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18 Cards in this Set
- Front
- Back
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Differences between neuronal and hormonal communication systems |
1.Neuronal Use neurones to carry signal through body across synapse junction Carrier signals around body rapidly Usually coordinate short term response 2. Hormonal Use blood to carry signals around body Endocrine glands release hormones into blood that's carried to target cells Usually coordinate long term response |
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3 features of a good communication system |
1. Covers whole body to ensure every receptor communicates with every effector 2. Enables rapid and specific communication 3. Produces long or short term responses |
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Role of tissue fluid in maintaining a suitable internal environment |
1. Exchange of substances 2. Medium for gases and solutes 3. Removal of metabolic waste |
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Define response |
Change in behaviour and physiology of an organism resulting from a stimulus |
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Standard response pathway |
Stimulus Receptor Communication pathway Effector Response |
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3 specialised structures needed for standard response pathway |
1. Sensory receptor Detect change in stimuli/ external environment and it's stimulated to send this to effector 2. Communication pathway / system Transmit info from receptor( input ) to effector ( output ) via coordination centre Act by cell signalling between cells 3. Effector Liver or muscle cells Bring about a response |
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Define negative feedback |
Mechanism that reverses a change bringing system back to optimum |
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Process of negative feedback |
1. Receptor detects change away from optimum and sends input to coordination centre 2. Coordination centre sends output to effector and effector responds to output 3. Effector brings about a change that brings internal conditions closer to optimum, reducing stimuli 4. Receptor responds to reduction in stimuli by reducing input to coordination centre 5. Output from coordination centre to effector is also reduced and effector reduces it's activity |
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Disadvantage of a negative feedback system |
When stimuli occurs it may take time to respond, response may cause a slight overshoot |
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Define positive feedback |
Mechanism that increases a change taking system further from optimum Usually harmful and less common |
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2 examples where positive feedback is useful |
1. Dilation of cervix 2. Activity of neurones |
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Difference between ectotherm and endotherm |
Ectotherm - organism that relies on external sources of heat to regulate it's body temperature Endotherm - organism that relies on heat from metabolic recations (internal sources) to regulate its body temp |
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Behavioural mechanisms of ectotherms when they're too hot or too cold |
Too cold 1. Expose more surface area to sun 2. Lie move to hot surface 3. Orientate body towards sun Too hot 1. Move away from sun 2. Move underground 3. Expose less surface area to sun |
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Advantages and disadvantages of ectothermy |
Advantages 1. Need less food and can survive longer periods of time without food 2. More energy and nutrients from food used to grow Disadvantages 1. Less active at lower temps 2. Smaller range of habitats where they thrive |
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How do endotherms use negative feedback to maintain body temperature |
Peripheral temperature receptor monitor temperature change and send impulse to thermoregulation centre in the hypothalamus. Nervous and hormonal systems carry signals to skin muscle liver to minimise variation in core body temp. |
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Physiological mechanisms used by ectotherms if body is TOO COLD |
1. Increase rate of exergonic reaction to release more heat 2. Hairs and feathers stand erect to trap air to insulate body 3. Increased respiration in liver cells so more energy from food converted to heat 4. Release of adrenaline/thyroxine - Spontaneous muscle contractions ( shivering ) generate heat 5. Vasocontriction- arterioles near extremities constrict reducing blood flow to skin surface minimising heat loss |
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3 Physiological mechanisms used by endotherms if body is TOO HOT |
1. Sweat glands secrete fluid onto skin surface which evaporates removing heat from blood 2. Vasodilation - arterioles direct blood to skin surface to increase heat loss from blood 3. Some animals pant increasing water evaporation from surfaces of lungs and airways |
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Advantages and disadvantages of endothermy |
Advantages 1. Can inhabit colder parts of the world 2. Can maintain constant body temp. despite external temp. change 3. Can remain active even when temp is low Disadvantages 1. May overheat in hot weather 2. Need more food so more energy used to maintain body temp. |
