Body Systems, Signals & Homeostasis — Chapter Practice, Grade 10

Gas moves between air and blood

Thin barriers permit gas exchange.

Less oxygen and nutrient delivery or slower waste removal can disrupt cellular processes.

Breathing moves air; cellular respiration transfers energy through reactions in cells.

Respiratory exchange and circulatory transport cooperate to supply the muscle.

Oxygen reaches lung exchange surfaces and diffuses into blood.

Circulation carries it to tissue capillaries, where it diffuses toward cells.

Response criteria

• Use the stated conditions.
• Show the evidence or calculation.
• Explain the conclusion and any stated limitation.

Air does not flow through blood vessels as a separate stream.

Water balance influences blood volume, circulation, temperature regulation and cellular conditions.

State what the supplied observations or conditions establish, and separate that from any assumption.

Absorption into transport systems and circulation deliver many nutrients; metabolism uses them at tissues.

No. Cells differ in receptors, pathways and conditions; some may not respond to that signal.

A neuron uses electrical activity and chemical communication to connect defined targets. A hormone is a signaling molecule carried through body fluids and acting on suitable receptors. Neural responses can be rapid and localized; hormonal routes can distribute a signal more broadly, but neither timing rule is absolute. Response depends on receptors, internal pathways and the current state of the target. Coordinated exercise or feeding responses use both kinds of control rather than one universal “brain command” or a hormone affecting every cell identically.

No. Cells differ in receptors, pathways and conditions; some may not respond to that signal.

Response criteria

• Read the structures, axes, directions and units correctly.
• Connect the evidence with the biological mechanism.
• Respect stated model assumptions and distinguish an observation from a further inference.

Respiratory exchange and circulation support changing tissue demand; neural/hormonal regulation can coordinate responses. Different variables have different dynamics, and intensity, conditions and other mechanisms require comparisons before naming one cause.

Respiratory exchange and circulation support changing tissue demand; neural/hormonal regulation can coordinate responses. Different variables have different dynamics, and intensity, conditions and other mechanisms require comparisons before naming one cause.

Response criteria

• Use the stated measurements or conditions, with correct units.
• Connect the result to the biological mechanism or evidence relationship.
• Identify the assumption, model limit or further evidence requested.

maintaining a stable internal environment despite changes outside

Homeostasis is the active maintenance of stable internal conditions (temperature, pH, glucose, water) even as the outside world changes.

reverses the change and pushes the condition back toward its set point

Negative feedback counteracts (reverses) the change, restoring the set point — the most common form of homeostatic control.

Contractions during childbirth strengthening until the baby is born

Childbirth contractions amplify themselves (positive feedback); sweating, shivering, and insulin all reverse a change (negative feedback).

After a meal blood glucose rises. The pancreas detects this and releases insulin, which signals body cells to take glucose out of the blood. This lowers blood glucose back toward its set point, reversing the original rise — a negative feedback loop.

stimulus → receptor → control center → effector → response

A stimulus is detected by a receptor, reported to a control center, which signals an effector to produce a response that restores the set point.

The selectively permeable membrane controls what enters and leaves, and transport processes (diffusion, osmosis, facilitated diffusion, and active transport) let the cell take in needed materials like glucose and oxygen, remove wastes, and balance water and ions. Together they keep the cell's internal conditions steady, which is homeostasis at the cellular level.

A negative-feedback response helping restore temperature toward its regulated range.

The deviation is increased temperature.

Evaporation of sweat can increase heat transfer out, opposing the rise.

Response criteria

• Use the stated conditions.
• Show the evidence or calculation.
• Explain the conclusion and any stated limitation.

Negative means opposing a deviation, not an unhealthy effect.

Negative feedback: the response tends to reduce the initial temperature rise.

State what the supplied observations or conditions establish, and separate that from any assumption.

Sensors, signaling pathways, effectors and the regulated variable can be distributed across interacting systems.

Without the return effect it is merely a chain; without a stopping/limiting mechanism it incorrectly suggests unlimited amplification.

Positive feedback increases the initiating process through a return effect. Selected clotting reactions can amplify local activation until injury conditions and other regulatory mechanisms stop or limit the process. This is not a claim that all clots grow indefinitely or that positive means beneficial. A rising output alone is not enough to classify feedback: identify what feeds back and how it changes the starting process. An endpoint, substrate depletion, spatial restriction or opposing regulation can constrain an amplifying loop.

Without the return effect it is merely a chain; without a stopping/limiting mechanism it incorrectly suggests unlimited amplification.

Response criteria

• Read the structures, axes, directions and units correctly.
• Connect the evidence with the biological mechanism.
• Respect stated model assumptions and distinguish an observation from a further inference.

The intended response is negative feedback because it opposes the deviation. Delayed sensing/response and changing inputs can produce overshoot; a rising value alone does not define positive feedback.

The intended response is negative feedback because it opposes the deviation. Delayed sensing/response and changing inputs can produce overshoot; a rising value alone does not define positive feedback.

Response criteria

• Use the stated measurements or conditions, with correct units.
• Connect the result to the biological mechanism or evidence relationship.
• Identify the assumption, model limit or further evidence requested.

They have suitable receptors and response machinery

Signals require a compatible detection and response system.

Inputs, demands, and responses fluctuate and can have delays.

No. It means amplification; consequences depend on context.

The cell will not show the usual direct response through that missing-receptor pathway.

Reception is the first necessary step in the specified pathway.

Without the receptor, the signal cannot initiate that pathway's normal response.

Response criteria

• Use the stated conditions.
• Show the evidence or calculation.
• Explain the conclusion and any stated limitation.

Exposure to a signal is not sufficient by itself.

No. Signaling can be disrupted without altering DNA sequence.

State what the supplied observations or conditions establish, and separate that from any assumption.

Receptor-triggered pathways can regulate factors controlling transcription, depending on the cell and signal.

The defined output, scale and relevant conditions; otherwise an apparent opposition may compare unlike quantities.

An antagonistic pair has effects that oppose each other on a specified variable. Examples in regulation can include pathways promoting storage versus release or activation versus inhibition. The pathways do not need to be equal in strength, act at the same time or use one universal control organ. A higher signal level can cause different downstream effects depending on receptor and context. Identify the variable, direction and input conditions before calling two molecules opposites; an effect in one tissue does not define all their actions.

The defined output, scale and relevant conditions; otherwise an apparent opposition may compare unlike quantities.

Response criteria

• Read the structures, axes, directions and units correctly.
• Connect the evidence with the biological mechanism.
• Respect stated model assumptions and distinguish an observation from a further inference.

They differ in sensitivity under the stated comparison, not necessarily maximal capacity. Binding, receptor number, downstream amplification and adaptation can differ; further controlled measurements are required.

They differ in sensitivity under the stated comparison, not necessarily maximal capacity. Binding, receptor number, downstream amplification and adaptation can differ; further controlled measurements are required.

Response criteria

• Use the stated measurements or conditions, with correct units.
• Connect the result to the biological mechanism or evidence relationship.
• Identify the assumption, model limit or further evidence requested.

Intact skin

Skin limits entry rather than identifying one specific antigen.

Disease includes noninfectious disruptions, such as inherited or environmental problems.

Persistent antigen-responsive cell populations can expand or act faster.

Selection can increase resistance frequency; the drug need not intentionally create the useful variant.

Susceptible bacteria are reduced by the treatment.

Resistant survivors can reproduce, increasing the resistant proportion.

Response criteria

• Use the stated conditions.
• Show the evidence or calculation.
• Explain the conclusion and any stated limitation.

Memory is specific; it does not guarantee protection from every pathogen.

It recruits protective responses but excessive or misplaced activity can damage tissue.

State what the supplied observations or conditions establish, and separate that from any assumption.

Recognition depends on molecular features; altered antigens can reduce the match to existing immune responses.

The regulated target can be higher still, so the response acts toward it in the stated model.

In a fever model, immune signaling can change thermoregulatory control, producing responses toward a higher target. This differs mechanistically from overheating without an appropriately raised target. Chills or heat-loss responses depend on the relation between current temperature and regulation, not merely whether a reading is above a usual value. Temperature can reflect many processes, and the educational comparison is not enough to classify a real person’s condition. The task is to explain control logic using the supplied target and response curves.

The regulated target can be higher still, so the response acts toward it in the stated model.

Response criteria

• Read the structures, axes, directions and units correctly.
• Connect the evidence with the biological mechanism.
• Respect stated model assumptions and distinguish an observation from a further inference.

It supports increased measured binding under comparable assay conditions. It does not alone establish an exact antibody count, doubled protection, lasting immunity or the full cellular response; additional calibrated/outcome evidence is needed.

It supports increased measured binding under comparable assay conditions. It does not alone establish an exact antibody count, doubled protection, lasting immunity or the full cellular response; additional calibrated/outcome evidence is needed.

Response criteria

• Use the stated measurements or conditions, with correct units.
• Connect the result to the biological mechanism or evidence relationship.
• Identify the assumption, model limit or further evidence requested.