Anatomy and Physiology Chapter 11 Nervous System II

1. Anatomy and Physiology Chapter 11 Nervous System II

2. Meninges • membranes surrounding CNS • protect CNS • three layers • dura mater – outer, tough • arachnoid mater – thin, weblike • pia mater – inner, very thin Chapter 11Nervous System II

3. Dura Mater • outermost layer • made of tough, white dense connective tissue • contains many blood vessels and nerves • attaches to inside of cranial cavity • some areas split into two layers which venous blood flows through

4. strong tubular sheath that surrounds the spinal cord • sheath is separated from spinal cord by an epidermal space which contains blood vessels, loose connective tissue, and adipose tissue

5. Arachnoid Mater • thin weblike membrane between dura and pia maters • lacks blood vessels • subarachnoid space between arachnoid and pia maters • contains cerebrospinal fluid (clear and watery)

6. Pia Mater • attached to brain and spinal cord • contains many nerves and blood vessels that nourish underlying cells

7. Meninges of the Spinal Cord

8. Ventricles and Cerebrospinal Fluid • Ventricles are interconnected cavities filled with cerebrospinal fluid (CSF) • CSF completely surrounds the brain and spinal cord providing protection • CSF helps maintain a stable ionic concentration • CSF provides a pathway to blood for waste

9. Ventricles

11. Cerebrospinal Fluid

12. Spinal Cord

13. Cross Section of Spinal Cord

14. Spinal Cord • Slender column of nerve fibers • Continuous with brain • Extends down through vertebral canal • Tapers and terminates near the disk between 1st and 2nd lumbar vetebrae • Fibers extend downward to become spinal nerves at the remaining lumbar and sacral levels – filum terminale

15. Structure of the Spinal Cord • 31 segments each of which gives rise to a pair of spinal nerves • Cervical enlargement – supplies nerves to upper limbs • Lumbar enlargement – supplies nerves to lower limbs

16. Functions of the Spinal Cord • Conduit for nerve impulse to and from the brain • Center for spinal reflexes • Nerve tracts and nerves spinal provide for 2 way communication between the brain and body parts outside the brain

17. Ascending tracts conduct sensory impulses to the brain • Descending tracts Conduct motor impulses from the brain to muscles and glands • Nerve fibers in the tracts are axons

18. Ascending Tracts

19. Descending Tracts

20. Reflex Arcs • Simple nerve pathways that carry out reflexes • Pathway: Receptor  sensory neuron  interneurons in CNS  motor neurons  effectors (muscles & glands)  • Spinal reflexes have reflex arcs that pass through the spinal cord

21. Reflex Behavior • Automatic and subconscious responses to stimuli inside or outside the body • Help maintain homeostasis by controlling many involuntary processes: heart rate, breathing rate, blood pressure and digestion • Also control involuntary actions: swallowing, sneezing, coughing and vomiting • Ex: patellar tendon reflex, withdrawal reflex

22. Reflex Behavior • example is the knee-jerk reflex • simple monosynaptic reflex • helps maintain an upright posture

23. Reflex Behavior • example is a withdrawal reflex • prevents or limits tissue damage

24. Brain Major Parts • cerebrum • two hemispheres • basal nuclei (ganglia) • diencephalon • brainstem • cerebellum

25. Brain- General functions • Largest and most complex part of NS • Has about one hundred billion multipolar neurons and innumerable nerve fibers • Responsible for sensations and perceptions • Issues motor commands and coordinates muscular movements

26. Regulates visceral activities • Responsible for reasoning and memory • Provides characteristics of personality

27. Brain

28. Brain Development • Forms during early embryonic stage • Begins as neural tube with 3 cavities (vesicles) that gives rise to the CNS • Walls of the tube give rise to various regions of the brain, brain stem, and spinal cord

29. Brain Development Three Major Vesicles • Forebrain • Midbrain • Hindbrain

30. Brain Development

31. Structure of the Cerebrum • Largest part of the mature brain • Consists of 2 large masses called cerebral hemispheres • Corpus callosum (bridge of nerve fibers) connects the 2 hemispheres • Convolutions (ridges) separated by grooves found on the surface • Sulcus – shallow groove • Fissure –deep groove

32. Lobes of the cerebral hemisphere are named after the skull bones they are under: frontal lobe, parietal lobe, temporal lobe, occipital lobe, and insula • Thin layer of gray matter (cerebral cortex) makes up the outermost portion and has about 75% of all nerve cell bodies in NS

33. Mass of white matter ( myelinated nerve fibers) under the cerebral cortex Some pass between hemispheres Some carry sensory or motor impulses

34. Structure of Cerebrum

35. Lobes of Cerebral Hemispheres • Frontal • Parietal • Temporal • Occipital • Insula

36. Functions of the Cerebral Lobes

37. Functions of the Cerebrum • Regions of the cerebral cortex perform specific functions • Primary motor areas – Fig 11.16 Pg 391 send impulses that cross from one side of the brain to the other within the brain stem • Sensory Areas – Fig 11.16 Pg 391 interpret impulses from sensory receptors

38. Motor Areas • Primary Motor Areas • frontal lobes • control voluntary muscles • Broca’s Area • anterior to primary motor cortex • usually in left hemisphere • controls muscles needed for speech • Frontal Eye Field • above Broca’s area • controls voluntary movements of eyes and eyelids

39. Sensory Areas • Cutaneous Sensory Area • parietal lobe • interprets sensations on skin • Sensory Area for Taste • near bases of the central sulci • Sensory Area for Smell • arise from centers deep within the cerebrum • Visual Area • occipital lobe • interprets vision • Auditory Area • temporal lobe • interprets hearing

40. Sensory & Motor Areas

41. Association Areas – interconnect with each other and with other brain structures - occupy anterior portions of frontal lobes and widespread in the lateral portions of the parietal, temporal, and occipital lobes

42. Association Areas Frontal Lobe Association Areas • concentrating • planning • complex problem solving Temporal Lobe Association Areas • interpret complex sensory experiences • store memories of visual scenes, music, and complex patterns Parietal Lobe Association Areas • understanding speech • choosing words to express thought Occipital Lobe Association Areas • analyze and combine visual images with other sensory experiences

43. General interpretive area – primary role in complex thought processing - located where the parietal, temporal, and occipital association areas join near the posterior end of the lateral sulcus

45. Hemisphere Dominance • Both hemispheres participate in basic functions such as receiving and interpreting sensory impulses, controlling skeletal muscles on the opposite side of the body, and storing memory • Most people have a dominant hemisphere for language related activities, and skills requiring verbal, analytical, and computational skills

46. 90% of people are left hemisphere dominant, some are right dominant, and some are equally dominant • Broca’s area on one side controls speech – usually the left side • Nondominant hemisphere specializes in nonverbal functions • Nerve fibers in the corpus callosum connect the hemispheres and transfer information

47. Hemisphere Dominance • The left hemisphere is dominant is most individuals • Nondominant hemisphere controls • nonverbal tasks • motor tasks • understanding and interpreting musical and visual patterns • provides emotional and intuitive thought processes • Dominant hemisphere controls • speech • writing • reading • verbal skills • analytical skills • computational skills

48. Memory Short Term • working memory • closed neuronal circuit • circuit is stimulated over and over • when impulse flow ceases, memory does also • unless it enters long-term memory via memory consolidation Long Term • changes structure or function of neurons • enhances synaptic transmission • 10 billion neurons can form 60 trillion synapses allowing limitless number of memories

49. Major Parts of the Brain

50. Basal Nuclei (ganglia) • masses of gray matter • deep within cerebral hemispheres • produces dopamine • controls certain muscular activities primarily by inhibiting motor functions