1.3 The Neuron and Neural Firing
- Syllabus
- 2025
- Topic
- 1.3
- Level
- —
Learning objectives
1.3A—Explain how the structures and functions of typical neurons in the central nervous system affect behavior and…Explain how the structures and functions of typical neurons in the central nervous system affect behavior and mental processes.• Two common types of neural cells in the brain are neurons (neural cells that transmit information) and glial cells (cells that provide structure, insulation, communication, and waste transport). These types of cells form the basis of the nervous system and are the building blocks of all behavior and mental processes.• In the spinal cord, the reflex arc demonstrates how neurons within the central and peripheral nervous systems work together to respond to stimuli. Three types of neurons work together in the spinal cord to create a reflex arc: sensory neurons, motor neurons, and interneurons.1.3B—Explain how the basic process of neural transmission is related to behavior and mental processesExplain how the basic process of neural transmission is related to behavior and mental processes.• The process of neural transmission most commonly occurs in an orderly, systematic way and involves the all-or-none principle, depolarization, refractory period, resting potential, reuptake, and threshold. Disruptions to this process could lead to disorders such as multiple sclerosis or myasthenia gravis.- Exclusion: The sodiumpotassium pump is outside the scope of the AP Psychology Exam.• Each neurotransmitter has specific function(s) related to behavior and mental processes, which may depend on the neurotransmitter’s location in the nervous system. Neurotransmitters generally communicate either excitatory (making an action potential more likely) or inhibitory (making an action potential less likely) messages. Neurotransmitters related to behavior and mental processes for study in AP Psychology are limited to dopamine, serotonin, norepinephrine, glutamate, GABA, endorphins, substance p, and acetylcholine.- Exclusion: The AP Psychology Exam will only address the listed neurotransmitters in EK• Outside of the nervous system, hormones perform actions similar to neurotransmitters. Hormones related to behavior and mental processes for study in AP Psychology are limited to adrenaline, leptin, ghrelin, melatonin, and oxytocin.- Exclusion: The AP Psychology Exam will only address the listed hormones in EK Specific information about the glands of the endocrine system (with the exception of the pituitary gland as referenced in EK1.3C—Explain how psychoactive drugs affect behavior and mental processes. UNIT 1 Biological Bases of BehaviorExplain how psychoactive drugs affect behavior and mental processes. UNIT 1 Biological Bases of Behavior• Psychoactive drugs can influence neurotransmitter function in various ways throughout the neural communication process. Some act as agonists which encourage neural firing. Some act as antagonists which discourage neural firing. Some act as reuptake inhibitors which block the reabsorption of neurotransmitters back into the cell. UNIT 1 Biological Bases of Behavior• Psychoactive drugs have psychological and physiological effects.- i. Stimulants, such as caffeine and cocaine, typically cause increased neural activity.- ii. Depressants, such as alcohol, typically cause decreased neural activity.- iii. Hallucinogens, such as marijuana, typically cause distortions in perception and/or cognition.- iv. Opioids, such as heroin, typically act as pain relievers.• Psychoactive drug use can lead to tolerance and/or addiction. Addiction can create significant withdrawal symptoms if the psychoactive drugs are no longer consumed.
Neurons, Glia, and the Reflex Arc
Neurons transmit information; glial cells make that transmission possible by providing structure, insulation, communication support, and waste transport. Together they form the working cellular basis of behavior and mental processes: neurons carry messages, while glia maintain the conditions in which neural networks can function.
| Cell type | Main learning job |
|---|---|
| Neuron | Transmits information through the nervous system |
| Glial cell | Supports neural structure, insulation, communication, and waste transport |
A spinal reflex shows CNS and PNS neurons working as one pathway: (1) a sensory neuron carries information from a stimulus toward the spinal cord; (2) an interneuron in the spinal cord connects and processes the signal; (3) a motor neuron carries the response command toward the body. Because the spinal cord coordinates this pathway, a response can begin without waiting for deliberate conscious processing.
Do not treat glia as message-carrying neurons or the reflex as a single-neuron event. The learning point is coordinated function among sensory neurons, interneurons, motor neurons, and supporting glial cells.
From Threshold to Neural Message
Neural transmission follows an ordered cycle. A neuron begins at resting potential. If incoming stimulation reaches threshold, depolarization produces an action potential according to the all-or-none principle: the neuron fires fully rather than partially. A refractory period follows before the neuron can fire normally again. At the next cell, chemical messengers influence whether another action potential becomes more or less likely; reuptake removes released neurotransmitter back into the sending cell.
| Signal idea | Effect or distinction |
|---|---|
| Excitatory message | Makes an action potential more likely |
| Inhibitory message | Makes an action potential less likely |
| Neurotransmitter | Communicates within the nervous system; its function can depend on location |
| Hormone | Acts outside the nervous system in ways that can resemble neurotransmitter signaling |
AP Psychology limits neurotransmitters here to dopamine, serotonin, norepinephrine, glutamate, GABA, endorphins, substance P, and acetylcholine. The listed hormones are adrenaline, leptin, ghrelin, melatonin, and oxytocin. A disruption anywhere in transmission can change behavior or mental processes; multiple sclerosis and myasthenia gravis are examples linked to disrupted signaling.
Exam boundary: the sodium–potassium pump is outside scope. Detailed endocrine-gland information is also excluded here, except for the pituitary gland where Topic 1.4 explicitly includes it.
How Psychoactive Drugs Change Signaling
Psychoactive drugs change behavior and mental processes by altering neural communication. Their effects depend on where they intervene: they may encourage receptor activity, block it, or keep a neurotransmitter available for longer. A drug’s neural mechanism therefore leads to psychological and physiological consequences.
| Mechanism | Effect on communication |
|---|---|
| Agonist | Encourages neural firing |
| Antagonist | Discourages neural firing |
| Reuptake inhibitor | Blocks neurotransmitter reabsorption into the sending cell |
| Drug category | Typical effect | CED examples |
|---|---|---|
| Stimulant | Increased neural activity | Caffeine, cocaine |
| Depressant | Decreased neural activity | Alcohol |
| Hallucinogen | Distorted perception and/or cognition | Marijuana |
| Opioid | Pain relief | Heroin |
Repeated psychoactive-drug use can produce tolerance and/or addiction. If addiction develops, stopping use can produce significant withdrawal symptoms. Do not assume a category label describes every effect of every dose; the CED statements describe typical effects.