Hormonal control

Question 1

homeostatic control

Answer 1

• passive movement of molecules (from a high concentration to a lees of them down a concentration gradient)
• water follows osmosis
• solutes will move the same as water (following water)
• water will always follow the salt solution if allowed
• same concentrations = isotonic
• some molecules are actively transported using carrier molecules (needs energy)

Question 2

osmoregulation

Answer 2

• correct balance between water and solute contents
• controlled by the kidney and skin
• too little = dehydration
• too much = burst cells
• concentration of solutes determines osmolarity (amount of solute particles dissolved in 1 litre of water) (osmotic pressure)

Question 3

Role of ADH

Answer 3

• about 99% of water is reabsorbed into the blood stream mostly in the proximal tubule and ascending loop of henle
• when fluid intake is low, sodium ions are pumped out of the loop of henle which creates a hypertonic tissue fluid in the medulla
• this causing water to move by osmosis from the filtrate into the blood in the peritubular capillaries.
• dissolves in bloodplasma
• causes collecting ducs to enlarge making them more permeable to water
• more water moving by osmosis from filtrate to blood
• less but more concentrated urine is excreted

Question 4

ADH

Answer 4

• Antidiuretic hormone
• secreted by the hypothalamus
• stored in the posterior pituitary gland
• prevents an increased output of urine
• special cells in the hypothalamus (osmoreceptors) cause someone to drink when osmolarity is low because of dehydration
• pituitary gland releases ADH

Question 5

Aldosterone

Answer 5

• steroid hormone
• produced by adrenal glands
• controls the control of sodium ions in the body
• causes reabsorption of sodium ions from the filtrate to the bloodstream
• this causes water to follow to increase blood volume (therefore blood pressure)
• linked to the balance of water and blood pressure

Question 6

Negative feedback

Answer 6

• factor (change in variable)
• sensor (change detected by the receptor)
• integrating system (information sent to control centre)
• effector (information sent to effector then tries to create a balance again by giving a response back to the influence)

Question 7

endocrine system

Answer 7

• organs that produce hormones
• pituitary gland
• pancreas
• testies
• thyroid gland
• adrenals
  ovaries

Question 8

homeostasis

Answer 8

• the state of steady chemical and physical conditions. To ensure optimum functional conditions for organisms