Week 5 (Touch, Pain and Temperature) Flashcards
What are the mechanical senses?
-Vestibular sensation
-Somatosensation
What is vestibuation
Vestibular system made up of receptors in inner ear that respond to body position & movement/tilt of the head
This information is used alongside our other senses in order to perceive what is happening
It also aids balance, which is why inner ear infections result in dizziness and loss of balance.
What does the vestibular system consist of?
The semicircular canals
The Otolith organ
The Semicircular canals
-3 canals filled with fluid (endolymph) with hair cells in it
-Movement causes endolymph to move against hair, bending the hair*
-Oriented on 3 planes – comparative stimulation gives brain information about movement of head
The Otolith organ
-These sends messages about our position in 3D space
-They are sensitive to acceleration, deceleration, & direction changes
-Comprise Utricle and Saccule – different orientations
similar to the endolymph but they are glutinous
What are the key aspects of somatosensation?
-Hapsis (fine touch, pressure)
-Kinesthesis, vestibular (movement, position & spatial orientation/ balance)
-Proprioception (awareness of our body in space)
-Temperature
-Pain
What are stimulus inside and outside of the body called?
Inside: Interoceptors and Proprioceptors
Outside: Exteroceptors
What are the two types of skin?
Hairy and glabrous (hairless)
What is hapsis a fancy word for, (or haptic/ tactile receptors)
The sensation of pressure
What are the different layers of skin called?
Epidermis, Dermis & Subcutaneous tissue.
The Epidermis
Top layer, contains cells that produce pigment and protect immune system.
The Dermis
Contains much of our nerve endings, oil and sweat glands, and hair follicles.
Subcutaneous tissue
Fat, connective tissue, blood vessels
Hair receptors
Dendrite attached to hair on your skin
-As an object moves across the skin, these hairs move, sending a nerve impulse
-Detect direction because specialised receptors for each direction (e.g. leftwards)
Cutaneous Receptors
encapsulated (surrounded by a capsule)
or unencapsulated (includes free nerve endings).
Free nerve endings in the skin
-most common in skin; different forms
-Dendrite of sensory neuron
Polymodal (not specialised):
-Sensitive to painful stimuli, to hot and cold, and to light touch.
-Slow to adjust to a stimulus
What are the 4 primary tactile mechanoreceptors in the skin?
-Pacinian Corpuscles
-Ruffini’s Corpuscles
-Merkel’s disks
-Meissner’s corpuscles
Pacinian Corpuscle
-The specific capsule involved in pressure detection; important for detecting deep touch and vibration
-Rapidly-adapting (changing stimuli)
Involves both superficial & deep layers and hair
Ruffini’s Corpuscle
-Also found deep in dermis and subcutaneous tissue
-Also found in both glabrous and hairy skin
-Sensitive to stretching/sustained deep touch
-Slow adapting
Merkel’s Disk
-Unencapsulated
-Found in epidermis and deeper
-Also found in both glabrous and hairy skin
-Tonic receptors: sustained light touch
Slow adapting
Meissner’s Corpuscle
-Encapsulated receptor; found high within dermis
-Particularly found in glabrous skin, and finger pads
-Rapidly-adapting, sensitive to light touch (changing stimuli)
-Sensitive to shape and textural changes in exploratory and discriminatory touch (e.g., Braille)
Special receptors that detect temperature and pain.
Nociceptors detect pain and temperature
Thermoreceptors- separate hot and cold
Proprioception (6th sense)
-Location and movement of body (e.g. that sense of awareness of where limbs are)
-Proprioceptors are encapsulated nerve endings, sensitive to the stretch of muscles/tendons and joint movement
-Fastest fibres
What are the 2 systems of receptors
Rapidly adapting and slowly adapting receptors
Rapidly adapting receptors
(stimulated at beginning and end)
-Produce bursts of action potentials
-Involved in detecting discriminate touch (Meissner’s corpuscles) and fluttering (Pacinian corpuscles; faster)
Slowly adapting receptors
(tells that stimulus is still occurring; detect steady pressure)
-Light pressure: E.g. Merkel’s receptors and hair receptors
-When clothing is on, only these remain active
-Firmer pressure: Ruffini Corpuscle = vibration due to stretching (Ruffini corpuscles)
Different travel speeds
Haptic & proprioception carried by large, well-myelinated axons (faster, for rapid response)
‘Type A fibres’
Nociceptive info
Temperature, pain, tickle, itch: carried by smaller axons, with little or no myelination
(occurs for long time, so don’t need rapid response)
‘Type C fibres’
Certain fast pain carried by myelinated ‘Type A fibres’
Still slower than haptic/proprioceptive axon fibres
How fine touch and crude touch travels
-(Fine) Touch information ascends spinal cord ipsilaterally via the Dorsal Column Medial Lemniscal Pathway
-Nociceptive (and crude touch) information ascends contralaterally via the Spinothalamic Pathway(s)
Haptic proprioception route to the brain
-Axons for haptic-proprioception located in dorsal portion of spinal cord
-Synapse at base of brain in dorsal-column nuclei
-These then cross to other side of brainstem through medial lemniscus (in medulla)
-Synapse in ventrolateral thalamus
-Sends most axons to somatosensory cortex but some to motor cortex too
Nociception route to the brain
Axons for nociception synapse in dorsal part of spinal cord’s grey matter
Neurons send axons to ventral part of other side of spinal cord*
Some also send information to the somatosensory cortex*
Conscious, sensory aspects of pain
Also to insular and anterior cingulate cortex
Where is the primary somatosensory cortex located?
The post central gyrus
