Afferent fibers of cerebellum : climbing and mossy fiber

 Afferent fibers of cerebellum : climbing and mossy fiber 

climbing fiber 

Climbing fibers  are the terminal fibers of the olivocerebellar tracts

One climbing fiber makes synaptic contact with

1-10  purkinje neuron

Climbing fiber arises from

·         the inferior olivary nucleus located in the medulla oblongata

They passes through the granular layer and purkinje layer and terminate into  the molecular layer

These axons pass through the pons and enter the cerebellum via the inferior cerebellar peduncle

These fibers provide very powerful, excitatory input to the cerebellum which results in the generation of complex spike excitatory postsynaptic potential (EPSP) in Purkinje cells

 In this way climbing fibers (CFs) perform a central role in motor behaviors.

They influence 

·         Motor timing.

·         the control & coordination of movements

·         They contribute to sensory processing and cognitive tasks likely by encoding the timing of sensory input independently of attention or awareness

Climbing fibers cross the midline in the brain stem, enter the cerebellum through the inferior cerebellar peduncle, and terminate contralaterally within the cerebellum.

In the central nervous system, these fibers are able to undergo remarkable regenerative modifications in response to injuries, being able to generate new branches by sprouting to innervate surrounding Purkinje cells if these lose their CF innervation.

This kind of injury-induced sprouting has been shown to need the growth associated protein GAP-43

Climbing fiber cannot have rosettes

A single purkinje neuron makes synaptic contact with only one climbing fiber

Climbing fiber > purkinje fiber

Mossy fiber 

 

Mossy fibers are the termical fibers of all other cerebellar afferent tract

One mossy fiber makes synaptic contact with 1000 purkinje neuron through granule cells of cerebellum

Mossy fiber arises from many sources

·         cerebral cortex ( largest),

·         the vestibular nerve and nuclei,

·         the spinal cord,

·         the reticular formation, and

·         feedback from deep cerebellar nuclei

They terminate in the granular layer of the cortex within the glomeruli

Axons of mossy fiber enter the cerebellum via the superior , middle and inferior cerebellar peduncles

They serve as inhibitory interneuron , they influence the degree of purkinje cell excitation

They  modify muscle activity through the motor control areas of the brain stem and cerebral cortex

Depending on the source of the mossy fibers, their termination within the cerebellum can be predominantly ipsilateral or contralateral and is restricted to particular lobules.

Keratan sulfate proteoglycan phosphacan regulates mossy fiber outgrowth and regeneration

Each mossy fiber can have up to 50 rosettes

unlike climbing fibers, mossy fibers DO NOT go directly to the Purkinje cell.

Mossy fiber > granule cell > purkinje fiber

Mossy fiber of cerebellum

Mossy fiber of cerebellum 

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They are the termical fibers of all other cerebellar afferent tract

One mossy fiber makes synaptic contact with 1000 purkinje neuron through granule cells of cerebellum

Mossy fiber arises from many sources

·         cerebral cortex ( largest),

·         the vestibular nerve and nuclei

·         the spinal cord ,

·         the reticular formation  

            feedback from deep cerebellar nuclei

Mossy fibers from the vestibular ganglion are the first mossy fibers to arrive in the cerebellum

They terminate in the granular layer of the cortex within the glomeruli

Axons of mossy fiber enter the cerebellum via the superior , middle and inferior cerebellar peduncles

They serve as inhibitory interneuron , they influence the degree of purkinje cell excitation

They  modify muscle activity through the motor control areas of the brain stem and cerebral cortex

Depending on the source of the mossy fibers, their termination within the cerebellum can be predominantly ipsilateral or contralateral and is restricted to particular lobules.

Keratan sulfate proteoglycan phosphacan regulates mossy fiber outgrowth and regeneration

Each mossy fiber can have up to 50 rosettes

unlike climbing fibers, mossy fibers DO NOT go directly to the Purkinje cell.

Mossy fiber > granule cell > purkinje fiber 

 

Climbing fiber of cerebellum

Climbing fiber of cerebellum 

For learning anatomy, please visit :

My youtube channel :  @easyhumanatomy73

My website : http://easyhumananatomy.com

My facebook page: https://www.facebook.com/easyhumanatomy/

My blog: http://www.easyhumanatomy73.blogspot.com

My blog:  Difference between : http://www.microscopicanatomybd.blogspot.com

They are the terminal fibers of the olivocerebellar tracts

One climbing fiber makes synaptic contact with

1-10  purkinje neuron

Climbing fiber arises from

·         the inferior olivary nucleus located in the medulla oblongata

They passes through the granular layer and purkinje layer and terminate into  the molecular layer

These axons pass through the pons and enter the cerebellum via the inferior cerebellar peduncle

These fibers provide very powerful, excitatory input to the cerebellum which results in the generation of complex spike excitatory postsynaptic potential (EPSP) in Purkinje cells

 In this way climbing fibers (CFs) perform a central role in motor behaviors.

They influence 

·         Motor timing.

·         the control & coordination of movements

·         They contribute to sensory processing and cognitive tasks likely by encoding the timing of sensory input independently of attention or awareness

Climbing fibers cross the midline in the brain stem, enter the cerebellum through the inferior cerebellar peduncle, and terminate contralaterally within the cerebellum.

In the central nervous system, these fibers are able to undergo remarkable regenerative modifications in response to injuries, being able to generate new branches by sprouting to innervate surrounding Purkinje cells if these lose their CF innervation.

This kind of injury-induced sprouting has been shown to need the growth associated protein GAP-43

Climbing fiber cannot have rosettes

A single purkinje neuron makes synaptic contact with only one climbing fiber

Climbing fiber > purkinje fiber 

 

Short discussion about autosome

 

Autosome

An autosome is any of the numbered chromosomes, as opposed to the sex chromosomes. Humans have 22 pairs of autosomes and one pair of sex chromosomes (the X and Y). Autosomes are numbered roughly in relation to their sizes. That is, Chromosome 1 has approximately 2,800 genes, while chromosome 22 has approximately 750 genes.

An autosome is any chromosome that is not a sex chromosome (an allosome).

 The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome pairs which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA.

For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters. By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. Unusual combinations of XYY, XXY, XXX, XXXX, XXXXX or XXYY, among other allosome combinations, are known to occur and usually cause developmental abnormalities.

Autosomes still contain sexual determination genes even though they are not sex chromosomes. For example, the SRY gene on the Y chromosome encodes the transcription factor TDF and is vital for male sex determination during development. TDF functions by activating the SOX9 gene on chromosome 17, so mutations of the SOX9 gene can cause humans with an ordinary Y chromosome to develop as females.

All human autosomes have been identified and mapped by extracting the chromosomes from a cell arrested in metaphase or prometaphase and then staining them with a type of dye (most commonly, Giemsa). These chromosomes are typically viewed as karyograms for easy comparison. Clinical geneticists can compare the karyogram of an individual to a reference karyogram to discover the cytogenetic basis of certain phenotypes. For example, the karyogram of someone with Patau Syndrome would show that they possess three copies of chromosome 13. Karyograms and staining techniques can only detect large-scale disruptions to chromosomes—chromosomal aberrations

Autosomal genetic disorders

Autosomal genetic disorders can arise due to a number of causes, some of the most common being nondisjunction in parental germ cells or Mendelian inheritance of deleterious alleles from parents. Autosomal genetic disorders which exhibit Mendelian inheritance can be inherited either in an autosomal dominant or recessive fashion

 These disorders manifest in and are passed on by either sex with equal frequency

 Autosomal dominant disorders are often present in both parent and child, as the child needs to inherit only one copy of the deleterious allele to manifest the disease. Autosomal recessive diseases, however, require two copies of the deleterious allele for the disease to manifest. Because it is possible to possess one copy of a deleterious allele without presenting a disease phenotype, two phenotypically normal parents can have a child with the disease if both parents are carriers (also known as heterozygotes) for the condition.

Autosomal aneuploidy can also result in disease conditions. Aneuploidy of autosomes is not well tolerated and usually results in miscarriage of the developing fetus. Fetuses with aneuploidy of gene-rich chromosomes—such as chromosome 1—never survive to term and fetuses with aneuploidy of gene-poor chromosomes—such as chromosome 21— are still miscarried over 23% of the time Possessing a single copy of an autosome (known as a monosomy) is nearly always incompatible with life, though very rarely some monosomies can survive past birth. Having three copies of an autosome (known as a trisomy) is far more compatible with life, however. A common example is Down syndrome, which is caused by possessing three copies of chromosome 21 instead of the usual two

Partial aneuploidy can also occur as a result of unbalanced translocations during meiosis Deletions of part of a chromosome cause partial monosomies, while duplications can cause partial trisomies. If the duplication or deletion is large enough, it can be discovered by analyzing a karyogram of the individual. Autosomal translocations can be responsible for a number of diseases, ranging from cancer to schizophrenia

 Unlike single gene disorders, diseases caused by aneuploidy are the result of improper gene dosage, not nonfunctional gene product smaller than a few million base pairs generally cannot be seen on a karyogram

An autosome is one of the 22 numbered pairs of chromosomes that most of us carry in almost all of the cells of our body. We actually have a total of 23 pairs of chromosomes in these cells, for a total of 46 chromosomes, but two of those are referred to by letter rather than by number and are called sex chromosomes rather than autosomes, since they--that is the X and Y chromosome--help determine what sex, or gender, we are. The 22 pairs of autosomes are referred to by number basically in inverse correlation with their size. That is, Chromosome 1, with the smallest number, is actually the largest chromosome. It has almost 3,000 genes on it. And we go down to the smallest chromosomes, the ones with the largest numbers. You think that would be Chromosome 22, since we have Chromosomes 1 through 22, which only has about 750 genes, but in fact Chromosome number 22 is not the smallest of the autosomes. We thought it was when it was first described, so that's how it got named 22. It turns out that Chromosome 21 is actually a little bit smaller than Chromosome 22.