Neurotransmitters & Neurotransmission

Transmission

signaling through nerve impulses, action potential

Synapse

space between neurotransmitters

Glial cells

supports the neurons: metabolic, nutrient supply, insulation

Neurons

fire action potential, nerve cells

Astrocytes

structure support, pH regulator, ion regulator, hormones, BBB homeostasis

Ependym

interface between brain parenchyma and cerebral spinal fluid homeostasis

Microglia

resident phagocyte of brain

Oligodendrocytes

accelerating electrical impulse transmission

Multipolar neurons

What type of neuron is this?

- motor, pyramidal, purkinje

- multiple dendrites, 1 axon

Bipolar neurons

What type of neuron is this?

- retinal, olfactory

- dendrite at 1 polar end, axon on other

Unipolar neurons

What type of neuron is this?

- touch + pain

- two axons with dendrites on end of each axon

Anaxonic neurons

What type of neuron is this?

- amacrine cell

- no axon

Oligodendrocytes are a part of what nervous system?

Central nervous system

Schwann cells are a part of what nervous system?

Peripheral nervous system

Function of Schwann cells and Oligodendrocytes

(they have the same function just in different location)

act as insulators conducting impulses

Sensory input occurs in which nervous system?

Central

Motor output occurs in which nervous system?

Peripheral

What muscle is in charge of ORGANS in motor output?

Smooth muscle

What muscle is in charge of the HEART in motor output?

Cardiac muscle

What muscle is in charge of VOLUNTARY MOVEMENT in motor output?

Skeletal muscle

What is the purpose of neurotransmission?

detect, process, store, and retrieve information

enhanced biological fitness

If the total weighted sum is reached, does the neuron fire?

yes

If the total weighted sum is not reached, does the neuron fire?

no

What are the 5 types of signaling?

endocrine, paracrine, autocrine, synaptic, neuroendocrine

What determines where and when signaling happens?

spatial, temporal specificity

What are 3 types of synapses?

1. synapses w/ another neuron

2. Neuromuscular junctions

3. Neuroglandular synapses

What type of synapse is this describing?

- neuron 1 -> neuron 2

Synapses w/ another neuron

What type of synapse is this describing?

- neuron -> skeletal muscle fibers

Neuromuscular junctions

What type of synapse is this describing?

- neuron -> gland cells

Neuroglandular synapses

What kind of synapse is this (chemical vs. electrical)?

- neurotransmitter carries impulse

Chemical

What kind of synapse is this (chemical vs. electrical)?

- gap junctions pass electrical current

Electrical

What kind of role does the electrical synapse have?

regulatory role , synchronous timing

What contains all of the structures basic to eukaryotic animal cells?

cell body

What collects information from other neurons?

dendrites

What conducts signal away from cell body?

axon

What transmits information to other cells?

axon terminals

What type of synapse is this?

- directly into bloodstream

axosecretory

What type of synapse is this?

- into another axon

- powerful placement, regulates flow, normally inhibitory

axoaxonic

What type of synapse is this?

- ends on dendrite spine

axodendritic

What type of synapse is this?

- no connection, into extracellular fluid

axoextracellular

What type of synapse is this?

- ends on soma

axosomatic

What type of synapse is this?

- ends on another axon terminal

axosynaptic

Which synapse(s) have a regulatory role, like a kill switch?

axodendritic

axosomatic

axosynaptic

What is step 1 of neurotransmission?

presynaptic neuron fires

What happens after the presynaptic neuron fires?

neurotransmitters released from axon terminal into synaptic cleft

What happens after neurotransmitters are released?

neurotransmitter binds to receptors in the plasma membrane of postsynaptic neuron

What prevents backward propagation?

hyperpolarization

What 2 cells speed of propagation?

Schwann + Oligodendrocytes

What channel opens from threshold to peak action potential?

Na+

What channel closes at the peak action potential?

Na+

What channel opens at the peak action potential?

K+

Where are neurotransmitters stored in?

vesicles

granules

produced on demand

Which neurotransmitter storage type(s) can fuse with cell membrane and dump contents into the synaptic cleft (exocytosis)?

vesicles + granules

What happens to neurotransmitters when there is an influx of Ca2+?

neurotransmitters are released

Are vesicles recycled to repackage neurotransmitters or are they discarded?

recycled for repackage

Depolarization opens what channel?

Ca2+

What causes vesicles to fuse?

Ca2+ influx

What are two ways that can remove neurotransmitters?

glial uptake or enzymatic degradation

Botulinum neurotoxins cleave what protein?

SNARE

Without the SNARE protein (because it is cleaved, no longer in action) is there release of neurotransmitters?

no release

What occurs from botulinum neurotoxins cleaving the SNARE protein?

flaccid paralysis

Does the action of botulinum neurotoxins depend on ion channels?

nope

What type of signaling is this?

- opposite direction

- postsynaptic -> presynaptic

retrograde signaling

What are some feedback functions of retrograde signaling?

crosstalk, synaptic plasticity, inhibitory

What is retrograde signaling involved in?

learning, memory, neuroprotection

What substance inhibits retrograde signaling?

Endocannabinoids: 2-AG, anandamide

What substance induces retrograde signaling?

neurotrophins: BDNF

gases: NO, CO

What 2 classes of classification are neurotransmitters are split into?

1. Chemical class

2. Function - impact on membrane potential

What are the 6 categories in the chemical class of neurotransmitters?

amino acids

biogenic amines (monoamine)

lipids

peptides

proteins

gases

What are the 3 categories in the function class of neurotransmitters?

excitatory

inhibitory

modulatory

Inhibitory neurotransmitters impact what?

GABA: chloride channel, negative

Modulatory neurotransmitters impact what?

metabolism

This type of receptor affects ion channels directly?

Ionotropic

This type of receptor affects metabolism and ion channels indirectly?

Metabotropic

What 3 receptors are cell membrane bound?

ionotropic, metabotropic, cell adhesion molecules

What receptor is intracellular?

nuclear receptors

What is this type of receptor?

- milliseconds

- nicotinic, ACh receptor

ligand-gated ion channels (ionotropic)

What is this type of receptor?

- seconds

- muscarinic, ACh recptor

G-protein coupled receptors (metabotropic)

What is this type of receptor?

- hours

- cytokine receptors

Kinase-linked receptors

What is this type of receptor?

- hours

- oestrogen receptors

Nuclear receptors

Ionotropic has what receptor that impacts cAMP?

Gi

Gi (increases/decreases) cAMP

decreases

What type of ion channel is this (excitatory/inhibitory)?

- NMDAR (Na+, Ca2+)

- AMPAR (Na+)

Excitatory

What type of ion channel is this (excitatory/inhibitory)?

- GABAa (Cl-)

Inhibitory

Ketamine is an uncompetitive channel blocker.

Is it an NMDAR agonist or antagonist?

NMDAR antagonist

What is the ligand of NMDA Receptors?

glutamate, glycine co-agonists

What controls the voltage of NMDA Receptors?

Mg2+

What kind of detection is in the NMDAR?

- ligand + positive membrane

Coincidence detection

What is the function of NMDARs?

cell survival, plasticity, development, communication, learning, memory

What type of binding site is this?

- different from GABA site

- not a subunit

allosteric site

What type of binding site is this?

- subunit site of GABA

orthosteric site

Benzodiazepine binds allosterically or orthosterically?

allosteric

Function of PAM binding to chloride ion

enhances Cl- ion conductance

Is PAM binding allosteric or orthosteric?

orthosteric

Gi alpha function

inhibits adenylyl cyclase

Gi beta/gamma function

activates K+ channels

What type of receptor is this?

- when activated -> conformational change

GPCRs

What type of receptor is this?

- detect and respond to neurotransmitter that is released by that neuron

- 5-HT(1A), 5-HT(1B), alpha2A, M2, M4

- negative feedback

- generally inhibitory

Autoreceptor

What are autoreceptors similar to (function)?

presynaptic heteroreceptors w/ axoaxonic synapses

Glutamate and Monoamines are what type of transporters?

uptake transporters