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Flashcards in Ascending Sensory Pathways Deck (66)
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1

What does somatosensory mean?

Relating to a sensation that can occur anywhere in the body (e.g. pain), rather than localised at one organ (e.g. sight).
-I.e. senses other than 5 senses

2

What are the 2 groups of somaesthetic modalities?

-Modalities that are essential to survive
-Modalities that increase detail

3

What sort of modalities are essential to survive?

Pain, temperature, some touch & pressure.

4

What fibres carry modalities that are essential for survival?

Thin, unmyelinated fibres.
-relatively slow conduction

5

What sort of modalities increase detail?

-Discriminative touch (2-point and vibration)
-Proprioception

6

What fibres carry modalities that increase detail?

Large, very myelinated fibres.
-fast conduction

7

What is proprioception?

The body's ability to sense movements in joints and joint positions.

8

What is the general mechanism of proprioception?

Golgi tendons/muscle spindles sense degree of tension/stretch in muscles >> CNS.

9

What is a pseudounipolar neuron?

Sensory neuron in PNS with a single stalk that splits into 2 processes.
(1 >> periphery, 1 >> spinal cord)

10

What is a nucleus?

Collection of cell bodies in the CNS.

11

What is a ganglion?

Collection of cell bodies in the PNS.
-e.g. dorsal root ganglion

12

How many neurons do general sensory pathways consist of?

Three.
-1*/2*/3*

13

Where do the cell bodies of sensory 1* neurons in the PNS reside?

Dorsal root ganglion.

14

Where do the cell bodies of sensory 1* neurons in the CNS reside?

Cranial nerve nuclei.

15

Where do 1* neurons synapse?

In the CNS (spinal cord/brain) on the same side as they entered the cord (ipsilateral).

16

Which neuron crosses the midline?

2* neuron.

17

Where do 2* neuron cell bodies reside?

In ipsilateral grey matter in the CNS.

18

What happens to 2* neurons once they cross the midline?

They ascend to the thalamus.
-VPL nucleus (from body)
-VPM nucleus (from face)

19

Where do 3* cell bodies reside?

In the thalamus.

20

Where do the 3* axons project?

3* axons project to the somatosensory area of the post-central gyrus.
-Contralateral 1* neuron origin

21

What does somatotopic mean?

Point-to-point correspondence.
-area of body >> specific point on post-central gyrus

22

Are general sensory pathway somatotopic?

Yes.

23

Is synaptic transmission from 1*, 2* and 3* neurons a simple relay? Give 3 examples.

No, can be modified by other inputs.
-e.g. diverging circuit, converging circuit, descending pathways

24

What is a diverging circuit?

One pre-synaptic neuron stimulates a response in multiple post-synaptic neurons. Increases the amount of info to CNS, and allows brain signals to travel to various locations of the body.

25

What is a converging circuit?

Several pre-synaptic neurons stimulate one post-synaptic neuron. Focuses information.

26

What is the general pathway of sensory information to the face?

Sensory stimulus >> 3 neurons >> thalamus (VPL/VPM) >> post-central gyrus.

27

Which arteries in the medial hemisphere supplied by?

Anterior cerebral arteries.

28

What are the main ascending and descending fibre tracts? (4)

-Dorsal column
-Spinothalamic
-Lateral corticospinal
-Ventral corticospinal

29

What are the major ascending tracts? (2)

-Dorsal column pathway
-Spinothalamic pathway

30

What information does the spinothalamic pathway carry?

Pain, temperature, light touch and pressure.