Notes

Outline

PowerPoint Presentations PowerPoint Contents Page

The Central Nervous  System Brain and Spinal Cord Chapter 12

Anatomy of CNS Central Nervous System (CNS)  Hollow tube, folded anteriorly Formed of two parts, joined and function together Brain Spinal Cord

Brain anatomy Five anatomical regions formed during embryological development Telencephalon, Diencephalon, Mesencephalon, Metencephalon, & Myelencephalon

Slide 5

Brain anatomy AKA Cerebrum, diencephalon, brain stem (midbrain,, pons, and medulla oblongata) cerebellum  Hollow--4 ventricles

Slide 7

Ventricles Hollow cavities in brain lined with ependymal cells and CSF lateral (I and II)-cerebral hemispheres third (III) in diencephalon fourth (IV) between pons & medulla continuous with central canal of spinal cord

Slide 9

Anatomy of Cerebrum Twin hemispheres, R & L Hollow, ventricles 1 and 2 Wrinkled, with sulci (grooves) & gyri (ridges) on surface Divided by fissures Regional lobes named for skull bones overlying each region

Cerebral lobes Frontal lobe Parietal lobe Temporal lobe Insula Occipital lobe Separated by sulci--central, lateral and parietal-occipital sulcus

Anatomy of Cerebrum Brain regionalized internally into gray and white matter Gray matter in outer layer (cortex) and inner clusters (basal nuclei) White matter consists of tracts connecting the cortex and nuclei; corpus callosum connects cerebral hemispheres

Slide 13

Cerebral cortex Area of consciousness composed of gray matter contains motor, sensory and association areas, contralateral some specialization per side no functional area acts alone, all contribute to behavior

Cerebral lobes, cont Frontal lobe-primary somatic motor area, conscious thought, etc Precentral gyrus--primary motor area Premotor cortex--learned skills Broca’s area--motor speech area Prefrontal area--intellect and abstract thought

Slide 16

Cerebral lobes, cont Parietal lobe-primary somatic sensory area in postcentral gyrus Gustation Temporal lobe-Auditory and olfactory Occipital lobe-Visual

Slide 18

Association areas All lobes of cerebrum have association areas which interrelate the interpretation of senses in each lobe. Gnostic area--left side temporal, parietal, and occipital lobes Language area? Wernicke’s area

Lateralization One hemisphere often dominates Left--language, math, logic Right--visual-spatial skills some learning disabilities are due to failure to develop a dominant hemisphere

Cerebral white matter Myelinated axons-tracts Commisure-connect two common areas of both hemispheres corpus callosum Association fibers-connect lobes on same side of hemisphere Projection fibers-to or from lower areas of brain and spinal cord

Slide 22

Slide 23

Basal nuclei (centers) Several structures (corpus striatum and amygdala) Receive input from all areas of cortex and interconnect influence primary motor cortex not well understood synchronizes movement

Slide 25

Slide 26

Diencephalon Like a small room with a narrow, slit-like ventricle (III) a thin roof (epithalamus) thick side walls (thalamus) and a thick floor (hypothalamus)

Slide 28

Thalamus Form sides of “room”, or walls of third ventricle; intermediate mass connects lateral walls Receive and process sensory (all) information coming to cerebral cortex, attach emotions ;) or :( Mediates emotional response, cortical arousal, learning & memory

Epithalamus Roof of diencephalon, with two structures Pineal gland--an endocrine gland which secretes melatonin--influences diurnal cycle and perhaps other biorhythm (repro?) choroid plexus--secretes CSF

Hypothalamus Floor of diencephalon attached to pituitary gland at ventral side by infundibulum, penetrated by 3rd ventricle Major player in your life--main homeostatic center, direct contact with blood; monitors everything, secretes hormones

Hypothalamus Autonomic control center Center for emotional response Regulates body temperature Hunger and thirst centers Regulates sleep cycle Controls endocrine system through hormones to pituitary

Slide 33

Brain stem Three parts to this central mass Midbrain Pons Medulla oblongata Much of this consists of tracts running to/from cerebrum and diencephalon, but also Contains important centers

Slide 35

Slide 36

Midbrain Ventral side mostly wiring Cerebral aqueduct runs centrally Dorsal surface has two major structures (Corpora quadrigemina) Superior colliculi--visual reflexes Inferior colliculi--auditory reflexes Substantia nigra, red nucleus Reticular formation centers

Pons Contains longitudinal ascending and descending fibers to higher centers and spinal cord Contains transverse connections to tracts and to cerebellum Center for  respiration (pneumotaxic center)

Medulla Oblongata Contains longitudinal ascending and descending fibers to higher centers and spinal cord Pyramids-tracts cross over to other side (decussation) Centers for respiration, heart rate, cough, sneeze, swallow Autonomic reflex center

Cerebellum Hemispheres joined by vermis, arbor vitae of white matter Processes input from motor cortex, brain stem nuclei, and sensors Coordinates timing of precise learned muscle patterns--”grooved” golf swing, typing, etc.  Place where athletes store their learned motor skills without conscious control

Functional systems Limbic system: cerebral and diencephalon structures for ring around upper brainstem Emotional system coordination with thoughts Many important structures including hippocampus and amygdala

Slide 42

Functional systems Reticular formation: Extends through brainstem, loose and farflung neurons, into cerebral cortex Reticular activating system-alertness Filters out repetitive or familiar stimuli Inhibited by sleep, alcohol, drugs Severe injury--coma

Slide 44

Brain protection Cranium Meninges Cerebrospinal fluid )CSF) Blood-brain barrier

Meninges Dura mater Arachnoid Pia mater

Dura mater Tough, collagenous membrane 2 layers, outer fused to periosteum and inner meningeal, space between is sinus for cranial venous blood 3 septa in fissures Falx cerebri Falx cerebelli Tentorium cerebelli

Slide 48

Slide 49

Arachnoid A thin transparent middle membrane, covering surface broadly Subdural and subarachnoid spaces Web of extensions to pia mater CSF and blood vessels in sub-arachnoid space villi protrude into dural sinuses

Pia mater Thin delicate membrane tightly covering brain Invested with tiny blood vessels Follows the gryi and sulci of brain surface Meningitis--encephalitis--inflammation meninges, bacterial or viral infection

Cerebrospinal Fluid Liquid cushion around brain, nourishes brain Filtrate of plasma, no proteins, has different  ion and molecule concentr’n Formed in choroid plexus in brain Ependymal cells filter plasma into ventricles About 150 ml, renews every 3-4 hours

Cerebrospinal Fluid, cont CSF moves down ventricles into cord central canal, out through holes in 4th ventricle into subarachnoid space arachnoid villi protrude into dural sinuses, CSF recovered into blood Hydrocephalus caused by blockage of holes in 4th ventricle

See figure 12-24 a & b

Blood-Brain Barrier Capillaries of brain have thick basal lamina, tight junctions, don’t leak Along with astrocytes, prevent all blood-borne materials from reaching neurons Fat soluble materials penetrate Hypothalamus not so protected, monitors blood condition

Brain injuries Coup/countercoup Concussion Contusion Hemorrhage Cerebral edema Cerebrovascular accident--TIA/stroke Degenerative disorders

Spinal cord Extends from medulla oblongata to   L-1 or L-2 vertebrae about 17-18 “ long, 3/4 “ thick 2-way path to brain,  reflex center Protection- vertebrae, meninges, CSF Meninges extend to S-2, spinal tap cord tapers to conus medullaris meninges anchor to vertebrae

Slide 58

Slide 59

Spinal cord, cont Cord has 31 segments, each marked by pair of lateral nerves Nerves emerge between vertebrae Cord has two swollen areas-cervical and lumbar enlargements Ends in cluster of nerves called cauda equina (pony tail)

Slide 61

Spinal cord, section Two grooves-dorsal sulcus, ventral fissure Gray and white matter Spinal rootlets form dorsal and ventral roots, fuse to form spinal nerves Central canal is hollow, contains CSF

Slide 63

Gray matter H-shaped configuration with dorsal (posterior) and ventral (anterior) horns, lateral horns Represent cell bodies of neurons Anterior horns--motor neurons Posterior horns--sensory neurons sides joined by gray commisure

Slide 65

White matter Myelinated and unmyelinated axons that communicate with other parts of nervous system Ascending-toward brain Descending-from brain Transverse-commisural Three columns-funiculi ant, post, lat

Tracts  of White matter Mulitneuronal pathways between brain and body Consist of 2-3 neurons in chain Paired laterally Somatotopy-mapping Decussation-cross over right to left

Ascending tracts Carry sensory info upward Six major pathways, 4 are to cortex for conscious interpretation Posterior funiculus (2) touch Lat and ant spinothalamic-pain, temp Ant and post spinocerebellar-muscle proprioception, not conscious

Descending tracts Carry motor info down; two neurons Two major groups Pyramidal--direct pathway Ant and lat corticospinal tract Other (extrapyramidal) indirect Rubrospinal, vestibulospinal, reticulospinal, and tectospinal