W3: Brainstem, Cerebellum, Spinal Cord, CNS, PNS

Question 1

General functions of the brainstem

Answer 1

1) connects diecephalon to spinal cord
2) contains neuronal centers critical for survival
3) contains 10/12 cranial nerves

Question 2

RAS

Answer 2

aka Reticular Activating System

1) Located in the core of the brainstem
2) ascending RAS terminate in thalamus and cerebral cortex
3) incoming sensory axons synapse on RAS neurons
4) Function: consciousness - increased arousal in response to sensory information (wakefulness)

Question 3

Gerneral functions of the Cerebellum

Answer 3

1) coordinate and smooth body movements
2) postural control
3) equilibrium

Question 4

How many segments make up the cervical, thoracic, lumbar, and sacral areas of the spinal cord?

Answer 4

cervical = 8 segments
thoracic = 12 segments
lumbar = 5 segments
sacral = 5 segments

Question 5

Conus medullaris

Answer 5

end of CNS spinal cord

Question 6

filum terminale

Answer 6

filament from conus medullaris.

attaches to tail-like bone at coccxyl for stability

Question 7

What are the areas of the spinal cord that are wider than the rest and what are their name?

Answer 7

cervical enlargement

lumbar enlargement

Question 8

What is the common organization of the cerebellum layers?

Answer 8

I. molecular layer
II. Perkinje layer
III. Granular layer

Question 9

Perkinje cells

Answer 9

The only neurons that project to the deep cerebellar nuclei.

Question 10

Granular cells

Answer 10

Form parallel fibers. Project in opposite directions parallel to one another and synapse on a large number of perkinje cells.

Question 11

Where do afferent projections to the cerebellar cortex (mossy fibers) originate from? What kind of information do they receive?

Answer 11

1) vestibular nuclei (equilibrium)
2) Spinocerebellar tract - receptors in muscles, joints, tendons (movement & position of limbs)
3) Soma in the pons (motor)

Question 12

Where do afferent projections to the Purkinje cells (climbing fibers) originate from?

Answer 12

inferior olive

Question 13

What cells/neurons project to and from the deep cerebellar nuclei?

Answer 13

Purkinje cells project TO the deep cerebellar nuclei.

Deep cerebellar nuclei project TO the cerebellum.

Question 14

Where do efferent projections from the deep cerebellar nuclei to?

Answer 14

1) thalamus
2) reticular formation
3) vestibular nuclei

Question 15

What happens when to rats with cerebellum damage?

Answer 15

i.e. reeler mouse

coordination problems, falls often, slow jerky movements, drunken gait.

Question 16

Cauda equina

Answer 16

“horse tail”

dorsal/ventral roots

Question 17

What are the motor and sensory components of the spinal cord?

Answer 17

motor component = somatic motor neurons, axons exit in ventral root

sensory component = primary sensory neurons in dorsal root ganglia

Question 18

What type of nerves exit the dorsal and ventral ramus?

Answer 18

mixed spinal nerves = ventral and dorsal roots

Question 19

General observations of major spinal tract:

Answer 19

1) mostly decussate - contralateral projections
2) most form a chain of 2-3 neurons
3) most exhibit somatotopy
4) all are paired and mirror images of each other

Question 20

Decussate

Answer 20

to cross sides

Question 21

Contralateral

Answer 21

cell bodies and axonal pathways on opposite sides

Question 22

Cutaneous sensory receptors

Answer 22

receptors in the skin

Question 23

Free nerve endings

Answer 23

Important for transmitting pain and temperature.

Endings of a DRG that are ‘free’ in epidermis

Question 24

Pacinian corpuscles

Answer 24

‘small onion’
free nerve ending surrounded by layers.
Responds to deep pressure.

Question 25

Golgi tendon organs

Answer 25

Embedded in tendon.

Function: to keep tendon from pulling too hard/keeps cerebellum informed on tendon stretch.

Question 26

Muscle Spindle

Answer 26

small muscles encapsulated in large muscles.

Senses how much the large muscle is stretching and adjusts stretch accordingly (through spinocerebellar pathway)

Question 27

Dorsal ramus

Answer 27

Innervates muscles associated with back.at every spinal segment.
Generally always the SAME

Question 28

Ventral ramus

Answer 28

Innervates muscle and skin in the rest of the body (muscles between ribs, segmetnal muscles)
CHANGES throughout spinal cord.

Question 29

What is the nerve plexus organization of the ventral ramus?

Answer 29

1) Brachial C5-T1
2) Lumbar L1-L4
3) Sacral L4-S4
* lumbosacral plexus L1-S4

Question 30

Quadriplegic

Answer 30

All 4 limbs paralyzed.

• missing voluntary motor function/somatosensory feedback
• swelling of peripheral cells makes is hare for axons to grow back

Question 31

Paraplegic

Answer 31

Paralyzed only in lower extremities.

• no somatosensory, no voluntary, problem with bladder, bowls, sexual functions
• still have hyperactive spinal reflexes (withdrawal but don’t know why)