Neurotransmitters and what do they do Flashcards
Acetylcholine (ACh)
Think of A and C words?
Involved in muscle contraction, learning, and memory.
1. Muscle Contraction: Acetylcholine is essential for signaling between nerve cells and muscles, facilitating muscle contractions. This is vital for motor control and movement.
2. Memory and Learning: ACh is implicated in memory and learning processes. It is involved in the formation of new memories and is crucial for cognitive functions.
3. Attention and Arousal: Acetylcholine contributes to the regulation of attention and arousal levels. It plays a role in promoting wakefulness and alertness.
4. REM Sleep: ACh is associated with rapid eye movement (REM) sleep, a phase of the sleep cycle linked to dreaming and memory consolidation.
5. Cortical Function: ACh is important for cortical functions, influencing higher cognitive processes such as thinking, reasoning, and perception.
Acetylcholine plays a crucial role in both muscle contraction and cognitive functions by acting as a chemical messenger. In muscle contraction, it enables the transmission of signals from motor neurons to muscle fibers, leading to muscle movement. In cognitive functions, ACh modulates attention, learning, and memory by affecting synaptic plasticity and neuronal activity in the brain. The processes are tightly regulated by enzymes like acetylcholinesterase and feedback mechanisms to ensure proper functioning.
Dopamine:
Stimulation of reward centers in the brain
Plays a role in pleasure, reward, motivation, and motor control.
Amino Acid needed Tyrosine
Serotonin:
Elevated Mood
Regulates mood, appetite, sleep, and social behavior.
Amino Acids needed: Tryptophan
- Why do SSRIs increase the risk of GI bleeding?
SSRIs increase the risk of gastrointestinal (GI) bleeding because they inhibit serotonin reuptake in platelets.
Serotonin plays a role in platelet aggregation (clot formation) – Platelets do not synthesize serotonin but take it up from the bloodstream.
SSRIs block this uptake, leading to reduced serotonin levels inside platelets.
Without enough serotonin, platelets become less effective at forming clots, increasing the risk of bleeding, particularly in the stomach and intestines.
The risk is higher when SSRIs are used with NSAIDs (e.g., ibuprofen, naproxen) or aspirin, as these also impair the stomach lining and clotting ability.
🔹 Key points:
✅ SSRIs impair platelet function → Increased risk of bleeding
✅ Higher risk when combined with NSAIDs, aspirin, or corticosteroids
✅ Elderly patients and those with ulcers or previous GI bleeding are at even greater risk
- Serotonin in the Brain (CNS) – Mood & Behavior
Serotonin is best known for its role in mood regulation, but it also affects cognition, sleep, and appetite.
🔹 Effects in the CNS:
✅ Mood Regulation – Low serotonin is linked to depression, anxiety, and irritability.
✅ Sleep-Wake Cycle – Serotonin is a precursor to melatonin, regulating sleep.
✅ Appetite Control – Helps regulate hunger and satiety (feeling full).
✅ Pain Perception – Modulates pain sensitivity, particularly in chronic pain conditions.
✅ Cognitive Function – Influences memory, learning, and decision-making.
- Serotonin in the Gut (Enteric Nervous System) – Digestion & Nausea
Surprisingly, 90% of the body’s serotonin is in the gut, not the brain!
🔹 Effects in the GI Tract:
✅ Motility – Stimulates intestinal movement (peristalsis) to push food through the digestive system.
✅ Nausea & Vomiting – Overactivation (e.g., from chemotherapy) triggers nausea by acting on the vagus nerve.
✅ Irritable Bowel Syndrome (IBS) – Abnormal serotonin signaling is linked to diarrhea or constipation.
- Serotonin in the Blood (Platelets & Vascular System) – Clotting & Blood Pressure
Platelets store serotonin and release it when a blood vessel is damaged.
🔹 Effects in the Blood & Cardiovascular System:
✅ Vasoconstriction (Narrowing of Blood Vessels) – Helps regulate blood pressure.
✅ Platelet Aggregation – Assists in blood clotting.
✅ Cardiac Function – Serotonin receptors in the heart can affect heart rate and rhythm.
Key Clinical Points:
SSRIs block serotonin reuptake, increasing serotonin in the brain → used for depression and anxiety.
Too much serotonin (Serotonin Syndrome) can cause agitation, tremors, fever, and life-threatening hyperactivity of the nervous system.
Serotonin in the gut explains why SSRIs cause nausea and diarrhea as side effects.
Serotonin in platelets explains why SSRIs increase the risk of GI bleeding.
Norepinephrine (noradrenaline):
Affects alertness, arousal, and stress response.
Epinephrine (adrenaline):
Involved in the fight-or-flight response, increases heart rate and blood flow to muscles.
Glutamate:
Acts as the primary excitatory neurotransmitter, involved in learning and memory.
Gamma-aminobutyric acid (GABA):
Acts as the primary inhibitory neurotransmitter, regulates anxiety and stress.
Endorphins:
Natural painkillers and mood enhancers, released during exercise and other pleasurable activities.
Histamine:
Involved in immune response, allergic reactions, and regulation of sleep-wake cycles.
Oxytocin:
Regulates social bonding, trust, and emotional responses.
Adenosine:
Regulates sleep and wakefulness, involved in relaxation
Nitric Oxide:
Involved in vasodilation and neurotransmission in the brain.
What are nuerotransmitters
Neurotransmitters are chemical messengers that transmit signals across synapses in the nervous system
Neuropeptide Y (NPY):
Regulates appetite, stress response, and cardiovascular function.
Substance P:
Involved in pain perception and inflammatory processes.
Neurotensin:
Modulates neurotransmission, appetite, and stress responses.
Enkephalins:
Endogenous opioids that regulate pain perception and mood.
Dynorphins:
Another group of endogenous opioids involved in pain modulation.
Anandamide:
A type of endocannabinoid neurotransmitter involved in mood regulation and pain perception.
Vasopressin (antidiuretic hormone):
Regulates water retention and blood pressure, also involved in social behavior and stress response.
Orexin (Hypocretin):
Regulates wakefulness, appetite, and energy expenditure
Neuromodulin:
A calcium-binding protein that modulates neurotransmitter release and synaptic plasticity.
Cholecystokinin (CCK):
Involved in digestion, satiety, and anxiety regulation
Functions
Acetylcholine:
Nicotinic in muscle cells uses sodium channels
Excitatory muscarinic used in brain for cognition and memory
Excitatory and inhibitory used in autonomic nervous system
Gaba-inhibitory in CNS (intracranial)
Glycine=inhibitory in spinal cord- via strychnine receptors
Glutamate- most common excitatory NT in CNS (learning and memory through NMDA)
Norepinephrine – focus on excitatory
-role in autonomic nervous system, and limbic and cortical functions
Serotonin: 5HT1 receptor in mood disorders
What amino acids are needed to make Serotonin, Dopamine and GABA.
Serotonin: Tryptophan also helps make Vitamin B3
- A way to remember it end with -N; niaciN tryptophaN
Dopamine: Tyrosine
- A way to remember it rhymes Dopamine and Tyrosine
GABA: Glutamate
What is a Monoamine?
A monoamine is a type of neurotransmitter that has one amine (-NHâ‚‚) group connected to an aromatic ring. These neurotransmitters play a major role in mood, cognition, and autonomic functions.
Examples of Monoamines:
Serotonin (5-HT) → Regulates mood, sleep, appetite.
Dopamine (DA) → Involved in reward, motivation, movement.
Norepinephrine (NE) → Controls alertness, stress response, blood pressure.
Epinephrine (Adrenaline) → Fight-or-flight hormone.
Histamine → Involved in wakefulness, immune response, and stomach acid regulation.
💡 Monoamine oxidase (MAO) is the enzyme that breaks down monoamines, which is why Monoamine Oxidase Inhibitors (MAOIs) prevent their breakdown, increasing neurotransmitter levels.
