Neurons, Synapses and Signaling Flashcards
What does the CNS consist of? PNS?
CNS: brain and spinal cord
PNS: Cranial nerves, spinal nerves, and ganglia that originate outside the CNS
Where are action potentials created? Where are neurotransmitters released?
Axon hillock
Axon terminal
Look at this picture and have an understanding of the structures of neurons.
:)
What are the 3 stages of information processing of the nervous system?
- Sensory input (PNS)
- Integration (CNS)
- Motor output (PNS)
Describe the function of sensory neurons, interneurons, and motor neurons.
Sensory neurons - Sensors detect stimuli (internal or external) and transmit impulse along these towards CNS
Interneuron - these are in the brain and receives input from sensory neurons and integrate the information.
Motor neuron - motor output leaves brain through these and triggers muscle or gland activity.
Is the inside of a neurons charge a net positive or negative?
Negative
What is the difference in voltage across the membrane called?
Membrane potential
What does the membrane potential have to do with message transmitting?
Messages are transmitted as changes in membrane potential.
What is the resting potential of a neuron? (membrane potential of neuron not sending signals)
between -60 to -80 mV
What are the two ions whose concentrations primarily determine the resting potential? How are these gradients maintained? Does this require energy?
K+ and Na+
sodium/potassium pumps control this gradient, ATP is required to run these.
Are there also ion channels that allow for Na and K to feely move across the membrane? What quantity of each of these are open in a resting cell?
YES
Generally in a resting neuron has MANY open K+ channels and a FEW open Na levels.
What is importnat to the formation of the membrane potential? Why?
The diffusion of K+ out of the cell
As K+ diffuses out of the cell the anions within the cell contribute to the negative charge inside.
What is the purpose of gated ion channels?
These open or close in response to stimuli to change the membrane potential.
What is the difference between hyperpolarization and depolarization?
Hyper - increase in magnitude of the membrane potential, making the inside of the membrane MORE NEGATIVE.
Depolarization - A reduction in the magnitude of the membrane potential, making it LESS NEGATIVE.
What are graded potentials?
These are changes in the polarization where the magnitude of change varies with the strength of the stimulus.
What channels open during depolarization?
voltage gated Na+ channels open and Na+ flows in which results in further depolarization, which leads to further Na+ channels to open and more Na+ to flow in,
Eventually the change is massive enough to trigger an action potential.
What must the membrane voltage cross before an AP occurs?
The THRESHOLD, usually -55 in mammalian neurons.
Once an AP is triggered, does the strength of the contributing stimulus have any effect on the magnitude of the AP?
What is this called?
NO
The all-or-none response
What is the definition of an AP?
Signals that carry information along axons.
What are the 5 stages of an action potential?
- Resting
- Depolarization
- Further depolarization
- Repolarization
- Hyperpolarization
What gives the graphing of an AP its shape?
The movement of ions through their voltage-gated channels
Can a neuron perform many APs per second?
YES
What is the refractory period?
This is the period after an AP in which a second AP cant be initiated.
This is caused by temporary inactivation of Na+ channels
How does an AP travel along the axon?
The neighboring region is depolarized, and the AP cant travel backwards due to the refractory period of the portion of the axon behind it, only allowing the AP to travel in one direction.
WHICH IS TOWARDS THE SYNAPTIC TERMINALS
What increases the speed of conduction of the AP down the axon? What types of glia makes the myelin sheath in the CNS and the PNS?
MYELIN SHEATH
CNS - oligodendrocytes
PNS - Schwann cells
Velocity increased:
- Increase in axon diameter
- INSULATION (MYELIN SHEATH)
Where is the only place in myelinated axons that APs can form? Meaning where are the voltage-gated channels located?
NODES OF RANVIER, gaps in the myelin sheath
What is saltitory conduction?
THis is how APs jump between gaps at the nodes of ranvier in myelinated axons
What is an electrical synapse and a chemical synapse? Frequency?
Electrical - electrical current flows from one neuron to another, FEW OF THESE.
Chemical - neurotransmitter carries information across the synaptic cleft. MOST SYNAPSES ARE THESE.
How does the presynaptic neuron package neurotransmitters for the postsynaptic neuro to recieve them?
What does the AP do?
Via synaptic vesicle located at the synaptic terminal
The AP signals the release of the neurotransmitter that diffuses accross the synaptic cleft to the postsynaptic cell.
What are the two types of postsynaptic potentials that exists?
Excitatory - these are depolarizations that bring the membrane potential towards the threshold
Inhibitory - hyperpolarizations that bring the membrane potential further from the threshold
Is a single excitatory postsynaptic potential (EPSP) usually enough to trigger an action potential?
NO
What is temporal summation?
This is when two ESPS are produced in rapid succession and they are added together to reaching the threshold potential.
THIS OCCURS ON THE SAME SYNAPSE
What is spatial summation?
This is when ESPS are produced almost simultaneously by DIFFERENT SYNAPSES of the same postsynaptic neuron.
These are added together
Can summation be used by both ISPS and ESPS? How is it determined whether or not an action potential is triggered?
YES
The summation effect of both the ESPS and ISPS must be taken into account to see whether an AP is triggered
What the 5 different types of neurotransmitters? Does the same neurotransmitter always produce the same effect in any cell it effects?
- acetycholine
- amino acids
- biogenic amines
- neuropeptides
- gases
NO, the same neurotransmitter may have different effects on different cells.
What are two ways that neurotransmitters can be terminated?
- enzymatic breakdown
- reuptake
What is the function of acetylcholine? What inhibits this neurotransmitter?
muscle contraction or relaxation at neruomuscular junctions, memory formation, and learning
Acetylcholinesterase is an enzyme that breaks down acetylcholine
What does serin gas and botulinium toxin cause?
serin gas - inhibits acetylcholinesterase so it builds up and causes contractive paralysis
botulinum toxin - prevents acetylcholine release and leads to flaccid paralysis including failure of respiratory muscles to contract.
What two amino acids are major neurotransmitters?
glutamate - long-term memory
GABA (gamma-aminobutryic acid) - stimulates IPSP
What are 4 biogenic amines that function as neurotransmitters? where are they active? roles of dopamine and serotonin?
epinephrine, norepinephrine, dopamine, serotonin
Both CNS and PNS
Both play a role in sleep, mood, and learning
What receptors do LSD and mescaline act on to cause hallucinations?
they bind to dopamine and serotonin receptors and activate them
What are some examples of neuropeptides? What do they affect? What drugs can act on these receptors?
substance P and endorphins
Affect our perception of pain
Opiates bind to the same receptors as endorphins
What are two gases that act as neurotransmitters? What do they locally regulate?
NO and CO
Locally regulate the PNS
