PSYC 375: Brain and Sensory Processes Exam 2 Copy

Na+

What are Ach-gated and glutamate-gated ion channels permeable to?

Depolarization

What does the influx of Na+ cause?

Brings Vm towards threshold for generating APs, causing EPSP

What does depolarization do to Vm and what does it cause?

Cl-

What are GABA-gated ion channels permeable to?

Hyperpolarization

What does the influx of Cl- cause?

Brings Vm away from threshold for generating APs, causing IPSP

What does hyperpolarization do to Vm and what does it cause?

Dendrites of some neurons that have voltage-gated sodium and calcium channels

What are excitable dendrites?

1. Can boost signal from dendritic terminals
2. Trigger voltage-gated Ca2+ channels to open if EPSP sufficiently large enough

What do excitable dendrites cause?

In opposite direction

from soma outward along dendrites

How do dendritic voltage-gated Na+ channels carry electrical signals?

Subthreshold EPSP in conjunction with a back propagated Na+ spike

What can cause a Ca2+ spike?

Drops off exponentially with distance

What do EPSP's do in dendrites?

Lack of excitable membrane

no voltage-gated ion channels

Why do EPSP's drop off exponentially with distance in dendrites?

0

What does the amplitude of an EPSP approach as it approaches the soma?

The distance where the depolarization is 37% of that at the origin

What is the length constant?

Resistance to current flow down the dendrite (internal resistance) and resistance to current flow across the membrane (membrane resistance)

What is the length constant dependent on?

High internal resistance and low membrane resistance

What generates a short length constant?

Low internal resistance and high membrane resistance

What generates a long length constant?

Synaptic vesicles

What are the elementary units of synaptic transmission?

Spontaneous exocytosis of a single synaptic vesicle

What are miniature postsynaptic potentials triggered by?

Used to determine number of vesicles that release during neurotransmission

What is quantal analysis?

One synaptic vesicle's worth--does not cause much of a change in postsynaptic cell's membrane potential

A CNS synapse is equal to…

EPSPs added together to produce significant postsynaptic depolarization

What is integration?

EPSP generated simultaneously at different synapses

What is spatial summation?

EPSP generated at same synapse in rapid succession

What is temporal summation?

ONLY when there is sufficient postsynaptic depolarization

when there is significant temporal and/or spatial summation of postsynaptic potentials

When do APs generate?

Yes--threshold reaches if there is a net excitation

Do both IPSPs and EPSPs summate?

When EPSPs can be diminished by inhibitory synapses

What is shunting inhibition?

Transmitter-gated ion channels and G-protein couples receptors

What are the two basic types of neurotransmitter receptors?

No--but they can activate ion channels

Are G-proteins ion channels?

1. Bind to receptor
2. Receptor protein activate G-proteins
3. G-proteins activate effector proteins

Steps of neurotransmitter action?

1. G-protein gated ion channels
2. Enzymes that synthesize second messenger molecules

What can a G-protein activate (aka: what are the effector proteins)?

Ion channel function and metabolism of postsynaptic cell

What do second messengers regulate/influence?

Metabatropic receptors because they have widespread metabolic effects

What are G-proteins often called and why?

True

True or false: some neurons can actually generate action potentials in their dendrites

Voltage-gated sodium and calcium channels

What do some neurons (cortical pyramidal neurons) have in their dendrites that cause APs?

Dendritic terminals

Where can excitable dendrites boost signals from?

Enough summation from EPSP or an Na+ spike

What can cause a calcium spike?

It will trigger voltage-gated Ca2+ channels to open, which causes a calcium spike

If EPSP is sufficiently large, what will happen?

True

True or false: the action potential created by EPSP does not degenerate over time

From soma outward along dendrites

How do dendritic voltage-gated Na+ channels carry Na+ spikes?

Subthreshold EPSP in conjunction with a back propagated Na+ spike

What two things in conjunction can trigger a Ca2+ spike?

Smaller EPSPs near soma
Larger EPSPs near dendritic terminals

What are the sizes of EPSPs near the soma and at dendritic terminals in hippocampus pyramidal neurons?

Peptide neurotransmitters

What do secretory granules contain?

Only when there is a high frequency of stimulation (aka many APs in rapid succession)

When do secretory granules release contents?

Synaptic transmission that modifies effectiveness of EPSPs and IPSPs generated by other synapses with transmitter-gated ion channel

What is modulation?

Activating NE beta receptors

What is an example of modulation?

1. Binding to receptor activates G-protein
2. G-protein activates enzyme anenylyl cyclase
3. Adenylyl cyclase converts ATP to the second messenger (cAMP)
4. cAMP activates a protein kinase
5. Kinase causes K+ channel to close via phosphorylation (phosphate group (PO3) added to protein)

What are the steps to activating NE beta receptor in modulation?

-Decrease K+ conductance
-Less K+ will flow across membrane
-Produces increase in dendritic membrane resistance resulting a longer length constant

What does closing K+ channels through modulation result in?

Presynaptic receptor

What is an example of an auto-receptor?

Neurotransmitters released by presynaptic terminal

What are presynaptic receptors sensitive to?

Typically G-protein-coupled receptors that stimulate second messenger formation

What kind of receptors are presynaptic receptors?

Neurotransmitter release and sometimes neurotransmitter synthesis

What do presynaptic receptors inhibit?

They reduce the release of neurotransmitters when levels are high in the synaptic cleft

How do presynaptic receptors act as safety values?

Autoregulation

What is this "safety valve" action called?

Away from the synapse

Where does diffusion occur during chemical synaptic transmission?

When neurotransmitters re-enter the presynaptic axon terminal

What is reuptake?

Amino acid and amine neurotransmitters

What does reuptake occur most with?

Transporters (located on the presynaptic membrane and sometimes glia)

What are reuptakes meditated by?

Enzymatic destruction or reloading into presynaptic membrane

What else do transporters do?

When neurotransmitters are not ridded from the postsynaptic cleft

What is desensitization?

Enzymatic breakdown within synaptic cleft

Desensitization occurs without what process?

Study of the effect of drugs on synaptic communication

What is neuropharmacology?

Inhibitors of neurotransmitter receptors
Curare -blocks the action of Acetyl Choline at nicotinic ACh receptors

What are receptor antagonists? Example?

Mimic actions of naturally occurring neurotransmitters
Nicotine - Mimics action of Acetyl choline at nicotinic ACh receptors

What are receptor agonists? Example?

AMPA, NMDA, Kainate

What are the three kinds of glutamate receptors?

The agents that bind to the receptor

What are the glutamate receptors named after?

True

True or False: glutamate activates all three receptors, but they are selective for the agonists that were used to identify them

The postsynaptic membrane

What do NMDA and AMPA receptors often coexist on?

Na+

What enters through the AMPA channels?

Na+ and Ca2+

What enters through the NMDA channels?

Generating EPSP

What do both NMDA and AMPA receptors contribute to?

Voltage-gated and transmitter-gated

NMDA channels are…

Glutamate

What causes NMDA channels to open?

Pore is blocked by Mg2+

What happens to the NMDA receptors at resting Vm?

Depolarization of membrane

What causes Mg2+ to be pushed out, allowing Na+ and Ca2+ to enter?

GABA

What is the primary inhibitory neurotransmitter in the CNS?

Cl-

What are GABA receptors permeable to?

Synaptic inhibition

What is tightly controlled in GABA receptors?

Coma

Too much synaptic inhibition leads to?

Seizure

Too little synaptic inhibition leads to?

A general anesthetic

What is the GABA agonist used as?

IPSP

Would a K+ permeable channel produce an EPSP or an IPSP?

Benzodiazepines and barbiturates--they enhance the functioning of GABA receptors

What two chemicals can bind to GABA receptors?

The frequency of channels openings

Benzodiazepines increase…

The duration of channel openings

Barbiturates increase…

Cl-

What do both benzodiazepines and barbiturates allow in?

Larger IPSPs and inhibition

A large influx of Cl- causes what?

Naturally occurring chemicals that that either enhance or suppress inhibitory function

What are neurosteroids?

GABA and glutamate

What are the amino acid neurotransmitter?

GAD

What enzyme converts glutamate to GABA?

A group of neurotransmitters with the amino acid tyrosine as their precursor

What are catecholamines?

Dopamine, norepinephrine, epinephrine

What are the catecholamines?

In regions of the brain of movement and reward

Where are catecholaminergic neurons found?

The enzymes present

What determines which catecholamine is produced?

Tyrosine hydroxylase

What do all catecholaminergic neurons contain?

Dopa decarboxylase (which is abundant in catecholaminergic neurons

What makes dopa into dopamine?

Brain systems that regulate emotion, mood, and sleep

What do serotinergic neurons play an important role in?