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What is homeostasis? State the role of the kidneys in homeostasis - Leaving Cert Biology - Question 12 - 2004
Question 12
What is homeostasis? State the role of the kidneys in homeostasis. (b) (i) Draw a labelled diagram of a nephron. Include blood vessels in your diagram. (ii) Filtrat... show full transcript
Worked Solution & Example Answer:What is homeostasis? State the role of the kidneys in homeostasis - Leaving Cert Biology - Question 12 - 2004
Step 1
What is homeostasis? State the role of the kidneys in homeostasis.
Answer
Homeostasis refers to the processes that maintain a stable internal environment within an organism, ensuring that conditions remain consistent and optimal despite changes in external environments. The kidneys play a crucial role in homeostasis by regulating the body's water balance and electrolyte levels. They filter blood to remove waste products while reabsorbing necessary substances, thus maintaining the blood's composition and volume.
Step 2
Draw a labelled diagram of a nephron. Include blood vessels in your diagram.
Answer
To draw a labelled diagram of a nephron, represent its key components:
- Bowman's capsule
- Glomerulus
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct Additionally, label the associated blood vessels:
- Afferent arteriole
- Efferent arteriole You should ensure proper scale and clarity, indicating the flow of blood and filtrate through these structures.
Step 3
Filtration and reabsorption are vital processes that take place in the nephron. Describe how each of these processes occurs.
Answer
Filtration begins in the glomerulus, where blood pressure forces water and small solutes out of the blood and into Bowman's capsule, forming filtrate. Larger molecules and blood cells remain in the bloodstream due to their size.
Reabsorption occurs primarily in the proximal convoluted tubule, where essential substances like glucose, amino acids, and various ions are selectively reabsorbed back into the bloodstream through active transport and diffusion. This process continues in the Loop of Henle and distal convoluted tubule, where additional water and electrolytes are reabsorbed, ensuring the body retains what it needs while excreting waste.
Step 4
What is the source of the heat that allows the body to maintain a constant internal temperature?
Answer
The primary source of heat in the human body comes from metabolic processes, particularly the breakdown of nutrients such as carbohydrates and fats in organs like the liver and muscles. These biochemical reactions release energy in the form of heat, which helps maintain a stable internal body temperature.
Step 5
State two ways in which the body is insulated against loss of heat.
Answer
- Fatty tissue (adipose tissue) provides insulation by trapping heat within body layers, preventing significant heat loss.
- Hair or fur acts as a barrier to reduce heat release from the skin surface, creating an insulating layer around the body.
Step 6
Describe the ways in which the body responds when its internal temperature rises above the normal level.
Answer
When body temperature rises, several responses initiate to cool it down:
- Vasodilation occurs in blood vessels, increasing blood flow to the skin's surface where heat can dissipate through radiation and convection.
- Sweating is stimulated, allowing moisture to evaporate from the skin's surface, which cools the body down as the sweat evaporates.
Step 7
Describe briefly the hormonal and nervous responses that occur when internal body temperature drops.
Answer
When body temperature drops, the hypothalamus detects the change and triggers several responses:
- Hormonal response: The release of hormones like thyroxine increases metabolic activity, generating more heat.
- Nervous response: Nerve impulses stimulate shivering, causing rapid, involuntary muscle contractions, which produce heat, and promote vasoconstriction, reducing blood flow to the skin and minimizing heat loss.