1. Chemical Control in Mammals
C/W /10/2016
Understand the principles of mammalian hormone production by endocrine glands and their mode of action involving receptors on target cells.
Know that there are two main modes of action in hormones:
Hormones attach to receptor sites and trigger the release of a second messenger that activates specific enzymes in the cell, including adrenaline
Hormones enter cells and bind directly to transcription factors, including oestrogen

2. Chemical control in mammals
Understand the principles of mammalian hormone production by endocrine glands and their mode of action involving receptors on target cells.
Chemical control in mammals
Chemical control in animals is brought about through hormones. These are organic chemicals produced in endocrine glands and released into the blood. Hormones are usually either proteins or peptides (e.g. insulin, antidiuretic hormone, adrenaline) or steroids (e.g. sex hormones oestrogen and testosterone)
Travel in the blood stream and act on target cells.
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3. Endocrine vs Exocrine Exocrine Endocrine
Maintain contact with the body surface
Ducts
Tear glands
Sweat glands
Mammary glands
No contact with body surface
No ducts
Hormones secreted directly into blood stream
Some organs have both exocrine and endocrine functions e.g. Pancreas
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4. Types of Hormone Steroid Peptide Tyrosine derivative
Oestrogen – increases thickness of uterine lining
Peptide
Insulin – Promotes glucose uptake by body cells
Adrenaline – Fight or flight responce
Tyrosine derivative
Thyroxine – increases metabolic rate

5. Hypothalamus
The hypothalamus plays an important role in integrating the nervous and endocrine systems in order to maintain homeostasis
It receives information from nerves throughout the body and other parts of the brain and initiates appropriate endocrine responses
The hypothalamus controls the release of hormones via the pituitary gland, which is comprised of two distinct lobes:
Anterior lobe
Posterior lobe

6. The pituitary gland and the hypothalamusLH
FSH
ACTH GH
ADH
Oxytocin

7. Checkpoint
Hormones attach to receptor sites and trigger the release of a second messenger that activates specific enzymes in the cell, including adrenaline
Hormones enter cells and bind directly to transcription factors, including oestrogen
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8. Protein Hormones – e.g. Adrenaline
Cannot enter target cells (are lipophobic)
Binds to receptors on the surface of the plasma membrane, which activates second messengers within the cell
Acts indirectly to change cellular activity (via signal transduction pathways)
Animation -

9. Cyclic AMP (cAMP) made from ATP Increased cellular respiration
Second Messengers
Cyclic AMP (cAMP) made from ATP
Increased cellular respiration
Increased contraction of muscles
Relaxation of smooth muscle in blood vessels
Adrenaline - fight or flight response!
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10. Checkpoint
Hormones attach to receptor sites and trigger the release of a second messenger that activates specific enzymes in the cell, including adrenaline
Hormones enter cells and bind directly to transcription factors, including oestrogen
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11. Steroid Hormones – E.g. Oestrogen
Enter target cells through the plasma membrane (are lipophilic)
Bind to receptor proteins in the cytoplasm and form a steroid / receptor complex which affects gene expression
Can act directly as a transcriptional regulator
Animation -

12. Checkpoint
Hormones attach to receptor sites and trigger the release of a second messenger that activates specific enzymes in the cell, including adrenaline
Hormones enter cells and bind directly to transcription factors, including oestrogen
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13. Checking understanding
Draw a labelled diagram (your teacher will help you) to illustrate how hormones such as adrenaline work via the second messenger mechanism
Draw a labelled diagram to illustrate how hormones such as Oestrogen act as transcription factors.
Sketch your diagram out on the white board first and get this checked by your class teacher before you move on.
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14. Key Definitions
Pituitary Gland – A small gland in the brain that has an anterior lobe and posterior lobe and produces and releases secretions that affect the activity of most other endocrine glands in the body.
Hypothalamus – Small areas of brain directly above the pituitary gland that controls the activities of the pituitary fland and coordinates the autonomic (unconscious) nervous system
Neurosecretory cells – Nerve cells that produce secretion from the ends of their axons. These secretions either stimulate or inhibit the release of hormones from the anterior pituitary, or are stored in the posterior pituitary and then later released as hormones.
Cyclic AMP (cAMP) – Compound formed from ATP that is produced when protein hormones such as adrenaline bind to membrane receptors and acts as a second messenger in cells.
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15. Exam Questions
1. Distinguish between the mode of action of steroid hormones and peptide hormones. [4 marks]
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16. Mark Scheme
Distinguish between the mode of action of steroid hormones and peptide hormones. [4 marks]
Responses must include reference to both steroid and peptide hormones.
Award [3 max] for: enter target cells via receptors / pass through plasma / cell membrane; steroid hormones bind to (receptor) proteins in the cytoplasm; steroid hormones hormone receptor complexes affect genes; steroid hormones control activity and development of target cells;
Award [3 max] for: peptide hormones do not enter cells; peptide hormones bind to receptors in the plasma membrane; peptide hormones act via secondary messengers inside the cell; peptide hormones secondary messenger causes changes in / inhibit enzyme activity;
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17. This relates to the following specification point:
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