receptor

Examples of receptor in the following topics:

• Types of Receptors

  • There are two types of receptors: internal receptors and cell-surface receptors.
  • Internal receptors can directly influence gene expression without having to pass the signal on to other receptors or messengers.
  • There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors.
  • Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme.
  • An example of this type of enzyme-linked receptor is the tyrosine kinase receptor.

• Binding Initiates a Signaling Pathway

  • Ligand binding to cell-surface receptors activates the receptor's intracellular components setting off a signaling pathway or cascade.
  • Cell-surface receptors, also known as transmembrane receptors, are membrane-anchored (integral) proteins that bind to external ligand molecules.
  • There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors.
  • All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.
  • Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme.

• Plasma Membrane Hormone Receptors

  • Lipid-insoluble hormones bind to receptors on the outer surface of the plasma membrane, via plasma membrane hormone receptors.
  • When a hormone binds to its membrane receptor, a G protein that is associated with the receptor is activated.
  • G proteins are proteins separate from receptors that are found in the cell membrane.
  • When a hormone is not bound to the receptor, the G protein is inactive and is bound to guanosine diphosphate, or GDP.
  • Describe the events that occur when a hormone binds to a plasma hormone receptor

• How Hormones Work

  • Hormones mediate changes in target cells by binding to specific hormone receptors.
  • Cells can have many receptors for the same hormone, but often also possess receptors for different types of hormones.
  • Cells respond to a hormone when they express a specific receptor for that hormone.
  • Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular hormone receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signaling pathways.
  • The hormone insulin binds to its receptor (1), which starts many protein activation cascades (2).

• Tastes and Odors

  • In addition to the activation of the taste receptors, there are similar receptors within the nose that coordinates with activation of the taste receptors.
  • Humans detect taste using receptors called taste buds.
  • Each of these receptors is specially adapted to determine one type of taste sensation.
  • Uniform distribution of taste receptors (the myth of the tongue map)
  • Humans detect taste using receptors called taste buds.

• Integration of Signals from Mechanoreceptors

  • The nociceptive receptors (those that detect pain) are located near the surface.
  • Both the upper and lower layers of the skin hold rapidly- and slowly-adapting receptors.
  • Receptors with large receptive fields usually have a "hot spot": an area within the receptive field (usually in the center, directly over the receptor) where stimulation produces the most intense response.
  • The size of the receptive field of a single receptor could be estimated from that distance.
  • Structure of four different types of sensory receptors found within the sensory system.

• Transduction and Perception

  • This takes place at the sensory receptor.
  • Receptor potentials are graded potentials: the magnitude of these graded (receptor) potentials varies with the strength of the stimulus.
  • For example, touch receptors, light receptors, and sound receptors are each activated by different stimuli.
  • An intense stimulus might initiate action potentials in a large number of adjacent receptors, while a less intense stimulus might stimulate fewer receptors.
  • Although perception relies on the activation of sensory receptors, perception happens, not at the level of the sensory receptor, but at the brain level.

• Intracellular Hormone Receptors

  • They then adhere to intracellular receptors residing in the cytoplasm or in the nucleus.
  • The hormone-receptor complex stimulates transcription of specific genes in the same way that steroid hormones do.
  • An intracellular nuclear receptor (NR) is located in the cytoplasm bound to a heat shock protein (HSP).
  • Upon hormone binding, the receptor dissociates from the heat shock protein and translocates to the nucleus.
  • Describe how hormones alter cellular activity by binding to intracellular receptors

• Reception and Transduction

  • Humans have about 12 million olfactory receptors distributed among hundreds of different receptor types that respond to different odors.
  • The sensory receptors on the cilia are proteins.
  • Each olfactory sensory neuron has only one type of receptor on its cilia.
  • When an odorant binds with a receptor that recognizes it, the sensory neuron associated with the receptor is stimulated.
  • Sweet, bitter, and umami tastants require a G-protein-coupled receptor.

• Synaptic Plasticity

  • One known mechanism involves a type of postsynaptic glutamate receptor: NMDA (N-Methyl-D-aspartate) receptors .
  • These receptors are normally blocked by magnesium ions.
  • Activated AMPA receptors allow positive ions to enter the cell.
  • One mechanism known to cause LTD also involves AMPA receptors.
  • The calcium that does flow through NMDA receptors initiates a different calcineurin and protein phosphatase 1-dependent cascade, which results in the endocytosis of AMPA receptors.