E.2d Ears

eardrum

  • sound waves cause eardrum to vibrate towards and away from middle ear
  • eardrum transmits mechanical vibration of air molecules to middle ear

bones of middle ear

  • ossicles = series of very small bones
    • 1st attached to eardrum
    • 3rd attached to oval window
    • muscles attached to ossicles protect from loud sound
      • by contracting to damp down vibrations
  • amplify sound x20 by acting as levers:
    • reduce sound wave amplitude
    • increase sound wave force
    • oval window’s small size relative to eardrum increases amplification

E.2c: Visual Processing

edge enhancement:

  • occurs within the retina
    • two types of ganglion cell, each stimulated when light falls on a small circular area of retina called the receptive field
    • on-center ganglion cells
      • ganglion is stimulated if light falls on the center of the receptive field
      • but this stimulation is reduced if light also falls on the periphery
    • off-center ganglion cells
      • light falling on the periphery of the receptive field stimulates the ganglion cell
      • if light also fall on the center of the receptive field, stimulation is reduced
    • both types of ganglion cell are therefore more stimulated if the edge of the light/dark is within the receptive field

E.2b Retina

thermoreceptors:

  • membrane receptor proteins respond to temperature,
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. free nerve endings in dermis detect warmth; hypothalamic thermostat detects internal temperature

photoreceptors:

  • photopigments change when activated by specific wavelengths of light,
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. rods and cones in the retina of the eye

E.2a Eyes

1. Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

mechanoreceptors:

  • membrane receptor proteins respond to mechanical deformation,
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. Meissner’s corpuscle (light touch), Pacinian corpuscle (deep pressure), hair cells (hearing, balance), aortic baroreceptor (blood pressure)

chemoreceptors:

  • membrane receptor proteins bind specific molecules
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. olfactory neurons, gustatory cells of taste buds, aortic carotid bodies, hypothalamic glucoreceptors

thermoreceptors:

  • membrane receptor proteins respond to temperature,
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. free nerve endings in dermis detect warmth; hypothalamic thermostat detects internal temperature

photoreceptors:

  • photopigments change when activated by specific wavelengths of light,
  • which results in membrane depolarization
  • leading to action potentials sent to brain,
  • which interprets the sensation,
  • e.g. rods and cones in the retina of the eye

11.2b Muscles & Joints

. Outline the functions of the structures of the human elbow joint named in 11.2.2.

  • Cartilage: reduces friction between bones where they meet
  • Synovial fluid: lubricates joint to reduce friction
  • Joint capsule: seals the joint and holds in the synovial fluid
  • Humerus: upper arm bone: attachment of biceps and triceps
  • Ulna & radius: forearm bones: attachment of biceps and triceps
  • Biceps: attaches from humerus to ulna & radius
  • Triceps: attaches from humerus to ulna
  • Antagonism: biceps and triceps attach across elbow joint; while triceps contracts to to extend arm, biceps relaxes; conversely, while treceps relax and the biceps contract, flexing the arm

11.2a Muscles & Joints

Bones, Ligaments, Tendons, Nerves

The bones provide rigid framework against which muscles attach and against which leverage can be produced, changing the size or direction of forces generated by muscles.Ligaments connect bone to bone, restricting movement at joints and helping to prevent dislocation.Muscles attach to bones via tendons, and when muscles contract, they create the forces that move bones; using leverage, small muscle contractions can produce large bone movements. Tendons attach muscles to bone. Lastly, nerves provide a communication network along which messages can be sent signaling muscles to contract at a precise time and extent, so that movement is coordinated.

6.5a Neurons

resting potential = an electrical potential across a cell membrane when not propagating an impulse

action potential – the localized reversal (depolarization) and then restoration (repolarization) of electrical potential between the inside and outside of a neuron as the impulse passes along it

11.3b: The Kidney

  • proteins:
    • large molecules
    • do not pass from glomerulus into nephron during ultrafiltration
  • glucose:
    • small moleucles
    • pass from glomerulus into nephron during ultrafiltration
    • reabsorped from filtrate back to blood plasma at proximal convoluted tubule
    • by co-transport with sodium ions
    • active transport of sodium ions
    • drives glucose reabsorption by facilitated diffusion
  • urea:
    • small moleucles
    • pass from glomerulus into nephron during ultrafiltration
    • concentrated in medulla
      • as water is reabsorbed
      • but urea is not reabsorbed

11.3a: The Kidney

The process of ultrafiltration 

  • high blood pressure in the glomerulus
    • forces 1300 ml of blood filtrate into kidney nephridia per minute (2000 L/day)
    • as filtrate moves from glomerulus to nephron, it undergoes ultrafiltration
  • ultrafiltration
    • three layers of filtration:
      • fenestrated (porous) endothelial wall of glomerulus
      • basement membrane (extracellular protein) between glomerulus and Bowman’s capsule
      • slits of interdigitating extensions of podocytes making up Bowman’s capsule squamous epithelium
    • any substance small enough to be forced through the capillary wall and between the podocytes by blood pressure (blood serum and smaller dissolved particles) enters the lumen of the nephron tubule
    • larger particles (RBCs, WBCs, platelets, proteins) are excluded from entering nephron, keeping them within the blood vessels
    • ultrafiltration is nonselective, allowing water, urea, glucose, amino acids, salts, vitamins, hormones, minerals, and any other small particles to enter the nephridia

11.1b: Defense Against Infectious Disease

Antibody uses

Production:

  • fusion of cancerous tumor cells + B-lymphocytes = hybridomas
    • use tumor cells because, by being cancerous, they divide without limit
    • use B-lymphocytes which are a clone producing the antibody desired
    • thus, the hybridomas produce specific antibodies in large quantities indefinitely

Diagnosis:

  • HIV infection can be diagnosed through a blood test
  • which assays for the presence of anti-HIV antibodies,
    • antibody produced through monoclonal antibody production is an anti-anti-HIV antibody!

Treatment:

  • monoclonal antibodies can be produced which selectively locate and adhere to cancer cells
  • anti-cancer drugs can be attached to the monoclonal antibodies
    • so that they deliver their effects directly to the targeted cancer cells