Neurons Flashcards
What is the morphological division?
CNS and PNS
What is cephalisation?
the formation of central ganglia and brains in one end of the animal body
What is the dorsal chord?
in the vertebrate line of the animal kingdom
What is the ventral chord?
In the invertebrate line
What are the main functions of the nervous system?
TO monitor and regulate inner organs, release chemical messengers
Is the neural membrane polarised?
yes
Where are ion channels distributed?
along the neural membrane
Ion’s distribution and properties enable the neruon to…
generate tiny localised bioelectric currents.
What do all neurons have?
Input zone,
integration zone,
conduction zone,
output zone
What is the input zone?
soma, dendrites
What is the integration zone?
between soma and axon
what is the conduction zone?
axon
what is the output zone?
axon terminals
Neuronal membrane is selectively what?
permeable
Most channels are made from ___ proteins that assemble themselves to produce a central _____
4
pore
Ion channels have a selectivity filter that only allows…
ions of a particular charge and size to pass through
What does the semi-permeable membrane allow
diffusion whilst the passage is open. When ion channels in the neural membrane open, ions can diffuse.
When ion channels are closed, ions can diffuse inside the cell and along the membrane but not beyond the membrane and out of the cell.
Ion distribution differs inside and outside of the cell which forms an
electrochemical gradient
What are the three classes of ion channels
Gated ion channels, ion pumps, lead channels
What do gated ion channels do?
remain closed until activation for a very brief period of time, either by electrical signals (voltage-gated) or by drugs or messenger molecules (ligand-gated).
What are voltage-gated?
electrical signals
What are ligand-gated
messenger molecules
WHat do ion pumps do?
actively transport ions in and out of the neuron
What do leak channels allow
a specific ion type to freely diffuse (e.g. they are always open and let K+ through but not Na+)
What do ion pumps help do?
restore and maintain the difference in ion concentrations inside and outside the neuron
What are the most importatn pumps in ion pumps
Sodium-potassium and calcium
What is intracellular recordings?
Microelectrodes are placed inside
What are extracellular recordings?
Microelectrodes are placed outside
How do we measure neural currents?
Voltage (V) – difference in potential, measured in volts
Strength of current (I) – electrostatic force moving charge per second, measured in amperes
Resistance (R) – difficulty of passing a current along a conductor
Multimeter – instrument to measure voltage, current, resistance
What is Ohm’s law?
V = I x R
How thick are squids axons
1mm
How much bigger are squids axons than mammalian?
100-1000x bigger
What is resting potential?
Membrane potential of a nerve cell at rest
What is neural signal?
Change of resting potentail to more negative or positive potntial
WHat is hyperpolarisation?
a more negative membrane potential than the resting potential
What is depolarisation?
a more positive membrane potential than the resting potential
where do graded potentials occur?
in dendrites
What is action potential (spike)
- An all-or-nothing response when the depolarisation increases above a neuron-specific threshold
(action potentials never occur during hyperpolarisation)
