C2.2 Neural Signalling Flashcards
What is the function of the sodium-potassium pump?
Restores the resting membrane potential by exchanging three Na+ ions for two K+ ions
The sodium-potassium pump uses energy to maintain ion concentration gradients.
What ensures that action potentials can only go in one direction?
The refractory period, during which sodium channels are closed => neuron is unresponsive
This prevents backflow of action potentials.
What happens when an action potential reaches the synapse?
Voltage-gated calcium channels open, allowing calcium ions to flow into the cell
This triggers the release of neurotransmitters.
Define saltatory conduction.
impulse jumps from node to node in myelinated cells
This is facilitated by the myelin sheath.
What is the resting membrane potential of a neuron?
-70mV
It indicates the polarized state of the neuron when not conducting an impulse.
Fill in the blank: Action potentials are ______.
all or nothing
This means that once the threshold is reached, the action potential will occur with the same magnitude.
What is the role of excitatory postsynaptic potentials (EPSPs)?
They make an action potential more likely by causing depolarization
EPSPs result from the opening of ion channels allowing Na+ influx.
What are the two types of fibers involved in transmitting impulses related to pain?
Afferent nerve fibers and efferent fibers
Afferent fibers transmit impulses toward the brain, while efferent fibers transmit impulses from the brain.
What affcets speed of nerve impulse transmission
- myelination = faster in myelinated
- diameter of neuron => faster in large diameter
- temperature = faster in high temp
Myelination increases the speed of impulses by saltatory conduction.
What occurs during repolarization of a neuron?
K+ ions rush out of the cell, => becomes more negative inside
This happens after the peak potential is reached.
What is the function of neurotransmitters at synapses?
They transmit signals across the synapse to the postsynaptic neuron
This occurs via exocytosis into the synaptic cleft.
What is the peak potential during an action potential?
+40mV
This is the maximum membrane potential reached during depolarization.
What are the types of receptors found in the skin for pain perception?
Thermoreceptors
Meissner’s corpuscles= light vibrations & touch
nociceptors = pain
Pacinian corpuscles= skin stretch and pressure
Ruffini endings & free nerve endings
Each receptor type is responsible for different sensory information.
What is the difference between presynaptic and postsynaptic neurons?
Presynaptic neuron carries impulse towards a synapse
postsynaptic neuron carries impulse away from a synapse
Presynaptic neurons are the ‘sender’ and postsynaptic neurons are the ‘receiver’.
What is the role of calcium ions in synaptic transmission?
They cause synaptic vesicles to fuse with the membrane, releasing neurotransmitters
This process is essential for communication between neurons.
neonicotinoid ?
- blcoks synaptic transmission by binding to acetylcholine receptor in CNS of insects = die
- Reduction in honeybee and bird populations
This is due to the loss of insects as a food source and has led to restrictions in some countries.
What is the function of Schwann cells?
They form the myelin sheath around axons, providing insulation
This insulation is crucial for increasing the speed of nerve impulses.
What are companion cells?
Cells that wrap their cell membrane around the axon many times.
They form a thick insulating lipid layer called the myelin sheath.
What is a neuromuscular junction?
A specialized synapse between a motor neuron and a muscle fibre.
What neurotransmitter is released by motor neurons at the neuromuscular junction?
Acetylcholine.
What initiates muscle contraction at the neuromuscular junction?
Binding of acetylcholine to receptors on the plasma membrane of the muscle fibre, leading to depolarization.
What results from neonicotinoid pesticides binding to acetylcholine receptors?
Permanent overstimulation of target cells, leading to fatal convulsions and paralysis.
What are the two types of postsynaptic potentials?
- EPSP (excitatory postsynaptic potentials)
- IPSP (inhibitory postsynaptic potentials)
What is summation?
Additive effect of inhibitory and exciutatory stimuli received from multiple postsynaptic neurons
Where is conscious awareness primarily associated?
The cerebral cortex of the brain. = cerebrum
What is the resting potential?
The voltage across the membrane when a neuron is not firing.
What drives the generation of resting potential in neurons?
Pumping of sodium and potassium ions by ATP-driven ion pumps.
What are the three types of neurons?
- Sensory neurons
- Motor neurons
- Relay neurons
What is the difference between myelinated and unmyelinated neurons?
Myelinated neurons have action potentials that ‘hop’ between nodes of Ranvier, increasing conduction speed.
What happens at an excitatory synapse?
It depolarizes the local membrane potential of the postsynaptic cell.
What happens at an inhibitory synapse?
It hyperpolarizes the local membrane potential of the postsynaptic cell.
What does cocaine do to neurotransmitter levels?
It blocks the dopamine transporter, elevating extracellular dopamine levels. => sends amplyfied signal
What is the threshold potential for generating an action potential?
Approximately -50mV.
What triggers an action potential in a neuron?
A stimulus causes the opening of some sodium channels, raising the membrane potential to threshold (-50mV).
What happens during the depolarization phase of an action potential?
Na+ voltage-gated channels open, flooding the cell with Na+, causing the membrane potential to become less negative.
What are the four main structural regions of a neuron?
- Network of dendrites
- Cell body
- Axon
- Axon terminal (synaptic) knobs
What occurs during the repolarization phase of an action potential?
Potassium ions exit the neuron, causing the membrane potential to fall back to a negative value.
What are the four key stages of an action potential?
- Resting potential
- Depolarization
- Repolarization
- Refractory period
What is the significance of the oscilloscopes in studying neurons?
They measure the membrane potential and display it as a graph.
saltatory conduction
skipping motion of action pot. from node to node in myelinated axon
Depolarisation & repolarisation steps
- Na channel opens & Na influx
- resting pot -70 -> -50 treshold
- volatge gated Na+ channel opens at treshold
- Na+ diffuse inside => triggers axon Na+ channel to open = saltatory conduction
- -50 -> +40 mv
- voltage gated K+ opens and K+ flow out => decrease
- Na+K+ pump reestablishes resting pot
Propagation
is unidirectional due to refractory period where some sections of nodes cant egenrate action pot.
how pain works
- stimuli on skin/receptor cells
- influx of positive ions
- action potential triggered
action potential steps
- resting ststae -70 mv
- depolarisation -55 treshold
- rising phase = na in
- falling phase = k out
- resting phase & hyperpolarisation = K out and CL in
- resting potential because of k+Na+ pump
- refractory period
Acetylcholine
- binds at synaptic cleft => opens membrane = NT goes in
- made in axon etrminal by acetyl-coa + choline
- stored in vesicles
- broken down by acetylcholinesterase
- choline goes back in axon terminal to regenerate
neuronal synapses
brtween 2 neurons
neuroglandular synpase
neuron & gland (ex: hypothalamus)
synaptic cleft
space between end of neuron and target cell into which Nt diffuse
synapse
junction between two nerve cells consisting of a gap across impulses pass by diffusion
Neurotransmitter steps
- action pot. travels down axon terminal of presynaptic neuron
- volatge gated calcium channel open = ca2+ flow in
- exocytosis induced = fuse with presynaptic membrane = release NT
- NT diffuse through cleft = bind to receptors in postsynaptic cleft
temporal summation
one or more presynaptic neurons transmit impulses in rapid fire order
multiple at same location
spatial summation
postsynaptic neuron stimulated by large number of terminals at the same time
at different locations
how does Neonicotinoid work
binds irreversibly to acetylcholine receptors at cholinergic synapses so that acetylcholine is unable to bind => no action potential
how does sodium potassium pump make resting potential
sodium out, potasiium in
