Hollow spaces in the brain termed ventricles. CSF is produced and circulated (lined with ependymal cells) Lateral ventricles (2) separated by a thin membrane called the septum pellucidum. (CSF produced in the choroid plexus) Each lateral ventricle communicates with the third ventricle via a channel called an interventricular foramen (foramen of Monro)
Third ventricle is continuous with the fourth ventricle via the cerebral aquaduct of Sylvius Fourth ventricle drains CSF into spinal cord through the foramen of Magendie.
Cerebral Hemispheres Superior part of the brain Covered entirely by ridges (gyri), separated by shallow grooves (sulci) and deeper called grooves (fissures) Anatomical landmarks: –Longitudinal fissure –Frontal, parietal, occipital, and temporal lobes Deep to temporal, parietal, and frontal lobes is a fifth lobe called the insula –Central sulcus of Rolando –Pre/post central gyri –Lateral sulcus of Sylvius –Calcarine sulcus –Parito-occipital sulcus –Transverse cerebral fissure
Cerebral Cortex: Seat of consciousness. Cerebral cortex contains three functional areas: 1- Motor areas - control voluntary motor function 2- Sensory areas - provide for conscious awareness of sensation 3- Association areas - integrate all other information Each hemisphere is concerned with the sensory and motor functions of the opposite side of the body
Motor regions are located in the posterior frontal lobe. Primary motor cortex - precentral gyrus in the frontal lobe - Large neurons (pyramidal cells) allow conscious control of movement of skeletal muscles -The pyramidal cells' long axons from voluntary motor tracts called pyramidal (corticospinal) tracts -Motor areas have been spatially mapped = somatotropy. (Homunculis)
Premotor cortex - anterior to the precentral gyrus in the frontal lobe. Regions controls learned motor skills that are repeated or patterned. Also coordinates the movements of muscles simultaneously and\or sequentially by sending activating impulses to the primary motor cortex.
Broca's area - anterior to the premotor area - Involved in directing motor speech.
Frontal eye field - anterior to the premotor cortex and superior to Broca's area Frontal eye field - anterior to the premotor cortex and superior to Broca's area Controls voluntary movement of eyes.
Sensory Areas (parietal, temporal, and occipital lobes) Primary somatosensory cortex - postcentral gyrus of parietal lobe (immediately behind primary motor cortex) –Neurons receive info (from sensory receptors, skin, and muscles) and identifies body region being stimulated Somatosensory association area - lies posterior to the primary somatosensory cortex –Integrate and analyze somatic sensory inputs (e.g. temperature and pressure) into comprehensive evaluation.
Visual areas - occipital lobes contain primary visual cortex (receive information from retina) and visual association area (interprets information from retina). Auditory areas - temporal lobes contain primary auditory cortex (receives impulses from inner ear) and auditory association area (interprets sound).
Olfactory cortex - temporal lobe in region called the uncus; enables conscious awareness of odors. “Skunkus in my uncus” Gustatory cortex - parietal lobe deep to temporal lobe; involved in perception of taste.
Association Areas Somatosensory cortex - posterior to the primary somatosensory cortex –The association areas, in turn, communicate with the motor cortex and with other sensory association areas to analyze, recognize, and act on sensory inputs.
Prefrontal cortex - anterior portions of frontal lobe - Involved with intellect and complex learning (cognition) and personality - Tumors may lead to personality disorders - prefrontal lobotomy are performed in severe cases of mental illness. Alzheimer’s Disease
Language areas - found in Wernicke's area of temporal lobe of one hemisphere (usually left) - Involved in interpretation of language.
Cerebral White Matter: - Responsible for communication within the brain between each hemisphere, cerebral cortex and lower CNS centers. - White matter bundled into large tracts - Fibers and tracts are classified according to the direction in which they run.
Commissural - Connects the gray areas of both hemispheres so the brain functions as one unit - Corpus callosum: superior to the lateral ventricles - Fibers run horizontal Association fibers: - Connect within the same hemisphere. - Connects adjacent gyri and different lobes. - Fibers run horizontal
Projection fibers: - Connects cortex to lower brain centers (spinal cord and brain stem). - Fibers run vertical - Internal capsule and corona radiata
Basal nuclei: (cell bodies) ganglia: Receive extensive input from the entire cerebral cortex and project messages (via relays) to the premotor and prefrontal cortices Amygdala: hangs off of the tail of the caudate nucleus. Center for fear.
Diencephalon (thalamus, hypothalamus) Thalamus: - Gray matter areas enclose the third ventricle. - Receive and projects fibers from the cerebral cortex. - All senses (afferent) from the body will pass through the thalamus (relay center). Senses are then sorted out - Gateway to the cerebral cortex
Hypothalamus: - Walls of hypothalamus (tissue) meet and extend, forming infundibulum (stalk), connecting the pituitary to base of hypothalamus. - The hypothalamus is the main visceral control center of the body. Homeostatic roles: 1- Autonomic control center - regulates involuntary nervous system activity (influences BP, HR, GI motility, Respiration rate and depth, and pupil size).
2- Center for emotional response and behavior - numerous connections with cortical association areas (initiates physical expressions of emotion). 3- Body temperature regulation - hypothalamus neurons monitor blood temperature flowing through hypothalamus (initiates sweating, shivering, etc.). 4- Regulation of food intake - responds to hormones and blood levels of nutrients. (hunger; satiation)
5- Regulation of water balance and thirst - triggers ADH release, causing kidneys to retain water; thirst centers stimulated, cause us to drink. 6- Sleep-wake cycle regulation - set timing of our sleep cycle in response to daylight-darkness cues. 7- Control of endocrine system - hypothalamus produces releasing hormones that control the secretion of anterior pituitary hormones
Brainstem: - Gray matter surrounded by white matter - Controls automatic functions necessary for survival (cardiac, breathing, digestion, head and eye movement) - Composed of the - midbrain - pons - medulla oblongata
Midbrain: Structures: Cerebral peduncles - pyramidal motor tracts descending toward spinal cord. Cerebral aqueduct - connect 3rd and 4th ventricle, enclosed by nuclei Nuclei - corpora quadragemina (two pair) –Superior colliculi (visual reflex, head/eye movement) –Inferior colliculi (auditory relay, startle reflex) Also embedded in white matter of midbrain are two pigmented nuclei Substantia nigra (site of dopamine production) and red nucleus (contains iron & hemoglobin and coordinates muscular movements: limb flexion). and red nucleus (contains iron & hemoglobin and coordinates muscular movements: limb flexion).
Classes of Neurotransmitters: Acetylcholine: excitatory (skeletal muscle) Biogenic amines –Dopamine, Norepinephrine, and epinephrine (feel good catecholamines) –Serotonin: inhibitory –Histamine Amino acids –GABA (gamma-aminobutyric acid) (inhibitory) –Glutamate: excitatory Peptides –Endorphins and enkephalins: inhibitory (opioids)
Pons: - between midbrain and medulla oblongata - between midbrain and medulla oblongata - Conduction pathway between higher and lower brain centers - Conduction pathway between higher and lower brain centers - Middle cerebellar peduncles connect pons with the cerebellum - Middle cerebellar peduncles connect pons with the cerebellum - Some pons nuclei (pneumotaxic) are respiratory centers that help maintain normal rhythm of breathing. - Some pons nuclei (pneumotaxic) are respiratory centers that help maintain normal rhythm of breathing.
Medulla Oblongata: - most inferior part of brain stem, blends into spinal cord at the level of the foramen magnum. Structures: - Pyramids - pyramidal tracts descending from motor cortex - Decussation of pyramids - fibers of pyramids cross over at one point; supporting that each hemisphere controls voluntary muscles - Olives - lateral to pyramids, relay sensory information on the state of stretch of our muscles and joints to the cerebellum
Medulla oblongata contains visceral motor nuclei that control: Medulla oblongata contains visceral motor nuclei that control: 1- Force and rate of heart contraction 2- Regulate BP (by regulating smooth muscle respiratory contraction) 3- Rate and depth of breathing, therefore maintain respiratory rhythm 4- Vomiting, hiccupping, swallowing, coughing, and sneezing
Cerebellum: “little brain”. Processes inputs from the cerebral motor cortex, brainstem nuclei, and sensory receptors to provide precise timing and patterns of skeletal muscle contraction. Coordinated movements such as driving and playing the piano. Controls equilibrium. - Composed of two cerebellar hemispheres connected by the vermis
- Transverse gyri (pleated) called folia. - Pattern of white matter inside resembles a branching tree; arbor vitae. - Contains posterior and anterior lobes that regulate subconscious skeletal. Cerebellar Processing: 1- Initiates voluntary muscle contraction 2- Determines body orientation (body parts in space) 3- Coordinates forces, direction, extent of muscle contraction
Limbic system: Complex group of fiber tracts that form a ring around the brainstem Part of the brain that is associated with emotions, pleasure, pain, fear, memory, anger, rage, sorrow and sex drive. Smell is tied in with memory Amygdala: fear Hippocampus: memory
Meninges (PAD): connective tissue that covers the brain and spinal cord 1- Pia mater: contacts brain surface and is found within the fissures and sulci 2- Arachnoid: separated from pia mater by subarachnoid space
3- Dura mater (tough mother): double membrane surrounding brain. A- Periosteal layer - attached to skull B- Meningeal layer - deep to periosteal, outermost brain covering; extends inward to form flat septa that anchor brain to skull: –Falx cerebri (in longitudinal fissure) –Falx cerebelli (runs along vermis of cerebellum) –Tentorium cerebelli (in transverse fissure)
Spinal Cord: runs through the vertebral foramen. Begins at the foramen magnum and ends at the level of L2. - Cervical and lumbar enlargements - Anterior median fissure and posterior median sulcus - Conus medullaris (L1-L2), cauda equina, and filum terminale - 31 pairs of nerves each two points of attachment called roots (dorsal and ventral)
- Interior gray matter (cell bodies) surrounded by white matter (myelinated neurons) - Central canal (continuous with the fourth canal) - Gray matter divided into horns: anterior, posterior, and lateral - White matter divided into columns: anterior, posterior, and lateral - Each white column contains bundles of nerve axons (called tracts) having a common origin or destination - Two types of tracts: ascending (sensory) and descending (motor)
Major spinal cord tracts: Corticospinal: descending motor tract that transmits motor impulse from cerebral cortex down spinal cord out to skeletal muscle Spinothalamic: ascending sensory tract that transmits pain, temperature and deep pressure.