Overview
This lecture explains how the chemistry of neurons and hormones affects thoughts, feelings, and behaviors, emphasizing that everything psychological is also biological.
Nervous System Basics
- The nervous system influences thoughts, emotions, and actions through complex chemical processes.
- Neurons (nerve cells) are the basic building blocks of the nervous system, transmitting electrochemical messages.
- Each neuron has three main parts: soma (cell body), dendrites (receivers), and axon (transmitter).
- The myelin sheath is a fatty layer around some axons that speeds up message transmission; its degradation leads to diseases like multiple sclerosis.
- Neurons communicate across synapses, small gaps between neurons, using neurotransmitters.
Neurotransmitters and Communication
- Neurotransmitters are chemical messengers that cross synaptic gaps to excite or inhibit other neurons.
- After transmitting messages, neurotransmitters are reabsorbed by the releasing neuron through reuptake.
- Excitatory neurotransmitters increase the likelihood of the next neuron firing (e.g., norepinephrine, glutamate).
- Inhibitory neurotransmitters decrease neuron firing likelihood (e.g., GABA, serotonin).
- Some neurotransmitters, such as acetylcholine and dopamine, can be either excitatory or inhibitory.
- Dopamine is linked to movement, learning, emotion, and excessive amounts can contribute to schizophrenia and addiction.
- Acetylcholine is essential for muscle action and memory; its deficit is linked to Alzheimer’s disease.
Endocrine System and Hormones
- The endocrine system consists of glands that release hormones into the bloodstream, affecting mood, metabolism, and growth.
- Hormones work slower than neurotransmitters but their effects last longer.
- Major glands include the adrenal glands (adrenaline for fight or flight), pancreas (insulin and glucagon for blood sugar), thyroid/parathyroid (metabolism, calcium), and sex glands (testosterone, estrogen).
- The pituitary gland is the "master gland," controlling other endocrine glands and releasing hormones like growth hormone and oxytocin.
- The hypothalamus in the brain controls the pituitary gland, creating a feedback loop with the nervous system.
Key Terms & Definitions
- Neuron — nerve cell that transmits messages in the nervous system.
- Soma — the cell body of a neuron.
- Dendrite — neuron extension that receives signals from other cells.
- Axon — long fiber that sends impulses outward from the neuron.
- Myelin Sheath — fatty tissue that insulates axons and speeds up transmission.
- Synapse — junction between two neurons.
- Neurotransmitter — chemical messenger crossing synapses between neurons.
- Reuptake — process of neurotransmitter reabsorption by the releasing neuron.
- Hormone — chemical messenger released by glands into the bloodstream.
- Pituitary Gland — master gland controlling hormone secretion.
- Endocrine System — system of glands producing hormones.
Action Items / Next Steps
- Prepare for next lesson on specific brain components and nervous system divisions.