Somatosensory system Flashcards
What do low threshold mechanoreceptors mediate?
Touch, vibration and pressure
What do low threshold thermoreceptors mediate?
Cold, cool, indifferent, warm and hot
Over what temperature is classed at “extreme heat”
45 degrees
What term describes cutaneous senses from the surface of the body?
Exteroceptive sensations
What term describes sensation concerning posture and movement? (Sensors located in muscle tendons and joints)
Propriceptive sensations
In sensory neurones; does a stimulus elicit a depolarizing or hyperpolarizing response?
Depolarizing
Which sensory neurones have the thickest layer of myelination
Proprioceptors of skeletal muscle; Aα receptors
Which sensory neurones have the thinnest layer of myelin?
Temperature, pain and itch “C” receptors.
What is the receptive field of a sensory neurone?
The region that, when stimulated with an adequate stimulus, causes a response in that neurone
Where are meissners corpuscles most abundant?
Skin where two point discrimination is highest
Where do you not get any meissners corpscules?
Hairy skin
What pathway carries the sensations of discriminatory touch, pressure vibration and conscious propriception from the sensory neurones to the brain?
Dorsal column medial lemniscal pathways
Where do the fibres of the dorsal column medial lemniscal pathway cross?
All cross together at the medulla
What pathway carries the sensations of pain, temperature, crude touch, itch and tickle from the sensory neurones to the brain?
Spinothalamic tract
Where do the fibres of the spinothalamic tract cross?
At all levels of the cord close to the point of entry.
What two tracts make up the dorsal column?
Gracile tract
Cuneate tract
What tract of the dorsal column carries sensory inputs from T6 and below?
Gracile tract
Of the gracile and cuneate tracts which is more medial and which more lateral?
Gracile tract is more medial and cuneate tract is more lateral
What tract of the dorsal column carries sensory inputs from above T6?
Cuneate tract
Where do the neurones travelling in the gracile tract synapse?
Dorsal column gracile nucleus
Where do the neurones travelling in the cuneate tract synapse?
Dorsal column cuneate nucleus
In the dorsal column medial lemniscal system; where do the second order neurones cross, and where do the ascend after this?
Axons from second order neurones cross in the great sensory decussation and ascend in the medial lemniscus.
After the second order neurones of the dorsal column medial lemniscus pathways have ascended up the medial lemniscus pathway where on the thalamus do they synapse?
The ventral posteriolateral nucleus of the thalamus
Where do the third order neurones in the dorsal column medial lemniscus pathway project to? What do they have to go via to get here?
Primary somatosensory cortex
Posterior internal capsule
