Synaptic transmission

Describe how weak and strong stimuli are transmitted from neuron to neuron

Low stimulus

  • low amplitude

  • low frequency

  • less NT release

High stimulus

  • High amplitude

  • High frequency

  • High release of NT

Contrast electrical and chemical synapses

Chemical

  • slower and unidirectional

  • uses neurotransmitter

  • causes EPSP or IPSP

Electrical

  • Connected via gap junctions (bidirectional)

  • causes electrotonic potential in post synaptic cell

Describe the general mechanism of synaptic transmission, including how vesicles wiht neurotransmitters fuse, the role of Ca2+ in the axon terminus and how neurotransmitters can be removed

As an action potential makes its way down the neuron it opens up voltage gated Ca2+ channels which stimulates SNARE proteins allowing NT to leave the presynaptic terminal into the synaptic cleft.

REMOVAL via:

  • presynaptic cell

  • astroglia

  • degradation enzyme

For each neurotransmitter listed describe its importance, synthesis, its receptors, its effects on the postsynaptic cell, its removal and any examples of disease or drugs specific that neurotransmitter.

Glutamate

  • made by astroglia

  • removed by astrocytes and presynaptic cells

  • Metabotropic receptors

  • Ionotropic receptors

    • causes EPSP

    • AMPA and Kainate (Na+ channels)

  • Voltage gated and Ionotropic

    • NMDA - Ca2+ channels

      • paired with AMPA and Kainate

        • AMPA or Kainate opens leading to Na+ influx

        • kicks off Mg2+ in NMDA

        • NMDA opens leading to Ca2+ influx depolarizing the cell.

Acetylcholine

  • found in:

    • somatic motor neurons

    • autonomic Nervous system

  • Receptors:

    • Nicotinic cholinergic receptors

    • Muscarinic Cholinergic receptor

GABA and Glycine

  • inhibitory

  • Receptors

    • GABA A: ionotropic Cl- channels

    • GABA B: metabotropic

  • agonists:

    • Benzodiazepines

      • xanax and valium

    • Benxodiazepin like

      • Ambion

    • EtOH

Catecholamines

  • made from tyrosine

  • all receptors are metabotropic

  • Includes:

    • Dopamine

      • reuptake via Catecholomethyl transferase or Monoamine oxidase

      • reward system:

        • seen in schizophrenia treatment and cocaine (reuptake inhibitor)

        • initiates motor activity in basal ganglia and midbrain (parkinsons)

        • reglation of prolactin

        • D1-D5 receptors

    • NorE/ NorA

      • NorE (post ganglionic neurons) vs NorA (adrenal medulla)

      • a1,a2,B1,B2

    • Epinephrine or Adrenalin

      • a1,a2,B1,B2

Serotonin

  • Contentment and arousal

  • Removal done via serotonin specific reuptake

  • Cocaine is reuptake inhibitor

  • used as antidepressants