Medicine Notes Neurology Notes
These notes helped me achieve a mark of 76% in my neurology exam, which is the equivalent of a 1st. The notes are based on a series of 49 lectures on the subject. This is a very good, thorough and in depth review of the nervous system. They are very clearly laid out and easy to follow. They cut out unnecessary information on the topic, making the notes very concise, and fast to get through. Anyone studying medicine, or any other subject requiring knowledge of the nervous system (e.g. physiology o...
The following is a more accessible plain text extract of the PDF sample above, taken from our Neurology Notes. Due to the challenges of extracting text from PDFs, it will have odd formatting:
Lecture 5
Neurons and glia are the building blocks of the brain
Structure of neurons
General
Electrically excitable, use electricity to relay messages
Polarised (dendrites- input; axons- output)
Terminally differentiated (don’t divide- postmitotic)
When neurons die, don’t produce more. Fewer when die than born
Actual CNS neuron: axon length >0.5m
In peripheral nervous system= longer
Structural classes of neurons
Polarity refers to number of processes coming from the cell body (i.e. dendrites and axons)
UNIPOLAR
E.g. Dorsal root ganglion sensory neuron (primary afferent)
BIPOLAR
E.g. Retinal bipolar cell (special senses)
MULTIPOLAR
E.g. Spinal motor neuron
NB. May also be described structurally according to shape (e.g. pyramidal cells, granule cells, stellate cells)
Ionic basis of electrical activity
(Resting) Membrane potential
Neurons maintain (negative inside, ~-70mV) membrane potential at rest
Key determinant of membrane potential
Ionic conc. gradient
Ionic electrical gradient (2 together= electrochemical gradients)
Selective membrane ionic permeability
Key charged ion species
Na; K; Cl; Organic ions (largely protein), A-
Sodium-potassium ATPase establishes electrochemical gradient
3 Na out; 2 K in
Critical for balance of osmotic pressures
ATPase so requires energy (ATP)
Energy efficiency is problem for NS. Human brain (-2% body mass) consumes
15% CO
20% total body oxygen consumption
25% total body glucose utilisation under low physical exertion
In average neuron at rest
Ion Intracellular Extracellular Out/In
Na 15mM 145mM 10
K 155mM 4.5mM 0.03
Ca 0.0001mM 1mM 10000
Cl 5mM 120mM 6
Nernst Equation
Calculates equilibrium or Nernst potential for ion across membrane- no net ion movement
Ex = RT/zF in [X]extracellular/[X]intracellular
R= Universal gas constant (8.314 J per Kelvin per mole)
T= Absolute temp (C + 273.15 K)
Z= Ion charge
F= Faraday’s constant (96485 coulombs per mole)
E= Electrical potential
NB: RT/F (at 37C)= 0.0267 joules/coulomb= 26.7mV
Favourite ion species
Na
(-61.4/1)*log(15/145)= +60mV
K
(-61.4/1)*log(154/4.5)= -94mV
Cl
(-61.4/1)*log(5/120)= -85mV
But resting Em= -60 to -90mV
Potential for each ion are the potentials that would balance the conc. gradient if each was the only ion involved
Membrane potential not close to that of Na as membrane not very permeable to it (more so to K)
Permeability
Controlled by protein ion channels in neuronal plasma membrane
Specific channels for specific ions
State of channels controlled by conformation of constituent proteins
Three major factors that influence movement of ions across cell membrane
Conc. gradient
Voltage gradient
Membrane permeability
Em=RT log Pk[K]o + Pk[Cl]o + PNa[Na]o
zF Pk[K]i + Pk[Cl]i + PNa[Na]i
Neurons as information processors
Changes in RMP
Depolarisation: RMP becomes less negative
Hyperpolarisation: RMP more negative
Permeability changes for an ion when permeability for specific ion increases, RMP will move towards that ions equilibrium potential (K= hyperpolarising; Na= depolarising)
Action potentials
Check notes, basic physiologic principles of APs
Basic properties of AP
THRESHOLD= membrane voltage at which AP initiated
RAPID DEPOLARISATION= explosive depolarising change in potential
OVERSHOOT= magnitude of positive change in membrane potential
ALL-OR-NONE RESPONSE= membrane reaches threshold, stereotypic AP occurs, if threshold not reached, no AP occurs
ABSOLUTE REFRACTORY PERIOD= when 2nd AP cannot be produced
RELATIVE REFRACTORY PERIOD= time when more difficult but not impossible to produce 2nd AP at membrane site
Ionic imbalance leads to pathological excitability changes
Na:E= +61mV; K:E= -95mV
HYPOKALAEMIA= more negative (hyperpolarised) closer to AP threshold (e.g.) muscle trouble
HYPERKALAEMIA= more positive (depolarised) closer to AP threshold hyperexcitability (prolonged...
Buy the full version of these notes or essay plans and more in our Neurology Notes.
These notes helped me achieve a mark of 76% in my neurology exam, which is the equivalent of a 1st. The notes are based on a series of 49 lectures on the subject. This is a very good, thorough and in depth review of the nervous system. They are very clearly laid out and easy to follow. They cut out unnecessary information on the topic, making the notes very concise, and fast to get through. Anyone studying medicine, or any other subject requiring knowledge of the nervous system (e.g. physiology o...
Ask questions 🙋 Get answers 📔 It's simple 👁️👄👁️
Our AI is educated by the highest scoring students across all subjects and schools. Join hundreds of your peers today.
Get Started