Homeostasis and Equilibrium Flashcards

Question

What is a common example of a cell membrane receptor? That we study

Answer 1

G protein coupled receptors (GPCR)

Answer 2

The hormone comes and binds itself to the cell surface receptor (GPCR). This triggers the release of a G protein which bonds with an enzyme 'adenylate cyclase', and activates it. This catalyses a reaction when ATP in the cell is converted into cAMP, which acts as a second messenger. The cAMP then acts as a catalyst for intracellular activity or biolofical effects in response to the info from the first messenger. cAMP is a common second messenger. It could have effects such as: Activiates proteins + enzymes Inhibits proteins + enzymes Altering gene expression etc.

Answer 3

These are hydrophobic hormones, and they can cross the cell membrane easily. Thus, unlike water soluble hormones, they don't need a cell surface receptor

Answer 4

Their receptors are in the cytoplasm or nucleus. They are typically called 'nuclear receptors' . The binding of the hormone to the nucleus receptor forces 'hormone reception complex' which goes into the nucleus and binds with the DNA. they DON'T need a second messenger, because they can just cross the bilayer

Answer 5

Hormones released down bloodstream, and travel throughout the body, carrying info between cells to regulate physiological processes. Each hormone is designed to interact with specific target cells that possess receptors for that particular hormone. These target cells can be locate d in distant organs or tissues. Thus, it allows for communication despite long distances

Answer 6

It is a steroid that acts as a hormone. They are cyclical chemical compounds made up of rings of carbon atoms that play an essential roles such as through looking at metabolism, immune response and reproductive. They are derived from cholestrol

Answer 7

For example, the steroid hormone testosterone passes through the plasma membrane, which then binds to a receptor protein in the cytoplasm, activating it. The hormone receptor complex enters the nucleus and binds to specific genes. The blood protein stimulates the transcription of the gene into mRNA, which can be translated into a specific pattern

Answer 8

It is a small, pea sized gland at the base of the brain. It tells other glands in your body what to do. It does this through making, storing and releasing hormones. Also known as the 'master gland'

Answer 9

Oxytocin and antidiuretic hormone (ADH)

Answer 10

It is a peptive (a compound consisting of two or more amino acids linked in a chain) hormone released by the posterior pituitary, and plays a significant role in childbirth and assisting with breast milk During labour, the cervix stretching will cause increased oxytocin released, which increases uterine contractions, further helping with childbirth, further causing the cervix to stretch, forming a positive feedback loop, as it keeps going until the cervix is stretched far enough for childbirth to occur Additionally, suckling at a lactating breast will send a signal to release oxytocin, which stimulates milk injections by contracting the cells which live in the breast. Thijs is a further positive feedback loop

Answer 11

It is a chemical produced which causes kidneys to release less water, increase uptake of water and decrease the amount of urine produced (to maximise amount of water) Main function is to increase H2O absorption

Answer 12

electrolyte/sodium - water balance

Answer 13

ADH is released as a response to an increase in plasma osmolarity, or a decrease in blood volume or a decrease in blood pressure. When this happens, ADH stimulates an increase in the amount of aquaporins in the kidney, to increase absorption of water, which thereby prevents loss of water --> prevents osmolarity increase again, and releases the water back into the body. This allows for decrease in plasma osmolarity and increase in blood volume and blood pressure

Answer 14

Calcium concentrations are so low that a dramatic increase will be considered a 'call to action' It has profound impacts on protein activity, interactions and conformation Calcium FLOODS into cells very quickly. In turn, changes cellular actions on all levels.

Answer 15

Glucose is the main source of energy for the brain (neurons). Additionally, glycogen stores in the brain is very little. Thus, we need glucose to be constantly circulating so that it can get to the brain --> brain can continue to function. When there is low blood glucose, brain doesn't have enough energy --> loss of brain function --> coma

Answer 16

Utilises passive transport through diffusion to enter cells. Cell membranes are semi permeable, however glucose can't cross membranes, and thus needs the assistance of glucose transporters

Answer 17

SGLT transporters GLUT transporters

Answer 18

These are typically seen in the small intestine & kidney. The small intestine is responsible for uptake of glucose from the blood. Meanwhile the kidney functions to reuptake the sodium and glucose from the blood Overall, these exist to assist in transporting sodium and glucose across a cell membrane Uses enerfy from the negative sodium ion gradient by the ATPase pump to transport glucose across membrane Essentially involves transport of sodium which allows for glucose to be transported as well?!

Answer 19

GLUT2 and GLUT4

Answer 20

They are mainly in the liver and pancreatic beta cells, and they don't rely on insulin for facilitated diffusion

Answer 21

They are mainly in the muscle and fat cells. These respond to insulin.

Answer 22

Problem is that glucose can reach high peaks or low throughs without additional glucose control. Thus if we only rely on glucose diffusion, it will provide a bad control of glucose. Thus, we need glucagon and insulin to add further control

Answer 23

Insulin generally promotes glucose uptake within muscle and fat cells, and also promote glycogen storage in the liver

Answer 24

Glucagon targets the liver to promote glycogen breakdown and thereby promote glucose release into the body. This is an important function during the fasting state of the body

Answer 25

This state occurs essentially after eating, and the nutrients and blood sugars have been absorbed in the system and are circulating During this state, blood sugar increases

Answer 26

During the fed state, mainly the mechanisms that attempt to maintain a stable blood sugar focus on lowering sugar through increasing its uptake into cells, to be stored. I.e. to the liver, fat and muscle cells. This is to prevent an extremely high blood sugar level and also allows for the cells to have enough glucose to function properly.

Answer 27

Insulin is secreted, which increases the amount of GLUT4 transporters on the cell membranes of cells. This increased GLUT4 results in more glucose entering the muscle cell --> enabling them to get the glucose required. However, if it was just reliant on simple diffusion, glucose entering the muscle will stop at a certain point because [glucose] in the cell = [glucose] outside the cell. Thus the idea of storing the glucose is important to disturb this equilibrium and ensure more and constant glucose entering the muscle cells --> glycogen etc.

Answer 28

Keeps glucose coming in the cell via passive transport Allows for storage of glucose into glycogen to be used for exercise or energy later on

Answer 29

During the fed state, fats take up glucose through GLUT4 and uses fatty acids to form triglycerides (fats) which can be used as an energy store Fat cells can just keep getting bigger with a continuous intake of glucose Once again, insulin increases amount of glucose absorbed

Answer 30

During the fed state, liver builds up energy stores in the form of glycogen and triglycerides

Answer 31

Typically occurs a few hours after eating and its the period when the body isn't receiving any dietary glucose or nutrition through food intake. During fasting, the body relies on stored energy sources, such as glycogen in the liver and the muscles Generally, during the fasting state, insulin will decrease but glucagon increases

Answer 32

Here, during fasting state, glycogen which was previously stored is used for energy to allow for exercise. Releases lactate from exercising muscles which can be then taken by the liver and used for gluconeogensis, which can then be released into the bloodstream to maintain blood glucose levels during fasting

Answer 33

Fat cells release stored triglycerides into glycerol and free fatty acids which can be used for energy

Answer 34

During fasting state, the liver aims to generate glucose to increase blood sugar levels (prevent hypoglycaemia). When there is decreased blood sugar levels on the outside of the cell, the GLUT2 transporters assist in transporting glucose formed through assistance of glucagon to catalyse the reaction from glycogen to glucose. The liver responds to the increased glucagon levels to up the levels of blood glucose

Answer 35

Produce enzymes to digest food Produce hormones insulin & glucagon to help maintain blood sugar control

Answer 36

The Pancreatic islets, also known as islets of Langerhans

Answer 37

Alpha cells (important) Beta cells (important) Delta cells Pancreatic polypeptide

Answer 38

Synthesise glucagon

Answer 39

Synthesise insulin

Answer 40

Glucose, amino acids, hormones, neuronal input etc.

Answer 41

Refers to the ability of beta cells to respond to various signals by generating electrical activity, leading to the secretion of insulin. This is critical for regulation of blood glucose levels in the body

Answer 42

They maintain a relatively stable resting membrane potential, at around ~70 millivolts (mv). This resting potential is primarily determined by the activity of the potassium channels, which move K+ ions outside of the cell --> inside of the cell is more -ve

Answer 43

GLUT2, ATP, K-ATP channel, VGCC (voltage gated calcium channels), Ca2+, insulin granules

Answer 44

Beta cells contain GLUT2, when blood glucose levels rise, glucose enters beta cells through these GLUT2 transporters. Results in increased production of ATP through glucose metabolism. This increased ATP level inhibits K ATP channels, causing them to close. As a result, K+ ions can't exit the cell --> membrane depolarisation (inside of cell becomes less negative) Membrane depolarisation then triggers the opening of voltage gated calcium channels (VGCC), which are sensitive to the membrane potential. Calcium ions then flow into the cell through these channels due to their electrochemical gradient The influx of Ca2+ into the beta cell cytoplasm triggers various intracellular signaling processes. It also involves activation of Ca2+ sensitive proteins, which in turn activate other proteins involved in the exocytosis of the insulin containing vesicles After insulin is secreted, the beta cell membrane repolarises --> returning to the resting membrane potential, which is facilitated by closure of Ca2+ channels and opening of K+ channels --> K+ ions leave cells --> repolarisation

Answer 45

Depolarization is the process by which the membrane potential becomes less negative, facilitating the generation of an action potential.

Answer 46

Around 10000 granules, in beta cells, however we only excrete 100 granules --> most likely because the rest is a backup, as this is an essential part of the biological process

Answer 47

It is a hormone coming from cells lining the small intestine, and acts as a key regulator of beta cells When eating, the body triggers secretion of GLP one which then gets into circulation as a hormone, and is picked up by beta cells --> priming beta cells for release of insulin from glucose digestion

Answer 48

This is an autoimmune disorder. In this case, the body recognises itself as being an invasive element and targets itself as part of the immune system and tries to destroy part of it. More specifically, it recognises beta cells as a hostile cell --> generates antibody against proteins that are present in beta cells including insulin Here, killer T cells go to kill all B cells in pancreatic islets Median age is 12 years old, and typically occurs in children. Includes symptoms such as weight loss, fatigue, frequent urination and excessive thirst

Answer 49

This is where beta cells dont work as well (could be due to prolonged exposure to high levels of glucose) --> reduced production of insulin Insulin resistance can also occur in cells --> less response --> high blood glucose due to inability for storage of glucose Symptoms include: slow healing of wounds, blurred vision, constant hunger, fungal infection, frequent urination, numbness of hands and feet