11 — animal physiology Flashcards
outline the role of the right atrium in the cardiac cycle (4)
- collects deoxygenated blood from the body
- blood drains into atrium through vena cava
- deoxygenated blood present in vena cava
- right atrium pumps blood into the right ventricle
- at the start of the cardiac cycle
- sinoatrial node is in the right atrium
- SA node sends out electrical signals to stimulate contraction in the walls of the atria
outline the role of ADH in osmoregulation (4)
- ADH secreted by pituitary gland if body is dehydrated
- more aquaporins open in collecting duct
- collecting duct more permeable to water
- water reabsorbed by osmosis
- water passes from filtrate to blood
- less water lost in urine
- negative feedback — less ADH secreted when blood solute concentration returns to normal
describe the hormone feedback mechanisms that help to prepare a woman’s body for pregnancy, sustain the pregnancy and the give birth (7)
preparing the woman’s body for pregnancy
- FSH stimulates oestrogen secretion
- oestrogen increases FSH receptors so boosting oestrogen production
- oestrogen stimulates repair of uterus lining
- high levels of oestrogen stimulate LH production and inhibit FSH secretion
- LH surge stimulates ovulation
sustaining pregnancy
- LH stimulates the development of corpus luteum, which secrets progesterone
- progesterone inhibits FSH and LH secretion
- progesterone maintains lining of uterus
- progesterone inhibits uterine contractions
- HCG secreted by embryo stimulates maintenance of corpus luteum
child birth
- oxytocin stimulates uterine contractions which stimulate oxytocin secretion
- positive feedback
explain how different parts of the kidney balance water and solute concentrations and also excrete nitrogenous wastes (7)
- humans are osmoregulators
- glomerulus/ bowman’s capsule in the nephron carry out ultrafiltration
- proximal convoluted tubule selectively reabsorbs solutes
- loop of henle maintains hypertonic conditions in the medulla by active transport
- loop of henle reabsorbs water by osmosis
- osmoreceptors in the hypothalamus cause production of ADH if the blood is too concentrated
- ADH causes more uptake of water
- resulting in a more concentrated urine
- excess amino acids are broke down producing nitrogenous waste
- ammonia is toxic and converted into non toxic urea
- urea is eliminated in urine
describe adaptations in mammals living in desert ecosystems to maintain osmolarity in their bodies (4)
- behavioural adaptations to avoid overheating
- adaptations for heat exchange e.g. large ears
- may have longer loop of henle
- may produce more ADH
- camel humps that store fat that releases water when broke down
- reduced sweat
describe how monoclonal antibodies are produced (5)
- mice injected with one type of antigen
- antibody producing cells are removed
- plasma cells that produce antibodies are used
- tumour cells that divide endlessly are used
- fusion of plasma cells with tumour produced hybridoma cells
- selection of hybridoma cells
- fused cells are cultured
- hybridoma cells divide endlessly and produce the desired antibodies
explain the role of calcium ions in muscle contraction (3)
- calcium released from sarcoplasmic reticulum
- calcium binds to troponin
- causes tropomyosin to move
- uncovers binding sites
- myosin heads bind to the actin forming cross bridges
explain the mechanism that prevents polyspermy during fertilisation (2)
- cortical reaction after first sperm nucleus enters the egg
- vesicles release their contents form the egg
- outer coat harded
- enzymes of sperm cannot digest the hardened coat
distinguish between osmoregulators and osmoconformers (2)
- concentration constant inside osmoregulators versus variable inside osmoconformers
- internal solute concentration can differ from the external environment in osmoregulators vs same in osmoconformers
- birds mammals freshwater fish are osmoregulators vs salt water aquatic animals are osmoconformers
explain the production and role of antibodies in defence against bacterial pathogens in humans (8)
- specific immune response as a consequence of the present of bacterial antigens
- phagocyte ingests bacterial pathogen displaying bacterial antigens on surface
- attached to MHC molecules
- helper T cell activated by presentation of antigen on surface of macrophage
- activated helper T cell binds to B cell specific to the antigen
- stimulated B cell undergoes repeated cell divisions
- cells enlarge and differentiate to form clone of plasma cells
- plasma cells produce specific antibodies
- antibodies bind to bacteria making them easier to digest by white cells
- some antibodies combined with antigen activate a complement cascade to kill bacteria directly
- some antibodies neutralise toxins
- once begun, antibody production lasts for several days until all antigens destroyed
- memory cells remain in blood giving extended immunity
describe the process of spermatogenesis leading to the production of four sperm cells in a human male (4)
- in the seminiferous tubule
- diploid cells grow
- two divisions of meiosis
- primary spermatocyte carries out the first division and secondary spermatocytes carry out the second division
- meiosis produces haploid cells
- haploid cells differentiate into sperm cells
- sertoli cells help sperm differentiate
outline the roles of oestrogen and progesterone in females during human reproduction (4)
- oestrogen/ progesterone for repair of uterus lining
- oestrogen at high levels stimulates LH secretion
- progesterone maintains the uterus lining during pregnancy
- progesterone/ oestrogen inhibits FSH/ LH secretion
- progesterone for development of breast tissue during pregnancy
- fall in progesterone leads to labour
- oestrogen/ progesterone cause pre-natal development of female reproductive organs
explain the process of muscle contraction (7)
- muscle fibre contains many myofibrils
- made up of sarcomeres
- nerve impulse from motor neuron causes release of calcium ions
- calcium ions released from sarcoplasmic reticulum
- calcium ions link to troponin
- tropomyosin moves to expose actin binding sites
- ATP hydrolysis
- ATP binds to myosin heads and causes them to change angle
- myosin heads form cross bridges to actin
- myosin heads push on actin and then detach from actin
- actin moved towards centre of sarcomere
- sarcomere becomes shorter resulting in muscle contraction
explain how insects excrete nitrogenous wastes (8)
- excreted as uric acid
- excretion by malpighian tubules
- nitrogenous waste in hemolymph
- nitrogenous waste absorbed by malpighian tubules
- ammonia converted to uric acid
- conversion to uric acid requires ATP
- high solute concentration in malpighian tubules
- water absorbed by osmosis flushes uric acid
- water/ ions reabsorbed from the faeces and returned to hemolymph
- uric acid precipitates so can pass out with little water
- uric acid excreted with the faeces
- water conservation
- uric acid is non toxic
compare and contrast the processes of spermatogenesis and oogenesis (8)
compare
- both result in haploid cells
- both involve mitosis at the start
- both have cell growth before meiosis \both involve two divisions of meiosis
- both involve differentiation to produce a gamete
- both are stimulated by hormones
contrast
oogenesis
- in the ovaries
- starts in germinal epithelium during embryo/ fetus development
pauses occur in prophase I/ prophase II/ metaphase II
- large quantity of cytoplasm in egg
- one cell per meiosis
- one usually per month
- released on about day 14
- stops at menopause
spermatogenesis
- in the testes
- continuously starting in germinal epithelium
- no pauses
- small quantity of cytoplasm per sperm
- four sperm per meiosis
- millions daily
- released continuously from testis
- goes on throughout adult life
