Netter’s Neuroscience Flash Cards by David L. Felten

Overview of the Nervous System 1-6
Synaptic Morphology
A. Schematic of synaptic endings
B. Enlarged section of bouton
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Overview of the Nervous System 1-7
Conduction Velocity
A. Myelinated fibers
B. Unmyelinated fibers
Impulse
 

























































































 


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Conduction Velocity
Overview of the Nervous System See book 1.15
1. Node (site of action potential reinitiation)
2. Nodes of Ranvier
3. Myelin sheath
4. Axolemma
5. Axoplasm
Comment: An action potential is triggered in a neuronal cell
membrane when sufficient depolarization has occurred to allow
the influx of sodium ions to overwhelm the capacity of the efflux of
potassium ions to counter the influx of positive charge. This results in
an explosive depolarization that moves the neuronal cell membrane
toward its sodium equilibrium potential (approximately +55 mV). An
action potential at one node exerts enough local influence on the
adjacent node (and perhaps several distant nodes) to bring those
sites to a depolarized state sufficient to trigger an action potential.
This process reinitiates the action potential at each node. If a local
anesthetic is used to block the excitability (capacity to depolarize)
at several successive nodes, then a conduction block will occur
and propagation of the action potential will cease. The conduction
velocity of an axon depends upon the axonal diameter, also a
reflection of the extent of myelination.

Overview of the Nervous System 1-8
Foramina in the Base of
the Adult Skull
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Regional Neuroscience 2-32
Innervation of the Heart
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2 1
Sympathetic
fibers
Postganglionic
Preganglionic
Postganglionic
Parasympathetic fibers
Afferent fibers
Afferent fibers
Preganglionic

Innervation of the Heart
Regional Neuroscience See book 9.52
1. Nucleus of the solitary tract
2. Dorsal vagal nucleus
3. Superior cervical sympathetic trunk ganglion
4. Middle cervical sympathetic trunk ganglion
5. Cervicothoracic (stellate) ganglion
6. Thoracic vagal cardiac branch
7. Cardiac plexus
8. Thoracic sympathetic cardiac nerves
9. Vagus nerves (CN X)
10. Superior cervical vagal cardiac branches
11. Inferior cervical vagal cardiac branches
Comment: Both sympathetic postganglionic noradrenergic and
parasympathetic postganglionic cholinergic nerve fibers innervate
the heart, including the atria, ventricles, sinoatrial node, and the
atrioventricular node and bundle. Sympathetic nerves also distribute
along the great vessels and coronary artery. Sympathetic fibers
increase the force and rate of cardiac contraction, increase cardiac
output, and dilate the coronary arteries. Parasympathetic fibers
decrease the force and rate of cardiac contraction and decrease
cardiac output. Vagal nerve damage may result in sustained
tachycardia. Excessive vagal activity can provoke bradycardia, atrial
fibrillation or flutter, ventricular fibrillation, or paroxysmal tachycardia.
Sympathetic nerve damage results in severe exercise intolerance,
painless myocardial ischemia, possible cardiomyopathy, and on
occasion sudden death.

Regional Neuroscience 2-33
Abdominal Nerves and Ganglia
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Regional Neuroscience 2-34
Nerves of the Esophagus
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Anterior view
Posterior view

Systemic Neuroscience 3-15
Vestibular Pathways
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Excitatory endings
Inhibitory endings
Vestibulospinal tracts
Lumbar
spinal
cord
Lower
cervical
spinal
cord

Nystagmus
Systemic Neuroscience See book 14.20
1. Oculomotor neurons to the medial rectus muscle
2. Axon of abducens internuclear neuron
3. Ascending tract of Dieters into medial longitudinal fasciculus
4. Medial and lateral vestibular nuclei
5. Abducens nucleus
6. Oculomotor nerve (CN III)
7. Lateral rectus muscle
8. Medial rectus muscle
9. Parapontine reticular formation (PPRF)
10. Abducens nerve (CN VI)
Comment: Nystagmus is the repetitive, alternating, back-and-
forth movement of the eyes, using circuitry to centrally coordinate
extraocular lower motor neurons (LMNs). Vestibular inputs and
cortical inputs regulate the control of the lateral rectus muscle on
one side with the medial rectus on the other side, resulting in the
coordinated movement of the eyes to maintain binocular vision.
Disruption of this process results in vestibular nystagmus, in which a
vestibular disruption (asymmetrical vestibular input) leaves neuronal
imbalance that is interpreted as movement that requires repetitive
readjustment (rapid phase, saccadic movement) to the coordinated
drifting of the eyes (slow phase). In optokinetic nystagmus, a normal
process, tracking movements of the eyes (e.g., to passing telephone
poles while riding in a car) reaches the lateral limit of eye movement,
eliciting a snap-back to the normal forward position of the eyes
via signals from the association visual cortex through the superior
colliculus to extraocular LMNs.

Systemic Neuroscience 3-17
Anatomy of the Eye
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Magnetic Resonance Venography
Overview of the Nervous System See book 7.27
1. Superior sagittal sinus
2. Transverse sinus
3. Sigmoid sinus
4. Internal jugular vein
5. Cerebral veins
6. Internal cerebral vein
7. Great cerebral vein of Galen
8. Basal vein of Rosenthal
9. Straight sinus
10. Confluence of sinuses
Comment: Magnetic resonance (MR) venography uses the same
principles of flow as MR angiography, taking advantage of the
relatively slow and steady venous blood flow compared with the
more robust flow of cerebral arterial blood. MR venography has
largely replaced imaging of venous drainage with radiopaque
contrast agents from carotid arteriography (venous phase).

Overview of the Nervous System 1-52
Neurulation
Level of section
Level of section
Level of section
Embryo at 20 days
(dorsal view)
Embryo at 21 days
(dorsal view)
2.3 mm2.0 mm
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Neurulation
Overview of the Nervous System See book 8.2
1. Neural plate of forebrain
2. Neural groove
3. Neural folds
4. Future neural crest
5. Neural plate
6. Fused neural folds
7. Caudal neuropore
8. Neural crest
Comment: The neural plate invaginates and forms the neural
tube as the two margins of the neural folds fuse. This process of
neurulation starts centrally and moves both caudally and rostrally.
If the neural folds fail to fuse properly, dysraphic effects are seen
that involve altered development of associated muscles, bone,
skin, and meninges. The failure of the caudal neuropore to close
results in spina bifida, with failure of vertebral arches to fuse and
possible protrusion of meninges and neural tissues, exposing them
to the external environment. If the rostral neuropore fails to form,
anencephaly results, a failure of brain development with exposure of
the neural rudiments to the external environment, a lethal condition.

Overview of the Nervous System 1-53
Neural Tube Development and
Neural Crest Formation
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2.6 mm
Level of
section

Regional Neuroscience 2-77
Reticular Formation and Nuclei
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A. Thalamus and hypothalamus
B. Midbrain
C. Pons
D. Medulla
E. Spinal cord–medullary
junction
Thalamus:

Reticular Formation and Nuclei
Regional Neuroscience See book 11.31
1. Intralaminar nuclei
(thalamus)
2. Reticular nucleus of the
thalamus
3. Midline nuclei (thalamus)
4. Lateral reticular formation
of the midbrain
5. Periaqueductal gray
6. Raphe nuclei (dorsal,
central superior)
7. Ventral tegmental area
8. Locus caeruleus
9. Parapontine reticular
formation (PPRF)—lateral
gaze center
10. Raphe nuclei (pontis)
11. Pontine reticular formation
(pontis caudalis, oralis)
12. Lateral reticular formation
13. Medullary reticular
formation (gigantocellularis)
14. Respiratory nuclei
15. Rostral ventrolateral
medulla (RVLM)
16. Raphe nuclei (obscurus,
pallidus, magnus)
17. Group A1
18. Lamina 7—caudal reticular
formation (RF)
Comment: The RF is the neuronal core of the brain stem, extending
from the rostral spinal cord through the hypothalamus and septal
region; RF neurons are large cells with axonal arborizations that
terminate a distance from their cell bodies and dendritic trees
(isodendritic). RF neurons are in a lateral zone (predominantly
sensory functions), a medial zone (predominantly motor functions
for tone and posture), a column of midline and lateral serotonergic
neurons, and clusters of noradrenergic neurons. These two lateral
groups of neurons exert modulatory influences on CXIS targets. The
sensory zone of the RF is the ascending reticular activation system
(ARAS); it receives multiple sensory inputs, activates the cortex
through nonspecific thalamic nuclei, and participates in arousal,
alertness, and consciousness. Consciousness requires intact ARAS
and at least one functioning hemisphere. The medial motor portion of
the RF consists of the pontine and medullary reticulospinal systems
(upper motor neurons) and paramedian nuclei such as the PPRF
(lateral gaze center).

Regional Neuroscience 2-78
Sleep-Wakefulness Control
From
retina
Spinal cord
Sensory
input
Sensory input
Thalamus
Locus
coeruleus
Sympathetic chain ganglia
To pineal
(melatonin)
Reticular formation
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Areas associated with arousal
Areas associated with the
induction of sleep

Sleep-Wakefulness Control
Regional Neuroscience See book 11.33
1. Nucleus basalis (cholinergic)
2. Preoptic hypothalamic area
3. Interleukins, other blood-borne substances
4. Suprachiasmatic nucleus
5. Raphe nuclei
6. Nucleus solitarius
7. Area postrema
8. Reticular formation
9. Locus coeruleus
10. Thalamus
Comment: Sleep is a normal physiological state involving a cyclic
temporary loss of consciousness, readily reversed by sensory
stimuli. Sleep is an active process initiated by brain activity in several
regions, including the locus coeruleus, the raphe nuclei of the
medulla and pons, nucleus solitarius, cholinergic neurons of the brain
stem tegmentum, the lateral reticular formation (particularly the pons),
several regions of the hypothalamus, and the reticular nucleus of the
thalamus. Many of these regions actively inhibit the lateral sensory
portion of the reticular formation that normally maintains wakefulness
and consciousness. Circulating substances such as interleukin-1 can
act on sites in the hypothalamus to induce sleepiness (a component
of illness behavior). Slow wave sleep that does not involve rapid
eye movement (REM) is initiated by hypothalamic neurons and is
accompanied by decreased activity in the locus coeruleus and the
cholinergic tegmental neurons. During REM sleep, activity in the
noradrenergic locus coeruleus and the serotonergic raphe neurons
greatly diminishes, preventing the cerebral cortex from attending
to external stimuli. Dreams probably occur because the cortex is
attending to internal stimuli provided by stored memories.

Regional Neuroscience 2-79
Cerebellar Organization:
Lobes and Regions
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“Unfolded” schematic of
cerebellum demonstrating
body map areas
“Unfolded” schematic of cerebellum demonstrating regions and lobes
Lobes
Regions

Bony Framework of the Head
and Neck
Overview of the Nervous System See book 2.3
1. Atlas (C1)
2. Axis (C2)
3. C3 vertebra
4. C7 vertebra
5. Mandible
6. Zygomatic arch
7. Sphenoid bone
8. Temporal bone
Comment: The cervical vertebrae are well articulated with each
other and provide a strong bony framework for protecting the spinal
cord as it emerges from the brain stem. But the sites of articulation
and the vertebrae themselves are sites of potential vulnerability to
trauma and can be fractured or dislocated, causing spinal cord
injury. Cervical discs may herniate, resulting in prot