- Flashcards
4 ways in which organisms can increase the rate of gas exchange
increase surface area, maximise the partial pressure gradient, minimise the amount of diffusion that occurs in an aqueous medium (as diffusion works better in gas form) and have a thin barrier of exchange
does increased temperature increase or decrease the solubility of oxygen in water
decrease
does increased salinity increase or decrease the solubility of oxygen in water
decrease
how does air enter the lungs
through trachea, which splits into bronchi, then even smaller bronchioles, to alveoli
what surrounds alveoli
capillaries
what is the role of surfactant
a phospholipoprotein that lines the inside of alveoli walls, lowering surface tension so that the alveoli don’t collapse
what carries O2 in the blood
haemoglobin
how does the partial pressure of oxygen impact its tendency to bind to haemoglobin `
higher partial pressure makes it more likely to bind
why does CO2 need to be transported out of the body
because it dissolves in liquid to form HCO3- if left to accumulate
how is CO2 transported out of the body
it will either disolve in the plama or in the blood cell, some bicarbonate ions are then able to haemoglobin
what is myoglobin
an oxygen storing molecule in muscle cells, with a higher affinity to oxygen than haemoglobin
role of chemoreceptors
detects oxygen and CO2 partial pressure, and pH, and sends signals to the central nervous system to control the rate of breathing
what determines sex in humans
the presence/absence of the SRY (sex determining region on the Y chromosome)
why is female considered the “default” sex
because if SRY is absent, the person will always be female
what are the 3 main sex hormones
testosterone, progesterone and estrogen
what is the common precursor for the sex hormones
cholesterol
true or false, a woman is born with all the eggs she will ever have in her life time
true
what is the role of the follicular cells surrounding an oocyte
to nourish the oocyte and release estrogen
how many primary oocytes are recruited at the start of the ovarian cycle
6-12
is the primary oocyte haploid or diploid
diploid
what are the 2 specialised cells that make up the follicle (other than the oocyte)
granulosa and theca cells
role of granulosa cells
provide estrogen and prepare the egg for fertilisation
role of theca cells
the primary steroid producing cells - they produce androgens (male hormones) which are then converted to estrogen by the granulosa cells
what does the follicle become following the release of the egg
the corpus luteum
what is the main hormone that the corpus luteum produces
progesterone
what does progesterone do
prevent the ovarian cycle from occuring
what happens to the corpus luteum if pregnancy does not occur
it will degenerate, and the resultant drop in progesterone will trigger menstruation
what is folliculogenisis
the development of the follicle
true or false, the meiosis of a primary oocyte produces 4 ovum
false, it produces 1 mature egg and 3 polar bodies
when does a primary oocyte undergo meiosis 1
at the time of ovulation
when does the secondary oocyte undergo meiosis
at fertilisation
what is the name of the uterus lining
the endometrium
describe the process of the uterine cycle and the hormones involved
estrogen produces by developing follicles stimulates the thickening of the endometrial lining, after ovulation, projesterone produced by the corpus luteum stimulates vascularisation (thickening of blood vessels), a drop in progesterone (if fertilisation does not occur) will result in menstruation (shedding of the lining)
what is the role of vascularisation
to increase blood supply to the uterus and meet the developing embryos nutrient requirements
where in the brain is a major control centre for the regulation of the ovarian cycle
the hypothalamus
explain the HPG axis (hypothalamo-pituitary-gonadal axis)
the hypothalamus releases gonadotrophin releasing hormone (GnRH) in pulses, which act on the anterior pituitary gland, causing it to produce the gonadotrophins FSH (follicle stimulating hormone) and LH (lutenising hormone)
role of LH
stimulates theca cells to produce androgens, which are then converted to estrogen
role of FSH
stimulates folliculogenesis and stimulates granulosa cells to convert androgens to estrogen
explain the feedback acting on the HPG axis
low levels of estrogen exert negative feedback on the HPG axis, supressing the release of LH and FSH. Once. a threshold of estrogen levels is reached (as a result of a buildup from the mature follicle), the axis will switch to a positive feedback loop, causing a surge in the release of LH and FSH (mostly LH), triggering ovulation. once the corpus luteum forms, high estrogen levels, in the presence of progesterone, will exert negative feedback on the axis, therefore inhibiting FSH and LH release.
what the the 2 main phases of the menstrual cycle
the follicular (including menstruation and ovulation) and the luteal phase (following ovulation)
what is endometriosis
a condition of the reproductive system where endometrial cells will grow in parts of the body other than the uterus, and will undergo the normal uterine cycle, including rapid proliferation, vascularisation and the shedding of the lining (as they still have progesterone and estrogen receptors)
the fertilisation of the egg causes the release of which hormone
Human chorionic gonadotrophin (HCG)
what is the role of HCG
to stimulate the corpus luteum to continue producing progesterone and estrogen to maintain the pregnancy
what makes up the testes
seminiferous tubules
what is the rete testes
where the seminiferous tubules come together before being channelled to the epididymis
do the final stages of sperm maturation occur before or after they enter the epididymis
after
what are the 2 specialised cells (other than sperm) found in seminiferous tubules
sertoli and leydig
what is the role of sertoli cells
nurture the developing sperm (the male equivalent of granulosa cells)
what is the role of leydig cells
produce testosterone (equivalent of theca cells)
true or false, males are born with all of the sperm they will have in their life time
false
what cells convert testosterone to estrogen (in males), allowing spermatogensis to occur
sertoli cells
what is dihydrotestosterone
an androgen, more potent than testosterone, that binds to the same receptors, just with a much higher affinity
explain spermatogenesis
diploid male germ cells undergo mitosis to form spermatogonium and then another mitotic division to form the primary spermatocyte. Will then undergo meiosis to become the secondaty spermatocytes after the first division and spermatids after the second. They will then undergo differentiation and maturation to become spermatozoa
what haoppens to the spermatozoa during maturation
they lose the bulk of their cytoplasm and extremely condesne their DNA to enhance mobility `
how does the DNA of sperm become super condensed
histones are replaced with protamines, that compact the DNA so tightly that they render it useless until fertilisation occurs
what is the role of the acrosomal vesicle and where is it located
located in the sperm head, contains the enzymes necessary to dissovle the shell and the mucus covering the egg
why is the mid-piece of the sperm loaded with mitochondria
to provide the sperm with the energy required to swim as fast as possible
how does the HPG axis work in males
GnRH from the hypothalamus also stimulates the anterior pituitary to release FSH and LH. Testosterone exerts negative feedback on the axis, suppressing GnRH secretion and therefore LH release. When testosterone levels drop, GnRH will be released again. Sertoli cells also release inhibin during spermatogensis, which acts directly on the anterior pituitary, inhibitng FSH secretion
role of LH in males
stimulates leydig cells to produce testosterone
role of FSH in males
stimulates spermatogenesis by acting on Sertoli cells
how does the oral contraceptive pill work
contrains progesterone and estrogen, causing the supression of the release of GnRH (as they exert negative feedback on the HPG axis) and therefore prevents the surge of LH that would typically cause ovulation. Also increases cevix mucus thickness, making it harder for sperm to enter, and reduces the thicknesses of the endometrial lining, hampering implantation
what is BPA
an endocrine disrupter that mimic estrogen by binding to estrogen receptors
what is a heterotroph
an organism that gain their energy from other organisms
what are essential nutrients
nutrients such as amino acid that an organism cannot produce themselves
what are the 2 main types of digestion
mechanical and enzymatic/chemical
explain digestion in the mouth
mechanical digestion from the teeth and jaws as well as digestion as the food is mixed with amylase containing saliva, which hydrolyses starch to form smaller saccharides
what transports food from the mouth to the stomach
the oespohagus
describe digestion in the stomach
the stomach is incredibly acidic, which kills pathogens and denatures proteins making them easier to disgest. Utilises enzymes such as pepsin and other proteases.s
what regulates the release of food from the stomach to the small intestine
the pyloric sphincter
what are the 3 parts of the small intestine
duodenum, jejunum and ileum
role of the duodenum
enzymatic digestion occurs here, due to digestive fluids released from the liver and pancreas.
what does the liver produce
bile, which is a mixture of acids, salts, phospholipids and cholesterol that emulsifies lipids, allowing them to be digested
where is bile stored
the gallbladder
what is the hepatopancreatic duct
the small channel shared by the pancreas and the liver that leads to the duodenum
what are micelles
small droplets of emulsified fat (by bile)
what is chyme
the “food” from the stomach
role of the jejunum
absorption of nutrients
role of iluem
absorption of nutrients
how is surface area increased in the small intestine
with a highly folded surface, contianing protusions called villi (which themselves have microvilli)
what enzymes are present in the small intestine
peptidases (which breaks down polypeptides), lactase, sucrase, and maltase (which break down oligosaccharides)
role of the large intestine/colon
absorption of water
role caecum
a microbe containing blind-ended sac that allows for the digestion of fibre (cellulose)
what is a generalist diet
an animal that is able to consume a wide range of foods (such as humans)
what is a specialist diet
an animal with a very restricted diet (and therefore usually a very niche digestive system) such as ant eaters which only eat ants (myrmecophagy)
how do foregut eaters get nutrients
the caecum is located before the stomach, allowing cellulose to be digested. Some microbes wash down the digestive system, providing the animal with additional protein/nutrients
how do hindgut eaters get nutrients
caecum is located after the gut, and therefore these animals will not gain protein from organisms that wash through the system
what releases gastrin
cells lining the stomach when they detect the presence of food
role of gastrin
stimulates the stomach to secrete digestive fluids and increase stomach movement. Also reduces the pH of the stomach when it gets too high
where is secretin produced
the duodenum
role of secretin
stimulates the pancreas to secrete digestive fluid which contains bicarbonate ions to neutralise the acidity of chyme
role of cholecystokinin (CCK)
stimulates the gall bladder to release bile and the pancreas to release digestive enzymes. It is secreted in the presence of fats and lipids in the chyme.
explain the action of ghrelin
when the stomach is empty, ghrelin is released, and detected by the hypothalamus, stimulating appetite and preparing the stomach to receive food
role of leptin
leptin levels increase, and are secreted by adipose tissue (fat cells) and detected by the hypothalamus when fat mass increases, resulting in appetite suppression,
how does low sleep impact ghrelin and leptin levels
inceased ghrelin and decreased leptin
what is produced when microbes ferment fibre
short chain fatty acids
what is osmoregulation
the control of homeostasis of water and solutes
what is an osmoconformer
an organism that has the same osmotic concentrations in their internal environment as the external environment
what is an osmoregulator
an organism that has different osmotic concentrations in their internal environment, to the external environment
what does stenohaline mean
an organism that must live within a narrow salinity range (as they cannot regulate internal salinity levels)
what does euryhaline mean
organisms that can live within a wider range of salinities
high osmolarity means ______ water potential
low
challenge faced by marine animals (in regards to osmoregulation)
body fluid is hypotonic (less concentrated) to sea water and therefore body fluid is lost to the water. This means that the body has too much salt and not enough water.
challenge faced by freshwater animals
body is hypertonic to the water, and therefore water is gained via osmosis and ions are lost to diffusion. Too much water, not enough salt.
