Somatic senses, motor control Flashcards
type of cell, location: nociceptors
for pain,
located at dermal/epidermal juction
- free nerve ending
type of cell, location: thermoreceptor
for absence/presence of heat
- free nerve ending
cold: epidermis
hot: in dermis
type of cell, location: hair root plexus
- free nerve ending, dermis
- around hair root
- touch sensation
type of cell, location: Merkel nerve ending
- free nerve ending
- mechanoreceptor (touch)
- epidermal/dermal junction
define nociception:
unpleasant sensation arising from noxious (unwanted) stimuli
types of nociceptors:
- mechanical
- thermo-mechanical
- polymodal (chemical, mechanical and thermal)
‘fast’ pain: type of pain, eg
A fibres
- acute, sharp pain
‘slow’ pain: type of pain, eg
C fibres
- burning, aching, throbbing pain
define thermoception:
sense of presence or absence of heat
list thermoreceptor types:
cold and warm
cold receptor features:
10-40˚C
- epidermis
- A fibres
warm receptor features:
32-48˚C
- dermis
- C fibres
type of cell, location: Meissner corpuscle
aka. tactile
- encapsulated cell
- for touch
- dermal/epidermal junction
type of cell, location: Ruffini corpuscle
aka bulbous
- encapsulated cell
- mechanoreceptor
- dermis
type of cell, location: Pacinian corpuscle
aka lamellar
- encapsulated cell
- mechanoreceptor
- deep dermis
define tactition:
sense of touch, pressure, vibration, tickle, itch
superficial mechanoreceptors:
- Meissner’s tactile corpuscle (fine touch)
- Merkel nerve endings (touch)
subcutaneous mechanoreceptors:
- Pacinian (lamellar) corpuscles (deep pressure)
- Ruffini (bulbous) corpuscles (stretch due to movement)
- hair root plexuses (movement of hair)
define proprioception:
- sense of movement, joint position sense, the sense of object’s weight
proprioceptors:
- muscle spindles
- Golgi tendon organs
- joint kinaesthetic receptors
muscle spindles: location
intrafusal muscle fibres:
- embedded inside skeletal m.
extrafusal muscle fibres: skeletal muscle
stimulus for muscle spindle:
muscle stretch (lengthening)
muscle spindles: fibre group
Type Aå
Type Bß
distribution: muscle spindles
skeletal muscles
how does stretch reflex work: general
stretch reflex causes contraction of muscle that has been stretched
morphology: Golgi tendon organs
- thin capsule of ct. over few tendon fascicles/ collagen fibres
- surrounded sensory nerve endings
stimulus: Golgi tendon organs
- tension
Golgi tendon organs: fibre group
Type Aå
Golgi tendon organs: location
musculotendinous junction of skeletal muscle
how does tendon reflex work: general
causes relaxation of muscle attached to stimulated tendon organ
3 main somatosensory pathways:
- dorsal column
- anterolateral system
- spinocerebellar pathways
1st order sensory neurons:
- from sensory receptor to spinal cord/ brainstem
- travel in peripheral nerves
- cell body located in dorsal root ganglion
2nd order sensory neurons:
- spinal cord to thalamus
- travel in spinal cord tracts
- decussate (cross over in ‘x’) in spinal cord/ brainstem
3rd order sensory neurons:
- thalamus to primary somatosensory cortex
- travel in internal capsule
dorsal column conveys:
- fine touch
- pressure
- vibration
- conscious proprioception
anterolateral system conveys:
- pain
- temperature
- itch
- tickle
