Download Nolte – Chapter 3 (Gross Anatomy and General

Nolte – Chapter 3 (Gross Anatomy and General Organization of the Central
Nervous System and Peripheral Nervous System) and all Class-Notes and LabNotes tagged with Chapter 3.
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Dorsal-Ventral all throughout CNS
o The cephalic flexure would spate the axes, but we keep the
terminology as if it was the same.
 Cephalic flexure visible at the junction between the brainstem
and the diencephalon.
Corpus collosum
o Splenium at posterior
o Body
o Genu at anterior
 Goes a bit ventral to the rostrum.
A particularly deep sulci is a fissure
Lobe and section markers
o Frontal lobe
 Anterior limit: None
 Ventral Limit: Separated from the temporal lobe by the lateral
sulcus (sylvian fissure)
 Most ventral region is the orbital part.
 Ventral Limit(Medial): On the medial surface extends to the
cingulate sulcus (but doesn’t include)
 Posterior Limit (Medial): imaginary continuation of the central
sulcus to the cingulate.
o Parietal Lobe
 Anterior Limit: Central Sulcus
 Posterior Limit: Imaginary line connecting the top of the
parieto occipital sulcus and the preoccipital notch.
 Ventral Limit: as if the calcarine and sylvian connected.
 Vental Limit(Medial): subparietal and calcarine sulci
 Posterior limit (medial) parietooccipital sulcus.
o Temporal Lobe
 Dorsal Limit: Sylvian Fissure extension to calcarine
 Posterior Limit: line connecting top of the parietooccipital
notch and the preoccipital notch.
 Posterior Limit(Medial): imaginary line from preoccipital
notch to the splenium.
 Dorsal Limit (Medial): Collateral Sulcus.
o Occipital Lobe
 Anterior Limit: parietal and temporal lobes on both medial and
lateral and surface.
o Limbic Lobe
 Encircles the telencephalon-diencephalon junction.
 Interposed between corpus collosum and rest of cortical lobes.
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The operculum covers the insula
o Made up of frontal, parietal and temporal.
o Circular sulcus outlines the insula and marks it borders with the
opercula.
Gross Function/Anatomy
o Precentral and forward is motor.
o Post central and back is sensory.
o IFG is split into 3
 Oribital(anterior), triangular(middle), opercular(posterior up
to the precentral gyrus).
 Brocas is in Orbital and triangular.
o Gyrus rectus
 The medulla part of the frontal lob just medial to olfactory bulb
 On the other side of the olfactory bulb(siting in its
sulcus) st the orbital gyrus extension.
o Parietal Lobe
 Somatosensory
 Postcerntral sulcus
 Superior parietal Lobule
 Intraparietal sulcus runs from the postcentral gyrus to
the parietooccipital sulcus to separate it from the
inferior parietal lobule.
 Inferior parietal lobule
 Made up of supramarginal gyrus(anterior up to the
postcentral gyrus) and angular gyrus(rest)
 Supramarginal caps the lateral fissure.
 Angular caps the superior temporal gyrus.
 Medial
 Back to the parietoccipital sulcus is the precuneus and
bounded ventrally by the calcarine.
 All that is left after precuneus is the posterior
paracentral lobule.
 These two are separated by the cingulate sulcus.
o Temporal Lobe
 Superior Temporal gyrus
 Primary auditory cortex
 Wernicke’s area is the posterior most portion of this.
 Wraps around in the anterior portion a bit to the medial
 Medial side
 Fusiform is most dorsal
o Separated by the occipitotemporal sulcus from
the inferior temporal sulcus
o Occipital
 ParietoOccippital and calcarine corner off the cuneus.
 Just inferior to that calcarine sulcus is the lingual gyrus.
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Most inferior is the fusiform gyrus
Lateral Side is all “lateral occipital gyri”
V1 is contained in the walls of the calcarine sulcus
 Rest of the lobe is “visual association”
o Limbic
 Cingulate and parahippocampal
 Cingulate is on top of diencephalon
 After it hooks around the genu we see the subcollasal
area cap off the cingulate gyrus.
 Parahippocampal is below.
 Anterior end that hooks back is the uncus.
o Amygdala lies beneath the uncus and the
hippocampus follows posteriorly.
 Superior to it we see the hippocampal sulcus
Diencephalon
o Thalamus has the third ventricle as a roof(their meeting point is the
stria medullaris)
o The medial surfaces are fused by the massa intermedia
o Hypothalamic sulcus seperates the thalamus from the more inferior
hypothalamus.
o Hypothalamus connectes with the pituitary by the infundibular stalk.
o More inferior are the mammillary bodies.
 SCN takes 10% of retinal input
 Right on top of optic chiasm
o On the dorsal side, right above the superior colliculi, we find the
pineal gland.
Midbrain
o The tectum goes over the cerebral aqueduct and is made up of the
collulculi and the brachium of the inferior.
o The cerebral peduncles
o Red nuclei
 Rubrospinal tract starter
 Important motor nuclei for cerebellum
Pons
o Pontine tegmentum forms floor of the fourth ventricle.
Medulla
o Rostral open, caudal closed.
o Medullary pyramids are just below the basal pons.
 Decussate at region of medulla to the spinal cord.
Cerebellum
o Vermis – midline
 Lateral hemisphere encapsulating it
o Anterior lobe
 Separated by the primary fissure.
 Afferent inputs from spinal cord
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o Flocculonodular lobe
 Nodulus(vermal portion), flocculus(vestibulocochlear nerve)
 Afferents from vestibular
o Posterior love
 Largest
 Gets relay from pontine nuclei.
 Coordination of voluntary movements.
Hippocampus
o Efferent fiber bundle: fornix
o Folded into the termporal lobe forming part of the wall of the alteral
ventricle.
o Becomes smaller as the temporal lobe curves into the parietal lobe.
 Ends near the splenium of the CC
o Fornix ends in the mammillary bodies.
Basal Ganglia
o Lenticular nucleus
 Putamen and globus pallidus
o Caudate
 Head in frontal lobe
 Body and tail that follow the lateral ventricle around into the
temporal lobe
 Sepearted from the lenticular by the internal capsule which
interconnects cerebrum with basal ganglia processes and
thalamus
Relevant Cranial Nerves
o II goes into the chiasm and becomes the tract
 Only one that projects directly into the
diencephalon(remember retina is actually part of
diencephalon)
o III emerges from the interpeduncular fossa between the cerebral
peduncles.
 This is just below the mammilarry bodies
 The infundibulum is superior to mammillary bodies.
o IV the only to emerge from the dorsal side
 Just caudal to the inferior colliculi
o V emerges from the lateral portion of the basal pons.
Miscellaneous
o Thalamocortical fibers are uncrossed
o Cerebellum is ipsilateral
o Spinothalamic is pain-temperature
o Cerebellar outputs return to the motor cortex and affect corticospinal
activite (but go through thalamus)
 Must cross midline before thalamus.
 Basal ganglia also affect motor output this way.
 They don’t receive sensory input as directly, though.
o Layer IV receives sensory input
 If this layer is tiny, then its probably not a sensory based cortex
o Layer V is output (pyramidals)
 Go down through the peduncles and medulla(decussate) and
go down the spinal cord to contact primary motor neurons
 This is the coricospinal tracts
o Layer VI receives input from thalamus
Peripheral Nervous System
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Peripheral nerves do not cross the midline
Afferent
o Go towards the CNS
o Primary afferents in the dorsal root ganglia hug the spinal cord
 These are psudounipolar
Efferent
o Fibers that go away
o Cell bodies reside inside the gray matter
Dorsal-Ventral
o Bell-Magendie Law
 Sensory axons enter the dorsal root
 But not limbo-sacral pain fibers
 Motor axons exit via the ventral root
Plexi
o Organized web of fibers like a tree branch that get more and more
focal as you get closer to innervations.
 E.g: brachial plexus will cover everything in the arms.
Peripheral Nerves and Conduction
o Ia are primary muscle spindle afferents
o Ib are golgi tendon organ afferents
o II are spindle secondaries
 Meissner, merkel, etc.
o III are free nerve endings for temperature and sharp pain
o IV(c) are free nerve endings as well
 Unmyelinated
 Slow pain
o Reception depends on intensity and duration
 pacininian can absorb initial energy and adapt quickly, so
vibration would be something that would get it to fire.
o Receptor type depends on location and quality
 homonculus
o Extrinsic mechanism can affect reception as well
 bright light can be received but can also trigger a contraction of
the pupil.
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intrafusal and extrafusal efferents can made more and less
sensitive.
Glia
o Schwann
 Wrap around the axon in an engulfing fashion
 also provide metabolic support
 especially in dorsal root ganglia
 they can make a type of matrix and rovide scaffolding for
axonal growth after injury.
Muscle Spindles
o receptor organs that lie in parallel to our muscle fibers
o tell us about the length of our muscle and the rate of change of this
muscle
o nuclear chain fibers and their flower outbranches respond primarily
to length and will fire when the muscle is lengthened.
o nuclear bag fibers with their annulospiral endings will to the rate of
change
o Gamma motor neurons will regulate the sensitivity to stretch when
muscle is relaxed.
 allows the nucleur bag to stay tense
Golgi tendon organs are between the muscle and tendon and will be
activated by isometric contractions.
o respond to tension
o slow adapting, so they can keep up the maintenance.
Autonomic Nervous System
o nerves that go to our viscera
o all the efferents go through a ganglia
o Sympathetic
 flight or fight
 efferents comes out of ventral horn
 B type fibers will synapse near the sympathetic
ganglion with acetylcholine and then innervate with
norepinephrine.
o except for sweat glands which are cholinergic.
o preganglionic can also innervate the adrenal
medulla that then secretes norep.
 the sympathetic ganglion are near the spinal cord
 and primarily in thoracic and upper lumbar
o thoracolumbar outflow.
 can be interconnected to form a sympathetic chain.
 travel from spinal cord to the sympathetic chain ganglion via
the white communicating rami
o Parasympathetic
 more normal
 Ganglion are closer to the vicera of interest
use acetylcholine on parasympathetic ganglia and the actual
viscera.
 mainly in sacral spinal nerves and cranial nerves
 none in the limbs
 more focal in its control than the sympathetic.
o There is always a stop at autonomic ganglia(post ganglionic)
 the preganglionic has its cell body in the CNS and are thinly
myelinated in route to the ganglia.
 the actual postgalionic innervations are unmyelinated.
 this is different from the somatic motor system where we just
have the cell body in CNS whose axons go directly to skeletal
muscle.
Injuries
o damage to a nerve causes willerian degeneration, where neurons
distal to the cut will start to die and the axon will regress to the
closest node of ranvier.
 the schwann cells will remain, though, as scaffolding.
o Collateral sprouting can occur from preserved tips f axons
 they can follow the NGF given off by schwann cells and
simultaneously grow through the schwann scaffolding.
Pain
o Nociceptive.
 hurt ow.
o Neuropathic
 dull aching (due to damage of neural tissue)
o Free nerve endings release potassium and other chemical mediators
o C fibers
 slow conduction(no myelinated)
 2nd pain
o A-delta Fibers III
 fast conducting
 1st pain
o Gate-Theory
 incoming pain stimuli can be regulated because the incoming
stimuli compete with sensory inputs and cortical modulations.
 we rub periphery so that the signal can compete
 touch will be faster than the slow transmitting c fibers,
so we keep touching and rubbing to overpower the slow
pain.
o Referred pain
 the area to which pain is referred correspond to the
dermatome innervated by the spinal segment to which the
visceral afferent project.
 visceral afferent fibers accompany sympathetic
efferents
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o subserve visceral reflexes and don’t really reach
consciousness but can if it is enough or if the
organ is inflamed.