communications and homeostasis

Question 1

stimulus

Answer 1

triggers a physical or behavioural change

Question 2

response

Answer 2

behaviour caused in living organism which results from an external/internal stimulus

Question 3

cell signalling

Answer 3

process by which a cell responds to substances outside cell

Question 4

homeostasis

Answer 4

maintenance of internal environment around a set point despite environmental changes

Question 5

negative feedback

Answer 5

mechanism that reverses change bringing system back to optimum

Question 6

positive feedback

Answer 6

mechanism that increases change, taking the system further away from optimum

Question 7

ectotherm

Answer 7

animal whose regulation of body temp depends on external sources (cold blooded)

Question 8

endotherm

Answer 8

internally generated heat to maintain body temp (warm blooded)

Question 9

vasodilation

Answer 9

widening of the blood vessels as a result of the relaxation of blood vessels in muscular walls

Question 10

vasoconstriction

Answer 10

constriction/narrowing of blood vessels by small muscles in their walls

Question 11

conduction

Answer 11

the transfer of sound waves, heat, nervous impulses of electricity

Question 12

convection

Answer 12

the process of heat transfer by the bulk movement of molecules within a liquid/gas

Question 13

radiation

Answer 13

energy released in form of particle or electromagnetic waves

Question 14

hypothalamus

Answer 14

acts as body’s smart control coordinating centre

Question 15

thermoregulatory centre

Answer 15

contains hypothalamus in brain, contains receptors sensitive to the temperature of blood

Question 16

thermoreceptors

Answer 16

receptive portion if a sensory neurone, that codes absolute and relative changes in temperature

Question 17

peripheral temp

Answer 17

temperature of the skin (influenced by environment)

peripheral temp receptors detect change in skin temp + alert hypothalamus as warning

Question 18

activity level of ectotherm depends on…

Answer 18

external temp

Question 19

if ectotherms are too cold..

Answer 19

• lie on warm surface
• move around to generate some heat

Question 20

if ectotherms are too hot…

Answer 20

• move underground (burrow)
• decrease SA expose to sun
• increase rate + depth of breathing -> increase water evaporation

Question 21

advantages of ectotherms

Answer 21

• decrease metabolic rate req.
• decrease food req.
• more food converted for growth
• can survive longer without food

Question 22

disadvantages of ectotherms

Answer 22

• more vulnerable to fluctuations environment
• less active at colder temps
• more susceptible to predation if less active
• cannot exploit as many locations

Question 23

why do lizards bask in the sun with their mouths open

Answer 23

gaping allows lizards to dissipate body heat as they don’t sweat so their body stays at opt temp.

Question 24

suggest why aquatic ectotherms have relatively few problems maintaining a stable body temp

Answer 24

• water has high SHC 4.2KJ so stable temp and less fluctuations

Question 25

why does changing the temp present a problem for most mammals

Answer 25

body’s enzymes have weak bonds = change in temp easily disrupts them and can impact metabolism = fatal