Topic 11: Animal Physiology

Question 1

Outline function of biceps.

Answer 1

Raise lower arm

Question 2

Outline function of cartilage.

Answer 2

Reduces friction, absorbs shock

Question 3

Outline function of distal convoluted tubule.

Answer 3

selective reabsorption of glucose/minerals/amino acids by active transport

Question 4

Explain the role of the medulla and the collecting duct of the kidney in the maintenance of the water balance in blood. [3]

Answer 4

• collecting duct has aquaporins
• high solute concentration of medulla
• reabsorption of water allows excretion of concentrated urine
• secretion of ADH increases permeability of collecting duct to water

Question 5

Outline how the skeletal muscle contracts. [6]

Answer 5

• calcium ions released from sarcoplasmic reticulum
• exposes myosin binding sites on actin
• cross-bridges form between actin and myosin
• ATP provides energy
• for actin filaments to slide over myosin filaments
• ATP provides energy to release myosin from binding sites
• action repeated further along the molecule

Question 6

Explain the role of the kidney in maintaining water balance in humans. [9]

Answer 6

• osmoregulation
• water passed into kidney tubules through ultrafiltration
• water reabsorbed in PCT
• water reabsorbed into blood from descending loop of Henle
• osmosis
• transport of salts into medulla of kidney
• changes salt conc, water is reabsorbed
• ADH releases into blood when water is required
• more reabsorption of water from the collecting duct
• causes concentrated urine
• urine conc. depends on the body’s needs for water

Question 7

Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions. [8]

Answer 7

• osmoregulation
• ultrafiltration in the glomerulus
• basement membrane filters, prevents loss of proteins
• selective reabsorption of glucose in PCT
• water reabsorbed in descending loop of henle
• active transport of sodium ions out of ascending limb
• impermeable to water
• water reabsorbed in collecting duct
• collecting duct permeability depends on ADH
• osmoregulation by varying the amount of water reabsorbed

Question 8

Describe the role of ADH in human osmoregulation.

Answer 8

• secreted when blood plasma concentration is hypertonic/water content too low
• makes walls of collecting duct more permeable to water
• more aquaporins in membrane
• more water reabsorbed from filtrate
• small volume of concentrated urine excreted

Question 9

Explain the role of the nephron in maintaining the water balance of the blood in the human body. [8]

Answer 9

• ultrafiltration in the glomerulus produces large volumes of filtrate
• 80% of water absorbed in PCT
• water reabsorbed from filtrate in descending loop of henle
• pituitary gland secretes ADH if blood solute conc too high
• makes collecting duct more permeable to water
• moves aquaporins into membranes
• more water reabsorbed from filtrate
• small volume of urine with high conc excreted
• water reabsorption in collecting duct due to high solute conc of medulla
• active transport of Na+ ions from filtrate in ascending limb of loop of Henle

Question 10

Outline what is meant by homeostasis. [4]

Answer 10

• Maintaining a constant internal environment
• with narrow limits
• e.g. blood temp/pH
• levels monitored internally
• negative feedback mechanisms
• involves hormonal/nervous control

Question 11

Explain the processes occurring in the kidney that contribute to osmoregulation. [8]

Answer 11

• osmoregulation is the maintenance of water balance
• loop of henle creates hypertonic conditions in the medulla
• water reabsorbed as filtrate passes through collecting duct
• monitored by hypothalamus
• controls secretion of ADH
• ADH released when blood solute conc too high
• makes collecting duct more permeable to water
• due to more aquaporins
• more water reabsorbed
• small volume of concentrated urine produced

Question 12

Blood is a liquid tissue containing glucose, urea, plasma proteins and other components. List the other components of blood. [5]

Answer 12

• plasma
• dissolved gases
• red/white blood cells
• hormones
• lymphocytes/phagocytes
• platelets
• amino acids

Question 13

Explain the role of ATP in muscle contraction. [2]

Answer 13

• ATP binds to myosin heads
• ATP breaks cross-bridges
• energy released when ATP forms ADP and phosphate
• myosin heads reset
• actin slides over myosin

Question 14

Describe how skeletal muscle contracts. [3]

Answer 14

• action potential arrives at neuromuscular junction
• release of calcium ions from the sarcoplasmic reticulum
• calcium binds to troponin, exposes actin to form cross-bridges
• heads push actin filament towards sarcomere center
• use of ATP to break cross-bridges

Question 15

Explain how the kidney helps to retain useful substances in the blood and eliminate substances which the body does not need. [8]

Answer 15

• ultrafiltration in the glomerulus
• basement membrane acts as filter
• prevents large molecules (proteins) from passing
• filtered substances pass to bowman’s capsule
• to PCT
• selective reabsorption
• all glucose reabsorbed
• most water reabsorbed
• area of high solute conc surrounds loop of henle
• ions exchanged between filtrate and blood in DCT
• collecting duct has role in osmoregulation
• ADH regulates amount of water reabsorbed
• substances not reabsorbed are eliminated as urine

Question 16

Describe the production of semen. [5]

Answer 16

• sperm produced by meiosis
• in testis / seminiferous tubules
• sperm stored in the epididymis
• sperm can swim
• seminal vesicles add fluid
• seminal vesicles rich in fructose
• prostate glands add fluid
• fluid rich in proteolytic enzymes (protease)
• semen contains alkaline substances
• neutralizes the acidic environment of the vagina

Question 17

Explain the structure and function of the placenta. [8]

Answer 17

• disc-shaped
• connected to fetus by umbilical cord
• placenta is embryonic and maternal tissue
• placental villi increases SA
• fetal capillaries in placenta
• inter-villous spaces through which mother’s blood flows
• small distance between fetus and maternal blood
• transfer of nutrients/glucose from mother to fetus
• transfer of oxygen from mother to fetus
• transfer of antibodies from mother to fetus
• transfer of waste products/CO2 from fetus to mother
• placenta secretes progesterone and oestrogen

Question 18

Outline the hormonal control of birth. [4]

Answer 18

• at 38-40 weeks of pregnancy fetus produces oestrogen
• decreases progesterone production
• removes inhibition of oxytocin secretion
• oxytocin released by the pituitary gland
• oxytocin stimulates uterine contraction
• cervix dilates and widens
• increase in oxytocin increases the rate of contractions
• positive feedback loop

Question 19

Describe the process of fertilization in humans. [6]

Answer 19

• sperm breaks through follicle cells
• triggers acrosome reaction
• proteases released
• digests zona pellucida
• plasma membranes of egg and sperm fuse
• sperm nucleus enters egg
• cortical reaction
• hardens glycoproteins in zona pellucida
• prevents polyspermy

Question 20

Explain how the structure and function of the placenta help to maintain pregnancy. [8]

Answer 20

• disc-shape organ that attaches to uterus
• connected to the fetus by the umbilical cord;
• produces hormones/HCG that maintain pregnancy;
• estrogen and progesterone maintain uterine lining;
• nutrients/oxygen from mother’s blood transferred to fetal blood;
• antibodies from mother’s blood transferred to fetal blood (through umbilical vein);
• waste products transferred from fetal blood to maternal blood (through umbilical artery);
• embryonic tissue grows into the uterine wall;
• placental/chorionic villi increase the surface area’
• fetal capillaries in placenta
• inter-villous spaces through which mother’s blood flows;
• small distance between fetal and mother’s blood

Question 21

Outline the role of hormones in the menstrual cycle. [6]

Answer 21

• LH and FSH are pituitary hormones
• FSH promotes the development of follicles
• follicles produce oestrogen
• oestrogen repairs and grows uterine wall
• oestrogen causes negative feedback of FSH
• oestrogen stimulates LH production
• LH stimulates the development of the corpus luteum
• corpus luteum secretes progesterone
• progesterone maintains uterine wall
• progesterone inhibits FSH/LH
• lowered level of progesterone (due to degeneration of corpus luteum) leads to menstruation

Question 22

Draw a labelled diagram of a mature sperm cell. [4]

Answer 22

• head and midpiece/mid-section/body;
• tail/flagellum; (at least four times length of the head and containing fibres)
• acrosome; (shown as distinct structure near front of head)
• nucleus; (occupying more than half the width or length of head)
• mitochondria; (as repetitive structures inside membrane of mid piece)
• centriole; (between head and midpiece)
• (plasma) membrane; (shown as single line covering whole cell)

Question 23

Describe the functioning of immunoglobulins. [3]

Answer 23

• function as antibodies
• variety of binding sites
• specific to antigens on pathogens
• attracts phagocytes to engulf the pathogen
• agglutination

Question 24

Outline how antibiotics offer protection from certain forms of infectious disease. [4]

Answer 24

• inhibit the growth of bacteria
• bacteria processes blocked but not in eukaryotes
• block metabolic pathways (e.g. DNA replication/transcription/translation)
• do not protect against viruses (non-living)
• antibiotics fail to protect if bacteria are resistant
• used in animals/humans

Question 25

Outline the role of hormones in the process of birth in humans. [4]

Answer 25

• level of progesterone falls before birth
• oxytocin secreted
• from pituitary
• stimulates uterine contractions
• contractions stimulate more release of oxytocin
• positive feedback loop

Question 26

Outline the processes involved in oogenesis within the human ovary. [8]

Answer 26

• process where female gametes are produced
• begins in fetal development
• large number of cells formed by mitosis
• cells grow, become primary oocytes
• begin first mitotic division, stop in prophase I
• until puberty
• some follicles develop each month in response to FSH
• primary oocyte completes first meiotic division
• forms two cells of unequal sizes (unequal distribution of cytoplasm)
• creates polar body
• polar body degenerates
• secondary oocytes proceeds to meiosis II
• stops at prophase II
• meiosis II completed if cell is fertilized
• ovum and second polar body formed

Question 27

Discuss the ethical issues surrounding IVF. [6]

Answer 27

pros

• chance for infertile couples to have children
• genetic screening of embryos reduces suffering from genetic diseases
• spare embryos safely stored for future pregnancies

cons

• IVF is expensive, not equally accessible
• cultural/religious objections
• lead to gender choice
• lead to unwanted pregnancies with associated risks
• inherited forms of infertility may be passed on to children

Question 28

Discuss the cause, transmission and social implications of AIDS. [8]

Answer 28

causes

• AIDs caused by HIV
• penetrates T lymphocytes
• glycoprotein and cell receptors involved
• reverse transcriptase enables DNA to be produced from viral RNA
• number of lymphocytes reduced over the years
• results in lower immunity
• other illnesses develop

transmission

• HIV transmitted through sexual contact/breastfeeding
• minority of individuals have no cell receptors and do not develop AIDS
• condoms/latex barriers act as protection from transmission through sexual contact

social implications

• expensive treatment
• discrimination
• economic consequences
• traditions/beliefs/culture

Question 29

Coughing to clear the airways is accomplished by muscle contractions. Explain muscle contraction. [8]

Answer 29

• myofibrils in muscle cells
• sarcomeres as the repeating units in myofibrils
• actin and myosin as overlapping protein filaments
• myosin (thick) actin (thin)
• nerve impulses stimulate contraction
• calcium ions released from sarcoplasmic reticulum and bind to troponin
• exposes actin binding sites
• myosin heads form cross-bridges with actin
• ATP breaks cross-bridges, causes movement of myosin heads
• myosin heads change angle
• myosin filaments pull actin towards centre
• sarcomeres shorten during contraction

Question 30

All parts of the body change the composition of the blood. Explain how the nephron changes the composition of blood. [7]

Answer 30

• higher nitrogen/urea when blood enters bowman’s capsule
• small soluble molecules/glucose/nutrients/ions removed from blood
• through ultrafiltration
• large molecules/proteins/blood cells remain in blood
• filtrate passes through nephron, water reabsorbed via osmosis
• selective reabsorption of glucose/nutrients in DCT via active transport
• sodium ions pumped into medulla in loop of Henle
• high sodium gradient enhances water reabsorption
• permeability of collecting duct dependent on ADH

Question 31

Compare the processes of spermatogenesis and oogenesis. [8]

Answer 31

common

• produce haploid cells/mature sex gametes
• involve mitosis and meiosis
• cell growth before meiosis
• differentiation to produce specialized gametes

differences

• where: ovaries; testes
• when: development of embryo; puberty
• breaks: prophase I/prophase II/metaphase I; no breaks
• cytokinesis: split unequally, equal
• number of gametes per meiosis: one cell/egg, some polar bodies; four sperm
• number of gametes released: one per menstrual cycle; millions at a time
• timing of release: at ovulation; during intercourse
• if gametogenesis stops: menstrual pause; goes on until death

Question 32

Describe the consequences of the potential overproduction of offspring. [5]

Answer 32

• more offspring than the environment can support
• increased mortality
• competition for resources
• better adapted more likely to survive
• better adapted pass on advantageous alleles
• natural selection leads to evolution

Question 33

Draw a labelled diagram of a mature human egg. [5]

Answer 33

• haploid nucleus
• cytoplasm
• centrioles
• cortical granules
• plasma membrane
• zona pellucida
• follicle cells
• polar body (outside the egg cell)
• shown as 0.1mm

Question 34

Draw a labelled diagram to show the structure of a sarcomere. [5]

Answer 34

• sarcomere labeled between Z lines
• Z lines at the ends
• actin as thin filaments attached to Z lines
• myosin as thick filaments
• myosin heads on both sides of myosin filaments
• light band (only actin) dark band (actin and myosin)

Question 35

Explain the process of ultrafiltration. [3]

Answer 35

• blood in glomerulus under high pressure due to the difference in diameter of arterioles
• fluid plasma and small molecules forced into bowman’s capsule
• prevents large molecules from passing through

Question 36

Explain the principles of vaccination. [9]

Answer 36

• weakened/attenuated form of a pathogen
• introduced to patient
• pathogen stimulates specific immune response (primary)
• antigens stimulate T-cells
• stimulate cloning of B-cells
• develops memory cells
• that produce specific antibodies
• production of antibodies upon second exposure is much faster
• secondary response
• may need booster shots to maintain immunity
• example of artificial immunity

Question 37

Describe the process of spermatogenesis in humans. [6]

Answer 37

• spermatogonia undergoes mitosis to keep a supply of germinal cells
• spermatogonia grow larger to become primary spermatocytes
• primary spermatocytes go through meiosis I
• forms secondary spermatocytes
• secondary spermatocytes go through meiosis II
• to produce spermatids
• spermatids differentiate (grow tail, reduce cytoplasm)
• associated with Sertoli cells
• sperm detaches from Sertoli cells, enter lumen of seminiferous tubule
• testosterone stimulates sperm production

Question 38

ADH is a peptide hormone produced in the hypothalamus. Explain its action in the human body. [8]

Answer 38

• ADH plays a role in osmoregulation (regulating blood solute concentration)
• acts on the collecting duct
• acts in the DCT
• hypothalamus detects solute concentration
• if blood solution concentration is too high, pituitary releases ADH
• ADH stimulates insertion of aquaporins, increase permeability of collecting duct
• water moves by osmosis, reabsorbed into blood
• small volume of concentrated urine produced
• negative feedback
• if low blood solute concentration, no ADH released
• permeability of collecting duct decreases
• large volume of dilute urine produced

Question 39

Describe the genetic and hormonal control of male sexual characteristics in a human. [3]

Answer 39

• male if (X and) Y chromosomes present
• gene on Y chromosome (SRY) promotes development of testes
• testes secrete testosterone
• testosterone stimulates sperm production/spermatogenesis
• testosterone stimulates development (in fetus) of male genitals/primary sexual
  characteristics
• testosterone stimulates development of male secondary sexual characteristics

Question 40

Explain the production of antibodies in humans. [7]

Answer 40

• antigens stimulate antibody production
• antibodies produced by lymphocytes
• macrophages engulf pathogens, display antigens
• T-cells activated by binding antigen
• activated T-cells activate B-cells
• mitosis of activated B-cells
• plasma cells formed from differentiating B-cells
• plasma cells secrete antibodies
• specific to one antigen
• some activated B-cells become memory cells

Question 41

Explain two types of inheritance, using examples of parents heterozygous for two genes A and B. [7]

Answer 41

• unlinked genes on different chromosomes
• unlinked genes inherited independently
• equal chance for 4 options
• linked genes do not produce Mendelian ratios
• 1:1 chance of inheriting different options
• recombinants are formed
• crossing over in prophase I of meiosis
• causes changes in ratio/genetic variation