Homeostasis

• Homeostasis


  maintenance of a constant internal environment.
• Examples of Homeostasis


  Temp (37 degrees for humans)

  Water Balance

  Blood sugar levels

  Salt balance

  Removal of waste

  pH
• Why is it important to maintain internal conditions?

  Human enzymes have an optimum temp. of 37 ,if they exceed this the enzymes will denature.

  Likewise, pH affects enzymes

  If water balance is not right, the cells may swell up and burst or chrivel up and plasmolyse.

  If glucose levels are low, not enough energy would be released via respiration.
• Thermoregulatory system


  In brain (hypothalamus)
• Cooling mechanism

  Vasoconstriction, sweating, contraction of erector/hair muscles
• What are the two organ systems that help large multicellular organisms communicate and coordinate behavior?

  The nervous system and the endocrine system
• Why do large multicellular organisms like humans need a communication system?

  To coordinate behavior and respond to their surroundings
• What are the main topics to know about the nervous system?

  • Structure of a nerve cell (neuron)
  • Structure of the whole nervous system
  • How a reflex arc works
• What is another name for a nerve cell?

  Neuron
• How are neurons adapted to carry electrical impulses?

  They are long, thin, and have many branch connections
• What is the function of a synapse in neuron communication?

  It allows the transfer of chemicals between nerve cells
• What happens when an electrical impulse reaches the end of a nerve cell?

  It causes the release of chemicals that diffuse to the next nerve cell
• How does the nervous system function as a whole when considering 100 billion neurons?

  It forms a complex network for communication throughout the body
• What are the two main parts of the central nervous system (CNS)?

  The brain and the spinal cord
• What role does the central nervous system play in processing sensory information?

  It decides what actions to take based on sensory input
• What type of neurons carry information from receptors to the central nervous system?

  Sensory neurons
• What do motor neurons do in the nervous system?

  They send impulses from the CNS to effectors like muscles or glands
• What is the function of effectors in the nervous system?

  • Muscles contract
  • Glands release hormones
• What is a reflex arc?

  It is the nerve pathway that underlies unconscious reflexes
• Why are reflexes beneficial for organisms?

  They allow rapid and automatic responses to stimuli
• What is the role of receptor cells in the reflex arc?

  They detect stimuli and initiate the response
• Describe the pathway of a reflex arc when touching a sharp object.

  The sensory neuron carries the impulse to the spinal cord, where it is relayed to a motor neuron that activates an effector
• What happens at synapses during the reflex arc process?

  The electrical signal is converted to a chemical signal to pass between neurons
• What is the purpose of the spinal cord in the nervous system?

  It transfers impulses between the brain and the rest of the body
• What is the process of accommodation in the eye?

  It is a reflex that changes the refractive power of the lens to see both near and distant objects.
• What are the important parts of the eye involved in accommodation?

  The cornea, lens, ciliary muscles, and suspensory ligaments.
• How do the cornea and lens function in the eye?

  Both refract light, with the cornea providing most of the refraction and the lens fine-tuning it.
• What is the fovea in the eye?

  It is the spot on the retina where light must be focused for clear vision.
• How does the lens adjust for nearby objects?

  The lens becomes short and fat to refract light more strongly.
• What happens to the ciliary muscle when focusing on nearby objects?

  The ciliary muscle contracts and moves inwards towards the lens.
• What is the role of the suspensory ligaments in accommodation?

  They attach the lens to the ciliary muscle and can be slackened or tautened to change the lens shape.
• How does the lens adjust for distant objects?

  The lens is stretched out to reduce its curvature and refractive power.
• What is the difference in the ciliary muscle's position when focusing on nearby versus distant objects?

  The ciliary muscle contracts inwards for nearby objects and relaxes for distant objects.
• What condition results from the lens not being able to refract enough light?

  This condition is known as long-sightedness or hyperopia.
• How do glasses help long-sighted individuals?

  They contain convex lenses that provide extra refracting power.
• What happens in a long-sighted eye when trying to focus on a nearby object?

  The image appears blurry because it is focused behind the retina.
• What condition results from the lens refracting too much light?

  This condition is known as short-sightedness or myopia.
• How do glasses help short-sighted individuals?

  They contain concave lenses that refract light outwards to counteract over-refraction.
• What happens in a short-sighted eye when trying to focus on a distant object?

  The image appears blurry because it is focused in front of the retina.
• What is the medical term for long-sightedness?

  Hyperopia