Communication & Homeostasis

module 5

why are communication & co-ordination essential in organisms?

communication & co-ordination are essential so that different parts of an organism can work together

define external environment

where an organism lives

define internal environment

where individual cells live - this is called tissue fluid

what is any change in the external or internal environment called?

stimulus

all cellular activities involve….

enzymes

enzymes work best in a narrow set of conditions, called…?

optimum conditions

what do extremes of temeperatures and pH cause to an enzyme?

the enzyme will denature

what does “denature” mean?

permanent change to tertiary structure of a protein (all enzymes are globular proteins)

what is essential to allow substances and products to stay in solution?

water

fill in the gap.

The presence of i____ may also seriously affect enzyme action

inhibitors

for enzymes to work efficiently, the tissue fluid that surrounds all cells must be kept….?

stable

what is the composition of tissue fluid maintained by?

blood

blood transports substances _______ cells

to and from

what happens to waste accumulated in the tissue fluid?

diffuse into bloodstream and eventually excreted from the body via the bloodstream

what are 2 examples of excreted wastes?

CO2 excreted by the lungs

urea excreted by the kidneys

explain the 5 things a good communication system will do

• cover the whole organism - so actions of all cells & tissues in body can be coordinated

• allow cells to communicate with each other (cell signalling)

• allow specific communication - so that only the cells that need to respond to the signal with respond to the signal

• allow rapid communication - to enable response to rapid changes in the environment

• allow both short-term and long-term responses - so that the responses can be suited to the environment change (a short-term change in the environment only requires a short-term response, but other changes may require a long-term response

what is communication between cells called?

cell signalling

what are the 2 steps of cell signalling?

1. a cell releases a chemical (signal)

2. another cell detects the chemical and responds to the signal

what does the neuronal system consist of?

a network of many millions of interconnected neurones (nerve cells)

where does communication between neurones take place?

across synapses

what is a synapse?

a tiny gap (20nm) between neurones

how is a synapse an example of cell-signalling between adjacent cells?

signals pass rapidly in one direction allowing quick responses to be made to stimuli

how does the hormonal system transport hormones (signals) all around the body?

via the bloodstream

where are hormones made?

special endocrine glands

fill in the gaps.

Hormones will only affect t_____ cells in the body

target

hormones carry signals that co-ordinate… what?

long-term responses (e.g. puberty)

hormones carry signals that co-ordinate long-term responses (e.g. puberty). What is this an example of?

cell-signalling between distant cells

State 4 examples of a stimulus and a corresponding response in animals. Do they use the hormonal or neuronal system for communication, why?

• heat - sweat - long-term response - hormonal, must continue until cool

• cold - shiver - long-term response - hormonal, must continue until warm

• flame - flinch - neuronal - rapid

• blinking when something comes too close - neuronal - rapid

describe 2 examples of a stimulus and response in plants

bending towards light & stomata opening when light

list the organs that are associated with excretion

• lungs

• liver

• kidneys

• skin

list the organs that are associated with maintaining the internal environment of a mammal, stating what role each organ plays

• skin - body temp control

• pancreas - releases hormones

• lungs - excretion of CO2

what is homeostasis?

maintenance of a constant internal environment despite changes in the external & internal environments

what are examples of conditions that need to be controlled?

• body temp

• water potential of blood

• blood glucose conc

• blood pressure

• blood salt conc

• CO2 conc

what is a receptor?

a cell that detects a stimulus

what is an effector?

a tissue or organ (e.g. muscle/gland) that carries out an action in response to a stimulus

what is a change in optimum conditions detected by?

receptors

what is activated to restore optimum conditions? what is this called?

processes to reverse the changes of optimum conditions - called negative feedback

what is an example of a homestatic process that uses negative feedback?

control of body temp in mammals

look at diagram in notes

what does positive feedback do?

increases any change detected by the receptors

why is it good that positive feedback is less common than negative feedback?

(positive feedback) tends to be harmful and doesn’t always result in homeostasis

what are 2 examples of positive feedback?

• contraction of the uterus during labour (this isn’t harmful, but helpful)

• blood clotting

Fill in the gaps.

contraction of the uterus

during labour, a hormone called ___1___ is released that intensifies and speeds up contractions.

the increase in contractions, causes ____2___ ___3____ to be released and the cycle goes on until the baby is born (the birth ends the release of ____4____ and ends the ____5____ feedback mechanism

1. oxytocin

2. more

3. oxytocin

4. oxytocin

5. positive

look at diagram on notes

fill in the gaps,

blood clotting

once a vessel is damaged, ___1___ start to cling to the injured site and release ___2___ that attract more ___3___. The ____4___ continue to pile up and release ____5____ until a clot is formed

1. platelets

2. chemicals

3. platelets

4. platelets

5. chemical

look at diagram on notes

what does “ecto” and “therm” mean?

ecto = on the outside

therm = heat

what are ectotherms?

animals that gain heat from outside their bodies

what are the advantages of ectotherms?

• less food needed for respiration (release of energy from food)

• survive for longer periods without needing to eat

• faster growth due to a greater proportion of energy released from food is used in growth

what are the disadvantages of ectotherms?

• less active in cooler temperatures - so need to “warm up” in the morning before moving. Greater risk of being eaten by predators

• must have sufficient energy reserves to last through the winter months bc the external temp never gets high enough for them to become active

what do ectotherms rely on for regulating temperatures?

increasing the exchange of heat with their external environment

list the physiological adaptations of ectotherms, and explain how they help regulate temperature

• alter body shape - exposes more or less surface area to sun (e.g. horned lizards)

• increasing breathing movements - evaporates more water (e.g. locusts)

list the behavioural adaptations of ectotherms, and explain how they help regulate temperature

• expose body to sun - enables more heat to be absorbed (e.g. snakes)

• orientate body towards sun - exposes larger SA for more heat absorption (e.g. locusts)

• orientate body away from sun - exposes lower SA so that less heat is absorbed (e.g. locusts)

• hid in burrow - reduces heat absorption by keeping out of the sun (e.g. lizards)

what does “endo” mean?

inside

what is an endotherm?

an animal that maintains its own body temp

are all mammals and birds endotherms or exotherms?

endotherms

how do endotherms maintain their own body temp?

through the gain and loss of heat

list the ways endotherms gain heat (input)

• exergonic chemical reactions release energy as heat

• absorbing infrared radiation from the sun or a fire

• conduction from warmer surfaces

list the ways endotherms lose heat (output)

• conduction and convection of sweating

• infrared radiation from the body

• conduction to colder surfaces

what are the advantages of endotherms?

• no matter what the external temperature is, the core body temperature stays fairly constant

• can be active at any part of the day, and any time of the year

• can live in really cold places

what are the disadvantages of endotherms?

• if external temp is cold, then a lot of the energy intake is used to maintain core body temp

• more food needed to stay alive

• less of the energy released from food is used for growth (more food is needed so that growth can take place)

fill in the gap.

The _________ contains receptors involved in temp regulation

hypothalamus

The hypothalamus contains receptors involved in temp regulation. What is this part of the hypothalamus called?

the thermoregulatory centre

fill in the gaps.

The hypothalamus is constantly monitoring the blood that flows through it. Our core body temperature is maintained at approximately ___1__˚C. The ____2___ also contains temperature receptors. These receptors are called _______3________ receptors because they are ‘around the outside’ of the body. These receptors act as an __________________4_______________ to let the hypothalamus know if the core temperature is likely to change. The hypothalamus sends electrical impulses to some _______5_______ and to the ____6____. Electrical impulses travel along nerve cells called _______________7_________________. 

1. 37

2. skin

3. peripheral

4. early warning system

5. muscles

6. skin

7. motor neurones

what response do arterioles in the skin bring about when body temp is high and when low?

• Increased blood flow in capillaries near the surface of the skin (vasodilation). - hot

• Decreased blood flow in capillaries near the surface of the skin (vasoconstriction). - cold

what response do hairs on the skin bring about when body temp is high and when low?

• Hairs lie flat. - hot

• Hairs are raised. - cold

what response do sweat glands in the skin bring about when body temp is high and when low?

• Secrete more sweat onto the skin. - cold

• Secrete less sweat onto the skin - hot

what response do skeletal muscles bring about when body temp is high and when low?

• No spontaneous contractions - hot

• Spontaneous contractions (shivering) - cold

what response do liver cells bring about when body temp is high and when low?

• Rate of metabolism is reduced - hot

• Rate of metabolism is increased - cold

what response do the lungs, mouth, and nose bring about when body temp is high and when low?

• Panting - hot

• No panting - cold

explain how arterioles in the skin increasing blood flow in capillaries near the surface of the skin (vasodilation) when body temp is high, works to maintain core body temp

vasodilation of arterioles & precapillary sphinctres directs blood to skin surface so more heat can be radiated away from the blood

explain how arterioles in the skin decreasing blood flow in capillaries near the surface of the skin (vasoconstriction) when body temp is low, works to maintain core body temp

vasoconstriction of arterioles & precapillary sphinctres directs blood away from skin surface so less heat is lost

explain how hairs on the skin lying flat when body temp is high, works to maintain core body temp

hairs lie flat to reduce insulation & allow greater heat loss

explain how hairs on the skin raising/stand up when body temp is low, works to maintain core body temp

hairs stand up to trap air, insulating the body

explain how sweat glands in the skin secreting more sweat onto the skin when body temp is high, works to maintain core body temp

more sweat as this evaporates it uses heat from the blood as the latent heat of vaporisation (water evaporates)

explain how sweat glands in the skin secreting less sweat onto the skin when body temp is low, works to maintain core body temp

less sweat so less evaporation means less heat is lost

explain how skeletal muscles not spontaneously contracting when the body is hot, works to maintain core body temp

fewer contractions so less heat is released

explain how skeletal muscles spontaneously contracting (shivering) when the body is cold, works to maintain core body temp

shivering releases heat

explain how liver cells reducing the rate of metabolism when the body is hot, work to maintain core body temp

less respiration takes place, so less heat is released

explain how liver cells increasing the rate of metabolism when the body is cold, work to maintain core body temp

increasing respiration so more energy from food is converted to heat

explain how the lungs, mouth, and nose panting when the body is hot, works to maintain core body temp

panting increases evaporation of water from lungs and airways surface. evaporation uses heat from blood as the latent heat of vaporisation

explain how the lungs, mouth, and nose not panting when the body is cold, works to maintain core body temp

less panting so less heat is lost

what is the latent heat of vaporisation?

minimum energy required to convert a liquid to a gas

why is water a liquid at room temp?

has a high latent heat of vaporisation due to several Hydrogen bonds

what behaviours do endotherms display when they are too cold?

• drink something hot

• lie in the sun

• orientate body towards sun to increase SA exposed to sun

• wet skin to use evaporation to cool body

what behaviours do endotherms display when they are too hot?

• drink something cold

• hide away from the sun in the shade

• orientate body away from sun to decrease SA exposed to sun

• remain dry