General Neuropathology Flashcards
Involuntary actions
maintain homeostasis
Regulated by ANS
Voluntary actions
Reflex activities
Meninges: Dura Mater
Outer layer
Meninges: Arachnoid
Middle layer
Subarachnoid space
Contains cerebrospinal fluid (CSF)
Meninges: Pia mater
Adheres to surface of brain
Meninges other parts
Subdural space
Arachnoid
Protection of the Brain
BBB
Blood-brain barrier Role (LCL)
Limits passage
Controls balance of electrolytes, glucose, and proteins in brain
Lipid-soluble substances pass easily
BBB and neonates
Poorly developed in neonates
Blood-CSF barrier
At the choroid plexus for CSF
Each hemisphere is divided into four major lobes.
Frontal
parietal
temporal
occipital
Longitudinal fissure
separates two hemispheres
Cortex
“Gray matter” – nerve cell bodies
Corpus callosum
“White matter” – myelinated nerve bundles (tracts)
Connect the hemispheres
Right and left hemispheres similar in
structure, not necessarily in function
Dominant hemisphere
Side of brain that controls language
Dominant hemisphere- in most people
Left hemisphere
Broca area
Motor speech
Wernicke area
comprehends language
Functional Areas – Diencephalon
Central portion of the brain
Functional Areas – Diencephalon contains what?
Contains the thalamus and hypothalamus
Functional Area - Diencephalon - Thalamus role
Relay station for incoming sensory impulses
Hypothalamus
Key role
What does it control?
Key role in maintaining homeostasis of the body
Controls autonomic nervous system and much of the
endocrine system
Hypothalamus regulates (BRESS F)
Body temperature, Regulation of sleep cycles Emotional responses Sex drive Stress response, Fluid and food intake,
Functional Areas – Brainstem 3 parts
Midbrain
Pons
Medulla oblongata
RAS
Functional Areas – Brainstem- Midbrain
Visual activities
Functional Areas – Brainstem- Pons (HS)
Helps regulate respiration
Several nuclei of cranial nerves
Functional Areas – Brainstem- Medulla oblongata (CCN)
Control center for respiratory and cardiovascular
function
Coordination of cough reflex, swallowing, vomiting
Nuclei for several cranial nerves
RAS (Reticular-Activating System)/Reticular formation
Network of nuclei and neurons throughout brainstem
RAS and connection
Connected to many parts of the brain
Determines the degree of awareness of the cerebral cortex
*Anesthetic drugs and RAS
inhibit RAS causing reversible loss of consciousness
Cerebellum Role
Coordination of movements
Maintenance of posture & equilibrium
Cerebellum receives input from
Receives input from proprioceptors in muscles &
joints
Input from visual and vestibular pathways
Cranial Nerves: How many pairs and where does it originates?
12 Pairs
Originate from various parts of the brain
Cranial nerve numbered how?
Numbered from ventral to dorsal
Cranial nerves may contain
–Motor only
–Sensory only
–Both (mixed)
Spinal Cord is protected by
Protected by vertebral column, meninges, CSF
Spinal Cord continuous with
Continuous with medulla
Where does the SC end?
Ends at lower border of L1-L2
Conus medullaris, cauda Equina
White and gray matter
Core
Posterior horns
Interneurons (association neurons)
Anterior horns
Cell bodies of motor neurons
Spinal nerves named by
Named by location in the vertebral column where
they emerge
Nerve Roots Ventral anterior root
Motor (efferent) fibers (VME)
Dorsal (posterior) root
Sensory (afferent) fibers (DSA)
What are reflexes?
Automatic, rapid, involuntary responses to a
stimulus
Sensory stimulus, what is it?
From receptor – conducted along afferent fiber
What is a Synapse?
In the spinal cord or for cranial reflexes in the brain
Efferent impulse serve to
to elicit the response
Connecting and interneurons
Transmit sensory information to the brain
Neurotransmitters; ACh
Excitatory @ NMJ
ACH found in
In ANS and brain
Neurotransmitters Epi & Norepi ? Found where?
Excitatory
Brain and Sympathetic Nervous System
Neurotransmitters: Dopamine, serotonin? Found where?
Excitatory
Brain
Neurotransmitters GABA
(inhibitory)
Brain
Sympathetic & Parasympathetic Branches
Motor and sensory innervation
Involuntary
Preganglionic fibers are found where?
In brain or spinal cord
Postganglionic fibers are found where?
Outside the CNS
Sympathetic Nervous System
“Fight-or-flight” response
Increases general level of activity in the body
Preganglionic fibers arise from
thoracic and first two lumbar segments.
SNS Ganglia located in
chains or trunks
***SNS Neurotransmitters
Preganglionic
Postganglionic
acetylcholine
norepinephrine
SNS Receptors
Alpha and beta receptors
Parasympathetic Nervous System
Originates
in the brainstem and sacral spinal
nerves
Parasympathetic Dominates
digestive system and aids recovery after sympathetic activity
Parasympathetic NS Ganglia
scattered and close to target organ
**Parasympathetic Neurotransmitter release (pre and pos synaptics)
both presynaptic and postsynaptic releases Acetylcholine
ACH Receptors
Nicotinic and muscarinic
Autonomic Hyperreflexia ocurs
Occurs with spinal cord injury at or above T6.
In autonomic Hyperreflexia Pathophysiology
SEBBB
Strong sensory input (ex. from full bladder) sends signal up S.C. –
Evokes massive reflex sympathetic surge resulting in vasoconstriction and severe hypertension. Baroreceptors send signal to Brain.
Brain sends inhibitory signals, which are blocked by the injury.
Brain also sends Vagus N. signal = ↓ HR, however, the bradycardia fails to control the HTN.
Autonomic Hyperreflexia Can be triggered by
visceral (bladder/bowel) or cutaneous stimulation (ex. Surgical incision).
% of patient developing autonomic hyperreflexia
85% of pts with injury above T6 will develop it.
Autonomic hyperreflexia Unlikely to occur at all in
patients with lesion below T10.
Autonomic Hyperreflexia Symptoms in awake patient: BSN
Blurred Vision
Severe HA
Nasal Stuffiness (due to reactive cutaneous vasodilation above level of injury)
Autonomic Hyperreflexia
Most likely to occur intra-op. at beginning of case with
initial surgical incision and/or at end of case as anesthetics are wearing off.
Treatment of Autonomic Hyperreflexia
Vasodilators with a short half-life (such as sodium nitroprusside)
CSF Provides
cushion for brain and spinal cord
CSF is Formed by
choroid plexuses in the ventricles
CSF Flows through
ventricles into subarachnoid space
Equal amounts of CSF need to
be produced and reabsorbed to maintain intracranial pressure (ICP)
Normal CSF production in adults is about
21 mL/hour or 500ml /day.
The total volume at any given time, however, is only about
150 mL.
CSF flow pattern
◘from lateral ventricles to 3rd ventricle via
foramen of Monroe, then passes into 4th ventricle via
aqueduct of Sylvius.
◘Then passes from 4th ventricle to cerebellomedullary
cistern via the foramen of Magendie.
◘From the cerebellomedullary cistern, it enters the
subarachnoid space, circulates around the brain and
spinal cord, and then is reabsorbed in the arachnoid
villi (“granulations”) above the cerebral hemispheres