane, causing mechanically gated ion channels to open.
What are the 3 main types of mechanoreceptors?
Proprioreceptors, baroreceptors, tactile receptors
What is an example of a proprioreceptor?
Muscle spindles
What do baroreceptors detect?
Pressure - e.g. blood pressure
What do tactile receptors sense?
Touch, pressure and vibration
In free nerve endings, what type of stimulus is detected by those with myelinated axons?
Temperature
In free nerve endings, what type of stimulus is detected by those with unmyelinated or thinly myelinated axons?
Pain/noxious stimuli
What are tonic receptors?
Receptors that are continually active (firing APs), with the frequency of APs changing to reflect the intensity of the stimulus.
Are tonic receptors slow or fast adapting?
Slow adapting
What are physic receptors?
Receptors that are normally ‘silent’/inactive, but will respond briefly with APs to changes/stimulus.
What are the 4 types of information encoded in sensory stimuli?
Modality, Intensity, Location & Duration - (MILD acronym)
What is modality in terms of information coding?
The type of receptor activated, and therefore the type of sensation.
What is intensity in terms of information coding?
The stimulus strength, encoded by the frequency of action potential firing and the number of axons activated.
What is duration in terms of information coding?
The time period over which stimulus exists, encoded by the time period over which action potentials are fired in the afferent neuron.
What is location, in terms of information coding?
The place in the body where receptors are activated, which is then mapped in the brain (somatosensory cortex)
When sensory stimulus intensity is weak, what will occur?
Threshold will not be reach, so there will be no response in the afferent neuron.
What are muscle spindles?
Stretch receptors that signal the length and and changes in length of muscles in response to stretch stimulus. They lie parallel to the main muscle and stretch as muscles lengthens and shorten as they contract
