5.1.1 communication and homeostasis NOT ON MOCK Flashcards Preview

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What changes might occur to an internal or external environment that an organism needs to respond to

PH, water potential, temperature, glucose, humidity, light, threat


What will a good communication system have or do

Cover the whole body, enable cells to communicate with each other, enable specific communication, enable rapid communication and enable short-term and long-term responses


Why do multicellular organisms need communication systems

To respond when their internal and external environment changes and to coordinate organ function


What is cell signalling

ward: nervous and hormonal systems coordinate the activities of how organisms, this coordination relies on communication at a cellular level, through cell signalling and cell signalling works and occurs through one cell releasing a chemical which then has an affect on another cell known as the target cell

p&m tutor: Communication between cells: electrical signals carried by neurons or chemical signals as hormones. Long-distance Endocrine signalling, paracrine signalling between adjacent cells occurs directly or aided by extracellular fluid. In autocrine signalling, cell releases signals to stimulate its own receptors and triggers a response within itself


What is homoeostasis

ward: The maintenance of a dynamic equilibrium within narrow ranges in the body

p&m tutor: Internal environment is maintained within certain limits around an optimum


What is an ectotherm

p&m : Organism that cannot increase its respiration rate to increase the internal production of heat. Relies on external sources to regulate its body temperature. Response to temperature changes behaviourally for example my Orient body to minimise/maximise sun exposure

ward: All animals except birds and mammals are ectotherm is which basically means they get their heat from the environment and they often find it easier to gain heat than lose it


How do plants coordinate

plants do not have a nervous system, instead they respond to changes in the environment by geotropism, phototropism, stomata, callose defence against pathogens and chemical defences : insect repellent


Define negative and positive feedback

negative — Ward: the reversing of a change in the internal environment. p&m tutor : self regulatory mechanisms return internal environment to optimum when there is a fluctuation

positive— p&m tutor: A fluctuation triggers changes that results in an even greater deviation from the normal level


What are the different types of receptors

Pacinian corpuscle detect changes in pressure

Photo receptors detect changes in light,

chemo receptors detect chemical changes

and Thermo receptors detect temperature changes and peripheral temperature receptor also detects temperature changes


What are receptors and effectors

Receptors: p&m - specialised cells located in sense organs that detect a specific stimulus

effectors : p&m - Usually muscles or glands which enable a physical response to a stimulus


What is an endotherm

p&m : Organism that can regulate its body temperature independently of external sources. Thermo receptors send signals to the hypothalamus, which triggers a physiological or behavioural response

ward: Heat is generated by metabolism/gained from the environment and heat is lost by radiation, evaporation, warm substances leaving the body


Outline behavioural methods endotherms use to regulate their body temperature

panting, hibernation, digging boroughs, pressing against warm surfaces, basking in the Sun


How does the autonomy nervous system enable endotherms to thermal regulate

negative feedback. Peripheral Thermo receptors detect changes in skin temperature. Thermo receptors in hypothalamus detect changes in blood temperature. Hypothalamus sends impulses to effectors in the skin ( vasodilation/constriction, piloerection, sweating) and muscles (shivering)


Explain the role of the skin in Thermo regulation

vasodilation/constriction of arterioles supplying skin capillaries controls heat loss to skin surface. hair erector muscles contract and follicles protrude to trap air for insulation. Evaporation of sweat cools skin surface


Is it better to be an endotherm

Advantage: rate of metabolism not affected, can remain active at all times of the day, do not have to adjust their activities to include temperature regulation.

Disadvantage: large amounts of food need to be eaten to provide fuel, animals with a large surface area to volume ratio for example small birds lose a lot of energy as heat


ppq: Name the corrective homoeostatic mechanisms that works to restore any changes in body temperature to the normal range

negative feedback / thermoregulation


ppq: endotherm is responding different ways to change in environmental temperature. Some of these responses are listed below

J secretion of adrenaline
K sweating
L Shivering
M contraction of erector pili muscles
N Curling up
O Finding shade
P vasoconstriction of arterioles near to skin surface

use the letters to identify:

A) The responses that conserve heat

B) The responses that cool the body

C) A physiological response that generates heat

D) A behavioural not physiological response to a decrease in environmental temperature

A) M , N. AND P : contraction of erector pili muscles, curling up and vasoconstriction of arteriolar near to skin surface

B) K AND O : Sweating and finding shade

C) L shivering ( can also accept J secretion of adrenaline)

D) N curling up


ppq: different endotherm is have evolved different physiological and behavioural adaptations to assist with temperature control. Explain how each of the following adaptations help the animal to control its body temperature

A) Elephants having large, thin ears that they move backwards and forwards when hot

B) Penguins living in cold climates have shunt blood vessels. These link arterioles carry blood towards their feet with small veins that carry blood away from their feet

A) the elephant’s ears have a large surface area ( to lose heat ) so blood flows close to the skin surface to lose the heat and this increases Air movement over the skin to lose heat

B) Blood loses less heat because less blood flows to the feet and warm blood is diverted from arterioles to veins


ppq: State the correct term for communication between cells

Cell signalling


ppq: describe two examples of communication between cells that occur during the life-cycle of D. discoideum

attraction of cells to folic acid from bacteria

attraction of cells to each other by cAMP


ppq: suggest how the plasma membrane of D. discoideum Is adapted for cell communication

contains receptors for folic acid / cAMP


ppq: Explain what is meant by the term homoeostasis

Maintaining relatively stable internal environment within narrow limits even though the environment is changing


ppq: Suggest why affective homoeostasis depends on negative feedback systems rather than positive feedback systems

In a negative feedback system, when a change takes place systems in the body act to return the situation to normal. They inhibit the change; in a positive feedback system, when a change takes place systems in the body at to reinforce the change. In homoeostasis, the body seeks to maintain a dynamic equilibrium; if there is a change, the need is to inhibit it and return things to the original state; this is possible with negative feedback systems but not with positive feedback systems


ppq: Describe how negative feedback is used to control blood glucose concentration

receptors detect a change in blood glucose concentration.

if higher glucose concentration, beta cells in the pancreas releases insulin

which then means an increased uptake of glucose by the effector (liver)

enters through the glucose transport proteins

glucose is then converted to glycogen and an increased use of glucose is used in ATP production


ppq: Describe the way in which an endothermic animals such as a mammal, normally prevents its body temperature from decreasing when the external temperature decreases

peripheral thermoreceptors are stimulated by / detect a decrease in the external temperature

The impulses are sent to the hypothalamus

and therefore vasoconstriction of the arterioles takes place to reduce heat loss

The mammals will prevent heat loss by radiation and will increase its metabolic rate to generate heat energy to increase its temperature as well

also the release of adrenaline and shivering will generate heat and also the piloerectors will generate more heat for the mammal


ppq: State where the core body temperature is monitored

(thermoregulatory centre in) hypothalamus


ppq: name the type of sensory cell in the skin that detect changes in environmental temperature

Peripheral temperature receptor


what do all living things need to maintain a certain limited set of conditions inside their cells

a suitable temperature
a suitable pH
an aqueous environment that keeps the substrates and products in solution
freedom from toxins and excess inhibitors


what is the environmental change



maintaining the internal environment

The composition of the tissue fluid is maintained by the blood.
Blood flows throughout the body and transports substances to
and from the cells. Any wastes or toxins accumulating in the tissue
fluid are likely to enter the blood and be carried away. In order
to prevent their accumulation in the blood they must be removed
from the body by excretion
It is important that the concentrations of waste products and
other substances in the blood are monitored closely. This ensures
that the body does not excrete too much of any useful substance
but removes enough of the waste products to maintain good
health. It also ensures that the cells in the body are supplied with
the substrates they need.


homeostasis textbook

Homeostasis is used in many living organisms to maintain
conditions inside the body, despite changes in external and
internal factors. Aspects maintained by homeostasis may include:
body temperature
blood glucose concentration
, blood salt concentration
water potential of the blood

blood pressure
carbon dioxide concentration.


sensory receptors

A number of specialised structures are required for this pathway
to work:
Sensory receptors such as temperature receptors. These receptors may be on the surface of the body, such as
temperature receptors in the skin. They monitor changes in the external environment. Other receptors are internal to monitor conditions inside the body, for example, temperature receptors in the brain. When one of these receptors detects a change it
will be stimulated to send a message to an effector.
A communication system such as the neuronal system or the
hormonal system. This acts by signalling between cells. It is used to transmit a message from the receptor cells to the effectors via a coordination centre which is usually in the brain. the messages from the receptor to the coordination centre are known as the input. the messages sent to the effectors are known at the output


negative feedback textbook

Negative feedback
In order to maintain a constant internal environment, any change away from optimum conditions must be reversed. In this way, conditions inside the body will be returned to the optimum
This mechanism that brings the conditions back towards the optimum is known as negative feedback

When conditions change, the receptors detect this stimulus and send an input to the coordination centre. The coordination centre sends an output to the effectors and the effectors respond to this output. When the effectors bring about a change that reverses
the initial change in conditions, the system moves closer to the
optimum and the stimulus is reduced.

The receptors detect the
reduction in stimulus and reduce the input to the coordination centre. The output from the coordination centre to the effectors is also reduced, so the effectors reduce their activity. As the system gets closer to the optimum, the response is reduced. optimum condition
change away from optimum


maintaining a constant internal environment textbook

A negative feedback system can maintain a reasonably constant
set of conditions. However, the conditions will never remain
perfectly constant: there will be some variation around the
optimum condition. When a stimulus occurs it may take time to
respond and the response may cause a slight 'overshoot. However,
as long as this variation is not too great, the conditions will remain
acceptable. A thermostatically controlled heated room will never
get too cold or too hot. Similarly, when negative feedback is
applied to living systems, the conditions inside a living organism
will remain within a relatively narrow range. The conditions will
remain 'warm' enough to allow enzymes to continue functioning
efficiently, but 'cool' enough to avoid damage to the body's many
other proteins.


positive feedback textbook

There are, however, some occasions when positive feedback can
be beneficial. Positive feedback is used to stimulate an increase in
a change.
An example is seen at the end of pregnancy to bring about
dilation of the cervix. As the cervix begins to stretch this causes
the posterior pituitary gland to secrete the hormone oxytocin.
Oxytocin increases the uterine contractions which stretch the
cervix more, which causes secretion of more oxytocin. Once the
cervix is fully dilated, the baby can be born. The birth ends the
production of oxytocin.
The activity of neurones also relies on positive feedback.


controlling body temperature textbook

Changes in body temperature can have a dramatic effect upon the activity of cell processes. As temperature rises, molecules have more kinetic energy. They move about more quickly and collide more frequently. This means that essential chemical reactions occur more quickly. However, in cooler conditions the opposite is true and chemical reactions slow down. The structure of proteins can also be affected by changes - especially increases - in body
temperature. Many proteins have a metabolic function; for example, enzymes increase the rate
of biological reactions. Enzymes are globular proteins and have a very specific tertiary structure,
giving them a specific three-dimensional shape. In the case of enzymes, the shape of the active site is complementary to the shape of the substrate and any change in shape will affect their ability to
function normally. If temperature is allowed to increase too much, enzymes change shape and their
function is lost. Some enzymes are very sensitive to temperature change. If the body temperature drops by 10 °C.
the rate of enzyme-controlled reactions falls by half. Many reactions in cells release heat, which can help to maintain the temperature, but if the temperature drops and reactions slow down, less heat is released. This allows the body to cool further. This is a form of positive feedback. As the body cools, the
organism is less and less able to function normally. However, if the temperature rises just a few degrees above the optimum, enzymes may denature and cease to function. The core temperature is the important factor, as all the vital organs are found in the centre of the
body. Peripheral parts of the body may be allowed to increase or decrease in temperature to some
extent without affecting the survival of the organism.


blood vessels response if body is too hot and cold

hot: dilation to direct blood to the extremities so that more heat can be lost

cold: constriction to limit blood flow to the extremities, so that blood is not cooled to much - this can lead to frostbite in extreme conditions


skeletal muscles response if body is too hot and too cold

hot: fewer contractions mean that less heat is released

cold: spontaneous muscle contractions shivering release heat


liver response if body too hot and too cold

hot : less respiration takes place so less heat is released

cold: increased respiration in the liver cells means that more energy from food is converted to heat


advantages to endothermic textbook

Endotherms can:
maintain a fairly constant body temperature whatever the temperature externally

remain active even when external temperatures are low, which
means they can take advantage of prey that may be available or escape from potential predators

inhabit colder parts of the planet.


disadvantages to endotherms textbook

use a significant part of their energy intake to maintain body
temperature in the cold

need more food

use for growth a lower proportion of the energy and nutrients gained from food

may overheat in hot weather.


the role of peripheral temperature receptors textbook

The thermoregulatory centre in the hypothalamus monitors blood
temperature and detects changes in the core body temperature.

However, an early warning that the body temperature may change
could help the hypothalamus to respond more quickly and reduce
variation in the core body temperature. If the extremities start
to cool down or warm up this may eventually affect the core body temperature. Peripheral temperature receptors in the skin monitor the temperature in the extremities. This information is fed to the thermoregulatory centre in the hypothalamus. If the thermoregulatory centre signals to the brain that the external environment is very cold or very hot, the brain can initiate behavioural mechanisms for maintaining the body temperature, such as moving into the shade