Exam 2 Flashcards
What are the terms in reference to membrane potential?
Polarization, depolarization, hyperpolarization
What is the membrane potential of a neuron at rest?
-70Mv the inside of the cell being more negative
What’s the difference between polarization, depolarization, and hyperlarization? (Membrane potential)
Polarization- membrane potential is negative (inside of neuron is more negative than outside of neuron)
Depolarization- making the membrane potential less negative, more likely to fire
Hyperpolarization- making the membrane potential more negative, less likely to fire
What are the factors contributing to even distribution of ions when neuron is at rest (encouraging Na+ to move into neuron and make the inside less negative)?
Random motion: particles tend to move down their concentration gradient
Electrostatic pressure: like repels like; opposites attract
What are the factors that factors contributing to uneven distribution of ions during when neuron is at rest?
Selective permeability to certain ions
Sodium- potassium pumps
Describe distribution of Na+ and K+ ions when neuron is at rest
There are more Na+ ions outside the cell than inside, and more K+ ions inside than outside. (Page 79)
What is the function of the sodium-potassium pump?
Use ATP force that exchanges 3 Na+ inside for 2k+ outside
Describe the difference between EPSPs and IPSPs
EPSP- more likely to fire, postsynaptic depolarization, making the membrane potential less negative.
IPSP- less likely to fire, postsynaptic hyperpolarization, making the membrane potential more negative
Describe the differences between postsynaptic potentials and action potentials
EPSP/IPSP= graded, decremental, fast
Action potential= all or none response, non decremental, when the threshold is reached
In order to generate an action potential, the ______ must be reached in the ______
Threshold of activation, axon initial segment
Describe the change in Na+ and K+ distribution that occurs during an action potential
1) voltage-activated Na+ channels open causing depolarization (less negative)
2) voltage-activated K+ channels open (rising phase)
3) Na+ channels close causing polarization
4) K+ channels close causing hyperpolarization (membrane becomes more negative)
Page 82
Describe the types of refractory period and the effects of these refractory periods on axonal conduction
Axonal conduction- axon potentials travel along the axonic membrane in the same direction
Absolute- the period where it’s impossible to initiate another action potential
Relative- the period where it is possible to die the neuron again but only by applying higher-than-normal levels of stimulation. Harder to initiate another action potential
The refractory periods limit the rate of firing (based on level of stimulation)
Describe saltatory conduction
Saltory conduction: the transmission of action potentials in myelinated axons
- passive conduction (instant and decremental) occurs along each myelin segment to the next node of Ranvier
- A new action potential is generated at each node
- Is faster than non-saltory conduction
Describe the process of exocytosis
The process of neurotransmitter release
Exocytosis= Ca2+
- arrival of an AP at the terminal opens voltage-activated Ca2+ channels
- the entry of Ca2+ causes vesicles to fuse with the terminal membrane and release their content
Describe the difference between iontropic and metabotropic receptors
Iontropic- directly associated with ligand-activated ion channels in postsynaptic membrane, induce brief EPSPs or IPSPs
Metabotropic- associated with signal proteins attached to G proteins, leads to either activation of ion channels and membrane potential charge or to production of second messenger
What are some processes that deactivate neurotransmitter?
Reuptake, enzymatic degradation, recycling
Describe processes that deactivate neurotransmitters including reuptake, enzymatic degradation, and recycling.
Reuptake- more common, the majority of the neurotransmitters, once released, are almost immediately drawn back into the presynaptic buttons by transporters mechanisms
Enzymatic degradation- enzymes break apart neurotransmitter in synapse
Recycling- terminal buttons recycle neurotransmitters or their breakdown products after they are released and reuptake occurs
Page 89
Describe autoreceptors
- Metabotropic receptors that have two unconventional characteristics
- They bind to their neuron’s own neurotransmitter molecules
- They are located on the presynaptic.
- Their usual function is to monitor the number of neurotransmitter molecules in the synapse.
Which of the amino acid neurotransmitters is not common in proteins we consume and how is it synthesized?
GABA
GABA is synthesized by a simple modification of the structure glutamate.
Describe the steps required for synthesis of catecholamines from tyrosine
1) tyrosine is converted to L-dopa
2) which in turn is converted to dopamine
3) extra enzyme and neuron’s convert dopamine to norepinephrine
4) extra enzyme in neuron’s convert norepinephrine to epinephrine
(Short answer)
How is serotonin different from dopamine, epinephrine, norepinephrine?
- Serotonin is synthesized from the amino acid tryptophan
- classified as an indolamines
- the other catecholamines synthesized from amino acid tyrosine
Describe how acetylcholine is reduced in the synapse? How does this relate to Alzheimer’s disease and treatment of Alzheimer’s disease?
It’s one of the few neurotransmitters broken down by enzymatic degradation in the synapse by the enzyme acetylcholinesterase
Acetylcholine transmission is decreased significantly in Alzheimer’s disease. Acetylcholine inhibitors are used to treat Alzheimer’s disease
Describe characteristics of soluble-gas neurotransmitters
1) unconventional neurotransmitters
2) synthesized in neural cytoplasm
3) once synthesized immediately diffuse through cell membrane into extracellular fluid and into nearby cells
4) extra enzyme in neuron’s convert norepinephrine to epinephrine
Describe characteristics of endocannabinoids
- synthesized from fatty tissue in cell membrane
- released from dendrites in cell bodies immediately after they are synthesized form fatty tissues in the cell membrane
- the main psychoactive, have effects on presynaptic neuron’s in that they inhibit subsequent transmission
