Chapter 15 Hormones & Endocrine Glands - Lecture Notes

Chapter 15: Hormones & Endocrine Glands Students should be able to: 1. 2.

Define hormones. State the principal roles of hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occur. Describe the signs (increased blood glucose level, glucose in urine) and treatment (administration of insulin) for those with diabetes mellitus.

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15.1 Coordination by Hormonal & Nervous Control Types of Coordination Nervous

Coordinating Messages are transmitted using Coordinating Messages are transmitted through

Impulses (Electrical)

Hormones (chemical substances)

Neurones (nerve cells)

Blood

The response is usually • Rapid • Usually localized (affect only a small area / small group of muscles)

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Hormonal

The response is usually • Slow • May affect more than one target organ

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 hormones

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o Sex hormones (testosterone in males/oestrogen in females) o ***“Fight or Flight” hormone (adrenaline) o ***Regulate blood glucose concentration (insulin)

15.2 Action of Adrenaline • 15.2.1

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Generally, responses triggered by hormones are not as fast as nervous responses, except Adrenaline (The “fight or flight” hormone) 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 action o Hence it is called “fight” or “flight” hormones

15.2.2

Summary of Effects of Adrenaline

Target Organ Liver

Heart

Effects of adrenaline 1) Increases rate of conversion of: Glycogen  Glucose 2) Arterioles dilate (become wider) 1) Rate & Force of heartbeat increases 2) Arterioles dilate

Breathing center of brain and gaseous exchange organs

1) Breathing rate increases 2) Arterioles in lungs dilate

Muscles (skeletal)

1) Become tense 2) Arterioles dilate

Purpose & results 1) To increase blood sugar level so that more glucose is available for energy production (esp in muscles) 2) Person feels active 1) Send more blood containing oxygen and glucose to skeletal & heart muscles 2) Heart thumps rapidly 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 it 2) Person breathes rapidly (panting) 1) To prepare them for immediate action and increase blood flow to them 2) Person trembles and feels tense

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Blood vessels of skin & gut

Constrict (diameter becomes smaller)

Eye: radial muscles or iris

Contract  Pupils (opening) become bigger

1) Send less blood to these regions so more blood can flow to the muscles, liver and lungs 2) Person looks pale, mouth becomes dry 1) To allow more light to enter eye to form brighter images  helps to detect visual dangers in surroundings 2) Pupils dilate

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15.3 Action of Insulin 15.3.1

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Insulin Where it is produced  islets of Langerhans in the pancreas When it is produced  Stimulus: Increase in blood glucose level

15.3.2

Effect of insulin

High blood glucose level detected in Islets of Langerhans secretes insulin Insulin 1) Converts excess glucose  glycogen 2) Stimulate absorption of glucose by cells  so it could be broken down for respiration 15.3.3

Blood glucose level returns to normal

Glycogen stored in liver & muscles

Effect of Lack of Insulin o Without insulin, body cannot use or store glucose o As a result  blood glucose increase above normal  excess glucose are excreted in urine o This disorder is called diabetes mellitus

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Diabetes Mellitus Symptoms: o High blood glucose level o Presence of glucose in urine The person who suffer from the condition tends to o 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)

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o If left untreated  lead to diabetic shock / coma or death

o Treatment: Diet control & taking regular doses of insulin via injection

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