Which of the following carry oxygen-poor blood?

This phenomenon is called molecular mimicry, where antibodies generated against foreign antigens (like viruses or bacteria) mistakenly recognize similar structures on the body’s own cells. This cross-reactivity can trigger an autoimmune response, leading the immune system to attack healthy tissues. Conditions such as rheumatic fever or type 1 diabetes can result from this type of immune misidentification.

A. A chemical messenger that is triggered by the binding of a ligand on the cell surface and causes a change in DNA transcription:This describes the mechanism of some hormones or intracellular signaling molecules, particularly steroid hormones, but it is not a complete definition of a hormone itself.

B. Junctions between cells interconnecting their cytoplasm:This describes gap junctions, which allow direct cytoplasmic communication between adjacent cells. It is a structural feature, not a hormone.

C. A chemical messenger transported by the bloodstream that stimulates target cells in another organ often a good distance away:This accurately defines a hormone. Hormones are secreted by endocrine glands into the blood and travel to distant target cells, eliciting specific physiological responses.

D. Chemical messengers that travel across a synapse to stimulate another cell:This describes neurotransmitters, which act locally at synapses rather than being transported through the bloodstream.

E. Chemical messengers that diffuse from their point of origin locally to affect other cells physiology:This describes paracrine signaling, which is local and short-range. Hormones, in contrast, typically act on distant cells via the circulatory system.