MCAT Content / Nerve Cell / Synaptic Activity Transmitter Molecules

Synaptic activity: transmitter molecules

Topic: Nerve Cell

Synaptic transmission is a chemical activity that is involved in the transmission of the impulse via release, diffusion, receptor binding of neurotransmitter molecules which are essential for the impulse to be forwarded to the postsynaptic neuron.

Neurotransmitter molecules are released from the presynaptic neuron. Once the transmitter molecules get released into the synapse, they diffuse across the synaptic cleftbind to receptors on the postsynaptic neuron which causes ions to move into the postsynaptic neuron continuing the impulse. Common neurotransmitters include acetylcholine (ACh), norepinephrine (NE), dopamine, serotonin, histamine, and ATP.

Constant synaptic activity is undesirable. Thus, neurotransmission must be regulated and removed from the synaptic cleft. The neurotransmitter termination can occur in three ways:

  1. Reuptake by presynaptic terminal where the neurotransmitter is stored or destroyed by enzymes.
  2. Degradation by enzymes in the synaptic cleft, such as acetylcholinesterase.
  3. Diffusion of the neurotransmitter as it moves away from the synapse.

 

Practice Questions

 

Khan Academy

 

MCAT Official Prep (AAMC)

Biology Question Pack, Vol 2. Passage 7 Question 45

Biology Question Pack, Vol 2. Passage 7 Question 49


Key Points

• In a chemical synapse, synaptic cleft separates the pre-and post-synaptic membranes. 

• The chemical event is involved in the transmission of the impulse via release, diffusion, receptor binding of neurotransmitter molecules, and unidirectional communication between neurons.

• Neurotransmitter molecules include acetylcholine (ACh), norepinephrine (NE), dopamine, serotonin, histamine, and ATP.

• The neurotransmitter termination can occur in three ways – reuptake, enzymatic degradation in the cleft, and diffusion.


Key Terms

Synaptic cleft: the space between neurons at a nerve synapse across which a neurotransmitter transmits a nerve impulse

Post-synaptic: the neurone that is on the other side of the synaptic cleft which receives the impulse

Pre-synaptic neuron: is the neuron conducting impulses towards the synapse

Neurotransmitters: a type of chemical messenger which transmits signals across a chemical synapse

Neurotransmitter termination: the degradation of the neurotransmitter in the synaptic cleft after the neurotransmitter has been released. 



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