ANATOMY I, CHAPTER 12, CNS - BRAIN

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1 ANATOMY I, CHAPTER 12, CNS - BRAIN 2 Protection and coverings of brain Cranial meninges (menix): membranes that surround the brain and are continuous with spinal meninges. Three layers: dura matter, arachnoid matter & pia matter 1. Dura matter (tough mother) - thick outer periosteal layer (leather like) and a thinner inner meningeal layer 2. Arachnoid layer (spider web-like): diffuse middle layer 3 3. Pia Matter: Very thin inner layer that is attached to surface of the brain and follows brain contour. Between arachnoid layer and pia matter is the subarachnoid space which contains cerebrospinal fluid 4 Figure 12.24: page Brain- Largest and most complex portion of the nervous system 100 billion neurons. Embryological Development 1. At 3 weeks embryo develops a neural plate 2. Plate invaginates to form neural grove 3. Superior edges of grove fuse and form a neural tube. 4. Anterior portion of tube enlarges but constrictions divide it into 4 separate compartments that become ventricles 6. Figure: 12.1; pg Figure: 12.1; pg Figure: 12.1; pg Figure: 12.1; pg Figure: 12.2; pg

2 11 Cerebrospinal fluid: Fluid that circulates through and around the brain and spinal cord Ventricles (4): hollow spaces in brain filled with cerebrospinal fluid. Lateral ventricles: located in each hemisphere of the brain cerebrum (2) Third ventricle: Vertical slit in the midline Fourth ventricle: Lies in the hindbrain 12 About 500 ml of cerebrospinal fluid produced each day by the choroid plexus normally, that amount is reabsorbed into the veins. If restriction occurs the presure builds up. Head swells in newborns. Cerebrospinal fluid acts as a cushion and floats the brain Serves as a source of safe nutrients, oxygen and removal of wastes 13 Figure: 12.26; pg. 462 CSF Circulation 14 Figures 12.5a&b; pg.433 ventricles Figure: 12.27; pg. 463 Hydrocephalus 17 Brain is divided into 4 main sectiond: Cerebrum, Diencephalon, Brain stem, & Cerebellum Cerebrum largest part of the brain consisting of two cerebral hemispheres and separated by a longitudinal fissure (deep grove) 83% of brain mass Both halves are connected by nerve fibers called corpus callosum 18 Cortex executive suite where conscious mind is found outer 1/8 inch 40% of brain mass Two layers: outer gray matter; inner white matter The cortex has gyri/gyrus (elevated ridges or convolutions) and sulci/sulcus (shallow groves) 19 Figure 12.6, Pg Figure 12.6 a, Pg, Figure: 12.6a, pg. 436 corpus callosum 2

3 22 Cortex divided by prominent sulci, into 5 lobes named according to overlying cranial bones Central sulcus separates the frontal and parietals(2) Parirtals(2) seperated from occipital by the occipital sulcus Temporal lobes(2) separated from frontal & parietals bt the lateral sulcus Fifth lobe, insula*, is buried deep within the lateral sulcus 23 Figure: 12.6a; pg Figure 12.6c: pg Fig b: pg Cortex contains 3 kinds of functional areas: 1. Motor, sensory & association areas 2. Each hemisphere is concerned w/ motor & sensory function of the contralaretal (opposite) side of the body (ipsilateral same side) 3. Function not totally equal bilaterally some specialization left vs. right 4. Areas are never totally autonomous always some carry over 27 Digress: Nuclei: mass of neurons (cell bodies) in CNS Ganglia: mass of neurons (cell bodies) in PNS 28 Primary motor (somatic) cortex Found in precentral gyrus of frontal lobe Conscious control of voluntary (skeletal) muscles Contains large pyramidal cells* with long pyramidal tracts* (corticospinal tracts) to. the spinal cord Control of specific body structures are controlled by pyramidal cells in a particular. Region of the primary motor cortex Somatopy: mapping of regions 29 Figure: 12.8 a; Pg

4 30 Figure 12.9; pg. 438 (motor homunculus) 31 Diencephalon: Central core of brain three parts Thalamus, hypothalamus & epithalamus Thalamus: (inner room) deep in middle of brain Superior walls of the third ventricle Relay station for information coming into the cerebral cortex sensory, emotional, visceral sent to proper area of the cerebrum Hypothalamus: Below the thalamus inferior walls of the third ventricle main visceral control center and subsequently controls body homeostasis 32 Infundibulum: Stalk of hypothalamus that connects to pituitary gland Mammillary bodies: pea shaped nuclei that relay impulses from olfactory (smell) sense ROLES of hypothalamus 1. Autonomic NS control blood pressure, heart rate, pipil size 2. Cenetr for emotonal response 3. Body temperature 4. Food intake regulation Regulation of sleep-wake cycles 6. Control endocrine (hormone) system Epithalamus: most dorsal aspect of diencephalon posterior boarder includes pineal gland/body produces melatonin, a sleep inducing hormone 34 Figure: 12.12; pg Limbic System: Group of structures located on the medial aspect of the cerebelum and the diencephalon It s our emotional aspects of behavior or feelings relating to survival, pleasure, pain & memory Two important parts: amygdala & anterior cigulate gyrus amygdala: recognizes angry or fearfull facial expressions cigulate gyrus: plays role in expressing emotions and resolving mental conflict 36 Figure: 12.18; pg. 452 limbic system 4

5 37 Brain stem: Rigidly programmed automatic behaviors necessary for survival contains all cranial nerves except I & II Includes: midbrain, pons & medulla oblongata Midbrain: located between diencephalon and pons. Contains the cerebral aquaduct Cerebral peduncles: paired fibers in ventral portion, connecting upper parts of brain w/ spinal cord 38 Figure: 12.15a; pg. 446 cerebral peduncles 39 Tectum: dorsal protion corpora quadrigemina: four, dorsal dome-like protrusions. 2 Superior colliculi: are reflex centers for eyes, head & neck movement from visual stimuli. 2 Inferior colliculi: reflex centers for head and trunk from sound stimuli Cerebral peduncles: (dorsal view) 40 Figure:12.15c dorsal corpora quadrigemina 41 Substantia nigra: near cerebral peduncles control subconscious movements Red nucleus: Ending place for fibers from cerebellum and cerebral cortex 42 Figure:12.16a;pg. 448 red nucleus& substntia 43 Pons: Neural bridge between brain and spinal cord - Bulging portion of brain stem between midbrain & medulla oblongata Pneumotaxic area & Apneustic area : nucleui in pons that controls breating 44 Figure: 12.15b; pg. 446 pons lateral 45 Medulla oblogata: Communication w/ superior spinal cord Pyramids- ventral bulges w/ motor tracts from pyramid cells in motor cortex to spinal cord decussation of pyramids: region where motor tracts cross to opposite sides. 46 Figure: 12.15a; pg. 446 ventral pyramid/decus 5

6 47 Cerebellum: processes input from cerebral cortex, brain stem nuclei and sensory receptors to provide precise timing, patterns of muscle contraction for smooth coordinated movement Two bilaterally symmetrical, apple sized hemispheres connected medially by a worm shaped vermis Surface has pleat-like gyri called folia (leaves) Deep fissures divide the cerebellum into a anterior, posterior and flocculonodular lobes 48 Anterior and posterior lobe function in subconscious movement Flocculonodular lobe, on inferior surface, functions in sense of equilibrium (balance) 49 Figure 12.17; pg. 451 cerebellum 50 Cerebellar cortex: outer layer of gray matter Arbor vitae: Inner white matter that has a tree-like appearance so, gray matter reaches deep into white matter. 3 Cerebellar peduncles Inferior cerebellar peduncle: connects cerebellum to medulla oblongata middle cerebellar peduncle: connects cerebellum to pons Superior peduncle: connects cerebellum to midbrain 51 Figure: 12.17a&b; pg Figure: 12.17a&b; pg