Neurotransmitters

Introduction

  • Neurotransmitters are chemicals which transmit signals from one neuron to the next across synapses

  • They are made in the cell body, then travel down the axon to the axon endings where they are stored

  • They are produced by pituitary and adrenal glands

Acetylcholine

  • First to be discovered in 1921

  • Excitatory:

    • Muscle stimulation, particularly the gastrointestinal system

    • Also play a role in REM sleep (dream stage)

  • People with Alzheimer’s Disease have about a 90% loss of acetylcholine in their brains

Norephinephrine

  • Excitatory:

    • Brings nervous system into high alert (fight or flight)

    • Associated with the Sympathetic nervous system, which increases heart rate and blood pressure

  • Stress depletes it while amphetamines cause it to be released

  • Can cause Generalized Anxiety Disorder, which is characterized by excessive worry that causes problems in daily life

Dopamine

  • Inhibitory:

    • Blocks neurons from firing

    • Associated with the reward system

    • Cocaine, opium, heroin, nicotine, and alcohol increase it

  • Schizophrenics have excessive amounts of dopamine

  • Too little dopamine cause Parkinson’s Disease

  • People with ADHD often have imbalances of dopamine and norephinephrine

Gamma Aminobutyric Acid (GABA)

  • Inhibitory:

    • Acts like a brake to the neurotransmitters that cause anxiety

  • Too little GABA can cause anxiety disorders

  • Epilepsy results if there is too little GABA

Glutamate

  • Excitatory:

    • Most common transmitter

    • Very important for memory

  • It is toxic to neurons and an excess of glutamate will kill them

  • ALS (Lous Gehrig’s Disease) results from excessive glutamate production

  • It is responsible for a large variety of diseases of the nervous system

Serotonin

  • Inhibitory:

    • Involved in emotion, mood, and perception

  • Too little leads to depression, anger issues, OCD, and suicide

  • Also tied to migraines, irritable bowel syndrome (IBS), and fibromyalgia

Endorphin

  • Inhibitory:

    • Involved in pain reduction and pleasure

    • Allows animal to hibernate

    • Slows heart rate, respiration, and metabolism

  • Drug like heroin, morphine, and opium cause slowing too, so too much and everything slows down permanently (death)

  • Excessive use of morphine/heroin causes a reduction in natural endorphin production which results in needing more drugs to replace natural endorphin. This is how addiction happens.

How can Neurotransmitters increase or decrease?

Agonist Mechanism (increase) is:

Any drug (or poison) that can increase activity of a NTs:

  1. Mimics the natural NTs shape

  2. Prevents reuptake of NTs to the pre-synaptic neuron (sending neuron)

  3. Blocks enzymes to break down leftover NTs in synapse

Antagonist Mechanism (decreases) is:

Any drug (or poison) that can reduces activity of NTs:

  1. Blocking the release of NTs from its terminal branch of the sending neuron

  2. Blocks receptor on post synaptic dendrite (receiving neuron)