Tag: zoology

A fall in GFR can stimulate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR comes back to normal.

A) LH is Luteinising Hormone which is not involved in the concentration of urine.

Caffeine is a central nervous system stimulant of the methylxanthine class of psychoactive drugs. It is the most mildest stimulant and is most widely consumed psychoactive drug. It is present in coffee, tea and cola drinks.
Therefore, the correct answer is option D.

The water reabsorption in the distal part of the nephron is in accordance with the body's state of hydration, under the influence of ADH and is termed as 'facultative reabsorption of water'.  ADH is secreted in the hypothalamus of brain and released into blood stream from the pituitary gland. The collecting ducts become more permeable to water due to the effect of ADH, so more water is reabsorbed by osmosis and no expenditure of ATP energy is required. The release of ADH is triggered when osmoreceptors in the hypothalamus detect an increase in osmolarity of the blood above a set point of ${300 mosm L^{-1}}$. In this situation the osmoreceptors cells also promotes thirst. Drinking reduces the osmolarity of the blood, which inhibits the secretion of ADH.

Juxtaglomerular cells are specialized smooth muscle cells of glomerular arterioles. They synthesize, store and secrete the enzyme renin. It plays a critical role in the renin angiotensin system and thus in renal autoregulation of the kidney.

• Expiration is a mechanism in which air which contains carbon dioxide release out from the lungs of the body.
  
• This air is dry and contains more moisture from the lungs.
• Lungs can never be empty even after force full expiration some amount of air remains in it known as residual volume.
• The exchange of gases occurs only at cellular and alveolar site, not in expiration.
  

During inspiration, the diaphragm contracts and flattens to increase the volume of the the thoracic cavity. This increase in volume leads to a decrease in intra-alveolar pressure, which is a pressure lower than atmospheric pressure and creates the pressure gradient. Due to the gradient the air is from the atmosphere is forced inside the lungs through nasal cavity.

The diaphragm is the muscular organ situated between the thoracic cavity and the abdominal cavity. It contracts and moves downwards due to which the volume in the lungs increases and the air is inhaled. When it relaxes, the volume of the lungs decreases and the air is expelled out.