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