Neurotransmitters and Mental Health

Prayer Request

• A prayer request was given, asking Allah to make learning beneficial and to increase knowledge.

Learning Objectives

• Students will be able to define neurotransmitters.
• Students will be able to list types of neurotransmitter receptors.
• Students will be able to classify neurotransmitters by function and chemistry.
• Students will be able to identify sites of neurotransmitters in the brain.
• Students will be able to explain the implications of neurotransmitter imbalance on mental health.
• Students will be able to list diagnostic methods for neurotransmitter imbalance.

Neurotransmitter Definition

• The criteria for a substance to be considered a neurotransmitter are:
  • The substance must be present within the presynaptic neuron.
  • The substance must be released in response to presynaptic depolarization, and the release must be calcium-dependent.
  • Specific receptors for the substance must be present on the postsynaptic cell.

Neurotransmitter Action Localization

• Neurotransmitters act either locally or more diffusely.
  • Local action involves altering the excitability of a single or a few postsynaptic cells.
  • Diffuse action involves long axons that locally release neurotransmitters onto distant targets.

Classification of Neurotransmitters

• Neurotransmitters can be classified as excitatory or inhibitory.
  • Examples of excitatory neurotransmitters include glutamate, acetylcholine, histamine, dopamine, norepinephrine, and epinephrine.
  • Examples of inhibitory neurotransmitters include GABA and serotonin.
  • Dopamine is both excitatory and inhibitory.

Neurotransmitter Receptors

• Whether a neurotransmitter is excitatory or inhibitory depends on the receptor type it acts on.
• Inhibitory postsynaptic potential decreases firing and propagation of the action potential due to chloride ion influx.
• Neurotransmitter receptors include ionotropic and G-protein-coupled receptors.

Types of Receptors Detailed

• Ionotropic Receptors (Ligand-Activated Ion Channels):
  • Allow ions (sodium, potassium, or calcium) to pass through.
  • Act quickly.
  • Example: NMDA receptors, involved in learning and memory.
  • Example: AMPA receptors, mediate fast excitatory transmission.
• G-Protein-Coupled Receptors:
  • Activate intracellular signaling pathways via G-proteins.
  • Lead to changes in gene expression, enzyme activity, or ion channel behavior.
  • Slower but have longer-lasting effects.
  • Example: Dopamine D2 receptors, associated with reward and motivation.
  • Example: Acetylcholine receptors (muscarinic), found in the heart and brain.
  • Example: GABA receptors (GABA-B), modulate neuronal activity.
  • Example: Serotonin receptors (5-HT1A), related to anxiety and depression.

Neurotransmitter Examples

• Acetylcholine (ACh):

  • Excitatory (usually), except in the heart (inhibitory).
  • Released from motor neurons.
  • Regulates sleep cycle and muscle functioning.

• Norepinephrine:

• Epinephrine:

  • Excitatory.
  • Released from chromaffin cells.
  • Responsible for the "fight-or-flight" response.

• Dopamine:

  • Both excitatory and inhibitory.
  • Released from the substantia nigra.
  • Inhibits unnecessary movements, inhibits prolactin, and stimulates growth hormone.

• Gamma-Aminobutyric acid (GABA):

  • Inhibitory.
  • Released from various brain regions.
  • Reduces neuronal excitability.

• Glutamate (Glu):

  • Excitatory.
  • Released from sensory neurons and the cerebral cortex.
  • Regulates central nervous system excitability, learning, and memory.

• Serotonin (5-HT):

  • Inhibitory.
  • Released from brain stem neurons and other locations.
  • Regulates body temperature, pain, emotions, and the sleep cycle.

• Histamine:

  • Excitatory.
  • Released from various sites (hypothalamus, stomach cells, etc.).
  • Regulates wakefulness, blood pressure, pain, sexual behavior, and inflammatory responses.

Neuromodulators

• Neuromodulation differs from neurotransmission by the duration of action at the synapse.
• Neuromodulators spend a significant time in cerebrospinal fluid modulating the activity of many neurons.
• Examples of neuromodulators are dopamine, serotonin, acetylcholine, histamine, and norepinephrine.

Neurotransmitter Imbalance-Related Disorders

• Related disorders include Alzheimer's disease, depression, schizophrenia, Parkinson's disease, epilepsy, Huntington's disease, and myasthenia gravis.

Diagnosis of Neurotransmitter Imbalance

• Identifying causes and symptoms.
• Diagnostic tests.
  • Neurotransmitter testing, often analyzed from urine samples.
  • Brain scans.
  • Brain tissue assays.

Summary of Neurotransmitters

• Neurotransmitters are small molecule transmitters and neuropeptides.
• Primarily biogenic amines that modulate ongoing activity in the brain and peripheral tissues in a gradual manner.
• Drugs influencing transmitter actions are crucial in treating neurological and mental health disorders.

This quiz focuses on the essential concepts of neurotransmitters, including their definitions, types, and roles in mental health. Students will explore neurotransmitter classification, receptor types, and implications of imbalances. Gain insights into diagnostic methods and the impact of neurotransmitters on brain functions.