Neuromuscular Junction Flashcards
What is synaptic transmission?
postsynaptic signaling interpreting the transmitted signal into a change in postsynaptic Vm
What are the 2 types of connections within synaptic transmission?
axiosymatic and axiodendritic
What are the classes of mmebrane receptors?
ionotropic (ligand gated) and metabotropic (GPCR)
What type of response is ionotropic?
fast
What type of response is metabotropic?
slower and variable
What are the 5 ionotropic receptors?
- Ach
- glutamate
- 5-HT3
- GABA
- glycine
What is the Ach receptor?
- receptor at neuromuscular junction
- plays role in learning and memory
- curare
What is the glutamate receptor?
- NMDA, AMPA receptors
- letamine
What is the 5-TH3 receptor?
- all antagonists are antiemetic
- serotonin receptor channel
What is the GABA receptor?
- types A and C
- causes membrane potential hyperpolarization through Cl-
- benzodiazepines, kava, valerian
What is the glycine receptor?
- glycine and taurine (agonist)
- strychnine (antagonist, rat poison)
What are the 4 types of metabotropic receptors?
- Ach
- metabotropic glutamate
- biogenic amines
- GABA
Metabotropic receptors have what type of coupled receptors?
G protein
What type of GABA receptor is in metabotropic receptors?
- type B
- agonists: ethanol and baclofen
How many transmembrane segments does the receptor structure have?
7
What occurs when the G protein is activated after metabotropic receptor activation?
- directly activates/deactivates channel
- activation of effector molecule; synthesis/activation of 2nd messenger
What occurs when there is an activation of effector molecule synthesis/activation of 2nd messenger after metabotropic receptor activation?
- increases/decreases kinase activity
- directly activates/deactivates channel
What occurs when there is an increase/decrease in kinase activity after metabotropic receptor activation?
- leads to phosphorylation/dephosphorylation of ion channels causing change in channel activity
- cause increase/decrease in channel subunit/protein production
What are the sources of Ca+?
- plasma membrane: voltage gated Ca+ channels, various ligand channels
- endoplasmic reticulum: IP3 receptors, ryanodine receptors
What are the removal mechanisms of Ca+?
- plasma membrane: Na+/Ca+ exchanger, Ca+ pump
- ER: Ca+ pump
- mitochondria
What are the sources for cAMP?
adenylyl cyclase
What is the intracellular target for cAMP?
protein kinase A
What is the source for IP3?
phospholipase C
What is the intracellular target for IP3?
IP3 receptors on ER
What is the source for diacylglycerol?
phospholipase C
What is the intracellular target for diacylglycerol?
protein kinase C
What are the second messengers?
- Ca+
- cAMP
- IP3
- diacylglycerol
What is the G-protein, cascade, and target action for norepinephrine?
- G-protein: Gs
- cascade: adenylyl cyclase -> cAMP -> protein kinase A
- target: increase protein phosphorylation
What is the G-protein, cascade, and target action for glutamate?
- G-protein: Gq
- cascade: phospholipase C -> diacylglycerol -> protein kinase, IP3 -> Ca+ release
- target: increase protein phosphorylation and activate Ca binding proteins
What is the G-protein, cascade, and target action for dopamine?
- G-protein: Gi
- cascade: adenylyl cyclase -> cAMP -> protein kinase A
- target: decrease protein phosphorylation
What are EPSPs?
postsynaptic potentials that increase probability of causing the postsynaptic cell to fire an AP
What are IPSPs?
postsynaptic potentials that decrease probability of causing the postsynaptic cell to fire an AP
What is the relationship between EPSPs and the threshold?
reverse potential of induced conductance is more positive than threshold
What is the relationship between IPSPs and the threshold?
reverse potential of induced conductance is more negative than threshold
What is the affect of major excitatory neurotransmitters on postsynaptic membrane?
depolarization caused by activation of cationic channels (Na+ and Ca+)
What is the affect of major inhibitory neurotransmitters on postsynaptic membrane?
hyperpolarization caused by activation of chloride channels
What are examples of excitatory neurotransmitters?
- Ach
- glutamate
- serotonin
- histamine
- catecholamines
What are examples of inhibitory neurotransmitters?
GABA and glycine
What is convergence?
several neurons synapse onto a single neuron (input)
What is divergence?
single neuron projects onto several neurons (output)
What is summation?
where the efefcts of all EPSPs and IPSPs determines the excitability of the cell
What determines the excitability of the postsynaptic cell?
temporal and spatial summation of EPSPs and IPSPs
What type of senor types are activated during the stretch reflex?
type 1a/2
What is the simple reflex circuit?
alpha neuron activation of extensors/quads interneuron-mediated inhibitory inactivation of flexors/hamstrings
What is a patellar reflex?
diagnosing lower motor neuron (L2,L4) diseases
What is afferent?
carries info from sensory receptors to CNS
What is efferent?
carry motor info. away from CNS to muscles and glands of body
