Synapses & Neurotransmitters (Level 4)

Summary

This session focuses on synapses, where neurotransmitters enable neurons to connect and transmit signals. It explains the action potential, the role of calcium in releasing neurotransmitters, and how they bind to receptors on postsynaptic neurons. Various neurotransmitters like acetylcholine, noradrenaline, dopamine, serotonin, and GABA are discussed, highlighting their unique roles in functions like memory, mood, movement, and inhibition. The video emphasizes the specificity of neurotransmitter-receptor binding, the lock-and-key hypothesis, and the effects of neurotransmitter imbalances on health and behavior.

Takeaways

• 🧠 Synapses are the junctions between neurons where neurotransmitters facilitate the transmission of signals.
• ⚡️ Action potentials travel along axons, leading to the release of neurotransmitters when calcium enters the neuron at the terminal.
• 🧪 Neurotransmitters bind to receptors on the postsynaptic neuron, causing either excitatory or inhibitory effects.
• 💡 Each neuron receives thousands of synaptic inputs and must process whether to fire or not based on these excitatory and inhibitory signals.
• 🔑 Neurotransmitters follow the 'lock and key' hypothesis, binding only to specific receptors, with some neurotransmitters having multiple receptor subtypes.
• 🧬 Acetylcholine, the first discovered neurotransmitter, plays a role in muscle contraction and memory formation, and has both excitatory and inhibitory effects depending on the receptor type.
• 🏃‍♂️ Noradrenaline (norepinephrine) is involved in emergency responses, boosting attention, mood, and controlling the sleep-wake cycle.
• 🎯 Dopamine is key for movement, memory, and motivation, with different pathways affecting various brain functions. It plays a role in pleasure, Parkinson's disease, and attention.
• 😴 Serotonin, derived from dietary tryptophan, regulates mood, sleep, feeding, and sensory perception. It is linked to depression, anxiety, and the effects of psychedelic drugs.
• 🚫 GABA is an inhibitory neurotransmitter that regulates brain activity and prevents excessive firing, linked to conditions like epilepsy and influenced by substances like alcohol and tranquilizers.

Q & A

What is a synapse and what role does it play in neuronal communication?

A synapse is the junction between two neurons where the transmission of signals occurs. It allows one neuron to pass its signal to the next neuron through the release of neurotransmitters.

What happens when an action potential reaches the end of a neuron?

When an action potential reaches the end of a neuron, calcium ions enter the cell, triggering the release of neurotransmitters from vesicles into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron.

What are neurotransmitters, and how do they function?

Neurotransmitters are chemicals released by neurons to transmit signals to other neurons across the synapse. They bind to specific receptors on the postsynaptic neuron, causing a change in the electrical potential, which can either excite or inhibit the neuron.

How do neurons determine whether to fire an action potential?

Neurons receive inputs from multiple synapses, some excitatory and some inhibitory. They sum these signals and determine whether the overall input is strong enough to trigger an action potential.

What is the 'lock and key hypothesis' in neurotransmitter function?

The 'lock and key hypothesis' states that each neurotransmitter can only bind to specific receptors that match its chemical structure, much like how a key fits into a specific lock. For example, acetylcholine binds only to acetylcholine receptors.

How does acetylcholine affect different parts of the body?

Acetylcholine has different effects depending on the receptor it binds to. In skeletal muscles, it has an excitatory effect, causing muscle contraction. In the heart, it has an inhibitory effect, slowing the heart rate.

What are the main functions of dopamine in the brain?

Dopamine is involved in movement, memory, and motivation. It helps regulate movement, learning, attention, and reward systems in the brain. Low dopamine levels are associated with Parkinson's disease.

What is the role of serotonin in the body?

Serotonin regulates various functions, including mood, temperature, sleep, feeding, and sensory perception. It is also linked to conditions such as depression, anxiety, and migraines.

How is GABA different from other neurotransmitters, and what is its primary function?

GABA (gamma-aminobutyric acid) is primarily an inhibitory neurotransmitter, meaning it reduces neuronal activity and helps prevent overstimulation. It plays a critical role in controlling seizures and is affected by tranquilizers and alcohol.

What is the relationship between tryptophan and serotonin?

Serotonin is derived from tryptophan, an amino acid obtained from the diet. Low levels of tryptophan can lead to reduced serotonin production, which is linked to mood disorders like depression.