Chapter 12: The Central Nervous System (B)

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Lateralization

each hemisphere of the brain has unique abilities not shared by its partner

Cerebral Dominance

designates the hemisphere that is dominant for language; about 90% of people, the left hemisphere has greater control over language abilities, math, and logic

Cerebral White Matter

second of three basic regions of each cerebral hemisphere; responsible for communication between cerebral areas and between cerebral cortex and lower CNS centers; consists mainly of myelinated fibers bundled into large tracts

Commissural Fibers

type of fiber tract; connect corresponding gray areas of the two hemispheres, enabling them to function as a corrdinated whole; largest commissure is the corpus callosum; run horizontally

Corpus Callosum

type of commissure fiber; lies superior to lateral ventricles, deep within the longitudinal fissure

Anterior and Posterior Commisures

less prominent commissure fibers

Association Fibers

type of fiber tract; connect different parts of the same hemisphere; short fibers connect adjacent gyri; long fibers connect different cortical lobes; run horizontally

Projection Fibers

type of fiber tract; enter cerebral cortex from lower brain or spinal cord centers or descend from cortex to lower area; motor output leaves through these fibers from cerebral cortex; tie the cortex to rest of nervous system and to body's receptors and effectors; run vertically

Internal Capsule

a compact band formed by projection fibers at the top of the brain stem on each side; pass between the thalamus and some of basal nuclei

Corona Radiata

distinctive arangment of projection fibers when the fibers radiat fanlike through the cerebral white matter to the cortex

Basal Nuclei

deep within cerebral white matter; third basic region of each hemisphere; group of subcortical nuclei; caudate nucleus, globus pallidus, and putamen constitute most of the mass of each group of basal nuclei; recieve input from entire cerebral cortex, as well as from other subcortical nuclei and each other

Lentiform Nucleus

a lens-shaped mass formed together by the putamen and globus pallidus; flanks internal capsule laterally

Corpus Striatum

the name for lentiform and caudate nuclei because the fibers of the internal capsule that course past and through them give them a striped appearance

What are basal nuclei associated with?

they are associated with subthalamic nuclei (located in lateral floor of the diencephalon) and substantia nigra of the midbrain

What influences muscle movements directed by the primary motor cortex?

the output nucleus of basal nuclei (globus pallidus) and the substantia nigra project to the premotor and prefrontal cortices

What are basal nuclei particularly important in?

starting, stopping, and monitoring the intensity of movements executed by the cortex

Diencephalon

forms the central core of the forebrain and is surrounded by the cerebral hemispheres; consists largely of 3 paired structures - the thalamus, hypothalamus, and epithalamus

Thalamus

consists of bilateral egg shaped nuclei; its a well hidden brain region that makes up 80% of diancephalon; relay station for information coming into the cerebal cortex; information is sorted out and edited

What do the bilateral egg shaped nuclei in the Thalamus form?

the superolateral walls of the third ventricle

How are the nuclei connected in most people?

at the midline by an Interthalamic Adhesion (intermediate mass)

How are nuclei in the Thalamus named according to?

their relative location

What are the functions of the nucleus in the Thalamus?

each has a functional specialty and each projects fibers to and recieves fibers from specific region of cerebral cortex

What do afferent impulses from all senses and all parts of body converege on?

the thalamus and synapse with at least on of its nuclei

The Thalamus plays a key role in what?

mediating sensation, motor activities, cortical arousal, learning, and memory; the gateway to the cerebral cortex

Hypothalamus

below the thalamus; caps the brain stem and forms the inferolateral walls of the third ventricle; extends from the optic chiasma (cross over point of the optic nerves) to posterior margin of mammillary bodies; contains many functionally important nuclei

Mammillary bodies

paired pealike nuclei that bulge anteriorly from the hypothalamus; relay stations in the olfactory pathways

Infundibulum

between the optic chiasma and mammillary bodies; stalk of hypothalamic tissue that connects to pituitary gland to base of the hypothalamus

Whats the main function of the Hypothalamus?

the main visceral control center of the body and is vitally important to overall by homeostasis

What are the Chief Homeostatic Roles of the Hypothalamus?

1. Autonomic Control Center, 2. Center for emotional response, 3. Body Temperature Regulation, 4. Regulation of food intake, 5. Regulation of water balance and thirst, 6. Regulation of sleep wake cycles, 7. Control of endocrine system functioning

Epithalamus

the most dorsal portion of the diencephalon and forms roof of the third ventricle

Pineal Gland

extends from posterior border of epithalamus; secretes hormone melatonin (sleep inducing signal and antioxidant), and hypothalamic nuclei; helps regulate sleep-wake cycle

Brain Stem

regions are midbrain, pons, and medulla oblongota; accounts for only 2.5% of brain mass; provides pathway for fiber tracts

Midbrain

located between the diencephalon and the pons

Cerebral Peduncles

on ventral aspect of midbrain; form vertical pillars that seem to hold up the cerebrum

Crus Cerebri

leg of the cerebrum; on each penduncle; contains a large pyramidal motor tract descending toward the spinal cord

Superior Cerebellar Penduncles

fibers tracts; connect the midbrain to cerebellum dorsally

Corpora Quadrigemina

nuclei scattered around white matter in midbrain; raise four domelike protrusions on the dorsal midbrain surface

Superior Colliculi

superior pair of Corpa Quadrigemina; visual reflexe centers that coordinate head and eye movements when we visually follow a moving object

Inferior Colliculi

part of the auditory relay from the hearing receptors of the ear to the sensory cortex; also act in reflexive responses to sound, such as in the startle relflex, which causes you to turn your head toward unexpected sound

Substantia Nigra

located deep to the cerebral peduncle; its dark color reflects a high content of melanin pigment; linked to basal nuclei; considered part of the basal nuclear complex by many authorities

Red Nucleus

deep to the sunstantia nigra; has reddish hue due to blood supply and presence of iron pigment in its neurons; relay nuclei in some descending motor pathways that effect limb flexion, and they are embedded in the reticular formation

Reticular Formation

a system of small nuclei scattered through the core of the brain stem

Pons

dorsally forms part of anterior wall of the fourth ventricle; composed of conduction tracts; oriented in two different directions

What are the functions of deep projection fibers in the pons?

they run longitudinally and complete the pathway between higher brain centers and the spinal cord

What are the functions of the superficial ventral fibers in the pons?

oriented transversely and dorsally; they form the middle cerebellar peduncles and connect the pons bilaterally with the two sides of the cerebellum dorsally

What nuclei act as relays for conversation between the motor cortex and cerebellum?

pontine nuclei

Medulla Oblongota

most inferior part of the brain stem; together with the pons forms the fourth ventricle

Pyramids

two longitudinal ridges flanking the midline of medulla's ventral aspect; formed by large pyramidal tracts descending from motor cortex

What is the Decussation of the Pyramids

just above the medulla - spinal cord junction, where most of the fibers in/from medulla cross over to opposite side before continuing into spinal cord

_________ are fiber tracts that connect the medulla to cerebellum dorsally

Inferior Cerebullar Peduncles

Olives

lateral to pyramids; oval swellings that are cause by wavy folds of gray matter of the underlying inferior olivary nuclei

What do the Nuclei of the Medulla do?

relay sensory information on the state of stretch of muscles and joints to the cerebellum

What type of nerves are associated with the Medulla?

hypoglossal nerves (emerge from the groove between the pyramid and olive on each side of brain stem), glossopharnygeal nerves, and vagus nerves

Vestibular Nuclear Complex

vestibular nuclei; mediate responses that maintain equilibrium

What sensory tracts nuclei are associated with the medial lemniscus tract?

the nucleus gracilis and nucleus cuneatus

What do nucleus gracilis and cuneatus do?

they serve as relay nuclei in a pathway by which somatic sensory information ascends from the spinal cord to the somatosensory cortex

What important Visceral Motor Nuclei are found in the Medulla?

Cardiovascular Center, Respiratory Centers, and various other centers; these centers carry out visceral functions from the hypothalamus which relays its instructions through meduallary reticular centers

Cerebellum

accounts for 11% of total brain mass; provides precise timing and appropriate patterns of skeletal muscle contraction for smooth coordinated movements and agility needed for our daily living, by processing inputs recieved from the cerebral motor cortex, various brain stem nuclei, and sensory receptors

Folia

fine transversley oriented pleatlike gyri on surface of cerebellum

How are the cerebellum and cerebral alike?

both have thin outer cortex of gray matter, internal white matter, and small, deeply situated, paired masses of gray matter

Purkinje Cells

types of neurons that populate the cerebullar cortex of cerebellum; the only cortical neurons that send axons through the white matter to synapse with the central nuclei of the cerebellum

Whats the pattern in the cerebellum that resembles a branching tree

Arbor Vitae

What coordinates body movement?

the anterior and posterior lobes of the cerebellum

What connects the cerebellum to the brain stem?

three paired fiber tracts - the cerebellar peduncles

Ipsilaterl

all fibers entering and leaving the cerebellum; means from and to the same side of the body

Superior Cerebellar Peduncles

caary instructions from neurons in the deep cerebellar nuclei to the cerebral motor cortex via thalamic relays

These two have no direct connections to each other.

the cerebellum and cerebral cortex

Middle Cerebellar Peduncles

carry one way communication from the pons to the cerebellum, advising the cerebellum of voluntary motor activities initiated by the motor cortex

Inferior Cerebellar Peduncles

connect medulla and cerebellum; convey sensory information to the cerebellum from (1) muscle prorioceptors throughout the body and (2) the vestibular nuclei of the brain stem, which are concerned with equilebrium and balance

Cerebellar Processing (1)

motor areas of cerebral cortex, via relay nuclei in brain stem, notify cerebellum of their intent to initiate voluntary muscle contractions

Cerebellar Processing (2)

cerebellum recieves information from proprioreceptors throughout the body and from visual and equilibrium pathways; this info enables cerebellum to evaluate body position and momentum

Cerebellar Processing (3)

cerebellar cortex calculates best way to coordinate force, direction, and extent of muscle contraction to prevent overshoot, maintain posture and ensure smooth coordinated movements

Cerebellar Processing (4)

via superior peduncles, cerebellum dispatches to the cerebral motor cortex its blurprint for coordinating movement; cerebellar fibers send info to brain stem nuclei

How is the cerebellum similar to a pilot?

the cerebellum continually compares the body's performance with the higher brains intention and sends messages to initiate the appropriate corrective measures

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