Unit 5 - Homestasis

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What is homeostasis?

Our body’s tendency to maintain internal conditions despite external conditions

How does our body react with homeostasis?

Physiological responses: -Internal chemical reactions. ex. breakdown and production of glucose to regulate blood sugar levels

-Unconcious physical changes. ex. sweating, shivering

Behavioural responses : -Carry out a conscious physical change/An action an organism takes to keep its internal environment stable, ex. seeking a warm spot when cold, or eating when hungry

How do we react to overheating?

• Physiological : -sweating, dilation of blood vessels, thirsty

• Behavioural: -drink water, find shade

How do we react to frostbite?

• Physiological: -shivering, constriction of blood vessels

• Behavioural: -putting on gloves, seeking places with warmth, moving around to create heat

What is a feedback mechanism?

• a process where the output of a system influences its input

• in the context of homeostasis, it is used to maintain a stable internal environment by counteracting or amplifying changes

What is a negative feedback loop?

• process which stabilizes itself by reducing its output when the output’s effects are too great

What are some examples of negative feedback loops?

• Body temperature

• Breathing

• Water balance

• Blood sugar

• Thermoregulation

What is thermoregulation?

• Biological process of maintaining a stable internal body temperature.

• Typically around 37°C in humans.

• Works by balancing heat production with heat loss.

• Heat loss through mechanisms like sweating.

• Heat production through mechanisms like shivering.

What is osmoregulation

• Osmoregulation is the process of maintaining the body’s water and salt balance.

• Keeps levels of water, ions, and solutes stable inside the body.

• Prevents the body from becoming too diluted (too much water) or too concentrated (too little water).

• Mainly controlled by the kidneys.

• Helps maintain proper blood pressure and cell function.

How it does it:

• Kidneys filter the blood and adjust how much water is reabsorbed or released.

• Too much water → kidneys make dilute urine (release more water).

• Too little water → kidneys make concentrated urine (save water).

• ADH hormone tells kidneys when to conserve or release water.

How blood pressure is affected:

• More water kept in the body → higher blood volume → blood pressure increases.

• More water released in urine → lower blood volume → blood pressure decreases.

Why is osmoregulation important in humans?

• It acts as our mechanism to regulate osmotic pressure

• It balances our water and salt, which we need

• Without osmoregulation, there would be a lot of toxic waste and water in humans

• We live on land and lose water constantly through breathing, sweating, and waste. We must continuously replace this lost water and regulate salts to keep our internal environment balanced.

What is osmotic pressure?

• Osmotic pressure is the force created by differences in solute concentration across a semi-permeable membrane.

• It pulls water from an area of low solute concentration to high solute concentration.

• Higher solute concentration = higher osmotic pressure.

• Helps control the movement of water in and out of cells.

• Important for maintaining cell shape, fluid balance, and overall homeostasis

What is a positive feedback loop?

a process where an initial change triggers a response that amplifies the original change

Examples of positive feedback loops

• childbirth

• blood clotting

What is excretion?

the process of removing metabolic waste products and other toxic substances from the body

Why do we excrete?

• To function, it is essential to excrete waste from cells and the body in general

• To maintain homeostasis, we must excrete to regulate our ionic balance and pH balance

What are the two main functions of the excretory system?

• Regulates fluids and waste

• Concentrates (gathers) waste and expels it from the body

What do we excrete?

• certain metabolites must be eliminated, like nitrogenous compounds (since nitrogen is bad for us)

• When the body processes things during metabolism like proteins etc, it produces waste molecules

What is waste?

• When we break down nitrogenous waste products (amino acids and nitrogenous bases from eating certain animals), they turn into amine groups, which are toxic waste.

Ammonia:

• Product of deamination (removing N⁺ group).

• Results from breakdown of proteins.

• Occurs in liver.

Urea:

• Ammonia produces it.

• Occurs in liver.

Uric acid:

• Formed from the breakdown of amino acids.

Single-celled organisms

• Have an advantage in excretion because they have a high surface area, so they use simple diffusion only.

• They are always in contact with the external environment.

• Their internal environment is hyperosmotic to the surroundings.

• They have contractile vacuoles that pump out excess water to expel it.

What challenge do single-celled organisms face?

• Because they are directly exposed to the external environment, any change in surrounding solute concentration causes immediate osmotic stress.

• This can lead to potential cell damage in single-celled organisms.

What are complex organisms?

• Most complex organisms do not have constant contact with the external environment

• Therefore, the excretory system takes on different forms to help excrete since they are in contact with the external environment, making it harder to excrete

What organs help us excrete?

Lungs:

• Excrete carbon dioxide through exhaling

Liver:

• Converts amino acids to urea to excrete

Large Intenstine:

• Removes waste

Kidneys:

• Filters blood and removes waste

What does the Human Urinary System do?

• Eliminate waste products and foreign matter from the body

What is the Human Urinary system composed of?

• Kidneys

• Ureters

-Transport urine from kidneys to bladder

• Bladder

-stores urine

-releases urine during urination

• Urethra

-carries urine out of bladder

What are the 3 main structures of the kidney?

• Cortex

  • Outer layer of the kidney

• Medulla

  • Inner layer of kidney

• Renal Pelvis

  • Hollow cavity that connects the kidney to the ureter

What are the 3 main functions of the kidney?

• Remove waste

• Balance blood pH

• Maintain water balance

What is a nephron?

• Tiny part of kidney

• Filters waste from the blood (in the kidney)

How does blood filtering occur in the nephron?

• Begins at the glomerulus (which is surrounded by bowman’s capsule)

• Glomerulus receives blood from affarent arteriole, once filtered, it exits through efferent arteriole

• Blood is finally carried to peritubular capillaries

How does the filtering of certain components occur in the nephron?

High blood pressure in the glomerulus pushes some components through the semipermeable membrane into Bowman’s capsule.

• These components enter the proximal convoluted tubule in the renal cortex.

• The filtrate descends into the medulla through the loop of Henle.

• It rises into the distal convoluted tubule.

• At this point, it is urine and goes into the collecting duct to the renal pelvis.

• By this point, all non-waste substances should have been reabsorbed.

• The ureter empties the remains into the bladder.

• Takes water, ions, small nutrients, molecules (amino acids, glucose), nitrogenous waste.

• Does not take blood cells, platelets, or plasma proteins, which continue through the capillaries.

What are the steps of the formation of urine?

1. Filtration

2. Reabsorption

3. Secretion

What happens in the reabsorption step in the Nephron?

• Some components entering Bowman’s capsule are not waste and must be reabsorbed in the proximal and distal tubules.

• Ions are reabsorbed at the proximal convoluted tubule and returned to body cells.

• Specialized ion pumps (proteins) transport sodium (Na⁺), and when sodium is reabsorbed, chlorine (Cl⁻) and bicarbonate move with it.

• Throughout the proximal and distal tubules, glucose, amino acids, salts, and water are reabsorbed to different extents.

• Reabsorption continues until everything needed is fully reabsorbed; excess is excreted in the urine.

What happens in the secretion step in the nephron?

• Waste products enter (are secreted in) the tubule to be removed as urine

• Wastes are secreted at several points during the urine formation process

At the Proximal Convoluted Tubule:

• Urea, Uric acid, Creatine, some drugs, H+ and NH4+

Loop of Henle:

• Urea

Distal Convoluted Tubule:

• -H+, K+, and NH4+ (ammonium)

What are terms for the different concentrations? Specific to osmosis

• Solution with a higher solute concentration is Hyperosmotic

• Solution with lower solute concentration is Hypoosmotic

• Balanced : isoosmotic

Why is osmoregulation and excretion connected?

Osmoregulation keeps water and ion levels stable.

Excretion removes toxic wastes.

Both happen in the kidneys in the nephron.

When the nephron removes wastes, it also adjusts water and ions — so excretion and osmoregulation are automatically linked.

What does ADH do?

• ADH (antidiuretic hormone) is released from the pituitary gland to regulate the body’s water balance.

• Osmoreceptors in the hypothalamus detect when blood osmotic pressure increases.

• When this happens, the receptors trigger the release of ADH.

• ADH signals the kidneys to reabsorb more water, lowering blood osmotic pressure.

• ADH also increases thirst, encouraging the organism to drink more water.

• Both actions help restore proper hydration.

How do kidneys help regulate blood pressure and blood pH?

The kidneys help control blood pressure and blood pH. To maintain blood pressure, they adjust the amount of water in the blood. The hormone aldosterone signals the kidneys to reabsorb more sodium (Na⁺), and water follows the sodium back into the blood by osmosis. This increases blood volume and raises blood pressure to a healthy level. To regulate blood pH, the kidneys release hydrogen ions, which form carbonic acid, and bicarbonate, which acts as a base. Together, this keeps the blood’s pH balanced.

What is Diabetes Mellitus bruh????

• Condition that happens when your pancreas cannot produce a hormone called insulin

• Overtime filters in the kidney become leaky:

  • Excess sugar builds up within nephrons

  • This increases the solute concentration in that part of the nephron. Higher solute concentration = higher osmotic pressure, which means water is “pulled” toward the glucose instead of being reabsorbed into the blood.

  • Creates water-build up (hence why it becomes leaky)

• This reduces water reabsorption, causing more water to stay in the urine. This is why people with diabetes Mellitus need to urinate frequently and are very thirsty

Why do we need Insulin?

• Essential for maintaining glucose levels, as without it, blood glucose(sugar) levels will raise

What is Diabetes Inspidus?

• Imbalance of fluid in the body

• Causes destruction of ADH-producing cells of the hypothalamus

• Healthy people urinate around 1-3L, people with this urinate about 19L.

• Very thirsty, frequent urination

What is Nephritis?

• Inflammation of the Nephrons

• Affects blood vessels within glomerulus

• Alters permeability of the nephron, making it so proteins and large molecules can pass

• No mechanism to absorb proteins, therefore they remain in nephron

• Frequent urination

What are Kidney Stones?

• Cluster of crystals that are formed from a build-up oxalates, phosphates, and carbonates which then combine with calcium to form the stone

What are the two categories of kidney stones?

• 1. Akaline stones

  • Urine becomes more alkaline (pH higher than normal) from infections

• 2.Acid stones

  • Urine is too acidic, contains high levels of uric acid

• Kidney stones can become sharp and painful, and will try to pass through kidney into ureter

Treatment:

• Shock treatment

• Surgery

How are kidney diseases diagnosed?

• Diagnosed by a urinalysis

• If glucose, protein, RBC, WBC, present than be concerned

• Can also be diagnosed by other stuff like blood test

What are the 2 kinds of Kidney Disease treatments?

1. Dialysis

• Used when your kidney barely functions

• Filtration machine acts as an artificial kidney

2 types:

1. Hemodialysis

2. Peritoneal Dialysis

2. Kidney Transplant

• Used when complete loss of function in kidney

• May need dialysis in combination of the new kidney until it begins to work