BIO 203 Lecture Notes - Lecture 14: Subarachnoid Space, Cerebrospinal Fluid, Afferent Nerve Fiber

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Lecture'14:'Nervous'System'
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1.#Explain#the#function#of#cerebral#spinal#fluid#and#blood#brain#barrier#in#CNS.##
The'Brain'Floats'in'Cerebrospinal'Fluid'(CSF)'
!!surrounds!entire!brain!
o!contained!within!subarachnoid!space!
o!flows!from!ventricles!(interior)!to!subarachnoid!space!to!return!to!plasma!by!villi!(movement!is!provided!
by!villi!along!the!cells)!
"!ventricles!=!circulatory!system!for!CSF!
o!provides!physical!and!chemical!protection!!
"!cushion!
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The'Blood@Brain'Barrier'Protects'the'Brain'
!!highly!selective!permeability!of!brain!capillaries!
!!astrocytes!foot!processes!promote!tight'junctions'between'endothelial'cells!
!!protects!brain!from!toxic!water!soluble!compounds!and!pathogens!
!!small#lipid;soluble#molecules!cross!the!blood>brain!barrier!
o!gases,!O2,!CO2!
!!membrane!transporters!move!glucose!through!BBB!
o!glucose!is!the!only!source!of!fuel!for!the!brain!!
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Neural'Tissue'Has'Special'Metabolic'Requirements'
!!neurons!need!a!constant!supply!of!oxygen!and!glucose!
o!unable!to!use!fatty!acids!or!proteins!for!their!metabolism!
!!brain!receives!15%!of!blood!pumped!by!heart!!
o!large!portion!
!!Oxygen#
o!passes'freely'across'BBB'
!!Glucose#
o!membrane'transporters!move!glucose!form!plasma!into!the!
brain!and!interstitial!fluid!
o!brain!responsible!for!about!half!of!body’s!glucose!
consumption!
o!progressive!hypoglycemia!leads!to!confusion,!
unconsciousness,!and!death!!
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2.#Identify#general#properties#of#sensory#systems.##
General!Properties!of!Sensory!Systems!
!!special!senses:!vision,!hearing,!taste,!smell,!equilibrium/balance!
!!somatic!senses:!touch,!temperature,!pain!itch,!proprioception!
(proprioceptors)!
o!senses!of!the!body!
!!stimulus!–!physical!energy!that!is!detected!by!a!sensory!receptor!
o!receptor!acts!as!a!transducer:!converts!a!chemical!stimulus!
into!some!kind!of!depolarization!#!if!high!enough!(threshold)!
#!AP!#!afferent!neuron!#!CNS!
"!receptor!is!responsible!for!monitoring!sensory!stimuli!
!!variety!of!complexity!of!sensory!neurons!
o!simple:!single!sensory!neuron!
o!complex:!multicellular!sense!organs!
"!separate!receptor!cells!&!afferents!!
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4#Major#groups#of#Receptors!(which!are!sensitive!to!particular!forms!of!energy)!
Chemoreceptors:!respond!to!chemical!ligands!(sensitive!
to!chemicals)!
!!i.e.!taste,!smell!
Mechanoreceptors:!respond!to!mechanical!energy!
pressure!and!sound!
!!i.e.!hearing!(vibrations),!touch!
!!includes!baroreceptors!(BP)!
Thermoreceptors:!respond!to!temperature!
Photoreceptors:!respond!to!light!(for!vision)!!
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Sensory(Receptors:!can!be!depolarized!or!hyperpolarized!
Simple#Receptors#
Complex#Neural#Receptors#
Nonneural#Sensory#Receptors#
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>!free!nerve!endings!=!dendrites!that!
stimulus!depolarizes!
>!myelinated!or!unmyelinated!!
@'no'modification'of'nerve'ending'
>!i.e.!chemical!stimulus!#!
chemoreceptors!at!free!nerve!
ending!!
>!mech.!R!#!layers!of!connective!
tissue!will!vibrate!as!well!
>!some'modification'of'nerve'ending!
>!when!receptor!is!a!completely!
different!cell!!
>!hair!cell:!used!for!hearing!
(deflected!by!sound!waves)!
>!completely'different/separate'nerve'
ending!
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Sensory'Transduction'Converts'Stimuli'into'Graded'Potentials!–!nervous!system!communicated!via!membrane!potential!
changes!
!!transduction:!stimulus!energy!converted!into!information!processed!by!nervous!system!(change!in!membrane!
potential)!
o!ion!channels!or!second!messengers!initiate!membrane!potential!change!!
!!receptor#potential#(graded#potential):#change!in!sensory!receptor!membrane!potential!
!!threshold:!minimum!stimulus!needed!to!fire!AP!in!afferent!!
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Document Summary

Explain the function of cerebral spinal fluid and blood brain barrier in cns. The brain floats in cerebrospinal fluid (csf) The blood- brain barrier protects the brain. Highly selective permeability of brain capillaries. Astrocytes foot processes promote tight junctions between endothelial cells. Protects brain from toxic water soluble compounds and pathogens. Small lipid- soluble molecules cross the blood- brain barrier: gases, o2, co2. Membrane transporters move glucose through bbb: glucose is the only source of fuel for the brain. Neural tissue has special metabolic requirements. Brain receives 15% of blood pumped by heart large portion. Oxygen: passes freely across bbb. General properties of sensory systems. Special senses: vision, hearing, taste, smell, equilibrium/balance. Somatic senses: touch, temperature, pain itch, proprioception (proprioceptors: senses of the body. Ap afferent neuron cns receptor is responsible for monitoring sensory stimuli. Variety of complexity of sensory neurons: simple: single sensory neuron, complex: multicellular sense organs separate receptor cells & afferents.

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