1. nervous tissue organization neurons neuroglia action potentials nerve conduction excitation or inhibition integration memory

4. nerve cells (neuron) excitability = stimuli result in an electrical impulse conductivity = impulse conducted to other cells secretory = neurotransmitter released to excite next cell sensory = afferent (in to PNS or CNS) motor = efferent (out to effectors) interneurons = (go to neurons in CNS)

5. neuroglia (supporting cells) majority of cells oligodendrocytes= wraps about nerves to form myelin sheath, insulates nerve fiber from extracellular fluid ependymal = cubed, line internal cavities of CNS, makes CSF microglia = small macrophages, dead cells, foreign matter, germs astrocytes = the most, support, form blood-brain barrier, regulate blood flow, glucose to lactate, secrete NGF, integration, recycle K & neurotransmitters, form scar tissue, cover all but synaptic areas Schwann cells = neurilemmocytes = envelop PNS, aids regeneration

8. neuron types multipolar = more than one dendrite into soma, one axon bipolar = one dendrite into soma, one axon unipolar = no dendrites touch soma, one axon anaxonic = more than one dendrite into soma, no axon, integration

10. different types of neurons have different rates of axonal transport speed antegrade & retrograde fast transport = mm/day= express slow axonal transport (antegrade) = mm/day=stop & go molecular motors use antegrade away from soma uses kinesin retrograde towards soma uses dynein

11. Myelin (fatty protein) wraps about neurons and increases conduction speed in CNS made by oligodendrocytes in PNS made by Schwann cells

13. regeneration after damage/cut - damage – followed by clean up, soma hypertrophies - distal ends degenerate – axon stump develops multiple processes – Schwann cells, basal lamina, & neurilemma form a regeneration tube + NGF & adhesion proteins – tube guides sprout to original target – connection reestablished & soma shrinks to normal size BUT- mistakes, wrong muscle, no muscle, die, 1-2 yrs

16. you pick up a hot spoon you perceive the heat you know that you want to drop the spoon you open your fingers and let go we do this for many stimuli every day so how does this action or reaction come about?

17. it starts with a nerve cell at rest having a resting membrane potential the interior of a nerve cell and the exterior of the cell have different electrical properties this difference is brought about by the concentrations of Na and K inside and outside of the cell brought about by the selective permeability of the cell membrane

18. -cell membrane is very permeable to K - at equilibrium K is 40 times as concentrated in ICF as ECF - at equilibrium Na is 12 times as concentrated in ECF as ICF - the difference in concentrations and the Na/K pump causes a RMP of -70mV - Na/K pump uses 70% of the energy needs of the nervous system diffusion, selective permeability, and ion concentration result in the electrical differences across the membrane which allows for nerve conduction to take place

19. stimulation of a neuron causes Na flows into ICF (into the cell) RMP shifts from negative to positive which generates a local potential that travels towards the trigger zone(axon hillock) local potential is graded according to strength of stimulus if an action potential is not generated does not reach threshold it degrades as it spreads and the RMP returns to -70 mV ICF

20. If enough units of muscles or dendrites are excited the local action potentials can build upon each other and spread to the trigger zone and initiate an self propagating action potential

23. action potential - local potential to axon hillock – depolarizes membrane – if voltage reaches -55 mV - Na gates open quickly – Na enters cell – voltage rises to +35 to +50 – K channels open slowly – Na channels close – K channels fully open – K leaves cell – repolarization as K leaves – hyperpolarization by K – Na diffuses back into cell – repolarization to -70 mV – in CNS astrocytes remove K from ECF

24. refractory period a period of time during which it is impossible to stimulate that area of a neuron to generate a second action potential absolute refractory = even if strong stimulus cannot evoke an AP relative refractory = needs a strong stimulus to evoke an AP

25. nerve conduction action potential move down axon unmyelinated fiber = has voltage gated channels along total length AP reaches axon hillock AP moves distally along axon AP is self propagating AP moves at up to 2 m/sec

27. Myelinated nerve fiber - incoming stimulus generates action potential - AP travels down axon by saltatory conduction - AP deteriorates as it travels down axon - AP are reenergized at each node - AP occurs only at nodes - AP does not jump over nodes - fast conduction up to 120 m/sec

33. it was less than 100 years ago that Otto Loewi showed that communication between nerves and nerves and nerves and muscles was chemical not electrical thus was born the study of synapses and neurotransmitters

34. synapses presynaptic may contact a dendrite, a soma, or postsynaptic axon a postsynaptic becomes presynaptic to the next order of neurons scientists have discovered more than 100 neurotransmitters

36. synaptic transmission - AP reaches synaptic knob – Ca gated channels open – Ca enters synaptic knob – exocytosis of NT from knob – empty vesicles recycled and refilled with NT – ACh diffuses across synaptic cleft – binds to postsynaptic receptors which open Na channels – Na rushes in and depolarizes postsynaptic cell – if potential change is strong enough it reaches axon hillock of cell – causes postsynaptic cell to fire an AP this is an example of an excitatory synaptic event as an inhibitory event Ach would cause hyperpolarization

38. adrenergic NE synapse presynapse releases NE – binds to postsynaptic membrane – G protein activated – G protein binds to adenyl cyclase - (ATP becomes cAMP) – cAMP binds to membrane and opens receptor which allows ions in to depolarize cell – or – activates cytoplasmic enzymes – or – activates genetic transcription slower than ACh but NE activity accompanied by amplification can be ↑ or ↓

39. neurotransmitters acetylcholine amino acids = glycine↓, glutamate↑, aspartate↑, GABA↓ monoamines = epi, NE, dopa, = catecholamines histamines, serotonin, ATP neuropeptides = cholecystokinin, sub P, enkephalins, endorphins neuromodulating hormones = long term effectors = NO, dopa, serotonin, histamine ACh and NE can be ↑ or ↓ depending on situation

40. If neurotransmitter remains in synaptic cleft it causes excess stimulation of postsynaptic cell the result is too much activation or too much inhibition neurotransmitters are reabsorbed by astrocytes and presynaptic cell and enzymes

41. there is a reason that neurons have many dendrites and many terminal arborizations your CNS and PNS do not operate on a 1 to 1 basis each neuron receives input from more than 1 neuron and send their action potentials to more than 1 neuron the result of an AP is therefore the result of many inputs some excitatory and some inhibitory or it is the result of neural integration

45. 10,000 inputs to get 1 output it is estimated that a spinal neuron has 8,000 synapses on dendrites 2,000 synapses on soma cerebellum estimates are 100,000 inputs why information processing (integration)

46. here are a bunch of terms to know summation = E +I results in net effect, takes place in trigger zone temporal sum=rapid input from 1 causes LPs to reach threshold and AP spatial sum = input from many add LPs to threshold and AP produced facilitation = 1 neuron makes another more likely to fire presynaptic inhibition = 1 neuron makes another less likely to fire divergence = one stimulus causes AP in many neurons convergence = stimuli from many neurons affect one neuron recruitment = as stimulus↑ affects more neurons neural coding = convert synapses into meaningful pattern of Aps neural pool = all of the + and – used to determine an effect labelled line code = info to brain recognized as coming from a specific stimulus