Which one of the following is synthesised in human body that dilates blood vessels and increases blood flow ?

This snippet names nitric oxide (NO) as a distinct reactive chemical species and describes its chemical activity, showing it is a well‑defined biologically relevant molecule.

A student could combine this with basic physiology knowledge (that the body produces many small reactive molecules) to justify checking whether NO is produced endogenously and has signaling roles in humans.

Defines blood pressure and states that constriction of arterioles increases resistance and causes hypertension, linking vessel diameter to blood flow and pressure.

Using the inverse relationship between vessel diameter and resistance, a student could infer that a substance that dilates arterioles would lower resistance and increase flow, motivating investigation of whether NO performs that role.

Explains that hormones and signals can cause contraction of muscles around small arteries, redistributing blood — an example that chemical signals modulate vessel tone.

A student can generalize that endogenous chemicals alter arteriole smooth muscle and therefore seek whether NO is one such endogenous vasomotor mediator.

Describes blood as the transport medium for many substances, implying that dissolved signaling molecules can reach tissues and affect function.

Given blood transports signaling compounds, a student could reasonably hypothesize and then check if NO (or its precursors) is carried or generated near vessels to change blood flow.

Shows nitrous oxide (N2O) exists naturally as part of the global nitrogen cycle and can be produced by natural processes.

A student could infer that biological systems can generate nitrogen oxides and check biomedical sources or breath/urine measurements to see if humans produce N2O.

Describes biological/chemical pathways (denitrification/nitrification) that produce nitrogen oxide species (NO) from nitrogen compounds.

One could extend this by investigating whether analogous enzymatic pathways exist in human tissues that could produce nitrogen oxides including N2O or related gases.

Notes blood plasma transports dissolved nitrogenous wastes, indicating the body produces and moves nitrogen-containing molecules systemically.

A student could look for whether any transported nitrogenous molecules in plasma include gaseous nitrogen oxides (e.g., measured in blood or breath) to test endogenous N2O synthesis.

Explains that chemical signals (hormones) act on smooth muscle around small arteries to alter vessel diameter and redirect blood flow.

Using this rule, one can reason that if a gas produced by the body acts as a signaling molecule on vascular smooth muscle, it could cause vasodilation and increase flow — so look for evidence that N2O or related gases act as vascular signals in humans.

Defines that constriction of arterioles increases resistance and raises blood pressure, implying the converse (dilation) would reduce resistance and increase flow.

A student could extend this physical principle to predict measurable hemodynamic changes (e.g., lower peripheral resistance, increased local flow) if a compound like N2O dilates vessels, and then search for such measurements in physiological studies.

Describes the circulatory system as transporting gases and other substances in blood, establishing that gases can be carried to and from tissues.

A student could ask whether small reactive gases (like NO2) can be transported or produced in blood and look for biochemical sources or measurements in human tissues.

Explains gas exchange at alveoli and that blood carries respiratory gases, showing the lungs are a locus for gas uptake/release.

One could extend this to consider whether inhaled NO2 reaches blood or whether lung cells convert nitrogen species, then consult physiological/biochemical sources.

Gives a chemical relationship between nitric oxide (NO) and nitrogen dioxide (NO2), indicating interconversion can occur chemically.

A student could use this chemical link plus knowledge that NO is a biological signaling molecule to investigate whether NO2 can form in vivo from NO or vice versa.

Describes NO2 as an externally produced gas (from combustion) that affects the respiratory tract, showing NO2 interacts with human tissues when present.

This suggests checking whether exposure, uptake, or local chemical reactions of NO2 in the respiratory tract could lead to systemic presence or vascular effects.

Notes health effects of nitrogen oxides on lungs and enzymes, implying nitrogen oxides can influence physiological function.

A student could extend this to investigate whether such effects include direct vasodilation or altered blood flow, by consulting physiological studies.