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Chapter 14

Chapter 14. The Brain and Cranial Nerves Lecture Outline. INTRODUCTION. The brain receives sensory input, integrates it, makes decisions, and regulates movement. It is also the center for intellect, emotions, behavior, and memory. Chapter 14 The Brain and Cranial Nerves.

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Chapter 14

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  1. Chapter 14 The Brain and Cranial Nerves Lecture Outline

  2. INTRODUCTION • The brain receives sensory input, integrates it, makes decisions, and regulates movement. • It is also the center for intellect, emotions, behavior, and memory. Principles of Human Anatomy and Physiology, 11e

  3. Chapter 14The Brain and Cranial Nerves • Largest organ in the body at almost 3 lb. • Brain functions in sensations, memory, emotions, decision making, behavior Principles of Human Anatomy and Physiology, 11e

  4. Blood Flow and the Blood-Brain Barrier • An interruption of blood flow for 1 or 2 minutes impairs neuronal function. • A total deprivation of oxygen for 4 minutes causes permanent injury. • Because carbohydrate storage in the brain is limited, the supply of glucose to the brain must be continuous. • Glucose deficiency may produce mental confusion, dizziness, convulsions, and unconsciousness. Principles of Human Anatomy and Physiology, 11e

  5. BBB • A blood-brain barrier (BBB) protects brain cells from harmful substances and pathogens by serving as a selective barrier to prevent passage of many substances from the blood to the brain. • An injury to the brain due to trauma, inflammation, or toxins causes a breakdown of the BBB, permitting the passage of normally restricted substances into brain tissue. • The BBB may also prevent entry of drugs that could be used as therapy for brain cancer or other CNS disorders, so research is exploring ways to transport drugs past the BBB. Principles of Human Anatomy and Physiology, 11e

  6. Protective Covering of the Brain • The brain is protected by the cranial bones (Figure 7.4) and the cranial meninges (Figure 14.2). Principles of Human Anatomy and Physiology, 11e

  7. CEREBROSPINAL FLUID • Cerebrospinal fluid (CSF) is a clear, colorless liquid that protects the brain and spinal cord against chemical and physical injuries. Principles of Human Anatomy and Physiology, 11e

  8. Cerebrospinal Fluid (CSF) • 80-150 ml (3-5oz) • Clear liquid containing glucose, proteins, & ions • Functions • mechanical protection • floats brain & softens impact with bony walls • chemical protection • optimal ionic concentrations for action potentials • circulation • nutrients and waste products to and from bloodstream Principles of Human Anatomy and Physiology, 11e

  9. Teaching Project • Each group will be assigned a section of the brain. • You must create a power point presentation of 10 slides or less. • These must be “note-taking friendly” and follow the guidelines on instruction sheet you will receive today. • We will begin presentations first thing this THURSDAY and probably continue until Friday. • Test is next Thursday! Principles of Human Anatomy and Physiology, 11e

  10. Origin of CSF • Choroid plexus = capillaries covered by ependymal cells • 2 lateral ventricles, one within each cerebral hemisphere • roof of 3rd ventricle • fourth ventricle Principles of Human Anatomy and Physiology, 11e

  11. Hydrocephalus • Blockage of drainage of CSF (tumor, inflammation, developmental malformation, meningitis, hemorrhage or injury) • Continued production cause an increase in pressure --- hydrocephalus • In newborn or fetus, the fontanels allow this internal pressure to cause expansion of the skull and damage to the brain tissue • Neurosurgeon implants a drain shunting the CSF to the veins of the neck or the abdomen Principles of Human Anatomy and Physiology, 11e

  12. THE BRAIN STEM Principles of Human Anatomy and Physiology, 11e

  13. Medulla Oblongata • Continuation of spinal cord • Ascending sensory tracts • Descending motor tracts • Nuclei of 5 cranial nerves • Cardiovascular center • force & rate of heart beat • diameter of blood vessels • Respiratory center • medullary rhythmicity area sets basic rhythm of breathing • Information in & out of cerebellum • Reflex centers for coughing, sneezing, swallowing etc. Principles of Human Anatomy and Physiology, 11e

  14. Ventral Surface of Medulla Oblongata • Ventral surface bulge • pyramids • large motor tract • decussation of most fibers • left cortex controls right muscles • Olive = olivary nucleus • neurons send input to cerebellum • proprioceptive signals • gives precision to movements Principles of Human Anatomy and Physiology, 11e

  15. Dorsal Surface of Medulla Oblongata • Nucleus gracilis & nucleus cuneatus = sensory neurons • relay information to thalamus on opposite side of brain • 5 cranial nerves arise from medulla -- 8 thru 12 Principles of Human Anatomy and Physiology, 11e

  16. XII = Hypoglossal Nerve • Controls muscles of tongue during speech and swallowing • Injury deviates tongue to injured side when protruded • Mixed, primarily motor Principles of Human Anatomy and Physiology, 11e

  17. XI = Spinal Accessory Nerve • Cranial portion • arises medulla • skeletal mm of throat & soft palate • Spinal portion • arises cervical spinal cord • sternocleidomastoid and trapezius mm. Principles of Human Anatomy and Physiology, 11e

  18. X = Vagus Nerve • Receives sensations from viscera • Controls cardiac muscle and smooth muscle of the viscera • Controls secretion of digestive fluids Principles of Human Anatomy and Physiology, 11e

  19. IX = Glossopharyngeal Nerve • Stylopharyngeus m. (lifts throat during swallowing) • Secretions of parotid gland • Somatic sensations & taste on posterior 1/3 of tongue Principles of Human Anatomy and Physiology, 11e

  20. VIII = Vestibulocochlear Nerve • Cochlear branch begins in medulla • receptors in cochlea • hearing • if damaged deafness or tinnitus (ringing) is produced • Vestibular branch begins in pons • receptors in vestibular apparatus • sense of balance • vertigo (feeling of rotation) • ataxia (lack of coordination) Principles of Human Anatomy and Physiology, 11e

  21. Injury to the Medulla • Hard blow to the back of the head may be fatal • Cranial nerve malfunctions on same side as injury;loss of sensation or paralysis of throat or tongue; irregularities in breathing and heart rhythm Principles of Human Anatomy and Physiology, 11e

  22. Pons • The pons is located superior to the medulla. It connects the spinal cord with the brain and links parts of the brain with one another by way of tracts (Figures 14.1, 14.5). • relays nerve impulses related to voluntary skeletal movements from the cerebral cortex to the cerebellum. • contains the pneumotaxic and apneustic areas, which help control respiration along with the respiratory center in the medulla (Figure 23.24). • contains nuclei for cranial nerves V trigeminal, VI abducens, VII facial, and VIII vestibulocochlear (vestibular branch only).(Figure 14.5). Principles of Human Anatomy and Physiology, 11e

  23. Pons • One inch long • White fiber tracts ascend and descend • Pneumotaxic & apneustic areas help control breathing • Middle cerebellar peduncles carry sensory info to the cerebellum • Cranial nerves 5 through 7 Principles of Human Anatomy and Physiology, 11e

  24. VII = Facial Nerve • Motor portion • facial muscles • salivary & nasal and oral mucous glands & tears • Sensory portion • taste buds on anterior 2/3’s of tongue Principles of Human Anatomy and Physiology, 11e

  25. VI = Abducens Nerve • Lateral rectus eye muscle Principles of Human Anatomy and Physiology, 11e

  26. V = Trigeminal Nerve • Motor portion • muscles of mastication • Sensory portion • touch, pain, & temperature receptors of the face • ophthalmic branch • maxillary branch • mandibular branch Principles of Human Anatomy and Physiology, 11e

  27. Midbrain • One inch in length • Extends from pons to diencephalon • Cerebral aqueduct connects 3rd ventricle above to 4th ventricle below Principles of Human Anatomy and Physiology, 11e

  28. Midbrain in Section • Cerebral peduncles---clusters of motor & sensory fibers • Substantia nigra---helps controls subconscious muscle activity • Red nucleus-- rich blood supply & iron-containing pigment • cortex & cerebellum coordinate muscular movements by sending information here from the cortex and cerebellum Principles of Human Anatomy and Physiology, 11e

  29. Dorsal Surface of Midbrain • Corpora quadrigemina = superior & inferior colliculi • coordinate eye movements with visual stimuli • coordinate head movements with auditory stimuli Principles of Human Anatomy and Physiology, 11e

  30. IV = Trochlear Nerve • Superior oblique eye muscle Principles of Human Anatomy and Physiology, 11e

  31. III = Oculomotor Nerve • Levator palpebrae raises eyelid (ptosis) • 4 extrinsic eye muscles • 2 intrinsic eye muscles • accomodation for near vision (changing shape of lens during reading) • constriction of pupil Principles of Human Anatomy and Physiology, 11e

  32. Reticular Formation • Scattered nuclei in medulla, pons & midbrain • Reticular activating system • alerts cerebral cortex to sensory signals (sound of alarm, flash light, smoke or intruder) to awaken from sleep • maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles • Motor function is involvement with maintaining muscle tone Principles of Human Anatomy and Physiology, 11e

  33. Cerebellum • 2 hemispheres • Function • correct voluntary muscle contraction and posture based on sensory data from body about actual movements • sense of equilibrium and balance Principles of Human Anatomy and Physiology, 11e

  34. Cerebellum Structure • There is a transverse fissure between cerebellum & cerebrum • Cerebellar cortex (outside) & central nuclei are grey matter • Arbor vitae = tree of life = white matter (inside) Principles of Human Anatomy and Physiology, 11e

  35. Cerebellar Peduncles • Superior, middle & inferior peduncles attach to brainstem • inferior carries sensory information from spinal cord • middle carries sensory fibers from cerebral cortex & basal ganglia • superior carries motor fibers that extend to motor control areas Principles of Human Anatomy and Physiology, 11e

  36. THE DIENCEPHALON Principles of Human Anatomy and Physiology, 11e

  37. Diencephalon Surrounds 3rd Ventricle • Surrounds 3rd ventricle • Superior part of walls is thalamus • Inferior part of walls & floor is hypothalamus Principles of Human Anatomy and Physiology, 11e

  38. Thalamus • The thalamus is located superior to the midbrain and contains nuclei that serve as relay stations for all sensory impulses, except smell, to the cerebral cortex (Figure 14.9). • seven major groups of thalamic nuclei on each side (Figure 14.9 c and d). • They are the Anterior nucleus, medial nuclei, lateral group, ventral group, intralaminar nuclei, midline nucleus, and the reticular nucleus. • It also registers conscious recognition of pain and temperature and some awareness of light touch and pressure. • It plays an essential role in awareness and the acquisition of knowledge (cognition.) Principles of Human Anatomy and Physiology, 11e

  39. Thalamus • 1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate mass) • Relay station for sensory information on way to cortex • Crude perception of some sensations Principles of Human Anatomy and Physiology, 11e

  40. Thalamic Nuclei • Nuclei have different roles • relays auditory and visual impulses, taste and somatic sensations • receives impulses from cerebellum or basal ganglia • anterior nucleus concerned with emotions, memory and acquisition of knowledge (cognition) Principles of Human Anatomy and Physiology, 11e

  41. Hypothalamus • The hypothalamus • inferior to the thalamus, has four major regions (mammillary, tuberal, supraoptic, and preoptic) • controls many body activities, and is one of the major regulators of homeostasis (Figure 14.10). • The hypothalamus has a great number of functions. • It controls the ANS. • It produces hormones. • It functions in regulation of emotional and behavioral patterns. • It regulates eating and drinking through the feeding center, satiety center, and thirst center. • It aids in controlling body temperature. • It regulates circadian rhythms and states of consciousness. Principles of Human Anatomy and Physiology, 11e

  42. Hypothalamus • Dozen or so nuclei in 4 major regions • mammillary bodies are relay station for olfactory reflexes;infundibulum suspends the pituitary gland • Major regulator of homeostasis • receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood Principles of Human Anatomy and Physiology, 11e

  43. Epithalamus • The epithalamus lies superior and posterior to the thalamus and contains the pineal gland and the habenular nuclei (Figure 14.7). • The pineal gland secretes melatonin to influence diurnal cycles in conjunction with the hypothalamus. • The habenular nuclei (Figure 14.7a) are involved in olfaction, especially emotional responses to odors. Principles of Human Anatomy and Physiology, 11e

  44. Epithalamus • Pineal gland • endocrine gland the size of small pea • secretes melatonin during darkness • promotes sleepiness & sets biological clock • Habenular nuclei • emotional responses to odors Principles of Human Anatomy and Physiology, 11e

  45. Subthalamus • The subthalamus lies immediately inferior to the thalamus and includes tracts and the paired subthalamic nuclei, which connect to motor areas of the cerebrum. • The subthalamic nuclei and red nucleus and substantia nigra of the midbrain work together with the basal ganglia, cerebellum, and cerebrum in control of body movements. • Table 14.2 summarizes the functions of the parts of the diencephalon. Principles of Human Anatomy and Physiology, 11e

  46. Circumventricular Organs • Parts of the diencephalon, called circumventricular organs (CVOs), can monitor chemical changes in the blood because they lack a blood-brain barrier. • CVOs include • part of the hypothalamus, • the pineal gland, • the pituitary gland, and a few other nearby structures. • They function to coordinate homeostatic activities of the endocrine and nervous systems. • They are also thought to be the site of entry into the brain of HIV. Principles of Human Anatomy and Physiology, 11e

  47. THE CEREBRUM • The cerebrum is the largest part of the brain . • The surface layer, the cerebral cortex, is 2-4 mm thick and is composed of gray matter. The cortex contains billions of neurons. • The cortex contains gyri (convolutions), deep grooves called fissures, and shallower sulci. (Figure 14.11a) • Beneath the cortex lies the cerebral white matter, tracts that connect parts of the brain with itself and other parts of the nervous system. • The cerebrum is nearly separated into right and left halves, called hemispheres, by the longitudinal fissure. • Internally it remains connected by the corpuscallosum, a bundle of transverse white fibers. Figure 14.12) Principles of Human Anatomy and Physiology, 11e

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