PROTECTIVE MECHANISMS OF CNS Flashcards
Protecting the CNS
Bones
* Skull and vertebrae
* Membranes
* ___Meninges____________
* Fluid Cushioning
* Cerebrospinal fluid (CSF)
* Chemical Protection
* ____Blood Brain Barrier__________
Meninges
Lining that serves protective and nutritive functions
* __Dura______ mater
* Most superficial
* Tough lining
* Arachnoid mater
* Location of many blood vessels
* Spider like structure
* Pia mater
* Thin membranous lining
Meninges: Dura Mater
Outermost membrane
* Touch, thick, fibrous
* Provides maximum meningeal
protection to CNS
* Attach to inner surface of
skull; overlies arachnoid
membrane
Two potential spaces around
dura
* Epidural: potential space
between dura and skull
* Subdural: potential space
between dura and arachnoid
Meninges: Pia Mater
Meninges: Pia Mater
* Thin, transparent
membrane
* Envelops entire surface of
brain
* Follows contours of gyri
and sulci
* Contains blood vessels;
adheres to brain surface.
Meninges: Arachnoid Mater
Meninges: Arachnoid Mater
* Subarachnoid space (between arachnoid membrane and pia
mater)
* Web-like extensions (arachnoid trabeculae) stretch into
the subarachnoid space which is filled with CSF.
* Transfers CSF back into bloodstream.
Cerebrospinal Fluid (CSF)
Cerebrospinal Fluid (CSF)
* Clear fluid
* Helps with removal of the products of neuronal
metabolism
* It acts as a protective cushion around the brain and
spinal cord
* Circulates from ventricles to subarachnoid space
(lateral third fourth SAS;__Subarachnoid space______________)
Choroid Plexus
CSF is found throughout the
ventricles and other cavities.
* CSF is produced by the choroid
plexus.
* CSF circulates through and
around the CNS and
eventually reaches the
venous system.
CSF: Ventricles
Fluid filled cavities - ventricles
* Circulate the cerebrospinal fluid
(CSF)
* Two lateral ventricles - each
hemisphere; connects to 3rd ventricle
* 3rd ventricle – diencephalon;
connects to 4th ventricle via cerebral
aqueduct
* 4th ventricle - pons & medulla;
contains openings into subarachnoid
space
Blood-Brain Barrier (BBB)
A layer of specialized
endothelial cells in the
brain
* Restricts substances
from diffusing out of
CNS capillaries from
bloodstream to brain
tissue
* Regulates what gets
into CNS extracellular
space
Blood-Brain Barrier (BBB)
* Clinical significance of BBB?
Clinical significance of BBB?
* Prevents microorganisms and some medications
(antibiotics) from reaching brain
* May be compromised by brain tumors, meningitis, AD,
epilepsy, and MS
Example of BBB in AD
Cerebellum
Coordinates and regulates motor output—
modification system—not an initiation system!
* VITAL for rapid, sequential, alternating, fine skilled
movement
* Receives input from
* Sensory cortex; Brainstem; Spinal cord;
**Extrapyramidal
* Can compare efferent (motor) commands w/ sensory
feedback
Cerebellum
* Involved in
Involved in ongoing, targeted motor programs
* Body position, equilibrium
* Muscle preparedness, tone
* Distance to target and duration of movement
* Corrective feedback, if required
* Ascending
* Descending
Cerebellum
* Sends modifications
Sends modifications to either motor cortex or to Lower
Motor Neurons (LMNs)
* Can increase/decrease rate of movement OR stop
movement
* Mediates muscle tone, range and strength of motion
* Maintenance of equilibrium
* Unconscious motor learning (works with Basal Ganglia)—
creation of new motor programs
Cerebellar Damage
Difficulty controlling body parts in context of relatively
normal muscle tone and strength
* Particularly evident during activities requiring rapid,
alternating movements
* Cerebellar Function Tests (Assessments)
* _________________
* Diadochokinesis (DDK)
* Cerebellar lesions produce ipsilateral symptoms
* May result from CVA, toxicity, or degenerative disorder
(e.g., Friedreich’s ataxia)
Ataxia
difficulty coordinating series of movements in space
and time
Ataxic dysarthria
difficulty sequencing movements for speech
(bilateral cerebellar damage)-slurring, imprecise articulation
Dysdiadochokineses
failure of sequential progression of
movements
Dysmetria
Difficulty accurately gauging appropriate range of
movement or distance to targe
Disequilibrium
impaired vestibular function—dizziness, body
wavers toward side of lesion (appear ‘drunk’)
floppiness of muscle/flaccidity
