Biofisika Neuron 2013

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    BIOFISIKA NEURON(Biophysics of Neuron)

    Aqsa SjuhadaDept of Physiology / Oral Biology, Airlangga [email protected]

    s eyeem.com/asa

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    BODY LIQUIDTotal : 60% Intracellular: 40% Extracell: 20% (kecuali cair

    serebrospinal, cairan sendi, cairansaliva)

    - cairan interstitial 15%

    - cairan plasma 5%- cairan sel darah

    - cairan intra vaskuler

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    TRANSPORT BAHAN

    ACTIVE TRANSPORT

    1. primary

    2. secondary

    - bulk transport- exocytosis

    - endocytosis

    - phagocytosis

    - pinocytosis

    PASSIVE TRANSPORT

    - osmosis

    - diffusion

    - filtration- solvent drag

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    ACTIVETRANSPORT

    PASSIVETRANSPORT

    CELLULARENERGY

    required not required,only kineticenergy

    PROCESS physiology -

    biology

    physics

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    DIFFUSION

    Particle movement Simple diffusion : O2, CO2, alcohol Facilitated diffusion : glucose, amine acid

    OSMOSIS Liquid movement Hypotonic - Hypertonic

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    DIFFUSION

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    OSMOSIS

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    MACAM GERAKANDARI

    ARAHGERAKAN

    PLASMAMEMBRAN

    CARRIERSYSTEM

    ENERGYCELLULAR

    Osmosis

    Solvent CC SP Tidak Tidak

    Diffusi Solut CC +/- Tidak Tidak

    ActiveTransp

    Solut CC SP Ada Ada

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    eyeem.com/asa

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    SEL EKSITABELSel yg mampu menimbulkan /

    menjalankan impuls elektrokimiasepanjang membran plasmanya.

    Sel saraf, sel otot, sel kelenjar

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    MEMBRAN PLASMA

    STRUKTUR DAN KOMPOSISI MEMBRAN PLASMA Lemak dynamic mozaic design / lipid bilayer 42%

    Protein 55%

    Karbohidrat 3%

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    SIFAT- Elastis tipis, ketebalan 6-10nm

    FUNGSI Physical isolation Regulation of exchange with the

    environment --- nutrition, ion Sensitivity --- receptor function Structural support

    JENIS

    Impermeable Semi permeable Selective permeable

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    PROTEIN

    Sebagian besar glicoprotein

    Protein integral / protein perifer, fungsinya: membatasi pergerakan membran plasma

    sebagai channel carrier system enzyme receptor

    Karbohidrat; berada di luar berikatan dgglicoprotein maupun lipid bilayer, fungsi:sebagai indikator sel.

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    NEURON

    = Sel saraf

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    Dentrites

    Cell Body

    Axon

    Terminal

    A Typical Neuron Overview

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    Diverse Neuron Forms and Functions

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    Basic Concepts

    Volt

    A charge difference between twopoints in space

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    Basic Concepts

    Ions charged particles

    Anions Negatively chargedparticles

    Cations Positively chargedparticles

    B i C t

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    Basic ConceptsForces that determine ionic

    movement Electrostatic forces

    Opposite charges attract, Identical chargesrepel

    Concentration forces Diffusion movement of ions through

    semipermeable membrane Osmosis movement of water from region

    of high concentration to low

    Hydrostatic Forces Gravity forces upon osmosis

    The combination of these forces leads todynamic equilibrium in the cellular environment

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    POTENSIAL MEMBRAN Perbedaan muatan listrik di luar dan di

    dalam membran sel

    RMP =Resting Membran Potential =Potensial Membran Istirahat

    Berbedaan muatan listrik di luar dan didalam membran sel dalam keadaantidak ada aktivitas elektris.

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    Apa penyebab Resting MembranePotential mempunyai beda potensial-70 mV ?

    Adanya perbedaan distribusi ion di luar dan didalam membran sel, terutama ion K+ dan Na+

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    Perbedaan distribusi ion di luar dandi dalam membran

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    Besar RMP 70 mV Artinya ? Potensial elektriks di dalam membran sel

    lebih negatif dibandingkan di luarmembran sel sebesar 70mV

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    RANGSANGAN

    Adekuat Tidak adekuat

    Mencapai threshold Tidak mencapaithreshold

    POTENSIAL AKSI LOCAL POTENTIAL

    Dirambatkan ke segala arahTidak dirambatkan

    Hukum ALL OR NONE Sumasi

    angsangan

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    angsanganmenyebabkan Natrium+

    influx

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    Action Potential Sequence

    Involves the action of voltage-gated channels Exchanges of ions in and out of the cell

    Action Potential Stages:

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    Action Potential Stages:Overview

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    ANIMASI ACTION POTENTIAL

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    ActionPotential

    Sequence

    Saluran Na+ terbuka, terjadilah fast

    natrium influx, depolarisasi.

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    ActionPotential

    Sequence

    Pada keadaan +40 mV, saluran Na+ menutup, tetapi saluran K+ sekarangterbuka, menyebabkan pengeluaran ion K+ (gradien konsentrasi),menyebabkan penurunan gradien elektris.

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    ActionPotential

    Sequence

    Saluran K+ menutup, terjadilah

    akumulasi ion K+ di ekstrasel. Hal inimenyebabkan depolarisasi,sedemikian rupa sehingga terjadiundershoot pada akhir action potential

    Equilibrium

    membran

    potential

    dikembalikan

    i

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    ActionPotential

    Sequence

    Na+-K+ pump (pompa Na+-K+) berfungsi mengembalikan

    keadaan serupa, yaitu RMP.

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    Membrane & Channel Changes

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    Membrane & Channel Changesduring an Action Potential

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    Refractory Period

    Two types Absolute

    When Na+ channels close, at peakof AP, they do not reopen for a time

    Relative Membrane hyperpolarized

    Some Na+ channels still refractory

    P i f h A i

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    Propagation of the ActionPotential

    Action Potential spreads downthe axon in a chain reaction

    Unidirectional it does not spread into the cell body

    and dendrite due to absence ofvoltage-gated channels there

    Refraction prevents spread backacross axon

    P ti f th A ti

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    Propagation of the ActionPotential

    Speed of propagation varies withthe axon diameter

    Faster with larger axons In large axons of mammals

    5m/second 2m axons 20m/second in 20m axons

    P ti f th A ti

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    Propagation of the ActionPotential

    Speed of propagation alsoassisted by the myelin sheath Provides resistance to AP

    Regular gaps in the myelinsheath (1mm intervals) Nodes of Ranvier

    Increase conduction speed up to 15times

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    T i K ih

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    Terima Kasihwww.flickr.com/humanis

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