Neurology Organization and Contol Flashcards
structural division of nervous system
- CNS
2. PNS
CNS
brain and spinal cord
processing center, main control center
housed by axial skeleton
PNS
nerves outside the CNS (everything but)
relays information to and from the CNS to various endpoints in the body
Functional breakdown of nervous system
- somatic nervous system
2. autonomic nervous system
somatic nervous system
provides sensory and motor innervation
controls voluntary movement
skeletal muscle (excludes viscera, smooth muscle, glands)
autonomic nervous system
provides motor innervation to the smooth muscle, conduction of the heart, glands
without conscious thought
divided into: Parasympathetic and Sympathetic
3 parts of a neuron
- axon
- dendrite
- cell body
2 types of neurons
afferent
efferent
afferent nerve
SENSORY
carries information from skin/peripheral to the CNS
efferent nerve
MOTOR
carries information from the CNS to the muscle
Types of supporting cells
- schwann cell
- oligodendrocytes
- astrocytes
- ependymal cells
- microglial cells
energy requirements of nervous system
requires 15% of cardiac output , 20% of O2 consumption
obligate aerobic (can’t store oxygen so requires continues supply of O2 from blood – only lasts about 10 sec w/o before death)
Glucose is source of energy – can’t store so also gets it from the blood
energy source of the brain
GLUCOSE
3 meningeal layers
- dura mater
- arachnoid mater
- pia mater
Dura mater
pain sensitive
two layers: edosteum (attached to the skull) and meningeal (has potential space where it separates from arachnoid mater for dural venal sinuses)
arachnoid mater
web of supportive collagen
acts as a shock absorber to prevent trauma
contains subarachnoid space
subarachnoid space
exists between pia and arachnoid mater
collection of cerebral vasculature and CSF cisterns
site of hemorrhage
pia mater
most inner meninge
covers every surface of the cerebrum
Subarachnoid hemorrhage
symptoms:
workup:
treatment:
symptoms: sudden, “worst HA of life”
workup: non contrast CT - will show blood, lumbar puncture with Xianthrochromia
treatment: neurosurgical intervention to stop bleeding, high mortality if not identified
Action potential
- resting membrane potential: polarized but no activity
- depolarization: influx of sodium ions that generate rapid electrical impulse
- repolarization: Na+ channels close, K+ channels open, efflux of K+ causes the potential to decrease back to resting
- — can’t be depolarized during this time
which cells produce myelin
schwann cells (PNS) oligodendrocytes (CNS)
benefits of myelin
speeds up conduction
protects axon
astrocytes
largest and most numerous
fills intracellular space
tightens the BBB
regulates ionic concentrations and synaptic activity
repairs and scar formation
microglia
phagocytes
cleans up debris
ependymal cells
line the ventricular system
combines with vascular network to form choroid plexus
forms a very selective barrier (causes CSF to be sterile)
choroid plexus fxn
formation of CSF
disorders of the myelin sheath
guillain-barre
multiple sclerosis
Guillan Barre
peripheral nervous system
attacks schwann cells
progressive paralysis from limbs towards center
only attacks the myelin sheath so it can recover
Multiple Sclerosis
central nervous system (oligodendrocytes)
can attack either the whole axon or just the sheath (relapsing/remitting)
BBB
blood brain barrier
separates blood from brain parenchyma
tight jxn so only lipid soluble can pass
2 methods of neuronal communication
electrical synapse
chemical synapse
electrical synapse
gap jxns b/t cells
allow action potential to move from cell to cell
chemical synapse
neurochemicals are released from the presynaptic structure and travel thru synaptic clef and interact with postsynaptic receptors on another neuron
excite or inhibit
Neurotransmitters
GABA glutamate serotonin dopamin norepinephrine epinephrine
GABA
mediates most synaptic inhibition
increases the threshold (harder to excite)
ex. of drugs that work on GABA receptors are barbiturates and benzodiazopine
glutamate
NT that mediates most synaptic excitation
lowers the threshold so it is easier to generate action potential
blood supply to anterior cerebrum
internal carotid
arises from common carotid
bifurcates into anterior cerebral and middle cerebral arteries
common place for ischemia in the brain?
middle cerebral arteries
emboli often lodge here
blood supply to posterior cerebrum
vertebral arteries
arise from subclavian
forms basilar artery–> posterior cerebral arteries
supplies brainstem, cerebellum, occipital lobes, temporal lobes, thalamus
circle of willis
anastomosis that connects the anterior and posterior circulations of the brain via communicating arteries to allow for collateral blood flow
circle of willis advantage
minimizes damage of ischemia by allowing oxygenated blood to flow in other paths to affected tissues
Sequelae of the middle cerebral artery
fine manipulative skills of face and upper limbs to receptive and expressive communication
aphasia when there is an emboli
where does the spinal cord end?
L2
at the conus medullar is
how many pairs of spinal nerves?
32
8 cervical 12 thoracic 5 lumbar 5 sacral 2 coccygeal
clinical presentation of complete cord transection syndrome
dependent on level of transection
will have numbness and loss of all sensory modalities, weakness and paralysis below effected level, bladder dysfunction
transection of spinal cord at upper cervical level
- quadriplegia (paralysis of 4 limbs)
- areflexia of upper and lower extremities
- anesthesia below transection level
- loss of sphincter control, urinary and bowl retention
injuries above which level involve cessation of respiration?
C3
neurogenic shock
hypothermia and hypotension
(low temp and low blood pressure)
more likely to occur when transection is at higher levels on SC
attempt to stabilize breathing and blood pressure to prevent
transection at thoracic level
- paraplegia (loss of lower limbs)
- anesthesia of lower limb
- areflexia of lower quadrant
- urinary, bowel retention and loss of sphincter control
spares respiratory muscles so less likely to have neurogenic shock
Cauda Equina syndrome
symptoms
asymmetric pain, leg weakness, sensory loss, bladder/bowel dysfunction, saddle anesthesia, decreased DTR in LE back pain
cauda equina syndrome
cause and diagnosis
compression of the caudal nerves, i.e. trauma, disc herniation, lesions, lumbar stenosis
diagnosis: imaging (CT/MRI)
cauda equina syndrome
treatmetn
surgical decompression to relieve compression
