Homeostasis and Response Flashcards
what is negative feedback?
returning body conditions back to normal
define homeostasis
maintenance of a constant internal environment
how is water content controlled in the body?
water is absorbed from food and drink and lost via sweat, urine. and breathing
why is water content controlled in the body?
to maintain concentration gradient for effective osmosis so cells won’t be damaged by too much/little water
how is ion content controlled in the body?
ions are absorbed from food, so amount eaten, and are lost via sweating
why is ion content controlled in the body?
ions are needed in the body
how is temperature controlled in the body?
behaviour and vasoconstriction/dilation
why is temperature controlled in the body?
to keep enzymes healthy and working efficiently
how are blood glucose levels controlled in the body?
food intake, amount of respiration, glucagon, insulin
why are blood glucose levels controlled in the body?
glucose is necessary for respiration
how is co2 concentration in the blood controlled by the body?
rate of respiration and breathing
why is co2 concentration in the blood controlled by the body?
co2 is toxic and can damage cells
what is the homeostasis response pattern?
- stimulus
- receptor
- sensory neurone
- coordination centre
- relay neurone within coordination centre
- motor neurone
- effectors
- response
what is a stimulus?
change in environment away from optimum conditions
what is the coordination centre?
structures which receive and process info from receptors
what are receptors?
cells which detect a stimulus
what are effectors?
organs which carry out response to stimulus
what is the response in the homeostasis response pattern?
return to optimum conditions by causing a muscle to contract or gland to secret hormones
where do sensory neurones transmit information between?
from the receptor cells to the CNS
where do relay neurones transmit information between?
inside the CNS, transmit impulses from the sensory neurone to the motor neurone
where do motor neurones transmit information between?
from the CNS to the effectors
why are reflexes faster?
they don’t involve conscious thought and use the nearest part of the CNS
what do all control systems include?
- receptors which detect stimuli
- coordination centre (eg brain, spinal cord, pancreas) which receives and processes information from receptors around the body
- Effectors to bring about responses to restore optimum levels
what are the features of nerve cells?
- long fibre (axon) insulated by a fatty (myelin) sheath - can carry messages up and down the body.
- Tiny branches (dendrons) which branch further as dendrites at each end - receive incoming impulses from other neurones.
what is a reflex?
automatic and rapid response to a stimulus to minimise any damage to the body from potentially harmful conditions - does not involve the conscious part of the brain, which makes it much quicker.
what is the reflex arc?
stimulus ⇒ receptor ⇒ sensory neurone ⇒ relay neurone ⇒ motor neurone ⇒ effector ⇒ response
what is a synapse?
microscopic gap where 2 neurones meet
how do impulses travel across synapses?
- electrical impulse travels along first axon.
- triggers nerve-ending of neurone to release neurotransmitters.
- diffuse across synapse and bind with receptor molecules on post-synaptic membrane
- receptor molecules on second neurone bind only to the specific neurotransmitters released from the first neurone.
- stimulates the second neurone to transmit the electrical impulse.
what are the 3 parts of the brain?
medulla, cerebral cortex, cerebellum
what does the medulla do?
controls automatic actions eg heartbeat, breathing
what does the cerebellum do?
co ordinates movement and balance
what does the cerebral cortex control?
consciousness, intelligence, memory, language
what are some brain disorders that can be investigated and treated?
- cancer
- epilepsy
- dementia
- paralysis
what are some treatments for brain disorders?
- surgery
- electrical stimulation
- chemotherapy
- medication
how are brain disorders investigated?
- surgery
- MRI scans
- x-rays
- thermal imaging
what are some difficulties in investigating and treating brain disorders?
- infection
- injury - brain damage eg nerves, blood vessels
- very complex
- long operations
what are the benefits of procedures carried out on brain and nervous system?
- treat the patient
- increases understanding for the future
- helps develop new procedures and medicines
what are the risks of procedures carried out on brain and nervous system?
- permanent brain damage
- loss of function of parts of body
- memory loss
- paralysis
what are the parts of the eye?
- ciliary muscle
- lens
- vitreous humour
- retina
- sclera
- choroid
- fovea
- optic nerve
- suspensory ligaments
- rods
- cones
- iris
- pupil
- cornea
- conjunctiva
- aqueous humour
what are the cones in the eye?
3 types - RGB - to see in colour
what is the ciliary muscle?
muscle in the eye attached to ligaments which pulls on ligament to change shape of lens to alter amount of refraction done
what is the function of the vitreous humour?
keeps eyeball spherical
what is the retina?
a clear transducer in the eye where receptor cells are - cones and rods
what is the choroid?
a black layer of tissue at the back of the eye
what is the sclera?
the mainly white outer layer of the eye which protects it
what is the fovea?
where light needs to be focussed in the eye
what is the optic nerve?
very wide nerve to carry clear impulses to brain
what are suspensory ligaments?
attached to lens - changes shape with muscles
what is the lens?
made of curved cells and refracts light
what is the function of rods in the eye?
seeing in monochrome
what is the iris?
circular protein muscle which is able to contract and relax to change size of pupil
what is the aqueous humour?
a gel-like substance which keeps the eye’s curves in place
what is the conjunctiva?
thin layer of tissue which protects lens and cornea
what is the cornea?
clear and curved to refract light
what is the pupil?
a hole that changes size/shape to control amount of light that enters the eye
what are the type of muscles that work opposite to each other?
antagonistic
when the pupil is dilated, are the circular muscles relaxed or contracted?
relaxed
when the pupil is dilated, are the radial muscles relaxed or contracted?
contracted
when the pupil is constricted , are the circular muscles relaxed or contracted?
contracted
when the pupil is constricted, are the radial muscles relaxed or contracted?
relaxed
what is the purpose of the pupil reflex?
so the right amount of light enters the eye, to prevent damage to retina
what is accomodation?
the process by which the lens changes shape to make sure the light focuses on the retina
what changes in the eye to focus on a near object?
- ciliary muscles contract and have a smaller diameter
- suspensory ligaments become looser and slacken
- lens becomes thicker and more rounded - more convergent
- light is refracted more - more curved lens
what changes in the eye to focus on a far object?
- ciliary muscles relax and have a thicker diameter
- suspensory ligaments tighten and become thinner
- lens become longer and thinner - less convergent
- light is refracted less - less curved lens
what is myopia?
short-sightedness
what causes myopia?
the lens is too strong (too round) or the eye is too long so too much refraction is done and light rays meet before the retina
how is myopia corrected?
by concave lenses which cause light to refract outwards (diverge) more than they normally would, before they reach the eye so when the lens refracts more than it should, this is cancelled out by the effect that the glasses had
what is hyperopia?
long-sightednes
what causes hyperopia?
the lens is too weak (too thin) or the eye is too short so not enough refraction is done and light rays meet behind the retina
how is hyperopia corrected?
by convex lenses which cause light to refract inwards (converge) more than they normally would, before they reach the eye so when lens refracts less than it should, this is cancelled out by the effect that the glasses had
what happens to the function of enzymes if the temperature is too low?
there is little kinetic energy, so enzymes move slowly and less complexes form, slowing rate of reaction and reducing rate of respiration - less energy
what happens to the function of enzymes if the temperature is too high?
enzymes denature and active site becomes damaged, so rate of reaction will stop
what happens in the body if there is an increase above the norm in body temp?
- change detected by thermoreceptors in the skin and in thermoregulatory centre in hypothalamus
- heat loss responses
what are the 2 heat loss responses?
vasodilation and sweating
what is vasodilation?
- capillaries dilate so more blood flows through them
- shunt vessel will constrict so more blood moves through capillaries
- if capillaries are wider, more heat will be lost by radiation as more blood is closer to skin surface
how does sweating create heat loss?
- warm liquid on skin surface will evaporate
- evaporation involves a change of state from liquid to gas
- energy is required for a state change, so energy from body is released
what happens in the body if there is a decrease below the norm in body temp?
- change detected by thermoreceptors in the skin and in thermoregulatory centre in hypothalamus
- heat conservation responses
what are the 3 heat conservation responses?
reduce sweating, shivering, vasoconstriction
what is vasoconstriction?
- capillaries constrict and shunt vessel so less blood flows through capillaries
- capillaries are less wide so there is less surface area - less blood is near the skin surface - less heat loss via radiation
how does shivering increase body temperature?
- rapid muscle contraction
- required energy from respiration so rate of respiration increases to meet demands of contracting muscles
- excess energy is released so more heat energy is provided to increase body temp
how does reducing sweating conserve heat?
- liquid is not evaporating so energy is not used unnecessarily to cause evaporation
- energy is not lost so heat is conserved
what are hormones?
proteins secreted by glands which are transported to target organs by bloodstream
how do hormones work?
- secreted by endocrine gland cell
- enter bloodstream
- could affect any cell, as every body cell is next to a capillary - if the cell has the correct receptor, the cell will recognise the hormone molecule
what are 5 differences between nervous and hormonal control?
- type of message: electrical impulse vs chemical message
- speed of message: immediate vs slight delay
- transmission: along neurones vs bloodstream
- duration of response: short lasting vs longer lasting
- specificity: specific target cells in effectors vs more general cell groups with specific receptors
what is the function of the pituitary gland?
releases several different hormones whose target organ is another endocrine gland, causing this gland to release the correct hormone to the body
what hormones does the pituitary gland release?
- growth hormone
- TSH
- FSH
- LH
what is the function of growth hormone?
controls growth in children
what is TSH?
thyroid stimulating hormone
what is FSH?
follicle stimulating hormone - stimulates ovaries to release oestrogen
what is LH?
luetenising hormone -stimulates ovaries to release egg
what hormone does the thyroid release?
thyroxine
what is the function of thyroxine?
- controls basal metabolic rate
- also stimulates protein synthesis for growth and development
what is thyroxine made from?
iodine and amino acids
what hormones does the pancreas release?
insulin and glucagon
what hormone do the adrenal glands release?
adrenaline
what does adrenaline do?
- prepares body for stressful situations - increased muscle movement, therefore increased respiration
- increases heart rate and therefore supply of oxygen to body cells
what is the function of hormones released by testes?
- controls development of secondary sexual characteristics
- involved in sperm production
explain the process of IVF
- FSH & LH are given to stimulate the growth of lots of eggs.
- Eggs are collected
- Eggs are fertilised in a petri dish in a laboratory, using sperm from the father.
- These fertilised eggs grow into embryos and are implanted into the woman’s uterus.
what happens if there is an Increase of blood glucose above the norm?
- detected by receptors in the pancreas
- insulin released
- glucose moves from blood into body cells (for respiration)
- excess glucose is converted to glycogen inside cells in liver and muscles
what happens if there is a decrease of blood glucose below the norm?
- detected by receptors in the pancreas
- glucagon released
- glucose released from body cells into blood
- glycogen converted back into glucose from liver
what are the risk factors for type 1 diabetes?
genetic predisposition - hereditary condition
what is the age of onset for type 1 diabetes?
early life
what is the effect on control of blood glucose by type 1 diabetes?
cells in pancreas are unable to produce sufficient insulin so glucose concentration in blood stays high
what are the symptoms for type 1 diabetes?
thirst, frequent urination, weight loss
what is the treatment for type 1 diabetes?
injections/administration by pump of insulin, diet, exercise
is type 1 diabetes reversible?
no
why can’t insulin for type 1 diabetes be taken as a tablet?
enzymes would break it down in digestive system (as it is a protein), so it wouldn’t reach cells
what does type 1 diabetes increase the risk of?
retinopathy
what are the risk factors for type 2 diabetes?
obesity, genetics in specific ethnic groups
what is the age of onset for type 2 diabetes?
usually adulthood
what is the effect on control of blood glucose in type 2 diabetes?
cells in target organs are unable to respond to insulin so glucose is not absorbed from blood and concentration stays high
what are the symptoms of type 2 diabetes?
thirst, frequent urination, tingling in fingers and toes
what is the treatment for type 2 diabetes?
control and monitoring of diet and exercise
is type 2 diabetes reversible?
yes
what is urine made from?
excess water + urea + (excess) ions
how is urea produced?
formed from excess amino acids which are deaminated in liver to form ammonia which is toxic and must be removed so ammonia is converted to urea for excretion
what is the function of the renal artery?
brings dirty blood to kidneys from liver to be filtered
what is the function of the renal veins?
sends clean and filtered blood back to body
where is oestrogen produced?
ovaries
what is the function of oestrogen?
- controls development of female secondary sex characteristics
- thickens uterus lining
- inhibits release of FSH from pituitary gland
- stimulates release of LH
what is the function of follicle stimulating hormone?
- travels to ovary and stimulates egg to grow inside follicle
- causes ovary to release oestrogen
where is follicle stimulating hormone produced?
pituitary gland
what is the function of Luteinising Hormone?
causes ovulation
where is luteinising hormone produced?
pituitary gland
what is the function of testosterone?
stimulates sperm production controls development of male secondary sex characteristics
where is testosterone produced?
testes
what is the function of progesterone?
- if pregnant, it continues to be produced to keep the lining thick
- if not pregnant, production stops and menstruation occurs
where is progesterone produced?
yellow bodies
what are yellow bodies?
develops from the follicle remnants after ovulation
ova + sperm -> ?
zygote ⇒ balstocyst
what is the role of hormones in the menstrual cycle?
- FSH is made by pituitary
- FSH causes egg to grow inside follicle
- FSH causes ovary to release oestrogen
- oestrogen inhibits release of FSH, stimulates production of LH, thickens uterus lining
- LH causes ovulation
- progesterone produced by yellow body
- menstruation or pregnancy
how do oral contraceptives work?
- contain oestrogen and/or progesterone
- daily pill taken for about 27 days
what are some cons of oral contraceptives?
have to remember to take it every day, no protection from STIs
what is a pro of oral contraceptives?
convenient
how do injections, implants, skin patches that slowly releases progesterone work?
stops egg release
what are some pros of injections/implants/skin patches that slowly releases progesterone?
- don’t have to remember to take tablets
- available to people who can’t take tablets
what is a con of injections/implants/skin patches that slowly releases progesterone?
FEAR OF NEEDLES
how do barrier methods (condoms and diaphragms) work?
physical barrier between sperm and egg
what is a con of barrier methods?
dont work 100% of the time
what is a pro of barrier methods?
relatively easy to use
how do intrauterine devices work?
- release hormones
- copper kills sperm
- prevents implantation of embryo - can’t attach to uterus wall
what are some cons of intrauterine devices?
- no protection from STIs
- must be removed by a doctor (not immediate)
what is a pro of intrauterine devices?
long term - 6-10 years
how do spermicidal agents work?
gel inserted inside vagina that kill sperm cells
what is a con of spermicidal agents?
don’t protect from STIs
what are some pros of spermicidal agents?
- quick
- convenient
- reliable
how does abstinence and ovulation cycle tracking work?
egg can’t be fertilised if there is no sperm
what is a con of abstinence and ovulation cycle tracking?
unreliable
what is a pro of abstinence and ovulation cycle tracking?
can follow religious beliefs eg catholics
how does surgical sterilisation work
cutting and sealing tubes to physically stop sperm/egg cells being released
what are some cons of surgical sterilisation?
- permanent
- risk in surgery
what is a pro of surgical sterilisation?
reliable, no chance of getting pregnant
what is positive phototropism?
when plant shoots grow towards the light
how is phototropism advantageous for a plant?
plant can absorb more light, leading to more photosynthesis and glucose production. allows plant to respire more so they have more energy to grow
what is gravitropism?
plant roots grow in direction of gravity
how is gravitropism advantageous for a plant
roots grow deeper into the soil which allows them to absorb more water for photosynthesis and absorb minerals and ions. also means they stay rooted and provide stability.
when do plants shoots need to respond to gravity rather than light
when seedlings are underground and the shoot is growing upwards which is negative gravitropism - there is no light to respond to as it’s underground
what is the function of auxins in root cell?
make roots grow towards gravity
what is the function of auxins in shoot cell?
make plant grow towards light
describe the process of positive phototropism using auxins
- light is directly above plant so auxins are evenly distributed and produced from the tip of the shoot
- as light moves there is a difference in concentration and auxins move away from the light
- this causes auxins to be in high concentration on shaded side, making cells on that side grow faster and shoot end ups growing towards light
describe the process of positive geotropism using auxins
- in roots, auxins inhibit cell elongation
- gravity causes auxins to accumulate on underside of root leading to uneven distribution
- cells on underside of root dont grow as large as cells on upper surface so upper surface will grow at a faster rate
- this will bend the root in the direction of gravity
what are some commercial uses of auxins?
- used to help promote growth of plants during plant cuttings
- used in weedkillers (concentrated auxins make cells grow too fast and abnormally so the plant dies prematurely)
what are some commercial uses of gibberellins?
- increase fruit size
- end seed dormancy to help in germination
- promote flowering
what is a commercial use of ethene?
controls ripening of fruit - used in storage/transport of fruits
