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vfiekz [6]
1 year ago
8

at short focusing distances, ciliary muscles contract. what effect do these contractions have on the suspensory ligaments?

Biology
1 answer:
True [87]1 year ago
6 0

At short focusing distances, ciliary muscles contract causing the suspensory ligaments to tighten.

The ciliary muscle is an integral muscle of the eye that is constructed as a ring of smooth muscle in the middle layer of the eye, the uvea (vascular layer). It regulates the passage of aqueous humor into Schlemm's canal and governs accommodation for observing objects at different distances.

A suspensory ligament is a ligament that provides support to a body part, particularly an organ. The suspensory ligament protects the fetlock from hyperextension (i.e., falling too low) during exercise. The ligament begins in both the fore and hindlimbs at its connection to the back of the upper cannon bone.

When the ciliary muscle relaxes, its diameter increases; when the suspensory ligaments tighten, the lens becomes thinner. This occurs when concentrating on a celestial object. When the ciliary muscle contracts, the lens becomes much more circular and has more focusing power because the pressure on the zonular fibers is reduced. When the ciliary muscles relax, these fibers contract, pulling the lens out and creating a flatter shape with less focusing power 

For more information on suspensory ligaments, visit :

brainly.com/question/12999415

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Countercurrent multiplication involves A) ions leaving ascending limb to make water come out of the descending limb B) water lea
Snowcat [4.5K]

Answer:

The correct option is A

Countercurrent multiplication is the process whereby energy is used to generate an osmotic gradient in which water is reabsorbed from the tubular fluid to produced concentrated urine.

Explanation:

Countercurrent multiplication moves sodium chloride from tubular fluid into interstitial space deep within the kidneys. The concurrent multiplication process build up osmotic gradient interstitial fluid in a single effect. Here, sodium chloride is driven by active transport out of the tubular fluid in the thick ascending limb into the interstitial fluid, which becomes hyperosmotic. This result to water moving passively down its concentration gradient out of the tubular fluid in the descending limb into the interstitial space to a point where it attains a state of equilibrium.

Therefore,the correct option is A, where the ions leaves the ascending limb to make water comes out of descending limb.

4 0
3 years ago
The eukaryotic cell organelle that most resembles a bacterial cell is the
marishachu [46]

Answer:

mitochondria

Explanation:

Both bacteria and mitochondria have their own cell

6 0
2 years ago
Predict my happen to population that is experiencing little immigration and emigration low birth rate and high death rate
Furkat [3]
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7 0
2 years ago
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What are two diffrences between replication and transcription?
Ghella [55]
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1.) Transcription involved both DNA and RNA, whilst replication only involves DNA.
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Hope I helped.
5 0
3 years ago
A gene is involved in promoting limb development in humans. The gene is initially weakly activated during the limb induction pha
Anna [14]

Answer:

1. If the gene is weakly activated, it likely lacks repressive histone modifications, but may also lack the presence of histone marks associated with strong transcriptional activation such as acetylation.

When the gene is strongly activated, it likely lacks repressive marks (such as H3K9me2/3 and H3K27me3 - both examples of repressive histone methylation) and might possess some activating histone acetylation marks, such as H3K4ac, and active histone methylation such as H3K4me3

<em>An aside: The pattern and presence of different histone modifications would depend on the gene, but based on the fact that it is a developmental gene, I would assume that H3K27me3 and H3K4me3 are at play (these are part of the Polycomb/Trithorax system)</em>

<em />

After limb growth is complete, the gene is turned off. Repressive histone methylation marks would be associated with this state, such as the aforementioned H3K9me2/3 or H3K27me3.

2. Histone modifications are tightly linked to genome organisation. Histone methylation marks associated with repression such as H3K27me3 and H3K9me3 are associated with compact chromatin structures, which restrict the access of transcriptional machinery and other positive regulators. Conversely, histone marks associated with gene activation are associated with a more permissive chromatin environment that facilitates the binding of factors associated with gene expression. In the case of histone acetylation, the acetyl mark directly removes the positive charge of chromatin, relaxing its interaction with negatively charged DNA.

3. If the inappropriate activation of this gene caused a cancerous tumor, this gene would be referred to as an oncogene (or a proto-oncogene for the term before it is inappropriately activated).

Typically, there are two classes of genes that lead to cancer: tumor-suppressor genes and oncogenes. Tumor suppressor genes lead to cancer when their protective activity is reduced or demolished, leading to the production of cancer cells. Oncogenes lead to cancer when they become over active. Oncogenes are often genes associated positively with growth and proliferation, consistent with the gene in this example.

8 0
3 years ago
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