neuronal anatomy and action potential

8/17/2019 Neuronal Anatomy and Action Potential

1/26

Neuronal

Anatomy andElectrophysiology

CAPE U2 Biology

R.Wint


2/26

Objectives1. Compare the signalling function of nervous system vs endocrine system.

2. Classify the division of the nervous system into central and peripheralith their su!divisions

". #tate the three characteristics of neruons that ma$e them adapted fortheir function

%. &escri!e the structure of sensory neuron

'. &escri!e structure of motor neuron

(. &escri!e structure of interneuron

). &e*ne the terms+ ,mem!rane potential- ,action potential- ,thresholdvoltage- ,depolarisation- hyperpolarisation-

/. E0plain ho the resting mem!rane potential arises in nerurons a3 4 3 ions5

6. E0plain the role of neurolemma in maintaining resting mem!ranepotential

17.8utline the steps of an action potential including refractory period

11.E0plain synaptic transmission

12.8utline the steps of cholinergic synpatic transmission

1".&escri!e the role of synapses e0citatory and inhi!itoryneurotransmitters5


3/26

Neurons

• 9he neuron is a highly speciali:edcell type and is the essential cellularelement in the C#.

• ;ore importantly neurons formcircuits and these circuits constitutethe structural !asis for !rain function


4/26

Neuronal Communication

• Communication !yneurons largelyconsists of long<

distance electricalsignals and short<distance chemicalsignals.


5/26

Typical Neuron Parts

• Cell body (soma): contains most of organelles includingnucleus

• Nissl bodies: condensed stac$s of rough endoplasmicreticulum

• endrites: !ranched processes e0tending from cell !odythat receive signals from other neurons=tissues

• A!on: an e0tension that transmit signals to other cells.

• A!on hilloc": cone !ase of a0on> here an actionpotential is generated

• #ynaptic terminal buds: terminal part of the a0on thatsecretes neurotransmitters.

• #ynapse: ?unction !eteen the synaptic terminal of ana0on and another cell


6/26


7/26


8/26

#tructural iversity o$Neurons

• " main functional types of neurons+

• #ensory neuron: detect stimuliand transmit signals to C#

• %nterneuron: con*ned in C#>analyse and interpret signals

• &otor neuron: transmit signal toe@ectors

• 'anglion (ganglia pl): a cluster ofinterneurons in the C#


9/26

ruc ure oNeurons


10/26

esting &embranePotential

• &embrane potential arises henthere is an uneual distri!ution ofcharges ions5 across the plasma

mem!rane.

• esting membrane potential of aneuron is the mem!rane potentialhen it is unstimulated. *+, to*-,milivolts


11/26

Neuronal Conduction

• 9he reception of a signal !y a neuron

of often may change the mem!rane

potential of a neuron resulting in the

generation of an electric current that

is propagated from dendrites to

synaptic !uds of a0ons


12/26

.ormation o$ esting &embranePotential

/ &inor reason: 9he neurolemma consists ofa


13/26

ti & b


14/26

esting &embranePotential

• What stops the !uildup of negative chargeD

• 9he e0cess negative charges inside the cell

e0ert an attractive force that opposes theo of additional positively charged 4 3 ionsout of the cell.

• 9he separation of charge voltage5 thusresults in an electrical gradient thatcounter!alances the chemicalconcentration gradient of 4


15/26

4yperpolarisation5epolarisation

• 4yperpolarisation occurs hen inside themem!rane !ecomes more negative.

• yperpolarisation occurs hen a stimulus

increases the net outo of positive ions orthe ino of negative ions

• epolarisation: the inside of themem!rane FCG5 !ecomes more positive.

• O$ten by the opening o$ gated Na1 channels causing Na1 to di6use into

the cell


16/26

Transesteri7cation

• 9he su!sitution of an R group of anester ith the R group of an alcohol

• Catalysed !y the addition of an acidor !ase

O4* 541


17/26

Transesteri7catio and 8iodieselProduction

• Biodiesel is a fuel made fromvegeta!le oils and alcohols;ethanol = Ethanol = Fso


18/26


19/26

#teps in 8iodieselPreparation


20/26

8iodiesel

• Biodiesel is often !lended ithpetroleum diesel to produce a fuelthat is compati!le ith diesel

engines. Biodiesel !lends reduceharmful emissions.Advantages isadvantages

Biodegrada!le igher fuel price dueuse from e0pensive

feedstoc$

Renea!le energysource thus reducesdependence onpetroleum

&oes not reduce 8emissions

igher ash point


21/26

E!plaining Acidity o$ AlcoholsCarbo!ylic Acids Phenols

• &ecreasing acidity+ C88HPh<8HRI8

• .actors that account $or acidity:#tability o$ conjugate base

$ormed

; resonance(electron delocalisation)induction

conjugation


22/26

#tability o$ Conjugate8ase

• The more stable the conjugate base,the more acidic the organiccompound

• #ta!ility of con?ugate !ase is a@ected!y+

• &elocalisation=&istri!ution of mo!ileelectrons

• Fnduction

• 8r!itals


23/26

Conjugatebase5esonance

• esonance increases sta!ility !y dispersingnegative charge preventing reformation of acid

• Ethanoic acid is stronger acid than phenol

!ecause in the ethanoate ion, the distri!utionof negative charge cloud is distri!uted ordelocalised more evenly than on thepheno0ide ion

•

8n the Pheno0ide ion the negative charge isrepelled !y the !en:ene ring therefore it isdenser around the o0ygen atom


24/26

esonance


25/26

%nductive E6ective

• 9he e@ect on the electron density in oneportion of a molecule due to electron-withdrawing or electron-donating groupselsehere in the molecule..

• Electron*3ithdra3ing groups(electronegative atoms): increaseacidity !y reducing the charge density on

one region of the atom• Electron donating groups decrease

acidity


26/26

Orbitals• 9he more ,s- character the or!ital in

the con?ugate !ase is the closer theelectron is to the nucleus thus themore sta!le it is

neuronal anatomy and action potential

Documents