PSYCH04X Neurotransmitters, Neuropeptides, and Hormones

Neurotransmitters

The chemicals released by neurons that affects another neuron.

Amino Acid

Glutamate, GABA, Glycerin, Aspartate

Modified Amino Acid

Acetylcholine

Monoamines

Indolamines: Serotonin
Catecholamines: Dopamine, Norepinephrine, Epinephrine

Neuropeptides

Endorphins, Substance P, Neuropeptide Y

Purines

ATP, Adenosine

Gases

Nitric Oxide

Acetylcholine (ACh)

• Location: Brain, Spinal Cord, PNC (especially some organs of the parasympathetic nervous system)

• Effects: Excitatory in brain and autonomic nervous system; inhibitory elsewhere

• Function: Enables muscle action, learning, and memory. Muscle movement, cognitive functioning

• Malfunction: Alzheimer’s Disease, ACh-producing neurons deteriorate

Dopamine

• Location: Brain and Spinal Cord

• Effects: Excitatory

• Function: Muscle disorders, mental disorders, Parkinson’s diseases. Influences movement, learning, attention, and emotion.

• Malfunction: Oversupply linked to schizophrenia. Undersupply linked to tremors and decreased mobility in Parkinson’s disease.

Serotonin

• Location: Brain and Spinal Cord

• Effects: Inhibitory

• Function: Sleeping, eating, mood, pain, depression. Affects mood, hunger, sleep, and arousal.

• Malfunction: Undersupply linked to depression. Some antidepressant drugs raise serotonin levels.

Norepinephrine

• Function: Helps control alertness and arousal

• Malfunction: Undersupply can depress mood.

Gamma-aminobutyric Acid (GABA)

• Location: Brain and Spinal Cord

• Effects: Main inhibitory neurotransmitter

• Functions: Eating, aggression, sleeping. A major inhibitory neurotransmitter.

• Malfunctions: Undersupply linked to seizures, tremors, and insomnia.

Glutamate

• Location: Brain and Spinal Cord

• Effects: Excitatory

• Function: Memory. A major excitatory neurotransmitter; involved in memory.

• Malfunction: Oversupply can overstimulate the brain, producing migraines or seizures (which is why some people avoid MSG, monosodium glutamate, in food)

Synthesis of Transmitters

Neurons synthesize nearly all neurotransmitters from amino acids.

Acetylcholine

Synthesized from choline which is abundant in milk, eggs, and peanuts.

Phenylalanine and Tyrosine

Present in protein, are precursor of dopamine, norepinephrine, and epinephrine.

Tryptophan

The precursor in serotonin, crosses the blood-brain barrier by a special transport system that it shares with other large amino acids.

Levo-dopa or L-dopa

Precursor to dopamine helps increase the supply of dopamine.

Neuropeptides

• Neuromodulators

• Chemicals released by the dendrites, cell body, and by the sides of axons

• Resembles hormones wherein they diffuse widely, slowly affecting many neurons in their region of the brain.

Vasopressin

• Neuropeptide

• Important for liquid intake

Oxytocin

• Love hormone

• Physical contact with someone

Place synthesized

Neuropeptides: Cell body
Neurotransmitters: Presynaptic Terminal

Place released

Neuropeptides: Dendrites, cell body, and sides of axon
Neurotransmitter: Axon Terminal

Released by

Neuropeptide: Repeated depolarization
Neurotransmitter: Single action potential

Effect on other cells

Neuropeptides: Release of neuropeptides
Neurotransmitters: No effect

Spread of effects

Neuropeptides: Diffuse to wide areas
Neurotransmitters: Effects mostly on receptors

Duration of effects

Neuropeptides: Minutes
Neurotransmitters: Milliseconds to seconds

Hallucinogenic drugs

Drugs that distort people’s perception. Chemically resemble serotonin. Provide stimulation at inappropriate times or for longer than usual durations.

Nicotine

Stimulates a family of acetylcholine receptors aka “nicotine receptors”

Opiate drugs

Includes morphine, heroine, and methadone. Opiates relieve pain by acting on receptors in the brain as well as the skin.

Hormones

• Resemble synaptic transmission in many ways.

• Chemicals secreted by cells in one part of the body and conveyed by the blood to influence other cells.

• The hypothalamus in the brain controls the release of hormones in the pituitary gland.

Hormones

• Found in both plant and animals

• Belong to the endocrine system

• Polypeptides, amines, terpenoids, steroids, or phenolic compounds

• Produced in endocrine glands and are secreted into the blood stream

• Transmitted through blood

• Act on a distant site from where it is produced

• Take few minutes to few days to respond

• Diverse functions in controlling growth, development, and reproduction

• Capable of regulating target organs or tissues

• Oxytocin, Cortisol, Testosterone, Estrogen (in animals)

• Abscisic Acid, cytokines, and gibberellins (in plants)

Neurotransmitters

• Found only in animals

• Belong to the nervous system

• Proteins, amino acids, or gases

• Released by presynaptic nerve terminal into the synapse

• Transmitted across the synaptic cleft

• In direct apposition to their target cells

• Quickly respond, usually within milliseconds

• Involved in the transmission of nerve signals

• Only stimulate the postsynaptic neurons

• Serotonin, Dopamine, Norepinephrine, Epinephrine, Glutamate, Aspartate, Glycerin, Nitrogen oxide, and Carbon monoxide