Chapter 4 & 5: The Chemistry of Behavior and Hormones

Vocabulary flashcards covering basic pharmacology, neurotransmitter pathways, receptor classifications, psychotropic medications, and endocrine systems from Chapters 4 and 5.

Endogenous

Molecules or processes that occur naturally within the body.

Exogenous

Molecules originating from outside the body (such as drugs or toxins) used to alter physiology and behavior.

Receptor Agonist

A ligand that mimics the effects of a neurotransmitter, having high affinity and activating the receptor to produce a biological effect.

Receptor Antagonist

A ligand that binds to a receptor without activating it, blocking active ligands from binding and producing no cellular effect.

Competitive Ligand

A drug or substance that acts as an agonist, antagonist, or inverse agonist by binding directly to the primary transmitter site.

Noncompetitive Ligand (Neuromodulator)

A substance that binds to a separate modulatory site on a receptor rather than the primary transmitter-binding site.

Amino Acid Neurotransmitters

A class of small organic molecules that includes Glutamate, Glycine, and GABA.

Amine Neurotransmitters

A class of small organic molecules that includes Acetylcholine (ACh), Dopamine, Norepinephrine, Serotonin, and Histamine.

Peptide Neurotransmitters

Short amino acid chains stored in and released from secretory granules at the axon terminal, such as Dynorphin, Enkephalins, and Somatostatin.

Criteria for Neurotransmitter Classification

1. Presynaptic synthesis and storage; 2. Depolarization-induced release dependent on $Ca^{2+}$; 3. Presence of specific postsynaptic receptors; 4. A specific mechanism to terminate the signal.

Glutamate

The most prevalent excitatory neurotransmitter in the brain.

GABA

The primary inhibitory neurotransmitter in the central nervous system.

Acetylcholine (ACh) Projection Pathways

Originates in the basal forebrain (septal nucleus, nucleus basalis) and midbrain tegmental nuclei, projecting to the forebrain (hippocampus, limbic system, cerebral cortex) and midbrain/thalamus.

Nigrostriatal (Mesostriatal) Pathway

A dopamine pathway originating in the substantia nigra and projecting to the striatum (caudate nucleus and putamen), primarily involved in motor control.

Mesolimbic Pathway

A dopamine pathway originating in the ventral tegmental area (VTA) and projecting to the nucleus accumbens and amygdala, involved in reward, reinforcement, emotion, and addiction.

Mesocortical Pathway

A dopamine pathway originating in the ventral tegmental area (VTA) and projecting to the prefrontal cortex, involved in short-term memory, planning, strategy, and problem-solving.

Tuberoinfundibular Pathway

A dopamine pathway originating in the hypothalamus and projecting to the pituitary gland, involved in hormonal regulation, maternal behavior, pregnancy, and sensory processes.

Norepinephrine (NE) System

Originates in the locus coeruleus and lateral tegmental area, projecting to the cortex, basal ganglia, hippocampus, hypothalamus, and spinal cord to modulate mood, arousal, sexual behavior, analgesia, and fight-or-flight responses.

Serotonin (5-HT) System

Originates in the raphe nuclei of the brainstem, projecting widely to mediate mood, anxiety, appetite, sleep, and pain/spinal reflexes.

Nicotinic Receptors

Ionotropic, mostly excitatory acetylcholine receptors found at neuromuscular junctions; stimulated by nicotine and blocked by curare.

Muscarinic Receptors

Metabotropic (G protein-coupled) acetylcholine receptors that produce slower excitatory or inhibitory responses and are blocked by atropine and scopolamine.

Ionotropic Glutamate Receptor Subtypes

AMPA (passes $Na^+$, $K^+$), NMDA (passes $Na^+$, $K^+$, $Ca^{2+}$), and Kainate (passes $Na^+$, $K^+$); all produce excitatory postsynaptic potentials (EPSPs).

$GABA_A$ Receptor

A fast, ionotropic chloride ($Cl^-$) channel containing binding sites for GABA, benzodiazepines, barbiturates/alcohol, picrotoxin, and steroids/neurosteroids.

Neuromuscular Junction

A chemical synapse between a motor neuron and a muscle fiber where ACh binding allows $Na^+$ influx, generating an end-plate potential that triggers muscle contraction.

Catecholamines

A group of monoamines sharing a catechol and amine group, consisting of Dopamine, Norepinephrine, and Epinephrine.

Parkinson's Disease

A movement disorder marked by tremors, rigidity, and a shuffling gait, caused by the progressive loss of dopaminergic neurons in the substantia nigra of the nigrostriatal pathway.

Affinity

The degree of chemical attraction or binding strength between a ligand and a receptor.

Efficacy

The capacity of a bound ligand to activate a receptor and trigger an intracellular biological response.

Caffeine

An exogenous neuromodulator that induces arousal by blocking endogenous adenosine receptors, disinhibiting catecholamine release.

Typical Antipsychotics

First-generation neuroleptics that act as selective dopamine $D_2$ receptor antagonists.

Atypical Antipsychotics

Antipsychotics that block dopamine receptors along with specific serotonin receptors, reducing negative symptoms.

Monoamine Oxidase (MAO) Inhibitors

Antidepressants that inhibit the MAO enzyme, preventing the synaptic enzymatic breakdown of monoamine neurotransmitters.

Tricyclic Antidepressants

Antidepressants that elevate synaptic levels of norepinephrine and serotonin by blocking their presynaptic reuptake.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressants (such as Prozac and Zoloft) that selectively inhibit the reuptake of serotonin into presynaptic terminals.

Endocannabinoids

Endogenous retrograde messengers (e.g., anandamide/AEA and 2-AG) synthesized postsynaptically that travel backward to presynaptic $CB_1$ or $CB_2$ receptors to regulate transmitter release.

Cocaethylene

A psychoactive compound formed in the body when cocaine and alcohol are consumed together, contributing to dual dependence.

Disease Model of Addiction

The view that addiction is characterized by underlying brain alterations requiring medical treatment rather than moral punishment.

Varenicline (Chantix)

An $\alpha_4\beta_2$ partial nicotinic acetylcholine receptor agonist utilized for smoking cessation.

Pineal Gland

An endocrine gland that secretes melatonin to regulate sleep-wake cycles and reproductive/seasonal rhythms.

Posterior Pituitary Hormones

Oxytocin (mediates uterine contractions, milk letdown, and social bonding) and Vasopressin (AVP/ADH; maintains water balance, blood pressure, and inhibits urine formation).

Anterior Pituitary Hormones

Hormones including ACTH, TSH, FSH, LH, Prolactin, and Growth Hormone (GH), which regulate other endocrine glands, growth, metabolism, lactation, and reproduction.

Thyroid Gland

An endocrine gland releasing thyroxine ($T_3$, $T_4$) to regulate metabolism and calcitonin to inhibit bone calcium release.

Parathyroid Glands

Endocrine glands that secrete parathyroid hormone to stimulate the release of calcium from bones.

Adrenal Cortex

The outer 80% of the adrenal gland; secretes glucocorticoids (cortisol) for stress responses and glucose metabolism, and aldosterone for sodium regulation.

Adrenal Medulla

The inner 20% of the adrenal gland; secretes epinephrine and norepinephrine to facilitate the fight-or-flight response and emotional arousal.

Pancreatic Islet Cells

Endocrine cells that release insulin (to lower blood glucose) and glucagon (to elevate blood glucose).

Endocrine vs. Synaptic Communication

Endocrine signaling releases hormones into the bloodstream to reach distributed targets with specific receptors, whereas synaptic signaling transmits neurotransmitters across a narrow synaptic cleft to an adjacent target cell.

Psychosocial Dwarfism

A developmental growth failure resulting from severe early life stress, which suppresses growth factors such as somatomedins.

Goiter

An enlargement of the thyroid gland typically caused by a dietary iodine deficiency.

Hypothalamic-Pituitary-Adrenal (HPA) Axis

A neuroendocrine stress pathway: Stress triggers hypothalamic CRH release, which induces anterior pituitary ACTH secretion, stimulating adrenal cortical cortisol release.