The Nervous System NS and Endocrine System Transmit info from 1 part of body to another

1. The Nervous System • NS and Endocrine System • Transmit info from 1 part of body to another • Communication—Integration--Control • Nervous System • Rapidly & short duration via nerve impulses • Endocrine System • Slowly via hormones (chemicals) secreted by • ductless glands into blood stream circulated • from glands to other parts of the body (target cells)

2. Homeostasis: Balanced & Controlled internal environment of body essential to fx of all body systems  relies on physiological control & integration NS: Monitors & Responds to In/External stimuli

3. Nervous System brain & spinal cordnerves & associated cells not part of CNS CNS PNS Sensory Nerves Motor Nerves Respond to stimuli from Env Sensory Receptors w/in sense organs (Eyes, Ears, Taste, Touch, Smell) Somatic NS Autonomic NS To cardiac & smooth muscles, glands, involuntary To skeletal muscles/voluntary parasympathetic sympathetic Fight/Flight Antagonistic gas ↑ brake ↓

4. Coverings & Fluid Spaces of Brain & Spinal Cord Meninges: Tough, fluid containing membrane surrounded by bone (skull & vertebrae) 3 Layers of Spinal Meninges Dura Mater (tough outer layer, lines vertebral canal) Pia Mater ( innermost layer covering spinal cord) Arachnoid Layer ( middle layer between Dura & Pia) cob web like w/ fluid (CSF) filling spaces Meninges (protective) extend up & around enclosing brain

7. Fluid fills Arachnoid spaces of brain meninges & spinal cord Cerebral Ventricles: Fluid filled spaces w/in brain 2 lateral ventricles deep w/in brain w/in Lt & Rt cerebrum (lgst part of brain conscious, voluntary, mental processes, emotions) CSF: cerebral spinal fluid forms continuously from fluid filtering out of blood  network of brain capillaries (choroid plexus) & into ventricles

8. From lateral ventricles CSF  3rd ventricle & flows ↓ aqueduct of Sylvius  4th ventricle  subarachnoid spaces  subarachnoid spaces of meninges that surround spinal cord  blood via veins in the brain ***CSF forms continuously from blood, circulates & is reabsorbed into blood again **Pressure on Aqueduct of Sylvius (Ex. brain tumor) blocks return path of CSF  blood CSF accumulates in ventricles or meninges. Hydrocephalus  water on the brain Treatment  catheter to drain fluid back to body

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10. 3 Types of Neurons Sensory Neurons (Afferent): Carry impulses from sense organs to spinal cord/brain (CNS) Dendrites can be very long Motor Neurons (Efferent): Carry impulses from CNS (brain/sc) (Effecter) to muscles & glands Interneurons (Central or Connecting): Connect sensory & motor neurons in spinal cord Lie w/in gray matter of CNS

11. Cells of the Nervous System Neurons & Neuroglia Basic Neuron Structure sensory, motor, & interneurons (between sensory & motor neurons in spinal column) Soma Cell body Many dendrites Impulse received by dendrites Myelinated axon carries impulse from cell body  axon terminals Axon terminals vesicles w/ neurotransmitters Saltatory conduction **vertebrates

12. Mostly outside CNS 80% lipid 20% protein Insulated sheath White Matter Indentations between Schwann cells Axons in brain & sc have no neurilemma  no regeneration but those in nerves do  regeneration Extend thru axon from cell body Saltatory Conduction: carries impulse node to node (vertebrates) 200 m/s vs few mm/s in unmyelinated (gray matter)

13. Neuroglias (connective tissue) Special connecting & supporting tissues of brain & spinal cord don’t transmit impulses Glia (glue): hold neurons together & protects them Glioma: common type of brain tumor develops from neuroglia cells 3 Types of Neuroglia Astrocytes:

14. Microglia: usually stationary can move & become phagocytic (scavengers)

15. Oligodendroglia: hold nerve fibers together & produce fatty myelin sheath that covers nerve fibers (axons) in brain & spinal cord (not Schwann Cells  outside CNS) Myelinated fibers (high fat  white matter) Nonmyelinated  (gray matter)

16. Myelin Disorder  Diseases associated with Oligodendroglia Multiple Sclerosis: Most common 10 of CNS Characterized by myelin loss/ destruction w/ oligodendroglial cell injury/death  demyelination of white matter of CNS  nerve conduction impaired  weakness, in-coordination, visual impairment, speech disturbances Afflicts more women between 20-40 MS ??? Related to autoimmunity & viral type infections Prolonged disease w/ relapses & remissions

17. White Matter in brain & Spinal cord made up of Tracts Tract: bundle of myelinated axons White Matter outside brain & spinal cord = nerves Nerves  bundles of myelinated axons single group of nerve fibers surrounded by connective tissue sheath Nerve Trunk group of bundled nerves

20. Nerve prs 8 7 cervical vertebrae 12 12 thoracic vertebrae 5 5 lumbar vertebrae 5 Fused vertebrae 1 coccyx

21. Reflex Arcs  impulse conduction in 1 Direction 2 neuron arc (sensory  motor) 3 neuron arc (sensory  interneuron  motor neuron) Interneurons w/in gray matter (H-zone)

22. Synapse: (microscopic space between neurons that neurotransmitters released from axon terminals diffuse across)

23. Sensory neuron receptors w/ dendrites pick up stimulus  impulse created  cell body  axon of sensory neuron Synapse  interneuron (dendrite  cell body axon)  synapse  motor neuron (dendrite  cell body  axon)  neuromuscular junction

26. Posterior root ganglion Anterior root spinal nerve Patellar Tendon Knee Jerk Reflex

27. Infant Reflexes Rooting Reflex: stroke cheek/ turns head towards touch Gripping Reflex: grasp anything placed in palm Toe Curling Reflex: Inner sole of foot stroked  toes curl Outer sole of foot stroked  toes spread Stepping Reflex: Held up w/ feet on surface  walk/march Sucking Reflex: when something touches roof of mouth Startle/Moro Reflex: sudden sound/mvmt  throw arms & legs out & head back then pull limbs back into body Galant Reflex: stroke middle or lower back  body curves towards side stroked Tonic Neck Reflex: place on stomach  whichever side head is facing  limbs on that side straighten, opposite side curl

28. The Nerve Impulse Initiated by a stimulus (pressure, temp, chemical changes, etc) Resting Neuron Outisde +++ (Resting Potential) Inside --- Na+ ions pumped out and K+ ions pumped in Na/K pump run by ATP  Active Transport More K+ ions leak out than Na+ ions leak in creating +++ Outside c.m Resting Potential --- Inside c.m (Also other ions present Ex. Cl-) C.M has gates/channels that allow ions to pass thru  normally closed

29. Steps of an Action Potential (Nerve Impulse) Neuron stimulated  nerve impulse generated Na+ gates open & flow inside C.M. Inside becomes more + than outside  Action Potential Nerve Impulse Depolarization As impulse passes, K+ gates open and K+ ions flow out  Inside becomes – and outside + again (Reploarization) Threshold: minimal level of stimulus required to create impulse  All or none Impulse moves in 1 direction b/c Na+ gates close after impulse & can’t be reopened for short time (Refractory Period)

30. Link to Action Potential Animation w/ Saltatory Conduction http://www.blackwellpublishing.com/matthews/actionp.html Resting Potential Action Potential Na+ rush in Depolarization Re-polarization – Action Potential – Resting Potential

31. Resting Potential Re-polarization Refractory Period

32. Action Potential reaches Axon Terminal Vesicles w/ neurotransmitters rupture  chemicals released  diffuse across synaptic cleft (assist, stimulate or inhibit postsynaptic neurons) Neurotransmitters: chemicals used by neuron to transmit impulse across synapse to another neuron or cell (Ex. muscle) *neuromuscular junction

33. Impulse arrives at axon terminal • Vesicles release neurotransmitters into synaptic cleft/gap • Neurotransmitters diffuse across synapse & attach to • receptors on next cell • Stimulus causes rush of Na+ to rush into cell • If threshold met/exceeded new impulse or Rx occurs • Ex. muscle contraction • Neurotransmitters quickly: broken ↓ by enzymes • taken up/recycled by axon terminal • diffuse away

34. Certain Illnesses associated w/ abnormal levels of Neurotransmitters Depression: ↓ serotonin & norepinephrine (Exercise releases these) Schizophrenia: associated w/ ↑ levels of dopamine Parkinson’s Disease:progressive NS disease most often after age of 50, associated with the destruction of brain cells that produce dopamine, characterized by muscular tremor, slowing of movement, partial facial paralysis, peculiarity of gait and posture. Endorphins & Enkephalins: Inhibit conduction of pain impulses How do abnormal levels of neurotransmitters affect Fx of NS? Either ↑ or ↓ transmission of nerve impulse

35. Nerve Gas: Class of Lethal Weapons Fx: Inactivate certain enzymes of nerve transmission Normal: neurotransmitters diffuse away, recycled, inactivated Neurotransmitter Acetylcholine is inactivated by cholinesterase enzymes that deactivate acetylcholine quickly  efficient, precise synaptic transmission Nerve Gas: binds to & inhibits cholinesterase so acetylcholine remains in synapse  continuous stimulation of nerves  Uncontrollable convulsions, muscular contractions, death

36. Synaptic Integration: Provides checks & balances in NS • At each neuron, Excitatory & Inhibitory receptors compete for membrane control • Signals can totally/partially cancel each other out or augment each other’s effect • Net outcomes depend on strength, direction & location of each signal. • Clostridium tetani Produces toxin that interferes w/ Inhibitory Receptors & Motor Neurons in CNS (brain/sc) • Lock jaw  unbalanced excitation of muscle cells • constant (tetanic) contraction  spastic paralysis  death

37. Structure of the Spinal Cord • Avg adult spinal cord 17-18” long • Lies inside spinal column in spinal cavity • Extends from occipital bone to 1st lumbar vertebrae • Hands on hips  L4 • Spinal meninges extend beyond spinal cord • almost to end of spinal column • Allows for spinal tap (lumbar puncture) to extract CSF (test) • insert needle just above L4

38. Spinal Cord • H- shaped  gray matter ( dendrites & cell bodies of • neurons) • White matter outer part (bundles of myelinated nerve fibers) •  spinal tracts • Ascending tracts  conduct impulses ↑ cord to brain • Ex. sensory fx (pain, touch pressure, etc) • Descending tracts  conduct impulses ↓ cord from brain • Ex. vol. mvmts, skeletal muscle activity

40. Spinal Cord fxs as Switchboard Carries impulses to & from brain To brain via ascending tracts From brain via motor tracts Contains centers for Reflex Arcs Interneurons switch/transfer incoming sensory impulses to outgoing motor impulses  Spinal Cord Reflex Arc 2 kinds withdrawal reflex (Ex. from hot/sharp surface) knee jerk reflex Injury cuts spinal cord across impulses can’t pass produces Loss of sensation  Anesthesia Loss of ability to move  paralysis

41. Spinal Nerves (31 prs) 8 cervical (7 cervial vertebrae) 12 thoracic (12 thoracic vertebrae) 5 lumbar 5 (5 lumbar vertebrae) Sacrospinal (fused vertebrae) 1 coccygeal (coccyx) Conduct impulses between spinal cord & areas not supplied by 12 cranial nerves Contain both sensory & motor fibers  sensation  mvmt

42. Nerve prs 8 7 cervical vertebrae 12 12 thoracic vertebrae 5 5 lumbar vertebrae 5 Fused vertebrae 1 coccyx

43. Dermatome: skin surface area supplied by single nerve Herpes Zoster/Shingles: viral infection of single dermatome caused by varicella zoster virus of chicken pox Virus travel thru cutaneous nerve & remains dormant in dorsal root ganglion long after chicken pox infection ↓ Immune Response (Ex. elderly, stress, radiation, immunosuppresive drugs  virus may reactivate  Virus travels over sensory nerve to skin of single dermatome  painful eruption vesicles, crust & clear 2-3wks

46. PNS Outside CNS Nerves & associated cells not part of CNS (brain & s.c) Consists of: cranial nerves that pass thru skull  stimulate head & neck Spinal nerves: 31 prs Ganglia: (nerve cell bodies)

47. Sensory Division of PNS: transmits impulses from sense organs  CNS Motor Division of PNS: transmits impulses from CNS  muscles/glands (Effectors) Somatic NS  voluntary Skeletal muscle contraction Some also use reflex arc Autonomic NS  Involuntary Ex. smooth muscles, digestion pupils reflex Sympathetic ↑ Effect (gas) Parasympathetic ↓Effect (brake)

48. Running: Sympathetic NS ↑ heart rate, blood flow to skeletal muscles, stimulates sweat & adrenal glands Parasympathetic NS ↓ smooth muscle contractions in digestive system Stop Running: Parasympathetic NS ↓ heart rate & blood flow to skeletal muscles Sympathetic NS ↑ contractions of smooth muscles in digestive system Important Fx  Maintaining Homeostasis

49. Divisions of the Brain Billions of Neurons 1.4kg Must have continuous supply of O2 Part of brain that is damaged  determines effects Wavy bumps/folds: gyri (gyrus) Shallow grooves: sulci (sulcus) Folds/Grooves ↑S.A for more neurons (S&F)

50. Gyri: folds Sulci: grooves