DPT 756 Lec 3 pt 2 Ionotropic & metabotropic

How many neurons per muscle at the neuromuscular junction? In the CNS?

NM junction: 1 motor neuron per muscle fiber

CNS: 100s to 1000s of neurons per muscle

Does the NM junction receive excitatory or inhibitory inputs? CNS?

NM junction: Only excitatory

CNS: Excitatory and inhibitory

Types of neurotransmitters used by NM junction? CNS?

NM junction: Only ACh

CNS: Many different neurotransmitters

Types of receptors in NM junction? CNS?

NM junction: Only ionotropic nicotinic ACh receptors

CNS: Ionotropic and metabotropic receptors

Efficiency of NM junction synapses? CNS?

NM junction: Efficient

CNS: Modestly efficient

How does inhibition affect the firing pattern of spontaneously active neurons?

Inhibitory input can causes inhibition of action potentials, leading to a change in beat frequency

Classes of glutamate receptors (3 total). Which are ionotropic? Metabotropic?

AMPA (Ionotropic)

NMDA (Ionotropic)

1 metabotropic

Can the function of synapses be modulated by experience?

Yes

Long-term receptor expression is caused by this phenomenon

Plasticity (the brain's ability to adapt to new demands)

Criteria for NMDA receptors to conduct calcium into postsynaptic cell (2)

Glutamate is released from presynaptic cell

Magnesium is released from receptor d/t depolarization of postsynaptic membrane

Effect of calcium on postsynaptic transmission... How does this affect memory?

Enhances postsynaptic transmission

Necessary for most types of memory

Describe the relationship between glutaminergic excitotoxicity and recovery post-stroke

After having a stroke, patients should do little exercise to reduce glutamate transmission to the damaged tissues (glutamate harms them)

Speed of ionotropic receptor transmission

Fast and brief responses

Basic function of ionotropic receptors

Mediate behaviors: From simple reflex behaviors, to complex cognitive processes

Speed of metabotropic receptor transmission

Slow and lasting responses

Basic function of metabotropic receptors

Modulate actions on emotional states, mood, arousal, simple forms of learning and memory

Variability of metabotropic transmission (how many transmitters, hormones, growth factors?)

Variable

Many transmitters, hormones, growth factors

Alterations in metabotropic transmission can cause these conditions (4)

Depression

Anxiety

Schizophrenia

PD

Drugs to treat neuro and psychiatric disorders may act on what structures?

Metabotropic receptors

Types of metabotropic receptors (2)

G-protein coupled receptors

Tyrosine kinase receptors

How does the G-protein initiate building a new receptor?

Causes release of ATP, which enhances and promotes DNA to transcribe new protein

G-protein tells DNA to build what type of protein?

A new receptor (for the thing you are actively learning)

Things that DNA builds after G-protein calls for it (2)

New receptors

New ion channels

How is short-term plasticity translated into long-term?

Via repetition, a channel is saturated and more receptors are built

Describe the first step of the synaptic vesicle cycle

Vesicles in the terminal bouton are filled with neurotransmitter

Second step of synaptic vesicle cycle

Vesicles fuse to the synaptic membrane when enough calcium is present in synaptic bouton

Third step of synaptic vesicle cycle

SNARES (velcro) attach vesicles to docking zone (end of bouton) and prepare them from release

Fourth step of synaptic vesicle cycle

Neurotransmitters are released via exocytosis

Final step of synaptic vesicle cycle

Vesicle is reuptaken into cell and reused for more neurotransmitter transport

How does botox affect SNARE proteins?

Prevent proper vesicle recycling

Results of botox (4)

Poor muscle control

Spasms

Paralysis

Death (rare)

How do physical therapists use botox injections?

In people with spasticity (especially unilaterally), it can be used to relieve tone