Human Health and Physiology

Question 1

Why is the digestion of large food molecules essential?

Answer 1

Firstly, the food we eat is made up of many compounds made by other organisms which are not all suitable for human tissues and therefore these have to be broken down and reassembled so that our bodies can use them. Secondly, the food molecules have to be small enough to be absorbed by the villi in the intestine through diffusion, facilitated diffusion or active transport and so large food molecules need to be broken down into smaller ones for absorption to occur.

Question 2

Describe the role of enzymes in digestion with reference to two named examples.

Answer 2

• Large food molecules must be broken down, such as carbohydrates and proteins through the hydrolysis of bonds to form monomers in preparation for absorption. - rate of reaction at body temperature too slow - enzymes increase the rate of breakdown by acting as a catalyst. - Pepsin breaks down proteins into smaller polypeptides - Salivary amylase breaks down Starch into maltose

Question 3

State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.

Answer 3

Amylase: Salivary Amylase Source: Salivary Glands Substrate: Starch Products: Maltose Optimum pH: 7 Protease: Pepsin Source: Stomach Substrate: Proteins Products: Smaller polypeptides Optimum pH: 1.5-2 Lipase: Pancreatic Lipase Source: Pancreas Substrate: Triglycerides such as fats and oils Products: Fatty Acids and Glycerol Optimum pH: 7

Question 4

Draw and label a diagram showing the structure of the digestive system.

Answer 4

Question 5

What is the function of the stomach?

Answer 5

Stomach: Secretes HCL which kills bacteria. HCL provides optimum pH for pepsin. Secretes pepsin for protein digestion

Question 6

What is the function of the small intestine?

Answer 6

Small intestine: Intestinal wall secretes enzymes Receives enzymes from the pancreas. Has villi for absorption of food particles.

Question 7

What is the function of the large intestine?

Answer 7

Large intestine: Moves material that has not been digested along. Absorbes water. Produces faeces.

Question 8

Define the term absorption.

Answer 8

Absorption is taking up of a substance by the skin, digestive tract, cell membranes, layers of cells and the bloodstream.

Question 9

Define the term assimilation.

Answer 9

Assimilation occurs when the food molecules becomes part of the bodies tissue. Therefore, absorption is followed by assimilation.

Question 10

Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.

Answer 10

• Many villi increase the surface area for absorption. - Epithelium is only one cell layer thick and so food is quickly absorbed. - Microvilli on the villi increase the surface area for absorption further. - Protein channels and pumps are present in the microvilli for rapid absorption. - The mitochondria in the epithelium provide ATP needed for active transport. - Blood capillaries are very close to the epithelium so diffusion distance is small. - The lacteal takes away fats after absorption.

Question 11

Draw a diagram of a villus in vertical section.

Answer 11

Include and label: - lymph vessel - arteriole - venule - central lacteal - capillary network - epithelial layer - microvilli - goblet cells

Question 12

Draw a diagram of the heart showing the chambers, valves and associated blood vessels.

Answer 12

Question 13

What supplies the heart muscles with oxygen and nutrients?

Answer 13

The coronary arteries supply heart muscle with oxygen and nutrients

Question 14

Outline the events that occur within the heart, which cause blood to move around the body.

Answer 14

• blood is collected in the atria - blood is pumped from the atria to the ventricles - opened atrio-ventricular valves allow flow from the atria to the ventricles - closed semi-lunar valves prevent backflow from the arteries to the ventricles -blood is pumped out from the ventricles to the arteries - open semi-lunar valves allow flow from the ventricles to arteries - closed atrio-ventricular valves prevent backflow to the atria - pressure generated by the heart causes blood to move around the body - pacemaker initiates each heartbeat

Question 15

Outline the control of the heartbeat.

Answer 15

• the heart is myogenic (beats of its own accord) - at rest will beat 60-80 times a minute - coordination of the heartbeat is under the control of the pacemaker which is located in the walls of the heart - sends out signals for contraction of heart muscle - atria contract followed by ventricular contraction - nerve for brain can cause heart rate to speed up - nerve from brain can cause heart rate to slow down - adrenalin, carried by blood, speeds up heart rate - `artificial pacemakers can control the heartbeat

Question 16

Explain the relationship between the structure and function of arteries.

Answer 16

• thick wall to help withstands higher pressure - outer fibrous coat prevents artery from rupturing under high pressures - lumen small compared to wall thickness to maintain a higher pressure - lumen larger nearer the heart to conduct a large volume of blood - valves in aorta and pulmonary artery to prevent the backflow of blood into ventricles

Question 17

Explain the relationship between the structure and function of capillaries.

Answer 17

• no muscle outer wall since pressure very low - endothelial layer one cell thick to allow permeability - small diameter leads to exchange - pores allow rapid diffusion - no valves since pressure very low

Question 18

Explain the relationship between the structure and function of veins.

Answer 18

• lumen always large in relation to diameter - thin wall and fewer elastic fibres since pressure lower - very little muscle since not needed for constriction - valves to prevent backflow between pulses

Question 19

What is blood composed of?

Answer 19

plasma erythrocytes leucocytes (phagocytes and lymphocytes) platelets

Question 20

What is transported by the blood?

Answer 20

nutrients oxygen carbon dioxide hormones antibodies urea heat

Question 21

Define pathogen.

Answer 21

an organism or virus that causes a disease.

Question 22

Explain why antibiotics are effective against bacteria but not against viruses.

Answer 22

Antibiotics block specific metabolic pathways Viruses reproduce using the host cell metabolic pathways Host cell pathways are not affected by antibiotics Viruses do not have metabolic pathways

Question 23

Describe how human skin and mucous membranes act as barriers to pathogens.

Answer 23

Skin: - lower pH to keep bacteria from growing - physical barrier to prevent entry - bacteria on skin prevents other bacteria from gowing Mucous membranes - lysozyme in sweat and saliva keeps bacteria growth i check - mucous traps bacteria - mucous is slightly acidic to kill bacteria - cilia sweep mucous up to be swallowed to kill bacteria

Question 24

Outline how phagocytic leucocytes ingest pathogens in the blood and in the body tissues.

Answer 24

Phagocytes are found in the blood and ingest pathogens. They do so by recognising pathogens and engulfing them by endocytosis. Enzymes within the phagocytes called lysosomes then digest the pathogens. Phagocytes can ingest pathogens in the blood but also within body tissue as they can pass through the pores of capillaries and into these tissues. This mechanism of endocytosis is called phagocytosis.

Question 25

State the difference between an antigen and an antibody.

Answer 25

Antigen is a substance that causes antibody formation whereas an antibody is a globular protein that recognises an antigen.

Question 26

Explain antibody production.

Answer 26

Antigen causes an immune response to produce antibodies, specific to that antigen. Antibodies produced in B-lymphocytes, which are produced in the bone marrow. They are carried in the blood. The helper T cell presents the antigen to B cell.

Question 27

Outline the effects of HIV on the immune system.

Answer 27

The Human immunodeficiency virus (HIV) is a retrovirus that infects helper T cells. The activation of lymphocytes requires helper T cells. HIV destroys these helper T cells so the lymphocytes cannot divide to form a clone of antibody producing cells. Antibodies are not produced and the pathogens survives to cause an infection. Infections begin to accumulate in the body - the lungs are especially vulnerable.

Question 28

Explain the cause, transmission and social implications of AIDs.

Answer 28

Cause: AIDs is caused by human immunodeficiency virus (HIV) which is a retrovirus. It enters the T-helper cells causing the immune system to become weakened allowing opportunistic infections to attack. Transmission: - sexually transmitted - mother to fetus - breast milk, saliva and other body fluids - use of dirty, shared, needles - blood transfusions Social Implications - orphaned children - social stigma/discrimination - problems obtaining employment and life insurance - costs on health systems treating people - drug treatment expensive - encourages the use of condoms

Question 29

What is ventilation?

Answer 29

Muscle movement to move fresh air into the alveoli

Question 30

What is gas exchange?

Answer 30

replacing carbon dioxide with oxygen in blood and lungs

Question 31

What is cell respiration?

Answer 31

Cellular energy production from glucose

Question 32

Explain the need for a ventilation system.

Answer 32

• draw fresh air/oxygen into the lungs - removal of CO2 - maintains concentration gradient of O2 and CO2

Question 33

Describe the features of the alveoli that make them well adapted for gaseous exchange.

Answer 33

• large surface area - single cell wall - moist lining - dense network of capillaries - single cell wall to capillary - short distance for gases to travel

Question 34

Describe the structure of the ventilation system, including the alveoli.

Answer 34

• ventilation occurs within the lungs - trachea divides to form two bronchi - bronchi divide to form several bronchioles, which then divide again - alveoli connected to the bronchioles - airways lined with cilla - diaphragm and intercostal muscles help the movement of the rib cage to allow the lungs to expand - many alveoli so there is a large surface area - walls of alveoulus is a single layer of cells - cells in alveolus wall are very thin, allowing diffusion.

Question 35

Explain the mechanism of ventilation of the lungs in humans.

Answer 35

Inhalation: - The external intercostal muscles contract. This moves the ribcage up and out. - The diaphragm contracts. As it does so it moves down and becomes relatively flat. - Both of these muscle contractions result in an increase in the volume of the thorax which in turn results in a drop in pressure inside the thorax. - Pressure eventually drops below atmospheric pressure. - Air then flow into the lungs from outside the body, through the mouth or nose, trachea, bronchi and bronchioles. - Air continues to enter the lungs until the pressure inside the lungs rises to the atmospheric pressure. Exhalation: - The internal intercostal muscles contract. This moves the ribcage down and in. - The abdominal muscles contract. This pushes the diaphragm up, back into a dome shape. - Both of these muscle contractions result in a decrease in the volume of the thorax. - As a result of the decrease in volume, the pressure inside the thorax increases. - Eventually the pressure rises above atmospheric pressure. - Air then flows out of the lungs to outside of the body through the nose or mouth. - Air continues to flow out of the lungs until the pressure in the lungs has fallen back to atmospheric pressure.

Question 36

What does the nervous system consist of?

Answer 36

The Nervous System consists of: The Central Nervous system, consisting of the brain and spinal cord, and the peripheral nerves,, and is composed of sensory and motor neurons that can carry rapid electrical impulses to the CNS.

Question 37

Draw and label a diagram of the structure of a motor neurone.

Answer 37

Include: cell body - complete with nucleus and dendrites axon - shown longer than the longest dendrite, with the membrane drawn as a continuous line myelin sheath - surrounding the axon , showing nodes of Ranvier motor end plates - not covered my myelin sheath and ending in a button/dot

Question 38

How are nerve impulses conducted?

Answer 38

Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.

Question 39

Define resting potential.

Answer 39

the electrical potential across the plasma membrane of a cell that is not conducting an impulse.

Question 40

Define active potential.

Answer 40

the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it (depolarization and repolarization).

Question 41

Explain how a nerve impulse passes along a non-myelinated neuron.

Answer 41

Resting potential rises above threshold level. Voltage gated sodium channels open. Sodium ions flow into the cell, more sodium channels open. Inside of cell develops a net positive charge compared to the outside and results in depolarization. Voltage gated potassium channels open. Potassium ions flow out of the cell. Cell develops a net negative charge compared to the outside and results in repolarization. Concentration gradients restored by sodium-potassium pumps. Resting potential is restored.

Question 42

Explain the principles of synaptic transmission.

Answer 42

• nerve impulse travels to end of presynpatic neuron which triggers the influx of Ca2+. - This causes synaptic vesicles to fuse with membranes which releases neurotransmitter molecules into the synaptic cleft. - the neurotransmitter diffuses across channel and binds to receptors on post synaptic neuron -

Question 43

What does the endocrine system consist of?

Answer 43

Consists of glands that release hormones that are transported by the blood.

Question 44

Define the term homeostasis.

Answer 44

Homeostasis involved maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance.

Question 45

Explain the principle of negative feedback in homeostasis.

Answer 45

• A change in environment is detected - response to bring the system back to within limits - when the normal state is reached, the response is stopped to prevent over reaction - the internal environment fluctuates around the norm.

Question 46

Define the term homeostasis and list four variables under homeostatic control in humans (excluding water balance)

Answer 46

Homeostasis maintains the internal environment at a constant level, between narrow limits. - blood pH - carbon dioxide - blood glucose - body temperature

Question 47

Describe the response of the human body to low external temperatures.

Answer 47

The hypothalamus is responsible for monitoring the temperature of the blood which is normally close to 37 degrees. If there are significant fluctuations from this set point, the hypothalamus sends signals (messages carried by neurons) to different parts of the body to restore the temperature back to the set point. This is done through negative feedback. If the temperature is too low: Vaso-constriction of the arterioles so that less blood flows to the skin. The diameter of the capillaries in the skin cannot change but less blood flows through them. This prevents heat loss to the external environment as the temperature of the skin falls. Shivering occurs. This is when the skeletal muscle does many small rapid contractions to generate heat. Sweat glands to not secrete sweat and so no water evaporation can occur as skin stays dry. Blood flow from extremities is reduced and blood flow to internal organs is increased.

Question 48

Describe the response of the human body to high external temperatures.

Answer 48

The hypothalamus is responsible for monitoring the temperature of the blood which is normally close to 37 degrees. If there are significant fluctuations from this set point, the hypothalamus sends signals (messages carried by neurons) to different parts of the body to restore the temperature back to the set point. This is done through negative feedback. If the temperature is too high: Vasodiliation is skin arterioles so that more blood flows to the skin. By doing so it transfers heat from the core of the body to the skin and this heat is then lost to the external environment, cooling down the body in the process. Skeletal muscle stays relaxed so that more heat is not generated. Sweat glands secrete large amounts of sweat which makes the surface of the skin moist. When water evaporates from the moist skin it cools down the body. Blood flow from extremities is increased and blood flow to internal organs is reduced.

Question 49

Explain how blood glucose concentration is controlled in humans.

Answer 49

• pancreatic cells monitor blood glucose - insulin/glucagon is a hormone - low glucose level induces the production of glucagon from the cells of pancreatic islet - glucagon stimulates the liver to break glycogen into glucose, leading to an increase in blood glucose. - absorption of glucose from the digestive tract after eating causes glucose levels to rise - high level of blood glucose induces the production of insulin - cells of pancreatic islet produces insulin which stimulated uptake of glucose into cells (muscles) and also into the liver, where it is stored as glycogen - insulin leads to decrease in blood glucose homeostatic monitoring of blood glucose levels is constantly happening.

Question 50

What is type 1 diabetes?

Answer 50

The onset is usually early, sometimes during childhood. Beta cells do not produce enough insulin. Diet by itself cannot be used to control the condition. Insulin injections are needed to control glucose levels.

Question 51

What is type 2 diabetes?

Answer 51

The onset is usually late, sometime after childhood. Target cells become insensitive to insulin. Insulin injections are not usually needed. Low carbohydrate diet can control the condition.

Question 52

Draw a labelled diagram pf am adult male reproductive system.

Answer 52

Include: - penis - scrotum - prostate gland - sperm duct - urethra - seminal vesicle - bladder - testes - epididymis - sperm duct / Vas deferens - Cowper’s gland - seminiferous tubules - erectile tissue

Question 53

Draw a labelled diagram of the reproductive system of a human female.

Answer 53

Include: - oviduct/fallopian tube - uterus -cervix - vagina - vulva/ labia - clitoris - endometrium

Question 54

Explain how hormones control the menstrual cycle in human females

Answer 54

Follicle Stimulating Hormone (FSH) stimulates the development of follicles and stimulates oestrogen secretion (by the developing follicle). Oestrogen stimulates the repair of the uterus lining and stimulates Lutenizing hormone secretion. LH causes ovulation and the development of the corpus luteum and the secretion of progesterone. Progesterone causes the thickening of the uterus lining ready for implantation. Progesterone and Oestrogen inhibits the secretion of LH/FSH Falling progesterone levles at the end of the cycle allowe FSH production and the cycle begins again.

Question 55

List three roles of testosterone in males.

Answer 55

pre-natal development of male genitalia development of male secondary sexual characteristics maintenance of sex drive

Question 56

Outline the process of in vitro fertilization.

Answer 56

IVF is fertilization outside the body. Drugs stop the normal menstrual cycle. FSH is injected to stimulate ovaries into producing eggs. HCG, a hormone, matures the follicle. Eggs are removed from the ovaries. A male donor provides sperm and the eggs are mixed with the sperm. 2-3 embryos are implanted into the uterus and a pregnancy test is done later to see if pregnancy has occured.

Question 57

What are the arguments for IVF?

Answer 57

Many types of infertility are due to environmental factors rather than genetic which means that the offspring would not inherit the infertility. The embryos that are killed during the IVF process cannot feel pain or suffering as they do not have a developed nervous system. Suffering caused by genetic diseases can be decreases by screening the embryos before placing them into the uterus. Since the IVF process is not an easy one emotionally and physically, is costly, takes time and there are no guarantees, parents who are willing to go through it must have a strong desire to have children and therefore are likely to be loving parents. Infertility can cause emotional suffering to couples who want to have children. IVF can take away this suffering for some of those couples.

Question 58

What are the arguments against IVF?

Answer 58

The infertility of the parents may be inherited by their offspring passing on the suffering to the next generation. More embryos are produced than needed and the ones that remain are usually killed which denies them the chance of a life. Embryologists select which embryos will be placed into the uterus. Therefore they decide the fate of new individuals as they choose which ones will survive and which ones will die. IVF is not a natural process which takes place in a laboratory compared to natural conception which occurs as a result of an act of love. Infertility should be accepted as God’s will and to go against it by using IVF procedures would be wrong.

Question 59

Describe how an action potential is produced.

Answer 59

The neuron begins at resting potential of -70mV which is established through the Sodium and Potassium pump. Na+ ions are pumped out and K+ ions are pumped in. Depolarisation occurs when a neuron is stimulated and a nerve impulse is generated. This happens as the voltage-gated protein channels open. Na+ ions flow into the cell and follow the electrical gradient and the concentration gradient. Inside becomes positively charged only if the neuron passed the threshold level of -50mV meaning the action potential is generated. The resting potential is restored through repolarisation. Gated K+ channels open and K+ flows out. Drops to below resting potential during refractory period in which Na+ channels are inactivated and the neuron cannot respond. The Na+ and K+ pumps re establish resting potential. Action potential in one axon causes he depolarisation of the adjacent section of the axon.

Question 60

Outline the use of four methods of membrane transport in nerves and synapses.

Answer 60

Active Transport - sodium-potassium pump rests resting potential in the axon following nerve impulse - re uptake of neurotransmitters to the pre-synaptic neuron following synaptic transmission - removal of Ca2+ from presynaptic neuron following synaptic transmission Simple diffusion - diffusion of neurotransmitter across synaptic cleft - diffusion of K+ ions out of the axon in resting potential Facilitated Diffusion - opening of the voltage-gated Na2+ and K+ channels in action potential -opening of voltage gated Ca2+ at presynaptic terminal. - Na+ channels activated in the post-synaptic terminal to propagate AP Vesicle Transport - influx of Ca2+ activates vesicles of neurotransmitters - exocytosis of neurotransmitter from ore-synaptic neuron to synaptic cleft