Same Notes as "Bio FA4" But the Cards Are AI Generated

• Organisms

  • Must be able to monitor their environment - Both internal and external
  • Can survive internal and external changes through anatomical, physiological, and behavioural adaptations
• Homeostasis


  Maintenance of a constant internal environment, mediated by a feedback systems
• Role of homeostasis

  To ensure that all metabolic reactions in the body can occur at a rate that ensures the survival of the organism
• Irritability


  The ability to detect and respond to changes in the environment. It is a characteristic of all living matter
• Coordination


  Different body parts work together to maintain homeostasis
• Stimulus

  A detectable change in the environment, which is either physically or chemically
• Stimulus response system

  1. Cells detect change

  2. Coordinating centre determines if change required

  3. Response (output) within an effector organ
• Feedback

  Positive feedback - the same response will continue<|>Negative feedback - the response is reversed or negated
• Coordinating systems in multicellular animals

  • Nervous system
  • Hormonal or endocrine system
• Hormones

  Chemical messengers that are produced in very small quantities by cells to regulate the activity of cells and organs
• Ways a hormone may effect a change

  • Autocrine - Bind to receptors in the same cell that produced them
  • Paracrine - Bind to receptors on neighbouring cells
  • Endocrine - Travel long distances through the blood supply to reach the target cells
• Pheromones

  Hormones that act over a distance
• Stimulus-hormone response

  1. Input from external environment relayed to hormone excreting cells via nervous system

  2. Hormone secreting cells respond directly to changes in their immediate internal environment
• Signal transduction pathway

  1. Hormone binds to receptor

  2. Receptor rearranges shape

  3. Change in conformation signals other molecules

  4. Secondary messenger molecules cause changes in chemical pathways
• Down-regulation

  Membrane receptors on cells are removed or recycled, reducing cell's sensitivity to signal
• Up-regulation

  More receptors on cells are synthesised to increase the cell's sensitivity to a weak signal
• Structures specialised to respond to Stimuli

  • Nerve Endings (Dendrites of Nerves)
  • Sense Organs
  • Mechanoreceptors - Respond to touch, pressure, stretch and itch
  • Thermoreceptors - Respond to changes in Temperature
  • Photoreceptor - Respond to light
  • Chemoreceptors - Respond to chemicals
  • Nociceptors - Respond to pain
• Endocrine glands


  Ductless glands that secrete hormones directly into the blood vessels
• Stimuli controlling hormone release

  • Presence of specific metabolite in blood
  • Presence of another hormone in blood
  • Stimulation by autonomic nervous system
• Ways a hormone can influence a target cell

  • Change membrane permeability
  • Influence enzymes in membrane
  • Influence cell organelles
  • Activate genes to produce specific proteins
• Hypothalamus


  Collects information from other parts of brain, monitors hormone levels
• Pituitary gland


  Formed from glandular portion that produces/releases hormones, and neural portion that releases neurohormones from hypothalamus
• Adenohypophysis


  Produces seven hormones which promote growth, pigmentation and the tropic hormones
• Tropic hormones


  Hormones which bring about changes in growth patterns
• Nervous system

  Links receptors that detect stimuli to effectors such as muscles or glands that bring about a response
• Neuron

  Nerve cell with cell body (soma) containing nucleus, and extending fibres (dendrites or axons)
• Types of neuron fibres

  • Axons - long and rarely branched
  • Dendrites - shorter and have many branches
• Dendrites


  Receive input from other neurons
• Axons


  Main pathway for conduction of impulses
• Schwann cells

  Wrapped tightly around axon forming the Myelin sheath
• Myelin sheath

  Layer of cells wrapping the axon, rich in lipids
• Node of Ranvier

  Gap between Schwann cells where the axon is exposed
• Neurons associated with

  • Stimuli - Sensory (afferent) neurons
  • Response - Motor (efferent) neurons
• Interneurons

  Link sensory and motor neurons
• Cell polarisation

  Inside of cell membrane more negatively charged than outside
• Sodium-potassium pump

  1. Sodium ions 'pushed' out through membrane channels against concentration gradient, requiring energy

  2. Potassium ions flow from extracellular fluid into cell, balancing outward movement of sodium ions
• Resting potential

  Net negative charge (-70mV) inside neuron, maintained by sodium-potassium pumps
• Action potential generation

  1. Stimulus depolarises membrane

  2. Sodium channels open, sodium ions move in

  3. Depolarisation spreads along axon

  4. Sodium channels close, potassium channels open, potassium ions move out to restore resting potential
• Refractory period

  Time taken for membrane to restore resting potential after action potential
• Threshold

  Stimulus must be large enough to open enough channels to cause potential change from -70mV to -55mV for action potential to occur