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Homeostasis is the ability to maintain a constant internal environment at present

values despite fluctuations from the external environment

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What is meant by the term "osmoregulation"?

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What is meant by the term "osmoregulation"?

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The process of keeping the osmotic concentration of the body with narrow limits of homoeostasis.

Osmotic concentration is the concentration of solutes dissolved in a watery solution. Osmotic concentration is usually measured in milliosmoles per liter (mOsm/L)

-> It is crucial because it maintains the proper balance of water and salts within an organism's body, ensuring that cells function optimally by preventing them from shrinking or swelling due to drastic changes in solute concentration.

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Osmoregulation by water reabsorption in the collecting ducts

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Osmoregulation by water reabsorption in the collecting ducts

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Which hormone controls the release of water from the collecting duct?
Antidiuretic hormone (ADH), also known as vasopressin,

What is the effect of this hormone?

ADH controls the release of water from the collecting duct by increasing the duct's permeability to water, allowing more water to be reabsorbed from the urine back into the bloodstream. This process helps the body conserve water and reduces the amount of urine produced.

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- Stimulus that disrupts homeostasis

- Receptor that detects the change

- Input, information is sent to the control center

- Control center, receives input then provides

- Output, the result of the body reaction

- Effectors, restores the condition

- Response, restoring homeostasis

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What substances are filtered in the Bowman's capsule?

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What substances are filtered in the Bowman's capsule?

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1. Water

2. Electrolytes

3. Glucose

4. Amino acids

5. Peptides

6. Nitrogenous waste

7. Hormones

8. Vitamins

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Physiological changes that form the basis of type 1 and type 2 diabetes:

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Physiological changes that form the basis of type 1 and type 2 diabetes:

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Definition of Diabetes Type I

Diabetes type I is an autoimmune condition in which the immune system mistakenly attacks and destroys the beta cells of the pancreas that produce insulin, causing the pancreas to stop producing insulin. The caused of type I diabetes is still unclear, but most of it is caused by genetic factor and environment, like virus or bacterial.

Symptoms of Diabetes Type I

Frequent urination (polyuria)

Excessive thirst (polydipsia)

Extreme hunger (polyphagia)

Unexplained weight loss

Fatigue and weakness

Blurred vision

Sometimes diabetic ketoacidosis (DKA) as the first sign

Treatment

Monitoring blood glucose levels and injecting human insulin throughout the day (Particularly after meals consumed).

Definition of Diabetes Type II

Diabetes type II is a insulin resistance condition, the pancreas still produce insulin but body’s cell do not respond to it properly.

Symptoms of Diabetes Type II

Frequent urination

Increased thirst

Increased hunger

Fatigue

Blurred vision

Slow-healing sores or frequent infections

Numbness or tingling in hands/feet (neuropathy)

Often develops gradually, may go unnoticed for years

Treatment

Maintain a low carbohydrate diet and regular exercise to reduce need for insulin

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1. Blood cells

2. Plasma proteins

3. Protein bound molecules

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The Bowman capsule has 3 important structural features which are adapted to carry out ultrafiltration. Describe how they assist in the process.

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The Bowman capsule has 3 important structural features which are adapted to carry out ultrafiltration. Describe how they assist in the process.

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1) Fenestration:

- small window-like pores

- found in the endothelial lining of the glomerular capillaries in the kidney

- 70–100 nanometers in diameter

- the first layer of the filtration barrier in the Bowman’s capsule.

- allow the passage of water and small solutes such as ions, glucose, amino acids, and urea

- preventing larger structures like red blood cells, white blood cells, and platelets from leaving the bloodstream

2) Basement membrane:

- second layer of the glomerular filtration barrier

- thick, gel-like structure made of extracellular matrix proteins such as collagen, laminin, and negatively charged glycoproteins.

- a size-selective and charge-selective filter.

-stops large molecules, especially plasma proteins like albumin, are prevented from crossing

- Ensuring useful cells and proteins remain in the blood, while smaller substances like water, ions, glucose, amino acids, and nitrogenous wastes pass through into the Bowman’s capsule.

3) Podocyte:

- epithelial cells that cover the outside of the glomerular capillaries in the Bowman’s capsule

- branch further into tiny foot processes (or pedicels), leaving narrow gaps called filtration slits

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Thermoregulation is the process by which the body maintains a stable internal temperature (~37°C), despite changes in the external environment.

It is a classic example of negative feedback control.

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How the Body Responds to Temperature Changes

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How the Body Responds to Temperature Changes

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When Body Temperature Rises (Too Hot):

Peripheral thermoreceptors detect increased skin temperature.

Signals sent to hypothalamus trigger cooling mechanisms:

Sweat glands produce sweat → evaporative cooling.

Vasodilation of skin blood vessels → more heat lost through skin.

Metabolic rate may decrease to reduce heat production.

When Body Temperature Falls (Too Cold):

Peripheral thermoreceptors detect low temperature.

Hypothalamus activates heat-producing responses:

Muscle shivering: rapid muscle contractions generate heat.

Vasoconstriction: skin blood vessels constrict to reduce heat loss.

Thyroxin secretion increases, raising metabolic rate for more heat.

Brown adipose tissue (brown fat) generates heat by burning fats (non-shivering thermogenesis).

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Role of Effectors: Muscle and Adipose Tissue

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Role of Effectors: Muscle and Adipose Tissue

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Skeletal muscles: Shivering produces heat by rapid contractions

Brown adipose tissue: Specialized fat that generates heat without muscle movement (especially in infants)

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Summary of Negative Feedback Loop in Thermoregulation

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Summary of Negative Feedback Loop in Thermoregulation

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Keeps enzymes working optimally.

Prevents damage from extreme temperatures.

Maintains overall homeostasis and survival.

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3. The role of the Loop of Henle - Osmoregulation

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3. The role of the Loop of Henle - Osmoregulation

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It is important to conserve water for terrestrial animals. The Henle loop concentrates the salt in the medulla and hence causing a vigorous osmotic flow of water from the collecting duct, therefore concentrating the urine.

Sodium and chloride ions are pumped out of the filtrate in the ascending limb of the loop of Henle into the surrounding medulla region, lowering its water potential

Describe osmoregulation in the descending limb:

The neighbouring descending limb is permeable to water, so water moves out of the descending limb by osmosis due to the low water potential of the medulla created by the ascending limb

The descending limb has few transport proteins in the membranes of its cells, so has low permeability to ions

The water potential of the filtrate decreases as the descending limb moves down into the medulla due to the loss of water and retention of ions

Describe osmoregulation in the ascending limb:

The ascending limb of the loop of Henle is impermeable to water, so water is unable to leave the loop here by osmosis

The water potential of the ascending limb increases as it rises back into the cortex due to the removal of solutes and retention of water

The low water potential in the medulla created by the ascending limb also enables the reabsorption of water from the collecting duct by osmosis

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Hypothermic conditions (body temperature too low):
Central and peripheral thermoreceptors in the skin and body core activate the hypothalamus, which stimulates thyroxine release to increase metabolism and heat production. Heat-generating mechanisms include:

Vasoconstriction of skin blood vessels – decreases blood flow to the skin, reducing heat loss.

Shivering of skeletal muscles – rapid muscle contractions generate heat.

Piloerection (hair stands on end) – traps an insulating layer of air near the skin (in humans, minimal effect but part of the response).

Increased metabolic rate – more cellular respiration produces additional heat.

Behavioral responses – seeking warmth, adding clothing, or curling up.

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Hyperthermic conditions (body temperature too high):
Central and peripheral thermoreceptors in the skin and body core activate the hypothalamus, which reduces thyroxine release to lower metabolic heat production. Heat-releasing mechanisms include:

Vasodilation of skin blood vessels – increases blood flow to the skin, enhancing heat loss.

Sweat gland activation – sweating and evaporation cool the body surface.

Reduced metabolic rate – less heat is produced internally.

Behavioral responses – seeking shade, removing clothing, or drinking fluids.

These mechanisms restore homeostasis by bringing body temperature back to the normal set point.

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Osmoregulation by water reabsorption in the collecting ducts

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Osmoregulation by water reabsorption in the collecting ducts

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Osmoregulation via water reabsorption is the kidney's process of conserving water to maintain the body's fluid and electrolyte balance. It involves filtering blood, then reabsorbing essential water and solutes from the resulting filtrate back into the bloodstream, primarily under hormonal control by antidiuretic hormone (ADH).

ADH, which increases the collecting ducts' permeability to water, allows water to be reabsorbed into the bloodstream via aquaporins.

When the body is hydrated, ADH levels decrease, reducing water reabsorption and producing dilute urine; conversely, dehydration increases ADH, leading to greater water reabsorption and concentrated urine.

Which hormone controls the release of water from the collecting duct?

Antidiuretic hormone (ADH), or vasopressin.

The effects are :

increases the permeability of the collecting duct walls to water.

stimulates the insertion of aquaporin water channels to collecting duct cell membranes.

This allows more water to be reabsorbed back into the blood by osmosis.

As a result, urine becomes more concentrated, and water is conserved in the body.

What happens when a person is dehydrated?

The pituitary gland releases more ADH.

More water is reabsorbed into the bloodstream, reducing water loss in urine.

Urine volume decreases and becomes darker/more concentrated.

Thirst is also stimulated, encouraging the person to drink water.

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Osmoreceptors in the hypothalamus detect this and reduce ADH secretion from the pituitary gland.

With less ADH, the collecting ducts become less permeable to water.

Less water is reabsorbed into the blood, and a larger volume of dilute urine is excreted.

blood water potential is balanced.

This maintains normal blood osmotic pressure.

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Which factors change the composition of urine?

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Which factors change the composition of urine?

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water intake

salt intake

health conditions

temperature

exercise levels

hormones

hydration status

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The role of the circulatory system is to supply the cells of the body with oxygen and nutrients, and to remove the waste products of metabolism.

1. During exercise the muscles will require more oxygen and glucose to fuel muscle contraction, so will need an increased blood supply

2. After a meal the digestive system will require more oxygen and glucose to fuel digestion and absorption, so will need an increased blood supply

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Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

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Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

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Everytime after we eat, as glucose floods your bloodstream our body ensure blood sugar levels remain safe with the action of two hormones: insulin and glucagon. Together, they maintain blood glucose levels through homeostasis.

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The circulatory system can divert blood flow to increase or decrease the blood supply to different organs. Achieved by vasodilation or vasoconstriction in the arterioles.

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The Pancreas Detects and Responds to Glucose Changes

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The Pancreas Detects and Responds to Glucose Changes

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1. The pancreas serves as both a sensor and responder in regulating blood glucose.

2. Dual Function of the Pancreas:

1. Exocrine Function: Produces digestive enzymes to aid in digestion.

2. Endocrine Function: Contains islets of Langerhans, which house two types of cells:

1. Alpha Cells: Secrete glucagon to increase blood glucose.

2. Beta Cells: Secrete insulin to decrease blood glucose.

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When blood glucose levels rise after a meal, beta cells in the pancreas release insulin, which prevents hyperglycemia.

How Insulin Works

1. Glucose Absorption:

1. Insulin binds to receptors on muscle and liver cells, prompting them to absorb glucose.

2. Glucose transporters (e.g., GLUT4) move glucose into cells.

2. Glycogen Formation:

1. In the liver and muscles, insulin activates enzymes to store glucose as glycogen.

3. Inhibits Glucose Production:

1. Suppresses the liver’s production of glucose from non-carbohydrate sources.

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1. Maintaining blood glucose levels is critical for survival.

2. Glucose is the primary energy source for the brain, and imbalances can lead to serious conditions like diabetes.

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Skeletal Muscle

During sleep the skeletal muscles are relaxed and blood flow to these muscles is relatively low

During wakefulness some muscle groups will be working to keep the body upright, and blood flow will increase

There will be a large increase in blood flow during physical exercise, as rapid contraction of many muscle groups will occur

Gut

Soon after a meal the blood flow to the gut will increase

Blood flow decreases during exercise so that more blood can be diverted to the skeletal muscles

Brain

The blood flow to the brain remains relatively constant regardless of the activity levels of the body, as it carries out processes that need to occur all the time

Blood flow increases slightly during a stage of sleep known as REM

Kidneys

Blood flow does not change significantly on the basis of activity level, but will increase slightly during sleep and rest, and decrease slightly during prolonged exercise

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Between meals or during exercise, blood glucose levels drop. Alpha cells in the pancreas release glucagon, which prevents hypoglycemia.

How Glucagon Works

1. Glycogen Breakdown:

1. Glucagon signals the liver to break down glycogen into glucose.

2. Glucose Production:

1. Promotes gluconeogenesis, synthesizing glucose from amino acids and other sources.