Sharpe's Flashcards
How does neurotransmission occur?
Neurons in the brain communicate with electrical signals with each other
What is the synapse?
The space between two neurons where neurotransmission occurs
What type of signal occurs between neurons?
Usually chemical
How are neurotransmitters packaged?
- vesicles
- active transport is needed to concentrate neurotransmitter into vesicles (antiport)
- Vesicular monoamine transporter (VMAT) of 5-HT, NE, & DA
- therapeutics can block packaging of neurotransmitter, causing their concentration in the axon terminal space to rise
How are neurotransmitters released?
- receives an action potential turning the electrical signal within the neuron into a chemical signal between neurons
- action potential induced depolarization of the membrane at the axon terminal causes the opening of calcium channels which are essential for vesicular release
What types of neurotransmission are there?
classic: neurotransmitter released from axon terminal (presynaptic) acts on either pre- or post-synaptic receptors
retrograde: neurotransmitter is released from post-synaptic neuron and acts on pre-synaptic neuron (endocavanoids not covered)
What types of receptors are there?
inotropic (ligand-gated ion channels): fast, usually POST-synaptic (ex. nicotinic ACh, GABA A receptors, glutamate receptors, glycine receptors, 5-HT3 receptors)
metabotropic (G-protein coupled receptors): slower than inotropic receptos because they work by activation of ion channels or signal cascades/2nd messenger systems, can be pre- & post-synaptic, subtype of G protein will determine excitatory (Gs) or inhibitory (Gi)
How does the Gs receptor activate?
- increases adenylyl cyclase activity
- opens Ca2+ channels
- inhibits Na+ channels
How does the Gi receptor activate?
- inhibits adenylyl cyclase activity
- closes Ca2+ channels
- opens K+ channels
What is the reuptake of neurotransmitters from the synapse?
“recycling” the neurotransmitter back into the pre-synaptic neuron (not with active transport) more with concentration gradient
ex. SERT, NET, DAT and more
How are neurotransmitters degraded?
enzymatically degradation of neurotransmitter can occur in the synapse or in the pre-synaptic terminal
degradation is one way of terminating the neurotransmitter’s action
in the pre-synaptic terminal, the degradation can decrease the amount of neurotransmitter available for packaging into vesicles
What is in the cerebral cortex
a. frontal lobe–> planning
b. motor lobe
c. speech
d. somato-sensory
e. vision, smelling, hearing
What is in the limbic areas?
a. regions: hippocampus (memory), amygdala (fear/anxiety), limbic cortex
b. functions: memory, mood, biological needs
What is in the midbrain?
a. regions: substantia nigra, basal ganglia
b. functions: movement, motivation, visual/hearing relay
What is in the brainstem?
a. regions: reticular formation, medulla, pons
b. functions: sleep/wake, attention (mainly by reticular formation), breathing, blood pressure maintenance
What is in the spinal cord?
a. connects the body to brain
b. input of peripheral information (pain & position)
c. output of central message (movement, blood pressure maintenance, body temperature maintenance, and respiration)
What is Glutamate?
glutamate= excitatory
- uptake by astrocytes with reuptake transporters specific to glutamate (back to glutamine)
- ionotropic receptors (FAST!) AMPA, NMDA, Kainate
- metabotropic receptors (mGluR, SLOWER) inhibitory, so coupled to Gi
What is GABA?
GABA= inhibitory
- GABAa- ionotropic (binding to these receptors causes Cl- to enter cells = hyperpolarization, receptors where alcohol, barbiturates, benzodiazepines and inhalants all work)
- GABAb- metabotropic/G-protein coupled (can be pre or post, receptos on neurons that release glutamate, dopamine, norepinephrine or serotonin will decrease the release of THOSE neurotransmitters)
What are some Monoamine neurotransmitters?
- Dopamine
- Norepinephrine
- Serotonin
What is Dopamine?
Dopamine (monoamine & catecholamine)
synthesis: tyrosine hydroxylase is the rate limiting step in production of dopamine
vesicles: VMAT in the PRE-synaptic & COMT in the synapse only!
localization: cell bodies mostly limited to- ventral tegmental are (reward, addiction), substantia nigra (movement) and projections to limbic areas (emotion, memory), stratum and cortex
What is Dopamine reuptake?
Dopamine reuptake transporter (DAT)
What are Dopamine receptors?
Metabotropic
D1: coupled to Gs
D2: coupled to Gi, may be presynaptic (autoreceptors) or postsynaptic
What are some diseases related to Dopamine?
Parkinson’s disease
substance abuse
Schizophrenia
ADHD
What is Norepinephrine?
synthesis: synthesized from dopamine (dopamine betahydroxylase converts dopamine to norepinephrine)
vesicles: VMAT
degradation: MAO from presynaptic terminal & synapse & COMT in synapse only
localization: cell bodies mostly limited to (locus ceruleus & brainstem) and projections to amygdala, thalamus and cortex
What is Norepinephrine reuptake?
Norepinephrine reuptake transporter (NET)
What diseases are associated with Norepinephrine?
cognition
depression
PTSD
ADHD
What is Serotonin?
synthesis: from tryptophan
vesicles: VMAT
degradation: MAO in presynaptic terminal and synapse
localization: cell bodies limited to (raphe nucleus) and projections to limbic, midbrain and cortex
What is Serotonin reuptake?
Serotonin reuptake transporter (SERT)
What Norepinephrine receptors are there?
Metabotropic
alpha 1: coupled to Gq
alpha 2: coupled to Gi, may be presynaptic or post
beta: coupled to Gs
What are the types of Serotonin receptors?
13 different types of receptors 12 metabotropic and 1 ionotropic
5-HT3- ionotropic; antagonists at this receptor are used as anti-nausea
5-HT 1D & 1A- inhibitory, autoreceptors; agonists are used for migraine treatment
5-HT 2A- antagonists to this receptors are antipsychotic
What are the diseases associated with Serotonin?
depression
antipsychotics
migraine
obesity/weight loss
What is Acetylcholine?
synthesis: choline + acetylCoA
vesicles: vesicular acetylcholine transporter packages Ach into vesicles in axon terminal
degradation: acetylcholinesterase
localization: cell bodies in forebrain and brainstem; intrerneurons in straitum & projections to limbic areas, cortex and striatum