B3 - organism level systems Flashcards
what is accommodation?
changing the lens shape to fine focus the image of an object regardless of its distance from the eye
what is the central nervous system?
CNS, the brain and the spinal cord
what is the cerebellum?
the region of the brain that controls unconscious functions such as posture, balance and muscular movement
what is the cerebral cortex?
the outer layer of the cerebrum
what is the cerebrum?
the highly folded region of the brain that is responsible for controlling voluntary actions such as learning, personality and memory; it is divided into the right and left hemispheres
what is the ciliary body?
an extension of the iris, it contains the ciliary muscle which can contract or relax allowing the eye to focus
what is colour blindness?
a condition where a person has a defect in the receptors or a lack of receptors in the retina
what is coordination?
the ability to use different parts of the body together smoothly and efficiently
what is the cornea?
the part of the eye that refracts light as it enters, focusing it onto the retina
what is the effector?
a gland or muscle that produces a response to the stimulus to restore optimum conditions
what is the iris?
the part of the eye that contracts or relaxes to control the amount of light entering the eye
what is the lens?
a part of the eye that further refracts light to focus it onto the retina
what is long-sightedness?
hyperopia; a defect of the eye where distant objects appear out of focus due to the convergence of light rays in front of the retina
what is the medulla?
the part of the brain responsible for non-voluntary movement such as breathing rate and heart rate
what is the motor neurone?
the neurone that transmits impulses from the relay neurone to the effector to produce a response
what is the optic nerve?
the nerve that carries impulses between the brain and the eye
what is the pituitary gland?
the gland that stores and releases hormones which regulate many bodily functions
what is the pupil?
a hole in the centre of the iris, it is controlled by the muscles of the iris and changes size depending on the brightness of the light
what is the receptor?
a cell or organ that recognises the stimulus
what is the reflex arc?
the pathway of neurones involved in a reflex action
what is the relay neurone?
the neurone that transmits electrical impulses from the sensory neurone to the motor neurone
what is the retina?
the layer at the back of the eye that contains light receptors and is sensitive to light
what is the sensory neurone?
the neurone that detects the stimulus. and transmits the electrical impulse to the rely neurone located in the spinal cord
what is short-sightedness?
myopia; a defect of the eye where distant objects appear out of focus due to the convergence of light rays in front of the retina
what are suspensory ligaments?
attach the lens to the ciliary muscle
what is the synapse?
the junction between two neurones (nerve cells)
what are the two divisions of the nervous system?
- central nervous system
- peripheral nervous system
what does the nervous system enable humans to do?
- react to their surroundings
- coordinate their behaviour
what are some examples of using the nervous system?
- avoiding danger
- finding a mate
- finding food
what are neurones (nerve cells)?
specialised to rapidly carry nerve impulses (electrical) from one part of the body to another
what is the function of a cell body?
contains nucleus, which controls the cell, also produces neurotransmitters
what is the function of an axon terminal?
to transmit neurotransmitters (we meet these soon) from the presynaptic neurone into the synapse
what is the function of the myelin sheath?
insulates neurone, speeding up impulse
what is the function of the nodes of Ranvier?
the “gaps” between the Schwann cells; allow speed of transmission to be further increased by allowing impulse to “jump” from node to node in a process called saltatory conduction
what is the function of dendrites?
branched endings - connect with other neurones and carry nerve impulses towards cell body
what is the function of Schwann cells?
forms the myelin sheath
what is the function of an axon?
single long fibre that carries nerve impulses away from cell body towards nerve endings
how do reflexes work?
- receptors detect changes in the environment (e.g. retina cells detect changes in light or skin cells detect changes in temperature/pressure)
- when a stimulus (change) is detected by receptors, the information is sent as electrical impulses along sensory neurones to the CNS
- the CNS coordinates a response (“decides” what to do about the change)
- the CNS then sends electrical impulses to an effector organ (muscle or gland) along a motor neurone
- the effector then responds accordingly, this could be causing a muscle to contract or a gland may secrete (release) a hormone
why is a reflex reaction quicker than the coordinated responses?
- automatic so are quicker than normal responses
- conscious brain isn’t involved
- sensory neurone connects to a relay neurone which links directly to the correct motor neurone (no time wasted thinking about the right response)
- these reactions often have a projective role
*reflex reactions do not require cognitive thought
what is the order from stimulus to response?
stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
what happens to the pupil when it’s dark?
when it’s dark, the pupils will dilate to let in as much light as possible
(pupil is dilated)
what happens to the pupil when it’s light?
when it’s very bright, the pupils constrict so that less light is let into the eye
(pupil has constricted/not dilated)
how does the lens change shape to look at distant objects?
- ciliary muscle is relaxed so it’s long and thin
- suspensory ligaments are pulled outwards
- they pull the lens flatter
how does the lens change shape to look at near objects?
- ciliary muscle contracted so short and fat
- suspensory ligaments slacken off
- lens becomes more convex (rounded)
what type of lens is used to correct short-sightedness?
concave
- this makes the light refract more before it enters the eye
what type of lens is used to correct long-sightedness?
convex
what is the alternative to corrective lenses?
laser eye surgery
what are the pros to laser eye surgery?
- it is a quick, simple procedure; it is outpatient so there are no overnight hospital stays, you do not go under general anaesthesia and the whole thing takes only 20 minutes on average
- vision improvement begins quickly, within a few hours after surgery; most people report noticing a huge difference the next day
what are the cons to laser eye surgery?
- you may physically not be eligible; for example, if you are younger than 20 or older than 40, your risk of changes to your cornea is higher, so LASIK is a much more temporary vision fix as your eyes change
- some side effects may be permanent, and they can be uncomfortable
what is the function of rods?
respond to light and allow you to see in low light levels, they are not responsive to different colours
what is the function of cones?
respond to different colours, different cells respond to red, blue and green light
what is the most common type of colour blindness?
red-green (protanopia)
why can investigating brain function be problematic?
- patients must give consent
- many studies need to be analysed to draw any reliable conclusions
- several areas of the brain may be involved in a specific function
- many people believe animal testing is unethical
how can the brain be investigated?
- CT scans
- MRI scans
- fMRI scans
- case studies
- post mortems
how can the brain be investigated using CT scans?
- use x-rays to create images
- quicker, quieter and cheaper than MRI
- don’t show up soft tissues as well
- cannot be used regularly (exposure to radiation)
how can the brain be investigated using MRI scans?
- use powerful magnets to identify abnormalities
- very expensive
how can the brain be investigated using fMRI scans?
- like an MRI but in real time
- increased blood flow shows up while the patient carries out specific activities
- allows doctors to work out which parts of the brain are responsible for different functions
- non-invasive and easy to use
- it cannot be known that the same pattern of activity would occur when not in machine
- very expensive
how can the brain be investigated using case studies?
- detailed, in-depth investigations of one individual or a small group; in this particular case it would be someone or a group with abnormal brain function
- if part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does
how can the brain be investigated using post mortems?
- involves the analysis of a person’s brain following their death
- areas of damage are examined to find out what caused the death
- this may also involve comparison with a neurological (normal) brain to look at the extent of the differences
what can damage to the nervous system be caused by?
- injury
- disease
- genetic condition
- ingesting toxic substances
how does the damage affect the nervous system?
damage prevents impulses from being passed effectively through the nervous system
what can damage to the PNS affect?
both motor and sensory neurones
what are the impacts of damage to the PNS?
- inability to detect pain
- numbness
- loss of coordination
what treatments are there for damage to the PNS?
- minor: self-heals with rest and support
- more severe: surgery
e.g. sections of nervous tissue can be grafted over damaged tissue, restoring the electrical conduction path for an impulse
what can damage to the CNS lead to?
- loss of control of body systems
- partial or complete paralysis
- memory loss or processing difficulties
can the CNS regenerate?
no, damage is permanent unless it can be corrected by surgery
what treatments are there for damage to the CNS?
- craniotomy
- radiotherapy and chemotherapy
- deep brain stimulation
how do craniotomies work?
- surgery to remove damaged brain tissue
- to access the brain, a surgeon peels back the scalp and removes a section of skull
what do radiotherapy and chemotherapy work?
- to treat a brain tumour
- MRI images may be used to build up an image of the damage site
-radiotherapy: beams of gamma radiation are fired at the tumour - chemotherapy: drugs that target fast-growing or fast-dividing cells, the drugs travel in the bloodstream
how does deep brain stimulation work?
- inserting an electrode to stimulate brain function
why is it so difficult to repair the CNS?
- 31 pairs of nerves
- each nerve consists of many nerve fibres (neurones)
- spinal cord is around 1.5 cm in diameter
- identifying and repairing damage to an individual nerve fibre, without damaging others, is extremely difficult
what is adrenaline?
a hormone released by the adrenal gland which increases heart rate and breathing rate (involved in fight/flight); it also raises blood sugar levels by increasing the conversion of glycogen into glucose
what is auxin?
a plant hormone responsible for cell elongation
what is contraception?
methods that are used to prevent pregnancy
what is dormancy?
a period of time in which seeds ‘hibernate’; this stops then they germinate
what are the endocrine glands?
a group of cells that are specialised in secreting chemicals (hormones) directly into the bloodstream
what is the endocrine system?
a chemical messenger system that releases hormones directly inti the bloodstream to control metabolism, development, growth and reproduction
what is ethene?
a plant hormone that promotes fruit ripening
what is FSH?
follicle stimulating hormone; a female reproductive hormone that is released by the pituitary gland and is responsible for the maturation of an egg in the ovary
what is gravitropism?
the growth response of a plant to gravity
what is germination?
the process by which seeds develop into plants
what is gibberellins?
plant hormones that initiate germination and flowering
what is herbicide?
a type of pesticide used to kill unwanted plants (weeds)
what is a hormone?
a chemical messenger secreted by the endocrine glands into the bloodstream and transported to receptors or target organs
what is infertility?
the inability to reproduce after 12 months or more of unprotective sex
what is a menstrual cycle?
the monthly cycle in biological women that involves the development of the uterus lining, ovulation, maintenance of the uterus lining and its shedding
what is IVF?
in vitro fertilisation; the fertilisation of an egg using sperm outside of the body
what is LH?
luteinising hormone; a female reproductive hormone released by the pituitary gland that stimulates the release of an egg
what is negative feedback?
a system that works to reverse the initial stimulus
what is a parthenocarpic fruit?
seedless fruit
what is oestrogen?
a female sex hormone produced in the ovaries that regulates the menstrual cycle and controls the development of secondary sexual characteristics
what is a pituitary gland?
the gland that stores and releases hormones which regulate many bodily functions
what is phototropism?
the growth response of a plant to unilateral light
what is progesterone?
the hormone that maintains the uterus lining during the later stages of the menstrual cycle and pregnancy
what are root cuttings?
a method of cloning plants in which a root is cut from a parent plant and replanted in compost
what is rooting powder?
a powder that contains auxins, the cut root is dipped into this before being replants (during root cuttings)
what is thyroxine?
a hormone released by the thyroid gland that controls the metabolic rate and the rate of glucose uptake during respiration; it also promotes growth
what is testosterone?
the male reproductive hormone that controls sperm production and the development of secondary sexual characteristics
what are some parts of the endocrine system?
- pituitary
- thymus
- pancreas
- ovaries
- testes
- adrenal
- parathyroid
- thyroid
what are hormones made from?
proteins
where are hormones produced?
they’re produced by endocrine glands which make up your endocrine system
how are hormones transported around the body?
they’re released directly into the bloodstream to be transported around the body
where do hormones have their effect?
they will only affect “target cells/organs”
- they have the correct “receptors” to respond to that hormone
what are the differences between the nervous system and the endocrine system?
nervous:
- transmission via electric impulses
- route of transmission = neurones
- fast
- short acting
endocrine:
- transmission via hormones
- route = bloodstream
- slow
- long acting
what is the body adapted to in a threatening situation?
- fight or flight
- some well camouflaged organisms might freeze
what is the effect of adrenaline on the body?
- adrenaline binds to receptors in the heart which then contracts more frequently and with more force
- heart rate and blood pressure increase
- also binds to receptors in liver which breaks down glycogen stores to release glucose
- this causes blood glucose levels to increase so more glucose can be transported to cells for increased respiration
what dos the body do when the level of a substance is detected as above or below normal level?
it triggers a response to bring the level back to normal
what is thyroxine released by?
the thyroid gland
what does thyroxine do?
- increase metabolic rate
- increase respiration rate
- increase formation of proteins, lipids and glycogen
what does the thyroid gland do to make thyroxine?
takes iodine an converts into thyroxine by combining with the amino acid tyrosine
what happens to the thyroid gland when it attempts to increase production of thyroxine?
it enlarges
(hypothyroidism)
what triggers the release of thyroxine?
thyroid stimulating hormone (TSH from the pituitary gland) triggers its release (this is where negative feedback occurs)
what happens when thyroxine is too high?
secretion of TSH from pituitary gland is inhibited
what are structures found in the female reproductive system?
- oviduct
- ovary
- uterus
- cervix
- vagina
what are the female reproductive hormones?
- oestrogen
- progesterone
- FSH (follicle stimulating hormone)
- LH (leutinising hormone)
what does oestrogen do?
- thickens uterine lining (endometrium)
- inhibits FSH and LH for most of the cycle
- stimulates FSH and LH release pre-ovulation
what does progesterone do?
- thickens uterine lining (endometrium)
- inhibits FSH and LH
what does FSH do?
- stimulates follicular growth in the ovaries
- stimulates oestrogen secretion (from developing follicles)
what does LH do?
- surge causes ovulation
- results in the formation of corpus luteum (yellow body)
what is menstruation?
the periodic discharge of blood and mucosal tissue (the endometrium) from the uterus and vagina
what is ovulation?
the phase of a menstrual cycle in which a mature ovum is released from the ovarian follicles into the oviduct
what causes menstruation?
if fertilisation doesn’t occur, the egg and lining of the uterus break down and leave the body through vagina
(old lining is shed/removed via bleeding)
at what point in the cycle does menstruation occur?
day 1-7
at what point in the cycle does ovulation occur?
around day 14
what occurs between day 1-13?
egge developing inside the growing follicle
what occurs between day 15-28?
empty follicle turns into corpus luteum
how many eggs are females born with?
1-2 million potential eggs
by puberty, how many eggs would a woman have?
maybe 1 million
by 25, how many eggs would a woman have?
around 300,000
what happens at age 35?
decline gets steeper, meaning a female can lose an even higher number of eggs per month until menopause
which hormone is released from the pituitary gland which stimulates the development of a follicle in the ovary?
FSH
as an egg matures inside the follicle, which hormone is produced?
oestrogen
production of oestrogen inhibits which hormone?
FSH
when oestrogen levels rise to a high enough level, what hormone is released from the pituitary gland?
LH
name the hormone which causes ovulation?
oestrogen
when an egg follicle becomes a corpus luteum, which hormone does it start producing?
progesterone
what are some forms of hormonal contraception?
- intrauterine system (IUS)
- the patch
- combined pill (“the pill”)
- mini-pill (POP)
- implant
- injection
what hormone(s) are involved in the IUS?
progesterone
what hormone(s) are involved in the patch?
oestrogen and progesterone
what hormone(s) are involved in the pill?
artificial oestrogen and progesterone
what hormone(s) are involved in the mini-pill?
progesterone
what hormone(s) are involved in the implant?
progesterone
what hormone(s) are involved in the injection?
progesterone
how does the IUS work?
- small, t-shaped plastic device is inserted into uterus
- progesterone released which thickens mucus in cervix, stopping sperm from reaching the egg
- thins womb lining and can prevent egg being released
how does the patch work?
- sticky patch around 5x5cm delivers oestrogen and progesterone through skin
- prevents ovulation and thickens cervical mucus so harder for sperm to travel through cervix
- thins womb lining so less likely an egg will implant there
how does the pill work?
- hormones prevent ovaries from releasing an egg
- more difficult for sperm to reach egg to implant in lining of womb
how does the mini-pill work?
- progesterone thickens mucus in cervix so sperm can’t reach egg
- thins womb lining and sometimes prevents release of egg
how does the implant work?
- progesterone steadily released into bloodstream
- thickens mucus in cervix so sperm can’t reach egg
- thins womb lining
- sometimes prevents release of egg
- small, flexible tube around 40mm long that is inserted under skin of upper arm
how does the injection work?
- progesterone thickens mucus in cervix and stops sperm from reaching egg
- thins womb lining and sometimes prevents release of egg
what are the effectivenesses of hormonal contraceptions?
- IUS = >99%
- patch = quite effective and unlike some oral contraceptives, still works during D&V
- pill = >99%
- mini-pill = >99%
- implant = >99%
- injection = >99%
extra info on the IUS?
- works for 3-5 years
- can be used whether you’ve had children or not
extra info on the patch?
- lasts 1 week
- change every week for 3 weeks, then week off
- during week off, there’s often withdrawal bleed
extra info on the pill?
- taken in a ‘21 day pill, 7 day no pill’ cycle
- sometimes placebo taken in 7 day off part so habit isn’t broken
- period occurs in 7 day break but usually lighter and less painful
extra info on the mini-pill?
- must be taken every day around same time
- if you have D&V it may not work
extra info on the implant?
- can last for 3 years
- often periods stop (amenorrhoea)
- fitted in first 5 days of menstrual cycle then immediate protection
- condoms should be worn for 7 days for protection
extra info on the injection?
- lasts up to 3 months
- useful for women who may forget to take a pill every day
what are some forms of non-hormonal contraception?
- sterilisation
- intrauterine device (IUD), copper coil
- “natural methods”
- barrier e.g. condoms, diaphragm etc
how does sterilisation work?
- surgical procedure to cut or tie tubes in reproductive system
- in women, means eggs prevented form travelling from ovaries to uterus
- in men, prevents sperm from being ejaculated
how does the IUD work?
- t-shaped system containing copper
- inserted into uterus
- prevents sperm from surviving
- alter lining of uterus so fertilised egg can’t implant
- can be kept for up to 10 years
how do “natural methods” work?
- not having sex when most fertile (around ovulation)
- ‘withdrawal’; when penis is removed prior to ejaculation
how do barrier methods work?
- male condom worn over penis to prevent entry of sperm into vagina
- female condom worn inside vagina during sex
- diaphragm fits over cervix to stop sperm meeting egg
- diaphragm has to be fitted by GP/nurse first time used and is used in conjunction with spermicide
what are the effectivenesses of non-hormonal contraceptions?
- sterilisation = >99%
- IUD = >99%
- ‘natural methods’ = least effective
- barrier = fairly effective (more so when used properly)
what are some reasons for infertility?
men:
- sperm issues e.g. sperm motility and semen quality
- blocked tubes (sperm ducts)
women:
- ovulation
- blockage of oviduct/fallopian tubes
- mucus build up
- follicle does not mature
how does hormonal imbalance contribute to infertility?
- a leading cause of infertility in women since inability to ovulate and regulate hormone levels can cause production of too much or too little of one hormone; symptoms can be detected to allow for treatment asap
- irregular menstruation
- excessive bleeding/too little bleeding
- absence of menstrual period for long periods of time
- excessive weight gain/loss
what are some treatments for infertility?
- FSH treatment
- IVF
- egg donation
- surrogacy
- ovary transplants
- artificial insemination
what is FSH treatment?
injections of clomiphene or FSH (stimulates follicular development)
what is IVF?
egg is removed form ovaries and fertilised with sperm in a lab; fertilised egg (embryo) then returns to womb to grow and develop
what is egg donation?
donor provides an egg
what is surrogacy?
another woman carries and gives birth to your child
what are ovary transplants?
relatively new; doctors transplant healthy ovaries from donor
what is artificial insemination?
directly inserting sperm into uterus
describe IVF
- FSH used to encourage production of mature eggs which increases number of eggs available for fertilisation
- eggs removed from uterus
- egg is fertilised outside body
- embryo is replanted back into uterus
suggest ethical arguments against IVF treatment
certain religious groups view IVF as an unnatural way to conceive/ they may believe that if God has caused you to be unable to conceive then you shouldn’t try via other methods
what is tropism?
growth in response to an external stimulus
- [plants detect stimuli in their environment and respond by growth in a particular direction
what would the growth of roots be described as?
- negatively phototropic
- positively gravitropic
where is auxin found?
made in tips of shoots and roots
what effect does auxin have on plant growth?
stimulates shoot cells to grow longer, but inhibits growth of root cells
how do plants respond to light directly above?
the auxin diffuses and distributes evenly as the light is directly above the plant tip, so all cells grow at same rate, plant can grow directly upwards
how do plants respond to light not directly above?
growing towards light as auxin concentration is more on shaded side of plants so that on that side the cells elongate and grow/bend towards light
true or false: the shoots of plants grow towards light
true
true or false: the roots of a plant are negatively geotropic and shoots are positively geotropic
false
true or false: roots respond more strongly to water than gravity
true
true or false: auxins affect plants by speeding up the growth in roots and shoots
false
true or false: when a plant is exposed to light from one side only, auxins collect on the lit side of the plant
false
true or false: if a plant is put on its side, auxins will collect in the lower side of the roots
true
what are some commercial uses of plant hormones?
- killing weeds
- promoting root growth
- delay ripening
- encourage ripening
- producing seedless (parthenocarp) fruit
- controlling dormancy
what is parthenocarpy?
production of seedless fruit (mainly using auxins); if auxins are applied to unpollinated flowers, the plant produces seedless fruit
what plant hormone(s) are involved in parthenocarpic fruit?
auxin;
fruit develops without ovum being pollinated
what plant hormone(s) are involved in rooting compounds?
auxin;
allow to clone a plant using rooting powder
what plant hormone(s) are involved in selective weedkiller in lawns?
auxin;
makes the weeds grow too fast and the rapid uncontrolled growth kills them
what plant hormone(s) are involved in altering dormancy?
gibberellins/auxin;
seeds triggered to germinate flowers made to open
what plant hormone(s) are involved in delaying ripening?
auxin;
delay conversion of starch to sugars
what plant hormone(s) are involved in promoting ripening?
ethene;
triggers conversion of starch into sugars
what is the benefit to humans of parthenocarpic fruit?
seedless fruit
what is the benefit to humans of rooting compounds?
robust cutting (means to clone plants)
what is the benefit to humans of selective weedkiller in lawns?
weedfree lawn
what is the benefit to humans of altering dormancy?
triggers seeds to germinate in winter
what is the benefit to humans of delaying ripening?
can harvest plant at same time prevent fruit drop, fruit less damaged in transport
what is the benefit to humans of promoting ripening?
fruits ready earlier in growing season, or after transport in unripe state
what is ADH?
a hormone secreted by the pituitary gland which increases water reabsorption in the kidney (making the kidney tubules more permeable to water)
what is glucagon?
a hormone produced by the pancreas which works with insulin to control blood sugar levels; it increase blood glucose concentration by converting glycogen into glucose
what is homeostasis?
the maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions
what is the hypothalamus?
the part of the brain that is the regulation centre for temperature and water balance of the body
what is insulin?
a hormone produced by the pancreas which controls the body’s blood sugar levels; it works to decrease glucose levels
what is a kidney?
the organ in the body that maintains water balance and produces urine
what is a nephron?
a kidney filtering unit
what is osmosis?
the net movement of water molecules from a region of high water potential to a region of low water potential, across a partially permeable membrane
what is a renal artery?
the blood vessel that provides the kidney with blood
what is a renal vein?
the blood vessel that takes blood away from the kidney
what is type 1 diabetes?
a conditioning which the pancreas fails to produce insulin, resulting in high blood sugar levels
what is type 2 diabetes?
a condition in which the person develops insulin resistance or doesn’t produce enough insulin
what is urine?
a liquid produced by the kidneys to help maintain water balance; containing mineral ions, water and urea
what is vasoconstriction?
the constriction of blood vessels
what is vasodilation?
the dilation of blood vessels
what are the organs of homeostasis?
- brain
- lungs
- skin
- kidneys
- pancreas
- muscles
what role do the lungs play in homeostasis?
- controls oxygen and CO2 levels
- impacts breathing rate
what role does the skin play in homeostasis?
- helps thermoregulation (controlling body temperature)
what role do the kidneys play in homeostasis?
- control water and salt balance
(water balance = osmoregulation)
what role does the pancreas play in homeostasis?
- controls blood glucose level e.g. by secreting insulin
what role do the muscles play in homeostasis?
- thermoregulation e.g. shivering
- can store glycogen so can help to control blood sugar level
what role does the brain play in homeostasis?
- monitoring and controlling many things within the body
what is normal body temperature?
approx. 37 degrees celsius
(optimum temperature for action of many enzymes)
what affect can low temperatures have on the body/enzymes?
- cause reactions to occur too slowly
- very low temperatures can cause hypothermia and, if untreated, death
what affect can high temperatures have on the body/enzymes?
- cause enzymes to be denatured
- heat stroke, dehydration and, if untreated, death
how is body temperature controlled?
- the hypothalamus is responsible for regulating temperature
- called the thermoregulatory centre
how does the hypothalamus monitor/manage body temperature?
receives information from:
- skin receptor cells which monitor external temperatures
- internal receptor cells which monitor blood temperature
when a hang of temperature is detected, brain causes responses throughout body by sending impulses to effectors to return temp to normal
what are some of the body’s responses to being too hot?
- erector muscles relax so hairs lie flat against skin so not trapping heat
- sweating
- vasodilation
how does sweating affect body temp?
evaporation of water on skin caused by heat of skin and takes heat away from body
how does vasodilation affect body temp?
- blood vessel dilation results in increased blood flow towards surface of skin
- increased blood flow beneath the epidermis results in increased heat loss
what are some of the body’s responses to being too cold?
- erector muscles contract so hair are erect which traps heat (goosebumps); insulation
- sweat glands do not make sweat
- vasoconstriction
- shivering
how does vasoconstriction affect body temp?
- blood vessel constriction results in decreased blood flow towards the skin’s surface
- decreased blood flow beneath the epidermis results I decreased heat loss
how does shivering affect body temp?
muscles contract and relax quickly, making cells respire more quickly, transferring extra energy by heating
what are the major components of the negative feedback system?
- receptors
- control centre
- effector organs
- neurons/nerve cells
- response
what conditions occur over temps <35->40?
- hypothermia = <35
- normal = 36.5-37.5
- fever = >37.5 or 38.3
- hyperthermia = >37.5 or 38.3
- hyperpyrexia = >40.0 or 41
what’s the difference between fever and hyperthermia?
the underlying mechanism
why do blood glucose levels need to be controlled?
- too high causes cells to be crenated
- too low causes lysis
what is the role of the pancreas?
it monitors and controls blood glucose levels and releases different hormones depending on the level
is insulin used when blood glucose is too high or low?
high
is glucagon used when blood glucose is too high or low?
low
what is the pancreas made up of?
Islets of Langerhans
when do good sugar levels go up?
eating a meal
when do blood sugar levels go down?
exercising
what is the response of target organs to too high blood glucose?
- pancreas release insulin
- liver and muscles absorb glucose and convert it to glycogen for storage
what is the response of target organs to too low blood glucose?
- pancreas releases glucagon
- liver and muscles convert glycogen to glucose and release it into the blood
what’s the difference between excretion and egestion?
- excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism
- egestion is the final act of digestion, when organisms eliminate solid, semisolid and/or liquid waste material from digestive tract via anus
why do we have to excrete urea in urine?
urea is toxic
what happens to urine if you take in a lot of water?
your kidneys produce lots of dilute urine so excess water is removed from body; urine will appear almost colourless
what happens to urine if you are short of water?
kidneys produce little, concentrated urine and water is saved. for body’s use
what is the function of. the kidney?
- filter the blood (remove urea but keep protein)
- reabsorb small molecules such as glucose
- control water levels
where are the kidney found?
urinary system
what structures are found in the kidneys?
- arteriole
- glomerulus
- Bowman’s capsule
- convoluted tubules
- loop of Henle
- capillaries
- nephron
- collecting duct
what does the Bowman’s capsule do?
- surrounds ball of capillaries, known as capillary know
- high pressure created in this knot since diameter of capillary leaving knot is narrower than the capillary entering
what does the collecting duct do?
- collects urine and transports it to the pelvis through ureters, where it is temporarily stored in the bladder
what does the proximal convoluted tubule do?
- reabsorbs around 65% of filtered load e.g. amino acids, glucose, solute etc
- regulates acid-base balance by reabsorbing around 80% of filtered bicarbonate
what does the loop of Henle do?
- reabsorb water and sodium chloride from filtrate
what does the distal convoluted tubule do?
- partly responsible for regulation of potassium, sodium, calcium and pH
- conditional reabsorption of sodium ions and water maintains pH and sodium-potassium level in blood cells
what are the three main stages of osmoregulation?
- ultrafiltration
- selective reabsorption
- removal of waste
what happens during ultrafiltration?
- high pressure built in glomerulus which squeezes water, urea, ions and sugars out of blood into Bowman’s capsule
- membranes between capillary and Bowman’s capsule act like filters so big molecules, e.g. proteins and blood cells, stay in the blood
what happens during selective reabsorption?
- as liquid flows along nephron, useful substances are reabsorbed into blood
1. sugars reabsorbed; involves active transport against conc. gradient
2. sufficient water reabsorbed by osmosis
what happens during removal of waste?
- remaining substances (inc. urea) continue out of nephron, into ureter and down to bladder as urine
- ADH affects permeability of collecting duct; more ADH means more permeable collecting duct so more water is reabsorbed
what does ADH stand for?
Anti-Diuretic Hormone
how does the body respond to lack of water?
more ADH secreted so more water absorbed
how does the body respond to too much water?
less ADH secreted so less water absorbed
what are three types of sports drinks?
- hypertonic
- isotonic
- hypotonic
what is the function of hypertonic sports drinks?
- contain conc. of salt and sugar higher than typical blood levels
- suitable for supplying glucose particularly for intense physical exercise
what is the function of isotonic sports drinks?
- contain similar conc. of salt and sugar as human body and primarily used for hydration and fluid replacement
what is the function of hypotonic sports drinks?
- contain conc. of salt and sugar lower than typical blood levels; suitable for rapid rehydration
