Topic 5 - Homeostasis and response

• Homeostasis = the regulation of the conditions inside your body to maintain a stable internal environment when the internal and external conditions change.
• Name 3 internal body condition which are under homeostatic control?

  Body temperature, blood glucose and water content
• What are the 3 things that all control systems include?

  Receptors - detects stimuli

  Coordination centres - receive and process information from the receptors.

  Effectors - bring about responses and counteract a change
• Stimuli = changes in the environment
• What does the nervous system allow a human to do?


  it enables humans to react to their surroundings and to coordinate their behaviour
• How is information passed along neurones?

  As electrical impulses
• What is the CNS comprised of?

  The CNS (Central Nervous System) is comprised of the brain and spinal cord.
• what is the job of the CNS?

  CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones. It also send messages from certain parts of your body to your brain, then from your brain to your body to tell your body what to do.
• State effectors and their actions - Muscles (contract) / Gland – secrete (hormones)
• What's a synapse?


  It's the gap between the neurones, a chemical diffuses across it and attaches to the next neurone and causes electrical impulses to start.
• Describe the stages in a reflex arc when you touch a hot pan handle (need to give specific details)

  -Stimulus of hot handle is detected by temperature receptor in skin of hand

  -Electrical/nervous impulse travels down sensory neurone to the relay in spinal cord (CNS)

  -Message is transferred by chemical across synapse (attaches onto next neurone)

  -Relay neurone transfers electrical impulse to motor neurone (across synapse)

  -Motor neurone causes muscle in arm to contract, and move hand away
• What is a reflex action? An automatic and rapid response to a stimulus.
• Describe how to do the ruler-drop test:

  -Student 1 hold a ruler just above the open hand /finger and thumb of student 2

  -Student 1 drop the ruler (no signal can be given)

  -Student 2 catches ruler

  -Record where the ruler is caught/ measure above the thumb on the ruler
• What is the brain?


  An organ which controls the complex behaviour made of billions of interconnecting neurones.
• Label parts of the brain and their function:

  -Cerebral Cortex = Co-ordinates consciousness, intelligence, memory and language

  -Cerebellum = Coordinates muscular activity and balance

  -Medulla = Coordinates unconscious activities such as controlling heartbea
• How can the brain be investigated?

  • electric stimulation
  • MRI scans
  • studying patients with brain damage
• It's difficult to treat brain disorders because the brain is so delicate and complex
• The eye is sensitive to light intensity and colour
• Retina: it's towards the back of the eye

  • Contains light receptors
  • Sensitive to intensity and colour
• Optic nerve:

  • Transmits electrical/nervous impulses from the retina to the brain
• Sclera: around the outside of the eye

  • Tough outer layer to protect the eye
• Cornea:

  • Transparent outer layer right at the front of the eye
  • Refracts light to focus an image
• Iris:

  • Contains muscles that allow it to control the diameter of the pupil
  • Allows control over the amount of light entering the eye
  • Bright light: Pupil smaller diameter, circular muscle in iris contracts (radial muscle relaxes)
  • Dim light: Pupil larger diameter, radial muscle in iris contracts (circular muscle relaxes)
• Ciliary muscles: this controls the shape of the eye

  • Contract/relax to loosen/tighten the suspensory ligaments (involved in accommodation)
• Suspensory ligaments: controls the shape of the eye

  • Loosen/tighten to change the shape of the lens
  • Refract light and focus light on near/distant objects (involved in accommodation)
• Lens:

  • Changes thickness to focus light on the retina
• Accommodation = the process of changing the shape of the lens to focus on near or distant objects
• How do the eyes focus on a near object?

  The ciliary muscles contract so they have a smaller diameter so the suspensory ligaments loosen / slacken so lens thickens and then lens becomes more curved / rounded so light is refracted more so light rays / image focused on retina
• How do the eyes focus on a far object?

  the ciliary muscles relax so they have a larger diameter so suspensory ligaments are pulled tight (more tension on lens) so the lens is then pulled thin or lens less curved/rounded so lens is less convergent/ light refracted less so light rays / image focused on retina
• Myopia - short sightedness

  Hyperopia - long sightedness

  • can be treated with lenses on glasses which refract the light rays so they don't focus on the retina
• Which area of the brain is responsible for regulating body temperature, and describe the two ways it detects changes in the body temperature?

  • The thermoregulatory centre: Receptors to detect the temperature of the blood as it flows through
  • Skin contains receptors which detect temperature and send nerve impulses to the brain
• Describe the mechanisms that work if the body temperature is too high?

  • Blood vessels supplying the surface of the skin dilate (vasodilation)
  • More blood flows to the skin (skin gets hot and red)
  • More heat transferred from the skin (by radiation)
  • Sweat produce from sweat glands
  • Water in sweat evaporates (as it heats up)
  • Transferring heat from the skin, so it causes cooling
  • hairs lie flat
• Describe the mechanisms that work if the body temperature is too low?

  • Blood vessels supplying the surface of the skin constrict/narrow (vasoconstriction)
  • Less blood flows to the skin (skin gets cold and pale)
  • Less heat transferred from the skin (by radiation)
  • Shivering
  • Skeletal muscles contract
  • More respiration, releases heat energy to transfer to blood
  • Water in sweat evaporates (as it heats up)
  • Transferring heat from the skin, so it causes cooling
  • hairs stand on end
• Hormone = a chemical messenger that is produced in one part of the body and travels to another part of the body. It's secreted by a gland and acts on a target organ and it travels in the bloodstream.
• Why is the pituitary gland referred to as the “master gland”?


  Secretes several hormones into the blood, in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects
• the effects of the hormone system are more slower and longer lasting than the nervous system
• The pancreas is the main organ which is responsible for controlling blood glucose levels.
• Which hormone is released when blood glucose concentration is too high, and what are its effects?

  Insulin is secreted by the pancreas, which then allows glucose to enter the cells (insulin causes the conversion of glucose to glycogen in liver/muscles).

  The blood glucose concentration returns back to normal.
• Which hormone is released when blood glucose is too low, and what are its effects??

  • when this is detected by the pancreas Glucogen is released from the pancreas which causes glycogen (in muscles/liver) to be converted into glucose
  • Glucose is then released into the bloodstream to raise blood glucose concentration back to normal
• How is information carried from the receptor to the CNS?

  The receptor detects the stimuli, then the information passes along the neurones and across a synapse where the electrical impulses start.