Anatomy The Nervous System

1. AnatomyThe Nervous System Chapter 9

2. Nervous system- master controlling & communicating system of body • 3 fxns: • senses changes within body & in the outside environment (sensory fxn) • interprets the changes (integrative fxn) • responds to the interpretation by initiating action in the form of muscular contractions or glandular secretions (motor fxn)

4. divided into 2 regions: 1. CNS- central nervous sys- control center for the entire system brain & spinal cord 2. PNS- peripheral nervous sys various nerve processes that connect brain & spinal cord w/ receptors , muscles, & glands

6. divided into: • afferent system- consists of nerve cells that convey info from receptors in muscles to brain these cells are afferent neurons 1st cells to pick up incoming info SENSORY b. efferent system- consists of neurons that convey info from CNS to muscles & glands efferent neurons MOTOR subdivided into:

7. somatic nervous system- made of efferent neurons that conduct impulses from CNS to skeletal muscle tissue voluntary control 2. autonomic nervous system- contains efferent neurons that convey impulses from CNS to smooth muscle tissue, cardiac muscle, & glands involuntary control subdivided into:

8. a. sympathetic division- stimulates or increases an organ’s activity b. parasympathetic division- decreases or inhibits an organ’s activity

9. Sympathetic vs. Parasympathetic Division 1. sympathetic – “fight or flight” system signs of SNS: -pounding heart -rapid, deep breathing -cold, sweaty skin -prickly scalp -dilated pupils

10. in scary situations, the Sym NS: • increases heart rate, blood pressure, bld glucose levels • increases bld flow to skeletal muscles • decreases bld flow to digestive sys • dilation of bronchioles in lungs hormones are released that bring about these changes- ADRENALIN

11. 2. parasympathetic “resting & digesting” system most active when body is at rest conserves body energy by decreasing demands on cardiovascular system

12. 2 types cells in nervous system: • neurons- aka nerve cells structural & functional unit of nervous sys *specialized to react to physical & chemical changes in surroundings 2. neuroglial- provide physical support, insulation, & nutrients for neurons

13. Neurons • cell body • dendrites • axons

14. Nerve transmission • in the form of electrochemical changes called nerve impulses • dendrites carry info toward cell body (Delivers) • axons carry info Away from cell body

16. Neuroglial Cells • aka glial cells • means “nerve glue” • provide structural frameworks, produce substances neurons may need, fill spaces, carry on phagocytosis • greatly outnumber neurons

17. Schwann cells • form myelin sheaths around PERIPHERAL NERVES • play imp role in regeneration of damaged nerves (because of neurolemma- living layer)

18. oligodendrocytes • align on nerve fibers • *produce myelin sheath that envelops brain & spinal cord nerves • can’t regenerate • no living layer

19. astrocytes • most numerous • name means “star cells” • large • found betw neurons & blood vessels; join parts together • form structure called “blood brain barrier” protects brain from harmful chemicals

20. microglial cells • smaller cells • usu stationary until inflammation • considered spider-like • can move & phagocytize when brain inflamed

21. ependymal cells • line cavities of brain & spinal cord • have cilia to circulate cerebrospinal fluid • looks almost like epithelial tissue

22. Development of Nervous System • nervous sys formed during 1st month of embryonic dev Probs: • rubella measles- deafness & other CNS complications • smoking- results in slight to heavy brain damage • drugs- brain damage to possible death • alcohol- fetal alcohol syndrome- brain damage to death

24. cerebral palsy- temporary lack of O2 during birth • results in poorly controlled skeletal muscles • seizures • brain damage (mild to severe) • impaired vision, hearing, speech

25. Brain disorders Most common types of brain tumors are those that develop from neuroglial cells- gliomas Head injuries: • concussion- slight brain injury • contusion- tissue destruction • cerebral edema- swelling of brain • intracranial hemorrhage- bleeding in brain

28. stroke- 3rd leading cause of death in US

29. Alzheimer’s Disease- results ultimately in dementia

30. CNS • brain – largest, most complex mass of nervous tissue • 4 major regions of brain: • cerebral hemisphere- aka cerebrum exhibits elevated ridges (mtns) gyri & deep grooves called fissures (shallow grooves- sulcus) 2 hemispheres of brain separated by single, deep fissure called longitudinal fissure

32. divided into lobes named by the bones that cover them • central fissure • cerebral cortex- surface of cerebrum contains billions of cells that function in speech, memory, logical & emotional responses, interpretation of sensation, consciousness, & voluntary movements

35. corpus callosum- large fiber tract that connects the 2 hemispheres in order for communication to occur betw 2 hemispheres • involved in several other fxn of the body: • eye movement • maintaining balance of arousal & attention • tactile localization

37. 2. Diencephalon (interbrain) • sits atop brain stem & surrounded by cerebral hemispheres • (region in brain) • 3 major structures:

38. thalamus- relay station for sensory impulses passing upward to sensory cortex • hypothalamus- (below thalamus) makes up floor of diencephalon • regulates body temp, H2O balance, & metabolism • center for emotions and drives • regulates pituitary gland (endocrine organ) which hangs from the floor of hypothalamus mammillary bodies bulge from floor – involved in smell & memory c. epithalamus- makes up roof; contains structures which secrete cerebrospinal fluid

39. Wimps need to put their heads down on their desks now!

41. 3. brain stem • controls vital activities like breathing & bld pressure • provides pathway for ascending & descending tracts • contains neurons involved in consciousness & awake/sleep cycles

42. 3 structures: • midbrain- convey ascending/descending impulses to regions in brain contains regions involved w/ hearing & vision b. pons- bridge for fiber tracts; involved in control of breathing c. medulla oblongata- most inferior part of brain merges into spinal cord helps control heart rate, bld pressure, breathing, swallowing, vomiting, etc

44. 4. cerebellum • “little brain” • projects dorsally under occipital lobe • provides precise timing for skeletal muscle activity, controls balance, and equilibrium

46. Protection of CNS • 3 coverings are the meninges: 1. dura mater- “tough mother” double-layered membrane attached to skull & is outermost covering of brain

47. 2. arachnoid mater- “spider mother” threadlike extensions that attach to 3rd layer this area is filled w/ cerebrospinal fluid 3. pia mater “ gentle mother” clings to surface of brain & spinal cord meningitis- infection of meninges

49. Wimps need to put their heads down on their desks now!