purkinje

Examples of purkinje in the following topics:

• Electric Activity in the Heart

  • If the AV node also fails, Purkinje fibers are capable of acting as the pacemaker.
  • The reason Purkinje cells do not normally control the heart rate is that they generate action potentials at a lower frequency than the AV or SA nodes.
  • The Purkinje fibers are located in the inner ventricular walls of the heart.
  • Atrial and ventricular discharge through the Purkinje trees is assigned on a standard Electrocardiogram as the P Wave and QRS complex, respectively.
  • Purkinje fibers also have the ability of automatically firing at a rate of 15-40 beats per minute if left to their own devices.

• Functions of the Cerebellum in Integrating Movements

  • In the human cerebellum, information from 200 million mossy fiber inputs is expanded to 40 billion granule cells, whose parallel fiber outputs then converge onto 15 million Purkinje cells.
  • Because of the way that they are lined up longitudinally, the 1,000 or so Purkinje cells belonging to a microzone may receive input from as many as 100 million parallel fibers and focus their own output down to a group of less than 50 deep nuclear cells.
  • A module (a multizonal microcompartment in the terminology of Apps and Garwicz) consists of a small cluster of neurons in the inferior olivary nucleus, a set of long narrow strips of Purkinje cells in the cerebellar cortex (microzones), and a small cluster of neurons in one of the deep cerebellar nuclei.
  • The synapses between parallel fibers and Purkinje cells, and the synapses between mossy fibers and deep nuclear cells, are both susceptible to modification of their strength.
  • As the illustration on the right shows, Purkinje cell dendritic trees are flattened in a way that aligns with the microzone length, and parallel fibers cross the microzones at right angles.

• Modulation of Movement by the Cerebellum

  • Within this thin layer are several types of neurons with a highly regular arrangement, the most important being Purkinje cells and granule cells.
  • Most of them derive from early models formulated by David Marr and James Albus, which were motivated by the observation that each cerebellar Purkinje cell receives two dramatically different types of input.
  • However, each cerebellar Purkinje cell also gets input from one single climbing fiber, which is so strong that a single climbing fiber action potential will reliably cause a target Purkinje cell to fire a burst of action potentials.
  • Divergence and convergence: The 1000 or so Purkinje cells belonging to a microzone may receive input from as many as 100 million parallel fibers, and focus their own output down to a group of less than 50 deep nuclear cells.
  • Plasticity: The synapses between parallel fibers and Purkinje cells, and the synapses between mossy fibers and deep nuclear cells, are both susceptible to modification of their strength.

• Functions of the Cerebellum

  • This neural divergence is followed by parallel fiber outputs that converge onto 15 million Purkinje cells.
  • Due to their longitudinal alignment, the approximately 1000 Purkinje cells belonging to a microzone may receive input via neural convergence from as many as 100 million parallel fibers.
  • A module consists of a small cluster of neurons in the inferior olivary nucleus, a set of long narrow strips of Purkinje cells in the cerebellar cortex (microzones), and a small cluster of neurons in one of the deep cerebellar nuclei.
  • Plasticity: The synapses between parallel fibers and Purkinje cells and between mossy fibers and deep nuclear cells are both susceptible to modification of their strength.

• Neurons

  • For example, dendrites from a Purkinje cell in the cerebellum are thought to receive contact from as many as 200,000 other neurons.
  • The Purkinje cell, a multipolar neuron in the cerebellum, has many branching dendrites, but only one axon.
  • Examples include (a) a pyramidal cell from the cerebral cortex, (b) a Purkinje cell from the cerebellar cortex, and (c) olfactory cells from the olfactory epithelium and olfactory bulb.

• Electrocardiogram and Correlation of ECG Waves with Systole

  • The QRS complex represents action potentials moving from the AV node, through the bundle of His and left and right branches and Purkinje fibers into the ventricular muscle tissue.
  • Following the T wave is the U wave, which represents repolarization of the Purkinje fibers.

• Parts of the Cerebellum

  • This thin layer contains several types of neurons with a highly regular arrangement, most importantly Purkinje cells and granule cells .

• Anatomy of the Heart

  • They are located in the left atrial wall of the heart and send nerve impulses to a large, highly specialized set of nerves called the Purkinje fibers, which in turn send those nerve impulses to the cardiac muscle tissue.

• Layers of the Heart Walls

  • The Purkinje fibers are located just beneath the endocardium and send nervous impulses from the SA and AV nodes outside of the heart into the myocardial tissues.

• Electrical Events

  • The AV node receives action potentials from the SA node, and transmits them through the bundle of His, left and right bundle branches, and Purkinje fibers, which cause depolarization of ventricular muscle cells leading to ventricular contraction.