biology paper 2

• Homeostasis

  An organism's ability to regulate internal conditions even when external conditions change
• Importance of homeostasis

  • Allows crucial chemical reactions involving enzymes to happen at an Optimum rate
  • Regulates blood glucose concentration, temperature, and water levels
• Nervous system regulation of homeostasis

  1. Receptor detects stimulus

  2. Electrical signal travels to spine through sensory and relay neurons

  3. Signal travels across synapse by neurotransmitter

  4. Signal goes to brain for conscious decision

  5. Signal goes back to effector (muscle) via relay and motor neurons
• Reflex

  Signal bypasses the brain and goes straight through the spine to the effector
• Effectors

  Glands that produce specific chemicals the body needs
• Investigating reaction time


  1. Hold ruler between finger and thumb, drop without warning

  2. Measure distance fallen before caught

  3. Repeat multiple times, take mean average
• Parts of the brain

  • Cerebral cortex - higher level functions
  • Cerebellum - motor skills, movement, balance, coordination
  • Medulla oblongata - controls unconscious actions
• MRI scans

  Safely see activity in the brain
• Accommodation in the eye

  1. For far objects: Ciliary muscles relax, suspensory ligaments tighten, lens becomes thin

  2. For near objects: Ciliary muscles contract, suspensory ligaments slacken, lens becomes fatter
• Pupil

  Hole in the iris that can change size depending on light intensity
• Retina

  Contains rods (detect light intensity) and cones (detect color)
• Thermoregulation

  1. Brain senses blood temperature

  2. Sends nervous and hormonal signals to effectors (sweat glands, blood vessels)

  3. To increase or decrease heat loss
• Endocrine system

  System of glands that produce hormones that travel to effectors via the blood
• Pituitary gland

  Main or master gland that produces hormones in response to stimuli
• Insulin

  Hormone produced by the pancreas that causes glucose to move from blood into cells
• Glucagon

  Hormone produced by the pancreas that causes the liver and muscles to turn glycogen back into glucose
• Type 1 diabetes

  Pancreas can't produce enough insulin
• Type 2 diabetes

  Cells no longer absorb glucose properly
• Urea

  Waste product made from excess proteins broken down by the liver
• Kidney regulation of water balance

  1. Antidiuretic hormone (ADH) from pituitary gland causes kidneys to reabsorb more water

  2. Less ADH causes kidneys to lose more water in urine
• Dialysis

  Process that does the job of the kidneys when they aren't working properly
• Menstrual cycle

  1. FSH causes egg maturation and estrogen production

  2. LH causes egg release

  3. Progesterone maintains uterus lining
• Contraception methods

  • Pills that inhibit FSH
  • Progesterone injections
  • Implants
  • Condoms
  • Diaphragms
  • IUDs
  • Sterilization