258 terms

BIO 210 (Lecture Unit # 4) Ch 12: The Central Nervous System

Mrs Babb's BIO 210 CCTC Fall 2010
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Adult Brain Regions
cerebral hemispheres, diencephalon, brain stem, and cerebellum
Spinal Cord
central cavity surrounded by gray matter (mostly neuron cell bodies); external white matter composed of myelinated fiber tracts
Brain
similar gray matter and white matter pattern as spinal cord; has additional regions of gray matter;
Cortex
both the cerebral hemispheres and the cerebellum have this layer of gray matter
Ventricles
connected to one another and to the central canal of the spinal cord; hollow ventricular chambers are filled with cerebrospinal fluid and lined by ependymal cells
Lateral Ventricles
paired; one deep within each cerebral hemisphere; large C-shaped chambers that reflect the pattern of cerebral growth; each ventricle communicates with third ventricle
Septum Pellucidum
thin median membrane that seperated lateral ventricles
Third Ventricle
narrow; in the diencephalon; recieves communication from lateral ventricles; continuous with fourth ventricle
Interventricular Foramen
channel in which lateral ventricals communicate with third ventricle
Fourth Ventricle
continuous with third ventricle via cerebral aquaduct; lies in the hindbrain dorsal to the pons and superior medulla; continuous with the central canal of the spinal cord inferiorly; marked by three openings (paired apertures [in side walls] and median aperture [in its roof]); apertures connect ventricles to subarachnoid space
Cerebral Aquaduct
canal like; runs through the midbrain; connects 3rd and 4th ventricles
Subarachnoid Space
a fluid filled space surrounding the brain
Cerebral Hemispheres
form the superior part of the brain; account for 83% of total brain mass; most conspicuous part of brain; entire surface marked by gyri, seperated by sulci; each has 3 basic regions (superficial cortex of gray matter, an internal white matter, and basal nuclei [islands of gray matter situated deep within the white matter])
Gyri
elevated ridges of tissue
Sulci
shallow grooves
Fissures
deeper grooves which seperate large regions of the brain
Longitudinal Fissure
medial; seperates the cerebral hemisphere
Transverse Cerebral Fissure
seperates the cerebral hemispheres from the cerebellum below
Central Sulcus
lies in the frontal plane, and seperates frontal lobe from parietal lobe
Precentral Gyrus
borders the central sulcus anteriorly
Postcentral Gyrus
borders the central sulcus posteriorly
Occipital Lobe
seperated from parietal lobe by the parietooccipital sulcus
Parietooccipital Sulcus
located on the medial surface of the hemisphere
Lateral Sulcus
outlines the flaplike temporal lobe and seperates it from the parietal and frontal lobes
Insula
fifth lobe of cerebral hemisphere; buried deep within the lateral sulcus and forms part of its floor; covered by portions of the temporal, parietal, and frontal lobes
Cerebral Cortex
it enables us to be aware of ourselves and our sensations, to communicate, remember, and understand, and to initiate voluntary movements; composed of gray matter: neuron cells bodies, dendrites, associated glia and blood vessels; thin (2-4mm); 40% of the mass of the brain; each hemisphere connects to contralateral side of body; two hemispheres not entirely equal in functions
Motor Areas of Cerebral Cortex
control voluntary movement; lie in the posterior part of the frontal lobes
Primary Motor Cortex
contain large neurons known as pyramidal cells in precentral gyri that allow us to consciously control the precise or skilled voluntary movements of our skeletal muscles
Pyramidal Tracts
massive voluntary motor tracts formed by long axons of pyramidal cells whichh project to the spinal cord
Motor Homunculi
upside - down caricatures representing the motor innervation of body regions
Premotor Cortex
anterior to the precentral gyrus in the frontal lobe; controls learned motor skills of a repetitious or patterened nature; coordinates movement of several muscle groups simultaneously or sequentially; involved in planning of movements that deepend on sensory feedback
Brocas's Area
lies anterior to the inferior region of the premotor area; present in one hemisphere only (usually the left); a motor speech area that directs muscles of the tounge; is active as one prepares to speak
Frontal Eye Field
located partially in and anterior to the permotor cortex and superior to Broca's area; controls voluntary movement of the eyes; wont control eye reflexes
Sensory Areas
area concerned with conscious awareness of sensation; occur in the parietal, insular, temporal, and occipital lobes
Primary Somatosensory Cortex
resides in the postcentral gyrus of the parietal lobe, just posterior to the primary motor cortex; receive information from the general (somatic) sensory receptors in the skin and from proprioceptors (position sense receptors) in skeletal muscles, joints, and tendons; capable of spatial discrimination (identification of body region being stimulated)
Somatosensory Association Cortex
lies posterior to primary somatosensory cortex and has many connections with it; function is to integrate sensory inputs (temperature, pressure, and so forth) relayed to it via the primary somatosensory cortex to produce an understanding of an object being felt; determines size, texture, and relationships of parts of objects being felt
Primary Visual Cortex
on the extreme posterior tip of occipital lobe, but most of it is buried in the calcarine sulcus in medial aspect of occipital lobe; recieves visual information that originates on retina of the eye
Visual Association Area
surrounds the primary visual cortex and covers much of the occipital lobe; uses past visual experiences to interpret visual stimuli (color, form, and movement); complex processing involves entire posterior half of the hemisphere
Primary Auditory Cortex
located in superior margin of temporal lobe abutting the lateral sulcus; interprets information from inner ear as pitch, loudness, and location
Auditory Association Area
located posterior to primary auditory cortex; permits perception of the sound stimulus; stores memories of sounds and permits perception of sounds
Olfactory Cortex
lies on medial aspect of the temporal lobe in a small region called piriform lobe which is dominated by hooklike uncus; part of the primitive rhinecephalon which includes all parts of cerebrum that recieves olfactory signals (olfactory tracts and bulbs that extend to the nose); region of conscious awarness of oders
Gustatory Cortex
region involved in perception of taste stimuli; located in insula deep to temporal lobe
Visceral Sensory Area
posterior to gustatory cortex; involved in conscious perception of visceral sensations (ex: upset stomach, full bladder)
Vestibular Cortex
posterior part of the insula and adjacent parietal cortex; responsible for conscious awareness of balance (position of head in space)
Multimodal Association Areas
receive inputs from multiple sensory areas; send outputs to multiple areas, including the premotor cortex; allow us to give meaning to information received, store it as memory, compare it to pervious experience, and decide on action to take; each individiual perception come together (hear, see, touch, feel, and smell); can be divided into 3 parts (anterior association area, posterior association area, limbic association area)
Anterior Association Area
in frontal lobe, also called prefrontal cortex; the most complicated cortical region of all; involved with intellect, complex learning abilities, recall, and personality; contains working memory needed for judgment, reasoning, persistence, and conscience; development depends on feedback from social enviornment
Posterior Association Area
large region encompassing parts of temporal, parietal, and occipital lobes; play role in recognizing patterns and faces, localizing us and our surroundings in space, and binding different sensory inputs into a coherent whole; involved in understanding written and spoken language
Limbic Association Area
includes cingulate gyrus, the parahippocampal gyrus, and hippocampus; part of limbic system; provides emotional impact that makes a scene important to us; hippocampus establishes memories that allow us to remember incidents
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
The Limbic System
a group of structures located on the medial aspect of each cerebral hemisphere and diencephalon; included are parts of rhinencephalon (septal nuclei, cingulate gyrus, parahippocampal gyrus, dentate gyrus, and C-shaped hippocampus), and the amygdala
Amygdala
an almond shaped nucleus that sits on the tail of the caudate nucleus; recognizes angry or fearful facial expressions, asseses danger, and elicits the fear response
What are the main limbic structures in the diencephalon?
the hypothalamus and the anterior thalamic nuclei
What does the fornix do?
link limbic system regions of diencephalon and cerebral hemispheres together
What two parts of the limbic system are important in emotions?
the amygdala and cingulate gyrus
Cingulate Gyrus
plays a role in expressing our emotions through gestures and in in resolving mental conflicts when we are fustrated
Rhinecephalon
the smell brain; triggers emotional reactions and memories from odors;
Most limbic system output is relayed through the....
Hypothalamus
Psychosomatic Ilnesses
under acute or unrelenting emotional stress fall prey to visceral ilnesses, such as high blood pressure and heartburn; emotion induced illness caused by hypothalamus
Thoughts are mediated by ...
the cognitive brain
Intimate relationship between our feelings are mediated by...
the emotional brain
Reticular Formation
composed of loosely clustered neurons (white matter); these neurons form three broad columns along the length of the brain stem (raphe nuclei, medial group, and lateral group of nuclei)
What is an outstanding feature of the reticular neurons?
their far flung axonal connections; ideal for governing the arousal of the brain as a whole
Reticular Activating System
arm of reticular formation where reticular neurons send a continuous stream of impulses to the cerebral cortex, keeping the cortex alert and conscious and enhancing its excitability
What do impulses from all the great ascending sensory tracts do when they synapse with RAS neurons?
keep them active and enhancing their arousing effect on the cerebrum
How does the RAS act like a filter for flood of sensory inputs?
repetitive, familiar, or weak signals are filtered out, but unusual, significant, or strong impulses do reach consciousness
What does normal brain function involve?
continuous electrical activity of neurons
Electroencephalogram
records some aspects of neuron activity in brain; made by placing electrodes to an apparatus that measures electrical potential differences between various cortical areas
Brain Waves
patterns of neuronal electrical activity recorded; generated by synaptic activity at the surface of the cortex
How is wave frequency expressed?
in hertz (Hz); its the number of peaks in one second; a frequency of 1 Hz means that one peak occurs each second;
Alpha Waves
(8-13 Hz) regular and rhythmic, low amplitude, synchronus waves; they indicate a brain is idling - calm, relaxed state of wakefullness
Beta Waves
(14-30 Hz) rythmic waves but are not as regular as alpha waves and have a higher frequency; occur when we are mentally alert
Theta Waves
(4-7 Hz) more irregular; common in children; uncommon in adults but may appear when concentrating
Delta Waves
(4Hz or less) high amplitude waves seen during sleep and when reticular activity system is damped, such as anesthesia
Consciousness
encompasses conscious perception of senstations, voluntary initiation and control of movement, and capabilities associated with higher mental processing (memory, logic, judgment, perseverance, and so on)
How is consciousness defined?
on a continuum that grades behavior in response to stimuli as (1) alertness, (2) drowsiness or lethargy (which proceeds to sleep), (3) stupor, and (4) coma
What are the current suppositions about consciousness?
1. it involves simultaneous activity of large areas of the cerebral cortex. 2. it is superimposed on other types of neural activity. 3. it is holistic and totally interconnected
Unconsciousness
a signal that brain function is impaired
Fainting
a brief loss of consciousness; most often indicates inadequate cerebral blood flow due to low blood pressure
Non-Rapid Eye Movement Sleep
first major type of sleep; defined in terms of EEG patterns; during first 30 to 45 of sleep cycle we pass through first 2 stages of NREM and into NREM stages 3 and 4, slow wave sleep; frequency of EEG waves decline as we pass through deeper and deeper sleep
Rapid Eye Movement Sleep
after 90 minutes of NREM sleep EEG pattern change abrubptly and we go to REM sleep; alpha waves; increase in heart rate, respiratory rate, and blood pressure; oxygen in brain is tremendous in this stage
Carcadian/24 hours cycle
reflect the alternating cycles of sleep and wakefullness
What is responsible for timing of the sleep cycle?
the hypothalamus
What is suprachiasmatic nucleus?
in the hypothalamus; a biological clock; regulates its preoptic nucleus
Preoptic Nucleus
a sleep inducing center; puts cerebral cortex to sleep by inhibiting brain stem's RAS (reticular activating system)
RAS Centers
help maintain the awake state but also mediate some sleep stages, especially dreaming sleep
What is slow wave sleep presumed to be?
restorative
What happens to a person when they are deprived of sleep?
they become moody and depressed, and exhibits various personality disorders
What does REM sleep give the brain?
an opportunity to analyze the day's events and work through emotional problems in dream imagery
What are the daily sleep requirnements of infants to adults?
16 hours in infants to 7.5 to 8 hours of sleep in early adulthood
Narcolepsy
when people lapse abruptly into REM sleep from the awake state; these sleep episodes last about 15 minutes and occur without warning; triggered by a pleasurable event; brains of people with this have fewer cells in the hypothalamas that secrete peptide called orexins (wake up chemical)
Insomnia
a chronic inability to obtain the amount or quality of sleep needed to function adequatly during the day
Sleep Apnea
temporary cessation of breathing during sleep; victim awakes abruptly due to hypoxia (lack of oxygen)
What function involves practically all of the association cortex?
language
What do patients with lesions in Broca's Areas suffer from?
can understand language but have difficulty speaking
What do patients with lesions involving Wernicke's area suffer?
are able to speak but produce a type of nonsense often referred to as a word salad; difficulty understanding language
Whats a language implemenation system that analyzes incoming and produces outgoing word sounds and grammatical structures?
Brocas and Wenickes area working together with basal nuclei
Memory
the storage and retrieval of information; essential for learning and incorporating our experiences into behavior and are part and parcel of our experiences
What does memory storage involve?
2 distinct stages; short and long term memory
Short-term memory
working memory; capacity is limited to seven or eight chunks of information
Long-term memory
limitless capacity; can be forgotten with time; STM gets sent here when we want to remember something really good
What is the transfer of information from STM to LTM affected by?
emotional state; rehearsal; association; automatic memory
Memory Consolidation
involves fitting new facts into the various categories of knowledge already stored in cerebral cortex
Declarative (fact) Memory
entails learning explicit information, such as names, faces, words, and dates; related to our conscious thoughts and our ability to manipulate symbols and language; when fact memories are commited to LTM, they are usually filed along with context in which they were learned (ex: when you think of your new aquaintance, you probably picture him at the basketball game where you met him)
Nondeclarative Memory
less conscious or even unconscious learning; categories include procedural (skills) memory (piano playing), motor memory (riding a bike), and emotional memory (your pounding heart when you hear a rattle snake); acquired through experience and repetition; do not have to think through how to do something you just do it; once learned hard to unlearn
How/where are specific pieces of each memory stored?
near regions of the brain that need them so that new inputs can be quickly associated with the old
How do we create new memories for declarative memory?
1. sensory input is processed in the association cortices, which then cases cortical neurons to dispatch impulses to medial temporal lobe (includes hippocampus and surrounding temporal cortical areas
2. Temporal lobe areas play major role in memory consolidation and memory access ( by communicating with thalamus and prefrontal cortex)
3. prefrontal cortex and medial temporal lobe recieve input from acetylcholine - releasing neurons in basal forebrain
4. sprinkiling of acetylcholine onto these strucutres allow formation of memories
What does the loss of ACh input seem to disrupt?
the formation of new memories and retrieval of old ones
How are memories retrieved?
when the same sets of neurons that were initially involved in memory formation are stimulated
What does damage to hippocampus and surrounding medial temporal lobe structures on either side result in?
slight memory loss
Antergrade Amnesia
when consolidated memories are not lost but new sensory inputs cannot be associated with old, and person lives in the here and now from that point on
Retrograde Amnesia
the loss of memories formed in the distant past
What happens molecularly during learning?
(1) neuronal RNA content is altered and newly synthesized mRNAs are delivered to axons and dendrites, (2) dendritic spines change shape, (3) unique extracellular protiens are deposited at synapses involved in LTM, (4) the number and size of presynaptic terminals may increase, and (5) more neurotransmitter is released by the presynaptic neurons
Long-Term Potentiation
a persistent increase in synaptic strength that has been shown to be crucial for memory formation; first identified in hippocampal neurons that use amino acid glutamate as a neurotransmitter
NMDA receptors
kind of glutamate receptor; can act as a calcium channel and initiate the cellular changes that bring about LTP; are blocked preventing calcium entry
What happens when postsynaptic terminal is depolarized by binding of glutamate to different receptors?
NMDA block is removed and calcium flows into the postsynaptic cell
What does calcium influx trigger?
activation of enzymes that carry out two main tasks; first they modify the protiens in the postsyaptic terminal, and also in the presynaptic terminal via retrograde messengers such as oxide and endocannabinoids; second they cause the activation of genes in the postynaptic neurons nucleus, which leads to synthesis of synaptic protiens
CREB
the molecular messenger that brings news to the nucleus that more protien is needed; more creb the more protien synthesis and stronger synapse becomes
BDNF (brain-derived neurotrophic factor)
required for protien synthesis phase of LTP
Meninges
three connective tissue membranes that lie external to the CNS organs
What are the functions of Meninges?
(1)cover and protect CNS (2) protect blood vessels and enclose venous sinuses (3)contain cerebrospinal fluid (4) form partitions in the skulli
What are the meninges from external to internal?
dura mater, arachnoid mater, and pia mater
Dura Mater
means touch mother; strongest meninx; two layered sheet of fibrous connective tissue where it surrounds the brain; superficial periosteal layer attached to inner surface of skull (periosteum); deeper meningeal layer forms true external covering of brain and continues in vertebral canalas spinal dura mater
Dural Venous Sinuses
dural layers not fused together; collect venous blood from brain and direct it into the internal jugular veins of the neck
Dural Septa
flat partitions the subdivide cranial cavity; limit excessive movement of brain within the cranium including Falx Cerebri, Falx Cerebelli, and Tentorium Cerebelli
Falx Cerebri
large sickle shaped fold that dips into the longitudinal fissure between the cerebral hemispheres; attaches to crista galli anteriorly
Falx Cerebelli
small midline partition that runs along the vermis of cerebellum
Tentorium Cerebelli
resembles a tent over the cerebellum; nearly horizontal dural fold extends into transveres fissure between cerebral hemispheres and cerebellum
Arachnoid Mater
midline meninx; forms loose brain covering; never dips into sulci at cerebral surface; seperated from dura mater by subdural space
Subdural Space
narrow serous cavity that seperates dura mater from arachnois mater; contains a film of fluid
Subarachnoid Space
weblike extensions; beneath arachnoid membrane; span this space and secure the arachnoid mater to underlying pia mater; filled with cerebrospinal fluid and contains largest blood vessels serving brain
Arachnoid Villi
knoblike projections of arachnoid mater; protrude superior;y through the dura mater and into superior sagittal sinus; cerebrospinal fluid is absorbed into venous blood of sinus
Pia Mater
means gentle mother; composed of delicate connective tissue and is richly invested with tiny blood vessels; only meninx that clings tightly to brain
Cerebrospinal Fluid
found in and around the brain and spinal cord; forms liquid cushion that gives buoyancy to CNS structures; reduces brain weight by 97% and prevents the brain from crushing under its own weight; also protects the brain and spinal cord from blows and other trauma; helps nourish the brain
Whats the composition of CSF?
a watery broth similar to composition of blood plasma; contains less protien than plasma and its ion concentrations are different
Choroid Plexuses
hang from roof of each ventricle form CSF; frond shaped clusters of broad thin walled capillaries enclosed first by pia mater and then by layer of ependymal cells lining the vetricles; permeable
How are Choroid Plexus ependymal cells joined?
by tight junctions, and they have ion pumps that allow them to modify this filtrate by actively transporting only certain ions across their membrane into the CSF poolw
Whats the CSF volume in adults?
is about 150 ml (about half a cup) is replaces every 8 hours or so; about 500 ml of CSF is formed daily
How do Choroid Plexuses help clean CSF?
by removing waste products and unnecessary solutes
How does CSF move freely through the ventricles?
some CSF circulates into the central canal of spinal cord but most enters the subarachnoid space via lateral and median aperatures in the walls of the fourth ventricle
Hydrocephalus
accumulation of CSF is brain due to blockage of tumer, etc.
Blood Brain Barrier
a protective mechanism that helps maintain a stable environment for the brain
What 3 layers in the brain capillaries must bloodbourne substances pass through?
endothelium of capillary wall; thick basal lamina surrounding external face of each capillary, and the bulbous feet of the astricytes clinging to the capillaries
How is the blood brain barrier selective?
nutrients such as glucose, essential amino acids, and some electroytes move passivley by facilitated diffusion through the endothelial cell membranes
What bloodbourne metabolic wastes are denied entry to brain tissue?
protiens, certain toxins, and most drugs
What is the blood brain barrier ineffective against?
fats, fatty acids, oxygen, carbon dioxide, and other fat soluble molecules that diffuse easily through all plasma membranes
Concussion
an alteration in brain function; usually temporary, following a blow to the head; victim may be dizzy or lose consciousness
Contusion
more serious concussion; individual may remain conscious, but severe brain stem contusions always cause coma
Subdural/Subarachnoid Hemorrhage
bleeding from ruptered into those spaces; accumulation of blood in skull; increases pressure and compresses brain tissue
Cerebral Edma
swelling of the brain
Cerebrovscular Accidents (CVAs)
most common nervous system disorder and third leading cause of death in America; strokes; occur when blood circulation to brain area is blocked and brain tissue dies; results in hemiplegia, sensory deficits, or speech impairments
Ischemia
deprivation of blood supply to any tissue
Alzeheimer's Disease
a degenerative brain disease in which betamylid peptide deposits and neurofibrillary tangles appear; marked by deficit of ACh; results in slow, progressive loss of memory and motor control and increasing dementia
Parkinson's and Huntington's Disease
neurodegenerative disorders of the basal nuclei; both involve abnormalities of the neurotransmitter dopamine (too little or too much secreted) and are characterized by abnormal movements
Complete fusion of the neural groove forms what structure?
neural tube
What 2 openings form from at either end from the fusion of the neural folds?
rostral neuropore

caudal neuropore
What gives rise to the ventricle system and central canal of the spinal cord?
neural canal
Name the 3 primary brain vesicles
prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)
What 2 secondary vesicles arise from the prosencephalon?
telencephalon

diencephalon
What 2 secondary vesicles arise from the hindbrain?
metencephalon

myelencephalon
What secondary vesicle arises from the mesencephalon?
mesencephalon
What 3 structures develop from the telencephalon?
cerebral cortex

basal ganglia

lateral ventricles
What 5 structures develop from the diencephalon?
thalamus

hypothalamus

epithalamus

subthalamus

3rd ventricle
What 2 structures develop from the mesencephalon?
midbrain

cerebral aqueduct
What 3 structures develop from the metencephalon?
pons

cerebellum

4th ventricle
What 2 structures develop from the myelencephalon?
medulla

4th ventricle
Name the 3 brain flexures
midbrain flexure

cervical flexure

pontine flexure
Which flexure develops in the region of the metencephalon? spinal cord? due to rapid growth?
pontine flexure

cervical flexure

midbrain
Which plate lies dorsally?
alar plate
Which plate lies ventrally?
basal plate
What type of nuclei are found in the alar plate?
sensory nuclei
What type of nuclei are found in the basal plates?
motor nuclei
What nuclei lie on the medial aspect of the basal plate?
somatic motor nuclei
What nuclei lie on the lateral aspect of the basal plate?
visceral motor nuclei
What nuclei lie on the lateral aspect of the alar plate?
somatic sensory nuclei
What nuclei lie on the medial aspect of the alar plate?
visceral sensory nuclei
From what structure do the cerebral hemispheres develop?
telencephalon
What forms from the cavity of the diencephalon?
3rd ventricle
What forms from the cavity of the cerebral hemispheres?
lateral ventricle
What structures hangs down from the hypothalamus?
pituitary gland
What germ layer gives rise to the pituitary gland?
ectoderm
What is the name of the ectodermal upgrowth that forms the adenohypophysis?
hypophyseal pouch
What is the name of the neuroectoderm downgrowth that forms the neurohypophysis
neurohypophyseal pouch
What 2 primordial structures give rise to the pituitary gland?
stomodeum (anterior and intermediate lobes, tuberal part)

diencephalon (posterior lobe and infundibulum)
Where are craniopharyngiomas found?
sphenoid bone
What is pharyngeal hypophysis?
accessory anterior lobe tissue