Water Balance and Homeostasis Flashcards

Flashcards about water balance and homeostasis

What is transpiration?

The process by which water vapor is lost from a plant to the atmosphere, primarily through the stomata in the leaves.

What drives transpiration?

Evaporation of water from the moist surfaces of mesophyll cells, followed by diffusion of water vapor through the stomata.

What happens to a plant that loses more water through transpiration than it gains?

It experiences water stress and wilts.

What physiological change happens within the plant?

Tension in xylem vessels increases, creating an increase in water potential gradient from soil to xylem.

How do roots absorb water from the soil?

Through osmosis.

What happens if the soil is dry relative to osmosis and transpiration?

Water absorption slows, and stomata close to minimize water loss.

What controls the opening and closing of stomata?

Guard cells.

How do guard cells open stomata?

They attract ions (and thus water), become turgid, and open the stomata.

How do guard cells close stomata?

Ions flow out of them, they lose water and become flaccid, closing the stomata.

What are regulatory mechanisms for the survival in a range of environments?

Mechanisms for maximum efficiency in functioning, growth, and survival.

What constitutes the external environment for humans?

The air that surrounds us, inside the respiratory and digestive systems, and inside the tubules of excretory systems.

What is a stimulus in the context of homeostasis?

A detectable change in a physical or chemical factor in the internal or external environment of a person.

What is an effector?

A body tissue or organ (gland or muscle) that carries out a response.

What is a response?

Changes in the structure, function, or behavior of a person.

What is a feedback mechanism?

A mechanism where a response counteracts or reinforces a stimulus.

Why is negative feedback useful?

A system of control in which a response occurs to produce a change that counteracts or reverses a stimulus, used for homeostasis.

What is a set point?

The target value or range that the body strives to maintain for a specific physiological variable.

What is the internal environment?

All fluids that surround and bathe body cells (interstitial fluid, extracellular fluid, lymph fluid, blood plasma).

What do interstitial fluid etc. do?

Provide essential inputs to cells, remove cell waste, and transport molecules around the body.

Define optimum range

The conditions in which humans thrive and function best.

Define tolerance range

The conditions in which humans can survive, but not thrive.

Define psychological stress

The result of conditions outside of the tolerance range, leading to a breakdown of regulatory mechanisms.

What does prolonged psychological stress leads to?

Death, as survival is impossible outside the zone of intolerance.

What are exteroceptors?

Receptors that detect stimuli from the external environment.

What are interoceptors?

Receptors that receive signals from within the body's internal environment.

List internal conditions in the tissue/extracellular fluid and blood plasma that need to be kept within limits

Temperature, pH, concentrations of solutes and gases, concentration of water and ions.

What is the purpose of thermoregulation?

To maintain a relatively constant body temperature (homiothermic) by using body structures, functioning, and behavior.

Define radiation in the context of thermoregulation

Heat transfer from an object by infrared energy waves.

Define conduction in the context of thermoregulation

Transfer of heat energy from a hotter to a cooler object by direct contact.

Define convection in the context of thermoregulation

Heat transfer when hot air or water rises and is replaced by an inflow of cooler air or water.

Define evaporation in the context of thermoregulation

When liquid water turns into water vapor, heat energy is used, cooling the surface.

What is the role of the hypothalamus in temperature regulation?

It acts as a thermostat with sensitive thermoreceptors that detect blood temperature.

What does the anterior region of the hypothalamus do?

Releases hormones, many of which interact with the pituitary gland.

What does the middle region of the hypothalamus do?

Involved in controlling appetite and in growth and body development.

What does the posterior region of the hypothalamus do?

Involved in temperature control by causing shivering and blocking sweat production.

What is the relationship between metabolic activity and heat production?

An increase in metabolic activity means more heat is produced because more energy is produced.

How to reduce heat gain?

Decreasing metabolic rate (but not completely).

How to increase heat loss?

Sweat glands activated, vasodilation, arrector pili muscles relax.

What is the function of arrector pili muscles?

Contracting to cause goosebumps, but no insulating air layer.

What is hypothermia?

A condition that occurs due to prolonged exposure to low temperature, where the body loses more heat than it produces.

What is hyperthermia?

A condition that occurs due to overproduction or absorption of heat.

What is the role of evaporation in heat loss for animals?

Evaporation, such as through sweating, is a major way to lose heat.

How do birds radiate heat?

Birds flap or flutter their wings close to their throat to increase radiation of heat from their bodies and increase convection.

How do animals retain heat?

Hibernation, insulation (thick skin, blubber, feathers), countercurrent blood flow, and blood chemicals to reduce freezing.

What is the function of countercurrent blood flow?

Cool blood absorbs heat from warm blood and returns it to the body rather than being excreted.

How does insulin regulate blood glucose levels?

Insulin travels in the bloodstream to most cells of the body, causing them to increase glucose uptake.

What is the role of glucagon in balancing blood glucose?

Glucagon causes liver cells to convert glycogen to glucose, releasing glucose in the blood.

What is osmoregulation?

Regulation of water in the body.

How is water lost from the body?

continuously

What happens if water input does not equal water output?

Balance between solute and solvent concentrations in tissue fluids and blood cant be regulated and bodily functions affected.

Explain Vasopressin effect.

ADH goes to kidneys and increases permeability of tubule linings → more water is absorbed and concentrated, less urine is produced. Another response=drink more water

Why is thyroid hormones important?

Impacts cellular differentiation, growth and metabolism