The Endocrine System

2 Contents Hormone Endocrine & exocrine glands Types of hormones Functions of hormones The endocrine glands in the human Hypothalamus Pituitary gland Glands, Hormones & Functions Undercativity of the pituitary gland Overactivity of the pituitary gland Diabetes mellitus Feedback mechanism of hormonal control Hormonal Vs Nervous Communication Similarities Differences

3 Hormone hormone: a substance (chemical message) produced by an endocrine gland secreted directly into and transported by the blood stream to other parts (target organs) of the body where it evokes a response.

4 Endocrine & exocrine glands endocrine gland: ductless gland - secretions (hormones) delivered directly into bloodstream e.g. pituitary, thyroid, parathyroid, pancreas, adrenal, ovary and testis. exocrine gland: a gland which delivers its secretion through a tube or duct - does not depend on blood stream - e.g. liver, pancreas, sweat glands and salivary glands.

5 Types of hormones Protein or protein-like nature e.g. insulin – attach to proteins on the surface membranes of their target organs and cause a response. Steroids e.g. oestrogen (similar structure to cholesterol) – enters the cells of the target organ – affects the nucleus and caused the cell to produce specific proteins – a slower response.

6 Function of hormones to regulate the activities of the various body systems e.g. cell metabolism (blood sugar levels – insulin)

7 The endocrine glands in the human

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9 Thyroid and Parathyroid location

10 Hypothalamus Monitors the blood – pH, temperature, hormone levels Hormones released by hypothalamus travel to pituitary and cause it to release hormones. Produces TRH (thyroid releasing hormone) which stimulates the pituitary to release TSH.

11 Position of hypothalamus and pituitary gland

12 Pituitary gland Releases hormones that control other glands e.g. TSH (thyroid stimulating hormone) stimulates the thyroid gland to release thyroxine, which increases cell metabolism. Releases hormones that control other organs e.g. growth hormone

13 Glands, Hormones & Functions

14 Under activity of the pituitary gland If the pituitary of a child does not produce enough growth hormone – this person will not grow = a pituitary dwarf. Can be cured with growth hormone injections (must be given before normal growth stops)

15 Over activity of the pituitary gland If the pituitary of a child produces too much growth hormone – this person will grow very large = a pituitary giant – often due to a pituitary tumour). Can be stopped by removing the tumour (will not reduce growth that has already taken place)

16 Diabetes mellitus diabetes mellitus: sugar in urine and excessive urine production caused by an inadequate production of insulin by the pancreas. Affected people can monitor their blood sugar levels and inject themselves with insulin when their sugar levels are rising.

17 The control mechanism for the production of thyroxine

18 Hormonal Vs Nervous Communication SIMILARITIES Both provide a means of communication within the body. Both involve the transmission of a message, which is triggered by a stimulus and produces a response.

19 Similarities continued The target organs of a hormone are equivalent to a nerve's effector. Both involve chemical transmission - the transmission of the message across the synapse is achieved by acetylcholine (chemical messenger), which is equivalent to a hormone in the endocrine system.

20 Hormonal Vs Nervous Communication – Differences Chemical substance sent through blood stream Responses usually slow Hormones carried to all parts of the body Responses often widespread - involving many target organs Responses may continue over a long time Action potential sent along nerve fibre Response usually rapid Impulse transmitted to specific destinations Responses may be localised - involving only one muscle Responses usually rapid and short-lived

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