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6.4 Gas exchange

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Page 1: Topic 6 4, 6 5, 6 6

6.4 Gas exchange

Page 2: Topic 6 4, 6 5, 6 6

All organisms absorb one gas from the environment and release another gas. This is called gas exchange and is accomplished in different ways, including:◦ Gills◦ Lungs◦ Diffusion through body surfaces◦ Through pores in leaves

Page 3: Topic 6 4, 6 5, 6 6

Biology Course Companion describes ventilation as the process of pumping fresh air or water to the gas exchange surface to replace the air.

We can also describe ventilation as the inhalation and exhalation of gases into the alveoli of the lungs. This is sometimes called respiration, but it should not be confused with…

Cell respiration refers to the process of using oxygen to release energy from glucose molecules. (Topic 3.7)

Page 4: Topic 6 4, 6 5, 6 6

Gas exchange happens by diffusion at a surface where the organism is in contact with the environment.

The rate of gas exchange depends on the area of the surface and on the concentration of gases across the exchange surface.

Pumping fresh air or water across the exchange surface, to replace the air or water already there, helps to maintain the concentration gradient so that diffusion will occur.

Page 5: Topic 6 4, 6 5, 6 6

The syllabus states that this answer should include:◦ A large total surface area◦ A wall consisting of single layer of flattened cells◦ A film of moisture◦ A dense network of capillaries

You should know why each of these is important. Think about the fact the gas exchange occurs by diffusion (6.4.2).

Having a good understanding of the structure of alveoli will help you understand this, so the next assessment statement will help.

Page 6: Topic 6 4, 6 5, 6 6
Page 7: Topic 6 4, 6 5, 6 6

Teacher’s notes in syllabus advises that you should be able to draw the inset diagram of the alveoli.

Page 8: Topic 6 4, 6 5, 6 6

Check outMader page 675 and .Click4Biology. Intercostal musclesrun between the ribs and help form andmove the chestwall. Be sure to be ableto explain volumeand pressurechanges.

Page 9: Topic 6 4, 6 5, 6 6

Inhalation—rib cages expands and diaphragm moves down.

This increases the volume of the chest cavity and therefore lowers the air pressure inside the lungs.

Air moves in due to pressure gradient.

Page 10: Topic 6 4, 6 5, 6 6

Exhalation—rib cages gets smaller and diaphragm relaxes.

This decreases the volume of the chest cavity and therefore raises the air pressure inside the lungs.

Air moves out due to pressure gradient.

Page 11: Topic 6 4, 6 5, 6 6

Inhalation—rib cages expands and diaphragm moves down.

This increases the volume of the chest cavity and therefore lowers the air pressure inside the lungs.

Air moves in due to pressure gradient.

Page 12: Topic 6 4, 6 5, 6 6

6.5 Nerves, hormones and homeostasis

Page 13: Topic 6 4, 6 5, 6 6

Central nervous system:◦ Brain◦ Spinal cord (please note the spelling)

Peripheral nerves◦ Sensory neurons◦ Motor neurons

Page 14: Topic 6 4, 6 5, 6 6

Syllabus states to include these:◦ Dendrites◦ Cell body with nucleus◦ Axon◦ Myelin sheath◦ Nodes of Ranvier◦ Motor end plates

Page 15: Topic 6 4, 6 5, 6 6

Dendrites provide large surface area for connecting to other neurons. They carry impulse toward the cell body.

Axon carries impulse away from the cell body.

Schwann cells form the thick insulating lipid layer called the myelin sheath.

Page 16: Topic 6 4, 6 5, 6 6

Worksheet 309 - 3124 dendrite sends signal to the cell body cell body is the control center axon takes impulse away from cell body5 a. sensory receptor b. cell body c. axon d. dendrite e. cell body f. axon g. dendrite h. axon i. myelin sheath j. node of Ranvier k. effector6 sensory neuron carries impulse to CNS interneuron takes nerve impulse from one part of CNS to

another motor neuron takes nerve impulse away from CNS

Page 17: Topic 6 4, 6 5, 6 6

9 a. an instrument that measures potential differences in millivolts b. large organic ions are inside the membrane (and K+ ions leak to outside) c. more Na+ ions outside

d. less K+ ions outside e. sodium-potassium pumps10 a. depolarization b. repolarization c. action potential d. threshold e. resting potential

Page 18: Topic 6 4, 6 5, 6 6

11 a. a change from negative potential to positive potential inside the axon

b. change from positive potential inside the axon back to negative

c. refers to the reversal of potential that occurs during the action potential

d. movement of Na+ to inside causes the inside to become more positive

e. gate of Na+ channel opens f. movement of K+ to outside causes the inside to become

negative again g. gate of K+ channel opens

Page 19: Topic 6 4, 6 5, 6 6

12 a. axon bulbs b. synaptic vesicles c. dendrites d. neurotransmitter e. synaptic cleft13 a. neurotransmitter is received by receptor of next neuron b. summing up of the effects of various neurotransmitters

—some are stimulatory and some are inhibitory

Syllabus notes advise that this answer would include◦ Release, diffusion and binding of neurotransmitter◦ Initiation of an action potential in the post-synaptic

membrane◦ Removal of neurotransmitter

Page 20: Topic 6 4, 6 5, 6 6

Endocrine glands are organs which produce chemicals called hormones and release the chemicals into the blood stream for transport throughout the body.

In contrast, exocrine glands also produce chemical products, often enzymes. The chemicals are released through tubes called ducts directly to the location in which the chemicals are to be used.

Therefore endocrine glands are sometimes called ductless glands.

Page 21: Topic 6 4, 6 5, 6 6

This is a definition of the term homeostasis. The term is used to describe maintaining the conditions within a cell or within an organism.

Both the nervous system and the endocrine system play a role in homeostasis by monitoring levels of variables and correcting changes in levels by negative feedback mechanisms.

Page 22: Topic 6 4, 6 5, 6 6

Negative feedback is also known as end-product inhibition and it involves the product of a process inhibiting the process that created the product.

In answering this question, you could use specific examples of hormonal feedback mechanisms.

Page 23: Topic 6 4, 6 5, 6 6

Click4Biology shows an alternate diagram to show how feedback mechanisms react to increases or decreases from the set point.Use the image that works best for you.Use specific examples of hormonal feedback.

Page 24: Topic 6 4, 6 5, 6 6

Cells in the hypothalamus detect changes in core body temperature and bring about different responses depending on whether the core body temperature is above or below the set point.

Page 25: Topic 6 4, 6 5, 6 6

Body temperature rises Arterioles in skin

vasodilate which increases blood flow to skin and allows for heat transfer.

Sweating dissipates heat through evaporation.

Hair flattens decreasing insulation.

Body temperature falls Arterioles in skin

vasoconstrict, reducing blood flow to prevent heat loss.

Sweating inhibited. Hair raised increasing

insulation. Shivering increases

muscular activity which generates heat.

Page 26: Topic 6 4, 6 5, 6 6

High blood glucose Beta cells detect increase

in blood sugar and secrete insulin into the blood.

Uptake of glucose by cells is increased, especially:◦ Liver cells—store

glycogen◦ Muscle—store glycogen;

build protein◦ Adipose tissue—stores

fat Return to set point reduces

insulin production.

Low blood glucose Alpha cells detect

decrease and secrete glucagon into the blood.

Liver breaks down glycogen and converts amino acids and glycerol to glucose.

Return to set point reduces glucagon production.

Page 27: Topic 6 4, 6 5, 6 6

In diabetes, body cells do not take up/metabolize glucose.

As blood glucose levels rise, glucose is excreted in the urine.

The body using proteins and fats for energy. Metabolism of fats increases ketones in the blood and causes acidosis. This can lead to coma and death.

Diabetics are prone to blindness, kidney disease, circulatory problems and complications during pregnancy.

Page 28: Topic 6 4, 6 5, 6 6

Type I diabetes is also called insulin-dependent diabetes. It is an auto-immune disease in which T-cells destroy the

pancreas beta cells that normally secrete insulin. Individuals must have daily insulin injections.

Type II diabetes is also called noninsulin-dependent diabetes.

The pancreas produces insulin, but the liver and muscle cells do not respond in the usual manner. They may lack the receptor proteins that bind to insulin.

Type II diabetes can sometimes be managed with diet and exercise or with oral drugs that stimulate the pancreas and enhance metabolism.

Page 29: Topic 6 4, 6 5, 6 6

6.6 Reproduction

Page 30: Topic 6 4, 6 5, 6 6

Mader and Click4Biology both have good diagrams to use as examples.

The diagrams on Click4Biology are more simple and perhaps easier to use. The diagrams in Biology Course Companion are also simple.

Teacher’s notes advise that relative position is important and that the diagram must include the bladder and urethra.

Page 31: Topic 6 4, 6 5, 6 6

Follicle stimulating hormone—produced by anterior pituitary ◦ Development of oocyte in the follicle◦ Thickening of follicle wall◦ Secretion of follicular fluid◦ Secretion of estrogen by follicle wall

Luteinizing hormone—produced by anterior pituitary◦ Completion of meiosis in the oocyte◦ Partial digestion of the follicle wall allowing it to burst

open (ovulation)◦ Growth of the corpus luteum which secretes estrogen and

progesterone

Page 32: Topic 6 4, 6 5, 6 6

Estrogen—produced by the ovary◦ Thickening of the endometrium◦ Blood vessel growth in endometrium◦ Increase in FSH receptors in follicle◦ Inhibition of FSH secretion and stimulation of LH secretion

when estrogen levels are high Progesterone—produced by the ovary

◦ Maintenance of thickening of the endometrium with many blood vessels

◦ Inhibition of FSH and LH secretions

Page 33: Topic 6 4, 6 5, 6 6

We completed a lab activity that creates the graph of these relationships.

The graph helps to comprehend the changes described in assessment statement 6.6.2.

You have a handout of this graph for your notes binder. This was handed out after the lab was finished.

Page 34: Topic 6 4, 6 5, 6 6

Normal development and functioning of the male reproductive organs

Maturation of sperm Initiates and maintains the male secondary sex

characteristics that develop during puberty◦ Increase in height and muscle mass◦ Deeper voice due to longer vocal cords◦ Facial and body hair

Page 35: Topic 6 4, 6 5, 6 6
Page 36: Topic 6 4, 6 5, 6 6

Hormones injected to induce menstruation. Ultrasound used to check for follicles. Synthetic FSH administered to develop follicles. Synthetic LH induces follicles to be ready for release. Eggs are collected. Sperm is collected. Fertilization of eggs by sperm (in Petri dish). Embryos checked and selected for implantation. Embryos transferred to uterus.

Diagram from Click4Biology

Page 37: Topic 6 4, 6 5, 6 6

Allows infertile individuals to achieve pregnancy. Costly. What happens to unused embryos. Embryo selection possibilities. Health risk to mother if multiple embryos implanted. Health risk to children if multiple embryos implanted. Should infertility be by-passed.

Page 38: Topic 6 4, 6 5, 6 6

Alcott, Andrew, and David Mindorff. Biology Course Companion. Oxford: Oxford University Press, 2007.

Burrell, John. Click4Biology. 23 Aug. 2007. 13 Oct. 2007 <http://www.patana.ac.th/secondary/science/index.home.htm>

Campbell, Neil, et al. Biology: Concepts and Connections. 5th ed. San Francisco: Pearson Benjamin Cummings, 2006.

Mader, Sylvia S. Biology. eighth ed. Boston: McGraw Hill, 2004.

Miller, Kenneth R., and Joseph Levine. Biology. Boston: Pearson Prentice Hall, 2006.