Purkinje cell
Encyclopedia
For the cells of the electrical conduction system of the heart
, see Purkinje fibers
Purkinje cells, or Purkinje neurons (icon ), are a class of GABA
ergic neurons located in the cerebellar cortex
. They are named after their discoverer, Czech
anatomist Jan Evangelista Purkyně
(ˈpurkɪɲɛ).
These cells
are some of the largest neuron
s in the human brain
(Betz cell
s being the largest), with an intricately elaborate dendritic
arbor, characterized by a large number of dendritic spine
s. Purkinje cells are found within the Purkinje layer in the cerebellum
. Purkinje cells are aligned like dominos stacked one in front of the other. Their large dendritic arbors form nearly two-dimensional layers through which parallel fiber
s from the deeper-layers pass. These parallel fibers make relatively weaker excitatory
(glutamatergic) synapses to spines in the Purkinje cell dendrite, whereas climbing fibers originating from the inferior olivary nucleus
in the medulla
provide very powerful excitatory input to the proximal dendrites and cell soma. Parallel fibers pass orthogonally through the Purkinje neuron's dendritic arbor, with up to 200,000 parallel fibers forming a Granule-cell-Purkinje-cell synapse
with a single Purkinje cell. Each Purkinje cell receives ca 500 climbing fiber synapses, all originating from a single climbing fiber. Both basket and stellate cells (found in the cerebellar molecular layer) provide inhibitory (GABAergic) input to the Purkinje cell, with basket cells synapsing on the Purkinje cell axon initial segment and stellate cells onto the dendrites.
Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all motor coordination
in the cerebellar cortex.
Purkinje cells show two distinct forms of electrophysiological activity:
Purkinje cells show spontaneous electrophysiological activity in the form of trains of spikes both sodium- as well as calcium-dependent was initially shown by Rodolfo Llinas
(Llinas and Hess (1977) and Llinas and Sugimori (1980). P-type calcium channels were named after Purkinje cells where they were initially encountered (Llinas et al. 1989), which are crucial in cerebellar function. It has recently been shown that climbing fiber activation of the Purkinje cell can shift its activity from a quiet state to a spontaneously-active state, and vice-versa, serving as a type of toggle switch (Loewenstein et al., 2005, Nature Neuroscience). However, these findings have recently been challenged by a study suggesting that such toggling by climbing fiber inputs occurs predominantly in anaesthetized animals, and that Purkinje cells in awake behaving animals, in general, operate almost continuously in the upstate (Schonewille et al., 2006, Nature Neuroscience).
Findings have suggested that Purkinje cell dendrites release endocannabinoids that can transiently downregulate both excitatory and inhibitory synapses
, autism
) and neurodegenerative diseases that are not thought to have a known genetic basis (cerebellar type of multiple system atrophy, sporadic ataxias).
In some domestic animals, a condition where the Purkinje cells begin to atrophy shortly after birth, called Cerebellar abiotrophy
, can lead to symptoms including ataxia
, intention tremors, hyperreactivity, lack of menace reflex
, stiff or high-stepping gait, apparent lack of awareness of wherein the feet are (sometimes standing or walking with a foot knuckled over), and a general inability to determine space and distance. A similar condition known as cerebellar hypoplasia
occurs when Purkinje cells either fail to develop in utero or die off in utero prior to birth. The genetic conditions Ataxia Telangiectasia
and Niemann Pick disease Type C, as well as cerebellar essential tremor
, involve the progressive loss of Purkinje cells.
Spinal pathology as well as loss of dendritic branches of the Purkinje cells have been also described in Alzheimer's disease.
Electrical conduction system of the heart
The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
, see Purkinje fibers
Purkinje fibers
For the nervous cells, see Purkinje cellPurkinje fibers are located in the inner ventricular walls of the heart, just beneath the endocardium...
Purkinje cells, or Purkinje neurons (icon ), are a class of GABA
Gabâ
Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...
ergic neurons located in the cerebellar cortex
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. They are named after their discoverer, Czech
Czech people
Czechs, or Czech people are a western Slavic people of Central Europe, living predominantly in the Czech Republic. Small populations of Czechs also live in Slovakia, Austria, the United States, the United Kingdom, Chile, Argentina, Canada, Germany, Russia and other countries...
anatomist Jan Evangelista Purkyně
Jan Evangelista Purkyne
Jan Evangelista Purkyně was a Czech anatomist and physiologist. He was one of the best known scientists of his time. His son was the painter Karel Purkyně...
(ˈpurkɪɲɛ).
Anatomy
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
are some of the largest neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s in the human brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
(Betz cell
Betz cell
Betz cells are pyramidal cell neurons located within the fifth layer of the grey matter in the primary motor cortex, M1. They are named after Vladimir Alekseyevich Betz, who described them in his work published in 1874. These neurons are the largest in the central nervous system, sometimes reaching...
s being the largest), with an intricately elaborate dendritic
Dendrite
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...
arbor, characterized by a large number of dendritic spine
Dendritic spine
A dendritic spine is a small membranous protrusion from a neuron's dendrite that typically receives input from a single synapse of an axon. Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body...
s. Purkinje cells are found within the Purkinje layer in the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. Purkinje cells are aligned like dominos stacked one in front of the other. Their large dendritic arbors form nearly two-dimensional layers through which parallel fiber
Parallel fiber
Parallel fibers arise from granule cells in the cerebellar cortex. They form excitatory synapses onto the dendrites of Purkinje cells ....
s from the deeper-layers pass. These parallel fibers make relatively weaker excitatory
Excitatory synapse
An excitatory synapse is a synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell. Neurons form networks through which nerve impulses travel, each neuron often making numerous connections with other cells...
(glutamatergic) synapses to spines in the Purkinje cell dendrite, whereas climbing fibers originating from the inferior olivary nucleus
Inferior olivary nucleus
The inferior olivary nucleus is the largest nucleus situated in the olivary body, part of the medulla oblongata.-Function:It is closely associated with the cerebellum, meaning that it is involved in control and coordination of movements, sensory processing and cognitive tasks likely by encoding the...
in the medulla
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
provide very powerful excitatory input to the proximal dendrites and cell soma. Parallel fibers pass orthogonally through the Purkinje neuron's dendritic arbor, with up to 200,000 parallel fibers forming a Granule-cell-Purkinje-cell synapse
Granule-cell-Purkinje-cell synapse
Granule-cell–Purkinje-cell synapses or gcPc synapses are the junctions that form the synapse in the cerebellum between granule cells and Purkinje cells. These synapses are thought to be a storage site for the information that is required for motor coordination and their misfunctioning is involved...
with a single Purkinje cell. Each Purkinje cell receives ca 500 climbing fiber synapses, all originating from a single climbing fiber. Both basket and stellate cells (found in the cerebellar molecular layer) provide inhibitory (GABAergic) input to the Purkinje cell, with basket cells synapsing on the Purkinje cell axon initial segment and stellate cells onto the dendrites.
Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all motor coordination
Motor coordination
thumb|right|Motor coordination is shown in this animated sequence by [[Eadweard Muybridge]] of himself throwing a diskMotor coordination is the combination of body movements created with the kinematic and kinetic parameters that result in intended actions. Such movements usually smoothly and...
in the cerebellar cortex.
Electrophysiological activity
- Simple spikes occur at rates of 17 – 150 Hz (Raman and Bean, 1999) either spontaneously, or when Purkinje cells are activated synaptically by the parallel fibers, the axons of the granule cells.
- Complex spikes are slow, 1–3 Hz spikes, characterized by an initial prolonged large-amplitude spike, followed by a high-frequency burst of smaller-amplitude action potentials. They are caused by climbing fiber activation, and can involve the generation of calcium-mediated action potentials in the dendrites. Following complex spike activity, simple spikes can be suppressed by the powerful complex spike input.
Purkinje cells show spontaneous electrophysiological activity in the form of trains of spikes both sodium- as well as calcium-dependent was initially shown by Rodolfo Llinas
Rodolfo Llinás
Rodolfo R. Llinás PhD is a neuroscientist. He is presently the Thomas and Suzanne Murphy Professor of Neuroscience and Chairman of the department of Physiology & Neuroscience at the NYU School of Medicine...
(Llinas and Hess (1977) and Llinas and Sugimori (1980). P-type calcium channels were named after Purkinje cells where they were initially encountered (Llinas et al. 1989), which are crucial in cerebellar function. It has recently been shown that climbing fiber activation of the Purkinje cell can shift its activity from a quiet state to a spontaneously-active state, and vice-versa, serving as a type of toggle switch (Loewenstein et al., 2005, Nature Neuroscience). However, these findings have recently been challenged by a study suggesting that such toggling by climbing fiber inputs occurs predominantly in anaesthetized animals, and that Purkinje cells in awake behaving animals, in general, operate almost continuously in the upstate (Schonewille et al., 2006, Nature Neuroscience).
Findings have suggested that Purkinje cell dendrites release endocannabinoids that can transiently downregulate both excitatory and inhibitory synapses
Medical conditions related to Purkinje cells
In humans, Purkinje cells are affected in a variety of diseases ranging from toxic exposure (alcohol, lithium), to autoimmune diseases and to genetic mutations (spinocerebellar ataxias, Unverricht-Lundborg diseaseUnverricht-Lundborg disease
Unverricht-Lundborg disease is the most common form of an uncommon group of genetic epilepsy disorders called progressive myoclonic epilepsy. It is caused due to a mutation in the cystatin B gene...
, autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
) and neurodegenerative diseases that are not thought to have a known genetic basis (cerebellar type of multiple system atrophy, sporadic ataxias).
In some domestic animals, a condition where the Purkinje cells begin to atrophy shortly after birth, called Cerebellar abiotrophy
Cerebellar abiotrophy
Cerebellar abiotrophy , also referred to as the cerebellar cortical abiotrophy , which is a genetic neurological disease in animals best known to affect certain breeds of horses and dogs. It develops when the neurons known as Purkinje cells, located in the cerebellum of the brain, begin to die...
, can lead to symptoms including ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
, intention tremors, hyperreactivity, lack of menace reflex
Menace reflex
The menace reflex is one of three forms of blink reflex. It is the reflex blinking that occurs in response to the rapid approach of an object. The reflex comprises blinking of the eyelids, in order to protect the eyes from potential damage, but may also including turning of the head, neck, or...
, stiff or high-stepping gait, apparent lack of awareness of wherein the feet are (sometimes standing or walking with a foot knuckled over), and a general inability to determine space and distance. A similar condition known as cerebellar hypoplasia
Cerebellar hypoplasia
Cerebellar hypoplasia is a developmental disorder characterized by the incomplete or underdevelopment of the cerebellum. It may be genetic or occur sporadically. Cerebellar hypoplasia may be caused by thyroid abnormalities, environmental influences such as drugs and chemicals or viral infections or...
occurs when Purkinje cells either fail to develop in utero or die off in utero prior to birth. The genetic conditions Ataxia Telangiectasia
Ataxia telangiectasia
Ataxia telangiectasia is a rare, neurodegenerative, inherited disease that affects many parts of the body and causes severe disability. Ataxia refers to poor coordination and telangiectasia to small dilated blood vessels, both of which are hallmarks of the disease...
and Niemann Pick disease Type C, as well as cerebellar essential tremor
Essential tremor
Essential tremor is a slowly progressive neurological disorder whose most recognizable feature is a tremor of the arms that is apparent during voluntary movements such as eating and writing...
, involve the progressive loss of Purkinje cells.
Spinal pathology as well as loss of dendritic branches of the Purkinje cells have been also described in Alzheimer's disease.
Links
- Cell Centered Database - Purkinje
- Disorders of cerebellum
- NIF Search - Purkinje Cell via the Neuroscience Information FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...