CNS: Sensory

Question 1

Purpose of the sensory system

Answer 1

To bring afferentiation (info from tissue) to the CNS for analysis, interpretation and assignment of sensation experiences

Question 2

Sensory system: usually composed of 3 neurons:

Answer 2

1. Sensory neuron/1st order neuron/primary neuron
2. 2nd order neuron
3. 3rd order neuron

Question 3

Intervertebral foramen

Answer 3

Dividing line between CNS and PNS

Question 4

1st order neuron: location of receptor cells?

Answer 4

In the tissue

Question 5

2nd order neuron: location?

Answer 5

In spinal cord

Question 6

All sensation is ___________

Answer 6

…assigned by the brain.

Question 7

2nd order neurons convey transmission to ______

Answer 7

…the thalamus

Question 8

3rd order neurons fxn?

Answer 8

Relay neurons from the thalamus to various brain centres, incl. the sensory cortex where sensation is appreciated and assigned.

Question 9

Nociception vs. pain

Answer 9

Nociception = afferentiation
Pain = The experience\interpretation as 'pain' by CNS

Question 10

Homunculous: location

Answer 10

Sensory Cortex

Question 11

Brain challenges in interpreting/assigning sensation (6)

Answer 11

1. Convergence
2. Personal Hx
3. Proximal Depolarization Phenomenon
4. Phantom Phenomena
5. Central Modulation Issues
6. NS Damage/Pathology

Question 12

Convergence: define

Answer 12

Brain challenge in interpretation/assigning sensation: There are a much larger # of 1st order neurons than 2nd order neurons and more 2nd order neurons than 3rd order neurons, so the brain is trying to interpret a ‘summary’ of info from the tissue. Brain may choose what’s ‘most likely’ occurring until it gets more info.

Question 13

Brain challenge in interpretation/assigning sensation: personal Hx: explain.

Answer 13

Personal hx means the brain is more likely to assign sensation based on a previous experience.

Question 14

Proximal depolarization phenomenon: def

Answer 14

If an afferent neuron is depolarized at a location other than its receptor, the info will still travel to the sensory appreciation zone for the supplied tissue, so the brain is most likely to assign sensation there.

Question 15

Phantom phenomena: def

Answer 15

Sensation in a missing body part; afferent stim. of remaining 1st order neuron segments generates transmission to the section of the sensory cortex that ‘assigns’ sensation to the missing part.

Brain also tries to ‘resolve’ the circuiting dilemma and often assigns sensation to the missing part in dreams and waking moments.

Question 16

Brain challenge in interpretation/assigning sensation: central modulation issues: define/explain

Answer 16

Info arriving at the thalamus/sensory cortex is filtered and only ‘meaningful’ info results in sensation. The rest is ‘suppressed’, prevented from generating experience. This central modulation relies on neurochemicals like serotonin and endorphins.

If there is a chemical depletion or damage in the cent. modulation fxn, the person may have undesired or less meaningful sensory experiences. Depression is an example of this.

Question 17

Brain challenge in interpretation/assigning sensation: NS damage/pathology: explain

Answer 17

This will greatly increase the challenges the brain experiences, either by distorting the afferentiation or impairing the analysis fxn.