osmoregulation

osmoregulation meaning

• manages body water content

• manges solute composition

• control movement of solute between internal movement and environment

Osmoregulation example

• Marine Iguana

• Special organ that takes salt out of their system

• Salt is then spit out the top of their head

Kidney’s Effect on Blood

• Osmolarity

• Blood pressure

• pH balance

• Osmolarity: concentration of solutes in a solution that affects water movement

• Osmotic pressure: force needed to stop water from moving into a solution by osmosis

• Blood pressure: force of blood pushing against blood vessel walls due to heart pumping

• pH balance

Osmoregulation in Humans

• Excretory system is regulated by the endocrine system

• 3 sets of hormones in osmoregulation

  • ADH

  • RAAS

  • ANF

Hormones in Human Osmoregulation

• blood osmolarity has high levels of ADH

• blood pressure and blood volume has high levels of ANF and low levels of RAAS

Stimulus: high blood osmolarity

• Stimulus: increase blood osmolarity

  • Detection by osmoreceptors in hypothalamus

  • Sends signal to pituitary to release ADH

Antidiuretic hormone (ADH)

• A short peptide hormone

• Produced by the hypothalamus

• Stored in posterior pituitary gland

Effects of ADH: retain water

• Stimulus: increased blood osmolarity

• Detection: osmoreceptors in hypothalamus detect change

• Response: pituitary releases ADH

• Target: distal tubule and collecting ducts

• Effect: more aquaporins added → tubules become more permeable to water

• Result: increased water reabsorption into blood/body

Effects of ADH: Intake Water

• Increase sensation of thirst

  • increase volume of water in body / blood

Effects of ADH

• Direct effect: water reabsorption dilutes blood and lowers blood osmolarity

• Side effects: more concentrated urine, less frequent urination

Source of Osmolarity Disturbances

• Water loss causes: sweating, dehydration, diarrhea

• Excess salt cause: increased salt intake

Diuretics

• Inhibit ADH release

• Effects: less water reabsorption and increased urine output

• Examples: alcohol and coffee

Diabetes

• Common symptom: frequent urination

• Types of diabetes:

  • Diabetes mellitus: related to insulin and glucose

    • Type 1

    • Type 2

  • Diabetes insipidus: related to water reabsorption

Diabetes Insipidus

• Cause: deficiency of ADH

• Effect: kidneys cannot conserve water

• Symptoms: dilute urine, frequent urination, excessive thirst

• Treatment: drink enough water and take ADH medication

• Difference from diabetes mellitus: urine has no glucose and is not sweet

Blood Pressure

• Stimulus: low blood volume and blood pressure

• Detection: by JGA near the glomerulus/afferent arteriole

• Response: JGA secretes the enzyme renin

Effect of Renin

• Renin catalyzes: angiotensinogen → angiotensin II

• Angiotensinogen: constantly produced but only activated when needed by enzyme cleavage

• Effects of Angiotensin II: Constrict area

• Effects of Angiotensin II: Retain water

• Blood vessel constriction

• increases blood pressure

• Stimulate adrenal gland (cortex layer) to release aldosterone

Effects of Aldosterone

• Steroid hormone

• Target: distal tubules

• Effect: increases Na⁺ channels → more sodium reabsorption

• Result: increased blood osmolarity

Secondary Effect of Aldosterone

• Increased osmolarity: stimulates ADH release

• Effect: more water reabsorption

• Result: increased blood volume and blood pressure

Source of Blood Pressure Disturbances

• Water loss: sweating, dehydration, diarrhea

• Blood loss: cuts/bleeding, internal bleeding

• Low salt intake: reduced sodium levels

Atrial natriuretic factor (ANF)

• also known as ANP: peptide hormone from heart atria

• Stimulus: increased blood volume and pressure

• Effect: inhibits NaCl reabsorption → less water reabsorption → decreased blood volume/pressure

• Also: inhibits renin and reduces aldosterone release