kheredia's blog

Data was collected on November 19th, 2019 in the Biology lab at Umass Amherst in Amherst, MA. The subject of study was ,Gryllus spp., the common field cricket found in the Northeast. The goal of this data collection was to measure the frequency at which male Gryllus spp. exhibited courting activities or competitive behaviors while in the presence of another male, and a female. Thirty crickets were used for this experiment, 20 males and 10 females. Before the experiment began, the crickets were identified as either male or female, and placed in two separate containers by the observers based on sex.

There are three parts to the small intestine; the duodenum, the jejunum, and the ileum. In the small intestine, Carbohydrates are broken down into monosaccharides, Lipids are broken down into individual fatty acids, and Proteins are broken down into individual amino acids. All of these macronutrients are broken down into their simplest forms and absorbed through the walls of the small intestine, made up of simple columnar epithelial tissue. The Pyloric sphincter regulates passage of chyme into the small intestine, where chyme is the acidic fluid that passes from the stomach to the small intestine, consisting of gastric juices and partly digested food. The pyloric sphincter is a smooth muscle sphincter that regulates passage of contents through the stomach to the small intestine. When it is constricted: nothing passes, and when it is relaxed: allows small amounts of chyme to enter the small intestine. This is an important regulation because you pepsin is required to cleave proteins before they enter the small intestine, and will prevent the small intestine from being overwhelmed.

In the small intestine those acidic contents from the low pH of the stomach get passed here (chyme). It’s regulated at the pyloric sphincter. Pancreatic juices get secreted here which have those enzymes for each macronutrient that breaks it down to individual molecules so that it can move on. For carbs we have pancreatic amylase breaking carbs down and brush border enzymes lactase sucrase and maltase which break them down even further from disaccharides into monosaccharides. If the disaccharides can’t be broken down they can’t be absorbed! They’ll remain in the gut and create osmotic pressure which makes you bloated. They need to be broken into individuals. Their transport across the membrane is by secondary active transport and facilitated diffusion. They are also broken down prior to transport. For protein we have those proteases. Pepsin cleaves the protein, trypsin and chymotrypsin cleave them more, and FINALLY and carboxypeptidase cleaves then even more and makes them individual amino acids. Transport here is also through secondary active transport and facilitated diffusion. Amino acids then get secreted into the interstitial fluid and enter the bloodstream. Last- lipids are cleaved by the lipases to become individual fatty acids. This starts with emulsification. The globule of fat is emulsified by bile salts to be able to enter aqueous solutions. Otherwise, without these bile salts, it cannot enter. The bile salts act like detergent and break down the globule into smaller pieces. NOW, lipases can break them down into their individual forms. Once they’re individual fatty acids, they get packaged in these molecules called micelles, which diffuse into enterocytes. After this, the micelle’s get packaged into molecules called chylomicrons. So it’s like a box filled with something going into another box. So now the individual fatty acids packaged in the chylomicrons get secreted into the interstitial space and travel in lymphatics to the bloodstream because they’re too large.

The effects of ADH, Aldosterone, and Angiotensin II all increase blood pressure. AntiDiuretic Hormone (ADH) increases reabsorption of water, plasma volume, and cardiac output e.g. EDV and therefore blood pressure increases. In the Distal convoluted tubule, aldosterone determines the final rate of sodium reabsorption and therefore adjusts the sodium concentration in the bloodstream It’s a hormone so it’s regulated by the endocrine system. Aldosterone is secreted by the adrenal cortex of the kidney. High aldosterone means increased sodium reabsorption. Because water follows solutes, if we increase sodium reabsorption, water reabsorption also occurs. Though, this ultimately depends on expression of ADH, which we will get into...but for now, just assume if everything else is “normal,” increased aldosterone release increases sodium reabsorption and water as well. The increased sodium reabsorption would increase blood volume, blood pressure, cardiac output, increases EDV, and increases SV. It is important to know that blood pressure increases in response to more reabsorption of fluid, and the reabsorption of fluid is driven by the reabsorption of sodium.
In the collecting duct, we know that final reabsorption of water occurs here and is dependent on ADH. ADH adjusts the osmolarity of the extracellular fluid by reabsorbing water, and is secreted by the pituitary gland of the hypothalamus. If ADH is secreted, this will signal the insertion of aquaporins, which are the channels that allow water to pass and be reabsorbed in the medulla when it follows down its concentration gradient. Side note - but remember that the gradient water follows is basically anything with a lot of salt. Deep in the medulla, as discussed, is a highly concentrated area. So water follows salt as it reaches down there when its traveling in the collecting duct, and gets reabsorbed into the blood. But like I said, this is only if ADH is secreted and signals aquaporin insertion.

There are a few hormones involved in the regulation of digestion, but we’re only going to talk about a few of them. Gastrin stimulates the stomach and the small intestine. Histamine is another hormone, stimulates HCl production in the stomach (to acidify the contents). Secretin is a hormone that inhibits the stomach while also stimulating the small intestine. Cholecystokinin stimulates the small intestine and digestion but inhibits stomach. Secretin and cholecystokinin are active during the intestinal phase of digestion (they’re stimulating the small intestine and not the stomach). Undigested food enters the duodenum and inhibits gastric emptying in the Intestinal phase. The distension from the gastric phase leads to gastrin release in the blood. Secretin and cholecystokinin inhibit stomach activity until contents are digested.

Phase 1 is the cephalic phase: neural control of the GI tract. This is when we see, smell, think of food and our mouth waters. It’s us thinking about food and getting hungry. The parasympathetic branch stimulates digestion (think rest and digest from skye’s class, easy to remember). The sympathetic nervous system would be more of energy expenditure while parasympathetic is storage.
Phase 2 is the gastric phase: mechanical, endocrine, and neural control. This is when food enters the stomach, and its activated by stomach distension (when the stomach fills up and stretches because of the food that’s in it) as well as chemicals in the food. This stimulates nerves as well as hormones that help regulate digestion (endocrine factors). The gastric phase also has something called short reflexes. They’re neural reflexes that don’t go to the brain. It connects one part of the GI tract to another part so signals can be transmitted quickly. Long reflexes also happen in the gastric phase. They go via the medulla and the vagus nerve that can go to other parts of the GI tract but they are processed through the brain. Gastrin is a hormone that comes from G cells (involved in endocrine control). Note: ALL THREE OF THESE PHASES CAN BE INHIBITED
Phase 3 is the Intestinal phase: mechanical, endocrine, and neural control. This phase is stimulated by partially digested food that enters the small intestine. We see inhibition (negative feedback) the more acidic the intestine, the less contents are going to be ejected into the intestine. Hormonal control: gastrin released in the stomach and stimulatory effects of others.

From the esophagus, we get to the stomach, where more mechanical digestion happens (the stomach churns and moves around to further break down food) and more chemical digestion occurs simultaneously. The stomach secretes gastric juices to help break apart the food further and into the nutrients we need that get absorbed later on in the digestive system. The movement of food within the stomach is called segmentation; it’s the mixing motion that basically sloshes food around haha. Within the stomach, we have gastric pits that hold important cells which provide different things to the stomach. Parietal cells are found in the gastric pits, and they secrete hydrogen ions (Hydrochloric acid) that enters the lumen of the stomach to acidify the content. We also have chief cells that secrete an enzyme called pepsinogen that becomes pepsin and helps breakdown proteins. Pepsinogen starts off as a pro enzyme, which is an enzyme that is not yet active, into the stomach. Pepsinogen is then activated by the low pH in the gut and becomes pepsin. Pepsin is what breaks down the proteins found in the stomach. There are also surface epithelial cells that produce a thick coating of mucus, which protects the gastric mucosa from acid and enzymes. Surface epithelial cells also secrete bicarbonate.

The digestive system helps us get nutrients from the outside world into our bodies. Technically, the digestive tract is the outside of the body (the mouth and the anus are the holes at either end). So to begin, we’re gonna go over the anatomy of the digestive system, we start at the mouth, which is where ingestion and mechanical breakdown (chewing) of food happens. The mouth and the esophagus are made up of stratified squamous epithelial tissue because the goal here is protection, not absorption or secretion. Saliva moistens the food and starts to break it down (chemical breakdown by an enzymes called amylase (breaks down carbs, is also known as CHO) and lipase (breaks down lipids). Saliva also helps lubricate the food and this helps it travel down the throat more easily.

An animal behavior seminar lectured by Fiona Cross detailed a few studies performed on the behavioral strategies of jumping spiders. While doing research an America, she mostly paid attention to Portia Africana, a tiny species of spider with incredible cognitive abilities when you consider its brain is smaller than a thumbtack.

She detailed the results from the studies done with Portia, revealing to the audience that the spider displays acts of specialized behavior with several strategies that allow it to be so versatile. For example, Cross described how throughout her studies, Portia paid attention to prey type and prey number with each consecutive trial using lures as bait. Portia would hesitate to approach prey if there were less of them, and would find no interest in the leaves used as the alternative lure in the trials it was subjected to.

I also learned some interesting facts about Portia compared to other species of spider: One of them was that compared to another jumping spider, Nephila Clavipes, Portia’s eyesight is superior. Another learned fact about Portia was about its aggressive behavior. Portia uses mimicry as a strategy to lure and attack other spiders. When it encounters other spider nests, Portia will act like prey stuck on its enemy’s web, by mimicking the vibrations of a struggling insect. When the other spider approaches closely enough, Portia will attack and ingest the spider. m

Because of how interesting this last piece of information was before she closed the seminar, a future proposal for an experiment involving Portia could be its frequency of aggressive mimicry with live spiders of a different species compared to its own cannibalistic species.

Today’s seminar, lectured by Fiona Cross, involved insight from studies done on behavioral strategies of jumping spiders. While doing research here, she mostly paid attention to Portia Africana, a tiny species of spider with incredible cognitive abilities when you consider its brain is smaller than a thumbtack. Results from the studies done with Portia revealed that it displays acts of specialized behavior with several strategies that allow it to be so versatile. For example, Fiona described how throughout her studies, Portia paid attention to prey type and prey number with each consecutive trial using lures. Portia would hesitate to approach prey if there were less of them, and would find no interest in leaves used as the alternative lure in the trials it was subjected to. I also learned some interesting facts about Portia compared to other species of spider: One of them was that compared to Nephila Clavipes, Portia’s eyesight is superior. An even better, more interesting fact about Portia I learned was its aggressive behavior using mimicry as a strategy to lure and attack other spiders. Portia, when encountering other spider nests, will pretend to act like a helpless insect stuck on the web by mimicking the vibrations of a struggling bug. When the other spider approaches closely enough, Portia will attack and eat the spider. Because of how interesting this last piece of information was before she closed the seminar, a future proposal for an experiment involving Portia could be its frequency of aggressive mimicry with live spiders of a different species compared to its own species (because Portia is also known to display acts of cannibalism).