neurotransmitter

Examples of neurotransmitter in the following topics:

• Neurotransmitters

  • Neurotransmitters match up with receptors like a key in a lock.
  • A neurotransmitter binds to its receptor and will not bind to receptors for other neurotransmitters, making the binding a specific chemical event.
  • The cholinergic system is a neurotransmitter system of its own, and is based on the neurotransmitter acetylcholine (ACh).
  • Another class of neurotransmitter is the biogenic amine, a group of neurotransmitters made enzymatically from amino acids.
  • Dopamine is the best-known neurotransmitter of the catecholamine group.

• Types of Neurotransmitters by Function

  • Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse.
  • Neurotransmitters fall into several chemical classes based on the molecular structure.
  • The major types of neurotransmitters include acetylcholine, biogenic amines, and amino acids.  
  • Acetylcholine, which acts on the neuromuscular junction, was the first neurotransmitter identified.
  • Glutamate and gamma-aminobutyric acid (GABA) are amino acid-based neurotransmitters.

• Synaptic Transmission

  • The binding of a neurotransmitter to its receptor is reversible.
  • The effects of the neurotransmitter generally lasts few milliseconds before being terminated.
  • The neurotransmitter termination can occur in three ways.
  • Third, diffusion of the neurotransmitter as it moves away from the synapse.
  • Communication at chemical synapses requires release of neurotransmitters.

• Classification of Neurons

  • Neurons can be classified by direction of travel, neurotransmitter utilized, or their electrophysiological properties.
  • A neuron releases a neurotransmitter that binds to chemical receptors on the target neuron .
  • The combination of neurotransmitter and receptor properties results in an excitatory, inhibitory, or modulatory change to the target neuron.
  • For example, the two most common neurotransmitters in the brain (90% of neurons), glutamate and GABA, have opposing actions.
  • Describe how neurons can be classified by direction of travel, neurotransmitter utilized, or their electrophysiological properties

• Excitation–Contraction Coupling

  • Because neuron axons do not directly contact the motor-end plate, communication occurs between nerves and muscles through neurotransmitters.
  • The receptors are sodium channels that open to allow the passage of Na+ into the cell when they receive neurotransmitter signal.
  • Acetylcholine (ACh) is a neurotransmitter released by motor neurons that binds to receptors in the motor end plate.
  • As a neurotransmitter binds, these ion channels open, and Na+ ions cross the membrane into the muscle cell.
  • Explain the process of excitation-contraction coupling and the role of neurotransmitters

• Postsynaptic Potentials and Their Integration at the Synapse

  • The neurotransmitters bind to receptors on the postsynaptic terminal resulting in an opening of ion channels.
  • At excitatory synapses, neurotransmitter binding depolarizes the postsynaptic membrane.
  • If enough neurotransmitter binds, depolarization of the postsynaptic membrane can reach 0mV, which is higher than threshold of -30-50mV.  
  • Neurotransmitter binding at inhibitory synapses reduces a postsynaptic neuron's ability to generate an action potential.
  • Most inhibitory neurotransmitters hyperbolize the postsynaptic membrane by making it more permeable to potassium or chloride.

• Cholinergic Neurons and Receptors

  • Acetylcholine is a neurotransmitter in the central and peripheral nervous systems that affects plasticity, arousal, and reward.
  • Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the motor division of the somatic nervous system (sensory neurons use glutamate and various peptides at their synapses).
  • Acetylcholine is also the principal neurotransmitter in all autonomic ganglia.
  • However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle.
  • Acetylcholine was also the first neurotransmitter to be identified.

• Mechanics of the Action Potential

  • During a chemical reaction, a chemical called a neurotransmitter is released from one cell into another.
  • Synaptic cleft: the small space at the synapse that receives neurotransmitters.
  • The neurotransmitter diffuses within the cleft.
  • The binding of neurotransmitter causes the receptor molecule to be activated in some way.
  • Several types of activation are possible, depending on what kind of neurotransmitter was released.

• Stages of the Action Potential

  • A neuron affects other neurons by releasing a neurotransmitter that binds to chemical receptors.
  • A neurotransmitter can be thought of as a key, and a receptor as a lock: the key unlocks a certain response in the postsynaptic neuron, communicating a particular signal.
  • However, in order for a presynaptic neuron to release a neurotransmitter to the next neuron in the chain, it must go through a series of changes in electric potential.
  • Reuptake refers to the reabsorption of a neurotransmitter by a presynaptic (sending) neuron after it has performed its function of transmitting a neural impulse.
  • Reuptake is necessary for normal synaptic physiology because it allows for the recycling of neurotransmitters and regulates the neurotransmitter level in the synapse, thereby controlling how long a signal resulting from neurotransmitter release lasts.

• The Synapse

  • The presynaptic neuron contains a chemical called a neurotransmitter that is packaged into synaptic vesicles clustered beneath the membrane in the axon terminal.
  • The neurotransmitter is released into and diffuses across the synaptic cleft, where it binds to specific receptors in the membrane on the postsynaptic side of the synapse.
  • Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may also follow graded electrical potentials found in dendrites.
  • A: Neuron (Presynaptic) B: Neuron (Postsynaptic)MitochondriaSynaptic vesicle full of neurotransmitterAutoreceptorSynaptic cleftNeurotransmitter receptorCalcium ChannelFused vesicle releasing neurotransmitterNeurotransmitter re-uptake pump