Neurons and Their Structure

Neurons and Their Structure

• Neurons serve as the fundamental units of the nervous system, composed of dendrites, cell body (soma), axon, and terminal buttons.
• Dendrites are extensions that receive signals from other neurons, enabling synaptic connections.
• The cell body, containing the nucleus, sustains cell function.
• Axons are long, wirelike structures transmitting signals away from the cell body, ending in terminal buttons.
• Myelin sheath is a fatty layer around axons that accelerates neural signal transmission.

Supporting Cells

• Glial cells support, nourish, and protect neurons in the nervous system, playing vital roles in maintaining overall brain health.

Neurotransmission

• A synapse is the gap between terminal buttons of one neuron and dendrites of another, where neurotransmitters are released to facilitate communication.
• Receptor sites on dendrites are specialized for specific neurotransmitters, influencing neuronal firing.

Neural Processes

• Resting potential refers to the neuron's negatively charged state when inactive, while action potential is a brief electrical charge that propagates along the axon upon reaching the threshold.
• Neural firing is an electrochemical process involving electrical signals within neurons and chemical neurotransmitters between them.

Principles of Neural Activity

• The all-or-none principle states that a neuron either fully fires or does not fire at all when the threshold is met.
• After firing, neurons enter a refractory period where they cannot immediately fire again until they return to resting potential.
• Reuptake is the process where a neurotransmitter is reabsorbed by the original neuron after signal transmission.

Types of Neurotransmitters

• Neurotransmitters are chemical messengers that cross synaptic gaps, binding to receptor sites on the next neuron to influence neural impulses.
• Excitatory neurotransmitters stimulate the next neuron to fire, while inhibitory neurotransmitters prevent it from firing.

Specific Neurotransmitters and Their Functions

• Acetylcholine: Involved in motor movement, learning, and memory; its deficiency links to Alzheimer's disease.
• Dopamine: Regulates motor movement, alertness, and emotions; imbalances affect conditions like Parkinson's disease and schizophrenia.
• Endorphins: Act as natural painkillers and influence pleasure; connected to addiction mechanisms.
• Serotonin: Regulates mood, hunger, sleep, and arousal; low levels are associated with depression.
• Norepinephrine: Plays a role in alertness and arousal, affecting mood; part of the body's stress response.
• GABA: Major inhibitory neurotransmitter; deficiencies can lead to seizures and insomnia.
• Glutamate: Principal excitatory neurotransmitter; excess can lead to overstimulation, migraines, or seizures.

Drug Interactions with Neurotransmitters

• Agonists: Molecules that enhance or mimic the effect of neurotransmitters, promoting a physiological response.
• Antagonists: Molecules that inhibit or block neurotransmitter action, diminishing or preventing a physiological response.