3.1 The presynaptic neuron releases a neurotransmitter. The neurotransmitter communicates with the postsynaptic cell. Flashcards
What is the distinction between endogenous and exogenous substances?
Endogenous substances: Chemicals produced within the body (e.g., neurotransmitters like acetylcholine).
Exogenous substances: Chemicals introduced from outside the body (e.g., drugs, toxins, medications).
What happens when an action potential arrives at the axon terminal?
1)Depolarization opens voltage-gated calcium (Ca²⁺) channels.
2)Ca²⁺ inflow causes synaptic vesicles to release neurotransmitters into the synaptic cleft (exocytosis).
3)Neurotransmitters bind to receptors (ionotropic or metabotropic) on the postsynaptic membrane.
4)Excess neurotransmitter is cleared by enzymatic breakdown or reuptake.
What are the two types of neurotransmitter receptors, and how do they differ?
-Ionotropic receptors: Fast-acting, contain ion channels that open/close when bound by neurotransmitters.
-Metabotropic receptors: Slower, activate G proteins and second messengers to cause broader cellular changes.
What is reuptake, and why is it important?
-Reuptake is the process where neurotransmitters are transported back into the presynaptic terminal for recycling.
-It ensures neurotransmitter levels are regulated and synapses are cleared.
How was the first neurotransmitter, acetylcholine, discovered?
-Otto Loewi electrically stimulated a frog’s vagus nerve, slowing its heart.
-He transferred the surrounding fluid to a second frog’s heart, causing it to also slow.
-This proved chemical neurotransmission, not electrical signals, slowed the heart.
Why is acetylcholine significant in neuroscience history?
-It was the first neurotransmitter discovered, supporting the “soups” hypothesis of chemical communication.
-Otto Loewi’s discovery earned him a Nobel Prize in 1936.
Why might evolution have favored multiple subtypes of neurotransmitter receptors?
-Receptor diversity allows nuanced responses, enabling the brain to regulate fast actions (e.g., reflexes) and slower, complex behaviors (e.g., emotions, learning).
-It supports specialized functions in different brain regions and adaptable signaling.
What are ionotropic receptors often compared to, and why?
They are likened to “keys opening locks” because neurotransmitters bind and directly cause the receptor to open or close ion channels.
What are some long-term effects of metabotropic receptor activation?
Changes in gene expression, remodeling of neural connections, or production of additional receptors and signaling molecules.
Why do ionotropic and metabotropic receptors add complexity to neural signaling?
They allow a single neurotransmitter to interact with multiple receptor subtypes, each producing different effects.
