A & P - Sensory Nervous System Flashcards
which receptor is responsible for awareness of limb position?
proprioceptors
what are chemoreceptors responsible for?
detection of chemicals
which receptor detects physical distortion?
mechanoreceptors
describe the steps in the somatosensory pathway I
- Activation of sensory receptors
- Transmission of sensory input to spinal cord or brainstem(1st order neuron)
- transmission of signal via ascending pathways through thalamus (2nd order) to primary cortex (3rd order)
- conscious perception
when sensory signals reach the primary cortex what is the signal checked for?
defection size modality (type of specific sense. eg. touch, pain, vision) frequency quality pattern
what are sensory receptors?
pseudo-unipolar cells
what is the name for a sensory receptor who’s endings are not in the connective tissue?
un-encapsulated - free nerve ending (eg. special senses)
where are the nerve endings of encapsulated sensory receptor found?
wrapped in glia or connective tissue
what is increased in encapsulated sensory receptors?
sensitivity
selectivity in respect to modality
how many pairs of spinal nerves are there? list the segments
31 pairs
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coxygeal
spinal nerves carry impulses via sensory or motor axons?
both - they are mixed
what does white matter in the spinal cord consist of?
mostly myelinated and unmylinated axons in ascending and descending tracts
what does grey matter in the spinal cord consist of?
mostly cell bodies of motor neurones and neuroglia
what information do the descending tracts of the spinal cord carry?
motor commands
what information do the ascending tracts of the spinal cord carry?
sensory input
what sensory information does the dorsal white column carry?
fine touch
properioception
what sensory information does the spinothalamic tract carry?
anterior- crude touch & pressure
posterior - temperature & pain
what sensory fibres does the dorsal column pathway use?
large diameter myelinated
describe the dorsal column pathway
bilateral
generates contralateral signals
fast
describe the locations of the dendrites, cell bodies and axons of the 1st, 2nd and 3rd order neurones in the dorsal column pathway
1st order
dendrites - periphery, cell body - DRG, axon - terminals in brain stem
2nd order
dendrite & cell body - brainstem, axon - decussates, projects into thalamus
3rd order
dendrites & cell body - thalamus
axon - projects into sensory cortex
what sensory fibres does the spinothalamic pathway use?
small unmyelinated axons
describe the spinothalamic pathway
bilateral
contralateral signals
slow
what is caused by a disturbance in the spinothalamic pathway?
phantom limb pain
referred pain
describe the locations of the dendrites, cell bodies and axons of the 1st, 2nd and 3rd order neurones in the spinothalamic pathway
1st order
dendrites - periphery, cell body - DRG, axon - terminates in spinal cord
2nd order
dendrites & cell body - spinal cord
axon - decussates, projects into thalamus
3rd order
dendrites & cell body - thalamus, axon - projects into sensory cortex
how would pain in the head travel to the cerebral cortex via the pain signalling pathway?
from cranial nerves - CNV, VII, IX, X
brainstem (1st order)
thalamus (2nd order)
cerebral cortex (3rd order)
in the pain signalling pathway which tracts carry which information?
spinothalamic tract - most somatic pain signals to cortex - perception
spinorecticular tract - visceral, emotional, behavioural
posterior column - visceral pain
which nerves make up the sciatic nerve?
L4 - S3
where is the primary motor cortex located?
parietal lobe in post central gyrus
what are nociceptors activated by?
chemical release from injured tissue
when tissue is injured what chemicals are released?
bradikins prostaglandins histamine ATP K+
what is 1st pain?
myelinated axon
fast conduction
sharp, localised, stabbing pain
what is 2nd pain?
unmyelinated axons
slow conduction speed
long lasting dull pain
what are dermatones?
areas of skin innervated by sensory branch of single nerve
how can dermatones be used as a diagnostic tool?
to pin point pain associated with spinal nerves
what role does pain play in homeostasis?
protects and preserves body
what is referred pain?
pain perceived at predictable site away from actual injury
what is chronic pain?
no disease or injury
no biological purpose
psychological
what is acute pain?
provoked by disease or injury
biological purpose to protect
SNS activation
what would cause a lack of pain perception?
genetic
diabetes
drugs
why do we feel referred pain?
skin and visceral nociceptive neurons on 1 interneuron
brain can’t distinguish source of pain
pain felt at surface of skin
