CNS: The BRAIN HA&P

1. CNS: The BRAIN HA&P Male – 3.5 lbs; Female – 3.2 lbs Brain mass: body mass is equal!

2. Embryonic Development • 3 weeks old – neural plate forms from ectoderm , and invaginates to form neural grove which deepens to form theneural tube by week four • Neural tube sinks deeper away from ectoderm and differentiates into brain anteriorly and spinal cord develops caudally • Central cavity of neural tube enlarges to form ventricles

4. Embryonic Brain Development

5. Space Restriction on Brain Development • Flextures develop bending forbrain towards brain stem • Cerebral hemispheres grow posteriorly and laterally enveloping diencephalon & midbrain • By 26th week cerebral hemispheres form convolutions to increase SA (more neurons to occupy limited space)

6. Regions of the Brain • Cerebral Hemispheres • Longitudinal fissure seperates R/L Hemisperes • 4 Lobes: Frontal, Parietal, Occipital, and Temporal • Motor, Sensory, and Cognitive Functions • Diencephelon • Thalmus, Hypothalmus, and Epithalmus • Brain Stem • Medulla Oblongata, Pons, Midbrain • Cerebellum • Subconscious coordinated movement and agility

7. Protection of the Brain • Bone • Meninges • 3 connective tissue membranes • Protect bv • Contain CSF • Cerebral spinal Fluid (CSF) • Blood Brain Barrier

8. Meninges • Dura Mater (tough mother) • 2 layers of strong fibrous connective tissue • Periosteal layer connects to periosteum of skull • Subdural space • Arachnoid (spider) • Middle loose brain covering • Subarchnoid space • w/weblike extensions that attach to the pia mater • Filled w/CSF • Large bv to brain • Pia Mater (gentle mother) • Delicate connecctive tissue • Rich w/tiny bv • Clings to brain following convolutions

9. What is meningitis? • Inflammation of meninges • Bacterial or viral infection • Diagnosed by a lumbar spinal tap • All of the above

10. Cerebral Spinal Fluid • Liquid Cushion from blows and trauma • Buoyancy reduces brain weight by 97%! • Provides nourishment (similar to blood plasma) • Abundant Na+, Cl-, H+, Less Ca2+ and K+ • Formed by choroid plexus (clusters of cappillaries) @ roof of ea/ventricle (ependymal cells) • Adults – 500mL produced daily, 150mL replaced ea/8 hrs • Removes waste products • Circulates through ventricles to central canal of spinal cord and subarachnoid space

11. Ventricles • Continues w/ea other & central canal of spinal cord • Lateral ventricles (pair) • 3rd ventricle • 4th ventricle • Cerebral aquaduct

12. Blood-Brain Barrier • Maintains stable environment for the brain • Capillaries are the least permeable in the body (tight junctions) • Selective • Glucose, a.a., some electrolytes move by facilitated diffusion • Bloodbourne metabolic wastes, proteins, some toxins, and most drugs are denied entry • Ineffective against fats, fatty acids, O2, CO2, alcohol, nicotine, anesthetics • Incomplete in newborn and premature • Lack of brain barrier in hypothalmus and brain stem (moniter blood, toxins, and vomiting reflex!)

13. The ___________ is the outermost meninx, and forms supportive and protective partitions between some portions of the brain. • Dura mater • Arachnoid • Pia mater • Ventricles • Blood brain barrier

14. Cerebral Hemispheres • 83% of total brain mass! • Gyri – elevated ridges • Sulci – shallow grooves • Fissures – deep grooves • Anatomical landmarks divide cerebrum into 5 lobes • Longitudinal fissure • Transverse cerebral fissure • Central sulcus • Lateral sulcus • Each hemisphere has 3 regions • Cortex – superficial gray matter • Internal white matter • Basal nuclei – islands of gray matter deep within white matter

15. Cerebral Cortex • Conscious mind • Gray matter: neuron somas, dendrites, glia, and bv • 2-4 mm but 40% of brain mass due to convolutions • Billions of neurons in 6 layers • Ea/hemisphere is concerned w/sensory & motor functions of opposite side of body • Divided into localized domains w/specific functions • Motor – control voluntary movements • Sensory – conscious awareness of sensation • Association – receiving input from multiple senses and sending output to multiple areas (complex connections)

17. Motor Areas • Primary motor cortex • Precentralgyrus of frontal lobe of ea/hemisphere • Skilled voluntary movements of skeletal muscles • Premotor cortex • Anterior to precentralgyrus • Learned motor skills of patterned nature (playing a musical instrument) • Coordinates several muscle groups • Broca’s area • Anterior to inferior region of premotor area • Usually only in left hemisphere • Motor speech area (directs muscles used in speech) • Frontal eye field • Anterior to premotor cortex and superior to Broca’s area • Controls voluntary movements of eyes

18. Sensory Areas • Primary Somatosensory cortex • Postcentralgyrus of parietal lobe • Receive information from sensory receptors in skin • Neurons identify body region being stimulated (opposite sides of body correlate w/hemispheres) • Somatosensory Association cortex • Posterior to primary somatosensory cortex • Integrates sensory inputs to understand object being felt • Visual Areas • Extreme posterior tip of occipital lobe & buried deep in medial occipital lobe • Receives visual info from retina of eye • Auditory Areas • Superior margin of temporal lobe

19. Sensory Areas cont’d • Olfactory Cortex • Medial aspect of temporal lobe • Olfactory tracts from superior nasal cavities • Gustatory Cortex • Insula (deep to the temporal lobe) • Perception of taste • Visceral Sensory Area • Cortex of insula posterior to gustatory cortex • Stomach pains, full bladder, lungs bursting, etc… • Vestibular (equilibrium) cortex • Posterior region of insula, deep to temporal lobe • Awareness of balance and your place in space

20. Multimodal Association Areas • Anterior association area • AKA pre-frontal cortex (frontal lobe) • Intellect, cognition, recall, personality, abstract ideas • Judgement, reasoning, persistence & planning • Matures slowly • Posterior association area • Large region of temporal, parietal, and occipital lobes • Recognizing patterns, faces • Wernicke’s Area – understanding written and spoken language • Limbic association area • Cingulategyrus, parahippocampalgyrus, and hippocampus • Emotional impact & memories

21. Are you Left or Right Brained?

22. Lateralization of Cortical Functioning • Both cerebral hemispheres are used for almost every activity, however there is some division of labor • 90% of people have left hemisphere dominance • Meaning left hemisphere has greater control over language abilities, math and logic • And the right hemisphere is associated with intuition, emotion, artistic and musical skills, poetic, creative, and far better at recognizing faces • Typically right handed • 10% of people the roles of hemispheres is reversed or shared equally • Typically left handed and male

23. Cerebral White Matter • Responsible for communication between cerebral areas and between cerebral cortex and lower CNS centers • Myelinated fibers bundled into large tracts • Commissures • connects gray areas of two hemispheres (horizontal) • Corpus Callosum–largest (superior to lateral vesicles) • Association Fibers • Connect different parts of same hemisphere (horizontal) • Projection Fibers • Connect cortex to bodys receptors and effectors • vertical

24. Diencephalon • Central Core of forebrain • 3 paired structures • Thalmus • Hypothalamus • Epithalmus

25. Thalamus • 80% of diencephalon • Large number of nuclei • Gateway to cerebral cortex • Afferent impulses from all senses converge • Information is sorted and relayed to appropriate area of cortex • Crude recognition as pleasant or unpleasant

26. Hypothalamus • Below the thalamus, above brain stem • Extends from optic chiasmato mammilary bodies (nuclei that relay olfactory pathways) • Infundibulum connects to pituitary gland • Visceral control center of body, vital for homeostatic control

27. Homeostatic Roles of Hypothalamus • ANS • Influences hr, bp, pupils, etc • Emotional response (limbic system) • Perception of pleasure, fear, rage, and sex drive • Body Temperature regulation • Monitors & initiates sweating or shivering • Regulation of food intake • response to changes in blood glucose/a.a., hormones • Regulation of water balance and thirst • Response to concentrations of bodily fluids • Regulation of sleep wake cycles • In response to light (visual) cues • Endocrine system functioning • Controls secretions of pituitary gland • Produces hormones ADH and oxytocin

28. Epithalamus • Dorsal portion of diencephelon, roof of 3rd ventricle • Pineal gland extends from posterior border • Helps regulate sleep wake cycle

29. Brain Imaging • Compare PET, fMRI, CAT, EEG, cerebral angiography

30. Brain Stem • Survival Behaviors • Pathway for fiber tracts • Innervation of the head • 3 parts: • Midbrain • Descending motor tracts • Cerebral aqueduct (connects 3rd & 4th ventricles • Visual reflex centers • Sound (startle)reflex • Pons • Bulging region • Deep tracts connect brain and spinal cord • Superficial fibers connect motor cortex and cerebellum • Help medulla maintain breathing rhythm • Medulla Oblongata

31. Medulla Oblongata • Motor cortex fibers cross over to opposite side of body before spinal cord • Relay sensory information • Auditory relays • Maintains equilibrium • Autonomic reflex center • Force and rate of heart contraction • Vasomotor center • Rate and depth of breathing • Vomiting, hiccupping, swallowing, coughing, sneezing

32. Cerebellum • 11%of total brain mass • Dorsal to pons & medulla • Using input from cerebral motor cortex and sensory receptors provides precise timing of skeletal muscle contraction subconsciously • Smooth coordinated movements • Agility

33. Brain Activities: • Limbic System • Reticular Formation • Sleep • Language • Memory • Brain wave patterns and EEG Each group will create a brief (8 ppt slides) presentation w/pictures on their assigned brain topic of interest! You may use textbooks or internet, be sure to cite sources!

34. Cranial Nerves