D3.3

Question 1

Homeostatsis and Feedback

Hyperglycaemia?

Answer 1

• Refers to high concentations of glucocse in the blood strem.
• The initial sympton caused by diabetes.
• The high solute conc. causes feelings of thirst & symptons liks blurred vision & fatigue

Question 2

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Thermoregulation?

Answer 2

• Refers to the mechanisms used to control body temp within a narrow range.
• Important component for maintaining homeostasis (only done by endotherms - birds & mammals)
• Internal body temp changes in extreme external environments and as a result of metabolic processes that raise body temp.

Question 3

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Vasoconstriction?

(Think about blood)

Answer 3

• When body temperautre dips due to cold environments, the muscular wall of arterioles contract which reduces blood flow to the capillaries and keeps it in the arterioles.
• The lower blood flow in the capillaries means less blood near the skin meaning less heat loss through skin to cold environments.
• Allows us to retain our metabolic heat.

Question 4

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Vasodilation

Answer 4

• When our body is overheating (due to high metabolic rates) it’s helpful to release heat to the environment (generally requires the environment to be cooler)
• The arteriole wall rexales allowing lots of blood to flow to the capillaries.
• This sends blood close close to skinallowing heat to transfer through the skin to the environment, resturning body temp to set point.

Question 5

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Thyroxine?

Answer 5

• A hormone involved in thermoreulgatoin.
• Metabolic processes (especially cell resp.) release heat, so increasing metabolic rate helps increase body temp.
• The hypothalamus detects the increased temp & sends TRH (a separate hormone) to the anterior pituitary.
• The pituitary releases the hormone Thyroid Stimulating Hormone which travels to the thyroid gland, releasing Thryoxine.
• Thyroxine travels to body cells to increase metabolic rate.

Question 6

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Internal Conditions needed to be in Homeostasis

(Four)

Answer 6

1. Osmolarity of blood (water & solute balance)
2. Body temperature
3. Blood Glucose Levels.
4. Blood pH.

Question 7

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Alpha vs Beta Cells in the Pancreas

Answer 7

• Both of the hormones involved in blood-sugar regulation are released by cells in the pancreas in clusters of endocrine cells called the Islet of Langerhans.
• Beta Cells in the Islet: release insulin in response to high blood sugar (following meals)
• Alpha Cells in the Islet: Release glucagon in response to low blood sugar (following fasting)

Question 8

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Blood Glucose Hormones: Insulin

Answer 8

When released, it lowers blood glucose in the blood.

Does this by:
1) Triggering body cells to uptake glucose from the blood to use in cell resp.
2) Triggering the liver to absorb glucose & convert it to glycogen for storage.
3) Can also trigger adipose (fat) cells to uptake glucose and convert it to triglycerides for storage.

Question 9

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Blood Glucose Hormones: Glucagon

Answer 9

• Released when blood sugar/glucose is lowhe liver.
• This triggers the conversion of glycogen to glucose, which is released into the bloodstream to increase glucose levels and faciliate cell resp.to continue between meals.

Question 10

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Cause of Symptons of Type 1 Diabetes

Answer 10

• The result of the beta cells of the pancreas not producing insulin, due to being attacked by the immune system (autoimmune disease).
• The lack of insulin means that cells don’t take up glucose, increasing levels in the blood, causing cells to not be able to complete cell resp.
• This requires insulin to be administrated to body (often via pump)

Question 11

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Causes and Symptoms of Type 2 Diabetes:

Answer 11

• The result of a reduction in cell response to insulin (desensitization), despite insulin being released by the pancreas.
• Can be due to damage to insulin recepetors or glucose transporters, often after long term overuse due to diet and other risk facotrs.
• Over time insulin levels can decline due to overuse of alpha cells.

Question 12

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Uncoupled Cell Respiration for Thermoregulation

(Heat production)

Answer 12

• Brown Adipose tissue is a specialized form of fat tissue with more mitochondira and less stored fat.
• In these cells, cell resp. is altered - the electrion transport chain utilizes different transport proteins that create heat rather than ATP.
• This increase body temperature in cold environments.

Question 13

Kidney Structure

Osmoregulation?

Answer 13

• The control over water content in the blood, so that blood osmolarity remains in homeostasis despite large swings in water intake and loss.
• One of the two primary functions of the kidney, primarily done through the Loop of Henele & collecting duct of the nephron, which reabsorb water according to ADH’s instructions.

Question 14

Kidney Structure

Excretion?

(The second function of the kidney)

Answer 14

• The removal of waste products/excess ions from the blood to help bodies have the ideal solute concentrations and limit toxic waste circulation.
• Most of natural waste production comes from the break down of amino acids for energy & urea.
• Medications & non-digestible particles in foods (e.g., dyes) can also be filtered out by kidney.

Question 15

Kidney Structure

Nephron?

Answer 15

• Filerting units - 1.25million of which make up the kidney.
• Each nephron is made up of many different cells & cell types (very complex)
• Rather than blood being filtered once, it’s filtered 1.25million times when it flows through the kidneys.
• This ensures effective blood purification

Question 16

Kidney Structure

Ultrafiltration?

Answer 16

• Over filtration based on size rather than necessity of removel.
• When blood first enters a nephron, most small solutes & water is initially filtrated out of the vessles (glomerulus) due to pressure entering thinner capillaries and into the filtrate.
• This includes some solutes belonging in the blood and more water than should be removed, so needed things will later be reabsorbed into the blood.

Question 17

Kidney Structure

Efferent Arterioles?

Answer 17

• Thinner than the afferent, creating a ‘bottle-neck’ effect that exerts pressure on the blood in the glomerulus capillaries.
• This causes small solutes and water to squeeze out of the vessels.
• Note that the renal artery brings blood to the kidney. This artery branches off into afferent arterioles that deliver blood to each nephron.
• The blood then moves through a thin tangled caipllary bed called the glogmerulus and then collects back in the efferent arterioles to continue its pathway.

Question 18

Kidney Structure

Filtrate?

Answer 18

• The initial fluid squeezed out of the blood at the glomerulus and collected in Bowman’s capsule.
• A water substance that contains wastes, ions, glucose and water.
• Some of the components of filtrate will be reabsorbed and what remains will become urine.
• Larger substances like proteins and blood cells shoudn’t filter out, and therefore don’t enter filtrate.

Question 19

Kidney Structure

Reabsorption?

Answer 19

• As ultrafiltration is by size, many ‘good’ small things must be returned to the blood so as to not be lost in urine.
• All the glucose that is filtered into the filtrate is reabsorbed in the proximal convoluted tubule (has many microvilli and co-transport pumps to aid the process).
• Many ions & water is also reabsorbed.
• Moves through the proximal tubule cells to a pertibular capillary surrounding the tube to join the renal vein & exit the kidney.

Question 20

Kidney Structure

Microvilli?

Answer 20

• Microscopic projections (finger-like) that greatly increase the surface area of the membrane which increases the rate of transport reabsorption.
• They cover the cells of the proximal convoluted tubule on the inside that is facing the tube that the filrate runs through.

Question 21

Kidney Structure

Parts of a Nephron: Glomerulus

Answer 21

• A capillary bed that branches off from the afferent arteriole.
• Has thin vessels and tangled/ overlapping - making it a small ball within the cortex of the kidney.
• The pressure from the efferent artiole causes water and small solutes to push through fenestrations (pores/gaps) in the glomerulus capillaries.

Question 22

Kidney Structure

Parts of Nephron: Bowman’s Capsule

Answer 22

• The circular tissue that surrounds the glomerulus & connects to the proximal convoluted tubule & remaining tubing of the nephron.
• Includes specialized cells called podocytes & a basement membrane that traps larger molecules (proteins and blood cells) so they don’t enter the filtrate.
• The filtrate gathers in the capsule and proceeds to the proximal convoluted tubule.

Question 23

Kidney Structure

Parts of a Nephron: Proximal Convoluted Tubule

Answer 23

• Filtrate travels from Bowman’s capsule to proximal convoluted tubule.
• Selective reabsorption occurs in the proximal convoluted tubule, including all glucose, most salts & ions & lots of water (not watse products)

Question 24

Kidney Structure

Role of Fenestrations in the Glomerulus

Answer 24

• The walls of glomeruli have fenestrations (an adaption in capillaries with higher exchange needs - small slits/openeing in the thin walls - gaps between cells)
• Allows for the squeezing out of water & solutes under the pressure of efferent arterioles.
• The fenestrations mean small molecules leave through the fenestrations rather than the bilayer, allowing for faster & more movements out of the capillaries.

Question 25

# Kidney Structure The Importance of the Basement Membrane

Answer 25

* A layer located between the **glomeruli & bowman's capsule**, containing cells (podocytes) along it that are connected by slit diaphragms. * Some larger proteins/red blood cells could slip out of the capillaries of the glomerulus but **not through the basement membrance & podocyte network**. * This **ensures the proteins and cells go back to the efferent arterioles**, as there's no process to reabsorb proteins, it's crucial they don't end up in the filtrate.

Question 26

# The Loop of Henle The Loop of Henle? | (It's purpose)

Answer 26

* After the filtrate leaves the proximal convoluted tubule - around 70% of the water that needs to be reabsorbed has been returned to the blood. * The filtrate then travels through the Loop of Henle, which **uses passive and active transport to further reabsorb water from the urine to the blood** * This is done by **sustaining a conc. gradient by salt transport that faciliates osmotic movement of water out of the filtrate**. * This allows for the **needed return of water to maintain osmolarity of the blood.**

Question 27

# The Loop of Henle Aquaporins?

Answer 27

* Specialized channel proteins that **faciliate rapid diffusion of water** through membranes. * In the collecting duct of the kidney, these sit in vesicles & **are only merged into the plasma membrane in response to ADH.** * Meaning, the **number of aquaporins in the collecting tube changes depending on the precise specific needs for reabsorption** at that time.

Question 28

# The Loop of Henle Countercurrent Multiplier System?

Answer 28

* As water flows through the loop, **a conc. gradient is maintained** - allowing water to be reabsorbed out of the filtrate. * Done by **actively transporting salt out of the ascending limb to maintain a hypertonic conc**. inside the tubule at every place along the Loop --> water continuinnly dissues out by passive osmosis. * This **diffusion of water out** of one side while salt is pumped out of the other, faciliates the countercurrenct multplier system.

Question 29

# The Loop of Henle Causes of Fluctuations in Blood Water Content

Answer 29

* Can be variable due to both large consumption of water or too little/loss of water (dehydration). * Sweat releases water for thermoregulation but can negatively impact osmoregulation. * Diarrhea releases water from the large intestines, preventing it from entering the blood stream.

Question 30

# The Loop of Henle Parts of the Loop of Henle: Descending Limb

Answer 30

* Transports filtrate down the tube. * **Very permeable to water but impermeable to solutes**. * Consequently, **water leaves the filtrate in this limb.** * Occurs as a result of the **filtrate remaining hypertonic to tissue/blood** around it.

Question 31

# The Loop of Henle Parts of the Loop of Henle: Ascending Limb

Answer 31

* As water exits the filtrate in the descending limb, the remaining **filtrate has lower water potential, making water less likely to leave**. * To prevent water movement from stopping, the ascending limb is **not water permeable**, but **salt permeable** and salt is **actively transported out of the filtrate**. * This **reduces the solute concentration** so that **water potential increases** and water continues to leave.

Question 32

# The Loop of Henle Function of the Distral Convoluted Tubule?

Answer 32

* After filtrate leaves the loop, it moves through the distral convoluted tubule (NOT part of the loop). * Some more fin tuning of the blood content occurs, with **selevtive reabsorption of salts & ions and even further secretion of hormones and wastes** (adding more things from the blood to the urine).

Question 33

# The Loop of Henle Function of the Collecting Duct?

Answer 33

* There needs to be additional reabsorption of water in the event of dehydration. * This homeostatic refinement occurs via the collecting duct, which **reabsorbs more water when ADH levels are high during dehydration**.

Question 34

# The Loop of Henle The Importance of Active Transport in the Loop of Henle?

Answer 34

* As the filtrate moves down the descending limb, **water needs to leave by osmosis**. * This requires the **environment surrounding the loop (medulla tissue and blood supply) to be hypertonic to the filtrate** (less solutes). * This is accomplished by the **ascending limp actively transporting NaCl out of the filtrate to the surrounding tissue, mainting the concentration gradient needed for the passive flow of water out of the descending limb**.

Question 35

# The Loop of Henle ADH and Aquaporins in the Collecting Duct

Answer 35

* When **ADH binds to receptor cells in the kidney, it triggers the merging of vesciles containing aquaporins** into the **collecting cell membrances facing the lumen** (where the filtrate is) * The **increased no. aquaporins allows more water to be transported** out of the urine & into bloodstream. * If **ADH is absent/los, few aquaporins are in the collecting duct** keeping more water in the urine.

Question 36

# The Loop of Henle Adjustments to Blood Supply during activiy

Answer 36

* An adaption to regulate our metabolic needs: **Adjust blood flow to organs based on activity level**. * Arteries can vasodialte to allow more blood flow, or vasconstrict to reduce blood flow to the organ. * The **skeletal muscles & digestive tract tolerate extremes** during activity & restrict to the digestive system. * The brain & kidney can however tolerate minimal changes, but kidneys do get reduced blood flow during sleep.