Brain Functions and Structure Overview |

1. Visual Anatomy & PhysiologyFirst EditionMartini & Ober Chapter 13 Brain and Cranial Nerves Lecture 20

2. Overview of the Brain • Functions • regulates visceral activities • coordinates muscular movements • interprets sensations • determines perception • stores memory • carries out reasoning • makes decisions • determines personality • Major Parts • cerebrum (twohemispheres) • diencephalon • thalamus • hypothalamus • brain stem • midbrain (mesencephalon) • pons • medulla oblongata • cerebellum

3. Protection of the Brain • The brain is protected • Mechanically by • The skull bones • The meninges • The cerebrospinal (CSF) fluid • Biochemically by the blood-brain barrier • Capillaries interconnected by tight junctions • Astrocytes/ependymal cells control permeability of general capillaries/choroid capillaries • May be obstacle to delivery of drugs • May become more permeable during stress

4. Meninges of the Brain Figure from: Hole’s Human A&P, 12th edition, 2010 - dura mater – outer, tough (anchoring dural folds) - arachnoid mater – web-like - pia mater – inner, delicate *Singular of meninges is meninx - Subdural space – like interstitial fluid - Subarachnoid space – CSF

5. Dural Folds Figure from: Martini, Fundamentals of Anatomy & Physiology, Benjamin Cummings, 2004

6. Ventricles of the Brain Figure from: Hole’s Human A&P, 12th edition, 2010 • interconnected cavities • within cerebral hemispheres and brain stem • continuous with central canal of spinal cord • filled with cerebrospinal fluid (CSF) • lateral ventricles (1, 2) • third ventricle (3) • fourth ventricle (4) • cerebral aqueduct

7. Cerebrospinal Fluid • secreted by choroid plexus of ventricles (~500 ml/day) • circulates in ventricles, central canal of spinal cord, and subarachnoid space • completely surrounds brain and spinal cord • clear liquid (more Na+ and Cl-, but less K+, Ca2+, glucose, and protein than plasma) • nutritive and protective • helps maintain stable ion concentrations in CNS Figure from: Hole’s Human A&P, 12th edition, 2010

8. Structure of Cerebrum • corpus callosum • connects hemispheres • gyri • bumps or convolutions • sulci • grooves • longitudinal fissure • separates hemispheres • transverse fissure • separates cerebrum from cerebellum • lateral sulcus • separates the frontal from the temporal lobes Figures from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

9. Functions of Cerebrum • interpretation • initiating voluntary movements • storing memory • retrieving memory • reasoning • center for intelligence and personality The cerebrum can be divided into several functional areas: - Motor(frontal cortex) - Sensory (parietal, occipital, and temporal cortex) - Association(all lobes) Points to keep in mind: - Each cerebral hemisphere receives information from, and sends information to, the opposite side of the body - Although symmetrical, the cerebral hemispheres are not entirely equal in function

10. Overview of Cerebral Cortex Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

11. Primary Motor Areas • Primary Motor Cortex - voluntary control of skeletal muscles Figure from: Hole’s Human A&P, 12th edition, 2010

12. Motor Areas of the Cortex Notice the relative amount of cortical tissue devoted to each motor function. What would this be proportional to? The Motor “Homunculus” ? Figures from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

13. Broca’s Area (Motor) • Broca’s Area • in one (dominant, usually left) hemisphere • controls muscles needed forspeech Figure from: Hole’s Human A&P, 12th edition, 2010

14. Frontal Eye Field (Motor) Controls voluntary movements of eyes and eyelids Figure from: Hole’s Human A&P, 12th edition, 2010

15. Sensory Areas • Cutaneous Sensory Area • parietal lobe • interprets sensations on skin • Visual Area • occipital lobe • interprets vision • Auditory Area • temporal lobe • interprets hearing Figure from: Hole’s Human A&P, 12th edition, 2010

16. Sensory Areas of the Cortex Notice the relative amount of cortical tissue devoted to each sensory function. The Somatosensory “Homunculus” Figures from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

17. Association Areas Figure from: Hole’s Human A&P, 12th edition, 2010 • regions of cortex that are not primary motor or primary sensory areas • widespread throughout the cerebral cortex • analyze and interpret sensory experiences; coordinate motor responses • memory, reasoning, verbalization, judgment, emotions

18. Hemispheric (Cerebral) Lateralization Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Categorical hemisphere Representational hemisphere

19. Basal Nuclei • nuclei are masses of gray matter in CNS • deep within cerebral hemispheres • caudate nucleus, putamen, globus pallidus (together called the corpus striatum) • subconsciouscontrol certain muscular activities, e.g., learned movement patterns Figure from: Hole’s Human A&P, 12th edition, 2010 Relay motor impulses originating in the cerebral cortex and substantia nigra of the midbrain.

20. Limbic System • Consists of • portions of frontal lobe • portions of temporal lobe • hypothalamus • thalamus • basal nuclei • other deep nuclei • associated with sense of smell (less significant) • Functions • controls emotions • produces feelings • interprets sensory impulses • facilitates memory storage and retrieval (learning!) Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 The motivational system

21. Memory • A “Memory” is the persistence of knowledge that can be accessed (we hope!) at a later time. • Memories are not stored in individual “memory cells” or neurons; they are stored as pathways called engrams, or memory traces that use strengthened or altered synapses. • Immediate memory lasts a few seconds, e.g., remembering the earliest part of a sentence to make sense of it. • Short-term memory (STM) lasts a few seconds to a few hours • Working memory is a form of this (repeating a phone number over to yourself just long enough to dial it – and then forget it!) • Limited to a few ‘bits’ of information (about 7-9). So, ‘chunk up’! • Long-term memory (LTM) can last a lifetime • Can hold much more information that STM • Declarative (events and facts) • Procedural (motor skills)

22. Diencephalon • between cerebral hemispheres and brainstem • surrounds third ventricle • thalamus • hypothalamus • epithalamus • optic tracts • optic chiasm • infundibulum • posterior pituitary • mammillary bodies • pineal gland (Tectum) Figure from: Hole’s Human A&P, 12th edition, 2010

23. Diencephalon • Thalamus • gateway for sensory impulses heading to cerebral cortex • receives all sensory impulses(except smell) • channels impulses to appropriate part of cerebral cortex and to the basal nuclei for interpretation • Hypothalamus • maintains homeostasis by regulating visceral activities • Heart rate and blood pressure- Body temperature - Water and electrolyte balance- Hunger and body weight- Movement/secretions of glands and intestines • Stimulation of the pituitary (links nervous and endocrine)- Sleep and wakefulness

24. Brain Stem Figure from: Hole’s Human A&P, 12th edition, 2010 • Three Parts • Midbrain • Pons • Medulla Oblongata (Tectum)

25. Midbrain • between diencephalon and pons • contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain • cerebral aqueduct • cerebral peduncles – bundles of nerve fibers • contains red nucleus (rubro-) and substantia nigra • corpora quadrigemina – centers for visual and auditory reflexes Major connecting center between spinal cord and brain and parts of brainstem (Tectum) Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

26. Pons Figure from: Hole’s Human A&P, 12th edition, 2010 (Tectum) • rounded bulge on underside of brainstem • between medulla oblongata and midbrain • helps regulate rate and depth of breathing • relays nerve impulses to and from medulla oblongata and cerebellum Ventral view Dorsal view

27. Medulla Oblongata • enlarged continuation of spinal cord • conducts ascending (olive) and descending (pyramids) impulses between brain and spinal cord • contains cardiac, vasomotor, and respiratory control centers • contains various nonvital reflex control centers (coughing, sneezing, vomiting) Figure from: Hole’s Human A&P, 12th edition, 2010 (Tectum) Ventral view Dorsal view

28. Reticular Formation • complex network of nerve fibers scattered throughout the brain stem • extends into the diencephalon • connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum • filters incoming sensory information; habituation • modulates pain • arouses cerebral cortex into state of wakefulness Figure from: Hole’s Human A&P, 12th edition, 2010 Ascending portion is called the ‘reticular activating system’(prefix = reticulo-)

29. Cerebellum • integrates sensory information concerning position of body parts • coordinates skeletal muscle activity • maintains posture • May also be involved in several sensory, linguistic, emotional and non-motor functions Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

30. Peripheral Nervous System You are here CNS PNS Figure from: Hole’s Human A&P, 12th edition, 2010

31. Peripheral Nervous System • Cranial nerves arising from the brain • Somatic fibers connecting to the skin and skeletal muscles • Autonomic fibers connecting to viscera • Spinal nerves arising from the spinal cord • Somatic fibers connecting to the skin and skeletal muscles • Autonomic fibers connecting to viscera

32. Cranial Nerves Paired. Numbered (roughly) in the order of their occurrence from anterior to posterior. Abbreviated using N or CN. Figure from: Hole’s Human A&P, 12th edition, 2010

33. The Cranial Nerves You should know this table

34. Cranial Nerves I and II • Olfactory (I) • sensory • fibers transmit impulses associated with smell Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 • Optic (II) • sensory • fibers transmit impulses associated with vision

35. Cranial Nerves III, IV, and VI • Abducens (VI) • primarily motor • motor impulses to the lateral rectus (LR) muscles that move the eyes • Oculomotor (III) • primarily motor • motor impulses to muscles that • raise eyelids • move the eyes • focus lens • adjust light entering eye • Trochlear (IV) • primarily motor • motor impulses to the superior oblique (SO) muscles that move the eyes What’s a ganglion? Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

36. Cranial Nerve V Figure from: Hole’s Human A&P, 12th edition, 2010 • Trigeminal (V) • both sensory and motor • opthalmic division • sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids • maxillary division • sensory from upper teeth, upper gum, upper lip, palate, and skin of face • mandibular division • sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip • motor to muscles of mastication and muscles in floor of mouth Major sensory nerve of face

37. Cranial Nerve VII • Facial (VII) • both sensory and motor • sensory from taste receptors • motor to muscles of facial expression, tear glands, and salivary glands • Major MOTOR nerve of face Figures from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

38. Cranial Nerves VIII and IX • Vestibulocochlear (VIII) • sensory • sensory from equilibrium receptors of ear • sensory from hearing receptors • Glossopharyngeal (IX) • both sensory and motor • sensory from pharynx, tonsils, tongue, and carotid arteries • motor to salivary glands and muscles of pharynx Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

39. Cranial Nerve X • Vagus (X) • both sensory and motor • somatic motor tomuscles of speech and swallowing • autonomic motor (parasympathetic) to viscera of thorax and abdomen • sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

40. Cranial Nerves XI and XII • Accessory (XI) • primarily motor • motor to muscles of soft palate, pharynx, larynx, neck, and back • Hypoglossal (XII) • primarily motor • motor to muscles of the tongue Figure from: Martini, Fundamentals ofAnatomy & Physiology, Pearson Education, 2004

41. Review • The brain is protected by the • Skull bones • Meninges • CSF • Blood-brain barrier • The meninges of the brain and spinal cord consist of the • Dura mater • Arachnoid (membrane) • Pia mater

42. Review • Important motor areas of cerebral cortex • Precentral gyrus (Primary motor area) • Broca’s area • Frontal eye field • Important sensory areas of cerebral cortex • Postcentral gyrus (Primary cutaneous sensory) • Visual area (occipital lobe) • Auditory area (temporal lobe)

43. Review Table from: Hole’s Human A&P, 12th edition, 2010

44. The Cranial Nerves