Communication and homeostasis 5.1.1 Flashcards
What two communication systems do we have in our bodies?
-Neuronal and Endocrine
How does cell signalling work in the hormonal system?
-Glands release hormones into the blood where target cells which are the only cells that can recognise these hormones respond.
Why is cell signalling specific?
-The chemicals released have a specific shape complementary to the cell surface receptor on the target cell.
What is the definition of homeostasis?
-Homeostasis: maintenance of an organisms internal environment within self limits, despite changes in internal and external factors
What conditions are maintained by homeostasis?
-Blood glucose and salt concentration
-Blood pressure
-Water potential of the blood
-Body temperature
-Carbon dioxide concentration
What are sensory receptors and effector cells?
-Sensory receptors: monitor changes in internal and external environments
-Effector cells: bring about a response e.g muscle cells
What is negative feedback?
-Receptors detect when a level is too high or low, information is sent via neurones or hormones to effectors to bring level back to optimum
-This only works within certain limits if a change is too big, the effectors might not be able to counteract it e.g. very cold weather
What is positive feedback?
-A change triggers a positive feedback mechanism, this amplifies the change, effectors respond to further increase the level away from the normal level
What are ectotherms and endotherms?
-Ectotherms: not able to control their body temperature so rely on external sources of heat, they use behavioural responses to control body temperature
-Endotherms: use heat generated internally to regulate body temperature, mostly physiological methods but some behavioural
What are behavioural responses that ectotherms use to regulate temperature?
-Lie directly in the sun (basking) to warm up in the morning, once they are active, respiration for muscle contraction generates some extra heat
-They usually shelter to escape extreme temperatures, burrows provide shade at day and prevent heat loss at night
What are the advantages of not controlling internal body temperature physiologically?
-Less energy needed from food as more of the energy gained from food can be used for growth and biomass
-Therefore can survive longer periods without food
How do endotherms monitor body temperature?
-Using receptors, peripheral receptors monitor external temperatures and the hypothalamus responds to action potentials from receptors within the body
-Peripheral receptors provide an early warning to a temperature change
How does thermoregulation reduce body temperature?
-Thermoreceptors detect increase in temperature and initiate an action potential along the sensory neurone to the hypothalamus, the hypothalamus sends an action potential back to the skin via the motor neurone
-This causes glands to secrete sweat onto the skins surface which evaporates carrying heat away from the surface
-Vasodilation: arterioles dilate causing more blood to flow through capillaries, more heat is then lost via radiation
How does thermoregulation increase body temperature?
-Hypothalamus detects drop in core temperature and sends an action potential to the erector pili muscles causing them to contract and the hairs stand. This traps a layer of air which acts as an insulator limiting heat loss
-Vasoconstriction: occurs in arterioles supplying the capillaries near the surface, less blood flow means less heat loss to the environment.
How do the skeletal muscles and liver respond to maintain body temperature?
-Skeletal muscles contract to release heat
-Liver can increase or decrease rate of respiration to increase or decrease energy from food that is converted to heat
How does panting reduce body temperature?
-Increases evaporation of water from lungs and airways (carrying heat away)
What are the advantages of controlling body temperature physiologically
-Can maintain relatively constant internal body temperature despite external temperature
-Can maintain active when external temperatures are low so can inhabit cold parts of the planet
What are the disadvantages of controlling body temperature physiologically
-Requires lots of energy to maintain body temperature
-Need to eat more food as lower proportion of food is available for growth
