nerves and synapses Flashcards
what are the inhibitory neurotransmitters?
GABA; glycine
what are the excitatory neurotransmitters?
glutamate, aspartate
what are the chemical synapses that release actylcholine called?
cholinergic synapses
what are the types of cholinergic receptors?
muscarinic, nicotinic
what happens at the sodium-potassium exchange pump?
the sodium-potassium exchange pump maintains the cell’s resting potential by ejecting three sodium ions for every two potassium ions it brings in from the ISF
(3 Na+ out; 2 K+ in)
what effect would a chemical that blocks the voltage-gated sodium channels in the plasma membrane of a neutron have on its ability to depolarise?
if the voltage-gated sodium channels couldn’t open, sodium ions could not flood into the neutron and it would not be able to depolarise
describe four features of a polarised neuron
resting membrane potential
-70 volts
more K+ inside
more Na+ outside
what is dopamine and what does it act on?
what is its effect?
neurotransmitter
dopaminergic receptors
can be excitatory or inhibitory
what physiology does acetylcholine play a role in?
cognition
learning and memory
consciousness
motor control
what is glutamate and what does it act on?
main NT in brain
NMDA receptor
what physiology does noradrenaline play a role in?
arousal and mood
blood pressure
what are the monoamine NTs?
noradrenaline adrenaline dopamine 5HT histamine (excitatory)
define nerve
bundle of nerve fibres
what is the main neurotransmitter?
glutamate
name the structural components of a typical neuron
the cell body, the dendrites and the axon
compare presynaptic and postsynaptic cells
a presynaptic cell is usually a neuron
a postsynaptic cell can be a neuron or another type of cell such as a skeletal muscle fibre or gland
what are the functional classifications of neurons? what are the functions of each type?
sensory neurons transmit impulses from peripheral receptors to CNS
motor neurons transmit impulses (commands) from CNS to peripheral effectors
interneurons analyse sensory inputs and coordinate motor outputs
what is a ganglion?
a collection of neuron cell bodies in the PNS
it’s a little bulge, it’s where the synapses are
what are the three types of sensory receptors?
interoceptors
proprioceptors
exteroceptors
describe the difference between an action potential and a graded potential
action potentials are changes in the transmembrane potential that propagate along the membrane
graded potentials are changes in the transmembrane potential that cannot spread far from the initial site
define membrane potential
the unequal charge distribution between the inner and outer surfaces of the plasma membrane
what is another name for a graded potential?
a local potential
what is the simplest form of information processing in the nervous system?
the integration of stimuli by an individual cell
what is the resting membrane potential?
the resting membrane potential is the membrane potential of a normal, unstimulated cell
what units are the electrical potential measured in?
volts (mV for cells) (millivolts)
what happens at the sodium-potassium exchange pump?
three sodium out/ two potassium in to maintain a stable resting membrane potential
what is the resting membrane potential of a neuron?
-70 mV
what effect would decreasing the concentration of extracellular potassium ions have on the resting membrane potential of a neuron?
it would cause more potassium to leave the cell via leak channels, making the transmembrane potential of the nerve more negative
list the three types of gated ion channels found in neurons
chemically gated ion channels
voltage gated ion channels
mechanically gated ion channels
under what conditions do each of the gated ion channels found in neurons work?
chemically gated channels operate when they bind to specific chemicals eg ACh receptors at the neuromuscular junction
voltage-gated channels open or close in response to changes in the membrane potential
mechanically gate channels operate in response to mechanical stimuli that physically distort the neuron’s membrane surface - important in many sensory receptors
define gated ion channels
active channels in the plasma membrane that open or close in response to specific stimuli
define graded potential
a change in the membrane potential that cannot spread far from the site of stimulation
what kinds of channels do resting membrane potential, graded potential and action potential depend on?
resting membrane potential depends on leak channels
graded potential depends on chemically gated ion channels
action potential depends on voltage-gated ion channels
describe the all-or-none principle in membrane potential
a given stimulus triggers either a typical action potential or no action potential at all - action potentials are always identical
what factor accounts for the local currents associated with action potentials?
movement of sodium ions parallel to the inner and outer surfaces of the plasma membrane when chemically gated sodium channels have opened
are the positive ions on the inside or outside of the cell at resting potential?
Negative on the iNside
pOsitive on the Outside
do potassium ions freely diffuse out of the neural cell?
no
they pass through leak channels or are transported via the sodium-potassium pump (Na/K pump)
which positively charged ions are found more on the outside of a neuron at rest?
sodium
which positively charged ions are found more on the inside of a neural cell when it’s at rest?
potassium
do sodium ions freely diffuse into the neural cell?
no
via leak channels and the sodium/potassium pump
what makes a neuron negatively charged compared to the ECF?
negatively charged proteins on the inside
the sodium/potassium pump helps to maintain the balance
what is the threshold for an action potential?
-55 mV
define repolarisation
the return of the transmembrane potential to the resting potential after the cell has been depolarised
name the types of cells that are capable of producing action potentials
excitable cells
- neurons
- muscle cells
(only in the axons of neurons)
define what is meant by depolarisation
a shift from the resting membrane potential towards a more positive potential
list the events involved in the generation and propagation of an action potential
- depolarisation to threshold
- activation of sodium channels and rapid depolarisation
- inactivation on sodium channels and activation of potassium channels
- closing of potassium channels
compare the absolute refactory period with the relative refractory period
the refractory period is the time between the initiation of an action potential and the restoration of the normal resting potential
absolute refractory period: the membrane cannot respond to further stimulation, no matter how strong
relative refractory period: membrane can only respond to larger-than-normal stimulus
define continuous propagation and saltatory propagation
continuous propagation happens along an unmyelinated axon; action potential affects every portion of membrane surface
saltatory propagation: relatively rapid propagation between successive nodes of a myelinated axon
what’s the relationship between myelin and the propagation speed of action potentials
myelin greatly increases propagation speed
what is a synapse?
a specialised site where the neuron communicates with another cell
describe the components of a synapse
presynaptic cell
postsynaptic cell
neurotransmitters
synaptic cleft
what are the chemical messengers released at the synapse called?
neurotransmitters
but penguin professor refers to them as neurocrines (any chemical secreted by a neuron); the term neurocrines includes NTs but also neurohormones and amino acids
what is the stimulus for the exocytosis of a neurotransmitter into the synaptic cleft?
an influx of calcium ions into the presynaptic nob
contrast an electrical synapse with a chemical synapse
in a chemical synapse, a neurotransmitter crosses the synaptic cleft
electrical synapse: membranes of pre and postsynaptic cells are joined together by gap junctions
define excitatory postsynaptic potential and inhibitory postsynaptic potential
EPSP - graded depolarisation of a postsynaptic membrane by a NT released by a presynaptic cell
IPSP - graded hyperpolarisation of a postsynaptic membrane after the arrival of a NT
define hyperpolarisation
a shift from the resting potential in which the transmembrane potential becomes more negative
neuron can only respond to extra strong stimulus
what is the term for the point in an action potential when the membrane is at its most depolarised? what is its voltage then?
peak action potential
+30 mV
what happens during the hyperpolarisation stage of an action potential?
transmembrane potential drops below -70 mV because potassium channels are slow to close
neuron can only respond to extra strong stimulus
what happens during repolarisation?
why does membrane potential change?
move back towards resting membrane potential
sodium channels are inactivated
potassium channels are activated.
what physiology does dopamine play a role in?
motor control
emotion and reward
decreased prolactin
vomiting
what pathophysiology does dopamine play a role in?
schizophrenia
parkinsons
addiction
what physiology does serotonin play a role in?
(there are lots of serotonin (5HT) receptors):
digestion sleep/wake mood appetite vomiting
what pathophysiology does serotonin play a role in?
(there are lots of serotonin (5HT) receptors):
depression
mania
eating disorders
what physiology does glutamate play a role in?
learning and memory
what pathophysiology does glutamate play a role in?
epilepsy
chronic pain
drug dependence
what pathophysiology does acetylcholine play a role in?
alzheimers
what pathophysiology does noradrenaline play a role in?
bipolar disorder
depression
