D3.3 Homeostasis

What is homeostasis?

The maintenance of the internal environment of an organism, including factors like blood glucose concentration, osmoregulation, pH, and temperature.

What are the two types of cells in the Islets of Langerhans?

alpha and beta cells

What do alpha cells produce?

Glucagon

What do beta cells produce?

Insulin

Role of Glucagon

glucagon raises blood glucose levels by stimulating the breakdown of glycogen

Role of Insulin

Insulin lowers blood glucose levels by promoting glucose uptake into body tissues

What are the physiological changes associated with type 1 diabetes?

Type 1 diabetes involves an inability to produce sufficient insulin due to autoimmune destruction of beta cells in the pancreas.

What are the physiological changes associated with type 2 diabetes?

A deficiency of insulin receptors and glucose transporters, leading to an inability to respond to insulin

How does the body monitor temperature?

Peripheral thermoreceptors in the skin and central thermoreceptors in the hypothalamus

What hormone does the hypothalamus secrete in response to cold?

Thyrotropin-releasing hormone (TRH)

What hormone does the pituitary gland secrete in response to TRH?

Thyroid-stimulating hormone (TSH)

What does thyroid-stimulating hormone (TSH) do?

Stimulates production of thyroxin by the thyroid, increasing metabolic rate of cells

What happens during vasoconstriction in response to cold?

Blood vessels narrow to reduce blood flow to the skin and minimize heat loss.

Shivering

Muscles contract cause movement and generate heat

Uncoupled Respiration (Brown adipose tissue)

Brown adipose tissue generates heat energy through respiration instead of ATP

What is vasodilation?

Blood vessels widen and increase blood flow to skin for more heat loss

Sweating

Sweat secreted by glands in the skin, and its evaporation is cooling

What is osmoregulation?

The process of maintaining the osmotic concentration of body fluids.

What is the function of the glomerulus in the kidney?

The glomerulus filters fluid out of blood plasma to produce glomerular filtrate, retaining larger molecules like plasma proteins and blood cells

Afferent arteriole

How blood enters the glomerulus

Efferent arteriole

How blood leaves the glomerulus

Why are plasma proteins and blood cells not part of the glomerular filtrate?

They are larger molecules and are not as permeable

What is the role of the Bowmans’s Capsule?

Participates in the filtration of blood from glomerular capillaries

What is the role of the Proximal Convoluted Tubule?

Reabsorption of substances in the filtrate

How are sodium ions reabsorbed?

Active transport

How are chloride ions reabsorbed?

Diffuses from the charge gradient from active transport of sodium ions

How is glucose reabsorbed?

Moved by cotransporter proteins in outer membrane of tubular cells

How is water reabsorbed?

Osmoses using the solute concentration gradient

What is the role of the loop of Henle in the kidney?

It establishes and maintains the osmotic concentration gradient in the medulla of the kidney.

Permeability of Ascending limb

Impermeable to water, permeable to sodium ions

Permeability of Descending Limb

Permeable to water, impermeable to sodium ions

How is blood osmotic concentration regulated?

Removing varying amounts of water from urine

How does the permeability of water in cells in distal convoluted tubule/collecting duct vary?

Number of aquaporins in the plasma membrane of cells

ADH

Antidiuretic hormone

What triggers the release of antidiuretic hormone (ADH)?

High blood osmotic concentration triggers the pituitary gland to secrete ADH, which increases water reabsorption in the collecting duct.

Response to high blood osmotic concentration

More water reabsorption

Response to low blood osmotic concentration

Less reabsorption of water