Lecture 11.6-11.10 Flashcards
Action potential (AP)
a wave of electrical activity traveling down a nerve or muscle fiber, allowing the body to communicate
Nerve impulse
AP in neuron,
Generating an AP
Resting state
Depolarization
Repolarization
Hyperpolarization
Resting state
inside of the neuron is more negative compared to the outside
Voltage-gated Na⁺ (sodium) and K⁺ (potassium) channels are closed
neuron is polarized
polarized
there’s a voltage difference across the membrane.
Depolarization
neuron gets a strong enough signal
voltage-gated Na⁺ channels open
allows Na⁺ ions to rush into the neuron
the inside of the neuron becomes more positive and the membrane potential becomes less negative, eventually becoming positive.
Repolarization
Na⁺ channels close
voltage-gated K⁺ channels open
As K⁺ leaves, the inside of the neuron becomes negative again, returning toward the resting membrane potential.
Hyperpolarization
some of the K⁺ channels remain open a bit longer, causing the inside of the neuron to become even more negative than the resting potential
Na⁺ channels reset
neuron eventually returns to its resting state
threshold
minimum level of stimulation needed to trigger an action potential
all or none phenomenon
If the stimulus is strong enough to reach the threshold, the neuron fires a complete action potential. If it’s too weak, the neuron does nothing
Synapse
junction that mediates information transfer from one neuron to the next
Electrical synapses
Provide a simple means of synching the activity of all the connected neurons
connect the cytoplasm of closeby neurons
allow neurons to move from one neuron to the next, they are electrically coupled
More abundant in embryonic tissue
Chemical synapses
Allow release and reception of chemical messengers aka neurotransmitters
To transport impulses, it must be done through chemical event that depends on release
2 parts of Chemical synapses
Axon terminal: holds sacs called synaptic vesicles,
Receptor region: a neurotransmitter
Synaptic delay
amount of time it takes for a signal to travel from one neuron to another across a synapse
Excitatory synapses
makes the next neuron more likely to fire an action potential.
Excitatory synapses process
AP reaches excitatory synapse
neurotransmitters are released and bind to the receptors of the other neuron
Na+ ions flow into the neuron, making it more +
Neuron is now closer to threshold to trigger the next AP
ESPS
a small, temporary change in the membrane potential that makes the neuron more likely to fire
Inhibitory synapses
Reduces ability to generate AP
neurotransmitters bind to receptors on the receiving neuron, causing chloride (Cl-) ions to flow into the neuron, or potassium (K+) ions to flow out.
makes the inside of the neuron more negative
pushes the neuron further away from the threshold needed to trigger an AP
ISPS
a small, temporary change in the membrane potential that makes the neuron less likely to fire
Neurotransmitters
means by which neurons communicate, integrate, and send messages to the rest of the body.
Acetylcholine
released by all neurons
Released by presynaptic terminal → binds to postsynaptic receptors → released and degraded to acetic acid and choline by acetylcholinesterase → presynaptic terminals recapture the released choline and reuse it to synthesize more ACh
Biogenic Amines
Catecholamines → dopamine, norepinephrine, epinephrine
Indolamines → serotonin and histamine
broadly distributed in the brain
Amino Acids
glutamate, aspartate, glycine, and gamma aminobutyric acid (GABA).
Peptides
Neuropeptides: strings of amino acids
Substance P: important mediator of pain signals
Endorphins: beta endorphin, dynorphin, and enkephalins, act as natural opiates, reducing the perception of pain under stressful conditions
Gut-brain peptides: widespread in the gastrointestinal tract
Purines
Nitrogen containing base that makes up DNA and RNA
ATP is recognized as a major neurotransmitter in both the CNS and PNS
ATP mediates Ca2+ influx upon binding to receptors on astrocytes
Adenosine is a potent inhibitor in the brain
Gastotransmitters
Include: nitric oxide, carbon monoxide, and hydrogen sulfide
Synthesized on demand and diffuse out of the cells that make them
Endocannabinoids
tetrahydrocannabinol (THC), active ingredient in marijuana
