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
