2.5 bio-Response and regulation

• Nervous system


  Made up of the brain and spinal cord (central nervous system, CNS) along with specialised nerves that carry information as impulses into and out of the CNS
• Nerve impulses


  Electrical signals that allow an organism to rapidly react to environmental and internal changes
• Types of neurones


  • Sensory neurone - carries impulses from receptors (sense organs) to the CNS
  • Relay neurone - carries impulses from sensory neurones to motor neurones in the CNS
  • Motor neurone - carries impulses from the CNS to effectors (muscles and glands)
• Synapse


  A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters
• Sense organs


  A group of receptor cells that detect specific stimuli (environmental and internal changes e.g. temperature, sound) and send information to the CNS along neurones
• Reflex


  An automatic, involuntary response to a stimulus by the body that serves as a protective mechanism
• Reflex arc


  1. Stimulus

  2. Receptor

  3. Coordinator

  4. Effector

  5. Response
• The coordinator coordinates information from the receptors and transmits impulses to the effectors
• Reflex arc pathway


  Stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
• Parts of the eye

  • Lens
  • Pupil
  • Iris
  • Cornea
  • Retina
  • Choroid
  • Sclera
  • Optic nerve

  
• Blind spot


  The point at which the optic nerve leaves the eye, where no photoreceptor cells are located
• Homeostasis


  The maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions
• Hormone


  A cell signalling molecule produced by the endocrine glands and released into the blood to travel to a target organ and bind, initiating a response
• Insulin


  Causes liver and muscle cells to increase their uptake of glucose, which is converted into glycogen for storage
• Glucagon

  Causes the breakdown of glycogen to glucose in the liver, which is released into the blood
• Negative feedback


  A corrective mechanism that allows only small fluctuations around a set point
• Types of diabetes


  • Type 1 - Immune system attacks and destroys insulin-producing cells, so the pancreas does not produce enough insulin
  • Type 2 - Person develops insulin resistance (links to obesity)
• Control of body temperature

  1. Temperature increases above 37°C: Vasodilation, Sweating, Erector muscles relax

  2. Temperature decreases below 37°C: Vasoconstriction, Little sweat, Erector muscles contract, Shivering
• Lifestyle choices can affect conditions like obesity, type 2 diabetes, and the effects of drugs and alcohol
• Tropisms


  Growth responses of a plant to stimuli, controlled by the hormone auxin
• Types of tropisms


  • Phototropism - Growth response towards light
  • Gravitropism - Growth response to gravity
• Plant tropisms increase a plant's chance of survival by enabling them to respond to their environment, maximise light absorption, and increase water/mineral uptake and anchorage