bipolar cell

Examples of bipolar cell in the following topics:

• Transduction of Light

  • Visual signals leave the cones and rods, travel to the bipolar cells, and then to ganglion cells.
  • Sometimes horizontal cells carry signals from one rod or cone to other photoreceptors and to several bipolar cells.
  • When a rod or cone stimulates a horizontal cell, the horizontal cell inhibits more-distant photoreceptors and bipolar cells, creating lateral inhibition.
  • Amacrine cells can distribute information from one bipolar cell to many ganglion cells.
  • The hyperpolarized membrane does not release glutamate to the bipolar cell.

• Neurons

  • While there are many defined neuron cell subtypes, neurons are broadly divided into four basic types: unipolar, bipolar, multipolar, and pseudounipolar .
  • A bipolar neuron has one axon and one dendrite extending from the soma.
  • An example of a bipolar neuron is a retinal bipolar cell, which receives signals from photoreceptor cells that are sensitive to light and transmits these signals to ganglion cells that carry the signal to the brain.
  • Pseudounipolar cells share characteristics with both unipolar and bipolar cells.
  • A pseudounipolar cell has a single structure that extends from the soma (like a unipolar cell), which later branches into two distinct structures (like a bipolar cell).

• Structural Diversity of Neurons

  • The cell body is the major biosynthetic center of the neuron.
  • Three major neuron groups make up this classification: multipolar, bipolar, and unipolar.
  • Bipolar neurons have two processes, an axon and a dendrite, that extend from opposite ends of the soma.
  • 1: Unipolar neuron, 2: Bipolar neuron, 3: Multipolar neuron, 4: Pseudounipolar neuron
  • A signal propagating down an axon to the cell body and dendrites of the next cell

• Vestibulocochlear (VIII) Nerve

  • This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain.
  • The vestibulocochlear nerve consists mostly of bipolar neurons and splits into two large divisions: the cochlear nerve and the vestibular nerve.
  • The vestibular ganglion houses the cell bodies of the bipolar neurons and extends processes to five sensory organs.
  • Hair cells of the cristae activate afferent receptors in response to rotational acceleration.
  • Hair cells of the maculae activate afferent receptors in response to linear acceleration.

• Transduction of Sound

  • The outer hair cells are arranged in three or four rows.
  • Their bending results in action potentials in the hair cells, and auditory information travels along the neural endings of the bipolar neurons of the hair cells (collectively, the auditory nerve) to the brain.
  • About 90 percent of the afferent neurons carry information from inner hair cells, with each hair cell synapsing with 10 or so neurons.
  • Outer hair cells connect to only 10 percent of the afferent neurons, and each afferent neuron innervates many hair cells.
  • The afferent, bipolar neurons that convey auditory information travel from the cochlea to the medulla, through the pons and midbrain in the brainstem, finally reaching the primary auditory cortex in the temporal lobe.

• Centrosome

  • The centrosome is an organelle that is the main microtubule organizing center of the animal cell and a regulator of cell-cycle progression.
  • In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell as well as a regulator of cell-cycle progression.
  • During the prophase in the process of cell division called mitosis, the centrosomes migrate to opposite poles of the cell.
  • In the absence of the centrioles the microtubules of the spindle are focused by motors allowing the formation of a bipolar spindle.
  • Some cell types arrest in the following cell cycle when centrosomes are absent.

• Reception and Transduction

  • Recall that sensory cells are neurons.
  • Olfactory neurons are bipolar neurons (neurons with two processes from the cell body).
  • The receptors are specialized to detect specific odorants, so the bipolar neurons themselves are specialized.
  • A taste bud is a cluster of gustatory receptors (taste cells) that are located within the bumps on the tongue called papillae (singular: papilla) .
  • In the human olfactory system, (a) bipolar olfactory neurons extend from (b) the olfactory epithelium, where olfactory receptors are located, to the olfactory bulb.

• Bipolar Disorders

  • The "bipolar spectrum" refers to the range in which these alternating moods may occur and includes bipolar I, bipolar II, cyclothymia, and other specified bipolar and related disorder.
  • Cyclothymia is a milder version of bipolar.
  • Neither the hypomanic or dysthymic episodes can meet the criteria for bipolar I or II.
  • It is estimated that roughly 1% of the adult population suffer from bipolar I, a further 1% suffer from bipolar II or cyclothymia, and somewhere between 2% and 5% percent suffer from "sub-threshold" forms of bipolar disorder.
  • Bipolar disorders have been shown to have a strong genetic and biological basis.

• Introduction to Biomedical Therapies

  • A depressed person might be given an antidepressant, a bipolar individual might be given a mood stabilizer, and a schizophrenic individual might be given an antipsychotic.
  • Others, with severe disorders like bipolar disorder or schizophrenia, may need to take psychotropic medication continuously for effective symptom management.
  • It involves using an electrical current to induce seizures in the brain in order to help alleviate the effects of certain mental conditions, such as severe forms of depression or bipolar disorder.
  • A more recent alternative to ECT is transcranial magnetic stimulation (TMS), a procedure approved by the FDA in 2008 that uses magnetic fields to stimulate nerve cells in the brain to improve depression symptoms; like ECT, it is used when other treatments have not worked (Mayo Clinic, 2012).

• Explaining Mood Disorders

  • Mood disorders are psychological disorders characterized by dysfunctional moods, including depression, bipolar, dysthymia, and cyclothymia.
  • When most people think of mood disorders, they typically think of depression (also called major depressive disorder and clinical depression) and bipolar disorder.
  • Cyclothymia is considered to be a milder or subthreshold form of bipolar disorder, with the two polar states being dysthymia and hypomania (as opposed to depression and mania in bipolar disorder).
  • The total number of reported stressful events in childhood is higher in those with an adult diagnosis of bipolar spectrum disorder, compared to those without.
  • Bipolar disorder is characterized by cycles of depressive and manic episodes.