Introduction[edit | edit source]
Acetylcholine (ACh), the first neurotransmitter discovered, is now known to be a neurotransmitter at the neuromuscular junction, all autonomic ganglia, at many autonomically innervated organs, and at many synapses in the CNS. ACh is stored in vesicles at the ends of cholinergic (acetylcholine-producing) neurons.
Muscles[edit | edit source]
Human peripheral nervous systems require acetylcholine to excite the activation of muscle function properly. Systems work by using acetylcholine in smooth muscles, essential for muscle contraction. When something does block acetylcholine, it can lead to muscle weakness and even paralysis in some cases.
The activation of muscle function involves: a nerve impulse arriving at the terminal of a motor neuron; ACh is released into the neuromuscular junction; it combines with a receptor molecule in the postsynaptic membrane of a muscle fibre, changing the permeability of the membrane, causing channels to open that allow positively charged sodium ions to flow into the muscle cell; if successive nerve impulses accumulate at a sufficiently high frequency, sodium channels along the end-plate membrane become fully activated, resulting in muscle cell contraction.
Parasympathetic Nervous System[edit | edit source]
ACh is the chief neurotransmitter of the parasympathetic nervous system, the part of the autonomic nervous system, that contracts smooth muscles, dilates blood vessels, increases bodily secretions, and slows heart rate. ACh can stimulate a response or block a response and thus can have excitatory or inhibitory effects.
Organ Systems[edit | edit source]
- In the gastrointestinal system (through stimulation of the vagus nerve) the tone, the amplitude of contractions, and the secretory activity of the stomach and intestine increase, sphincters are released.
- In the respiratory system, it determines bronchoconstriction and stimulation of the chemoreceptors of the aortic and carotid glomus, with consequent reflex hyperpnea.
- In the urinary system, parasympathetic sacral stimulation causes contraction of the detrusor muscle of the bladder, increasing the emptying pressure and ureteral peristalsis, the release of sphincters.
- In the exocrine glands, it stimulates the secretion of all the exocrine glands that receive a parasympathetic innervation, including the lacrimal, tracheobronchial, salivary, digestive glands, and the exocrine sweat glands.
- In the eye, it determines miosis and accommodation of the lens in close vision, inducing the contraction of the sphincter muscle of the pupil and the ciliary muscle.
- In the male reproductive system, it causes erection.
CNS[edit | edit source]
In the central nervous system, ACh is found primarily in interneurons. A few important long-axon cholinergic pathways have also been identified. eg: the cholinergic projection from the nucleus basalis of Meynert (in the basal forebrain) to the forebrain neocortex and associated limbic structures (degeneration of this pathway is one of the pathologies associated with Alzheimer's disease).
Physiotherapy Relevance[edit | edit source]
Acetylcholine is a critical neurotransmitter that plays an important role in the normal function of the brain and body. Disruptions in the release and function of this neurotransmitter can result in significant problems in areas such as memory and movement.
Anticholinergics[edit | edit source]
Anticholinergic agents are substances that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. They inhibits parasympathetic nerve impulses by selectively blocking the binding of the neurotransmitter acetylcholine to its receptor in nerve cells. As anticholinergics can affect a variety of functions, including digestion, urination, salivation, and movement, they can help treat many conditions.
Three categories exist, with specific targets in the central and/or peripheral nervous system: antimuscarinic agents, ganglionic blockers, and neuromuscular blockers.
Anticholinergics can help treat various health conditions, including:
- Respiratory disorders, eg COPD, asthma
- Overactive bladder and Urinary Incontinence
- Symptoms of Parkinson’s disease, eg tremor see Parkinson's Pharmacotherapy
- Cardiovascular disease
- Gastrointestinal symptoms, eg vomiting
- Palliative care for the treatment of smooth muscle spasm (e.g., bladder, intestine), drying secretions (sialorrhea, drooling, noisy respiratory secretions or "death rattle"), inoperable intestinal obstruction, and disease-related pyrexia.
References[edit | edit source]
- Neuroscience Acetylcholine Available: https://nba.uth.tmc.edu/neuroscience/m/s1/chapter11.html (accessed 3.5.20220
- Britannica Acetylcholine Available: https://www.britannica.com/summary/acetylcholine (accessed 3.5.2022)
- Sam C, Bordoni B. Physiology, Acetylcholine. InStatPearls [Internet] 2021 Apr 17. StatPearls Publishing.Available:https://www.ncbi.nlm.nih.gov/books/NBK557825/ (accessed 3.5.2022)
- Very well mind What is ACh Available:https://www.verywellmind.com/what-is-acetylcholine-2794810 (accessed 3.5.2022)
- Pallipedia Anticholigenics Available:https://pallipedia.org/anticholinergics-antimuscarinics/ (accessed 4.5.2022)
- Medical news today Anticholigenics Available;https://www.medicalnewstoday.com/articles/323514#uses (accessed 4.5.2022)