Neurons, Synapses, and Neurotransmission (Lecture Video Notes)

A comprehensive set of Q&A flashcards covering neuron structure, signaling, synapses, neurotransmitters, and the effects of psychoactive drugs based on the provided lecture notes.

What are the two interrelated processes of the electro-chemical system in the nervous system?

Electrical changes within neurons (impulse/firing) and chemical signals between neurons.

Which system is faster and more local: Nervous system or Endocrine system?

The nervous system; its impulses travel up to ~200 mph and target precise sites, whereas the endocrine system is slower and broadcasts signals throughout the body.

What are the CNS and PNS?

CNS = brain and spinal cord (does not regenerate well); PNS = all other nerves (can regrow).

What is the difference between the Somatic and Autonomic nervous systems?

Somatic transmits information from the outside world and controls voluntary motor output; Autonomic regulates internal organs and glands and operates largely automatically.

What are the two parts of the Autonomic nervous system and their general roles?

Parasympathetic: calming, energy conservation; Sympathetic: arousing, energy release.

What is the basic unit of the nervous system and how many are in the CNS?

Neuron; about 100 billion neurons in the CNS.

What are glial cells and why are they important?

Supporting cells that outnumber neurons; they help form the blood-brain barrier, make myelin, maintain the intracellular environment, form scar tissue, aid in neuron migration, and more.

What is the role of the myelin sheath and what are the Nodes of Ranvier?

Myelin wraps and speeds transmission around axons; Nodes of Ranvier are gaps where the action potential jumps (saltatory conduction) to speed signaling.

What is the axon and what factors influence its conduction speed?

The axon is the neuron’s outgoing branch; speed increases with larger diameter, length, and presence of myelin; conduction can be up to ~3 feet+ or more in length for some neurons.

What are dendrites and the dendritic bush?

Dendrites receive information from other neurons or the outside world; the dendritic bush is the branching region; dendrites have many receptor sites and can form thousands of connections.

What is the soma and its function in a neuron?

(cell body) keeps the cell alive, contains DNA, and contributes to regeneration; it is not the primary conductor of signals like the axon.

What are the three neuron types and their roles?

Sensory (afferent): brings info into the CNS; Motor: controls muscles; Interneurons: connect sensory and motor neurons.

What is a reflex arc?

The fastest neural response pathway: sensory neuron → interneuron → motor neuron.

What is the blood-brain barrier and what passes through it easily?

A barrier around brain blood vessels that protects the brain; passes oxygen, carbon dioxide, glucose, amino acids, and some psychoactive drugs; large molecules are blocked.

Which substances commonly pass the blood-brain barrier?

Oxygen, carbon dioxide, glucose, amino acids, and some psychoactive drugs.

Outline the neurotransmitter life cycle.

Synthesis → transport/storage → release/diffusion → inactivation/reuptake.

Where are larger neurotransmitters vs smaller neurotransmitters synthesized?

Larger NTs are synthesized in the soma and transported to axonal terminals; smaller NTs are synthesized in the axon terminals.

Where are neurotransmitters stored and what triggers their release?

Stored in synaptic vesicles; action potentials cause vesicles to fuse with the presynaptic membrane and release NTs via exocytosis, triggered by calcium.

What is the lock-and-key concept in neurotransmission?

NTs bind to specific receptor sites on the postsynaptic neuron; most NTs have multiple receptor types.

What are the two main receptor types and their effects?

Ionotropic receptors open ion gates directly (fast, <10 ms); Metabotropic receptors activate G proteins and second messengers (slower but longer-lasting).

What second messenger is commonly produced in metabotropic signaling and which enzyme is involved?

cAMP produced by Adenylyl Cyclase; Phosphodiesterase breaks down cAMP.

What are excitatory and inhibitory outcomes when NTs dock at receptors?

Excitatory docking opens Na+ gates (depolarizes); Inhibitory docking opens Cl– gates (hyperpolarizes).

Name the major categories and example neurotransmitters.

Amino acids (Glutamate—excitatory; GABA—inhibitory); Acetylcholine (memory/learning/movement; neuromuscular junction); Monoamines (Serotonin, Dopamine, Epinephrine, Norepinephrine); Peptides (Substance P, Endorphins).

What is acetylcholine (ACh) and its roles?

Involved in memory, learning, and movement; neuromuscular junction; can modulate dopamine levels; nicotine affects muscarinic receptors.

What are monoamines and which NTs fall into this group?

A group including Serotonin, Dopamine, Epinephrine, and Norepinephrine; all affect mood, arousal, and other functions.

What are peptide neurotransmitters and give examples?

Chains of amino acids; Substance P (pain signaling) and Endorphins (natural opioids).

How do psychoactive drugs affect synapses (agonists vs antagonists)?

Agonists increase activity: boost synthesis or release, mimic NT, block reuptake. Antagonists decrease activity: reduce synthesis or release, block receptors, or prevent release.

Give pre-synaptic example effects (increasing or altering NT activity).

L-dopa increases dopamine synthesis; Botulinum toxin reduces ACh release; Black widow venom causes continuous ACh release.

Give post-synaptic example effects (agonists/antagonists).

Agonists: Cocaine/Amphetamines/Ritalin increase dopamine; Opiates mimic endorphins; Antagonists: Atropine blocks muscarinic ACh receptors; Curare blocks nicotinic ACh receptors; LSD affects serotonin receptors.

What are reuptake inhibitors and give examples?

Drugs that block reuptake to keep NTs in the synapse longer; examples include SSRIs (serotonin), Dopamine RIs (cocaine, methylphenidate), Norepinephrine RIs.

What are the key features of an action potential (resting, threshold, peak, and refractory periods)?

Resting potential around -70 mV (Na+/K+ distribution with Na+ outside, K+ inside); Sodium-potassium pump maintains gradient; Threshold around -55 mV triggers firing; Peak around +25 mV; Refractory period (hyperpolarization to ~-95 mV) prevents immediate re-firing.

What is saltatory conduction and why is it faster?

In myelinated axons, the action potential jumps between Nodes of Ranvier, speeding transmission by roughly 50–100x.

Why does the nerve impulse not travel directly down the axon and how is it regenerated?

The impulse is regenerated at successive nodes along the axon via depolarization, aided by the sodium-potassium pump and local ion flow.