Neruo 3 Somatic Sensation and Ascending Tracts Flashcards Preview

ESA 5 > Neruo 3 Somatic Sensation and Ascending Tracts > Flashcards

Flashcards in Neruo 3 Somatic Sensation and Ascending Tracts Deck (80)
Loading flashcards...

Explain the first order, second order, and third order neurones in the somatosensory system

First order - pass electrical stimulus to spinal cord

Second order - ascends to the brain and synapses with the third order neurone

Third order - Cell body Located in the ventral posterior nucleus in the thalamus of the brain takes the impulse to the necessary part of the brain


Where is the ventral posterior nucleus located? What is it?

It is the somatosensory relay nucleus in the thalamus of the brain


What neuron is used for the sensation of pressure, vibration, and texture?

Merkel Discs


What type of neuron is used for the sensation of light touch and vibration?

Meissner's corpuscle


What neuron is used for the sensation of temp?

Riffini corpuscle


What neuron is used for the sensation of pressure?

Pacinian corpuscle


What are proprioceptors and where are they located? What types are there?

Proprioceptors in the muscles tells the body where it is in space and allows it to function properly.

2 main types:

  • muscle spindle tells about the length of the muscle
  • Golgi tendon organ measures tension in the tendons


How is an intense stimulus transmitted in a neuron?

Frequency coding - Strength determined by rate of APs

Activation of neighbouring cells


What are tonic and phasic receptors? Give example of each

Tonic receptors - slowly adapting and keep firing as long as stimulus lasts e.g. joint and pain receptors

Phasic - rapidly adapting and respond briefly to a stimulus e.g. touch receptors


Define acuity

Precision by which a stimulus can be located


How is acuity improved by lateral inhibition?

Sitimulation of a 1st order neurone will inhibit the adjacent 2nd order neurones so that the stimulus is only felt in the correct 2nd order neurone


Define 2 point discrimination

minimal interstimulus distance required to percieve 2 simultaneously applied skin indentations


What is the link between 2 point discrimination and the size of neuronal receptive fields?

Smaller neuronal receptive field = better 2 point discrimination


Define convergence and divergence of a signal

Convergence - 2+ first order neurones converge onto a single 2nd order neuron

Divergence - 1 first order neurone diverges into 2+ 2nd order neurones


Where is the somatosensory cortex located?

Post central gyrus


How is the white matter of the spinal cord divided?

Funiculi - dorsal, lateral and ventral


How is the grey matter of the spinal cord divided? 

Divided into X laminae. Each laminae is equivalent to a neuronal nucleus. Cell bodies of neurones with common functions occur in the same laminae


How many pairs of segmental nerves are there?

31 pairs


Which nerve carries the majority of the cranial sensory system?



Where is priority given in the sensory homonculus?

Face, hands, tongue


What are the 2 categories into which ascending tracts can be divided into?

Conscious and non conscious sensation


What are some examples of non conscious sensation?

muscle length, muscle tension, joint angle


Where is the cell body of spinal sensory neurones located?

Dorsal root ganglion of that spinal segment


What type of neurone is the first order neuron of the somatosensory system?



How would you orientate the spinal cord?

dorsal median sulcus is posterior and is a groove in the spinal cord

Ventral median fissure is an opening at the anterior end o the spinal cord


What runs through the central canal of the spinal cord?



What is the function of the dorsal column - medial lemniscus pathway of the spinal cord?

Fine touch and proprioception


What is the dorsal column - medial lemniscus pathway made up of? To where does it transmit information to?

Cuneate and gracile

Post central gyrus


What does the lateral corticospinal tract carry?

limb motor information


Label the ascending pathways