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Hormones

Boardworks Ltd 2004

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KS4 BiologyHormones

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Contents Hormones The endocrine system Endocrine glands Blood glucose regulation Summary quiz

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What exactly are hormones?

What effect do hormones have on the body? Hormones and the endocrine system To understand hormones you need to know about the endocrine system and how it works.

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The endocrine system coordinates the bodys organs so that they work together.

The endocrine system is based on the production of chemical messengers called hormones.

Hormones are produced by glands (endocrine glands) in different parts of the body. These chemical messengers are produced in very small quantities and are transported in the blood. The endocrine systemHormones control body processes that require several organs of the body to interact for a combined effect.

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What do hormones do?Hormones travel slower than nervous impulses but cause longer-lasting effects.Over- or under-activity of some endocrine glands can cause functional disorders such as diabetes.They are delivered to all parts of the body but can have local effects.

Hormones are used to stabilize the bodys internal environment through homeostasis and also coordinate longer-term processes such as growth and sexual development.

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Which body system?

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Contents The endocrine system Endocrine glands Blood glucose regulation Hormones Summary quiz

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Produces the hormone thyroxine:

Regulates rate of metabolism.

Excess causes hyperactivity.

Deficiency causes weight gain and sluggishness. Endocrine glands thyroidthyroid

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Endocrine glands adrenal glandsadrenal glandsProduce the hormone adrenalin.

Adrenaline causes the fight or flight response resulting in:

Increased heart rate and breathing rate.

Blood diverted to the muscles.

Increased respiration to increase the amount of glucose in the blood.

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ovaries Endocrine glands reproductive organsIn females, ovaries produce several hormones:

oestrogenControls the development of female secondary sexual characteristics.

Regulates menstrual cycle.

progesterone Thickens uterine wall.

Prevents contractions until a baby is being born.

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testes Endocrine glands reproductive organsIn males, testes produce the hormone testosterone:

Promotes the development of male secondary sexual characteristics.

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Endocrine glands pancreas pancreasProduces the hormone insulin:

Controls the conversion of blood glucose to insoluble glycogen, which is stored in the liver.

Increases metabolic rate by stimulating cellular glucose uptake.

Increases protein synthesis in some cells.

Deficiency causes the condition sugar diabetes, where the blood sugar level is unregulated.

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Produces the hormone glucagon:

Controls the conversion of insoluble glycogen to glucose in the liver. Endocrine glands pancreaspancreas

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pituitary glandProduces several hormones:

growth hormonePromotes bone and muscular growth.

antidiuretic hormone (ADH)Controls reabsorption of water into the blood by kidneys.

thyroid stimulating hormone (TSH)Controls the endocrine function of the thyroid gland. Endocrine glands pituitary gland

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pituitary glandProduces several specific hormonesin females:

follicle stimulating hormone (FSH)Causes the follicle in the ovary to develop and secrete oestrogen.

luteinizing hormone (LH)With FSH and other hormones causes ovulation. Endocrine glands pituitary gland

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Name that gland

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Match hormones to glands

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Contents The endocrine system Endocrine glands Blood glucose regulation Hormones Summary quiz

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Some hormones affect only one target organ, but most affect more than one.

When the hormone has had the desired effect, further production of the hormone needs to be controlled.

Hormone production is controlled by a process called negative feedback.

The regulation of blood glucose level is an example of negative feedback. Negative feedback

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and the liver are all involved in regulating blood glucose.The brain, the pancreas Negative feedback blood glucoseWhich of these parts of the body are involved in the negative feedback process that regulates blood glucose?

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Negative feedback high blood glucoseThe brain detects the level of glucose in the blood.

When the level of blood glucose increases above normal, what hormone does the pancreas release?increased blood glucose

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Negative feedback high blood glucoseThe pancreas is stimulated to release insulin. What effect does this have?

The insulin stimulates the liver to take glucose from the blood and convert into glycogen, which is stored in the liver.insulinincreased blood glucose

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The level of glucose in the blood decreases, causing the pancreas to stop producing insulin.

What would happen if the pancreas kept on producing insulin?blood glucose returns to normal Negative feedback high blood glucoseincreased blood glucoseinsulin

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Negative feedback also occurs when the blood glucose level decreases below normal.

This time the brain detects decreased blood glucose and so the pancreas is stimulated to release which hormone? Negative feedback low blood glucosedecreased blood glucose

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The pancreas produces the hormone glucagon.

Glucagon stimulates the liver to convert glycogen back to glucose and release this glucose into the bloodstream. Negative feedback low blood glucosedecreased blood glucoseglucagon

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The level of glucose in the blood increases, causing the pancreas to stop producing glucagon.

What would happen if the pancreas kept on producing glucagon? Negative feedback low blood glucosedecreased blood glucoseblood glucose returns to normalglucagon

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Blood glucose activity

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When hormones go wrong diabetesWhat happens if the pancreas is unable to produce the hormone insulin?After a person with diabetes has eaten, their blood glucose level increases. What happens to this glucose?

The absence of insulin means that glucose is not converted to glycogen and stored in the liver, so the blood of adiabetic contains extra glucose.

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When hormones go wrong diabetesGlucose is essential for the body, so why is excess glucose a danger for people with diabetes? When the glucose is used up, coma and convulsions may occur. So how is diabetes controlled?

Regular insulin injections and a careful diet can control the condition.

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Contents The endocrine system Endocrine glands Blood glucose regulation Hormones Summary quiz

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Multiple-choice quiz