Topic 3: APs, Synapses & NTs Flashcards
When a neuron is not firing it is said to be ____
Resting
When a neuron is resting its cell membrane is ____
Polarized
A polarized membrane has an electrical gradient (difference) between the _____ of the cell membrane and the _____
Outside, Inside
The outside contains more ______ because a ‘pump’ pumps ____ out of the cell
Sodium (Na+), Na+
How long does the resting polarized neuron remain polarized ?
Until there is stimulus
The Na+ ion channels on the resting neuron’s membrane open suddenly when the stimulus reaches _____ and allow the Na+ that was on the ______ of the membrane to go rushing in
Threshold, outside
When the stimulus reaches threshold ___ goes in
Na+ ions
What is complete depolarization?
Complete depolarization of the axon results when threshold is reached and the neuron continues to open Na+ channels all along the cells membrane of the axon.
Wave depolarization is also called _____
Nerve impulse or the action potential
When is the neuron back to its normal polarized state?
After an appropriate amount of Na+ is pumped
What is the refractory period?
Refractory period is the time when the neuron is busy returning everything to the normal polarized (resting) state. It usually doesn’t respond to any incoming stimuli.
All axons are sheathed in myelin
False.
Many but not all axons are sheathed in myelin
The movement of ____ conduct APs along neuron cell membrane
Sodium
What is myelin made up of?
Myelin is composed of lipids (fat) and functions like rubber insulation around an electrical wire. It covers the length of the axon except for small nodes about 1mm. apart
What is it called when action potentials jump from Node to node ?
Saltatory Conduction
The speed of conduction along an axon depends on its ____ and whether it is ______
Diameter, myelinated
What is saltatory conduction?
- Saltatory conduction increases nerve conduction velocity w/o having to dramatically increase axon diameter. Without it, conduction velocity would need large increases in axon diameter.
- Saltatory conduction requires much less energy than continuous conduction b/c the sodium ‘pumps’ only need to operate at the nodes of Ranvier and not along the whole axon.
Demyelinating diseases such as _____ are often accompanied by debilitating fatigue.
Multiple Sclerosis
In _______, the impulse is propagated as a ____________ spreading along the axon
Unmyelinated, continuous wave of depolarization
In ______, the impulse ‘jumps’ from node to node, a faster and energy saving process called ________
Myelinated, Saltatory conduction
A typical synapse consists of :
1) Presynaptic neuron
2) Synaptic cleft
3) postsynaptic neuron
The ____ is where an AP is transmitted from one neuron to another neuron
Synapse
There are synapses between _____ and ____ and between ______ and ______
Neurons and muscles (NMJ), neurons and glands
A ______ is a chemical released by a presynaptic neuron
Neurotransmitter. It diffuses across the synaptic cleft to stimulate or inhibit the postsynaptic neuron.
Name the types of synapses:
Axon terminals can connect with :
1) dendrites of another neuron: axodendritic synapse (most common)
2) the cell body of another neuron: axiomatic synapse
3) the axon of another neuron: axoanonal synapse
When an AP reaches presynaptic terminal, vesicles containing neurotransmitters (NT) fuse with the neuron’s membrane and release their contents into the _______
synaptic cleft
______ are required for the fusion to take place
Calcium ions
An EPSP makes it _____ likely that an AP will continue in the postsynaptic neuron.
More likely.
Threshold of the postsynaptic neuron will most likely be reached
An IPSP makes it ____ likely that an action potential will continue on in the post synaptic neuron
less likely.
Poles are further apart
Frequent postsynaptic potentials at the same synapse occur in rapid succession. The effect of the first potential does not have time to dissipate and the succeeding potentials add to the previous ones
Temporal summation
E.g. Mom, mom, mommy .. what?
Multiple excitatory signals to various postsynaptic sites
Spatial summation
What is the All or None Law?
If the sum of all EPSPs and IPSPsr reaches threshold, an AP will result. however, if the neuron does not reach threshold, an AP will not occur. If it fires and the AP goes all the way to the end of the axon it is called All or None Law
The change in the frequency of action potentials usually indicates ________
A change in the intensity of a stimulus
A chemical that is released from the a neuron and transmits a nerve impulse from one neuron to another, muscle or organ or other tissue.
Neurotransmitter
A NT ______ is a chemical that has the same effect on the postsynaptic neuron as the neurotransmitter does
agonist
An ______ is a molecule that blocks the effect of a NT or its agonists
Antagonist
Life-threatening depression of respiratory system is a side effect of _____
opioid overdose.
When administered it allows an overdose victim to breathe normally
Naloxone, aka Narcan
e.x Often taken by musicians
What is the most common inhibitory Neurotransmitter in the CNS
GABA - Gamma-aminobutyric acid
Nerve cells fire often without this
GABA
Low GABA activity is related to
Anxiety disorders, such as panic attacks, seizure disorders and cognitive impairment
Supplement sold and promoted as a natural tranquilizer is ___
Valerian.
GABA taken as a supplement does not cross the BBB and works as a placebo.
Examples of benzodiazepines are
Vallium and Librium
Glutamate is the most common inhibitory neurotransmitter in the CNS
False. It is an excitatory NT
This is involved in cognition, memory and learning
Glutamate
Due to chronic inflammation, microglia can become ___
over activated (sensitized)
____ use glutamate to destroy infected neurons, virus, and bacteria, but this can also cause large amounts of collateral damage to healthy neurons
Microglia (phagocytes of the CNS)
Over activated microglia can result in a self-perpetuating cycle called ______
Reactive microgliosis .
An underlying mechanism of progressive neuron damage across numerous neurodegenerative diseases, regardless of the instigating stimuli.
E.g. NFL players experience this due to concussions
____ deficit is linked to depression
Serotonin.
a class of drugs that alleviate depression by increasing the length of time that serotonin stays in the synapse.
Selective Serotonin re-uptake inhibitors (SSRI)
Makes it more likely to bind to postsynaptic receptors.
One well-known SSRI is _____
Prozac.
An excess of dopamine in the limbic system and not enough in the cortex has been linked to ______
Paranoia and addiction (this is why addiction is a disease)
An excess of dopamine in the frontal lobe _____
relieves pain and boosts feelings of pleasure
Memory problems, Mov’t problems such as parkinson’s are a cause of _____
Shortage of dopamine
Dopamine agonist drugs are linked to _____
Pathologic gambling, compulsive shopping, her impulse control disorders
____ is secreted from the hypophysis. It is a hormone that also acts as a neurotransmitter in the brain
Oxytocin
Oxytocin is thought to be released during ____
Hugging, touching and orgasm in both sexes.
Two ways in which drugs modify synapse function
- Mimic the neurotransmitter (agonist)
e. g morphine mimics endorphins in pain pathways - Block re-uptake of neurotransmitter (antagonist)
- Cocaine blocks the reuptake of dopamine
- Prozac is a serotonin reuptake inhibitor - Block enzyme pathways that degrade neurotransmitters
- several anti-depressants block an enzyme that degrades serotonin, dopamine, epinephrine, and norepinephrine
“PANS”
The neurotransmitter released at the postganglionic synapses is _________
Acetylcholine (Ach)
Axons that release ACh are called ______
Cholinergic fibres
Aka for cholinergic drugs
Parasympathomimetic drugs : because they produce effects that imitate parasympathetic nerve stimulation
“SYNS”
The neurotransmitter released at the postganglionic synapses is _________
Norepinephrine aka noradrenalin
Fibres that release norepinephrine are called _____
adrenergic fibres
aka for adrenergic fibres
Sympathomimetic drugs: because they mimic effects similar to those produced by the sympathetic nervous system
_____ drugs increase BP and HR and are useful in treating systemic trauma, including shock, and cardiac arrest
Adrenergic drugs
Drugs that block or inhibit the release activity of NE known as
adrenergic blocking agents
Aka for beta-adrenergic blocking agent
Beta-blocker : reduces symptoms connected with HT, cardiac arrhythmias and angina pectoris
Why must people who take beta-blockers avoid caffeine, alcohol, and salty foods?
because the interaction of those substances and the drug can raise the heart rate and blood pressure
