Curriculum
Course: SQA National 5 Biology
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Curriculum

SQA National 5 Biology

1. Unit 1 — Cell Biology

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2. Unit 2 — Multicellular Organisms

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3. Unit 3 — Life on Earth

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Text lesson

2.2.4 Hormonal Control

2.2.4 Hormonal Control: Describe how hormones are produced by glands, transported in the blood and act on target cells, and compare hormonal with nervous control.

2.2.4 Hormonal Control
1

A hormone is a chemical messenger produced by an endocrine gland.
2

The gland releases the hormone directly into the bloodstream.
3

The blood carries the hormone around the body, so it reaches all tissues.
4

Only target cells with the matching receptor protein respond to that hormone.
5

The target cells or organs change their activity, producing the effect of the hormone.
6

Target cells have receptor proteins whose shape fits one hormone, which is why each hormone affects only certain cells.
Insulin
  • Made in the pancreas; lowers blood glucose concentration.
Glucagon
  • Made in the pancreas; raises blood glucose concentration.
Adrenaline
  • Made in the adrenal glands; prepares the body for action in the fight-or-flight response.
Testosterone and oestrogen
  • Made in the testes and ovaries and control the development of sexual characteristics.
Thyroid and ADH
  • Other hormones control metabolism and water balance, showing how many body processes depend on chemical messengers.
Nervous vs Hormonal
Speed
  • Nervous responses are very fast, while hormonal responses are slower.
Duration
  • Nervous responses are short-lived, while hormonal effects last longer.
Pathway
  • Nerve impulses travel along neurones; hormones travel through the blood.
Target
  • Nervous signals go to specific effectors, while hormones can affect many cells.
Feature Nervous Hormonal
Signal Electrical impulses Chemical hormones
Travels in Neurones Blood
Speed Fast Slower
Effect lasts Short Longer

2.2.4 – Key Points for the Exam

  • Hormone: A chemical messenger carried in the blood.
  • Endocrine gland: A gland that releases hormones into the blood.
  • Target cell: A cell with receptors for a specific hormone.
  • Adrenaline: A hormone that prepares the body for action.

Common Mistakes

  • Saying hormones travel through nerves; they are carried in the blood.
  • Writing that all cells respond to every hormone; only target cells with receptors do.
  • Describing hormonal responses as faster than nervous ones.
  • Mixing up the sources of insulin and adrenaline.
  • Believing hormones are used up immediately; they act for a longer time before being broken down.
YOUR STUDY PATH

2.2.4 Hormonal Control

SQA National 5 Biology / 2. Unit 2 — Multicellular Organisms

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