Communication and Homeostasis Flashcards
Why do multicellular organisms need communication systems?
To respond when their internal and external environment changes.
To coordinate organ function.
What is cell signalling?
Communication between cells; electrical signals carried by neurons or chemical signals as hormones.
For:
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 Homeostasis?
Where the internal environment is maintained within set limits around an optimum
What is Negative Feedback?
Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
What is Positive Feedback?
A fluctuation triggers changes that results in an even greater deviation from the normal level.
What are receptors?
Specialised cells located in sense organs that detect a specific stimulus.
What are effectors?
Usually muscles or glands which enable a physical response to a stimulus.
What is an ectotherm?
Organism that cannot increase its respiration rate to increase the internal production of heat.
Relies on external sources to regulate its body temperature. Responds to temperature changes behaviorally e.g. may orient body to minimise/ maximize sun exposure.
What is an endotherm?
An organism that can regulate its body temperature independently of external sources. Thermoreceptors send signals to the hypothalamus, which triggers a physiological or behavioural response.
Outline behavioural methods endotherms use to regulate their body temperature:
- Basking in the sun
- Pressing against warm surfaces
- Digging burrows
- Hibernation/ aestivation
- Panting (heat loss as water evaporates from the mouth)
How does the autonomic nervous system enable endotherms to thermoregulate?
Negative Feedback. Peripheral thermoreceptors detect changes in skin temperature. Thermoreceptors in hypothalamus detect changes in blood temperature.
Hypothalamus sends impulses to effectors in skin (vasodilation/constriction, piloerection, sweating) and muscles (shivering).
Explain the role of the skin in thermoregulation
Vasodilation/ constriction of arterioles supplying skin capillaries controls heat loss to the skin surface.
Hair erector muscles contract and follicles protrude to trap air for insulation.
Evaporation of sweat cools skin surface.
