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805 > Lecture 15 > Flashcards

Lecture 15 Flashcards

Intro to Neurons

1
Q

Cell Body

A

Contains nucleus and ER of neuron

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2
Q

Dendrites

A

Receives info from axon and other neuron terminals via neurotransmitter-receptor interactions

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3
Q

Axon

A

Transmits signal from cell body to axon terminals (1-100 m/sec) and transports proteins and lipids to terminals with cytoskeleton

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4
Q

Presynaptic Terminal

A

Synaptic Vessicles store and release neurotransmitters to activate or inhibit neurons

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5
Q

What does PNS Affect?

A

All other excitable tissue: skeletal, smooth, and cardiac muscle.

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6
Q

Postsynaptic Dendrites

A

Receptors bind neurotransmitters and produce ionic responses (EPSP & IPSP), act on second messenger responses, OR direct effect on ion channels (Na, K, Cl, Ca)

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7
Q

Membrane Potential

A
  • Potential difference between inside and outside of neuron
  • -60 to -75 mV
  • Ionic pumps are used on neuron to maintain internal ion concentrations
  • Negatively charged components are inside cell and impermeable
  • Membrane is selectively permeable to K+ ions
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8
Q

Which ion establishes the resting potential?

A

K+

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9
Q

Action Potential Steps (3)

A
  1. Na+ open and influx to depolarize the membrane
  2. Adjacent Na+ channels open and propagate the signal
  3. K+ channels open and return membrane to resting potential
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10
Q

Action Potential Propagation Steps (3)

A
  1. Generation of Action Potential - dendrites/cell body depolarize and open voltage-sensitive Na+ channels
  2. Local current flows passively down axon and open Na+ channels (action potential)
  3. Continues until reaching synaptic terminal
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11
Q

Refractory Period

A
  • Time after action potential when Na+ channel are inactive
  • Reason why action potentials don’t travel backwards
  • Important in mechanism of action of some drugs like antiepileptics and antiarrhythmics
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12
Q

Myelination

A
  • Insulates axon - reduces Na+ leaking and increase the flow distance
  • Myelin wrapped around axon by oligodendrocytes in CNS and Schwann Cells in PNS
  • Nodes of Ranvier are gaps in the myelination
  • Conduction velocities significantly increase with myelination (0.5-10 m/s for unmyelinated and up to 150 m/s when myelinated)
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13
Q

Local Anesthesia

A
  • Must enter neurons and act on open Na+ channels to prevent depolarization by blocking influx
  • High potency for neurons with a high firing rate
  • Binding Site: S5 & S6 transmembrane segments that wall the sodium channel pores
  • Intracellular loop connecting domains III & IV creates inactivation of the sodium channels
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14
Q

Lidocaine

A

Binds domain IV segment S6 portion of Na+ channel to stop neuron signals and influx.

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15
Q

Molecule Characteristics + Effect on Neuron

A

Lipophilic - enters neuron (potency)

Hydrophilic - binds to site (duration of action)

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16
Q

Mechanism of Antiepileptic Drugs

A

Prolongs the inactivation period of Na+ channels by increasing the refractory period and decreasing the sustained, rapid firing of neurons

17
Q

Ion-Channel Receptors - Voltage Dependent Receptors

A
  • Na+ - initiation and propagation of action potential
  • Ca+2 - release neurotransmitters at synapse and contract muscle tissue
  • K+ - sets resting potential, hyperpolarizes tissues, alters action potential duration
  • Cl- - Hyperpolarizes neurons (GABA)
18
Q

Receptor Mediated - Ligand Gated Receptors

A
  • Neurotransmitters bind and control intrinsic ion channel
  • Regulated by phosphorylation
  • Ex: Na and Ca by glutamate and Cl by GABA
19
Q

G Protein-Coupled Receptors

A

-Bound to GTP binding proteins, adenyl cyclase, phospholipase C, or ion channels
Ex: Muscarinic cholinergic receptors, adrenergic receptors, serotonergic receptors, and peptide receptors

20
Q

Heart Example of Receptor Mediated

A
  • B-Adrenergic Agonists increase calcium release

- Affect pattern of heart contraction

21
Q

Receptors + Drug Effects

A
  • Determinant of quantitative relations between dose or drug concentration and pharmacological affects
  • Also responsible for selectivity of drug action and mediates the actions of pharmacologic antagonist and agonists
22
Q

Receptor Affinity + Drug Effects

A

Determines drug concentration required to form significant number of drug-receptor complexes. Number of complexes could limit the maximal drug effect

23
Q

Molecules with Neurotransmitter/Neuromodulatory Properties

A
  • Dopamine
  • Norepinephrine
  • Epinephrine
  • Serotonin
  • Acetylcholine
  • Glutamine
  • GABA
24
Q

Neurotransmitters

A

Chemical Substances that transmit nerve impulses across a synapse to postsynaptic receptor

25
Q

Catecholamines

A
  • Dopamine, Norepi, Epi
  • CNS and P - sympathetic - NS
  • Work via G-proteins
26
Q

GABA

A
  • IPSP (Inhibitory Postsynaptic Potentials)
  • Hyperpolarization
  • Most abundant inhibitor in CNS
  • Synthesized from L-glutamic acid by GAD
  • GABA-A receptor - increase chloride ions into neuron
  • GABA-B receptor - decreases calcium release
27
Q

Glutamate

A
  • EPSP (Excitatory Postsynaptic Potentials)
  • Most abundant excitor in CNS, excitatory amino acid that has stimulatory affects and high concentrations in brain
  • Receptors increase sodium and calcium ion influx to depolarize neuron
  • PCP receptor inside channel and interacts with NMDA receptor
28
Q

Catecholamine Process

A

Synthesis&raquo_space; Storage&raquo_space; Release&raquo_space; Receptors or Uptake&raquo_space; Metabolism

29
Q

GABA-A

A
  • Ligand-gated channel with alpha and beta units (react with benzodiazepines and barbiturates, BOTH INCREASE AFFINITY OF GABA FOR RECEPTOR)
  • GABA binding site causes Cl- influx and hyperpolarization
  • Benzos - bind separate from GABA site and have potentiate binding of GABA (doesn’t work in its absence), antagonist = Flumazeril (Romazicon)
  • Barbiturates - opens Cl- channel by activating GABA directly, potentiate binding of GABA but can still work in its absence
30
Q

GABA-A Therapeutic Uses (4)

A
  1. Sedative/hypnotics - Temazepam (Restoril) & Zolpidem
  2. Antianxiety - Xanax
  3. Antiepileptic - Phenobarbital (Luminal)
  4. Muscle Relaxants - Clonazepam
31
Q

Neuromodulators

A

Affect function of neurons but doesn’t act as a neurotransmitter itself.

32
Q

PCP Receptor

A
  • PCP and Ketamine interact with receptor
  • Inhibit passage of Ca+2 and Na+
  • Indirectly antagonize glutamate
  • Act as noncompetitive antagonists
33
Q

NMDA Receptor Roles

A
  1. Long term plasticity - learning, memory, epilepsy
  2. Ischemia/Hypoglycemia - induced massive release of glutamate which increases calcium concentrations and leads to cell damage or death
  3. Neurological Disorders - stroke
  4. Neurodegenerative diseases - Alzheimer’s (treated with Memanitine [Namenda], which is a glutamate antagonist)

805 (18 decks)

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