W3: Brainstem, Cerebellum, Spinal Cord, CNS, PNS Flashcards
General functions of the brainstem
1) connects diecephalon to spinal cord
2) contains neuronal centers critical for survival
3) contains 10/12 cranial nerves
RAS
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)
Gerneral functions of the Cerebellum
1) coordinate and smooth body movements
2) postural control
3) equilibrium
How many segments make up the cervical, thoracic, lumbar, and sacral areas of the spinal cord?
cervical = 8 segments thoracic = 12 segments lumbar = 5 segments sacral = 5 segments
Conus medullaris
end of CNS spinal cord
filum terminale
filament from conus medullaris.
attaches to tail-like bone at coccxyl for stability
What are the areas of the spinal cord that are wider than the rest and what are their name?
cervical enlargement
lumbar enlargement
What is the common organization of the cerebellum layers?
I. molecular layer
II. Perkinje layer
III. Granular layer
Perkinje cells
The only neurons that project to the deep cerebellar nuclei.
Granular cells
Form parallel fibers. Project in opposite directions parallel to one another and synapse on a large number of perkinje cells.
Where do afferent projections to the cerebellar cortex (mossy fibers) originate from? What kind of information do they receive?
1) vestibular nuclei (equilibrium)
2) Spinocerebellar tract - receptors in muscles, joints, tendons (movement & position of limbs)
3) Soma in the pons (motor)
Where do afferent projections to the Purkinje cells (climbing fibers) originate from?
inferior olive
What cells/neurons project to and from the deep cerebellar nuclei?
Purkinje cells project TO the deep cerebellar nuclei.
Deep cerebellar nuclei project TO the cerebellum.
Where do efferent projections from the deep cerebellar nuclei to?
1) thalamus
2) reticular formation
3) vestibular nuclei
What happens when to rats with cerebellum damage?
i.e. reeler mouse
coordination problems, falls often, slow jerky movements, drunken gait.
Cauda equina
“horse tail”
dorsal/ventral roots
What are the motor and sensory components of the spinal cord?
motor component = somatic motor neurons, axons exit in ventral root
sensory component = primary sensory neurons in dorsal root ganglia
What type of nerves exit the dorsal and ventral ramus?
mixed spinal nerves = ventral and dorsal roots
General observations of major spinal tract:
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
Decussate
to cross sides
Contralateral
cell bodies and axonal pathways on opposite sides
Cutaneous sensory receptors
receptors in the skin
Free nerve endings
Important for transmitting pain and temperature.
Endings of a DRG that are ‘free’ in epidermis
Pacinian corpuscles
‘small onion’
free nerve ending surrounded by layers.
Responds to deep pressure.
Golgi tendon organs
Embedded in tendon.
Function: to keep tendon from pulling too hard/keeps cerebellum informed on tendon stretch.
Muscle Spindle
small muscles encapsulated in large muscles.
Senses how much the large muscle is stretching and adjusts stretch accordingly (through spinocerebellar pathway)
Dorsal ramus
Innervates muscles associated with back.at every spinal segment.
Generally always the SAME
Ventral ramus
Innervates muscle and skin in the rest of the body (muscles between ribs, segmetnal muscles)
CHANGES throughout spinal cord.
What is the nerve plexus organization of the ventral ramus?
1) Brachial C5-T1
2) Lumbar L1-L4
3) Sacral L4-S4
* lumbosacral plexus L1-S4
Quadriplegic
All 4 limbs paralyzed.
- missing voluntary motor function/somatosensory feedback
- swelling of peripheral cells makes is hare for axons to grow back
Paraplegic
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)
