Neurotransmitter Receptors Quiz

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Questions and Answers

What occurs when neurotransmitters are removed from their receptors?

They produce continuous postsynaptic effects.

They degrade only in the synaptic cleft.

They bind to a different type of receptor.

They might be reabsorbed by astrocytes or presynaptic terminals. (correct)

Which synaptic potential is characterized by transient depolarization of the postsynaptic membrane?

Inhibitory postsynaptic potential (IPSP)

Both EPSP and IPSP cause depolarization.

Excitatory postsynaptic potential (EPSP) (correct)

Synaptic delay influences EPSP generation.

What role do GABA and glycine play in neural signaling?

They primarily cause excitatory postsynaptic potentials.

They are responsible for synaptic delays.

They contribute to transient hyperpolarization. (correct)

They serve only in the peripheral nervous system.

Which of the following receptors are classified as ionotropic receptors?

Nicotinic ACh receptors Signup and view all the answers

What is the significance of synaptic integration in neural computation?

It combines multiple synaptic potentials in one neuron. Signup and view all the answers

Which types of G proteins do M1, M3, and M5 metabotropic receptors couple to?

Pertussis toxin-insensitive G proteins Signup and view all the answers

What is the primary role of NMDA-gated channels in the brain?

Influencing calcium ion concentration and learning functions Signup and view all the answers

Which of the following is true about AMPA receptors?

They are found in most excitatory synapses and mediate fast excitation Signup and view all the answers

Which neurotransmitter is predominantly associated with inhibitory synapses in the brain?

GABA Signup and view all the answers

What type of receptors do benzodiazepines and barbiturates specifically target?

GABAA receptors Signup and view all the answers

What distinguishes the different groups of metabotropic glutamate receptors?

Their subunit composition and pharmacological properties Signup and view all the answers

How does the probability of ionotropic GABA and glycine channels opening relate to neurotransmitter concentration?

It is directly proportional Signup and view all the answers

Which process primarily utilizes the glutamate-glutamine cycle?

Synthesis and recycling of glutamate Signup and view all the answers

What effect does glycine binding to its receptors have on the postsynaptic neuron?

Inhibition of the postsynaptic neuron Signup and view all the answers

Which statement accurately describes the GABAB receptor?

It activates K+ channels through a metabotropic mechanism. Signup and view all the answers

What role does glycine play in NMDA receptor activation?

It acts as a co-agonist with glutamate. Signup and view all the answers

Which neurotransmitter is synthesized from the amino acid serine?

Glycine Signup and view all the answers

Barbiturates enhance the activity of which type of receptor?

GABAA receptors Signup and view all the answers

What effect does the activation of K+ channels through GABAB receptors have on the postsynaptic cell?

Leads to hyperpolarization Signup and view all the answers

Which neurotransmitter is considered a biogenic amine and is derived from tyrosine?

Dopamine Signup and view all the answers

What is the primary function of glycine in the central nervous system?

Providing inhibitory control Signup and view all the answers

Study Notes

Metabotropic Receptors

Metabotropic receptors are coupled to different G proteins and can thus have distinct effects on the cell
M1, M3, and M5 are coupled to pertussis toxin-insensitive G proteins
M2 and M4 are coupled to pertussis toxin-sensitive G proteins
Each set of G proteins is coupled to different enzymes and second messenger pathways

Glutamate

Glutamate is the major excitatory neurotransmitter in the central nervous system
Glutamate has both ionotropic and metabotropic receptors
Ionotropic receptors subtypes are AMPA, Kainate and NMDA

AMPA Receptors

AMPA-gated channels are found in most excitatory synapses in the brain
AMPA receptors mediate fast excitation

NMDA Receptors

NMDA-gated channels have more complex behavior
NMDA channels are permeable to Na+, K+, and Ca2+
Ca2+ permeability allows NMDA receptors to influence intracellular Ca2+ levels
Ca2+ can activate many enzymes, regulate the opening of a variety of channels, and affect the expression of genes
Excess Ca2+ can precipitate the death of a cell
NMDA-gated channels coexist with AMPA-gated channels in many synapses of the brain

Metabotropic Glutamate Receptors

Eight genes coding for metabotropic glutamate receptors have been identified and classified into three groups
Group I receptors are found mainly postsynaptically
Groups II and III are found mainly presynaptically

Inhibitory Amino Acid Receptors: GABA and Glycine

Both glycine and GABA (GABAA and GABAC) have ionotropic receptors
Each of these receptors has a Cl- channel

Glycine

Glycine-mediated inhibitory synapses predominate in the spinal cord
Glycine receptors are ionotropic receptors (ligand-gated chloride channels)
Glycine also serves as a co-agonist with glutamate at NMDA receptors in the CNS

GABA

GABAergic synapses make up the majority of inhibitory synapses in the brain
GABAA receptors are the targets of two major classes of drugs: benzodiazepines and barbiturates
GABAB receptor is a metabotropic receptor

Termination of Neurotransmitter Effects

Neurotransmitter bound to a postsynaptic neuron produces a continuous postsynaptic effect
Neurotransmitter must be removed from its receptor
Removal of neurotransmitters occurs when they are degraded by enzymes, reabsorbed by astrocytes or the presynaptic terminals, or diffuse from the synaptic cleft

Synaptic Delay

Neurotransmitter must be released, diffuse across the synapse, and bind to receptor
Synaptic delay – time needed for this process (0.3-5.0 ms)
Synaptic delay is the rate-limiting step of neural transmission

Postsynaptic Potentials

EPSP: Transient postsynaptic membrane depolarization by presynaptic release of neurotransmitter
EPSPs are caused by Ach- and glutamate-gated channels
IPSP: Transient hyperpolarization of postsynaptic membrane potential caused by presynaptic release of neurotransmitter
IPSPs are caused by glycine- and GABA-gated channels

Synaptic Integration

The combining of excitatory and inhibitory signals acting on adjacent membrane regions of a neuron
In order for an action potential to occur, the sum of excitatory and inhibitory postsynaptic potentials (local responses) must be greater than a threshold value

Acetylcholine (ACh)

Released from all preganglionic and most postganglionic neurons in the parasympathetic nervous system and from all preganglionic neurons in the sympathetic nervous system
Ach is the transmitter at neuromuscular junction and also within the CNS

Nicotinic ACh receptors

Ionotrophic; nonselective cationic channel

Muscarinic ACh receptors

There are five known muscarinic subtypes of ACh receptors (M1 to M5)

Biogenic Amines

Dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), serotonin (5-hydroxytryptamine [5-HT]) are biogenic amines that act as neurotransmitters
Dopamine, norepinephrine, and epinephrine are catecholamines, and they share a common biosynthetic pathway that starts with the amino acid tyrosine

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Description

Test your knowledge on metabotropic and ionotropic receptors, focusing on glutamate and its major receptor subtypes like AMPA and NMDA. Understand how these receptors influence neuronal signaling and their distinct roles within the central nervous system.