Hormones the endocrine system

Endocrine system - hormonesy Transported around the body to regulate bodily

functionsy Most hormones transported by circulatory system

y Hormones are the chemical molecules used to

communicate a message from one part of the body to anothery Transport is via the bloodstream

most hormones y Some act on the cells where they are produced y Some act on nearby cells (extracellular fluid)2

Endocrine system - hormonesy Some act on very specific cells and others act on many y Keep a homeostatic, or relatively stable or constant

internal environment, within narrow limitsy Core body temperature

y Signalling molecules produced by cells and regulate

target cells, usually located elsewhere in the body

y Target cells have receptors that enable them to recognise

the chemical message; other cells ignore the hormone

y Endocrine glands y Ductless glands that secrete hormones directly into the bloodstream3

Endocrine glandsy Pineal y y y y y y y

patterns Hypothalamus (just above pituitary in brain); very many body functions Pituitary control centre Thyroid thyroxin; metabolism Thymus T-cells; immune system Adrenal adrenalin; increases heart rate Pancreas insulin Ovary/testis oestrogen, progesterone/testosterone

melatonin; wake sleep

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Homeostatic mechanismsy Stimulus

Response model

- The intensity of the stimulus needs to be sufficient enough to reach the

threshold of the receptor- Stimulus Effector Response

y Negative feedback systems- The response produced reduces the effect of the original stimulusBlood sugar levels - Calcium ion levels in the blood-

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Negative feedback: Blood sugar levels

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Negative feedback: Calcium ion levels in the blood

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Homeostatic mechanismsy Positive Feedback systems rare homeostatic mechanism- The response produced increases or enhances the effect of the original

stimulus; moving levels out of the normal range- Childbirth contractions

when it starts the pituitary produces oxytocin which causes the uterus to contract and the pitutary to produce more oxytocin - Blood clotting and fibrin production (this causes blood to coagulate; platelets activate its production by releasing an enzyme when in contact with the damaged tissue

y Proportional control systems- Stimulus and response are proportional - Shivering and ambient temperature

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Hormone types all via bloodstreamy Three chemical types of hormones y Amino acid derivative eg thyroid hormonesy y y

Made in advance and stored in secretory vesicles till needed Leave by exocytosis (water soluble) Short lived

y Steroid eg sex hormones; need carrier protein y Made on demand y Leave cell by simple diffusion (lipid based; lipophilic) y Long lived y Peptide and protein (most hormones) insulin and TSH y Made in advance and stored in secretory vesicles till needed y Leave by exocytosis (water soluble) y Short lived9

Hormone types (signal molecules)y Amino acid &

peptide/proteiny Water soluble y Hydrophilic (lipophobic) y Passes easily through

y Steroid y Lipid solubley

Lipophilic (hydrophobic)

y Need carrier protein

bloodstream y Can t pass through target cell membraney y

through bloodstream y Diffuse through target cell membraney

Receptor in cytosol

Receptor on cell surface Needs carrier protein or G protein (second messenger)10

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Cell communicationy Signal transduction y the movement of signals from outside the cell to inside y Can be simple, perhaps creating one molecule y Can produce many intracellular events y Can activate a particular DNA sequence y Once the message is delivered, enzymes break it down

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Plant hormonesy Responsible for: y Growth y Buds starting to grow y Stem length y Roots growing down y Stems growing up y Flowers appearing y Fruit ripening y Move in phloem and

xylem y Small amounts y Found mainly iny Meristem (growing

stems and roots) y Growing young leaves y Growing seeds y Ripening fruit13

Plant hormonesy Can stimulate or inhibit y Produced due to external y 5 groups of plant

hormonesy Auxins y Cytokinins y Gibberellins y Abscisic acid y ethylene

factorsy Temperature y Day length y Light intensity y gravity

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Auxinsy Enlargement and elongation of cells in stems y Lateral and adventitious roots y Promotes flower and fruit growth y Causes specialised cell development y Produced in growing tips of plants y Bending of plant shoots and roots in response to light

and gravity

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Auxinsy IAA is an auxin responsible for apical dominance y IAA moves down phloem y Lateral buds are inhibited from developing y Cutting off the growing tip stops IAA production and

lateral buds start growing y Epicormic buds work in a similar way y Tropism: Growth of a plant in response to a stimulusy Positive = growing towards the stimulus y Negative = growing away from the stimulus16

Auxins - phototropismy Growth of a plant stem

towards light (positive)y Auxin moves away from

the light to the dark side y Auxin promotes cell elongation and growth y This bends the stem towards the light

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Auxin - geotropismy A seed germinates y Auxin produced in the

stem and root moves down due to gravity y Stem has a NEGATIVE response and grows up y Root has a POSITIVE response a grows towards gravity18

Cytokininsy Promotes growth; cell reproduction y Growing stems and roots, and developing fruit

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Gibberellinsy Eg gibberellic acid y Promotes plant growth y Cell elongation and cell reproduction y Stems and leaves y Seed germination y Bud development y Juvenile leaves in some

species (eucalyptus)20

Gibberellinsy Once a seed is wet,

gibberellin produces gibberellic acid y This diffuses into cells, causing DNA to produce amylase y Amylase starts changing starch into glucose, which becomes food for the embryo21

Abscisic acidy Inhibits growth y Abscission layer y Abscission y Dropping fruit y Falling deciduous leaves y Dormant buds y Closes stomata when

plants are stressed

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Ethyleney Gas y Increases respiration rate y Produced in fruits y Eg bananas, apples y Used to market fruit; uniform ripening y Dying flowers y Blocking ethylene production increases the life of cut flowers

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Multiple choice questions

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Multiple choice questionsy Q1. Signal molecules that pass from one cell to another in plants include y A gibberellins that inhibit seed germination yB

ethylene that gives the instruction for fruits to ripen

y C abscisic acid that gives the instruction for leaves to grow y D auxin that gives the instruction for stems to stop growing25

Multiple choice questionsy Q1. Signal molecules that pass from one cell to another in plants include y A gibberellins that inhibit seed germination yB

ethylene that gives the instruction for fruits to ripen

y C abscisic acid that gives the instruction for leaves to grow y D auxin that gives the instruction for stems to stop growing26

Multiple choice questionsy Q2. Hormones can be made of different types of compounds. These include y A - amino acid hormones that are insoluble in water. y B - steroid hormones, insoluble in water, that act only on the outer membrane of a cell. y C - protein hormones that bind to receptors on the cell surfaces. y D - peptide hormones, soluble in water, that act on receptors in the cytosol of a cell.27

Multiple choice questionsy Q2. Hormones can be made of different types of compounds. These include y A - amino acid hormones that are insoluble in water. y B - steroid hormones, insoluble in water, that act only on the outer membrane of a cell. y C - protein hormones that bind to receptors on the cell surfaces. y D - peptide hormones, soluble in water, that act on receptors in the cytosol of a cell.28

Multiple choice questionsy Q3. Testosterone is an example of a steroid hormone.

Testosterone affects only certain cells called target cells. This is because:

y A - testosterone can only cross the plasma membrane of target

cells

y B

only target cells have the necessary receptors in the cytosol to which the testosterone can bind membranes to which the testosterone can attach respond

y C - only target cells have the necessary receptors on their y D - only target cells possess the genes in their DNA that will

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Multiple choice questionsy Q3. Testosterone is an example of a steroid hormone.

Testosterone affects only certain cells called target cells. This is because:

y A - testosterone can only cross the plasma membrane of target

cells

y B

only target cells have the necessary receptors in the cytosol to which the testosterone can bind membranes to which the testosterone can attach respond

y C - only target cells have the necessary receptors on their y D - only target cells possess the genes in their DNA that will

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Multiple choice questionsy Q4. A student set up an experiment as follows: a very ripe apple was placed in a sealed plastic bag with 2 unripe bananas. Another plastic bag was set up as the first, but without an apple. After a few days the bananas with the apple had ripened, but the bananas in the other bag had not. The bananas ripened due to: y A ethylene gas being given off by the ripe apple yB yC yD

methane gas being given off by the ripe apple the increase in temperature due to the decaying apple excess carbon dioxide being given off by the ripe apple31

Multiple choice questionsy Q4. A student set up an experiment as follows: a very ripe apple was placed in a sealed plastic bag with 2 unripe bananas. Another plastic bag was set up as the first, but without an apple. After a few days the bananas with the apple had ripened, but the bananas in the other bag had not. The bananas ripened due to: y A ethylene gas being given off by the ripe apple yB yC yD

methane gas being given off by the ripe apple the increase in temperature due to the decaying apple excess carbon dioxide being given off by the ripe apple32

Multiple choice questionsy Q5. In mammals the parathyroid gland secretes parathyroid

hormone (PTH). PTH regulates the concentration of calcium in blood plasma. PTH increases the amount of calcium in blood plasma by causing calcium to move from bone to the plasma, and by assisting the uptake of calcium from the alimentary canal. PTH also stimulates the kidney to activate vitamin D. Calcium concentration in plasma acts directly, in negative feedback, to regulate the amount of PTH.

It would be expected thaty A y B y C y D

increased PTH production results in reduction of vitamin D activation reduced PTH production results in increased calcium in the faeces sustained overproduction of PTH results in strengthened bones high levels of blood calcium stimulate release of PTH33

Multiple choice questionsy Q5. In mammals the parathyroid gland secretes parathyroid

hormone (PTH). PTH regulates the concentration of calcium in blood plasma. PTH increases the amount of calcium in blood plasma by causing calcium to move from bone to the plasma, and by assisting the uptake of calcium from the alimentary canal. PTH also stimulates the kidney to activate vitamin D. Calcium concentration in plasma acts directly, in negative feedback, to regulate the amount of PTH.

It would be expected thaty A y B y C y D

increased PTH production results in reduction of vitamin D activation reduced PTH production results in increased calcium in the faeces sustained overproduction of PTH results in strengthened bones high levels of blood calcium stimulate release of PTH34

Multiple choice questionsthyroxin that controls basal metabolic rate. Iodine (from the diet) forms part of the thyroxin molecule. The pituitary gland produces a hormone, thyroid stimulating hormone (TSH) that stimulates the production of thyroxin by binding to a receptor on the surface of the thyroid gland. When the level of thyroxin rises above a certain level it inhibits the production of TSH. One can conclude that a person whose diet is deficient in iodine: y A would produce more thyroxin to compensatey B y C y Q6. In humans the thyroid gland produces the hormone

would produce little thyroxin and little TSH

would be expected to have a higher than normal level of TSH in their blood

y D

would produce a form of thyroxin that was less efficient than normal iodine containing thyroxin35

Multiple choice questionsthyroxin that controls basal metabolic rate. Iodine (from the diet) forms part of the thyroxin molecule. The pituitary gland produces a hormone, thyroid stimulating hormone (TSH) that stimulates the production of thyroxin by binding to a receptor on the surface of the thyroid gland. When the level of thyroxin rises above a certain level it inhibits the production of TSH. One can conclude that a person whose diet is deficient in iodine: y A would produce more thyroxin to compensatey B y C y Q6. In humans the thyroid gland produces the hormone

would produce little thyroxin and little TSH

would be expected to have a higher than normal level of TSH in their blood

y D

would produce a form of thyroxin that was less efficient than normal iodine containing thyroxin36

Short answer question 1Thyroxin is a hormone produced by the thyroid gland that increases the metabolic rate of most cells a. What is a hormone? b. What is one possible way of measuring an increasing metabolic rate of cells? Explain your answer.y

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Short answer question 1Thyroxin is a hormone produced by the thyroid gland that increases the metabolic rate of most cells a. A hormone is a chemical produced by an endocrine gland that is released into the bloodstream or other body fluids where it moves to target cells b. Measuring an increase in oxygen uptake; an increase in metabolic rate means an increase in aerobic respiration to produce more energy, and hence an increase in oxygeny

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Short answer question 2A hormone was produced in one cell, entered the bloodstream and travelled to two groups of cells adjacent to each other. One group of cells responded to the hormone but the neighbouring group did not. y What is the most likely reason for this difference in response by cells to the same hormone?y y Cells with the receptors specific for the hormone

respond to this hormone. Only one group of cells had these receptors. The other group had receptors, but not for this hormone39

Short answer question 3y Consider one hormone you have studied this year that

is transported through the blood to one or more types of cells. a. Name the hormone b. Name the tissue or gland that produces the hormone c. Explain what the term signal transduction refers to d. What is the outcome as a result of signal transduction in the cells that were targets for the hormone you chose for part a?40

Short answer question 3Suggested answers a. Hormone b. Tissue or gland (examples) producing hormone Insulin Glucagon ADH Pancreas (beta cells) Pancreas (alpha cells) Hypothalamus d. Signal transduction outcome Liver/skeletal muscles take up more glucose Liver cells release glucose or break down glycogen Cells in kidney tubules reabsorb more water

c. Signal transduction refers to the series of events that occur after the receipt of a specific signal and which result in a response41

Short answer question 4y A general signal transduction pathway is shown in the

following figure. Some of the parts of the pathway are labelled.

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Short answer question 4a. M represents a compound which could initiate signal

transduction. Give an example of compound M b. The initiation of signal transduction in a cell is controlled and specific. Explain what feature ensures this specificity c. What type of molecules generally act as intermediate or relay molecules? d. Name a response in the cell which may occur after signal transduction initiated by the compound M you have named in part a.43

Short answer question 4a. Hormone (could be a specific answer like glucagon) b. The structures of the hormone and the receptor were

complementary; they fit together c. cyclicAMP or more general responses such as different proteins, different enzymes or secondary messenger molecules d. Eg an increase or decrease in protein synthesis or (conversion of glycogen into glucose)

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Short answer question 5The diagram shows a young plant growing with a sufficient supply of nutrients in normal light. a. What type of growth response is being shown by this plant? Some VCE students were asked to perform an experiment to test the effect of lack of sunlight on the growth of a sample of seeds of the same plant. b. Name one controlled variable that students should keep constant. c. Name the one experimental variable that students should change.45

Short answer question 5a. Positive phototropism b. Any of: temperature, number of seeds; nutrients c. Amount of light

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