Structural Organization1. Central Nervous System the central switchboard of incoming & outgoing messages; primary organs are the brain & spinal corda. Nuclei: a collection of dendrites within the CNSb. Tracts: collection of axons of the neurons within the CNS

2. Peripheral Nervous System connects CNS to the rest of the bodya. Ganglia: located outside of the spinal cordb. Nerves: extend from ganglions, extending to distant regions of the body to allow CNS to connect to those regions

Functional Organization Sensory Nervous System detects & transmits stimuli from receptors to CNSSomatic sensory: processes sensory info; (consciously aware of stimuli eyes, ears, skin; ex: tactile receptors in skin sends sensory info to brain & gives us the feeling of touch)Visceral sensory: processes sensory info that is not consciously perceived from blood vessels & internal organs such as the heart (BP to CNS)

Motor Nervous System motor output from CNS to effector organs such as the muscle/glandSomatic motor: processes motor output that innervates skeletal muscles & generally under voluntary controlAutonomic motor: processes motor output that innervates smooth & cardiac muscles or various glands & is generally involuntarily Sympathetic: responsible for Fight or Flight response; utilizes the neurotransmitter Norepinephrine Fight or Flight: characterized by increase of heart rate, which increases BP as well as the rate & depth of breathing; activated by fear (dangerous situations), etc.Parasympathetic: responsible for Rest & Digest response; utilizes the neurotransmitter Acetyl CholiRest & Digest: activated after a meal; actively is responsible for the secretion of various digestive enzymes to break down the meal

CNS DevelopmentWhen a sperm fertilizes an egg it results with a zygote The zygote goes through several cell divisions to give rise to a multicellular structure known as morulaMorula differentiates into a blastocystBlastocyst gives rise to primary germ layersThe ectoderm which is one of the germ layers, differentiates & gives rise to the neuronal tubeThe neuronal tube consists of 3 parts: forebrain, midbrain & the hindbrain in the embryo that is one month oldAs the embryo develops these primary structures give rise to other structures:Forebrain: develops to give rise to the telencephalon which develops into an adult brain structure known as the cerebrum & the diencephalon which consists of 3 major parts, the thalamus, hypothalamus & epithalamusMidbrain: develops into mesencephalon which is part of the brain stem of an adultHindbrain: develops into metencephalon which gives rise to the pons in the brainstem & the cerebellum of an adult; & myelencephalon which gives rise to the medulla oblongata in the brainstem of an adult

Adult Brain: Overview 4 primary structures:1. Cerebrum: largest part of the brain structures that is responsible for all higher brain fx including complex reasoning, thoughts, intelligence, long term memory storage, & personality2. Cerebellum: responsible for the maintenance of equilibrium and body balance 3. Brain Stem: primitive part of the brain (made up of the midbrain, pons & medulla oblongata) that is responsible for involuntary responses such as regulating the heart rate, breathing & body temperature 4. Diencephalon: deep within the brain (made up of 3 primary parts central thalamus, hypothalamus, & epithalamus; hypo = below; epi = above)

White & Gray MatterThe brain is made up of 2 types of matter Gray Matter: located in cerebral cortex & made up of the cell bodies & dendrites of neurons White Matter: located deep within the brain & is made up of a collection of axons; appears white due the axons being myelinated

Cranial MeningesThe brain is housed within the cranial cavity of the skull & is protected by the flat bones of the cranium from physical injury; surround the brain itself is a set of membranes known as cranial meninges which consists of 3 layers-1. Pia Mater: innermost layer that is made up of delicate, loose areolar CT2. Arachnoid Mater: middle layer that is made up of a delicate collection of collagen & elastic fibers (resembles a spider-web) a. Arachnoid trabeculae: is the collection of the collagen & elastic fibers b. Subarachnoid space: space in between these fibers that are filled with cerebrospinal fluid (CSF); c. blood vessels can be found within the arachnoid mater which supplies blood to the neuronal tissue of the brain 3. Dura Mater: the outer most layer that is made up of tough, dense irregular CT that consists of 2 sub-layers in which both layers are typically fused to one another except in regions where they separate to form large blood-filled cavities known as dural venous sinuses (which are responsible for draining blood away from the brain) - a. Periosteal layer: is in direct contact with the flat bone which forms the cranium of the skullb. Meningeal layer: direct contact with arachnoid layer

*Meningitis: inflammation of meninges caused by bacterial &/or viral agentscan be treated by a course of antibiotics or antiviral medication.

Cranial VentriclesWithin the brain are cavities known as cranial ventricles, these cranial ventricles are responsible for the production of CSF that is found within the subarachnoid space. 1. Lateral ventricles: the larger ventricles located in the cerebrum2. 3rd ventricle: located within the diencephalon3. 4th ventricle: located within the cerebellum & brain stem

*These ventricles are all connected to each other lateral ventricle is connected to the 3rd ventricle via interventricular foramen (foramen = opening; inter = between; intra = within) 3rd ventricle is connected to the 4th ventricle via a channel called cerebral aqueduct (aqueduct = channel)Ch. 12 Central Nervous System1/21/15 6:10 PM

Cerebrospinal Fluid (CSF)CSF is involved in providing 3 primary fx:1. Buoyancy: allows brain to float within the cranial cavity; decreases the weight of the brain up to 96% (without CSF, brain would be crushed by its own weight)2. Protection: acts as a shock absorber & provides cushion for the brain from mechanical/physical injury (ex: during a car accident, when your head moves back & forth from impact, the CSF slows the movement of your brain; without it, the brain will hit the bones of the cranium resulting in mechanical/physical injury to the neuronal tissue of the brain)3. Stability: inhibits & reduces fluctuations in temperature & internal chemicals within the cranial cavities

CSF Formation Choroid Plexus: located in each cranial ventricle; is involved in the formation of CSF; it is made up of 2 structures:i. continuous capillaries: tiny blood vessels via the Pia materii. ependymal cells: a layer of the neuroglial cells that surrounds the capillaries

CSF is formed from blood as some of the fluid is filtered out of the blood, it is modified by the ependymal cells to give rise to the CSF CSF has the same composition as the blood plasma minus blood plasma proteins such as hemoglobin, albumin, -globulins, -globulins, -globulins, etc. (these proteins are too big to pass barriers)

CSF Circulation1. CSF is formed from the choroid plexus of the lateral ventricles2. As it is formed, it flows into the 3rd ventricles through the interventricular foramen3. From the 3rd ventricle, it flows into the 4th ventricle through the cerebral aqueduct4. From the 4th ventricle, it can: a. enter the central canal of the spinal cord, orb. leave through the lateral apertures/medial apertures5. CSF can then enter the subarachnoid space6. Within the subarachnoid space, CSF will circulate to provide stability, buoyancy & protection to the brain against injury7. As it flows through the subarachnoid space, excess CSF drains from the subarachnoid space due to the pressure difference & is pushed out via the arachnoid villi & enters the blood via dural venous sinuses (which contains blood)a. if excess CSF is not drained, it will build up, resulting in - i. Children Hydrocephalus: where there is blockage (that is due to a defect in the arachnoid villi) in the drainage of the CSF into the dural venous sinuses, the head of the child doubles/triples in size because the cranial sutures are not yet fused together, allowing the head to expand as the pressure goes outwardii. Adults does not result in head enlargement because the sutures between the bones (frontal, parietal, temporal, occipital bones) that form the cranium are fused together & closed; the pressure can go outward due to these fused sutures allowing the pressure to go inward towards the neuronal tissue of the brain, destroying those brain tissues results in cognitive impairment (unless treated through the insertion of venous shots to the abdominal cavity to allow drainage of the excess fluid )

Ch. 12 CNS: Cerebrospinal Fluid1/21/15 6:10 PM

Blood-Brain Barrier (BBB)BBB are gate keepers that selectively allow certain substances to enter the brain & make contact with the central neurons while preventing other substances such as toxins present in the blood from entering to prevent any damage to the neurons neurons must be protected as they do not regenerate; they are rare cell types of the body that does not generally under go cell division once they are gone, they are gone forever; resulting in some cognitive impairment which is why there is a need for protective mechanisms via the cranial cavity, dural meninges, CSF, & BBB

BBB are made up of 3 structures:Endothelial cells: make up the bulk of tiny blood vessels = continuous capillaries; endothelial cells are fused together via the tight jx which acts as a glue that connects the cells together forming a continuous layer of capillariesa. Tight jx are significant - the material has to pass through the cell membrane of the endothelial cells rather than squeezing in between the cells in order to enter the interstitial fluid that surrounds the neurons in the braini. the cell membrane is selectively permeable, so by forcing the materials to pass through the cell membrane, a greater degree of control of which substances can enter is established cell membrane is made up of phospholipids, so any substance that has to pass through must be small & lipid-soluble 2. Basement membrane: made up of glycoproteins; fuses the endothelial cells to the perivascular feet of the astrocytes3. Astrocytes: specialized neuroglial cells; extends cytoplasmic processes that wrap around the continuous capillaries forming another barrier through which the material must pass through in order to reach the sensitive neuronsa. astrocytes wrap the perivascular feet around the continuous capillaries, &b. the perivascular feet also wrap themselves around the neurons

*Any material has to pass through both the endothelial cells & the cell membranes, & then has to enter the astrocytes in which the astrocytes present the material to the neurons this allows to protect neurons against various toxic chemicals both endothelial cells & astrocytes can modify these chemicals as they are transporting & presenting them to the neurons

*Psychoactive drugs small & lipid soluble drugs that can penetrate & pass through the BBBs, entering the brain, bringing about some effect ex: alcohol, coffee, nicotine from cigarettes, cocaine, heroine, general anesthesia

*Parkinsons disease is caused by a deficiency of the neurotransmitter, Dopamine, which is neither small or lipid-soluble; so artificial Dopamine cannot penetrate these BBBs to relieve the symptoms of the disease L-Dopa (psychoactive drug) is small & lipid soluble allowing it to penetrate the BBBs, & once it enters the interstitial fluid it is converted into DopamineCh. 12 CNS: Blood-Brain Barriers1/21/15 6:10 PM

Cerebrum: OverviewCerebrum is made up of 2 cerebral hemispheres in which each hemisphere controls the opposite side of the body - Left hemisphere: controls the right side of the bodyRight hemisphere: controls the left side of the body*this is due to the projection tracts which decussate or cross over in the spinal cord

longitudinal fissure: divides the left & right hemisphere, except at the point where they connect through the corpus callosumcorpus callosum: allows for the communication between the left & right hemispheres

the cerebrum folds into itself forming convulations to allow for it to be more compact, letting it fit within the limited space inside the cranium Convulations are made up of - Gyrus/Gyri: peaksSulcus/Sucli: depressions

Cerebrum DivisionThe Cerebrum is organized into Gray matter & White matter Gray matter (collection of cell bodies & dendrites of neurons) is organized into 2 structures:Cerebral cortex: the folds on the outer shell of the brainCerebral nuclei: little interior islands of gray matter White matter (collection of axons): inner white matter that occupies the interior of the cerebrum & presents the tracts that allow for communication between the different parts of the cerebrum

Cerebral Cortex The cerebral cortex, the outer shell, is organized into 5 functional lobes Frontal lobe has 4 important areas:Prefrontal cortex: anterior portion that is responsible for higher brain fxs such as reasoning, complex thoughts, intelligence, & personalityPrimary motor cortex: involved in the contraction of skeletal muscles which enables voluntary muscle movements Premotor cortex: involved in processing highly complex learned motor behavior & storage of long term memories associated with complex sequences of skeletal muscle movements/contractions required for complex motor activities (such as riding a bike, playing a piano, etc.is located between the prefrontal & primary motor cortexBrocas area: involved with language & specifically with the production of speech; responsible for the contraction of the skeletal muscles associated with the mouth, lips & tongue, in order to produce comprehensible speech

* MRIs & CAT scans are utilized to visualize different areas of the brain during cognitive tests to see which areas of the brain is active characterized by a high level of glucose utilization which lights up on the CAT scan

Parietal lobe has 2 important areas:Primary somatosensory cortex: anterior portion that processes sensory information from tactile receptors in the skin, resulting in a conscious perception of touch as well as the ability to determine whether an object is hot or cold to touch & pressureSomatosensory association area: posterior portion involved with the storage of long term memory associated with how a specific object feels to touch (allows you to determine an object without looking at it) Central sulcus/fissure: separates the frontal lobe from the parietal lobeTemporal lobe has 3 primary areas:Primary auditory cortex: processes sensory information from the hair cells located in the inner ear, allowing to consciously perceive sound/hearingAuditory association area: responsible for the storage of long term memory of sounds heard in the past which enables to determine how voices of different people sound, songs, etc.Primary olfactory cortex: processes sensory information from olfactory cells located in the nasal cavity allowing to consciously perceive various odors/smellsLateral sulcus: separates temporal lobe from parietal lobeOccipital lobe has 2 areas:Primary visual cortex: receives sensory information from photoreceptors of the retina in the eye, enabling the conscious perception of sight Visual association area: stores long term memories associated with visual information allowing to recognize places previously visited, individuals by facial features, etc.damage to this association area results in a type of memory loss (amnesia) known as face blindness (the inability to recognize individuals by facial features)individuals who have this damage causes them to rely on the auditory association area to determine the individual based on how they soundParieto-occipital sulcus: separates the parietal lobe from the occipital lobeInsular lobe (Insula) has 2 areas:Primary gustatory cortex: involved in processing sensory information from the gustatory cells located within the taste buds on the surface of the tongue, allowing to consciously perceive various tastesVisceral sensory area: processes visceral information from internal organs (ex: stomach, urinary bladder, etc.)when the stomach fills with food, it expands, & activates mechanoreceptors which sends a nerve impulse to the visceral sensory area resulting in the feeling of being full (tells you to stop eating)as the urinary bladder fills with urine, it stretches which activates mechanoreceptors in the bowl of the urinary bladder & sends nerve impulses to visceral sensory area resulting in the increasing urgency to urinate

Multimodal Association AreasMultimodal association areas occupy the cerebral cortex in more than one lobe (occupies both parietal & temporal lobes)Wernickes area: involved with the understanding/comprehension of both written & spoken language, allowing you to understand as well as distinguish between languages, etcBrocas area & Wernickes area communicate with one another to produce comprehensible speech Gnostic area: involved in the integration of all the sensory information (visual, auditory, olfactory, gustatory, somatosensory) to create a clear picture of the current activity

Motor & Sensory Homunculus1. Motor Homunculusa. Precentral gyrus: body parts (ex: fingers, face, etc) that require detailed & precise types of movements is reflected by the fact, that a great amount of the primary motor cortex is devoted to such a control (require a greater degree or greater surface area of the primary motor cortex) 1. Sensory Homunculusa. Postcentral gyrus: Body parts/areas that are very sensitive (ex: lips, tongue, fingertips) have a greater concentration of tactile receptors within the skin, have a more greater areas of the primary somatosensory cortex devoted to process that sensory information

Brain PlasticityBrain plasticity is the ability of the brain to rewire itself LearningAs a child grows, the relative numbers of the neurons stays the same, however, as the child is learning & experiencing new sensations, the neighboring neurons extend cytoplasmic processes the dendrites & axons making connections with other neighboring neuronsAs the child is re-emphasizing things learned through repetition, those connections increase in number; through repetition the information that is learned, is stored through the extensions of the dendrites to the neighboring neuronsThe extensions create a network

Blind IndividualsBlind individuals typically have an increased somatosensory & auditory perception (hearing & touch)the primary somatosensory cortex & primary auditory cortex sends tracts into the occipital lobe & takes over the primary visual cortex (which is no longer being used)

*Parts of the brain work together to accomplish a single task (an interconnectivity) ex: To play the violin:1. requires a contraction of the skeletal muscles & voluntary movement requiring the primary motor cortex2. playing the violin is a complex motor task that requires the premotor cortex3. when touching the strings of the violin it activates tactile receptors which sends impulses to the primary somatosensory cortex4. to play the violin, you need to look at the violin & the strings, this activates photoreceptors in the retina of the eye, which sends impulses to the primary visual cortex5. the sound being generated from playing the violin stimulates the hair cells of the inner ear which activates AP to send impulses to the primary auditory cortex

Cerebral NucleiDeep within the cerebrum are cerebral nuclei that represents a collection of the cell bodies, dendrites & axons of the neuron

The general fx of the cerebral nuclei is to start, stop & monitor the intensity of the skeletal muscle contraction initiated by the primary motor cortex of the frontal lobe to produce smooth movements & prevent antagonistic & unnecessary movement

Some several types of cerebral nuclei include 1. Caudate nucleus: 2. Putamen:3. Globus pallidus:

Damage to the cerebral nuclei results in: too little of movement & slow movement (Parkinsons disease), or too much movement & jerky movement (Huntingtons disease)

Inner White Matter Cerebrum is made up of inner white matter Inner white matter is made up of tracts (collection of axons) There are 3 Major types of Tracts 1. Association tracts: allow for the communication between different parts of the brain within the same hemisphere, there are 2 subtypes:a. arcuate fibers: shorter tract that allows for the communication between different parts of the brain of the same lobe b. longitudinal fasciculi: longer tract that allows for the communication between 2 or more different lobes within the same hemisphere2. Commissural tracts: allows communication between the 2 (left & right) hemispheres; represented by the corpus callosum as it connects the 2 hemispheres3. Projection tracts: allows communication between the brain & spinal cord; it connects higher brain centers (cerebrum) to the brain stem, cerebellum & then to the spinal cord

Cerebral LateralizationCerebral lateralization refers to the fact that the 2 cerebral hemispheres are specialized for different tasksCategorical Hemisphere (left hemisphere) is responsible for:a. Language it contains Brocas area b. Reasoning & Analytical skills it contains Wernickes areaRepresentational Hemisphere (right hemisphere) is responsible for:c. Imagination & Storytellingd. Musical & artistic abilities) *One of the hemispheres is always more dominant than the other in 95% of the population, the left/categorical hemisphere is more dominant than the right/representational hemisphere*Co-dominance can exist where neither of the hemispheres are more dominant than the other (ex: people who are ambidextrous)Ch. 12 CNS: Cerebrum1/21/15 6:10 PM

DiencephalonThe Diencephalon consists of 3 major structures Thalamus2 important fxs:acts as a relay center for the sensory information in which it routes the sensory information to appropriate areas of the cerebral cortexacts as a gate keeper, in which it filters irrelevant sensory information, allowing only certain sensory information to be passed on to the cerebral cortex to be consciously perceivedLSD (psychoactive drug) that can cross BBBs & inhibits the fx of the thalamus & allows all types of sensory information to reach the cerebral cortex & be consciously perceived, overpowering its ability to process the information, resulting in visual & auditory hallucinations (seeing & hearing things that are not real)Epithalamus contains 2 important structures Habenular nucleus: responsible for processing visceral & emotional responses to various odors/smell Pineal gland: responsible for the production & secretion of the hormone, melatonin, which regulates the circadian rhythm (sleep & wake cycle)Hypothalamus has many fx:it controls the Autonomic Nervous System, in which it regulates heart rate, BP, digestion & breathingit controls the Endocrine system, in which it controls the secretion from a master endocrine gland called the pituitary glandthe pituitary gland controls the secretions from other endocrine glands within the bodyThermoregulation it regulates the temperature of the body, maintaining it at 37Ccentral thermoreceptors in the hypothalamus continuously monitor the temperature of the blood, any variation in which the temperature is below/above 37C in the blood will initiate a response by the hypothalamus if the temperature is below 37C, it initiates a response such as shivering thermogenesis to generate heat which increases the temperature if the temperature is above 37C, it initiates a response such as sweating, which then results in evaporative cooling which is when the sweat evaporates from the surface of the skin to take away heat, bringing the temperature down Control of food & water intake Food intake: chemoreceptors within the hypothalamus continuously monitor glucose levels & amino acids in the blood as amino acid levels go down, the chemoreceptors are activated, resulting in the increase of hunger when hunger occurs, eating follows the carbohydrates obtained from food are broken down into glucose, where glucose is absorbed in the blood, increasing glucose levels as you eat, the stomach expands & mechanoreceptors are activated in which it sends nerve impulses to the hypothalamus, resulting in the sensation of being fullWater intake: osmoreceptors in the hypothalamus monitor osmolarity of the blood (how concentrated the blood is with the solutes) so after a meal, as carbohydrates, lipids, & proteins are broken down into glucose & amino acids, these solutes are absorbed into the blood, increasing the blood concentration/osmolarity which then activates the osmoreceptors resulting in thirst when thirsty, you drink water the water gets absorbed into the blood which then dilutes the blood concentration & brings the blood osmolarity down & back to normal Control of circadian rhythms the hypothalamus controls the secretion of melatonin from the pineal gland Regulates emotional responses the hypothalamus controls the limbic system which is involved emotional response (rage, anger, fear, sadness, pleasure, happiness, etc.)Sex drive via controlling the limbic system Ch. 12 CNS: Diencephalon1/21/15 6:10 PM

BrainstemThe brainstem consists of 3 parts 1. Midbrain a. Superior colliculi: known as the visual reflex centers which help to track a moving object with our eyes & also reflexively/involuntarily make you turn your head in the direction of a visual stimulus (such as an approaching car)b. Inferior colliculi: act as auditory reflex centers that causes you to involuntarily turn your head in the direction of a sound (such as a loud bang)c. Red nucleus: i. appears red in preparations due to the red staining (iron) pigments that it containsii. responsible for keeping our back muscles (specifically the erector spinae) in a state of perpetual contraction to maintain posture while sitting or walking d. Substantia nigra: i. appears black in preparations due to the black staining pigment melaninii. associated with the production of the neurotransmitter Dopamineiii. plays a crucial role in controlling unnecessary jerky movements (resting tremors)iv. damage to the substantia nigra & consequent decrease in Dopamine leads to the signs & symptoms associated with Parkinsons disease (where individuals exhibit slow, voluntary movements & resting tremors particularly in the hands & head)2. Pons a. Pontine respiratory centers: the most important & crucial structure of the pons that regulates the rate & depth of breathing; there are 2 areas of the pontine respiratory centers i. apneustic area: promotes breathing (occurs during exercise)ii. pneumotaxic area: inhibits breathing occurs during inhalation as you inhale, the lungs are filled with air to a point where you cant breath anymore, this is due to the activation of mechanoreceptors which sends impulses to the pneumotaxic area which inhibits breathing to prevent overstretching the lungs (overstretching of the lungs damage the sensitive pulmonary alveoli)

3. Medulla Oblongata The medulla oblongata is involved with many autonomic fxs, the 3 principle fxs include:a. Cardiac center: controls heart rate & stroke volume (strength/force of cardiac contraction)b. Vasomotor center: controls the diameter of the blood vessels i. control via vasoconstriction resulting in the decrease of the diameter, orii. control via vasodilation resulting in the increase of the diameter*both cardiac & vasomotor centers are crucial in regulating BP

c. Medullary Respiratory center: establishes the basic rhythm of breathing, ensuring a continuous mechanical ventilation (breath in & out) especially when asleepthe medullary respiratory center work with the pontine respiratory centers, creating these groups: Ventral group Dorsal groupCh. 12 CNS: Brainstem1/21/15 6:10 PMdamage to the medullary respiratory centers occurs in which the individual stops breathing when asleep such individuals require to be hooked up to a ventilator during sleep

Cerebellum Cerebellum Anatomy1. Cerebellum is made up of 2 cerebellar hemispheres (left & right), both consists of:a. Anterior lobeb. Posterior lobe2. The interior of the cerebellum is made up of Gray & White matter:a. Gray matter is contained within the cerebellar cortex & isolated cerebellar nucleib. White matter represented by a tree-like structure called the arbor vitae

Cerebellum FunctionCerebellum generally keeps the brain aware of where the head is relative to the trunk of the body & integrates from the proprioceptors & vestibular organs; primary functions include:1. Coordination & fine tuning of body movementsa. Cerebral cortex rough draft (blue)b. Propriorecepetors (yellow)c. Cerebellumi. Integration (green)ii. Final draft (red)2. Maintains body balance & posturea. Vestibular organsb. Proprioreceptors

Limbic SystemHippocampus: central to the formation of new memoriesMemory formation short term memorylong term memoryencoding: moving memory from short term to long termAmygdala Emotional responses Animals that have a damaged amygdala will show no fear to objects that have been once feared in the past

Reticular FormationThe reticular formation extends throughout the brainstem into the diencephalon and includes:1. Reticular activating system: keeps us in the state of mental alertnessa. receives & processes sensory information from the eyes, ears & tactile receptors within the skin b. projects that sensory information to the appropriate areas of the cerebral cortex, making us consciously aware of such sensation2. General Anesthesia administered to the pt prior to surgery, rendering the pt unconscious at the level of the reticular activating system, inhibiting the neurons & stops the sensory information from projecting into the cerebral cortex therefore makes the pt unconscious & unaware of the painful stimulation during surgery

Brain Wave Patterns & EEG EEG (Electroencephalogram): records the electrical activity of neurons giving rise to brain waves there are 4 principle categories:

Alpha waves: present in individuals that are awake & are in a calm, relaxed state Beta waves: present in individuals that are concentrated on a cognitive task (ex: studying) Theta waves: mostly present in young children; present in adults in which it occurs prior to sleep, deep meditation, during drowsiness Delta waves: present during deep sleep or under general anesthesia*The clinic significance of the EEG is that it can help to diagnose various neurological disorders, ranging from epilepsy to comaEpilepsy: neurological disorder in which the neurons are generating & transmitting action potentials either too frequently or too rapidly, resulting in convulsions (seizures) in which there are 2 major forms:Petit mal seizures (absence seizures):typically occurs in children (10 min), leading to the death of the neuronal tissue; there are 2 types of strokes:a. Ischemic stroke: result of the build up of fatty plaque within the bulb of the cerebral arteries that supply the blood to the neuronal tissuesi. Embolus: traveling blood clot; that can get stuck within the plaque & can block the blood flow to a specific area of the brain, depriving it from oxygen & leading to the death of the neuronal tissueb. Hemorrhagic stroke: result of an aneurysm, the bursting of the cerebral arteries, causing bleeding within the brain i. the ball of the cerebral arteries can form into balloon-like structures, where any blow to the head may cause a rupture of the cerebral artery, resulting in an aneurysmii. the aneurysm then causes bleeding within the brainiii. bleeding within the brain, then interrupts the delivery of oxygen to the brain, resulting in brain damage* signs & symptoms of a stroke varies depending on which part of the brain is affected

3. Degenerative Brain Disordersa. Alzheimers disease i. typically occurs around the age of 65ii. characterized by Dementia: slow progressive loss of cognitive fxs memory, personality, etc memory loss is gradual; it starts with small things such as forgetting the keys, forgetting to turn off the oven, etc & then progresses more severely as the brain mass is lost, resulting in the inability to not recognize closest family members affects the speech area, resulting in a loss of language abilities affects prefrontal cortex, resulting in personality changesiii. Cortical atrophy: decrease in size, refers to the loss of brain mass as neurons die off & brain mass is lost, it results in the enlargement of the lateral & 3rd ventricles loss of neurons = loss of brain mass, causing cognitive impairment; neuronal death is caused by: the accumulation of neurofibrillary tangles within the axons, impairing axonal transport, leading to the death of the neurons the accumulation of defective amyloid precursor proteins within the neurons, leading to their deathb. Parkinsons disease i. due to the degeneration & loss of neurons from the substantia nigra (midbrain) loss of these neurons means there is a decrease in the synthesis & secretions of Dopamine results in signs & symptoms of Parkinsons disease, such as: slow, voluntary movements expressionless face stiff posture resting tremors (particularly in hands)ii. Treatment of the Parkinsons disease include: L-Dopa Deep brain implants sends small electrical charge to prevent resting tremors Stem cell theory transplanting embryonic neurons into the substantia nigrac. Huntingtons disease i. hereditary disorder (follows autosomal dominance of inheritance)ii. onset of disease is about 35-45 yrs of ageiii. individuals live ~15 yrs after the 1st appearance of the symptoms of the diseaseiv. symptoms include: start with face twitching, with then progresses into jerky movements such as arm, leg twitching, etcv. symptoms then lead to the failure of the diaphragm & pulmonary ventilation, causing the inability to breath in & out, resulting in deathvi. characterized by the accumulation of the tactile protein known as huntintin & death of the neurons (particularly within the cerebral nuclei)

Ch. 12 CNS: Brain Disorders1/21/15 6:10 PM

Spinal Cord: OverviewSpinal cord connects the brain to the rest of the body allowing for the communication between the brain & the bodyIt connects to the brain at the level of the medulla oblongata of the brainstem & moves inferiorly all the way down to the L1 vertebrae of the vertebral column Spinal cord divides into 4 parts:Cervical part gives rise to the spinal nerves (C1-C8), allowing for the communication with the distant parts of the bodyThoracic part gives rise to spinal nerves T1-T12Lumbar part gives rise to nerves L1-L5Sacral part gives rise to nerves S1-S5 & CX1Conus medullaris: point where the spinal cord terminateCaude equine: a collection of nerve plexuses (after conus medullaris)Filum terminale: CT that attaches the cauda equine terminally to the coccyx of the vertebral column

Spinal MeningesSpinal cord is enclosed & protected by spinal meningesThe spinal meninges are made up of 3 layers:Dura mater (most outer layer) made up of tough, dense irregular CTwithin the Dura mater is the epidural space that is made up of a collection of adipose & areolar CTthe epidural space provides cushion for the spinal cord within the vertebral columnArachnoid mater (middle layer) made up of a collection of collagen & elastic fibersthe subarachnoid space is located in between the elastic fibersthe subarachnoid space contains CSF, which protects the spinal cord from mechanical shock Pia mater ( inner layer) made up of delicate, loose areolar CT & is in direct contact with the spinal cordSpinal Cord: AnatomySpinal cord contains Gray & White matterGray matter (located centrally) made up of cell bodies & dendrites of neuronsorganized into hornsposterior horns (posterior side of spinal cord)lateral horns (lateral side of spinal cord)anterior horns (anterior side of spinal cord)White matter (located peripherally) made up of axons of neuronsorganized into tracts located in the funiculiposterior funiculus (in between the posterior horns)lateral funiculus (in lateral horns)anterior funiculus (in anterior horns)Spinal Cord Gray Matter (reflex integration)Gray matter is involved in Reflex Integration (processes of reflexes)Posterior horns houses sensory axons & interneurons; receives sensory information from the periphery (PNS) to the spinal cordit has somatic sensory neurons that carries sensory info that is consciously perceived (ex: touch), &visceral sensory neurons that carries sensory info that is not consciously perceived (ex: baroreceptors BP)Anterior Horn houses somatic motor neurons; innervates skeletal musclesLateral Horn houses autonomic motor neurons that carries motor output from the spinal cord to the PNS, specifically to the effector organs (cardiac muscles, smooth, muscles/glands)

Reflex IntegrationReflex initiates the contraction of the skeletal muscle involuntarilyStimulus activates a receptor (ex: pain receptor)Receptor activates the sensory neuron which carries sensory information from PNS to CNS, resulting in the action potential traveling toward the spinal cordThis information will then be integrated with respect to the interneuron which connects the sensory neuron to the motor neuron which sends motor output from CNS towards effector muscleAnother AP moves from the spinal cord to the effector muscle, resulting in the contraction of that muscle & allows for that area of the body to pull away from the stimuli causing painThe sensory info will reach the cerebral cortex & be perceived as such, but only once we have removed the hand from the stimuli

Reflex: Classification Reflexes can be classified:based on the effectors being innervated, they are classified into:visceral reflex: innervate glands, smooth & cardiac muscle tissueEx: baroreceptors of the aorta which monitors & regulates BP a reflex we are not consciously aware ofsomatic reflex innervate skeletal muscles Ex: withdrawal reflex during touching something that is hot

based on complexity of the reflex, they are classified into:monosynaptic reflex: has only a single synapse only 2 neurons, 1 sensory neuron which synapses with the monosynaptic motor neuron Ex: stretch reflex specialized sensory receptors integrated within the skeletal muscle are stretched, activating AP towards the spinal cord & causes the motor neuron to shoot the AP to the muscle, causing it to contract resulting in the extension; this reflex prevents overstretching of the muscles where overstretching can damage/tear muscle fibers

polysynaptic reflex: more complex, many synapses in which it has 3 or more neurons making up that reflex (sensory neuron, interneuron, motor neuron) Ex: withdrawal reflex if you touch a stimuli, it activates receptors & therefore activates a sensory neuron which shoots an AP towards the spinal cord resulting in the motor neuron generating a nerve impulse towards the muscle, causing it to involuntarily contract & remove it from stimuli & prevent damage

Spinal Cord: White Matter (impulse conduction)White matter is organized into areas called funiculi that is made up of a collection of tracts, 2 basic tracts are:Ascending tracts (inner)directs sensory information towards the braindivides into 2 pathways:Somatosensory pathways (consciously aware)starts with some somatic receptors such as the tactile receptors in the skin ( ex on the right side of the body)the tactile receptors in the skin will activate the primary neuron & activate an AP leading into the spinal cordwithin the spinal cord, the primary neuron will synapse with the secondary neuronthe secondary neuron will decussate (cross over) to the other side of the spinal cordthe axons will form the ascending tract which will travel to the thalamus of the brain where it will synapse with the tertiary neuronthe tertiary neuron will project to a specific area of the primary somatosensory cortex (ex - of the left cerebral hemisphere) resulting in the perception of touchViscerosensory pathways (unconsciously aware)consists of visceral receptors such as baroreceptors in the aortavisceral receptors activate the primary neuron which synapses with the secondary neuronthe secondary neuron projects into the hypothalamus keeping the brain informed of what the BP of the body is at all timeshypothalamus regulates the BP

Descending tracts (outer)directs motor information from the brain to the spinal cord to the PNS (effector)divided into 2 pathways:Direct pathway (innervates skeletal muscle tissue; voluntary control)consists of upper motor neurons (where cell bodies reside; within the primary motor cortex) that extend to the midbrain, pons, medulla oblongata, to the spinal cord where it decussatesin the spinal cord, the upper motor neurons synapses with the lower motor neurons lower motor neurons innervate the skeletal muscleIndirect pathway (innervates smooth muscle, cardiac muscle & glands; involuntary control)starts with upper motor neurons that originates from hypothalamusupper motor neurons synapse with interneurons at the spinal cord, neurons synapse with lower motor neuronslower motor neurons then innervates the smooth muscle/cardiac muscle & glands , allowing hypothalamus to control heart rate, digestion & secretion from endocrine & exocrine glands (sebaceous glands/sweat glands)Ch. 12 CNS: Spinal Cord1/21/15 6:10 PMDecussation for most pathways occur at the spinal cord or medulla oblongata

Spinal Cord DisordersSpina Bifida most common in undeveloped, 3rd world countries result of a failure of the terminal portion of the neural tube to close properly during development vitamin deficiency (specifically folic acid) during pregnancy causes Spina bifida (70%) Spina bifida comes in 2 forms:Spina bifida occulta milder form of Spina bifidathe dura mater remains intactcharacterized by the absence of the complete closure of the terminal process in the vertebraeSpina bifida cysticamore severedura mater is not properly closed, causing CSF & cauda equine to leak out, forming a bulge seen on the backif not removed surgically, it will result in paraplegiaParaplegia: paralysis of the lower limbs; causing the inability walksurgical removal involves draining the fluid, sealing/closing suture the opening of the wound as well as seal/close the dura materSpinal Cord Injury spinal cord injury results in 2 conditions:Paraplegia: paralysis of the lower limbs (legs)caused by the injury to the thoracic, lumbar & sacral part of the spinal cordQuadriplegia: paralysis in upper & lower limbs (arms & legs)

caused by the damage to the cervical part of the spinal cord