5.1.1 Communication and homeostasis
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- Created on: 19-09-17 21:08
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- 5.1.1 Communication and homeostasis
- A) the need for communication systems in
multi-cellular organisms
- ll organisms needs to maintain a limited set of conditions
- Organisms respond to changes in internal and external environment.
- External environment: humidity, external temperature, light intensity new or sudden sound
- This is because cellular activities rely on enzymes which require a specific set of conditions to work effectively
- Organs need to coordinate their activity to maintain optimal internal conditions that support survival
- Internal environment: cell pH, water potential, internal temperature, blood glucose
- Organisms respond to changes in internal and external environment.
- ll organisms needs to maintain a limited set of conditions
- B) The communication between cells by cell
signalling
- When cells communicate by signalling, one cell releases a chemicalThis chemical is detected by another cellThe second cell then responds to this signalThere are 2 major systems of communication:
- NEURONAL SYSTEM: network of neurons, quick signals, rapid responses
- HORMONAL SYSTEM: uses blood to transport signals, endocrine organs secrete hormones directly into blood, carried all over the body, only recognised by specific target cells, enables long-term responses to be coordinated, specific target cells have receptors that have a shape that is complementary to the shape of the hormone
- When cells communicate by signalling, one cell releases a chemicalThis chemical is detected by another cellThe second cell then responds to this signalThere are 2 major systems of communication:
- C) The principles of homeostasis
- Homeostasis is the regulation of internal environments independently of external environments (including temperature, blood glucose concentration, blood salt concentration, water content, blood pressure, blood pH
- NEGATIVE FEEDBACK: reversal of a change in the environment to return to the optimum position. Receptor detects the change ? Communication systems inform the effectors ? The effector reacts to reverse the change
- POSITIVE FEEDBACK: response cause change to increase ? destabilizes the system ? usually more harmful ? does not lead to homeostasis ? can be useful in certain situation e.g, childbirth - uterine contractions
- Homeostasis is the regulation of internal environments independently of external environments (including temperature, blood glucose concentration, blood salt concentration, water content, blood pressure, blood pH
- D) the physiological and behavioural responses
involved in temperature control in ectotherms
and endotherms.
- ENDOTHERMS: an organism which can use physiological mechanisms to regulate internal body temperature
independently of the environment.
- Peripheral temperature receptors ? hypothalamus ? effectors in skin and muscles
- Vasodilation/vasoconstriction, spontaneous musclular contractions, sweat glands and hairs in skin
- Behavioural: moving into the shade when too hot, and into the sunlight when too cold, remaining inactive when too hot, and moving about when too cold in order to generate heat from the muscles (unless it is extreme cold, where it is safer to stay still and roll into a ball to reduce surface area), orientating body to increase or decrease the surface area exposed to the sunlight depending on the temperature
- Peripheral temperature receptors ? hypothalamus ? effectors in skin and muscles
- ECTOTHERMS: The body temperature of an ectotherm will fluctuate with changes in external temperature.
- Behavioural responses: To warm up, an ectotherm will normally bask in the sun, or lie on a warm surface, and when too hot will find some shadeto rest in, or alternatively hide in a burrow
- ENDOTHERMS: an organism which can use physiological mechanisms to regulate internal body temperature
independently of the environment.
- A) the need for communication systems in
multi-cellular organisms
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