Animal Form and Function Lecture Notes - 2024

Animal form (morphology) and function (physiology) (Ch. 39) Tuna Form and function in Galapagos finches Penguin Seal Jackrabbit  Animal form and function – main concep...

Animal form (morphology) and function (physiology) (Ch. 39) Tuna Form and function in Galapagos finches Penguin Seal Jackrabbit  Animal form and function – main concepts Animal morphology and physiology = adaptations: heritable traits that allow some individuals to survive and reproduce in certain environments better than others (higher fitness) Physical laws (mechanical strength, diffusion, heat exchange) constrain these adaptations and lead to convergent evolution (1st slide) Body size also has a big effect on how animals work (SA:volume) Increasing complexity of large, multicellular animals imposes “design constraints” on body form and function Specialisation of cells/tissues/organs/organ systems Transport systems (e.g. circulatory, digestive system) Control/coordination systems (hormonal, electrical) Allows for maintenance of homeostasis via negative feedback Thermoregulation: an example of homeostasis integrating form (morphology), function (physiology) and behaviour Seemingly bizarre animals all reflect adaptation to environment 1970s 1990s Hallucigenia Anomalocaris Loading… Wiwaxia Burgess Shale fauna 500 MYA Census of Marine Life 2010  All animals exchange materials (nutrients, gases, wastes, heat, etc) with their environment Hydra: a coelenterate Exchange (jellyfishes) Gastrovascular cavity Exchange (a) Single cell 0.15 mm Exchange Small organisms have: -large surface area relative to volume (or mass) 1.5 mm -short diffusion distance between environment and cell(s) (b) Two layers of cells  Remember: surface area:volume ratio! (Fig. 39.9, 39.10) - body size has pervasive effects on how animals function Loading… the rate at which resources can be obtained depends on SA available for diffusion, active transport, etc the rate at which resources are used, and wastes/heat produced, depends on volume (or mass) More complex, multicellular organisms require other solutions for exchange with the environment Specialised branched or folded surfaces increase SA; internalised (protected), Specialised transport systems (e.g. digestive and respiratory system) and specialised fluids (interstitial, blood) link each cell with the environment  Hierarchical organisation of complex animals Cells make us tissues which are organised into functional units (organs) and groups of organs work together (organ systems) Fig. 39.4-39.6 4 main tissue types in animals Connective tissue (Table 39.1) - by far the most variable Loose connective Hard, supporting tissue connective tissue e.g. extracellular e.g. bone Nervous tissue matrix Muscle Dense connective tissue Fluid connective tissue tissue e.g. tendons e.g. blood  The three other tissue types Epithelial tissue Nervous tissue Biological surfaces for exchange (Fig. 39.6) Nerve cells or neurons transmit electrical signals (Fig. 39.4) Muscle tissue Muscle cells (3 types) comprise cells that contract (Fig. 39.5)  Coordination and control of complex body plans: the endocrine system and the nervous system Stimulus from internal or external environment Action potential Growth Rapid Reproduction Synapse behaviours - min, hours, - msec, sec, days, months minutes Response Synapse Response involves changes limited to cells in membrane with specific potential at receptors for specific target each signal cells  Animal hormones belong different “families” – with different structure/function (Fig. 46.4) Protein hormones Monoamines (1 AA) Steroid hormones Thyroid hormones (2 AA) How the hormone interacts with (stimulates) the target/effector cell depends on whether the hormone passes easily through the plasma membrane = lipid solubility  Lipid solubility is key for how hormones function (synthesis, storage, transport, mode of cellular action) Protein hormones Steroid hormones Endocrine Monoamines Thyroid hormones cell, storage/ release Loading… Transport in circulation Target cell Signal Hormone transduction + receptor = transcription factor Cellular response Endocrine systems form networks (axis) for chemical communication and coordination Environment Sensory input Brain Hypothalamus Pituitary Peripheral endocrine glands or target tissues Hypothalamic-pituitary-thyroid axis Neuroendocrine systems are regulated by feedback loops Negative feedback most common - tends to maintain constant or “baseline” levels of hormones (though the absolute regulated level of hormone can vary markedly) Positive feedback rare - important for “explosive” events - oxytocin, prolactin at birth - estradiol at ovulation  Hormonal (neuroendocrine) regulation of female vertebrate reproduction and gonad function Sensory information e.g. day length, food, social factors, physiology Higher brain centers Hypothalamus GnRH GnI H Pituitary FS L H H Gonad Estrogen s Estrogen LIVE s Yolk precursors R Vitellogenin/VLDLy Sexual Receptor- mediated behaviour yolk Hypothalamic-pituitary-gonadal axis uptake Oviduct Gonadal steroids (E2, T) (albumen/she ll)  Hypothalamus and pituitary work together to regulate peripheral endocrine organs Fig. 46.16a Stress Reproduction Growth Short axon neurosecretory cells + Long axon neurosecretory cells specialised (portal) blood system  Neuroendocrine and neural regulation of stress – the hypothalamic-pituitary-adrenal axis “Flight-or-fight” Adrenal medulla Adrenal cortex Short-term response Long-term response Epinephrine Cortisol Norepinephrine (a glucocorticoid)  Neuroendocrine and endocrine control of metamorphosis during Insect development Neuroendocrine - PTTH Protein Glandular - JH See Fig. 46.10 Steroid  The nervous systems forms a networks for electrical signaling (using action potentials) K+ Na+ out in Electrical signal = action potential A rapid, transient change in Fig. 43.1 membrane potential  Neuron structure and organisation Information flow Fig. 43.2 Electrical signal (chemical signal) Action potentials = changes in membrane potentials at a single point on the membrane Action potentials propagate because charge spreads down the membrane (Fig. 43.7) Current spreads in both directions along axon BUT action potentials only move in one direction; because Na channels “behind” the a.p. site are inactive for short period = refractory period  Speed at which action potentials are conducted is proportional to axon diameter 1 mm wide Hodgkin & Huxley Please sir, my heads too small!  Schwann cells and myelin sheath (insulation) allow for saltatory (more rapid) conductance of action potential Schwann cells = glial cells in peripheral NS (PNS) Oligodendrocytes = glial cells in central NS (CNS) Voltage-gated ion channels restricted to nodes of Ranvier Inward current during a.p. is transmitted all the way to the next node (because of Schwann cell insulation) Depolarises membrane at next node to threshold and regenerates a.p.  Neurons meet and transfer information at chemical synapses using neurotransmitters (Fig. 43.11) 1 3 2 4 1 A.p. arriving at synapse depolarises pre-synaptic membrane 2 voltage- gated Ca channels open, Ca influx synaptic 3 vesicles move to and fuse with presynaptic membrane, release neurotransmitter into synaptic cleft 4 neurotransmitter binds to ligand-gated ion channels on post-synaptic membrane and change m.p. Results in change in membrane potential of post-synaptic cell = graded potential (proportional to size of stimulus) The vertebrate nervous system The spinal cord can act independently of the brain in simple nerve circuits = reflexes (automatic responses to certain stimuli, e.g. pain) Functional organisation of vertebrate peripheral nervous system (PNS) Fig. 43.16 Sensory neurons Motor neurons Skeletal muscle Smooth & cardiac muscle  Fig. 43.17 Antagonistic, involuntary control When a nerve meets a muscle – regulation of muscle contraction Neurotx release A.p. propagation Acetylcholine Ca release from sarcoplasmic reticulum (SR) via voltage-gated channels Active transport returns Ca to SR Ca binds to troponin exposing binding sites Actin-myosin interaction = contraction