biology P2

• what is homeostasis?


  maintaining a stable internal environment
• why do internal conditions in the body have to be regulated?

  for our cells to function properly and for optimal enzyme actions
• what are the two types of automatic control systems?

  nervous and hormonal
• what three components make up most control systems?

  receptors, co-ordination centres and effectors
• what is negative feedback?

  when the level of a certain substance gets too high or low and reverses the effect to bring it back to normal
• what does the nervous system detect?


  detects and reacts to stimuli
• what does the CNS consist of?

  brain and spinal cord
• how is the CNS connected to the body?

  sensory and motor neurones
• what are sensory neurones?


  neurones that carry information as electrical impulses from the receptors to the CNS
• what are motor neurones?

  neurones that carry electrical impulses from the CNS to effectors
• what are the two types of effectors?

  muscles contract or glands secrete hormones
• what are receptors?


  cells that detect changes in stimuli
• what is an example of receptors forming parts of larger organs?

  the retina in the eye is covered in light receptor cells
• how does the CNS coordinate a response?

  stimulus --> receptor --> sensory neurone --> CNS --> motor neurone --> effector --> response
• what is a synapse?


  connection between two neurones, nerve signals are transferred by chemicals which diffuse across the gap
• what are reflexes?


  rapid, automatic responses to stimuli that do not involve the conscious part of the brain to prevent damage
• how is a reflex arc carried out?

  1. stimulus is detected by receptors, impulses are sent along sensory neurone to a relay neurone in the CNS

  2. the impulses reach the synapse between the sensory and relay neurone, chemicals are released to diffuse across and travel along the relay neurone

  3. when impulses reach a synapse connecting the relay and motor neurone, chemicals are released and diffuse along the motor neurone

  4. impulses travel to the effector and muscle is contracted
• how can we carry out a practical for reaction time?

  1. The person being tested should sit with their arm resting on the edge of a table.

  2. Hold a suitable ruler of length (30cm or 1m) vertically between your thumb and forefinger at 0cm. They should let go of the ruler without warning.

  3. The person should try to catch at quickly as possible.

  4. Measure the length at which the person caught the ruler.

  5. Repeat several times to generate a mean distance.

  6. The person should then have a caffeinated drink (300ml), measure the volume and repeat steps 1 -5.
• what control variables should be considered in the reaction time practical?


  - use the same person catching the ruler

  - use the same hand to catch the ruler

  - make sure the person has not had any caffeine prior to the experiment

  - drop the ruler from the same height
• how is measuring reaction time on a computer more precise?

  - it removes the possibility for human error

  - reaction time can be recorded in milliseconds, giving a more accurate measurement

  - the person cannot predict when to respond
• what are hormones?


  chemical messengers that are released in the bloodstream and only affect target organs
• what type of effect do hormones have?

  long lasting effects
• what is the pituitary gland?


  gland in the brain that produces many hormones to regulate body conditions, known as the 'master gland' because the hormones act on other glands, releasing more hormones
• what is the thyroid?

  gland that produces thyroxine that regulates rates of metabolism, heart rate and temperature
• what is the adrenal gland?

  gland just above the kidneys that produces adrenaline that is used to prepare the body for a 'fight or flight' response
• what does the pancreas produce?

  insulin and glucagon that is used to regulate blood glucose levels
• what do the ovaries produce?


  produces oestrogen that is involved in the menstrual cycle
• what does the testes produce?


  produces testosterone which controls puberty and sperm production in males
• how does the body use negative feedback in blood glucose levels are too high?

  1. blood with too much glucose enters the bloodstream

  2. insulin is secreted by the pancreas

  3. insulin makes the liver turn glucose into glycogen

  4. glucoses moves from blood into liver and muscle cells

  5. blood glucose levels are reduced
• how does the body use negative feedback in blood glucose levels are too low?

  1. blood with too little glucose enters the bloodstream

  2. glucagon is secreted by the pancreas

  3. glucagon makes the liver turn glycogen into glucose

  4. glucose is released into the blood by the liver

  5. blood glucose levels are increased
• what is type 1 diabetes?

  - the pancreas produces little to no insulin

  - the high blood glucose levels could kill the patient

  - insulin therapy must be introduced during mealtimes to make sure there is a reduction of glucose

  - patient should restrict eating too much simple carbohydrates and take regular exercise
• what is type 2 diabetes?

  - when a patient becomes resistant to their own insulin

  - this causes their blood glucose levels to rise dangerously

  - being overweight increases chances of getting type 2 as obesity is a risk factor in developing it

  - controlled by eating a carbohydrate-controlled diet and regular exercise
• what occurs during stage 1 of the menstrual cycle?

  lining of the uterus breaks down
• what occurs during stage 2 of the menstrual cycle?

  uterus lining builds up and is ready to receive a fertilised egg
• what occurs during stage 3 of the menstrual cycle?

  an egg is developed and released from ovaries at day 14 (ovulation)
• what is the role of FSH?

  - produced in the pituitary gland

  - causes an egg to mature in the ovaries in a follicle, stimulates ovaries to produce oestrogen
• what is the role of oestrogen?

  - produced in the ovaries

  - causes the lining of the uterus to grow, stimulates the release of LH and inhibits (stops) release of FSH
• what is the role of LH?

  - produced in the pituitary gland

  - stimulates the release of an egg at day 14 (ovulation)
• what is the role of progesterone?

  - produced in the ovaries

  - maintains the lining of the uterus

  - when it falls, the lining breaks down and inhibits release of LH and FSH
• what two hormones can be used to reduce fertility?

  progesterone and oestrogen