Sensiomotor circuits

Question 1

What is meant by the general modality of sensory info [3]

Answer 1

• info from anywhere in the body to CNS
• transmitted through spinal nerves
• pain, touch, pressure, temperature etc.

Question 2

What is meant by the special modality pf sensory info [3]

Answer 2

• localised to specific
• transmitted through spinal nerves (cranial)
• vision, hearing, taste

Question 3

What are the four divisions of the spinal cord

Answer 3

• cervical
• thoracic
• lumbar
• sacral

Question 4

Define dermatome

Answer 4

area of skin innervated by each spinal segment

Question 5

Describe how the dorsal columns are positioned on the spinal cord.

Answer 5

from medial to lateral
- sacral
- lumbar
- thoracic
- cervical

Question 6

Label somarosenry pathways x3

Answer 6

see notes

Question 7

where do axonal projections originate from [1]

Answer 7

dorsal root ganglion

Question 8

describe the 3 step relay process in the dorsal columns tract

Answer 8

• 1st order neurones: dorsal horn to dorsal column nuclei
• 2nd ON: dorsal columns nuclei to thalamus
• 3rd ON: thalamus to somatosensory cortex

Question 9

Where does decussation occur in the dorsal columns tract

Answer 9

• dorsal columns nuclei
• nucelus gracilis and cuneatus

Question 10

What are the two components of the spinothalamic tract

Answer 10

• anterior spinothalamic tract
  -lateral spinothalamic tract

Question 11

Describe the three step relay process of the spinothalamic tract [3]

Answer 11

• 1st ON: sensory receptor to dorsal horn of the spinal tract
• 2nd ON: decussates and projects from dorsal horn to the ventral posterior nucleus to thalamus
• 3rd ON: thalamus to the primary somatosensory cortex

Question 12

Where decussation occur in the spinothalamic tract

Answer 12

in the spinal cord

Question 13

Describe the pathway of the trigemiothalmic tract [4]

Answer 13

• axons from sensory neurones converge into trigeminal nerve (cranial nerve V)
• first synaptic relay at level of trigeminal nucleus (pons)
• second synaptic relay in the thalamus
• third synaptic relay in the thalamus

Question 14

Where does decussation occur in the trigeminothalamic tract

Answer 14

pons

Question 15

What is the role of trigeminal tract

Answer 15

• somatosensory info from the head and neck

Question 16

What is meant by the thalamus is the getaway to the cortex

Answer 16

relays all sensory info (other than olfaction)

Question 17

What Broadman’s area is the somatosensory cortex?

Answer 17

3b

Question 18

Where does the somatosensory cortex receive projections from

Answer 18

VP nucleus of the thalamus

Question 19

What other areas is the primary somatosensory cortex flanked by and what are their function [3]

Answer 19

• Area 3a: processing of body position
• area 1: involved in the processing of texture
• area 2: processing of shape

Question 20

How many layer of the cortex are there

Answer 20

6

Question 21

Which layer of the cortex do thalamic component arrive

Answer 21

layer IV

Question 22

What is the difference between fast adapting and slow adapting neurones [2]

Answer 22

• slow will continue to response to stimulus
• while fast reopen only at onset (or offset) of stimulus

Question 23

Describe the experiment that showed somatosensory plasticity [4]

Answer 23

• area of somatosensory cortex processing sensory info mapped under normal conditions
• then mapped after the removal of finger from monkey
• innervation caused major rearrangement of the cortical processing area where finger was lost
• areas where lost finger originally mapped to become mapped to adjacent fingers

Question 24

What is meant by sensorimotor intergration [3]

Answer 24

• sensory info integrated
• in frontal assertion area
• results in generation of motor commands

Question 25

What are the two main types of fibres [2]

Answer 25

- association fibres - commissural fibres

Question 26

What is the difference between short and and long range association fibres [2]

Answer 26

- link areas of the cortex/ link distant cortical areas - between adjacent sulci/ travel along white matter

Question 27

Descrie commissural fibres

Answer 27

- connect corresponding regions between hemispheres

Question 28

What is the importance of commissural fibres

Answer 28

- allow appearance of coordinated patterns of activity - coordinated activity between both sides

Question 29

What areas are associated with the planning of movement [3]

Answer 29

- PFC - PPC - motor cortex

Question 30

How is the PFC involved in planning of movement [2]

Answer 30

- integrates sensory info - evaluation of need for motor action

Question 31

How is the PPC involved in the planning of movement [2]

Answer 31

- intergrates spatial relationship between body and environment - transmits outcomes to motor cortex

Question 32

Describe the role of the motor cortex in the planning of movement [2]

Answer 32

- supplementary motor area (SMA) and premotor area (PMA) initiate and coordinate motor commands to generate movement - primary motor cortex (M1) activates specific muscle fibres for groups of muscles needed for movement

Question 33

Describe a study that showed the brain is capable of motor plasticity [3]

Answer 33

- areas of different muscle movements mapped to rat primary motor cortex - denervation of vibrissae - areas of primary motor cortex that vibrissae was mapped to before denervation now mapped to other body part

Question 34

What are two major motor pathways [2]

Answer 34

- direct / pyramidal - indirect / extrapyramidal

Question 35

Describe the direct motor pathway

Answer 35

upper motor neurones from PMC provide direct input to lower motor neurones in spinal cord/brainstem

Question 36

Identify the tracts that undergo the direct the direct motor pathway [2]

Answer 36

corticospinal corticobulbar

Question 37

Describe the indirect motor pathway

Answer 37

- motor commands to lower motor neurones are provided by the motor centres in the brainstem

Question 38

Identify the tracts in the indirect motor pathway [4]

Answer 38

- rubrospinal - tectospinal - vestibulospinal - reticiulospinal

Question 39

What are the two division of the corticospinal tract

Answer 39

lateral anterior

Question 40

What does the lateral corticospinal tract decussate

Answer 40

at the level of the pyramids

Question 41

where does the anterior corticospinal tract

Answer 41

at the spinal cord

Question 42

Where does the lateral cortcispinal tract innervate

Answer 42

skeletal muscles

Question 43

where does the anterior corticospinal tract innervate

Answer 43

trunk and proximal parts of the limbs

Question 44

Where are the upper motor neurones of the cotciobulbar tract located

Answer 44

head and neck area of the motor cortex

Question 45

Where are the axonal projection of the upper motor neurones sent through

Answer 45

corona radiata

Question 46

Describe the pathway for the lower motor neurones of the corticobulbar tract [3]

Answer 46

- located in the cranial nerve nuclei of the brainstem - axons from motor components of cranial nerves innervate head and neck - not all axons will decussate

Question 47

Where does the extrapyramidal pathway originate

Answer 47

motor nuclei of the brainstem

Question 48

identify the tract for the brain areas midbrain, pons, medulla

Answer 48

midbrain: tectospinal and rubrospinal pons: vestibulospinal medulla: rectospinal

Question 49

Where are lower motor neurones located

Answer 49

- ventral horn of the spinal cord

Question 50

What is meant by signal nerves are mixed nerves

Answer 50

contain both sensory component and motor component

Question 51

What is meany by the term motor unit

Answer 51

one motor neurone and all the muscle fibres that it innervated

Question 52

What is a neuromuscular junction [2]

Answer 52

- synapse between lower motor neurones and individual muscle fibres - one neurone for many muscle fibres

Question 53

Define the term myotome

Answer 53

- group of muscles innervated by all the lower motor neurones in a single spinal nerve

Question 54

What is a motor neurone pool

Answer 54

all the motor neurones that innervate a single muscle

Question 55

Why are there different sizes of motor pools [2]

Answer 55

- need larger motor pools for finer movements - and can have smaller motor pools for larger movements