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Unit 4: Respiration &
coordination
4.2 Chemical coordination in animals
By Mr. Wilson
Hormones
• From Greek ‘To Set In Motion’.
• Chemical messenger from one cell/group
of cells to another.
• Mainly secreted from endocrine glands
into bloodstream to act on distant organs.
• Rate of production often linked to a
negative feedback system.
• Neurones may stimulate production.
Major endocrine glands
(Male left, female on
the right.) 1. Pineal
gland 2. Pituitary
gland 3. Thyroid
gland 4. Thymus 5.
Adrenal gland 6.
Pancreas 7. Ovary
8.Testis
Actions of hormones
• Hormone actions vary widely, but can include stimulation
or inhibition of growth, induction or suppression of
apoptosis (programmed cell death), activation or
inhibition of the immune system, regulating metabolism
and preparation for a new activity (e.g., fighting, fleeing,
mating) or phase of life (e.g., puberty, caring for
offspring, menopause). In many cases, one hormone
may regulate the production and release of other
hormones. Many of the responses to hormone signals
can be described as serving to regulate metabolic
activity of an organ or tissue. Hormones also control the
reproductive cycle of virtually all multi-cellular organisms.
Action of a steroid hormone
Control of blood glucose
• Two hormones involved: Glucagon from
alpha Islet of Langerhans cells & Insulin
from beta Islet of Langerhans cells in
pancreas.
• Vocabulary – Glycogenolysis,
gluconeogenesis, deamination,
glycogenesis
• Copy the diagram of how hormones may
activate specific enzymes in cells.
Negative feedback & blood glucose
A negative feedback mechanism
• Show your understanding of negative
feedback with a simple diagram to show
how the temperature of a water bath is
maintained by a thermostat.
• Why is it called negative feedback?
Explaining negative feedback
Antidiuretic hormone (ADH)
• Involved in osmoregulation (control of
body water).
• Operates on a principle of negative
feedback.
• Receptors (osmoreceptors) are in
hypothalamus.
• ADH makes distal convoluted tubule and
collecting duct of nephrons MORE
permeable to water.
Osmoregulation
Reproductive hormones
• Research which hormones are involved in
bringing about secondary sexual
characteristics and controlling various
stages of reproduction and pregnancy.
• Where produced, target tissue/organs and
effect.
• You may want to present this information
in a table for clarity.