hormones 2013 hbl

8/10/2019 Hormones 2013 HBL

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HORMONES.

Pupils should be able to :

1.Define hormone as a chemical substance, produced

by a gland, carried by the blood, which alters the

activity of one or more specific target organs and isthen destroyed by the liver.

2.Explain what is meant by an endocrine gland, with

reference to the islets of Langerhans in the pancreas


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3. State the role of the hormone adrenaline in

boosting blood glucose levels and give examples

of situations in which this may occur.

4. Explain how the blood glucose concentration is

regulated by insulin and glucagon as a

homeostatic mechanism.

5. Describe the signs such as an increased blood

glucose level and glucose in urine and the

treatment of diabetes mellitus using insulin.

SIOs in pale green not in Sci Bio


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Co-ordination of the human body is brought about by

Nervous and

hormonal control

http://www.abpischools.org.uk/page/modules/hormones/index.cfm?coSiteNavigation_allTopic=1


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- where it alter theactivity of those organs

- After which it is destroyed in the liver

What is a hormone?

- its a chemical substance (protein, polypeptide, steroid oramines)produced in minute amts by endocrine(ductless) glands

- to be transported to one or more specific target organs

- secreted directly into the blood


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- Important in homeostatic control where thestimulus is mainly from the bodys internal envimt.

- Change in internal environment detected mainly byhypothalamus

- which then directs the endocrine gland/s involvedto secrete the appropriate hormone

- Serious deficiencies or excessesof hormoneproduction give rise to illnesses


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Secretes thyroxine

& triiodothyronin

regulate growth &

developmt of cells

Anterior pituitary gland

- Produces 6 hormones

- most have other endocrineglands as their target organs

- Also releases growth hormone

Posterior pituitary gland

- stores 2 hormones

- ADH & oxytocin prod by

hypothalamus

Master gland cos it orchestrates

the productn of hormones from

other endocrine glands


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Two kinds of glands

EXOCRINE glandGlands with ducts are called

exocrine glands. Eg salivary gland

ENDOCRINE glandductless glands. Do not have a

duct to carry away the secretion

eg adrenal glands


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PANCREAS- Is an exocrine glandwhich secretes enzymeinto

the duodenum through the pancreatic duct

-Is also an endocrine gland(ductless)the hormone producing cells are arranged in smallisolated groups called islets

- Islets of Langerhansin the pancreas produce the

hormone insulin


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After food, blood glucose level increases.

Blood normally contains about 70 90mg of

glucose per 100cm3of blood

Pancreas detects and secretes insulin to bring thglucose level down.


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Effects of INSULIN

1.Increases the permeability of cell membranesto glucose and thus increases the rate of glucose

uptake by cells

2. Causes the conversion of excess glucose toglycogen for storage in liver and muscles

3. Causes an increased oxidation of glucoseduringtissue respiration

All these changes decreases blood glucose concentration


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If blood glucose level drops, the hormoneglucagonis released.

Glucagonacts mainly on the liver cells.

During vigorous muscular contraction or

during starvation, glucose level drops


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Blood glucose level below 40mg/100cm3affectsbrain cells - lead to convulsion and coma

Conversion of the stored glycogen into glucose

Conversion of fats and amino acids into glucose

Effects of Glucagon

- Stimulates the :

Conversion of lactic acid into glucose


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What happens when there is a deficiency ininsulin production?

- result in Diabetes mellitus

SIGNS :urine contains glucose

persistentlyhigh blood glucose level

TREATMENT :diet must be carefully monitoredtreated by injecting insulininto veinscannot take insulin orally because as a protein, itwould be broken down by digestive enzymes


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A person suffering from diabetes mellitus tendsto :

lose weight and show muscular weaknessdue to

- inability to convert glucose to glycogen for storage inmuscles and liver

- cells unable to absorb glucose well for tissue respiratio

body oxidises fats instead of glucose- results in production of ketones which can lower

bloods pH and cause death if too much accumulates

become dehydrated- excess glucose excreted via kidneys and this leads tomuch loss of water resulting in thirst


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ADRENALINE

Produce by adrenal medulla of the adrenal gland,

situated above the kidneys

secreted when person is infear, anger, anxiety

adrenal glands controlled bythe nervous system

prepare body for fight orflight reactions


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Stimuli

Fear,

anger,

anxiety,

stress, etc

1

2

How Adrenal Medulla Responds to Stimuli

Receptor

Hypothalamus stimulated

6

5

3

adrenal

medulla

sensoryneurone

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

adrenal

cortex

Certain sensory

neurones in the

hypothalamus are

activated

Nerve impulses

leave the spinal

cord to adrenal

medulla


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Effects of Adrenaline :

1. Speeds up the breakdown of glycogen toglucosein liver and muscles - thus more glucose ismade available for tissue respiration

2. Increases metabolic rate- more E released intissue respiration

3. Increases rate of heartbeat- so that O2 andglucose can be carried to the muscles quickly


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5. Constricts arterioles in skin(causing pallor) - moreblood can be channelled to the muscles and lungs

6. Pupils dilate- let more light into eye to form brighte images; help to detect visual danger signals in

surroundg

4. Increases breathing rate- so that more O2 can beabsorbed into blood in the lungs and CO2 can beremoved quickly

hormones 2013 hbl

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