Ascending Pathways

Question 1

Hair follicle receptors

Answer 1

touch

Question 2

merkel endings

Answer 2

pressure and low frequency vibrations

Question 3

meissners corpuscles

Answer 3

light touch

Question 4

Pacinian Corpuscles

Answer 4

Vibration and JPS

Question 5

Ruffini Endings

Answer 5

skin stretch, pressure and JPS

Question 6

Nociceptors

Answer 6

Pain

Question 7

Muscle spindles

Answer 7

determine muscle length and proprioception

Question 8

Golgi tendon organs

Answer 8

JPS

Question 9

Meissner’s corpuscles receptive fields

Answer 9

these have limited receptive fields when they are in the tips of the fingers than when they are on the palms of the hands

Question 10

Pacinian receptive fields

Answer 10

however have generally large receptive fields each of which has a smaller more sensitive area within it

Question 11

What is the contents of a receptive field

Answer 11

in the centre of a receptive field dendrites are dense and then diffuse as they reach the periphery (this results in faster firing at the centre as they activate more dendrites)

Question 12

the concept of lateral inhibition

Answer 12

relies on reciprocal inhibition between two adjacent neurons where the extent of inhibition from each one is linked to the stimulus point on the neuronal receptive field overlap

Question 13

different axon types effect what

Answer 13

the speed of transmission of the information to the CNS

• Some modalities therefore are slower at being transmitted to the brain than others

Question 14

Fasciculus gracilis carries information from

Answer 14

the lower body extremities

Question 15

Fasciculus cuneatus carries information from

Answer 15

the upper body extremities

Question 16

Dorsal and ventral spinocerebellar tracts carry

Answer 16

proprioceptive information from muscle spindles (Dorsal) & Golgi organs (ventral)

Question 17

Spinothalamic tracts

Answer 17

pain and temperature transmission etc.

Question 18

where does en route sensory information pass through on its way to the cortex

Answer 18

thought the thalamus

EXCEPT OLFACTORY

Question 19

what is the thalamus

Answer 19

this acts as a relay station between the periphery and the cortex

• it has reciprocal connection to all the cortical regions and can read information, receive feedback and modulate cortical activity

Question 20

thalamic peduncles

Answer 20

they are thalamic connection that form between the thalamus and the cortex

Question 21

What are the three principle ascending tract systems of the spinal cord

Answer 21

1. Dorsal column-medial lemniscus pathways
2. Spinothalamic pathways
3. Spinocerebellar pathways

Question 22

Dorsal column - medial lemniscal pathway

mechanical stimuli

Answer 22

1. Conscious proprioception,
2. Discriminative touch,
3. Vibration and
4. Pressure

Question 23

Dorsal column - medial lemniscal pathway cortical functions

1.

Answer 23

To determine the shape of an object (without sight)
Proprioception from the finger joints and fine discriminating touch provides a very accurate model of any object that is handled

Question 24

Dorsal column - medial lemniscal pathway cortical functions

2.

Answer 24

2. To determine the texture of an object (without sight)
   Texture is determined by vibration and slip receptors as well as fine discriminating touch. Note pleasure can be associated with this pathway

Question 25

Lesions of one of the somatosensory association cortex leads to

Answer 25

amorphosynthesis’

Question 26

what is amorphosynthesis’

Answer 26

Patient unable to recognise complex object by feel on the opposite side to the lesion Patients often only explore one half of an object during testing of object recognition Patients can also neglect the whole of the opposite side of their body such that they overlook motor output on that side.

Question 27

what is one thing to note about patients with ‘amorphosynthesis’

Answer 27

these patients still have an appreciation of pain and temperature, they are unable to locate with any certainty the location of the source of the stimulus

Question 28

Lesions of the gracile fasciculus can cause

Answer 28

ait ataxia, as the brain (cortex and cerebellum) is deprived of information about the position of the feet.

Question 29

• Lesions in the cervical cord also cause

Answer 29

upper extremity ataxia. • Often patient is able to compensate with Vision and thus minimize sensory ataxia.

Question 30

Classic sign of gait (or sensory) ataxia is the

Answer 30

stamp and stick gait. • Patient stamps down feet to enhance sensory input and maintains a broad based stance.

Question 31

Spinothalamic Pathways are composed of what kind of fibres

Answer 31

Composed of smaller diameter (slow either Aδ or C fibres) with no specialized sensory endings Lightly or unmyelinated fibers which are ‘Quick to cross’

Question 32

Aδ fibres detect

Answer 32

non-discriminative touch (strong stimuli that does not damage the skin) heat or cold and sharp pain

Question 33

C fibres detect

Answer 33

ull aching pain and itch (histamine sensitive) plus thermal and mechanical

Question 34

1st order neurons synapse with 2nd order neurons in the

Answer 34

dorsal horn, which then decussate and ascend in either the lateral or anterior spinothalamic tract depending on the sensory modality

Question 35

when 2nd order neurones reach the thalamus

Answer 35

they synapse with 3rd order neurons which then projects to the sensory cortex in the same way as the dorsal lemniscal pathway

Question 36

Spinothalamic lateral route of the anterolateral spinothalamic pathway

Answer 36

Mixture of Aδ and C fibres | carrying information about pain and temperature via Aδ heat or cold activated fibres and C fibres (dull pain and itch)

Question 37

Spinothalamic anterior or ventral route of the anterolateral spinothalamic pathway

Answer 37

Only C fibres carrying | information about coarse, non discriminating touch via mechanosensitive fibres

Question 38

lesions in the lateral spinothalamic tract cause

Answer 38

decreased perception of pain and temperature on the contralateral side of the body, always one or two dermatomes below the level of the lesion.

Question 39

Spinothalamic tract lesions can cause

Answer 39

paraesthesia which is experienced as shooting pain or ‘electrical’ pain. Patients can also become aware of their pain and temperature deficit when they experience painless cuts or burns.

Question 40

The Neospinothalamic tract (lateral pathway)

Answer 40

which terminates in the ventral posterior lateral nucleus (VPL) is mainly composed of Aδ fibres.

Question 41

The Palaeospinothalamic tract (anterior pathway)

Answer 41

which terminates in the dorsomedial (DM) and intra laminar areas is composed of C fibres.

Question 42

Anterolateral tract lesions

Answer 42

Lesions in the neo part of the anterolateral tract cause decreased perception of pain and temperature on the contralateral side of the body, always one or two dermatomes below the level of the lesion (Lissauers tract). Used as a surgical procedure (cordotomy) for terminal disease pain, pain returns after about 1 year.

Question 43

Spinocerebellar pathway

Answer 43

Takes information about the body's position and movements to the cerebellum for integration with motor intention and other sensory inputs 2 principal routes for information, they are the anterior route and the posterior route (each of which only contains two neurones)

Question 44

where does motor information come from in the spinocerebellar pathway

Answer 44

from muscle spindles (muscle length), Golgi organs (proprioception) and touch receptors • used by cerebellum for the control of posture and co-ordination of movement

Question 45

where are the cell bodies of the 2nd order neurones located in the spinocerebellar pathway

Answer 45

in the dorsal horn of the spinal cord, and terminate in the vermis of the cerebellum

Question 46

lesions in the cerebellum always produce

Answer 46

ipsilateral effects. It is thought that some parts of the anterior pathway are double-crossed and others not, however the posterior pathway is entirely ipsilateral