What is visual acuity?

Visual Acuity - The ability to tell apart points which is close together

This is a bit like the resolution of something, you talk about the resolution of an image or microscope. As far as a microscope, the resolution is the smallest distance at which two objects can be told apart.

In your eyes,  Rod cells give low visual acuity because many rods join to the same neurone which means light from two objects close together can't be told apart. In you eye, Rod cells are more sensitive, but cone cells (the other type of cells in your eyes) help you see more detail.

Sickle Cell Anaemia

Sickle Cell Anaemia is a recessive genetic disorder, it's caused by a mutation in the haemoglobin gene. This causes an altered haemoglobin protein to be produced. This means the red blood cells become sickle shaped (concave) - not the typical shape you're probably aware of. The red blood cell's concave shape means they can't flow through capillaries easily like normal red blood cells can so the capillaries can become blocked - blood flow is then restricted. This can also bring up so many more issues like organ damage and periods of acute pain.

Some people can be carriers of the sickle cell gene, amazingly, carriers of the sickle cell gene are partially protected from malaria. Because of this advantageous effect, the frequency of the sickle cell gene have increased. Unfortunately this means the likelihood of inheriting two copies of the allele are increased - overall, this means sickle cell anaemia is more prevalent in these areas.
 

What is a synapse?

When electrical impulses are fired around your body, they do so by travelling around in neurones as chemical/electrical impulses.


However, your neurones don't cover every inch of your body. To get over this issue, there are small gaps between the neurones - this is called the synapse. Technically speaking, it's a junction between the neurone and the next cell. , the gap itself is called the synaptic cleft. The neurone before the gap is given the name of a presynaptic neurone - it has a swelling on it called the synaptic knob. On the presynaptic neurone there's synaptic vesicles filled with chemicals called neurotransmitters.


When an action potential reaches the end of the neurone, neurotransmitters are released into the synaptic cleft. They diffuse across this gap and attach to the postsynaptic membrane - here they bind to specific receptors. When the neurotransmitter binds to the receptors, this could trigger an action potential, causing muscle contraction (perhaps) in the next cell. Alternatively, a hormone could be secreted if it's a gland cell.




Because these receptors are only on the post synaptic membrane, this makes action potentials unidirectional - i.e they travel in only one direction. If nerve signals travelled in multiple directions, things would get very confusing very quickly!

Organ's don't grow on trees.... #SciSparksAdvent Day 3

Well they don’t grow on trees but in the near future you may well be seeing stem cells grow a whole range of organs. Perhaps stem cells are known mostly for their ability to grow into any type of cell. This development although it’s comparatively new is pushing the boundaries of what’s possible; we’ve even managed to grow a new heart entirely from stem cells.

Between April 2013 and March 2014 nearly 5,000 people had organ transplants. Although one major problem we have is that sometimes the person’s own immune system detects that the organ is a foreign object and rejects it. The hope is that if the organ is made from your own cells the success rate will be much higher.

Currently around 120,000 people are waiting for an organ transplant - stem cell organs could mean organs would be available in days rather than potentially years. To grow a new heart (or any other organ), it all starts off with a donor organ that doesn’t necessarily have to come from a human. They then remove all the cells, this leaves the scientists with a protein scaffolding which is then repopulated with the patient’s own stem cells.

This image shows a new heart being grown in a lab

Scientists grow a heart

Scientists at the University of Pìttsburgh, PA have managed to grow a functioning mouse heart from pluripotent stem cells. These are adult stem cells that act like embryonic stem cells. The team achieved this by stripping the mouse heart of its cells and replacing them with human cells.  The heart then began to beat just as before. This could then lead to stem cells being used in the future for human organ transplants. Although there are a number of ethical issues surrounding the use of stem cells.  This technological advance could be used to replace heart tissue damaged during a heart attack.