Physiology - Introduction to the Nervous System Flashcards
what is the role of the dendrites?
receives inputs from other neurones and convey signals to the soma
what is the role of the cell body of a neurone?
it is the synthetic and metabolic centre of the neurone
integrates incoming electrical signals and conducts them to the axon
what happens at the axon hillock?
it is the site of initiation of the action potential
what is the role of the axon?
conducts output signals as action potentials to the presynaptic terminal
what is anterograde transport?
along an axon from the soma to the presynaptic terminal
what is retrograde transport?
along an axon from the presynaptic terminal to the soma
what is another name for the neurone cell body?
the soma
what is a synapse?
a point of chemical communication between neurones or other cells
what can viruses exploit to infect neurones?
the retrograde transport system
what are the three components that make up a synapse?
presynaptic terminal
synaptic cleft
postsynaptic membrane
what is another name for the processes arising from the soma?
neurites
describe a unipolar neurone
one neurite
describe a pseudo-unipolar neurone
one neurite that bifurcates
describe a bipolar neurone
two neurites
describe a multipolar neurone
three or more neurites
what are the four functional regions found in most neurones?
input
integrative
conductive
output
what happens to the electrical signal in an action potential as it is conducted over a large distance?
they do not decay but stay constant
what happens to passive signals as they pass from their site of initiation and why?
they diminish
the nerve cell membrane is leaky meaning current is lost
what is the length constant (λ)?
the distance that the current can travel before it diminishes to zero
what two factors does the length constant depend on?
membrane resistance (rm) axial resistance (ri)
what is membrane resistance (rm)?
the membranes ability to resists leakage of current
should be high
what is axial resistance (ri)?
the impedance of the current inside the axon
should be low
how can the length constant be increased?
increase the ratio of membrane resistance/axial resistance
what impact does increasing length constant have on AP conduction velocity?
increases local current spread which increases AP conduction velocity
how can you increase passive current spread in an axon?
either decrease axial resistance or increase membrane resistance
how can you decrease axial resistance?
increase axon diameter
how can you increase membrane resistance?
myelination
what cells are responsible for myelination?
Schwann cells in the PNS
oligodendrocytes in the CNS
what cell type are Schwann cells and oligodendrocytes?
macroglia
describe the presence of Schwann cells around axons
many Schwann cells surround one axon
describe the presence of oligodendrocytes around axons
one oligodendrocyte surrounds many axons
is conduction faster in a myelinated or non-myelinated axon?
myelinated
what is saltatory conduction?
when the AP jumps from one node of ranvier to the next
in which axons does saltatory conduction occur in?
myelinated axons
what effect do demyelinating disorders have on conduction?
slow down nerve conduction speed
name two demyelinating disorders
MS
Guillain Barre syndrome
what separates the pre and post synaptic membranes?
synaptic cleft
what is found in the synaptic cleft and what does it do?
a matrix of fibrous extracellular protein
holds the membranes together
where are neurotransmitters stored?
within vesicles in the presynaptic terminal
what feature is found in the presynaptic membrane?
active zones where vesicles cluster
what feature is found in the postsynaptic membrane?
the postsynaptic density containing neurotransmitter receptors
what are the three types of synapses classified by the location of the presynaptic terminal on the postsynaptic cell?
axodendritic
axosomatic
axoaxonic
what is an axodendritic synapse?
axon meets the dendrites
what is an axosomatic synapse?
axon meets the soma
what is an axoaxonic synapse?
axon meets the axon
what are the two functional types of synapse?
excitatory
inhibitory
what is the transmitter for excitatory synapses in the CNS?
glutamate
what postsynaptic receptors does glutamate bind to?
cation selective glutamate receptors
what does glutamate binding cause?
the excitatory postsynaptic potential (epsp)
what are the transmitters for inhibitory synapses in the CNS?
GABA or glycine
what postsynaptic receptors does GABA/glycine bind to?
anion selective GABA/glycine receptors
what effect does GABA/glycine binding have?
inhibitory post synaptic potential (ipsp)
what ion channels are opened in response to the epsp?
positive sodium channels
causes a depolarisation
what ion channels are opened in response to the ipsp?
negative chloride channels
causes a hyperpolarisation
what are the three main classes of neurotransmitters?
amino acids
amines
peptides
name an amino acid neurotransmitter and where they are released from?
glutamate
synaptic vesicles
name an amine neurotransmitter and where they are released from?
noradrenaline
synaptic vesicles
name a peptide neurotransmitter and where they are released from?
CCK
secretory vesicles
how does a neurotransmitter work directly on an ion channel?
via ionotropic receptors
describe an ionotropic receptor
the receptor is an integral part of the channel
which is causes faster gating - ionotropic or metabotropic receptors?
ionotropic
how does a neurotransmitter work indirectly on an ion channel?
via metabotropic receptors
describe a metabotropic receptor
the receptor and the channel it controls are two separate, distinct components
