BIO 231 CHAPTER 13 BRAIN AND CRANIAL NERVES

4 major regions of brain [midsaggital view]

- cerebrum, halved into the left and right cerebral hemispheres [further split into the 5 lobes, frontal, parietal, occipital, temporal, insula] - diencephalon - brainstem - cerebellum

cranial nerves

12 in total with designated name and number, roman numerals according to position on brain, begining with most anterior

cranial meninges

3 connective tissue layers that separate and support the soft tissue of the brain from the bones of the craniu, they also enclose and protect some of the blood vessels that supply the brain, and lastly they contain and help circulate CSF In the order of deepest to superficial, it goes: pia mater, arachnoid mater, and dura mater

lobes of the cerebrum

5 lobes: frontal, parietal, temporal, occipital, insula frontal: form anterior poart of the cerebral hemisphere and ends posteriorly at a groove called the central sulcus; this is the boundary to the parietal lobe; inferior border of frontal love is the lateral sulcus, as this groove separates the frontal and parietal from the temporal; important anatomical feature of this love is the precentrla gyrus, which is a mass of nervous tissue under the central slcus;; the function of this lobe is tied to voluntary motor function, concentration, verbal coimmunication, decision making, planning, and the personality parietal, deep to parietal bone and forms superoposterior part of each cerebral hemisphere, terminates anteriorly at the central sulcus and posteriorly at a relatively indisinct parieto-oiccipital sulcus, and laterally at a lateral sulcus; important anatomical feature is the postcentral gyrus which is a mass of tissue posterior to central sulcus; involved with sensory functions like shape and tecture through touch and sensory input regardfing body position from the proprioceptors in the joints and muscles temporal lobe is internal to the temporal, inferior to lateral sulcus, involved with earing and smell occipital love is internal to occipital bone and forms posterior region of each hemisphere; responsible for processing incoming visual info and storing visual memories insula is a small love deep to the lateral sulcus and is observed by pulling aside temporal love, lack of accessibility prevents aggressive studies of its true function, assumed to help in memory and interpretation of taste

Neural tube defects (NTDs) are serious developmental deformities of the brain, sc, and meninges

Anencephaly; substantial or complete absence of brain and bones making the cranium, this is because the neural tube didn't close completely; survival is no longer than mere hours after birth, these are rare however and easily detected Spina bifida; occurs more frequently than anencephaly and the caudal portion of the tube won't close. Two forms of spina bifida occurs: spina bifida cystica; no vertebral arch forms, the posterior aspect of the spinal cord is unprotected, paralysis of the lower limbs is associated with this disease Spine bifida occulta: less serious, much more commonly partial defect in the vertebral arch that involves the vertebral lamina and spinous process; there is a tuft of hair in the region of the bony defect and people with this are asymptomatic as it is generally detected incidentally during x-rays CORRECTION OF DISEASE: increased intake of vitamin B12 and B9 (follic acid or folate) can help decrease the chances of this neural tube defect; these vitamins help with DNA formation and cell division

thalamus

forms superolateral walls of 3rd centricle and has paired oveal masses of grey matter on each side; located between anterior commissure and pineal gland each part of thalamus has about a dozen major thalamic nuclei that are organized into groups; ventral posterior nuclei relays sensory info to the primary somatosensory cortex of the parietal lobe, auditory info is relayed through the medial geniculate nuclei thalamus is principal and final relay point for incoming sensory info that's processed and projected to the appropriate lobes; only a small portion of sensory info that arrives at the thalamus is given to the cerebrym since the thalamus is an information filter

for a short time, the neural tobe will be open at both ends

these openings are neuropores and they close during the 4th week the opening closest to the future head is called the cranial neuropore the opening closest to the butt is called the caudal neuropore if these opening do not close, the human will have a neural tube defect and can affect the nervous system as the neural tube forms the CNS; cranial part of neural tubes expand from the brain as the caudal tube expands to form the spinal cord

grey and white matter distribution

Grey matter - derives color from cell bodies and dendrites of neurons; contains the cortex, a superficial layer of grey matter, or the nucleus/center, which are clusters of neuron cell bodies in the grey matter that are either close to the surface or deeper in the brain superficial grey area is the cerebral coretx and the inner deep part of the grey matter of the cerebrum is the cerebral nuclei cerebellar cortex has outer grey matter of the cerebellum spinal chord is reversed with an outer white matter and inner grey matter FUNCTION OF GM: synapses with grey matter help for integration and processing to occur in specific areas on either the brain or the spinal cord

hypothalamus

anteroinferior region of diencephalon, with a stalkilike infundibulim extending from it to attach to pituitary gland - master control of the autonomic nervous system; integration center and is the president over the autonomic nervous system that influences heart rate, blood pressure, digestive activities, and respiration - master control endocrine system; hormone secretion, creates Antidiuretic hormone and oxytocin - regulate body temp, body, preoptic, thermostat here - controls food intake; ventromedial, monitor glucose - controls water intake; monitor concentration of dissolved substances in blood - regulates the circadian rhythm - controls emotional behavior, location central of limbic system, pleasure aggression, fear, rage, content, and sex drive

encephalitis

acute inflammatory disease of brain caused by viral infection and death may occur

functional brain regions

acts as multi-association area between loves to integrate info from individual areasl functional brain region is the prefrontal cortex in the anterior portions of the frontal lobe; this is associated with higher intellectual functions like thought, judgement, expression of personality, planning, etc. it takes and coordinates info from multiple areas of the brain and evaluates possible consequences of one's action and mdoulates behavior based on what is socially acceptable; this develops continuously in our teens and 20s as axons are myelinating and unnecessary synapses are removed; thus why we are impulsive, emotional, risk taking, etc because our ****ing brain isn't mature functional brain region is also the wernicke area, where it is only in the left hemisphere and is involved with recognizing, understanding, and comprehending spoken or written language; works closely with motor speech area for fluent communication

TBI (traumatic brain injury)

acute brain damage after trauma, abrupt loss of consciousness with headache, drowsiness, and even amnesia contusion is TBI where bruising of brain causes blood leak from small vessels into subarachnoid space second impact syndrome (SIS) is where someone experiences second brain injury before the first one healed correctly; can lead to death

cerebral lateralization

assymetries in the frontal and occipital lobes shape called petalias right handed people have front frontal petalias, meaning right frontal lobe projects farther than the left; left occipital petalias is where the left occipital lobe extends farther than the right; it is said that left handed people are inclined to have reverse pattern (left frontal and right occipital) each hemisphere takes on a certain task as it is specialized, called the phenomenon of cerebral lateralization categorical hemisphere: left hemisphere, usually contains Wernicke and motor speech, specialized for language abilities and for performing sequential and analytical tasks like for science and math; direct correlation with info for analysis, function in categorization and identification representational hemisphere: right hemisphere and concerned with visuospatial relationships and analysis; seat for imagination and insight, musical talent and artistic skill, perception of patterns and spatial relationships, with comaparing sound, site, smell, and taste both of these hemispheres remain in constant communication throug commissures, like the corpus callosum, which has hundreds of millions of axons that project between the hemispheres lateralization of the hemispheres develops early in life, before a child is 5/6. functions of a damaged or removed hemisphere are often taken over by the other before lateralization is complete; the process can differ between the sexes like with women having thicker posterior parts of the corpus callosum due to having additional commissural axons, males have more lateralization and suffer functional loss more if a hemisphere gets damaged \cerebral lateralization is correlated with handedness; right handed people hafe a different lateralization pattern than those who are left handed. about 95% of the population, the left hemisphere is the categorical hemisphere, which correlated with the 90% incidence of being right handed. Correlation of this isn't as strict among left handed people who could have either hemisphere as their categorical hemisphere; though ti us stated that there is a thicker corpus callosum in a left handed person which means more signals are being relayed between the hemispheres, this controls speech in all the right handed and most of the left handed

protection and support of the brain

brain is protected and isolated by multiple structures body cranium provides rigid support protective CT membranes called meninges surround and partition portions of the brain CSF acts as cushioning fluid between layers of meninges Brain also has BBB to prevent entry of toxins and harmful substances

pons

bulging region of anterior part of brainstem sensory and motor tracts are in here and connect to brain and SC middle cerebellar penducles are transverse axons that connect pons to the cerebellum houses autonomic nuclei in pontine respiratory center; vital center along with the medullary respiratory center in the medulla oblongata; responsible for skeletal muscles breathing, main function iof pontine is th regulate smooth transition from breathing in to breathing out superior olivary nuclei are inferior to pons and they receive auditory input and are involved in the pathway for sound localization cranial nerve nuclei for both motor and sensory are here; for trigeminal CN V, abducens, CN VI, and facial CN VII, some nuclei for vestibulocochlear cranial nerves CN VIII are here too

higher order of the brain

by the age of 5, 95% of the brain growth is complete and the rest of the body won't reach adult size until puberty neurons can expand connections as the CNS develops and create increased synaptic junctions that are needed for ccomplex reflex activities and processes; the level of higher brain function capibility relies on the nervous system's maturation level

arachnoid mater

called arachnoid membrane as it resembled a web of collagen and elastic fibers called the arachnoid trabeculae deeper to the trabeculae is the subarachnoid space which has CSF arachnoid trabeculae extends through this sub space towards the pia mater; arachnoid trabeculae and the CSF support cerebral arteries and veins in the sub space

brain ventricles

cavities or expansions in the brain that are from the neural canal (lumen of embryonic neural tube) lined with ependymal cells that have CSF, they are connected to each other and the central canal of SC 4 ventricles, two lateral ones that are separated by the septum pellicudum, a thin medial partition; each lateral ventricle is connected in the third ventricle through an opening called the interventricular foramen; narrow canal called cerebral aqueduct passes through the midbrain and connects to the third ventricle and the 4th one. in the diencephalon is the smaller and thinner ventricle = third ventricle 4th ventricle is tetrahedron shaped and is located between the pons, medulla oblongata, and cerebellum; opens up to subarachnoid space via the lateral apertures and the single median aperture; this ventricle narrows at the nferior end before it merges with the slender central canal of the spinal cord

positions of the 4 major parts of the brain [inferior view]

cerebellum is inferior to cerebrum brainstem has 3 regions: midbrain, pons, medulla oblongata diencephalon is organized into epithalamus, thalamus, and hypothalamus (essentially these are internal structures) [12 pairs of cranial nerves extend from the brain] DIRECTIONAL TERMS USED: Anterior = rostral, towards the nose Posterior = caudal, towards the tail

cerebrospinal fluid CSF

clear and colorless, circulates in ventricles and subarachnoid space; bathes the exposed surfaces of the CNS and surrounds it buoyancy; the brain flots in the CSF to reduce weight by about 95% to prevent brain crushing under its own weight, it would sink through the foreamen magnum without CSF protection; provides liquid cushion to protect delicate neural structures from sudden movements,slows movements of brain if the skull or body moves suddenly environmental stability; transports nutrients and chem messengers to brain, removes waste products, protects nervous tissue from chem fluctuations that disrupt neural function, waste products and excess CSF are transported into the venous circulation

brainstem

connects cerebrum, diencephalon, and cerebellum to the spinal cord made of the midbrain, pons, and medulla oblongata in the order of superior to inferior bidrectional pathway for all tracts between the mejor regions of thebrain and the SC contains autonomic centers and reflex centers for regulating body functions; also houses nuclei of many cranial nerves

sensory areas

corticol areas in the parietal, temporal, and occipital lobes and the insula involved with consciousness awareness of sensation; each sense has a distncy cortical area and each primary cortical region typically has an association area in order to receive input from primary regions and integrate the current sensory output with previous experiences and memories primary somatosensory cortex n the postcentral gyrus of the parietal lobes; neurons here receive general somatic sensory info from receptors of the skin in terms of touch, pressure, pain, temperature, and sensory input from the proprioceptors from the joints and muscles for conscious interpretation of body position; we are conscious in this cortex sensory homunculus may be traced on postcentral gyrus surface, like a motor homunculus; larger portions occupied by body areas with large collections of sensory info somatosensory association areas are in the parietal love and are posterior to primary somatosensory cortex, integrates sensory info and interprets sensations for texture, temp, pressure, and shape sensory info for sight, sound, taste, smell arrives at cortical regions other than the parietal lobe primary visual cortex in the occipital love and receives incoming visual info visual assocaition area is in the occipital lobe and surrounds primary visual area, enables us to process visual info by analyzing color, movement, form, etc primary auditory cortex in the temporal and receives and processes auditory ingo, auditory association area located in this lobe and is posteroinferior to this auditory cortex, the cortical neurons here interpret characteristics of sound and can store memories of sound that you heard in the past primary olfactory cortex in temporal and provides conscious awareness of smell, primary gustatory cortex in the insule involved in processing taste info

electroencephalogram

diagnostic test where electrodes are attached to head to record electrical activity of the brain, helps with sleep disorders, lesions, and determining if a person is in a coma or is a vegetable, seizures can also be looked at when studying epilepsy (a seizure is abnormal electrical activity) EEG measures and plots the 4 brain waves, alpha beta theta and delta, distribution of waves and the frequency can depend on the person's age and what state they are in; alpha and beta are for awake and alert while theta and delta are for sleepl presence of the delta and theta during the wake state show a problem

functions of cerebellum

doesn't initiate skeletal muscle movement but coordinates and fine tunes as the cerebrum initiates it; ensures skeletal part follows the correct patterns also stores memories of previously learned patterns and this is performed indirectly by regulating activity along involuntary and voluntary motor pathways at the cerebral cortex, cerebral nuclei, and motor centers in the brainstem cerebrum starts the movement and sends the rough draft idea to the cerebellum which coordiantes and adjusts as needed also maintains equilibrium and posture, receives sensory info from muscles and joints to regulate body position, and can send info to the cerebellum and the cerebrum so the cerebrum is aware o everything despite not specifically looking at the joints of interest also receives convergent input from sensory and motor pathways, can unconsciously perceive info of body location, detect a problem and it can release error correcting nerve signals

cranial dural septa

double layers of dura mater from the meningeal layer of the derma mater extended as flat partitions in the cranial cavity at 4 spots these separate the specific parts of the brain and also stabilize and support the brain falx cerebri; largest of the 4 and is a sickle-shaped vertical fold of the dura mater located in the midsagittal plane; it projects into the longitudinal fissure between the hemispheres of the cerebral; the inferior portions attach to crista galli of ethmoid bone, posteriorly the inferior protein attaches to internal occipital crest; in the superior and inferior margins of this septum are two dural venous sinuses, the superior sagittal sinus and the inferior sagittal sinus tentorium cerebelli: horizontally oriented of the dura mater, separates the occipital and temporal loves of the cerebrum from the cerebellum; named because of the dural tent over the cerebellum it makes; the transverse sinuses are in the posterior border and the straight sinus is in the midsaggital region; anterior surface of this has a gap called the tentorial notch, which is a gap to allow passage to the brain stem falx cerevelli; extending from the midsaggital line inferior to the tenroium cerebelli; sickl shaped vertical partition that divides the hemispheres of the cerebellum; tiny occipital sinus is here in the posterior vertical border and is a dural venous sinus diaphragma sellae; smallest of them and forms a roof over sella turcica of the sphenoid bone; gap inside allows for passage of thin stalk called infundibulum that attaches to pituitary gland to the base of the hypothalamus

pineal gland

endocrine gland secretes melatonin for the circadian rhythm

hydrocephalus

excessive CSF leads to brain distortion and results from the obstruction in CSF flow or impaired absoroption of CSF at the arachnoid villi head is enlarged and neurologic damage can result, permanent brain damage also occurs if the hydrocephalus develops after cranial sutures close; tubes can be added to help reduce the flow and drain out excess fluid

reticular formation

extends through core of midbrain, pons, and medulla and extends into the diencephalon and spinal cord, has motor and sensory components communicates with spinal cord and helps regulate muscle tone, assists with autnomic motor functions like breathing, blood pressure, and heart rate by working the autonomic centers in medulla and pons sensory component is for alerting cerebrum of incoming info, the component is called the RAS or resticular activating system that processes visual, autidotry, and touch stimuli to keep us in the state of being alert, it also arouses us from sleep consciousness is the awareness sensation and voluntary control of the motor activities and it involves simultaneously activiting large areas of the cerebral cortex, levels of consciousness exist on an continuum where the highest is level of cortical activity is alertness where we are repsonsive, aware, and well oriented.

structural components of cerebellum

has 2 hemispheres that have 2 lobes each known as the anterior and posterior that are separated by the primary fissure; narrow band of nervous tissues that is called the vermis is between the lobes; the hemispheres and vermis have surface folds known as folia partitioned into 3 regions, the outer grey matter called the cerebellar cortex, the internal white matter, and then the deepest grey matter made of cerebellar nuclei; internal white area is the arbor vitae penduncles are the three thick nerve tracts that connect the cerebellum with the brainstem; the superior cerebellar penduncles connect cerebellum to midbrain, middle cerebellar peduncles connects cerebellum to the pons; inferior connects to medulla

epidural hematoma

hematoma is a pool of blood outside a vessel epidural hematoma is a pool of blood in the epidural space of the brain due to a severe blow; the adjacent brain tissue becomes distorted and compressed as the hematoma grows; can cause death but survivable if blood is drained and the bleeding vessel is tied off

meningitis

inflammation of meninges caused by viral or bacterial infection; create mo0re severe symptoms and can result in brain damage and death

pia mater

innermost layer of cranial meninges, thin layer of areolar ct that tightly holds to the brain and follows every fold of brain

emotion

interpretted by limbic system but controlled by the prefrontal cortex, decides the way we show our feelings aspects of emotions can depend on the intact, functional amygadaloud body and hippocampus and if they are famaged, they can create exaggerated expressions of emotions and anomalies in the learning and memory processes

midbrain

known as mesencephalon; superior portion of the brainstem with several components to it cerebral peduncles are motor tracts on the anterolateral surfaces of the midbrain; descending axons project through here and relay voluntary motor commands from primary motor cortex of each cerebral hemisphere; superior cerebellar peduncles connect the midbrain to the cerebellum; bands of myelinated sensory axons made of medial lemniscus extend from medulla oblongata, through pons and midbrain, all to the thalamus substantia nigra has symmetric nuceli in the midbrainl has dark appearance, houses clusters of neurons that produce NT dopamine, which can affect movement control, emotional response, and ability to feel pleasure and pain -- parkinsons related to these cells tegmentum inbetween nuclei of substantia nigra and preidqueductal gray matter; tegmentum has pigmented red nuclei and reticular formationl due to blood vessel densiry and the iron pigmentation of the cells; responsible for integrating ingo from the cerebrum and cerebullum and sends out motor commands to the erector spinae muscles to help maintain posture in back cerebral aqueduct, extends through midbrain and connects the 3rd and 4th vesicles, surrounded by the periaqueductal gray matter; outermotor nerve nuclei of the CN III and trochlear nerve CN IV are in the midbrain tectum is the most posterior of themidbrain and has 2 pairs of sensory nuclei which are the superior and inferior colliculi; also called the tectal plate. nuclei are relay stations for prcessing visual and auditory stuff; superior are for visually tracking things for turning the eyes; the inferior collects info for hearing and turns the head and eyes in the direction of a sound

cerebral hemispheres

left and right halves of the cerebrum; separated by the narrow and deep cleft called the longitudinal fissure that extends along midsaggital plane the hemispheres are separated and have only a few locations where the bundles of myelinated axons called tracts allow the formation of a white matter region and allow communication between them, these white matter tracts are called the corpus callosum as it connects the hemisphere and provides the main source of ocmmunication between the two hemispheres regarding the cerebral hemispheres: - while selected regions of the cortex to participate in specific functions, in cases it is diffuclt to assign a precise function to a specific regionl there is overlap and indistinct boundaries that permit a single region of the cerebral cortex to have different functions. Some cortical function like memory and consciousness however can't be given to any area - general rule, both the cerebral hemispheres receive sensory info from and project motor commands to the opposite sides of the body; right hemisphere controls the left side, left hemisphere controls right side - two cerebral hemispheres appear as anatomic mirror images but display functional differences, termed cerebral lateralization; for example regions in the brain that contrl speech and understanding verbalization are frequently on the left cerebral hem, the differences primarily affect higher order function

functional brain systems

limbic and reticular formation

cerebrum

location of conscious thought processes and the origin of all complex intellectual functions has 2 hemispheres on the superior aspect of the brain; allow for reading and language comprehension, formation of ideas and memory;; basically ther center of intelligence, reasoning, thought, memory, judgement, voluntary muscle control (skeletal) and conscious perception of senses associated are distinct regions of grey matterl the cerebral cortex and nucleus

limbic system

made of multiple cerebral and diencephalic structures that process and experience emotions, it is the emotional brain and it forms a ring around the diencephalon cingulate gyrus is an internal mass of cerebral cortex located in longitudinal fissure and is superior to the corpus callosum, seen on sagittal section and receives input from other components of the limbic parahippocampal gyrus is the mass of cerebral cortical tissue in the temporal lobe and it is associated with the hippocampus hippocampus is component of cerebrum located superior to parahippocampal gyrus, conects to diencephalon vis the fornix and is shaped like a seahorse, the hippicampus and para gyrus are essential to store memories and form the long term amygdaloid connects to hippocampus and helps with emotion and fear and extremeness of emtions olfactory bulbs/tracts/cortex are for orders being associate with memories fornix is the thin tract of white matter that connects to the hippocampus with limbic system structures of diencephalon various nuclei; anterior thalamic, habenular, septal, mammillary bodies of hypothalamus

cognition

mental processes like awareness, knowledge, memory, and perception, associated with cerebrum and forms about 70% of nervous tissue in the brain, responsible for cognition and processing integration of info between sensory and motor output personality abnormalities noted with damage to the prefrontal cortex that deals with abilioty to plan, think, and execute appropriate behavior lose the ability to detect and identify stimuli on one side of the body, primary somatosensory area in the hemisphere opposite to the affected area has been damaged agnoisa is the inability to recognize and uinderstand multiple stimuli, like the meaning or sound of words

functional areas of cerebrum

motor areas; areas that control movement primary motor cortex, or the somatic motor area, is located in precentral gyrus of frontal love; neurons here control voluntary skeletal muscle activity, the neruons' axons project to the opposite side of the brainstem or spinal cord, therefore left affects the right and vice versa; distribution of the motor cortex innervation to various body parts are diagrammed as a motor homunculus; homunculus proportions reflect the amount of cortex dedicated to motor activity in the area, higher in our hands versus our trunks certain motor functions are makked to certain specific areas of the frontal love, like motor speech and frontal eye field motor speech area in most people ins in the inferolateral portion of the left frontal lobe, this area regulates breathing and controllling muscular movements for vocal stuff frontal eye field in the frontal lobe superior to motor speech area and controls/regulates eye movements for reading and coordinated binocular vision primary motor cortical regions are connected to adjacent association areas that coordiante discrete skeletal muscle movement premotor cortex is also known as the somatic motor association area and is in the frontal lobe anterior to precentral gyrus; responsible for coordinationg leanred, skilled motor activities like moving the eyes while reading; sustained trauma in this area can still let people unsterstand written letters but have difficulty reading since the eyes cant follow the lines of the page

anatomic structure of white matter

myelinated axons in bundles make up the white matter, bundles of the myelinated axons are called tracts and are located on or close to the surface specific tracts in the brain do have names, corpus callosum, internal capsule, peduncles white matter in the SC is split into funiculi and white commissures PNS the bundles of myelinated axons are called nerves and they are called ganglia when they are clustered together GENERAL FUNCTION OG WM: relay nerve signals, they provide a means for info to be transmitted between different regions of the brain and spinal cord and between the brain and body.

sleep

natural and temporary anscence of consciousness, cortical activity is reduced and functions continue in the vital centers non-REM is non rapid eye movement, REM is rapid eye movement; both types have to with different EEG patterns and the abscence or presence of the eye moving REM has dreams that are memorable 75% of sleep is in non REM, 25% in REM non-REM for body repair, REM for consolidating and organizing memories nonREM has 4 stages, cycling through the nonREM and Rem is normal for the full sleep state average sleep needed is 8.5-9.5 hours a night and the lack of sleep causes problems with depression, impaired memory, and decreased immunefunction insomnia is when we can't fall asleep sleep apnea is when a person has breathing interruptions while sleeping, they use a CPAP or continuous positive airway pressure machine where aireways are kept open due to air being pumped through the mask and sleep without interruption

central white matter

of the cerebrum deep to gray matter of the cortex and is myelinated axons grouped together in tracts; can be association, commissural, or projection tracts association tracts: connects different regions of cerebral cortex in same hemisphere, short tracts are made arcuate fibers, they connect neighboring gyri in the same lobe; longer association tracts are longitudinal fasciculi, and they connect gyri in different lobes of the same hemisphere, like the one that connects the wernicke area to the motor speech commissural tracts extend between cerebral hemisphere through axonal bridges called commissures; prominent tracts that link the left and right hemispheres are the large, c shaped corpus callosum and the smaller anterior and posterior commissure projection tracts link the cerebral cortex to inferior brain regions and the spinal cord; like the projection tracts in the corticospinal tracts that carry motor signals from cerebrum to brainstem and spinal cord; packed group of axons in these tracts that are passing between the cerebral nuclei and the grey matter of the thalamus is called the internal capsule

medulla oblongata

or medulla, moist inferior part and is continuous with spinal cordl the inferior portion of medulla is flat with round shape and narrow central canal; this tube opening goes towards the pons and the central canal enlarges to become the inferior portion of 4th ventricle; all communication from brain and SC involves the tracts that come through the MO pyramids are the two longitudinal ridges along the medulla oblongata on the anterior surfaces; they house motor projection tracts known as corticospinal tracts in anterior region of medulla, acons of the pyramid traxts cross to the opposite side of the brain known as the decussation of the pyramids; this crossover allows the cerebral hemisphere to control the voluntary movements of the other side of the body lateral to the pyramids are olives, distinct bulges that have folds of grey matter called inferior olivary nucleus, they help relay ascending sensory nerve signals, especially proprioceptive info also there are paired inferior cerebellar peduncles that are tracts that connect to medulla oblongata to cerebellum SEVERAL AUTONOMIC NUCLEI AND CENTERS: - cardiovascular: has both cardiac centers, regulates heart rate and force of the output; has vasomotor center that controls contraction and relxation of smooth muscle in walls ot eh smallest arteries known as arterioles that can change the diameter of blood vessels, which also affects blood pressure - medullary respiratory: regulates repiratory rate and is made of ventral resp. group and dorsal resp. group. Influenced by pontine rest center and the primary function is to start neve signals that xause contraction of the breathing muscles OTHER NUCLEI in medulla can help with sneezing, cough, gag, etc. also contains cranial nerve nuclei that are associated with vestibulocochlear CN VIII an the glossopharyngeal CN IX the vagus CN X, accessory CN XI, and hypoglossal CN XII. medulla also has nucleus cuneatus and nucleus gracilis that relay somatic sensory info to the thalamus; medial lemniscus exits from the nuclei and protects through brainstem to ventral posterior nucleus of thalamus

cerebral nuclei

paired, irregular masses of grey matter buried deep in the central white matter of the basal region of the cerebral hemispheres inferior to the floor of the lateral ventricle (not the basal ganglia) REMEMBER: ganglion refers to clusters of neuron cell bodies outside the CNS where the nucleus is a collection of cell bodies inside the CNS in general they help regulate motor output initiated by cerebral cortex and help inhibit unwanted movements (parkinsons affects this) have multiple components with own specific function and realted to the overall function of the nuclei; components include: - caudate nucleus: enlargedhead and slender arching tail that parallels curves of lateral ventricle; each time a person initiates walking, the neuron in this nucleus stimulates the appropriate skeletal muscles needed - lentiform nucleus: compact traingular mass made of putamen and glbous pallidus; these are two masses of grey matter positioned between insula lobe and lateral wall of thalamus; putamen function in controlling skeletal muscular movement at subconscious level, globus pallidus excites and inhibits activities of thalamus to regulate skeletal muscle tone claustrum is the thin sliver of grey matter formed by a layer of neurons located internal to insula, processes visual info at subconscious level amygdaloid body: expanded region at tail of caudate nucleus, participates in expressing emotions, controlling behavior, and development of moods term of corpus striatum describes striated appearance of white matter in the internal capsule between grey matter of caudate nucleus and lentiform nucleus

blood brain barrier

part of general circulation; brain is protected from contents of blood and this barrier regulates what comes in and what comes out; prevents exposure of neurons to drugs, waste products from blood, and variations in the levels of normal substances that cause change in brain function specialized capillaries surrounded by astrocytes; composed of endothelial lining resting on basement membrane 3 significant structural differences from other capillaries: - tight junctions, prevent passage of stuff between cells - walls are more substantial with thickened basement membrane, further restrict passage of stuff from blood to brain - wrapped in perivascular feet by astrocyte; form outermost part of BBB BBB truly serves as gatekeeper and controls what materials pass from the blood to the brain HOWEVER IT IS NOT ABSOLUTE; lipid soluble molecules cross the plasma membrane by simple diffusion, products like nicotine, alcohol, and anesthetics can diffuse and go into the interstitial fluid of the CNS to reach the neurons; cocaine and methamphetamine damages the barriers marked, reduced, ir missing in parts of CNS: choroid plexus, hypothalamus, pineal gland; therefore the choroid plexus capillaries are permeable to produce CSF while the other two produce certain hormones that have ready access to the blood

epithalamus

partially forms posterior roof of diencephalon and covers third ventricle; posterior portion covers pineal glad and habenular nuclei

CSF formation, circulation, removal

production occurs about 500 mL per day, 1/2 liter; volume of the CSF in subarachnoid space at aby given time between 100-160 mL formed by choroid plexus, a region of specialized tissue in each ventricle and is made of a layer of glial cells called the ependymal cells and blood capillaries that are in the pia mater -- in order to enter the ventricle, fluid in the blood must cross these structures: blood capillary wall, pia mater, ependymal cells HOW IT IS MADE: blood plasma is filtered from blood capillaries across the capillary wall and pia mater, composition is modified by ependymal cells as it moves through; the fluid then is released into a ventricle and is referred to as CSF, chemical composition of CSF in the ventricle differs from the one of filtered blood plasma with more Na and Cl land less glucose (RBC, WBC, PLATELETS AND PLASMA PROTEINS NOT FILTERED FROM BLOOD CAPILLARIES AND THEREFORE ARE NOT APART OF THE CSF) after formation, CSF, it circulates through ventricles where additional fluid is added by ependymal cells, then the CSF goes to the subarachnoid and the volume is increased by adding interstitial fluid from the brain [collectively CSF is made by choroid plexus, ependymal cells, and fluid from subarachnoid] constant reabsorption needed for avoiding acummulation of CSF and compression of tissuel reabsoprtion occurs at arachnoid villi where extensions of the arachnoid mater comes through the dura mater into the dural venous sinuses. villi forms arachnoid granulation and as the CSF forms, fluid pressure rises in the sub space and forces the CSF from the sub space to cross the arachnoid villi and return to the blood in the dural venous sinuses; THEREFORE arachnoid villi provides conduit for one way flow of the excess CSF to go back into blood in the dural venous sinuses

primary brain vesicles

prosencephalon - forebrain mesencephalon - midbrain rhombencephalon - hindbrain

language

reading, writing, speaking, understanding words need the cortical areas of speech integration which is the Wernicke are for reading or hearing interpretation and the motor speech area is to receive nerve signals from the Wernicke are to help regulate motor activites needed to speak wernicke is therefore central for the ability to recognize written and spoken language, posterior to this is the angular gyrus which is a region that processes words that we read into a form that we can speak wernicke area sends speech plan to the motor speech area, which then initiates a specific patterned motor program transmited to primary motor cortex, then the primary motor cortex signals other motor neurons which stimulate muscles in the face to produce sound and speech Wernicke is the area that is categorical in most people, the cortical region opposite to this is the sees emotional content of speech, if this is damaged then the person cannnot understand emotional nuances like bitterness or happiness in spoken woirds lesion in this region results in aprosodia, which causes dull speech speech disorders apraxia where motor function is doisordered and the person cannot coordinate and execute the ability to talk despite knowing what they want to sau; there is difficulty in producing recognizeable sounds and sequences to form speech aphasia, difficulty understanding written stuff and speechl have problems finding correct words and may use nonsense to describe, many may notr realize that others cnanot understand them; usually seen with head injury ot triokes

habenular nuclei

relay signals to limbic system, also involved in visceral and emotional responses to odors

diencephalon

sandwiched between inferior regions of cerebral hemispheres, known as in-between brain, includes the epithalamus, thalamus, and hypothalamus; 3rd ventricle associated with diencephalon

cerebellum

second largest part of brain, coordinates fine control over skeletal muscle action and stores memories of movement patterns

interthalamic adhesion

small, midline mass of grey matter that connects right and left thalamic bodies

Brain development

starts in the cranial part of the neural tube in the human embryo, the tube undergoes disproportionate growth rates in different regions by late 4th week, 3 primary brain vesicles are developed which give rise to the different regions of the adult brain

dura mater

strongest of the meninges, outer and dense layer of connective tissue and has 2 layers meningeal layer is superficial to arachnoid periosteal layer is the more superficial and forms the periosteum on the internal surfaces of the cranial bones; usually the two layers are fused except for in the areas where they are separate and form the large, blood filled spaces of the dural venous sinuses (a sinus is a modified vein) triangular in the cross section and don't have valves to regulate the venous blood flow; they just drain blood from the brain two potential spaces associated with dura mater, epidural and subdural dura mater and skull bones separated by epidural which has the arteries and veins subdural space is between arachnoid and overlying dura mater either epidural or subdural space may become real space if blood or fluid accumulates in it

secondary brain vesicles, developed by 5th week from the 3 primary vesicles

telencephalon - from the prosencephalon and forms the cerebrum; grows rapidly and envelops diencephalon to fold it and create sulci and gyri diencephalon - derives from the prosencephalon and forms thalamus, hypothalamus, and epithalamus mesencephalon - only primary that doesn't form second piece, midbrain metencephalon - from rhombencephalon and forms the pons and cerebellum mylencephalon - rhombencephalon and forms medulla oblongata

neurulation

the process where the neural plate (thickened ectoderm in the embryo at week 3) is induced by underlying notochord to form a neural tube ultimately this forms all nervous tissue structures 1. neural plate develops central longitudinal indentation called the neural groove; at the same time cells along the lateral margins of the neural plate proliferate and become thickened neural folds, the tips of these folds form the neural crest 2. the neural folds then elevate and approach each other as the neural groove will deepen, the crest cells should now be the highest point of the neural groove. When viewed from a superior angle, the neural fold looks like the sides of a hotdog bun and the neural groove is the slit on the bun. 3. The neural crest cell will begin to punch off from the neural folds and from other structures 4. Lastly by the end of the third week, the neural folds have met and fused at the midline as the neural groove starts to form the neural tube (has an internal space called the neural canal). The tube initially fuses at the midline but later the portions of the folds slightly superior and inferior to the midline fuse as well; thus the neural tube forms as the neural folds zip together inferior and superior.

what limits the size of our brain? [brain left lateral view]

the volume of our skull, in order to fit more neurons in, we have folds called gyri, that create shallow depressions between themselves called sulci, and the deeper grooves are called fissures

memory

versatile human element of cognition of different lengths of time for storage capacities, can depend on complex interactions among different brain regions; information management can also deal with learning and forgetting info sensory memory is based on sensory input, like sounds and smells and sight, they can last maybe a second at most short term memory is limited and is a brief duration of less than a minute inless info is repeated long term, short term can be converted into this and can exist for limitless periods of time converting STM to LTM is encoding or memory consolidation; it requires proper functioning of the two components of the limbic system, the hippicampus and the amygdaloid body hippo needed for creating STM, LTM is stored in the association areas of the cerebral cortex; loss of ability to form STM win't affect meantenance of LTM since the two areas involve different anatomic strucutres