Chapter 38

1. Chapter 38 Nervous System

2. Learning Objectives • Describe the evolution of nervous system • List the functions and location of the cerebrum, thalamus, hypothalamus, midbrain, cerebellum, pons, medulla oblongata, basal nucleii, amygdala and hippocampus of the limbic system • Differentiate the somatic and autonomic systems • Diagram the spinal reflex circuit • Differentiate functions of the left and right hemisphere

3. Learning Objectives • Diagram the lobes of the cerebrum according to function and anatomy • Discuss the process of memory • Debate the existence of consciousness • Explain the various types of neurological disorder incidence and symptoms

4. Invertebrate Nervous Systems (1) • Simplest nervous systems: The nerve nets of cnidarians • Echinoderms have modified nerve nets, with some neurons grouped into nerves

5. Invertebrate Nervous Systems (2) • Flatworms, arthropods, and mollusks have a simple central nervous system (CNS) • Ganglia in the head region (brain) • Peripheral nervous system (PNS) • Nerve cords from central ganglia to rest of body

6. c. Planarian (flatworm) Eyespot Ganglia Longitudinal nerve cords Fig. 38.1c, p. 869

7. d. Arthropod (grasshopper) Dorsal ganglia Ventral ganglion Ganglia of ventral nerve cord Fig. 38.1d, p. 869

8. e. Mollusk (octopus) Ganglia associated with internal organs Optic lobe Frontal lobes Lobed brain Eye Fig. 38.1e, p. 869

9. Chordate Nervous Systems • CNS • Large brain located in the head • Hollow spinal cord • PNS • All the nerves and ganglia connecting CNS to the rest of the body

10. Development in Vertebrates • Vertebrate embryo • Anterior end of neural tube develops into brain • Rest develops into spinal cord • Embryonic brain enlarges into forebrain, midbrain, and hindbrain • Develop into adult structures

11. Regions in 4-week embryo Regions in adult Regions in 5-week embryo Functions in adult Neural tube Higher functions, such as thought, action, and communication Telencephalon (cerebrum) Telencephalon Coordinates sensory input and relays it to cerebellum Forebrain Thalamus Diencephalon Center for homeostatic control of internal environment Hypothalamus Coordinates involuntary reactions and relays signals to telencephalon Mesencephalon Midbrain Midbrain Integrates signals for muscle movement Cerebellum Metencephalon Hindbrain Pons Center for information flow between cerebellum and telencephalon Medulla oblongata Controls many involuntary tasks Myelencephalon Fig. 38.2a, p. 870

12. Hypothalamus Hemisphere of cerebrum Thalamus Brain stem: Midbrain Pons Cerebellum Medulla oblongata Spinal cord Central canal Adult brain regions Fig. 38.2e, p. 870

13. The Peripheral Nervous System • Somatic system controls skeletal muscles • Voluntary body movements • Involuntary muscle contractions that maintain balance, posture, muscle tone • Autonomic system controls involuntary functions • Sympathetic system • Parasympathetic system

14. Parasympathetic Division Sympathetic Division Constricts pupil; adjusts eye for near vision Dilates pupil; adjusts eye for far vision Optic nerve Eyes Eyes Cranial nerves Salivary glands Stimulates secretion Salivary glands Inhibits secretion Vagus nerve Decreases heart rate Increases heart rate Heart Heart Constricts bronchioles (airways) Lungs Dilates bronchioles Lungs Stimulates stomach activity Stomach Inhibits stomach activity Stomach Inhibits glucose release Liver Stimulates glucose release Liver Stimulates activity Intestines Intestines Inhibits activity Stimulates contraction (emptying) Relaxes bladder muscles Bladder Bladder Inhibits penile or clitoral arousal Stimulates penile or clitoral arousal Chain of sympathetic ganglia Genitals Genitals Spinal nerves Fig. 38.4, p. 872

15. The Spinal Cord • Carries signals between the brain and the PNS • Its neuron circuits control reflex muscular movements and some autonomicreflexes

16. 2 The afferent neuron transmits the impulses to the spinal cord. 3 Interneurons integrate the information. 1 A pain receptor in the finger stimulates an afferent neuron. Interneuron connections leading to brain Integrating interneurons in spinal cord Stimulus Ganglion Spinal nerve Central canal Gray matter White matter Biceps muscle (flexor) contracts Response 4 One efferent neuron stimulates the flexor muscle to contract. Hand withdrawn 5 The other efferent neuron sends inhibitory signals that keep the extensor muscle from contracting. Effector Triceps muscle (extensor) relaxes 6 The flexor contracts, withdrawing the hand from the pain. Fig. 38.5, p. 873

17. Major Brain Structures • Cerebrum • Brain stem • Medulla • Pons • Midbrain • Thalamus and hypothalamus

18. Structures of the Cerebrum • Right and left cerebral hemispheres • Connected by corpus callosum • Cerebral cortex • Thin gray matter covering core of white matter • Basal nuclei • Collections of gray matter deep in telencephalon

19. Protecting the CNS • Cerebrospinal fluid provides nutrients and cushions the CNS • A blood-brain barrier allows only selected substances to enter the cerebrospinal fluid

20. Layer of cerebrospinal fluid between meninges Ventricles Central canal of spinal cord Cerebral cortex (gray matter) White matter Corpus callosum Basal nuclei (gray matter) Thalamus Ventricles Right cerebral hemisphere Left cerebral hemisphere Fig. 38.6, p. 874

21. Functions of the Brain Stem • Gray-matter centers in pons and medulla control involuntary functions • Centers in midbrain coordinate responses to visual and auditory sensory inputs • Reticular formation • Receives sensory inputs from the body • Sends outputs to cerebral cortex that help maintain balance, posture, muscle tone • Regulates states of wakefulness and sleep

22. Midbrain Cerebellum Pons Medulla Reticular formation Fig. 38.8, p. 875

23. Front of brain Fig. 38.7, p. 875

24. Functions of the Cerebellum • Integrates sensory inputs to coordinate body movements • Positions of muscles and joints • Visual and auditory information

25. The Telencephalon’s Subcortical Gray-Matter Centers • Thalamus • Receives, filters, and relays sensory and motor information to/from regions of cerebral cortex • Hypothalamus • Regulates basic homeostatic functions of body • Contributes to endocrine control of body functions • Basal nuclei • Affect fine-tuning of body movements

26. The Limbic System • Structures • Parts of thalamus, hypothalamus, basal nuclei • Amygdala and hippocampus • Functions • Controls emotions • Influences basic body functions controlled by hypothalamus and brain stem

27. Cerebrum Thalamus Gathers sensory information before distribution to higher areas Basal nuclei Hippocampus Involved mainly with memory Olfactory bulbs Hypothalamus Amygdala Controls emotions, activates “fight or flight” self-preservation reactions Fig. 38.9, p. 876

28. The Cerebral Cortex Primary somatosensory areas • Register information on touch, pain, temperature, and pressure from all parts of the body • Right cerebral hemisphere receives sensory information from left side of body and vice versa • Primary motor areas control voluntary movements of skeletal muscles

29. Front Primary somatosensory area of left hemisphere Primary motor area of left hemisphere Back Left hemisphere Left hemisphere Cross-sectional view Cross-sectional view Fig. 38.11, p. 878

30. Association Areas of Cerebral Cortex • Integrate sensory information and formulate responses passed on to primary motor areas • Wernicke’s area • Integrates visual, auditory, other sensory information into comprehension of language • Broca’s area • Coordinates movements of lips, tongue, jaws, other structures to produce sounds of speech

31. General motor association area Primary motor area Frontal Association area (planning,personality) Primary somatosensory area General sensory association area Parietal lobe Wernicke’s area (understanding language) Frontal lobe Taste Visual association area Occipital lobe Smell Temporal lobe Broca’s area (expressing language) Primary visual cortex (visual input) Auditory area (hearing input) Cerebellum Auditory association area Facial recognition area (on inner side of cortex) Brain stem Fig. 38.10, p. 877

32. Lateralization of the Cerebral Hemispheres • Left hemisphere functions • Spoken and written language, abstract reasoning, precise mathematical calculations • Right hemisphere functions • Nonverbal conceptualizing, mathematical estimation, intuitive thinking, spatial recognition, artistic and musical abilities • Equal functions • Long-term memory and consciousness

33. Memory • Storage and retrieval of a sensory or motor experience or thought • Short-term memory involves temporary storage of information • Long-term memory is essentially permanent

34. Learning • Modification of a response through comparisons made with information or experiences stored in memory

35. Consciousness • Awareness of ourselves, our identity, and our surroundings • Varies through states from full alertness to sleep • Controlled by the reticular activating system

36. Awake (beta waves) Eyes closed, relaxed (alpha waves) Dozing (theta waves) Deep sleep (delta waves) Time (sec) Fig. 38.13, p. 882

37. Major Diseases of the Brain • Autism Spectrum Disorder • ADHD • Alzheimer’s Disease/Dementia • Schizophrenia

38. Autism Spectrum Disorder • In 2006, 1% or one child in every 110 was classified as having an ASD • Males: 1:70; females: 1:315. • Increased 57% from 2002 (Rice, December 18, 2009 / 58(SS10);1-20).

39. ASD People with autistic disorder usually have significant language delays, social and communication challenges, and unusual behaviors and interests People with Asperger syndrome usually have some milder symptoms of autistic disorder.  They might have social challenges and unusual behaviors and interests.  However, they typically do not have problems with language or intellectual disability.

40. ADHD • 4.5 million children 5-17 years of age have ever been diagnosed with ADHD as of 2006. • 3%-7% of school-aged children suffer from ADHD. Some studies have estimated higher rates in community samples • Boys (9.5%) are more likely than girls (5.9%) to have been diagnosed with ADHD. Diagnosis of ADHD increased an average of 3% per year from 1997 to 2006 (http://www.cdc.gov/ncbddd/adhd/data.html)

41. Types of ADHD Predominantly Inattentive Type: • Lack of organization or finish a task, • Unable to pay attention to details, or to follow instructions or conversations. • Easily distracted or forgets details of daily routines. Predominantly Hyperactive-Impulsive Type: • fidgets and talks a lot. • hard to sit still for long (e.g., for a meal or while doing homework). • Smaller children may run, jump or climb constantly. • Feels restless and has trouble with impulsivity. • May interrupt others a lot, grab things from people, or speak at inappropriate times Combined Type: Symptoms of the above two types are equally present in the person

42. Alzheimer’s Disease/Dementia • About 5% ages 65-74 year old • About 50% over 80 years old • An estimated 5 million Americans have Alzheimer’s disease. • This number has doubled since 1980 • It is expected to be as high as 13.4 million by 2050 • Individuals with Alzheimer’s disease make up less than 13 percent of the Medicare population, yet they account for 34 percent of Medicare spending.* • How old will you be in 2050? Who is paying the bill?

43. Schizophrenia • Affects 1.1 percent of the population • Onset usually after age 18 • Later in women • Often addicted to nicotine and other substances • Genetically linked

44. Symptoms • Positive: • Hallucinations (voices are common) • Delusions (religious or alien, or authority) • Thought disorders • Movement disorders • Negative: • Absence of pleasure, planning, enjoyment (affect), speaking, etc. • Cognitive defects: • Little understanding, trouble focusing, and little memory