Somatosensory System Part 3 SN

Question 1

What is the Ventral Horn and Dorsal Horn referring to?

Answer 1

The grey matter (where cell bodies lie)

Question 2

Where do large neurons lie?

Answer 2

Ventral Horn

Question 3

Where do small neurons lie?

Answer 3

Dorsal Horn

Question 4

In the white matter, what are dorsal columns?

Answer 4

Ascending axons only

Question 5

In the white matter, what are lateral columns?

Answer 5

Ascending and Descending axons

Question 6

What are descending axons?

Answer 6

Interneurons and Motor Neurons

Question 7

In the white matter of ventral columns, what are descending responsible for?

Answer 7

Axial and postural muscles

Question 8

In the white matter of ventral columns, what are ascending responsible for?

Answer 8

Pain and temperature

Question 9

What are the fascicles involved in Ascending Axons?

Answer 9

Gracile and Cuneate Fasicles

Question 10

What do sensory neurons do?

Answer 10

Get information from body surface

Question 11

What do motor neurons do??

Answer 11

Innervate Skeletal Muscles

Question 12

What do Sacral Levels contain?

Answer 12

Few axons, less white matter

Question 13

What do Cervical Levels Contain?

Answer 13

Many axons, more white matter

Question 14

Where are descending axons mostly found in?

Answer 14

Cervical Level

Question 15

What are Larger Ventral Horns?

Answer 15

Spinal Levels that innervate arms and legs

Question 16

What do Larger Ventral Horns have more of?

Answer 16

Motor Neurons

Question 17

What does more motor neurons mean?

Answer 17

They have to innervate more muscle cells

Question 18

What do larger dorsal horns reflect?

Answer 18

A greater density of sensory receptors which can send more fibres to spinal cord.

Question 19

Where do ascending axons and somatotropin distribution start?

Answer 19

Sacral Regions

Question 20

What happens in sacral regions?

Answer 20

Axons move into pathways more medial in dorsal columns

Question 21

What happens in sacral to cervical regions?

Answer 21

Progressive Merging of axons medial to lateral

Question 22

What happens in Gracile Fascicle?

Answer 22

• Medial Clustered Neurons….motor fibres from lower extremities
• Terminates in gracile nucleus (cluster of neurons in spinal cord)

Question 23

What happens in the Cuneate Fascicle?

Answer 23

• Lateral Clustered Neurons
• Terminates in Cuneate Nucleus

Question 24

What is the Medial Lemniscus?

Answer 24

• Long Fibre Bundles from Medulla Oblongata
• Synapses onto thalamic relay nuclei (VP nucleus)
• Arranged somatotopically

Question 25

What is the Thalamus?

Answer 25

- Conveys sensory input to sensory axons of cerebral cortex and transmit and modulates inputs (motor information)

Question 26

What is the Thalamus made up of?

Answer 26

50 distinct nuclei

Question 27

Where do output axons travel through in the Thalamus?

Answer 27

The internal capsule

Question 28

What are the 4 major groups of the thalamus?

Answer 28

Anterior, Medial, Ventral, Posterior

Question 29

What is the Anterior Part of the Thalamus responsible for?

Answer 29

- Major inputs from hypothalamus and hippocampus - involved with Memory and Emotion - Connection with Frontal Cortex

Question 30

What is the Medial Part of the Thalamus responsible for?

Answer 30

- 3 Sub-Divisions - Connections to Frontal Cortex, Memory - Inputs from Basal Ganglia, amygdala

Question 31

What is the Ventral Part of the Thalamus responsible for?

Answer 31

- Motor Control, relays information from Basal Ganglia and Cerebellum - Conveys to Somatosensory

Question 32

What is the Posterior Part of the Thalamus responsible for?

Answer 32

- Auditory Nuclei, conveys to temporal lobe - Input from Retina, conveys to visual cortex (occipital lobe)

Question 33

What are Relay Nuclei?

Answer 33

Neuron clusters that terminate onto specific regions of cortex.

Question 34

What is the Reticular Nucleus?

Answer 34

- The outer covering of thalamus, sheet-like neurons

Question 35

What does the thalamic relay nuclei release?

Answer 35

Glutamate (excitatory)

Question 36

What does Thalamic Nuclei (Outgoing) send?

Answer 36

Collaterals to Reticular Nucleus

Question 37

What is the function of the Reticular Nucleus?

Answer 37

Modulates activity of thalamic nuclei and monitors the thalamocorticol stream of information

Question 38

What does somatosensory information consist of?

Answer 38

- Primary Somatosensory Cortex (S1) - Broadmann's Area (3b) - Area of Cortex devoted to body parts, not mass

Question 39

What is the Primary Somatosensory Cortex?

Answer 39

Anterior Parietal Cortex

Question 40

What are the 4 complete maps of skin in the Primary Somatosensory Cortex?

Answer 40

3a, 3b, 1 and 2

Question 41

What does Area 2 mediate?

Answer 41

Tactile information is combined with limb position which mediates tactile recognition of objects

Question 42

How does the Primary Somatosensory Cortex project to other areas of cortex?

Answer 42

- Motor Control - Eye-Hand Coordination - Memory Related to Touch

Question 43

What is voluntary movement?

Answer 43

Primary motor cortex that is somatotopically organized

Question 44

What does voluntary movement project through?

Answer 44

Corticospinal tracts to ventral horn of spinal cord through internal capsule (apart of the mid brain)

Question 45

What are Direct Connections in Voluntary Movement?

Answer 45

Ventral Motor Neurons that are monosynaptic

Question 46

What are Indirect Connections in Voluntary Movement?

Answer 46

Through Interneurons, coordinates large muscle groups

Question 47

How is voluntary movement modulated by?

Answer 47

Sensory Information and Other Motor Region (cerebellum, basal ganglia, pre-motor)

Question 48

What are the inputs of the cerebellum?

Answer 48

Somatosensory primary afferent and corticospinal axons

Question 49

What are Error Correcting Mechanisms?

Answer 49

- Predictive Control of Movements - Outgoing Commands adjusted based on information based on information about the reflections of prior movements

Question 50

What are posture and movements in relation to the cerebellum?

Answer 50

- Connections to brain stem nuclei - Direct modulation of spinal motor circuits - Major influence through thalamic connections