2- co-ordination and response and reproduction Flashcards
homeostasis
the control or regulation of the internal conditions of a cell or organism
it is important for an organism to keep internal conditions within set limits to ensure
they stay healthy and maintain optimum conditions to allow the organism to function in response to internal and external changes, if these limits are exceeded the organisms may die
homeostasis maintains optimal conditions for
enzyme action and all cell functions
the core temperature for a human is
37 degrees c
if human body temperature changes within 2 degrees it can be fatal because
the change would stop essential enzymes from functioning optimally
body temperature is monitored and controlled by
the thermoregulatory centre in the base of the brain as blood passes through it
the thermoregulatory centre contains
temperature receptors and sends nervous impulses to the thermoregulatory centre, the brain then coordinates a cooling or heating response depending on what is required
the skin contains
temperature receptors and sends nervous impulses to the thermoregulatory centre and the brain then coordinates a cooling or heating response depending on what is required
heat exchange occurs
at the body surface as this is where the blood comes into closest proximity to the environment
one way to increase heat loss is
to supply the capillaries in the skin with a greater volume of blood which then loses heat to the environment via radiation
arterioles have muscles in there walls that
can relax or contract to allow more or less blood to flow through them
during vasodilation
the muscles in arterioles relax causing the arterioles near the skin to dilate and allowing more blood to flow through capillaries
sweat is secreted
by sweat glands
the hair erector muscles in the skin relax causing
the hairs to lie flat which stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
one way to decrease heat loss is to
supply the capillaries inn the skin with a smaller volume of blood, minimising the loss of heat to the environment via radiation
shivering is a
reflex action in response to a decrease in core body temperature. muscles contract in a rapid and regular manner. the metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
the nephrons of the kidneys contain structures called
tubules through which filtrate passes on its way to the bladder. water can be reabsorbed from this filtrate as it passes along these tubules. if the water content of the blood is too high then less water is reabsorbed but if it is too low then more water is reabsorbed
the pituitary gland in the brain constantly releases a hormone called
ADH
adh affects the
permeability of the collecting ducts to water
the quantity of adh released depends on
how much water the kidneys need to reabsorb from the filtrate
if the water content of the blood falls below a certain level-
the blood is too concentrated, receptors detect this and stimulate the pituitary gland to release more ADH, this causes the collecting ducts of the nephrons to become more permeable to water, this leads to more water being reabsorbed from the collecting ducts, the kidneys produce a smaller volume of urine that is more concentrated
if the water content of the blood rises above a certain level
the blood is too dilute, receptors detect this and stimulate the pituitary glands to release less ADH, this causes the collecting ducts of the nephrons to become less permeable to water, this leads to less water being reabsorbed from the collecting ducts, the kidneys produce a larger volume of urine that is less concentrated
homeostasis is under
involuntary control
a stimulus
a change to the environment
a receptor
receptor cells that detect stimuli
a coordination centre
a place which receives and processes information from receptors
effector
a muscle or gland which brings about responses to restore optimum levels
plants need to be able to grow in response to
certain stimuli
tropism
the directional growth responses in response to light and gravity
phototropism
response to light
geotropism
response to gravity
if the growth is towards the stimulus
the tropism is positive
if the growth is away from the stimulus
the tropism is negative
as shoots grow upwards
away from gravity and towards light the shoots are a positive phototropic response and a negative geotropic response
as roots grow downwards
into the soil and away from light and towards gravity, roots show a negative phototropic response and positive geotropic response
plants produce plant growth regulators called
auxins to coordinate and control directional growth responses such as phototropism and geotropisms
auxins are produced in
the tips of the shoots and the roots
in the shoots auxins promote
cell elongation
more auxin in shoots =
more cell elongation = more growth
in the roots auxins
inhibit cell elongation
more auxin in roots =
less cell elongation = less growth
the distribution of auxin in the shoots is affected by
light and gravity whereas the distribution in the roots is primarily affected by gravity
unequal distributions of auxins cause
unequal growth rates in plant roots and shoots
two different control systems in humans are called
nervous system, hormonal system (endocrine)
changes in our external environment or the internal environments of our body act as
stimuli- the nervous and hormonal systems coordinate a suitable response to these stimulis
the nervous system response to stimuli
information is sent through the nervous system as electrical impulses- these are electrical signals that pass along nerve cells known as neurons, these impulses travel along neurones at very high speeds, this allows rapid responses to stimuli
the endocrine system response to stimuli
information is sent through the endocrine system as chemical substances known as hormones. hormones are carried by the blood and can therefore circulate around the whole body. hormones transmit Information from one part of the organism to another and bring about a change. they alter the activity of one or more specific target organs
hormones are used to control
functions that do not need instant responses
central nervous system
the brain and spinal cord
peripheral nervous system
all of the nerves of the body
information is sent through the nervous system as
electrical impulses
bundle of neurones is a
nerve
the nerves spread out
from the central nervous system to all the other regions of the body as well as the sense organs
the central nervous system acts as a
central coordinating centre for the impulses that come from or are sent out to any part of the body
neurons have a
cell body where the nucleus and main organelles are found and cytoplasmic extensions from this body called axons and dendrites
the axon is the
main long fibre of the neurone
the axon is insulated by
a fatty myelin sheath with small uninsulated sections along its length called nodes- this means that electrical impulses don’t travel down the whole axon, they jump from one node to the next
many extensions called
dendrites extend out from the cell body of the neurone and at the far end of the axon- this means neurones can connect to many other neurones and receive impulses from them forming a network for easy communication
main types of neurones
sensory neurones, relay neurones, moter neurones
sensory neurones carry
impulses from sense organs to the central nervous system
relay neurones are found in
inside the central nervous system and connect sensory and motor neurones
moter neurones carry
impulses from the central nervous system to effectors
sensory neurones are
long and have a cell body branching off the middle of the axon
relay neurones are
short and have a small cell body at one end with many dendrites branching off it
moter neurones are
long and have a large cell body at one end with long dendrites branching off it
pathway of the nervous system
stimulus -> sensory neurone -> relay neurone -> moter neurone -> effector -> response
describe the pathway of nervous system
first a stimulus is received by a sensory neurone, when a receptor is stimulated it produces electrical impulses. these impulses then travel along a sensory neurone to the central nervous system to either the brain or spinal chord. in the central nervous system the impulses are passed on to a relay neurone. the relay neurone links to the moter neurone along which the impulses travel until they reach the effector. the effector is what carries out the response
neurones don’t
come into direct contact with each other
where the dendrites
of two neurones meet a junction known as a synapse is formed
at a synapse
there is a very small gap between neurones- this gap is known as the synaptic cleft or synaptic gap
electrical impulses can’t
travel directly from one neurone to the next due to the synaptic cleft. instead the electrical signal is briefly converted to a chemical signal that can cross the synaptic cleft.
the chemical signalling molecules used to transfer the signal between neurones at a synapse are known as
neurotransmitters
once neurotransmitters cross the synaptic cleft and meet the neurone on the opposite side
the signal is converted back into an electrical impulse which can then pass along the neurone
how an impulse is passed across a synapse
the electrical impulse travels along the first axon of the first neurone known as the presynaptic neurone. this triggers the end of the presynaptic neurone to release chemical messengers called neurotransmitters from vesicles. these vesicles fuse with the presynaptic membrane releasing their contents into the synaptic cleft. the neurotransmitters diffuse across the synaptic cleft and bind with receptor molecules on the membrane of the second neurone known as the postsynaptic membrane. this stimulates the second neurone to generate an electrical impulse which then travels down the second axon. the neurotransmitters are then destroyed to prevent continued stimulation of the second neurone. synapses ensure that impulses can only travel in one direction avoiding the confusion that would be caused within the nervous system if impulses were able to travel in both directions.
a reflection response does not
involve the conscious part of the brain as a coordinator of the reaction
a reflex arc is
the pathway of a reflex response, specifically the pathway taken by electrical impulses as they travel along neurones
reflex response to pain
the object (stimulus) is detected by the pain/pressure/touch receptors in the skin. a sensory neurone sends electrical impulses to the spinal chord (the coordinator). an electrical impulse is passed to a relay neurone in the spinal chord and a relay neurone synapses with a moter neurone. a moter neurone carries an impulse to a muscle in the effector. when stimulated by the moter neurone the muscle will contract and pull the foot up and away from the object (response)
the retina of the eye contains
two types of receptor cells- receptor cells that are sensitive to light known as rods and receptor cells that can detect colour known as cones
cornea
transparent lens that refracts light as it enters the eye
iris
controls how much light enters the pupil
lens
transparent disc that can change shape to focus light onto the retina
retina
contains light receptor- rods that detect light intensity and cones that detect colour
optic nerve
sensory neurones that carry impulses between the eye and the brain
pupil
hole that allows light to enter the eye
the ciliary muscle
a ring of muscle that contracts and relaxes to change the shape of the lens
the suspensory ligaments
ligaments that connect the ciliary muscles to the lens
the sclera
the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attatchment for the muscles that move the eye
the fovea
a region of the retina with the highest density of cones where eyes see particularly good detail
the aqueous humour
the watery liquid between the cornea and the lens
the vitreous humour
the jelly like liquid filling the eyeball
the choroid
a pigmented layer of tissue lining the inside of the sclera that prevents the reflection of light rays inside the eyeball
the blind spot
the point at which the optic nerve leaves the eye where there are no receptor cells
the eye when an object is close up
the ciliary muscles contract, this causes the suspensory ligaments to loosen, this stops the suspensory ligaments from pulling on the lens which allows the lens to become fatter and light is refracted more
the eye when an object is far away
the ciliary muscles relax, this causes the suspensory ligaments to tighten, the suspensory ligaments pull on the lens causing it to become thinner and light is refracted less
the eye responding to change in light intensity- dim light
photoreceptors detect change in environment (dark), radial muscles contract, circular muscles relax and the pupil dilates and more light enters the eye
the eye responding to change in light intensity- bright light
photoreceptors detect a change in environment (bright), radial muscles relax, circular muscles contract and the pupil constricts and less light enters the eye
the skin is
our largest sense organ
vasodilation of skin capillaries- inc heat
heat exchange occurs at the body surface as this is where the blood comes into closest proximity to the environment. one way to increase heat loss is to supply the capillaries in the skin with a greater volume of blood which then loses heat to the environment via radiation. arterioles have muscles in their walls that can relax or contract to allow more or less blood to flow through them. during vasodilation these muscles relax causing arterioles near the skin to dilate and allowing more blood to flow through capillaries
sweating
sweat is secreted by sweat glands, this cools the skin by evaporation which uses heat energy from the body to convert liquid water into water vapour
flattening of hairs
the hair erector muscles in the skin relax causing hair to lie flat, this stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
vasoconstriction of skin capillaries- decrease heat
one way to decrease heat loss is to supply the capillaries in the skin with a small volume of blood, minimising the loss of heat to the environment via radiation. during vasoconstriction the muscles in the arteriole walls con tract causing the arterioles near the skin to constrict and allowing less blood to flow through capillaries.
shivering
shivering is a reflex action in response to a decrease in core body temp. muscles contract in a rapid and regular manner. the metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise core body temperature
erection of hairs
the hair erector muscles in the skin contract causing hairs to stand on end. this forms an insulating layer over the skins surface by trapping air between the hairs and stops heat from being lost by radiation
information is sent through the endocrine system as
chemical substances known as hormones
hormones are carried by
the blood and can circulate around the whole body
hormones transmit information from
one part of the organism to another and bring about a change
hormones are produced by
endocrine glands
structures that make up the endocrine system
pituitary gland, thyroid, pancreas, adrenal glands, testes, ovaries
pituitary glands
a master gland which makes hormones such as lh and fsh
thyroid
produces thyroxine which controls metabolic rates and affects growth
pancreas
produces insulin which regulates glucose levels
adrenal glands
produces adrenaline
testes
produces testosterone
ovaries
produce oestrogen
a hormone is
a chemical substance produced by a gland and carried by the blood which alters the activity of one or more specific target organs
when is adrenaline produced
in situations where the body may be in danger
what does adrenaline do
increases heat rate and breathing rate- ensures glucose and oxygen can be delivered to the muscle cells at a faster rate
diverting blood flow towards muscles and away from non essential parts of the body such as the alimentary canal- ensures an increased supply of glucose and oxygen (reactants of respiration)
dilation of blood vessels inside muscles- ensures more blood can circulate through them again, supplying more glucose and oxygen
breaking down of stored glycogen to glucose in the liver and muscle cells, with glucose released by the liver being transported to active muscle cells- ensures a higher blood glucose concentration for increased respiration in muscle cells (providing greater energy for movement)
blood glucose concentration must
be kept within a narrow range so is another example of homeostasis- too high can lead to cells in the body losing water by osmosis, too low can can lead to the brain receiving insufficient glucose for respiration
what controls blood glucose levels
the pancreas and liver
how does the pancreas and liver control blood glucose levels
the pancreas acts as an endocrine gland, making and secreating hormones into the bloodstream)
if blood glucose levels get too high-
cells in the pancreas detect the increased blood glucose levels, the pancreas produces the hormone insulin, secreating it in the blood. insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen. this reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops recreating insulin
if the blood glucose levels get too low-
cells in the pancreas detect the decreased blood glucose levels. the pancreas produces the hormone glucagon. glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood. this increases the concentration of glucose in the blood back to normal levels, at which point the pancreas stops recreating glucagon
testosterone
testosterone is produced in the male testes, it is responsible for the development of secondary sexual characteristics in males
progesterone
progesterone is produced in the female ovaries. it is responsible for maintaining the uterine lining during pregnancy
oestrogen
oestrogen is produced in the female ovaries, it is responsible for the development of secondary sexual characteristics in females and regulating the menstrual cycle
sexual reproduction is
the process involving the fusion of the nuclei of two gametes to form a zygote and the production of a genetically different offspring
fertilisation
fusion of a male and female gamete
gamete
sex cell
gamete animals
sperm and ovum
gamete plants
pollen nucleus and ovum
gametes contain
half the number of chromosomes found in other body cells- they have a haploid nucleus, this is because they only contain one copy of each chromosome rather than two copies found in other body cells
a normal body contains how many chromosomes
46
each gamete has how many chromosomes
23
when male and female gametes fuse they become
a zygote
zygote
fertilised egg cell
zygotes have how many chromosomes
46
zygote nucleus is
diploid
advantages of sexual reproduction
increases genetic variation, species can adapt to new environments due to variation giving them a survival advantage, disease is less likely got affect the population due to variation
disadvantages of sexual reproduction
takes time and energy to find mates, difficult for isolated members of the species to reproduce
asexual reproduction
the process resulting in genetically identical offspring being produced from one parent
asexual reproduction does not
involve gametes or fertilisation
how many parents required for asexual reproduction
1 so there’s no fusion of gametes and no mixing of genetic information
asexual reproduction offspring are
genetically identical to the parent and eachother
plants reproduce by
asexual and sexual reproduction
bacteria reproduce by
asexual reproduction called binary fission
advantages of asexual reproduction
population can be increased rapidly when conditions are right, can exploit suitable environments quickly, more time and energy efficient, reproduction is completed much faster than sexual reproduction
disadvantages of asexual reproduction
limited genetic variation, population vulnerable to changes in conditions and may only be suitable to one habitat, disease is likely to affect the whole population
key differences between sexual and asexual reproduction
- number of parent organisms
- how offspring are produced
- level of genetic similarity between offspring
- possible sources of genetic variation
- number of offspring produced
- time taken to produce offspring
