NA. 5.1 Communication & Homeostasis Flashcards
Which condition need to be limited for cells to function
- temperature
- PH
- an aqueous enviroment
- Freedom from toxins & excess inhibitors
What is a stimulus?
an environmental change
What is a response?
a change in an organisms behaviour or physiology in reaction to the stimulus
What is cell signalling?
The way in which cells communicate with each other
What are 2 major communication systems?
- Neuronal(consisting of brain CNS and nerves)
* Hormonal (consisting of blood and glands)
Why do multicellular organisms need communication systems?
- To respond when their internal & external environment changes.
- To coordinate organ function.
What are the features of a Good communication system?
- cover the whole body
- enables Rapid communication
- enables Specific communication
- Brings about both short & long term responses
what is the Homeostasis mechanism
Stimulus →Receptor → Communication Pathway →Effector →Response
Define negative and positive feedback
Negative feedback: self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
Positive feedback: a fluctuation triggers changes that results in an even greater deviation from the normal level.
What is an ectotherm?
Relies on external sources to regulate its body temperature. Responds to temperature changes behaviourally
e.g; snakes, lizards, most insects
How might ectotherms control their body temp
• Moving in or out of a sunny area
thus increasing or decreasing surface area exposed to sun
• Lie on a warm surface (if cold)
• Burrowing underground (if hot)
what are some advantages of ectothermy?
• More energy used on growth
• Less food used in respiration
∴they need less food
∴ can survive longer without food
What are some disadvantages of ectothermy?
• they are less active in cool temperatures
∴ more vulnerable to predators
∴ cant take advantage of available food if they’re too cold
Outline behavioural methods endotherms use to regulate their body temperature.
• panting (heat lost as water evaporates from mouth)
• Being more or less active (movement generates
heat in muscles, limbs lose heat )
• Hibernation
• Moving in or out of a sunny area thus increasing or decreasing surface area exposed to sun
Outline Behavioural methods endotherms use to regulate their body temperature.
- panting (heat lost as water evaporates from mouth)
- Being more or less active (movement generates heat in muscles, limbs lose heat )
- Hibernation
- Moving in or out of a sunny area thus increasing or decreasing surface area exposed to sun
State some physiological responses an endotherm might have if its too warm
- Hair and feather lie flat to reduce insulation
- Vasodilation so heat lost through extremities
- sweat, cools body when evaporates( vaporisation)
- Some animals cant sweat so they pant, (similar to sweat but instead evaporation of water on lung surface and airways )
State some physiological responses an endotherm might have if its too cold
- Hair and feather erect to trap air, insulating body
- Vasoconstriction so less heat loss through skin
- spontaneous muscle contractions (shivering)
- less sweat secreted
- less panting
What are some advantages of endothermy?
• they can maintain a fairy constant body temp regardless of external temperature
• Can inhabit colder parts of planet
• They can remain active even when temps lower so
∴ Can escape from predators
∴ Can take advantage of available food if they’re too cold
What are some disadvantages of endothermy?
• More energy used on maintaining body temp
∴ less energy for growth & nutrients
• They need more food
• They may overheat in hot weather
What is the hypothalamus?
The part of the brain that coordinates homeostatic responses
Where is body temperature monitored?
the thermoregulatory centre in the hypothalamus
How are external body temperature changes detected ?
the Peripheral temperature receptors in the skin
