Homeostasis and Thermoregulation Flashcards

Comprehensive flashcards covering homeostasis, receptors, the nervous and endocrine systems, feedback loops, tolerance limits, and specific plant and animal thermoregulation adaptations based on Chapter 10 notes.

What is the definition of homeostasis?

The processes involved in maintaining a constant internal environment, within tolerance limits, despite changes in the internal and external environment.

What are the two stages of homeostatic regulation in the stimulus–response model?

1. Detection of a change from the stable state (stimulus) and 2. Response to the stimulus (counteracting the change).

What are enzymes and how do they function as catalysts?

Reusable, biological catalysts (proteins) that lower the activation energy of a chemical reaction, enabling it to proceed faster.

What is the function and location of an osmoreceptor in animals?

It detects changes in osmotic pressure in blood (changes in blood water concentration) and is located in the hypothalamus.

Which receptor detects oxygen and ion levels, and where is it located?

The chemoreceptor, located in the aorta and carotid arteries.

What components make up the Central Nervous System (CNS)?

The brain and the spinal cord.

What is the role of an effector in the nervous system?

Effectors are muscles or glands that carry out a response to stimuli.

How do the response speeds of the nervous and endocrine systems compare?

The nervous system executes a relatively fast response along neurons, while the endocrine system executes a relatively slow response via hormones.

What is the homeostatic function of the hormone Thyroxine?

Secreted by the thyroid, it targets nearly all tissues to increase metabolic rate, oxygen consumption, and heat production.

What is the role of Antidiuretic hormone (ADH) in homeostasis?

Secreted by the posterior pituitary, it targets the kidney to stimulate the reabsorption of water.

What is a negative feedback loop?

A homeostatic process that changes the direction of a stimulus by counteracting the initial deviation, returning values to their normal or optimal level.

What is the function of the coordinating centre (modulator) in the negative feedback model?

Usually the hypothalamus, it receives messages from receptors via sensory neurons, coordinates a response, and sends instructions to an effector via motor neurons.

What occurs if an internal environmental factor goes outside an organism's tolerance range?

It may be fatal for the organism.

What are the three zones defined by the level of an abiotic factor in relation to an organism's survival?

The optimal range (where the organism functions best), the zone of physiological stress, and the zone of intolerance (unavailable niche).

What happens to enzymes at high temperatures above the optimum?

Bonds holding the enzyme together break, changing the shape of the active site, causing the enzyme to become denatured.

How does a decrease in temperature below the optimum affect cell membranes?

Membranes become rigid instead of fluid, which slows the cell membrane transport of substances.

How does an increase in nitrogenous waste affect homeostasis?

It increases toxicity, can increase blood pH due to ammonia, decreases enzyme activity, and affects water balance as cells lose water to dilute the waste.

What is the effect of an increase in water concentration above the tolerance range (hypotonic solution) on animal cells?

Animal cells can swell and burst, a process known as cell lysis.

What percentage of animal blood plasma is water?

$90\%$.

In plant thermoregulation, how do the narrow, vertical leaves of the Hakea coriaceae assist survival?

They minimise direct sunlight hits to reduce heat absorption and increase resistance to night-time frosts in deserts.

What is the difference between an endotherm and an ectotherm?

Endotherms use metabolic processes to generate their own heat to maintain stable internal temperatures; ectotherms rely on the external environment to determine their body temperature.

What is a major cost and a major benefit of being an endotherm?

Cost: High metabolic rate requires more food and energy. Benefit: Can live in extreme environments and remain active at night or in cold weather.

What are the four types of heat transfer involved in thermoregulation?

Conduction (direct contact), Convection (air currents), Evaporation (water turning to vapour), and Radiation (electromagnetic waves).

How do elephants use their ears as a structural adaptation for cooling?

They increase blood supply to their ears and flap them; the high surface area-to-volume ratio allows heat transfer to the surroundings via radiation.

What is 'pilorelaxation' in the context of thermoregulation in hot environments?

The muscles attached to hair follicles relax to flatten the hairs, decreasing the layer of insulating air.

How do the structural features of Arctic foxes reduce heat loss in cold environments?

They have smaller, more rounded ears and limbs to reduce the surface area-to-volume ratio, leaving less surface area for heat to transfer through.

What is vasoconstriction and how does it aid thermoregulation?

It is a physiological response where smooth muscle cells in blood vessels contract to reduce the diameter of arterioles, decreasing blood flow to the skin surface to reduce heat loss via radiation.