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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
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