Nervous System

1. Nervous System

2. Nervous System master control system master communicating center • nerve tissue develops from embryonic ectoderm

3. Role of the Nervous System • monitors changes - (sensory function) • processes and interprets information - (integrative) • elicits responses - (motor)

4. Nervous System Organization • anatomical organization - central nervous system (CNS) - peripheral nervous system (PNS) • functional organization - sensory - integrative - motor

5. Central Nervous System (CNS) • brain - cerebrum - diencephalon - brain stem - cerebellum • spinal cord - continuation of brain stem - continues from base of skull to the 1st lumbar vertebra four principal parts

6. diencephalon cerebrum pituitary gland midbrain brain stem cerebellum pons medulla oblongata spinal cord

7. Peripheral Nervous System (PNS) • cranial nerves - 12 pairs - emerge from the brain • spinal nerves - 31 pairs - emerge from the spinal cord

8. Functional Organization • sensory - gathers information that occurs within internal and external environment • integrative - analyzes sensory information - decides necessary responses • motor - carries instructions (nerve impulses) to muscles and glands (effectors)

9. Basic Types of Functional Neurons

10. Sensory Neurons • afferent neurons - carry information from various body parts to the brain or spinal cord (input) Motor Neurons • efferent neurons - carry instructions from the CNS to muscles and glands (output)

11. Interneurons or Connecting Neurons • analyze information • determine appropriate response • located in the CNS

12. Peripheral Nervous System(subdivisions) • somatic nervous system (soma = body) - voluntary - sensations are consciously perceived • autonomic nervous system (auto = self) - involuntary and automatic - sensations are usually not consciously perceived

13. Somatic Nervous System(SNS) • sensory neurons - carry impulses to the CNS from receptors for general and special senses (touch, pressure, vibration, temperature, pain, proprioception, smell, taste, vision,hearing and equilibrium) • motor neurons - carry impulses away from CNS only to skeletal muscles

14. Autonomic Nervous System(ANS) • sensory neurons - carry impulses to the CNS from visceral receptors (internal organs) • motor neurons - carry impulses from CNS to smooth muscle, cardiac muscle, and glands

15. Motor Division of Autonomic Nervous System Two principal divisions work together, i.e., impulses of one division activate an organ, while impulses from the other division inhibit the organ • sympathetic • parasympathetic

16. Sympathetic • prepares the body for energy-expending, stressful, or emergency situations Parasympathetic • active under normal ordinary, restful conditions • counterbalances effects of sympathetic division • restores body to resting state

17. Protection and Coverings of the Brain • bones of cranium • cerebrospinal fluid • connective tissue membranes called meninges • vertebral column

18. Cranium • frontal • sphenoid • ethmoid • occipital • parietal • temporal

19. Cerebrospinal Fluid(CSF) • formed by filtration and secretion from networks of capillaries - choroid plexuses located in the (4) ventricles of the brain form blood-brain barrier • clear, colorless liquid • contains glucose, proteins, lactic acid, urea, cations, anions, and lymphocytes

20. Cerebrospinal Fluid (cont.) • acts as shock-absorbing medium • protects brain from banging against inner walls of cranium • is a medium for exchange of nutrients and waste products between blood and nervous tissue

21. Cerebrospinal Fluid (cont.) • significant changes in composition can indicate disease conditions - meningitis - tumors - multiple sclerosis • if drainage of CSF is obstructed, excessive pressure on the brain will cause hydrocephalus

22. Blood-Brain Barrier • permits certain substances to enter the fluid but prohibits others • protects the brain from harmful substances • formed by tightly adherent cell connections

23. Meninges • protective membranes • delicate • envelop brain and spinal cord • Three connective tissue membranes: - dura mater - arachnoid - pia mater

24. Dura Mater • outermost layer • leathery • next to bony inner surface of cranium • separated from arachnoid by subdural space which is fluid filled

25. Arachnoid • middle layer • looks like a cobweb • Two components: - layer next to the subdural space - system of supporting fibers (trabeculae) forming web-like structure between arachnoid and pia mater

26. Arachnoid (cont.) • in some areas, arachnoid material perforates dura mater forming protrusions called arachnoid villa • Functions: - reabsorption of CSF into blood

27. Pia Mater • innermost • thin layer of loose connective tissue • transparent • contains many blood vessels • between pia mater and nerve tissue is a thin layer of neuroglial processes firmly attached to pia mater

28. Meningitis • inflammation of meninges • serious threat to brain • bacterial and viral meningitis can spread to nervous tissue of CNS

29. Regions of the Brain • cerebrum (cerebral hemisphere ) • diencephalon • brain stem • cerebellum

30. Cerebrum (cerebral hemisphere) • largest, obscures most of brain stem • looks like mushroom cap • made up of 2 deeply grooved hemispheres - left and right • Surface is covered by: - grooves - fissures or sulci - ridges - gyri or convolutions which serve as landmarks

31. Cerebrum (con’t) • concerned with higher brain functions • Contains centers for: - interpreting sensory impulses - initiating voluntary muscular movements • stores information of memory • utilizes information in reasoning processes • functions in determining a person’s intelligence and personality

32. Left Hemisphere • More important for: - right-hand control - spoken and written language - numerical and scientific skills - reasoning

33. Right Hemisphere • More important for: - left-hand control - musical and artistic awareness - space and pattern perception - insight and imagination

34. Lobes • each hemisphere is subdivided into 4 lobes • named for cranial bone that covers them • more precisely defined by surface landmarks, i.e., sulci and fissures

35. Lobes (cont.) • parietal lobe • occipital lobe • temporal lobe • frontal lobe

36. White Matter • underlying the cortex • whitish appearance is due to fatty component of myelin • consists of myelinated axons extending in three principal directions - association fibers - commissural fibers - projection fibers

37. Association Fibers • connect and transmit impulses between gyri in the same hemispheres

38. Commissural Fibers • transmit impulses from the gyri in one cerebral hemisphere to corresponding gyri in the opposite hemisphere

39. Three Important Commissural Fibers • corpus callosum (corpus = mass or body) - great commissure of the brain between the cerebral hemispheres • anterior commissure • posterior commissure

40. Projection Fibers • form descending and ascending tracts • tracts transmit impulses from cerebrum and other parts of brain to spinal cord • tracts transmit impulses from spinal cord to brain

41. Gray Matter • made primarily of densely packed neuron cell bodies • basal ganglia - paired masses of gray matter - found in cerebral hemispheres • cerebral cortex - layer of gray matter approx. 3 mm thick - has 6 distinct layers - divided into 3 areas based on function

42. Cerebral Hemisphere • outer layer of gray matter is cerebral cortex - made up of lobes composed of dendrites and cell body neurons - interior is composed of white matter (nerve fibers arranged in bundles called tracts)

43. Functions of Cerebral Cortex • divided into three main areas based on function - sensory area - motor area - association area

44. Sensory Areas • Function in interpreting impulses, located in several lobes of cerebrum - general sensory area - primary visual area - primary auditory area - primary gustatory area - primary olfactory area

45. Sensory Areas general sensory primary gustatory primary visual primary auditory

46. General Sensory Area • Receives impulses from: - the skin - muscles - internal organs • localizes precisely where sensations originate • located on the postcentral gryus on the occipital lobe

47. Primary Visual Area • receives input from the eyes • Interprets: - shape - color - movement • located on the occipital lobes

48. Primary Auditory Area (cont.) • receives input from internal ear (cochlea) • Interprets: - pitch - rhythm • located on the temporal lobes

49. Primary Gustatory Area • receives input from taste buds • Interprets: - sensations related to taste (sweet, sour, salty, bitter) • located at base of postcentral gryus on parietal lobes

50. Primary Olfactory Area • receives input from olfactory bulbs • Interprets: - sensations related to smell • located on temporal lobes