Lecture 14 (3/24) Flashcards Preview

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Flashcards in Lecture 14 (3/24) Deck (19):
1

Fibers/Tracts (Overview)

There are millions and millions of axons that band together in their travels

Can travel in ascending/descending, left/right, and front/back

Bundles of axons that travel together in the CNS are called TRACTS

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Projection Fibers

Fibers that connect widely spaced regions in the CNS

Long distance carriers

They carry info from the cortex to the brain stem and spinal cord
-includes descending tracts and peripheral fibers that travel to the brain via the spinal cord

Two Types:
Afferent
Efferent

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Afferent Projection Fibers

Carry sensory info from receptors found in the PNS and take that info to the brain

Ascending

Have 3 stations on their way to the cortex:
First Order Neurons (ganglion)
Second Order Neurons
Third Order Neurons

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First Order Neurons

One of three stations afferent projection fibers stop at on their way to the cortex

Cells in the ganglion connect to receptors in the PNS

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Second Order Neurons

One of three stations afferent projection fibers stop at on their way to the cortex

Cells in the ganglion connect the cells in the spinal cord where they synapse with receptors

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Third Order Neurons

One of three stations afferent projection fibers stop at on their way to the cortex

Found in the thalamus

Upon receiving the info the first order neurons carry the info to the cortex via the internal capsule and the corona radiata

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Internal Capsule

Helps the third order neurons relay sensory information to the cortex

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Corona Radiata

Helps the third order neurons relay sensory information to the cortex

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Efferent Projection Fibers

Projection fibers that carry command and control (motor) signals from the brain to the muscles and glands

Originate in the motor cortex and the premotor cortex and travels all the way down to the spinal cord and muscles

Ex. Cortical spinal tract

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Commissural Fibers

AKA Commissures

Fibers that cross the midline and provide communicative links to the two hemispheres

Three types:
Corpus Callosum
Anterior Commissure
Posterior Commissure

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Corpus Callosum

Largest of the Commissures

Primary communicative link between the two hemispheres

Damage here would prevent information from traveling between the hemispheres. Causes a collection symptoms called Split-Brain Syndrome

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Anterior Commissure

A fiber that crosses the midline deep within the brain near the thalamus, near the anterior portion of the corpus callosum

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Posterior Commissure

Crosses the midline near the posterior portion of the corpus callosum

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Association Fibers

Fibers that connect regions within a single hemisphere

Three types:
Uncinate Fasciculus
Cingulum
Arcuate Fasciculus

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Fasciculi

A type of association fiber

Fibers that connect regions that are far apart within a single hemisphere

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Uncinate Fasciculus

An association fiber

Connects the inferior frontal lobe with the temporal lobe in each hemisphere

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Cingulum

An association Fiber

Runs above the corpus callosum and connects deep regions in the frontal and parietal lobes with regions in the temporal lobe and midbrain

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Arcuate Fasciculus

An association fiber

Connects Broca's area with Wernicke's area

Damage here causes a type of aphasia called Conduction Aphasia

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Conduction Aphasia

A type of aphasia caused by damage to the arcuate fasciculus

These patients have good comprehension abilities, but repetition is a problem for them