Neuro Flashcards
Astrocytes
- Most abundant glial cell
- regulate metabolic environment
- repair neuron after neuronal injury
Ependymal cells
Concentrated in roof of 3rd and 4th ventricles & spinal cord
Oligodendrocytes
Form myelin sheath in the CNS
Schwann cells form myelin sheath in PNS
Microglia
Macrophages - phagocytize neuronal debris
Frontal lobe
motor cortex
Parietal lobe
somatic sensory
Occipital lobe
vision cortex
Temporal lobe
auditory
Wernicke’s area - understanding speech
Broca’s area = motor control of speech
Cerebral cortex
cognition, sensation, movement
Hippocampus
memory and learning
Amygdala
emotion, appetite, responds to pain & stressors
Basal ganglia
fine control of movement
Diencephalon
thalamus & hypothalamus
Thalamus
relay station that directs info to cortical structures
Hypothalamus
primary neurohumoral organ
Brainstem
- midbrain
- pons
- medulla
- reticular activating system
Midbrain
auditory and visual tracts
Pons
autonomic integration
Medulla
autonomic integration
Reticular Activating System
controls consciousness, arousal, and sleep
Cerebellum
- Archiocerebellum
- Paleocerebellum
- Neocerebellum
Archeocerebellum
maintains equilibrium
Paleocerebellum
regulates muscle tone
Neocerebellum
coordinates voluntary muscle movement
All cranial nerves are part of the Peripheral Nervous System except…
Optic n.
- only CN surrounded by dura
Bell’s palsy results from an injury to which nerve
Facial (CN VII)
- ipsilateral facial paralysis
Tic douloureux
Trigeminal neuralgia (CN V) - excruciating pain in the face
Eye movement is controlled by which cranial nerves?
CN III, IV, VI
Parasympathetic output is carried out by which cranial nerves?
CN III, VII, IX, and X
- vagus is responsible for 75% of all ParaSNS activity
Where is CSF located?
- Ventricles ( L lateral, R lateral, 3rd and 4th)
- Cisterns around the brain
- Subarachnoid space in the brain and spinal cord
Blood Brain Barrier is not present at…
- chemoreceptor trigger zone
- posterior pituitary gland
- choroid plexus
- parts of the hypothalamus
CSF volume?
150 ml
Specific gracvity?
1.002-1.009
What cells is CSF produced by and at what rate?
- ependymal cells of choroid plexus
- rate of 30 ml/hr
Choroid plexus is located in what cerebral ventricles?
All 4
CSF pressure?
5-15 mmHg
How is CSF reabsorbed into the venous circulation?
via arachnoid villia in the superior sagittal sinus
Global cerebral blood flow
45-55 mL/100g tissue/min
- 15% of CO
Cortical cerebral blood flow
75-80 mL/100g tissue/min
Subcortical cerebral blood flow
20 mL/100g tissue/min
Cerebral Perfusion Pressure autoregulation is abolished by?
- intracranial tumor
- head trauma
- volatile anesthetics
5 determinants of cerebral blood flow
- cerebral metabolic rate for oxygen
- cerebral perfusion pressure
- venous pressure
- PaCO2
- PaO2
Conditions that impair cerebral venous drainage
- jugular compression r/t improper head position
- inc. intrathoracic pressure r/t coughing or PEEP
- vena cava thrombosis
- vena cava syndrome
For every 1 mmHg inc or dec in PaCO2, CBF will inc or dec by what?
1-2 mL/100g brain tissue/min
Cerebral max vasodilation and vasoconstriction occur at what PaCO2 levels?
vasodilation: PaCO2 = 80-100 mmHg
vasoconstriction: PaCO2 = 25 mmHg
Does metabolic acidosis affect CBF?
No - because H+ does not pass through the BBB
- only respiratory acidosis affects CBF
How does PaO2 affect CBF?
- PaO2 < 50-60mmHg causes vasodilation and inc CBF
- PaO2 > 60mmHg does NOT affect CBF
Grey Matter
- contains neuronal bodies
- processes afferent signals from periphery
Laminae I-VI
- dorsal grey matter
- sensory
Laminae VII-IX
- ventral grey matter
- motor
Grey matter is larger in two regions of the spinal cord
- C5-C7 (houses cell bodies for neurons that supply upper extremities)
- L3-S2 (houses cell bodies for neurons that supply lower extremities)
White Matter
- contains axons of ascending and descending tracts
- divided in dorsal, later, ventral columns
Tracts
group of fibers inside white matter in the CNS that relay information up or down the spinal cord
Dorsal column - medial lemniscal system
- transmits mechanoreceptive sensations - fine touch, proprioception, vibration, pressure (fine degree of intensity)
- transmits sensory info faster than anterolateral system
- ascends spinal cord on ipsilateral side
- crosses contralateral side in the medulla and ascends towards thalamus (via medial lemniscus)
- ends in cerebral cortex (postcentral gyrus - parietal lobe)
Anterolateral system - spinothalmic tract
- transmits pain, temp, crude touch, tickle, itch, sexual sensation
- may ascend 1-3 levels on ipsilateral side via lissauer tract
- pain neurons synapse in substantia gelatinosa (laminae I and II)
- crosses contralateral side and ascends via anterior spinothalmic tract and lateral spinothalmic tract
- most tactile signals are relayed to the thalamus and advance towards somatosensory cortex in the postcentral gyrus - parietal lobe
- most pain fibers synapse in the RAS and are then connected to the thalamus
Corticospinal tract
“pyramidal tract” - pyramids are formed by neurons as they run through the medulla
- motor neurons exit precentral gyrus of frontal lobe
Lateral Corticospinal Tract
- fibers innervate limbs
- cross to contralateral side in medulla
- descend via spinal cord via lateral corticospinal tract
Ventral Corticospinal Tract
- fibers innervate axial muscles
- remain on ipsilateral side as they descend via ventral corticospinal tract
- most fibers crossover to contralateral side of spinal cord when they reach the cervical or upper thoracic area
Upper Motor Neuron
- begin in cerebral cortex and end in the ventral horn
Lower Motor Neuron
- begin in ventral horn and end at NMJ
Upper Motor Neuron Injury
- injury above level of decussation in the medulla, paralysis will be on opposite side
- injury below level of decussation in the medulla, paralysis will be on the same side
- manifests as hyperreflexia and spastic paralysis
- Ex upper motor neuron dz: cerebal palsy, ALS
Babinski Sign
- tests integrity of corticospinal tract
- Normal response: firm stimulus to underside of foot produces downward motion of all toes
- Damage: upward extension of big toe and fanning of others
Lower Motor Neuron Injury
- peripheral motor fibers link spinal cord to a muscle
- injury results in paralysis on the same side as injury
- manifests as impaired reflexes and flaccid paralysis
- Babinski sign is absent in lower motor neuron injury
Neurogenic Shock
- hypotension, bradycardia, hypothermia
- pink, warm extremities
- can last 1-3 wks
Autonomic Hyperreflexia
- 85% of pts w/injury above T6
- presentation: HTN and bradycardia
- profound vasoconstriction below level of injury
- activates baroreceptor in carotid bodies & dec HR
- body attempts to dec afterload w/vasodilation above the injury
Amyotrophic Lateral Sclerosis
- progressive degeneration of motor neurons in corcticospinal tract
- affects upper & lower motor neurons
ALS Signs and Symptoms
- upper neuron involvement: spasticity, hyperreflexia, loss of coordination
- begins in hands and spreads to rest of body
- ocular muscles not affects
- sensation remains intact
- resp failure = most common cause of death
- autonomic dysfxn = orthostatic hypotension & resting tachycardia
ALS Management
- Succs can cause lethal hyperkalemia (lower motor neuron dysfxn is associated w/proliferation of postjunctional nicotinic receptors)
- Inc. sensitivity to NDNMB
- bulbar muscle dysfxn and inc. risk pulm aspiration
- chest weakness dec. vital capacity and max min. ventilation
- consider post-op ventilation
