Learning diary blog 5

The chapters most important topic was hypothalamus because it is the source for homeostasis. It for example controls the autonomic nervous system. It is the independence part of nervous system which is not conscious controlled, and it consists of two divisions. First is called sympathetic division. It is important in threating situation. It gets the physiological responses to increase, for example head rate, blood pressure and the eyes expands. The other is called parasympathetic division. After the threating situation it decreases heart rate and blood pressure. Those divisions goals are incompatible, so both can not be stimulated strongly at the same time.

Hypothalamus controls the posterior and anterior pituitary. In the posterior pituitary is the largest hypothalamic neurosecretory cells which are called magnocellular neurosecretory cells. Those cells release two chemical substances into bloodstream that are oxytocin and vasopressin (antidiuretic hormone ADH). Vasopressin controls the blood volume and salt concentration. Anterior pituitary hormones impact to the gonads, the thyroid glands, the adrenal glands and the mammary glands by bloodstream. Parvocellular neurosecretory cells control the anterior lobe.

One example of the function of the hypothalamus can be seen in the communication between the kidneys and the brain. After a several different chains of activity hypothalamus receives a stimulus which causes an increase in ADH production which in turn make us feel thirst.

One interesting topic from the topis is the enteric division of the autonomic nervous system. It is weird to think that there is a system in our middle body which consists of two networks and controls our transportation and digestion of food with millions of neurons. However, even thought the enteric division is mostly autonomous, it also receives messages from the brain via axons.

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Learning diary blog 4

Chapter 6 taught new things about neurotransmitters, for example that they are assorted in three major classes: amino acids, amines, peptides. They must have three identifiable features for the molecule to be a neurotransmitter. First, the molecule must be stored in the presynaptic neuron and synthesized there. Second, during the stimulation the presynaptic axon terminal release the molecule. Third, the presynaptic neuron releases a neurotransmitter and produces the response. After that the molecule must make a response in postsynaptic cell, which mimics the response of the neurotransmitter.

The neurotransmitters can be localized in several ways. One way is immunochemistry where the transmitter candidate can cause an immune response that generates specific antibodies which be chemically tagged with colourful marker. After this the antibodies are injected to brain tissue section. They highlight cell types that have the specific transmitters. Molecules can be localized by the different antibodies that are marked with different colours.

Other method is called in situ hybridization, ISH. The method finds the specific mRNA strands by binding complementary nuclei acid strands to these mRNA strands. Every polypeptide synthesize has unique mRNA molecule. In the method can be used colourful fluorescent molecules, then it is called FISH. The third alternative is to make the probes radioactive. Then we can monitor the distribution of radioactivity. This method is called autoradiography.

It was interesting to read about the different neurotransmitters, specially catecholamines and serotonin, and their limiting factors. The structures of different neurotransmitters are quite complex and their synthesizations are also quite hard to remember.

The most interesting part of the chapter was the one about G-protein coupled receptors and effectors because it gathered well the previously learned information about it but also explained well the new ones. For example, the shortcut pathway and second messenger cascades clarified well, how the different G-protein-coupled receptors affect on different effector proteins.

The chapter taught in its entirety that the neurotransmitters are small parts of huge chain of events. Neurotransmitters causes fast and slow chemical changes and some of them can active more than one subtype of receptor while some of the neurotransmitters have their own receptors but converge to affect the same effector system.

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Learning diary blog 3

The chapters 8 to 10 seemed to separate from the previous ones by including more examples which made it more interesting. The basic mechanisms and anatomy of eye and palate was already familiar but the sensory processes itself were almost completely new. The difficult part of the chapters was the transduction mechanisms on different receptors. There are lot of similarities between them but also many little differences which confuse the entirety. For example, the ion channel response differs between G-protein-coupled neurotransmitter receptor and photopigment. Also, the names for different structures are sometimes hard to remember, for example the different parts which belongs to process, where light flows from photoreceptors to optic nerve; 1. photoreceptors (in human eye rod or cone)à(horizontal cells) 2. bipolar cells à (amacrine cells) 3. ganglion cells and their axons à out of the eye to brain.

The palate particularly seems interesting; how it can be possible that we can recognize so many different odours? It was new that tongues different parts are specialized to different odours, for example tip of the tongue recognize most to the sweetness. Anyway, the parts are sensitive to other odours too, not only the odour it is specialized to. In the tongue is papillae which consist of taste buds. It was interesting that different odours get the depolarization on different ways, for example in sourness, HCL dissolves and H+ can bind to and block K+ channels. Potassium’s permeability decreases and happens depolarization.

Eyes structure was reviewed properly in the book. It was interesting to see how the image is formed in the retina and which issues affect to form the picture in the wrong place and how it can be fixed whit different lenses. If you do not see close properly and have hyperopia you need lenses which are convex. In turn, if you do not see far and have myopia, you need concave lenses.

It like to dive eyes open, so it was nice to know why everything looks blurry underwater. It causes of lights speed in medium if it quite same than lights speed in eyes structure the force of cornea ends and comes blurry.

What kind of things can be done by transferring different receptor cells from place to another? Or could it be possible for example to confuse our rods and cones to do the opposite as they should with drugs; cones would work in low light and rods in daylight?

Also, it sounds interesting and somehow difficult to imagine that “We see because our eyes have photoreceptors. If our tongue had photoreceptors, we might see with our mouth.”

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Learning diary blog 2

The third lecture mainly focused on synaptic transmission and topics around it. It recalled old familiar things but also taught new ones. The basic principle of synapses is that there are synapses because the information cannot just jump over the gap between them two neurons.

We started with the basics of synaptic transmission and defined the main structures: Post-synaptic and pre-synaptic neuron and axon which conducts the signal aka action potential to synapse. The one new information was that the action potential is always the same: discrete and binary even it branches to thousands of target cell. One question which came to mind was that, how the action potential can be always the same, how does it retain its form and value even it is delivered to one target cell or then to 1000 cells?

This action potential is so important because it includes the information which must be delivered. When the action potential arrives to axon terminal and depolarizes the presynaptic membrane the Ca2+-channels open and the Ca2+-ions will flow inside. This concentration change causes the vesicles to release the neurotransmitters to synaptic cleft. To calculate the reversal potential there is this formula called Nerst equation which was familiar already but the new one was Goldman equation which gives the membrane potential when the concentrations and permeabilities are known: Goldman equation (reference: lecture slides)

It was new that action potential can be generated with microelectrodes. The action potentials frequency can be controlled by electrical current. If the electrical current is continuous and
just goes above threshold, it generates action potentials which frequency is one Hertz. If the current increases the frequency increases too. A new concept is the Voltage-gated sodium channel, which properties explains action potentials properties. I find the optogenetics sounds interesting. How it can be possible to generate action potential with genes and light? Can it be used to form certain emotions depending on the light.

The release of neurotransmitter from vesicles were quite understandable but secretory granules is little bit unclear. Does secretory granules store only peptides or also amino acids and amines and does it have similar structure as vesicles so the neurotransmitter release is also similar?

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Learning diary blog 1

The second lecture started with familiar topics from previous courses, such as, different organelles in soma and brief explanation about DNA formation and gene expression. One question which came to mind was that, why there are two different places for protein synthesis, on a free ribosome and on rough ER?

Another interesting question which expressed on the lecture session was about what would happen if there are not energy available? We were given two examples, working of natrium-kalium pumps and action potential. I was just wondering does these organelles need energy themselves?

On the lecture we were also talking about the axon terminal and about how the presynaptic axon terminal is hanging on the postsynaptic dendrite and the answer was the glia cells. The term glia cell is familiar, but their structure isn’t that much. For example, are they much more inflexible than neurons so that they can support well?

In the first reading assignment there were many familiar concepts for example, protein synthesis, action potential, DNA, RNA, transcription and translation, cell structure and plain neuron structure like axons and neurons. By reading I could recall the concepts and get to know them more detail. New information was for example, that the protein synthesis can happen in two different ways in two different places – free ribosome and rough ER.

I can particularly remember from the reading assignment the astrocytes which are the most common glia cells. These cells fill most of the empty space between neurons and take care and regulate the chemical content, for example concentration of the potassium in the extracellular.

Overall, the book is informative and well-made but sometimes it is little bit off topic. I found that the beginning could have gone a bit faster straight to the topic.

I also learned a little bit more about the brain functions, such as signals and structure from prerecording. For example, signals of eye go to back part of the brain and the white matter connects the different parts of the brain. This information can be investigated for instance with X-ray, MRI, MRA or PET imaging.

 

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