14. Coordination and response(Part 4)(Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025)

Summary

This video is part 4 of the IGCSE Biology series on coordination and response, focusing on homeostasis and negative feedback. It explains how the body maintains internal balance, regulating factors like blood glucose and temperature. Examples include insulin and glucagon's role in controlling blood sugar and how sweating, shivering, and vasodilation manage body heat. The video also covers type 1 diabetes and the role of the skin. Additionally, it explores plant tropisms, discussing how auxins control plant growth in response to light and gravity.

Takeaways

• 📚 Homeostasis is the maintenance of a stable internal environment, necessary for proper cell and organ function.
• ⚖️ Negative feedback helps maintain homeostasis by reversing changes that deviate from the set point, such as body temperature or blood glucose levels.
• 🌡️ The set point for normal human body temperature is approximately 37°C, and deviations trigger corrective mechanisms.
• 🍬 The regulation of blood glucose levels involves insulin and glucagon: insulin lowers glucose levels, while glucagon raises them.
• 💉 Type 1 diabetes is characterized by the inability to produce insulin, leading to high blood glucose levels; it is managed with insulin injections and lifestyle changes.
• 🧴 The skin plays a key role in thermoregulation, with mechanisms like insulation, sweating, and blood vessel adjustments helping maintain body temperature.
• 🩸 Vasodilation (widening of blood vessels) helps cool the body, while vasoconstriction (narrowing of blood vessels) helps conserve heat in cold conditions.
• 🌱 Plants respond to environmental stimuli such as light and gravity through tropisms—growth movements towards or away from stimuli.
• 💡 Phototropism causes plant shoots to grow towards light, while gravitropism causes roots to grow towards gravity.
• 🌿 Auxins are plant hormones that control growth by promoting cell elongation; their distribution influences the direction of plant growth in response to light and gravity.

Q & A

What is homeostasis and why is it important?

Homeostasis is the maintenance of a stable internal environment in the body. It is essential because it ensures proper cell and organ function, preventing health issues that can arise from imbalances, such as temperature or glucose level fluctuations.

How does negative feedback work in maintaining homeostasis?

Negative feedback detects any deviation from a set point and activates corrective mechanisms to restore it. Once the factor returns to its ideal level, the corrective actions are stopped until needed again, keeping the internal environment stable.

What role does insulin play in regulating blood glucose levels?

Insulin is released by the pancreas when blood glucose levels are high. It prompts the liver to convert excess glucose into glycogen for storage, lowering blood glucose levels back to normal.

What causes Type 1 diabetes, and how is it managed?

Type 1 diabetes is caused by the pancreas failing to produce enough insulin, leading to high blood glucose levels. It is managed by insulin injections, blood glucose monitoring, diet control, and regular exercise to help manage glucose levels.

What are the main parts of the skin involved in temperature regulation?

The skin parts involved in temperature regulation include hairs, hair erector muscles, sweat glands, sensory receptors, neurons, blood vessels, and fat tissue.

How does the body respond when it’s too cold?

When cold, the body initiates responses like shivering to generate heat, vasoconstriction to reduce heat loss, and contraction of hair erector muscles to trap warm air near the skin.

What is vasodilation, and how does it help in cooling the body?

Vasodilation is the widening of blood vessels near the skin surface, increasing blood flow and allowing more heat to be lost through radiation, which cools the body.

What are tropisms, and what types of responses do plants exhibit to light and gravity?

Tropisms are directional growth responses to stimuli. Phototropism is a plant’s growth toward or away from light, while gravitropism is growth in response to gravity. Shoots are positively phototropic and negatively gravitropic, whereas roots are the opposite.

What is the role of auxins in plant growth?

Auxins are plant hormones that control growth by promoting cell elongation. When unevenly distributed due to light or gravity, auxins cause differential growth, leading plants to bend towards light or grow in response to gravity.

How does phototropism occur in shoots exposed to light from one direction?

In one-sided light, auxins accumulate on the shaded side, causing cells on that side to elongate more than those on the lighted side, resulting in the shoot bending toward the light.