Physiology and Behaviour I. Dr Mike Wride School of Natural Sciences Zoology Department

Transcription

1 Physiology and Behaviour I Dr Mike Wride School of Natural Sciences Zoology Department wridem@tcd.ie

2 Two Lectures Physiology and Behaviour I: Physiological mechanisms - hormones and behaviour, the effects of the environment Physiology and Behaviour II: Drive and motivation; Behavioural responses to change in environment:

3 Text Books David McFarland (1999) Animal Behaviour 3rd Ed. Chapters 15 and 16 Chris Barnard (2004) Animal Behaviour: Mechanism, Development, Function and Evolution. Chapters 3.3, 4 and 5 Principles of Animal Behaviour (2009). 2nd Ed. Lee Alan Dugatkin Chapter 3

4 Outline of Lecture Physiological mechanisms - hormones and behaviour Homeostasis Environmental influences on behaviour Conformers and adaptor - thermoregulation, thirst, energy and nutrients Effects of stress on behaviour

5 Physiological Mechanisms The nuts and bolts of behaviour Two major mechanisms Nervous System - organised behaviour - coordiantion/ integration of sensory and motor systems in the organism Hormones - endocrine system affects sensitive tissues at distant sites within the body

6 Hormones and Behaviour Dugatkin p 81, Fig 3.7 endocrine cells and target cells

7 Complex Effects of Hormones Dugatkin, p83, Fig 3.9 Hormones can trigger a new behaviour or modify an existing behaviour or they can prime the organism to respond to a particular environmental situation that might arise in the future

8 Testosterone and Aggression Dugatkin p84, Fig 3.10

9 Effect of Hormones on Behavioural Systems During Development Dugatkin, p 85, Fig 3.11; p86 Fig 3.13

10 in utero position and subsequent adult behaviour Dugatkin p 87, Fig 3.14, 3.15

11 Changing Environments Animals initiate steps to deal with physical demands of changing environments To maintain survival and ability to reproduce Two principles: Tolerance - extent to which extremes can be tolerated (e.g. temp, sailinity) Acclimatization - physiological adaptation to changing environments

12 Homeostasis and Behaviour Homeostasis: maintenance of internal environment of an animal An animal that is able to regulate its internal environment (maintain homeostasis), in the face of fluctuations in the external environment, has greater freedom to exploit a variety of potential habitats Claude Bernard (1859)

13 The Feedback Principle of Homeostasis p265 McFarland; Fig 15.4: feedback principle in a simple thermostatic electric heater

14 2 Types of Animals Conformers: change internal environment to match external environment Regulators: maintain internal environment at a steady state Internal sensors monitor the internal state of the body and initiate appropriate responses to return the body to the steady state when deviations from it occur i.e. a responsive approach...but, some regulation is pro-active

15 Thermoregulation Most animals have optimal body temperature Function most efficiently at this temperature Reduction in temp Body biochemistry/ processes unviable Metabolism slows, muscle activity diminishes, animal becomes torpid Increase in Temp

16 Approaches in response to change in internal body temperature Employ specialised physiological mechanisms Change behaviour both depend on thermoreception - detecting internal and external body temperature

17 Responses of Invertebrates to reduction in temp Some invertebrates (cold blooded - conformers): reduce their activity when external temperature falls Other invertebratess (e.g. common woodlouse, millipede) maintain a body temperature higher than the environment

18 Responses of Vertebrates to Reduction in Temp Warm blooded (endotherms) - shivering, increased food intake (to create more heat) Cold blooded (exotherms)- gain heat from external sources (e.g. sun) May change colour e.g. Desert iguana Dark in am and gets lighter as the day progresses

19 Solutions to Increase in Temp: Overheating Cooling mechanisms required Conduction: direct loss of heat Convection: blood flow to periphery Radiation: proportional to temp difference between internal and external Evaporation: energy associated with water loss

20 Feather Movement in Doves p263 McFarland; Fig 15.1

21 Examples of control of Heat Loss by Changes in Behaviour Fiddler crabs, ground squirrels - and other burrowing animals - make sorties between cool burrows and warm external environment to cool off Panting in birds and mammals - when potentially lethal temperature approaches Namib desert lizard - burrows into the sand when midday temp goes above 40 o C

22 Behaviour of a Dehydrated Camel p264 McFarland; Fig 15.2

23 Behaviour of a Burrowing Lizard p264 McFarland; Fig 15.3 Sand dunes have fluctuating surface temp. Lizard under surface when surface temp too hot or too cold Shaded blocks -active periods of lizard

24 Water Homeostasis Two major mechanisms: Water conservation Thirst

25 Extracellular Thirst: Hypovolaemia p268 McFarland, Fig 15.7

26 Water Conservation Mechanisms ADH - water retention P268 McFarland, Fig 15.8

27 Energy and Nutrients Process of digestion and pattern of eating often related Amount of sodium is very important for maintaining homeostasis Animals have an innate sodium appetite, but can also learn and remember the sources of sodium Salt depleted rats remember and return to a source of sodium in a maze

28 Feeding Behaviour Rats deficient in thiamine show preference for novel food If novel food contains thaimine, rat continues to eat this food Adaptation to rapidly exploit new sources of nutrients Rat can bypass old food in stomach by digesting some of the new food to assess the consequences of ingesting the new food

29 Stress Can be considered to be anything that poses a threat to homeostasis Both internal and external stimuli can cause stress - stressors (e.g. haemorrhage, predator in vicinity) General Adaptation Syndrome - general profile of physiological responses to stress

30 Hormonal Responses to Stress 2 main systems involved: Autonomic nervous system Hypothalamic-pituitaryadrenocortical system (release of adrenocorticotrohic hormone; ACTH)

31 The Hypothalamic- Pituitary- Adrenocortical (HPA) System p274, McFarland; Fig 15.11

32 Affect of ACTH on Adrenal Cortex Synthesis and secretion of corticosteroids Activation of carbohydrate metabolism Regulation of adrenalin production in adrenal medulla Autonomic nervous system and HPA system closely linked Effective response to stressors - coping

33 Stress Hormones and Spatial Memory in Rats Relevance to understanding human learning and memory - understanding learning disabilities in humans Stress hormone - corticosterone interferes with spatial memory skills in rats Use of water maze apparatus and learning trials plus/minus a stressor - electric shock

34 Water Maze and Learning Trials Dugatkin - p 88; Fig 3.16

35 Shock and spatial Memory Dugatkin, p 89; Fig 3.17

36 Summary of Lecture Physiological mechanisms - hormones and behaviour Homeostasis Environmental influences on behaviour Conformers and adaptor - thermoregulation, thirst, energy and nutrients Effects of stress on behaviour

37 Next Lecture Drive and motivation Behavioural responses to change in environment: Biological clocks; Reproductive behaviour; Dormancy: aestivation and hibernation; Migration; Lunar and tidal rhythms; Circadian rhythms and daily routines