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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