response to acetylcholine

Definition

Target type: biologicalprocess

Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an acetylcholine stimulus. [GO_REF:0000071, GOC:TermGenie, PMID:21238497]

Acetylcholine, a neurotransmitter, is a critical molecule in the nervous system, mediating a wide range of physiological processes. The response to acetylcholine involves a complex series of events that begin with its release from presynaptic neurons and culminate in the activation of specific cellular pathways.

1. **Release of Acetylcholine:** When a nerve impulse arrives at the synapse, a presynaptic neuron releases acetylcholine from synaptic vesicles into the synaptic cleft, the narrow gap between the presynaptic and postsynaptic neurons. This release is triggered by the influx of calcium ions into the presynaptic terminal.

2. **Binding to Receptors:** Acetylcholine diffuses across the synaptic cleft and binds to its receptors on the postsynaptic membrane. There are two main types of acetylcholine receptors:

* **Nicotinic receptors:** These are ligand-gated ion channels, meaning that acetylcholine binding directly opens the channel, allowing ions to flow across the membrane. Nicotinic receptors are found in both the central nervous system (CNS) and the peripheral nervous system (PNS), including skeletal muscle.

* **Muscarinic receptors:** These are G protein-coupled receptors (GPCRs). Binding of acetylcholine to muscarinic receptors triggers a cascade of intracellular signaling events that ultimately alter cellular function. Muscarinic receptors are found in the CNS and PNS, mediating effects on smooth muscle, cardiac muscle, and glands.

3. **Signal Transduction:** Binding of acetylcholine to its receptors initiates a signaling cascade. In the case of nicotinic receptors, the opening of ion channels leads to a rapid depolarization of the postsynaptic membrane, triggering an action potential. For muscarinic receptors, activation of GPCRs leads to the production of intracellular signaling molecules, such as cyclic AMP (cAMP) or inositol triphosphate (IP3), which regulate various cellular processes.

4. **Cellular Response:** The specific cellular response to acetylcholine depends on the type of receptor involved and the target cell. Examples include:

* **Muscle contraction:** Acetylcholine binding to nicotinic receptors at the neuromuscular junction triggers muscle fiber contraction.

* **Neurotransmitter release:** Acetylcholine plays a role in the release of other neurotransmitters in the CNS, such as dopamine and serotonin.

* **Cardiac function:** Acetylcholine binding to muscarinic receptors in the heart slows down heart rate and reduces the force of contraction.

* **Smooth muscle contraction and relaxation:** Acetylcholine can cause both contraction and relaxation of smooth muscle, depending on the specific type of muscarinic receptor involved and the location.

* **Glandular secretion:** Acetylcholine stimulates the secretion of various glands, such as salivary glands and sweat glands.

5. **Acetylcholine Degradation:** To terminate the signal, acetylcholine is rapidly broken down by the enzyme acetylcholinesterase (AChE). AChE hydrolyzes acetylcholine into choline and acetate, both of which are taken back up by the presynaptic neuron for recycling.

The intricate interplay of acetylcholine release, receptor binding, signal transduction, and degradation ensures that this neurotransmitter effectively mediates a diverse range of physiological processes. Disruptions in acetylcholine signaling can lead to various neurological and muscular disorders.
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Proteins (5)

Compounds (155)