Chapter 15 Hormones. Objectives n Students should be able to: –Define a hormone as a chemical...

Chapter 15Chapter 15

HormonesHormones

ObjectivesObjectives Students should be able to:Students should be able to:

– Define a Define a hormonehormone as a chemical as a chemical substance, produced by a gland, carried substance, produced by a gland, carried by the blood, which alters the activity of by the blood, which alters the activity of one or more specific target organs and is one or more specific target organs and is then destroyed by the liverthen destroyed by the liver

– Explain what is meant by a endocrine Explain what is meant by a endocrine gland, with reference to the islets of gland, with reference to the islets of Langerhans in the pancreasLangerhans in the pancreas

State the role of the hormone State the role of the hormone adrenalineadrenaline in boosting blood glucose in boosting blood glucose levels and give examples of situations levels and give examples of situations in which this may occurin which this may occur

Explain how the glucose concentration Explain how the glucose concentration is regulated by is regulated by insulininsulin and and glucagonglucagon as as a homeostatic mechanisma homeostatic mechanism

Describe the signs such as an Describe the signs such as an increased blood glucose level and increased blood glucose level and glucose in urine, and the treatment of glucose in urine, and the treatment of diabetes mellitusdiabetes mellitus using insulin using insulin

Living with stressLiving with stress

Butterflies in your stomach?Butterflies in your stomach? Increase in pulse rate?Increase in pulse rate? Sweaty hands which feel cold and Sweaty hands which feel cold and

clammy?clammy?– Why?Why?– Because we are nervous and our body is Because we are nervous and our body is

preparing for actionpreparing for action

Such symptoms are induced by the Such symptoms are induced by the hormone ADRENALINEhormone ADRENALINE

Adrenaline:Adrenaline:– Increases the heart rateIncreases the heart rate– Increases the rate of breathingIncreases the rate of breathing– Causes vasoconstriction of the blood Causes vasoconstriction of the blood

vessels around the intestine (why?)vessels around the intestine (why?)– Raises the metabolic rate?Raises the metabolic rate?– Dilates the pupilsDilates the pupils

15.1 Hormones15.1 Hormones A hormone is a chemical substance A hormone is a chemical substance

produced in minute quantities by an produced in minute quantities by an endocrine gland. It is transported in endocrine gland. It is transported in the bloodstream to target organ(s) the bloodstream to target organ(s) where it exerts its effectswhere it exerts its effects

Hormones influence the growth, Hormones influence the growth, development and activity of an development and activity of an organismorganism

Some hormones also exercise control Some hormones also exercise control over other glands or muscles over other glands or muscles

Where are hormones produced? Where are hormones produced?

Hormones are produced by Hormones are produced by glandsglands

Hormones are produced by Hormones are produced by ductless ductless glandsglands. This means that the . This means that the hormones which the glands produce hormones which the glands produce passes directly into the bloodstream passes directly into the bloodstream which then distributes the hormones which then distributes the hormones round the bodyround the body

Some glands are purely endocrine Some glands are purely endocrine glands producing only hormones (e.g. glands producing only hormones (e.g. adrenal gland produces only adrenaline)adrenal gland produces only adrenaline)

There are glands that produce both There are glands that produce both hormones and other secretions. Can you hormones and other secretions. Can you think of one?think of one?

Hormones production must be Hormones production must be balanced to ensure that body balanced to ensure that body functions normallyfunctions normally

After hormones have performed their After hormones have performed their functions, they are eventually functions, they are eventually destroyed by the liver and excreted destroyed by the liver and excreted by the kidneysby the kidneys

Chapter 15 HormonesGlands and Their Hormonal SecretionsApril 20, 2023

Glands and Their Hormonal Secretions

HypothalamusAn endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH).

Glands and Their Hormonal SecretionsHypothalamusAn endocrine gland that regulates the secretion of some pituitary hormones.



Thyroid glandSecretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development.





Adrenal gland (medulla)Secretes adrenaline. Adrenaline has wide-ranging effects that prepare the body for ‘fight or flight’ situations.

kidney






PancreasIslets of Langerhans in the pancreas secrete insulin and glucagon that regulate the blood glucose concentration.

kidney







kidney


Ovaries (in females) Secretes oestrogen and progesterone.






kidney


Ovaries (in females) Secretes oestrogen and progesterone.

Testes (in males) Secretes testosterone.

Chapter 15 HormonesHow Adrenal Medulla Responds to StimuliApril 20, 2023

April 20, 2023 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 20

StimuliFear, anger, anxiety, stress, etc

1

How Adrenal Medulla Responds to Stimuli



1Receptor

Hypothalamus stimulated

2




12


Receptor


3 sensory neurone

Certain sensory neurones in the hypothalamus are activated



12


Receptor


3 sensory neurone

spinal cord

Nerve impulses are transmitted to the spinal cord

4



12


Receptor


5

3

adrenal medulla

sensory neurone

spinal cordNerve impulses leave the spinal cord to adrenal medulla

4



12


Receptor


6

5

3

adrenal medulla

sensory neurone

spinal cord

Adrenal medulla is stimulate, producing adrenaline.

4



12


Receptor


6

5

3

adrenal medulla

sensory neurone

Adrenaline is carried in blood

7

spinal cord

4



12


Receptor


6

5

3

adrenal medulla

sensory neurone

Adrenaline is carried in blood

7

spinal cord

Adrenaline reaches target organs in various parts of the body. It brings about short-term responses that prepare the body for ‘fight or flight’.

8

4

Effects of adrenaline secretionEffects of adrenaline secretion Increases blood glucose levels by Increases blood glucose levels by

speeding up the breakdown of glycogen speeding up the breakdown of glycogen to glucose in the liver and musclesto glucose in the liver and muscles

Increases metabolic rate (more energy Increases metabolic rate (more energy released)released)

Increases rate of heartbeatIncreases rate of heartbeat Constricts arteries in skinConstricts arteries in skin Causes pupils to dilate to enhance visionCauses pupils to dilate to enhance vision Contracts hair muscles producing ‘goose Contracts hair muscles producing ‘goose

pimples’pimples’

Effects of InsulinEffects of Insulin

Secreted by Islets of Langerhans in Secreted by Islets of Langerhans in pancreaspancreas

Secretion caused by an increase in Secretion caused by an increase in concentration of blood glucose above concentration of blood glucose above the normal levelthe normal level

Effect(s):Effect(s):– Decrease in blood glucose concentration Decrease in blood glucose concentration

by:by: Increasing the permeability of cell membranes Increasing the permeability of cell membranes

to glucose thereby increasing the rate of to glucose thereby increasing the rate of glucose uptake by cellsglucose uptake by cells

Causing the conversion of glucose to glycogen Causing the conversion of glucose to glycogen for storage in liver and musclesfor storage in liver and muscles

Causing an increased oxidation of glucose Causing an increased oxidation of glucose during tissue respirationduring tissue respiration

– This leads to an overall increase in the This leads to an overall increase in the utilization of glucose by cellsutilization of glucose by cells

Lack of secretion:Lack of secretion:– Glucose cannot be utilized by cells, some Glucose cannot be utilized by cells, some

lost in urine => diabetes mellituslost in urine => diabetes mellitus– Muscle cells no reserves of glycogen, Muscle cells no reserves of glycogen,

body weakness flows and then loss of body weakness flows and then loss of weightweight

– Body oxidizes fats instead of glucose to Body oxidizes fats instead of glucose to produce energy resulting in poisonous produce energy resulting in poisonous substances formedsubstances formed

Effects of OversecretionEffects of Oversecretion– Abnormal decrease in blood sugar Abnormal decrease in blood sugar

concentrationconcentration– Shock HAPPENSShock HAPPENS– Coma and death may followComa and death may follow

Diabetes mellitusDiabetes mellitus

A disease where the body is unable to A disease where the body is unable to control its blood glucose concentration control its blood glucose concentration so that it remains within normal limits.so that it remains within normal limits.

Kidneys unable to reabsorb all the Kidneys unable to reabsorb all the glucose, hence some gets excreted in glucose, hence some gets excreted in the urinethe urine

2 Types of diabetes:2 Types of diabetes:

Type 1:Type 1:– Juvenile diabetes. Inability of the pancreas Juvenile diabetes. Inability of the pancreas

to produce insulinto produce insulin Type 2:Type 2:

– Occurs later in life. Overweight people Occurs later in life. Overweight people seem more prone to it. May be due to a seem more prone to it. May be due to a decrease in the production of insulindecrease in the production of insulin by by the pancreas or a the pancreas or a failure of the target cells failure of the target cells to respond well to itto respond well to it. .

SignsSigns– Persistently high blood glucose level Persistently high blood glucose level – Glucose in urine after a mealGlucose in urine after a meal– Healing of wounds is slow or difficultHealing of wounds is slow or difficult

TreatmentTreatment– Measure blood glucose concentrations Measure blood glucose concentrations

and test urine regularlyand test urine regularly– Watch their diet, take less carbohydratesWatch their diet, take less carbohydrates– Inject insulin into veins (Type 1)Inject insulin into veins (Type 1)– Control intake of carbohydrate (Type 2) Control intake of carbohydrate (Type 2)

GlucagonGlucagon Produced by Produced by islets of Langerhansislets of Langerhans when when

the concentration of blood glucose the concentration of blood glucose decreases below the normal levelsdecreases below the normal levels

Target organ of glucagon is Target organ of glucagon is LiverLiver Glucagon increases the blood glucose Glucagon increases the blood glucose

concentration by stimulating:concentration by stimulating:– The conversion of glycogen into glucoseThe conversion of glycogen into glucose– The conversion of fats and amino acids The conversion of fats and amino acids

into glucoseinto glucose– The conversion of lactic acid into glucoseThe conversion of lactic acid into glucose

Hormonal & Nervous ControlHormonal & Nervous Control

Both serve as a means of co-ordination Both serve as a means of co-ordination within the bodywithin the body

There are differences between the 2 There are differences between the 2 systems though:systems though:

Chapter 15 Hormones. Objectives n Students should be able to: –Define a hormone as a chemical...

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