Lab Activity 21

1. Lab Activity 21 The Brain Portland Community College BI 232

2. Brain Meninges: Dura Mater • Continuous with the spinal meninges • Dura mater: An outer and inner fibrous connective tissue • Outer later is fused to the periosteum of the cranial bones (no epidural space) • Between the layers are tissue fluids, blood vessels and venous sinuses. • Venous sinuses are large collecting veins. • Venous sinuses drain into the internal jugular veins

3. Dural Folds • The inner layer of dura mater that extends into the cranial cavity. • Provide additional stabilization and support for the brain • Contain the dural sinuses

4. Dural Folds • Falx cerebri projects between the cerebral hemispheres in the longitudinal fissure • Superior sagittal sinus & inferior sagittal sinus • Tentorium cerebelli separates the cerebellar hemisphere from the cerebrum • Transverse sinus • Falx cerebelli divides the cerebellar hemispheres

6. Brain Meninges: Arachnoid & Pia Mater • Arachnoid mater consists of the arachnoid membrane and fibers of the arachnoid trabeculae that attach to the pia mater • Pia mater: attached to the surface of the brain, anchored by processes of astrocytes • Contains branches of cerebral blood vessels that penetrate the surface of the brain. • CSF is between these two membranes in the subarachnoid space

7. Ventricles

8. CSF Circulation • CSF is made from tufts of blood capillaries called choroid plexuses • CSF cushions and provides buoyancy to the brain.

9. CSF circulation • CSF flows through the arachnoid granulations under the dura mater and returns to venous sinuses returning the fluid to the cardiovascular system.

10. Blood Supply to the brain • Blood vessels supply the brain with nutrients and oxygen. • The two main arteries are the vertebral arteries and internal carotid arteries

11. Blood Supply to the Brain • The vertebral arteries join to form the basilar artery before branching into the arterial circle (circle of Willis) that forms a loop around the pituitary gland. • Joins with the internal carotid arteries anteriorly

12. Brain Regions • Forebrain • Cerebrum • Diencephalon • Midbrain • Corpora Quadrigemina • Hindbrain • Pons • Medulla oblongata • cerebellum

13. Cerebrum • Frontal lobe (many higher functions) • Intellect, abstract reasoning, creativity, social awareness and language • Precentral gyrus = primary motor cortex • Broca’s area is the motor speech area • Parietal lobe • Sensation (except smell), language • Postcentral gyrus=primary somatic sensory cortex • Wernicke's area involved in the formation of language

14. Cerebrum • Occipital lobe • Primary vision cortex • Shape, color and distance of an object are perceived here • Temporal lobe • Primary auditory cortex, interprets impulses sent from the inner ear • Translates words into thought

16. Precentral Gyrus: (frontal lobe) contains the primary motor area Central Sulcus Postcentral Gyrus: (parietal lobe) contains the primary somatosensory area.

17. Cerebral Hemispheres • Left hemisphere involved with language and reasoning (Broca area usually on left) • Right hemisphere involved in space and pattern perceptions, artistic awareness, imagination

18. Sulci & Gyri Sulci • Sulci: Shallow depressions of the cerebral cortex • Central sulcus is between the frontal and parietal lobes • Lateral sulcus is between the parietal lobes and temporal lobes. • Fissures: Deep grooves • Longitudinal: separates cerebral hemispheres • Transverse: separates cerebrum form the cerebellum • Gyri: The elevated ridges of the cerebral cortex • Serve to increase the surface area

19. Longitudinal Fissure Transverse fissure TransverseFissure

20. Central Sulcus Lateral Sulcus

21. Diencephalon Structures • Thalamus • Hypothalamus • Epithalamus

22. Diencephalon: Hypothalamus • Pituitary gland: Attaches to the hypothalamus via the infundibulum • Mamillary bodies: Process olfactory sensations. (smell to memory) Mamillary body Pituitary gland (not in this picture) would be hanging here

23. Diencephalon: Hypothalamus • Major Functions: • Controls somatic motor activities at the subconscious level • Controls autonomic function • Coordinates activities of the nervous and endocrine systems • Secretes hormones • Produces emotions and behavioral drives • Coordinates voluntary and autonomic functions • Regulates body temperature • Coordinates circadian cycles of activity

24. Diencephalon: Thalamus • Relay station for sensory input

25. Diencephalon: Epithalamus • Superior to the third ventricle, contains the pineal gland Pineal gland

26. Brainstem 3 Structures: • Midbrain (mesencephalon) • Pons • Medulla oblongata Corpora quadrigemina

27. Midbrain Pons Corpora quadrigemina Medulla

30. Midbrain • Functions: • Connects pons to cerebellum • Superior colliculi: visual reflex centers • Inferior colliculi: auditory reflex centers

31. Brainstem: Pons • Functions: • Sensory and motor nuclei of Cranial nerves V, VI, VII, and VIII • Respiratory control: • Apneustic center and pneumotaxic center to modify the activity of the respiratory rhythmicity center in the medulla • Nuclei and tracts that process and relay information to and from the cerebellum

32. Medulla Oblongata • Functions: • Center for the coordination of complex autonomic reflexes (heart rate, respiratory rhythm, blood pressure) • Control of visceral functions (vomiting, swallowing) • Decussation of pyramids: a crossover point for the major motor tracts

33. Cerebellum • Functions: • Coordination of movements • Adjustment of postural muscles Vermis Arbor Vita (white matter that looks like a leaf)

34. Cerebral Cortex • The superficial layer/rim of gray matter in the cerebral hemispheres • Gray matter consists of cell bodies, dendrites, and unmyelinated axons.

35. White Matter & Basal Nuclei • White matter consists primarily of myelinated axons • Is beneath the gray matter cortex • Notice how it is the opposite arrangement from the spinal cord (Spinal cord: white matter is on the outside and gray matter is on the inside.) • Corpus callosum: Connects the right and left hemispheres • Basal nuclei: Islands of gray matter within the white matter. • Function: Involved in the subconscious control of skeletal muscle tone and the coordination of learned movement patterns

36. White Matter White Matter & Basal Nuclei Basal Nuclei Corpus Callosum

37. Sheep Brain Dissection • Follow instructions in book for the sheep brain dissection. • When finished discard brain in the container provided. Wash utensils and put back so other classes can use the materials. • ID structures on the brain models for next week’s quiz.

38. Cranial Nerves • Nerves that originate from the brain rather than the spinal cord • Part of the peripheral nervous system (not the central nervous system) • CNs (except for XII) are in sequence from anterior to posterior • May contain one or more of the following: • Sensory: receives neural input • Somatic Motor: predominantly innervates muscles • Mixed: have significant sensory and motor functions

39. CN I: Olfactory Nerve • Function: • Sensory for smell • Exiting foramen=cribriform plate • Origin forebrain • Test: Have patient identify aromatic substances like vanilla or coffee • Symptoms of nerve damage: Anosmia: diminished or absent sense of smell

40. CN II: Optic Nerve • Function: • Sensory for vision • Exiting foramen= optic canal • Origin=forebrain • Tests: • Eye chart • Check peripheral vision • Funduscopic exam

41. CN II: Optic Nerve • Optic chiasm: Fibers from the nasal half of each retina cross over to the opposite side of the brain. • Symptoms of nerve damage: • Loss of vision (peripheral or central) • Abnormal funduscopic appearance

42. CN II: Optic Nerve Pathology Papilledema. Note swelling of the disc, hemorrhages, and exudates, with preservation of the physiologic cup. Proliferative Diabetic Retinopathy. Note the multiple hemorrhages throughout the retina.

43. Cranial Nerves III, IV & VI(Control Eye Movements)

44. CN III: Oculomotor nerve • Function: • Somatic Motor to extraocular muscles (voluntarily move the eye) • Parasympathetic (motor) to iris and lens (pupillary constriction) • Exiting Foramen= superior orbital fissure • Origin= midbrain • Tests: • Check pupils for size, shape and equality • Shine light in each eye and check for pupil constriction • Have patient follow an object in all directions to check for symmetric eye movements

45. CN III: Oculomotor Nerve Injury • Symptoms of nerve damage: • Double vision (diplopia): The affected eye turns outward when the unaffected eye looks straight ahead • The affected eye can move only to the middle when looking inward and cannot look upward and downward. • Ptosis: eyelid droop • Pupil may be dilated and sometimes fixed

46. Oculomotor Nerve Injury Right Eye Injured side Normal side

47. Pupillary Reflex Efferent Afferent Consensual reflex: Both pupils should constrict at the same time

48. Originates in the midbrain CN IV: Trochlear Nerve • Function: • Somatic motor to superior oblique muscle of the eye. • Exiting foramen= superior orbital fissure • Origin= midbrain • Test: Check eye movements • Symptoms of nerve damage: • Outward rotation of the affected eye • Vertical diplopia Normal side Injured side

49. Originates in the pons CN VI: Abducens Nerve • Function: • Somatic Motor to lateral rectus muscle of the eye. Exiting foramen=superior orbital fissure Origin= pons • Test: Check eye movements • Symptoms of nerve damage: • The affected eye will tend to be deviated inward because of the unopposed action of the medial rectus muscle. • Cannot move eyeball laterallybeyond the midpoint Normal side Injured side

50. CN V: Trigeminal Nerve 3 Branches • Ophthalmic • Maxillary • Mandibular