Chapter 15: Hormones & Endocrine Glands

Students should be able to:

1. Define hormones.2. State the principal roles of hormone adrenaline in boosting blood

glucose levels and give examples of situations in which this may occur.

3. Describe the signs (increased blood glucose level, glucose in urine) and treatment (administration of insulin) for those with diabetes mellitus.

15.1 Coordination by Hormonal & Nervous Control

Types of Coordination

Just like nervous control, hormones are also produced in response to a stimulus

***Definition of hormones:o A chemical substance produced in minute (small) amounts

By endocrine glands and secreted directly into the blood To be transported to one or more target organs Where it carries out its effect by controlling metabolism,

growth, sexual reproduction and other body processes After which it is destroyed in the liver

o Looking at the definition of hormones, are there any differences between it and enzymes?

Types of Hormones:o Growth hormoneso Sex hormones (testosterone in males/oestrogen in females)

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Nervous Hormonal

Impulses (Electrical) Hormones (chemical substances)

Coordinating Messages are transmitted using

Neurones (nerve cells) BloodCoordinating Messages are transmitted through

The response is usually Rapid Usually localized

(affect only a small area / small group of muscles)

The response is usually Slow May affect more than one

target organ

o ***“Fight or Flight” hormone (adrenaline)o ***Regulate blood glucose concentration (insulin)

15.2 Action of Adrenaline

Generally, responses triggered by hormones are not as fast as nervous responses, except Adrenaline (The “fight or flight” hormone)

15.2.1 Adrenaline Where it is produced adrenal glands, situated above the kidneys When it is produced Stimulus such as

o Anger o Anxious o Excitement o Frustration / Stress

Adrenaline is produced to prepare the body for fast / rapid actiono Hence it is called “fight” or “flight” hormones

15.2.2 Summary of Effects of Adrenaline

Target Organ Effects of adrenaline Purpose & resultsLiver 1) Increases rate of

conversion of: Glycogen Glucose2) Arterioles dilate (become wider)

1) To increase blood sugar level so that more glucose is available for energy production (esp in muscles)2) Person feels active

Heart 1) Rate & Force of heartbeat increases2) Arterioles dilate

1) Send more blood containing oxygen and glucose to skeletal & heart muscles2) Heart thumps rapidly

Breathing center of brain and gaseous exchange organs

1) Breathing rate increases2) Arterioles in lungs dilate

1) To breathe in more air and increase blood flow to lungs so that more oxygen is absorbed into blood & more carbon dioxide is got rid of from it2) Person breathes rapidly (panting)

Muscles (skeletal)

1) Become tense2) Arterioles dilate

1) To prepare them for immediate action and increase blood flow to them2) Person trembles and feels tense

Blood vessels of skin & gut

Constrict (diameter becomes smaller)

1) Send less blood to these regions so more blood can flow to the muscles, liver and lungs

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2) Person looks pale, mouth becomes dry

Eye: radial muscles or iris

Contract Pupils (opening) become bigger

1) To allow more light to enter eye to form brighter images helps to detect visual dangers in surroundings2) Pupils dilate

15.3 Action of Insulin

15.3.1 Insulin Where it is produced islets of Langerhans in the pancreas

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When it is produced Stimulus: Increase in blood glucose level

15.3.2 Effect of insulin

15.3.3 Effect of Lack of Insulino Without insulin, body cannot use or store glucoseo As a result blood glucose increase above normal excess

glucose are excreted in urineo This disorder is called diabetes mellitus

15.3.4 Diabetes Mellituso Symptoms:

o High blood glucose levelo Presence of glucose in urine

o The person who suffer from the condition tends too Become dehydrated because when glucose is excreted in

urine, an equivalent amount of water has to be excreted Interferes with the water reabsorption in the nephrons (See Chapter on Excetion)

o Lose weight and show muscular weakness because body cells turn to proteins and fats for energy supply (since cells cannot absorb glucose and unable to use glucose to produce energy)

o If left untreated lead to diabetic shock / coma or deatho Treatment: Diet control & taking regular doses of insulin via

injection

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High blood glucose level detected in hypothalamus

Islets of Langerhans secretes insulin

Insulin 1) Converts excess glucose glycogen2) Stimulate absorption of glucose by cells so it could be broken down for respiration

Glycogen stored in liver & muscles

Blood glucose level returns to normal