Sensory Receptors Flashcards
What are the four types of sensation classes?
Superficial - touch, pain, temperature and touch discrimation
Deep - muscle and joint position, deep muscle pain and visceral pain
Visceral - autonomic sensation, hunger, nausea as well as visceral pain
Special senses (head only) - smell, vision, hearing, taste
What are cutaneous sensory receptors?
Located at ends of sensory nerve dendrites which detect sensory information from surrounding structures and transduce sensory Infiniti signals the brain can read
Classes of sensory receptors are?
Mechanoreceptors Thermal receptors Pain receptors Chemoreceptors Photoreceptors
What are mechanoreceptors
Detect mechanical compression or stretching of the receptor or tissues adjacent to receptor
Respond to tissue deformation
Includes stretch receptors
tactile receptors
Hair cells of the ear
What are thermal receptors
Detect changes in temperature with some detecting cold and some detecting warmth
They sense peripheral and core temperature
What are pain receptors / nociceptors
May differ in different tissues but all detect pain and itch
Detect damage occur in tissues whether physical or chemical damage
What are chemoreceptors
Detect chemicals in blood (CO2 and H+)
Others detect chemicals in food by olfaction and taste
Detect taste in mouth, smell in nose, oxygen level in arterial blood etc
What are photoreceptors / electromagnetic receptors
Detect light via rods and cones of the retina
What cutaneous receptors are there
Free nerve endings Meissners corpuscle Merkels disk Hair receptors Ruffini endings Pacinian corpuscle (mechanoreceptor)
(All coming from peripheral nerve bundle)
What receptors are found hairless glabrous skin
Thick epidermis
Sweat glands
Meissners corpuscles
Higher receptor density
Pacinian corpuscles
Merkles disks
Free nerve endings
What receptors are found in hairy skin
Thin epidermis Sebaceous glands (hair oil)
Hair follicle receptors
Ruffini endings
Lower receptor density
Pacinian corpuscles
Merkels disks
Free nerve endings
What receptors are found in both hairy and non-hairy skin
Pacinian corpuscles
Merkels disks
Free nerve endings
What are free nerve endings and what do they do?
Free nerve endings detect pain and are polymodal i.e. Can detect hot cold via c fibres and sharp pains via Adelta fibres
Slowly adapting with high activation threshold
There are special type for itch and tickle in superficial layers which contain only c fibres
What are merkles disks and what do they do
Encapsulated nerve endings
Static touch and pressure
Alpha beta fibres
Specialised epithelial cell and nerve fibre
Found with meissners corpuscles and in lips, extremities and genitals
Multiple branches found in Iggo Dome which work with meissners to determine texture
What’s a meissners corpuscle and what does it do
Encapsulate nerve endings which found between dermal papillae
Detects changes in touch and pressure
Alpha beta fibres
Glaborous non hairy skin only
Rapidly adapting with low activation theshold
Found in lips fingers and areas for high level of point discrimination
Good at detecting objects move over skin and low frequency vibration
What are pacinian corpuscles and what do they do
Largest mechanoreceptor (2mm)
Onion like encapsulated nerve endings
Found deep layers of dermis
Detects high frequency vibration
Alpha beta fibres
Glaborous and hairy skin types
Rapidly adapting with low activation threshold
Hands feet nipples
What is a ruffini corpuscle and what does it do
Responds to skin stretch
Deeper layers of skin, tendons and ligaments
Encapsulated nerve endings in all skin types but abundant in hands and fingers as well as soles of feet
What sensation do Meissners corpuscles detect?
Touch
What sensation do merkels disks detect?
Pressure and texture
What sensation do pacinian corpuscles detect?
Vibration
What sensation do ruffini endings detect?
Skin stretch
What sensation do hair follicle receptors detect?
Stroking/ air movement
Muscle and skeletal receptors? What do they do in unison?
Muscle spindles
Golgi tendon organs
Joint receptors
In unison give limb proprioception
What sensation do muscle spindles detect?
Muscle length
What sensation do Golgi tendon organs detect?
Muscle tension
What sensation do joint receptors detect?
Joint angle
What are somatic sensory receptors?
Free nerve endings such as thermal receptors and nociceptors
Examples of thermoreceptors
Cool which detects skin cooling
Warm which detects skin warming
Examples of nociceptors and what they detect
Mechanical
Thermal (hot)
Thermal (cold)
Polymodal (mechanical/thermal/chemical)
All detect pain
What happens when a sensory nerve is stimulated?
It causes AP to travel to CNS
How does CNS tell difference between action potentials from different receptors (as they are all in the same form)?
Modality - where each sensory nerve is recognised by the CNS as being of a particular type
Achieved by CNS reading final destination of nerve fibre - information delivered to point A in the CNS is always of a particular modality
Modal info also delivered to CNS in topographic fashion - pain let delivered to part of CNS which is different to but near stretch or vibration signals from the leg
What is phantom limb sensation?
Arises when sensory neurones from absent limbs are spontaneously active and can be mimicked by electrical stimulation
How does the CNS determine the strength of the signal?
Impulses are of a fixed duration and amplitude therefore the intensity of the signal must be determined by the frequency of impulses - the higher the frequency the more intense the signal is
What is generator potential?
The generator potential initiates impulses in sensory nerves
The bigger the generator potential, the faster the frequency of sensory nerve impulses and so the bigger the intensity of the signal
What is generator potential amplitude dependent upon?
It is dependent upon stimulus strength
Sub- threshold stimulus will not generate AP but strong stimulus will
What are the two types of sensory receptor types and their adaption styles?
Slowly adapting generator potentials which do not adapt rapidly to constant stimuli so no chance in generator potential
Rapidly adapting generator potentials which adapt rapidly to stimuli and less action potentials are fired due to this
What happens when there is a receptor cell which synapses onto sensory neurone
Sensory cells (vision, hearing and taste) produce a receptor potential when stimulated (not a generator potential) which causes receptor cell to release neurotransmitter into synapse and normal neurotransmission takes place
This is a postsynaptic potential rather than a generator potential
What’s the difference between postsynaptic potentials and generator potentials
Generator potentials will last as long as the receptor is stimulated and the amplitude is determined directly by the intensity of the sensory stimulus (not by neurotransmitter conc)
How do different sensory receptors detect different stimuli
Through differential sensitivities
Where one receptor designed to be responsive to one stimulus yet can be highly unresponsive to other types of sensory inputs
What’s a modality of sensation
Modality is the principle types of sensation we CNS feel such as pain, touch, sight etc
Known as the labelled line principle
Link between receptor potential and action potential
When receptor generator potential reaches above threshold action potentials are fired
The more the receptor rises above the threshold the greater the action potential frequency occurs
Slowly adapting receptors sense
Continuous stimulus strength
Rapidly adapting receptors detect
Why are they important
Change in stimulus strength
Predictive function
