Memmler’s The Human Body in Health and Disease 11 th edition

1. Memmler’sThe Human Body in Health and Disease11th edition Chapter 10 The Nervous System: The Brain and Cranial Nerves

2. I. The Brain: Main parts • Cerebrum • Cerebral hemispheres • Longitudinal fissure • Lobes • Diencephalon • Thalamus • Hypothalamus • Brain stem • Midbrain • Pons • Medulla oblongata • Cerebellum

3. Brain, sagittal section. Main divisions are shown.

4. External surface of the brain, superior view. The division into two hemispheres and into lobes is visible.

5. II. Protective Structures of theBrain and Spinal Cord • Meninges • Dura mater • Arachnoid • Pia mater

6. Dura mater • - Is the thickest and toughest • - Is in two layers, and the outer layer is fused to the cranial bones. In certain places, these two layers separate to provide venous channels, called dural sinuses, for the drainage of blood coming from the brain tissue • Arachnoid • - loosely attached to the pia mater by weblikefibers, allowing a space for the movement of cerebrospinal fluid (CSF) between the two membranes. • Pia mater • is attached to the nervous tissue of the brain and spinal cord • is made of a delicate connective tissue • holds blood vessels that supply nutrients and oxygen to the brain and spinal cord.

7. Frontal (coronal) section of the top of the head. The meninges and related parts are shown. ZOOMING IN • What is located in the spaces where the dura mater divides into two layers?

9. Cerebrospinal Fluid • CSF • is a clear liquid that circulates freely in and around the brain and spinal cord and finally flows out into the subarachnoid space of the meninges, then returns to the blood through projections called arachnoidvilli in the dural sinuses • Function: • Supports nervous tissue • cushions from shock • Carries nutrients to cells • Transports waste products from cells • Produced in ventricles (4 of them: lateral, third and fourth) • Choroid plexus (found in all 4 ventricles) • forms CSF by filtration of the blood and by cellular secretion. • Lateral ventricles (paired) • communicate with a midline space, the third ventricle, by means of openings called interventricular foramina • Cerebral aqueduct • extends through the midbrain into the fourth ventricle, which is located between the brain stem and the cerebellum

10. Flow of cerebrospinal fluid (CSF). Black arrows show the flow of CSF from the choroid plexuses and back to the blood in dural sinuses; white arrows show the flow of blood. (The actual passageways through which the CSF flows are narrower than those shown here, which have been enlarged for visibility.) ZOOMING IN • Which ventricle is continuous with the central canal of the spinal cord?

11. Lateral: - in the two cerebral hemispheres • Third - surrounded by the diencephalon • Fourth -located between the brain stem and the cerebellum

12. III. The Cerebral Hemispheres: Structure • Lobes • Frontal • Parietal • Temporal • Occipital • Insula • Gray matter (Cerebral cortex) • Gyri • Sulci • Central sulcus • Lateral sulcus • White matter • Basal nuclei (basal ganglia) • Corpus callosum • Internal capsule

13. External surface of the brain, lateral view. The lobes and surface features of the cerebrum are visible. ZOOMING IN • What structure separates the frontal from the parietal lobe?

14. Outer part of cerebral hemispher • The outer nervous tissue of the cerebral hemispheres (makes up the gray matter) • responsible for conscious thought, reasoning, and abstract mental functions • arranged in folds forming elevated portions known as gyri that are separated by shallow grooves called sulci • The central sulcus, which lies between the frontal and parietal lobes • The lateral sulcus, which curves along the side of each hemisphere and separates the temporal lobe from the frontal and parietal lobes

15. Inner part of the cerebral hemisphere • Internally, the cerebral hemispheres are made largely of white matter and a few islands of gray matter • Basal nuclei (aka basal ganglia) • Island of gray matter located deep within each cerebral hemisphere. • work with the cerebral cortex to regulate body movement and the muscles of facial expression. • secrete the neurotransmitter dopamine • Corpus callosum • is an important band of white matter located at the bottom of the longitudinal fissure and bridges the left & right hemisphere • Internal capsule • carries impulses between the cerebral hemispheres and the brain stem.

16. Basal Ganglia & Corpus Callosum

17. Functions of the Cerebral Cortex • Frontal lobe • Motor area • provides conscious control of skeletal muscles • Speech centers • Parietal lobe • Sensory area • Interpretesimpulses from the skin, such as touch, pain, and temperature • Estimation of distances, sizes, shapes • Temporal lobe • Auditory area • for receiving and interpreting impulses from the ear • Olfactory area • Interprets impulses arising from receptors in the nose • Occipital lobe • Visual receiving and Visual association area • Interprets impulses arising from the retina of the eye.

19. Functional areas of the cerebral cortex. ZOOMING IN • What cortical area is posterior to the central sulcus? What area is anterior to the central sulcus?

20. Communication Areas • Communication is a good example that shows how areas of the cerebral cortex functionally are interrelated • Auditory areas : lies in the temporal lobe • Auditory receiving : detects sound impulses transmitted from the environment, • Auditory association: interprets the sounds • Speech comprehension (Wernicke area): functions in speech recognition and the meaning of words • Babies often appear to understand what is being said long before they do any talking themselves. • Motor areas • Motor areas for spoken and written communication lie anterior to the most inferior part of the frontal lobe's motor cortex • Motor speech (Broca area): controls speech muscles in the tongue, the soft palate, and the larynx . damage to this area may result in difficulty in producing speech (motor aphasia). • Written speech center: lies anterior to the cortical area that controls the arm and hand muscles. • Visual areas • visual images of language are received. The visual area that lies anterior to the receiving cortex then interprets these visual impulses as words. The ability to read with understanding also develops in this area. Reading Japanese involves only the receiving area

21. Memory and the Learning Process • Short-term memory • Information lost unless reinforced • Long-term memory • Rehearsal (repetition) • Alertness

22. IV. The Diencephalon • Thalamus • Nearly all sensory impulses travel through it • sort out the sensory impulses • direct them to particular areas of the cerebral cortex. • Hypothalamus • Maintain homeostasis by controlling body temperature, water balance, sleep, appetite, and some emotions, such as fear and pleasure • Controls sympathetic and parasympathetic divisions of autonomic nervous system • Influences heartbeat, blood flow, hormone secretion • Controls the pituitary gland

23. Regions of the diencephalon. The figure shows the relationship among the thalamus, hypothalamus, and pituitary gland (hypophysis). ZOOMING IN • To what part of the brain is the pituitary gland attached?

24. The Limbic System • Between cerebrum and diencephalon • Involved in emotional states, behavior • It includes the hippocampus which functions in learning and the formation of long-term memory • Stimulates the reticular formation: a network that extends along the brain stem and governs wakefulness and sleep. • links the conscious functions of the cerebral cortex and the automatic functions of the brain stem.

26. V. The Brain Stem • Composed of: • midbrain, • pons, and • medulla oblongata • Connects cerebrum and diencephalon with the spinal cord

27. The Midbrain • Superior part of brain stem • Four masses form superior part of midbrain • Center for reflexes involving eyes and ears, for example, moving the eyes in order to track an image or to read. • Conducts impulses between higher centers of cerebrum and lower centers of pons, medulla, cerebellum, spinal cord • Cranial nerves III and IV originate from the midbrain

28. The Pons • Connecting link between cerebellum and rest of nervous system • contains nerve fibers that carry impulses to and from the centers located above and below it • Certain reflex (involuntary) actions, such as some of those regulating respiration, are integrated in the pons. • Cranial nerves V through VIII originate from the pons.

29. The Medulla Oblongata • Externally myelinated, internally contains collections of cell bodies (gray matter) called nuclei, or centers: • The respiratory center controls the muscles of respiration in response to chemical and other stimuli. • The cardiaccenter helps regulate the rate and force of the heartbeat. • The vasomotorcenter regulates the contraction of smooth muscle in the blood vessel walls and thus controls blood flow and blood pressure. • The crossing of motor fibers in the medulla results in contralateral (opposite side) control • The last four pairs of cranial nerves (IX through XII) are connected with the medulla

30. VI. The Cerebellum • Three parts • Vermis (middle portion) • Left hemisphere (lateral) • Right hemisphere (lateral) • Functions • Coordinate voluntary Muscles to ensure smooth, orderly function • Maintain balance during walking, standing etc • Maintain muscle tone so that all muscle fibers are slightly tensed and ready to produce changes in position as quickly as necessary

31. The cerebellum. (A) Posterior view showing the two hemispheres. (B) Midsagittal section showing the distribution of gray and white matter. The three parts of the brain stem (midbrain, pons, and medulla oblongata) are also labeled.

32. VII. Brain Studies Imaging techniques to study the brain without surgery • Computed tomography (CT) scan • provides photographs of the bone, soft tissue, and cavities of the brain • Magnetic resonance imaging (MRI) • gives more views of the brain than • Positron emission tomography (PET) • visualizes the brain in action

33. 12 Imaging the brain. (A) CT scan of a normal adult brain at the level of the fourth ventricle. (B) MRI of the brain showing a point of injury (arrows). (C) PET scan.

34. Electroencephalograph • Record electric currents given off by brain nerve cells • Study sleep patterns • Diagnose disease • Locate tumors • Study drug effects • Determine brain death

35. Figure 10-13 Electroencephalography. (A) Normal brain waves. (B) Abnormal brain waves.

36. VIII. Disorders of the Brain andAssociated Structures • Meningitis • Inflammation of brain and spinal cord coverings Cause: • Bacterial causes • the meningococcus, Haemophilusinfluenzae , Streptococcus pneumoniae • Viral causes • mumps virus Effect/symptom: • Headache, stiff neck, nausea, and vomiting Diagnosis by lumbar puncture and examination of the CSF for pathogens and white blood cells (pus). • Encephalitis • Inflammation of the brain • Viral causes • Toxic substances causes • Viral vaccine causes

37. Hydrocephalus • Abnormal CSF accumulation within brain • Causes • Either from overproduction or impaired drainage of the fluid • Congenital malformation • Tumor • Inflammation • Hemorrhage • Treatment • Treatment of hydrocephalus involves the creation of a shunt (bypass) to drain excess CSF from the brain.

38. Stroke and Other Brain Disorders • Stroke: aka cerebrovascular accident (CVA) • Most common brain disorder • Cause: • blood clot that blocks blood flow to an area of brain tissue • rupture of a blood vessel resulting in cerebralhemorrhage • Smoking and excess alcohol consumption also increase the risk of stroke • Effect • aphasia (ah-FA-ze-ah), a loss or defect in language communication.

39. Cerebral palsy • cause • brain damage occurring before or during the birth process • Effect • diverse muscular disorders that vary in degree from only slight weakness of the lower extremity muscles to paralysis of all four extremities as well as the speech muscles • Treatment • muscle and speech training and other therapeutic approaches

40. Epilepsy • a chronic disorder involving an abnormality of the brain's electrical activity with or without apparent changes in the nervous tissues • Cause • unkown • Effect • seisure

41. Brain tumor • Most brain tumors originate from the neuroglia (support tissue of the brain) and are called gliomas • Tend not to metastasize, but they can compress brain tissue. • Symptom/effect • depend on the type of tumor, its location, and its degree of destructiveness. • Treatment • implanting timed-release drugs into a tumor site at the time of surgery

42. Injury Head trauma can lead to injury within skull • Epidural hematoma • Cause: • Damage to an artery from a skull fracture • Effect: • bleeding between the dura mater and the skull • pressure on blood vessels and interrupts blood flow to the brain. • Symptoms include headache, partial paralysis, dilated pupils, and coma

43. Subdural hematoma • Cause • A tear in the wall of a dural sinus results from a blow to the front or back of the head that separates the dura from the arachnoid, • Intracerebral hematoma • Bleeding into the brain tissue • Cerebral concussion • Cause: • a blow to the head or from sudden movement of the brain against the skull, as in violent shaking. • Effect • loss of consciousness, headache, dizziness, vomiting, and even paralysis and impaired brain function

44. Multi-infarct dementia • Cause • brain damage resulting from chronic ischemia (lack of blood supply) that for example would be caused by a series of small strokes • Effect • progressive loss of memory, judgment, and cognitive function.

45. Parkinson disease • a progressive neurologic condition characterized by tremors, rigidity of limbs and joints, slow movement, and impaired balance • Cause • cell death in a part of the brain, the substantianigra, that produces the neurotransmitter dopamine. • encephalitis or other brain diseases, exposure to certain toxins, or repeated head injury, as may occur in boxing. • Treatment • administration of L-dopa, a substance that is capable of entering the brain and converting to dopamine • Drug that mimic the effects of dopamine, prevent its breakdown, or increase the effectiveness of L-dopa. • Implanting cells and electrical stimulation devices

46. Alzheimer disease • Cause • unexplained degeneration of the cerebral cortex and hippocampus • Effect • intellectual impairment with mood changes and confusion. Memory loss, especially for recent events, is a common early symptom. • development of amyloid, an abnormal protein, and a tangling of neuron fibers that prevents communication between cells • Treatment • No cure, but several drugs, herbal extracts, estrogen hormones and vitamines E can delay the progression of early disease.

47. IX. Cranial Nerves • 12 pairs • Four categories • Special sensory impulses • such as those for smell, taste, vision, and hearing, located in special sense organs in the head. • General sensory impulses • such as those for pain, touch, temperature, deep muscle sense, pressure, and vibrations. • Somatic motor impulses • resulting in voluntary control of skeletal muscles • Visceral motor impulses • producing involuntary control of glands and involuntary muscles

48. Cranial nerves. The 12 pairs of cranial nerves are seen from the base of the brain.

49. Names and Functions of the Cranial Nerves • I Olfactory: carries smell impulses from receptors in the nasal mucosa to the brain • II Optic: carries visual impulses from the eye to the brain • III Oculomotor: concerned with the contraction of most of the eye muscles • IV Trochlear: supplies one eyeball muscle • V Trigeminal: It has three branches that transport general sense impulses (e.g., pain, touch, temperature) from the eye, the upper jaw, and the lower jaw. • VI Abducens: controlling impulses to an eyeball muscle. • VII Facial: Controls muscles of facial expression; carries sensation of taste; stimulates small salivary glands and lacrimal (tear) gland • VIII Vestibulocochlear: carries sensory impulses for hearing and equilibrium from the inner ear. • IX Glossopharyngeal: contains general sensory fibers from the posterior tongue and the pharynx (throat) • X Vagus: largest. supplies most of the organs in the thoracic and abdominal cavities. • XI Accessory: motor nerve with two branches. One branch controls two muscles of the neck, the trapezius and sternocleidomastoid; the other supplies muscles of the larynx. • XII Hypoglossal: carries impulses controlling the tongue muscles. Oh Once One Takes The Anatomy Final AGood Vacation Seems Heavenly Except for the first two pairs, all the cranial nerves arise from the brain stem. The first 9 pairs and the 12th pair supply structures in the head.

50. Disorders Involving the Cranial Nerves • Destruction of optic fibers • Damage to hearing nerves • Paralysis of muscles • Bell palsy • Neuralgia