B5-Homeostasis and Response

• What is homeostasis?


  Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum condition for function in response to internal and external changes.
• What was homeostasis ensure for the body?


  Homeostasis maintains optimal conditions for enzyme action and all cell functions.
• What does homeostasis control in the human body?

  · Blood glucose concentration

  · Body temperature

  · Water levels
• What are example of automatic control systems in the body?

  -Nervous

  -Hormonal
• What do all control systems include?

  -Cells called receptors which detect the stimulus (changes in the environment)

  -Coordination centres (brain, spinal cord and pancreas) that receive and process information from receptors.

  -Effectors-muscles or glands, which bring about responses which restore optimum levels.
• What are examples of effectors?

  -Muscles which contract and cause movement

  -Glands which release hormones
• What is negative feedback?


  -To counteract change in the body, the mechanism negative feedback gets involved.

  -When the level of something becomes too high or too low, your body uses negative feedback to bring it back to normal.
• What is an example of negative feedback occurring?

  1)Receptor detects a stimulus-level is too high

  2)The coordination centre receives and processes the information, then organising a response.

  3)Effector produces a response, which counteracts the change and restores the optimum level-the level therefore decreasing.
• What happens to the effector after producing responses?

  -The effectors will just carry on producing the responses for as long as they're stimulated by the coordination centre.

  -This might cause the opposite problem but luckily the receptor detects if the level becomes too different and negative feedback starts again.
• What is the nervous system?

  The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
• Where is the CNS in the vertebrates?

  CNS consists of brain + spinal cord only.
• Where is the CNS in mammals?

  CNS is connected to the body by sensory neurons and motor neurons.
• What are sensory neurons?

  Neurons that carry information as electrical impulses-from receptors to CNS.
• What are motor neurons?

  neurons that carry electrical impulses from the CNS to effectors.
• What are relay neurons?

  These connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons.
• What are effectors?

  All your muscles and glands-responds to electrical impulses
• What is the difference between a receptor and an effector?

  Receptors-cells that detect stimuli-different types e.g. taste receptors. Receptor can form parts of larger + complex organs like retina of the eye is covered in light receptor cells.

  
  

  Effectors-respond to nervous impulses and bring about change. Muscles + Glands are known as effectors-they respond in different ways. Muscles contract in response, glands secrete hormones.
• What is the acronym for the process of Stimulus-Receptor-Sensory neuron-Coordination centre-Motor Neuron -Effector -Response?

  Stop

  Rating

  Sex

  Cum

  Must

  Enter

  Rectum?
• What is the synapse?


  The synapse connects neurons

  The connection between two neurons is a synapse
• What happens during the process of synaptic transmission?

  o The nerve signal is transferred by chemicals which diffuse across a gap.

  o These neurons then set off a new electrical signal in next neuron
• What are reflexes?

  -Reflexes are rapid, automatic responses to certain stimuli which do not involve the conscious part the brain

  -They can reduce the chances of being injured.
• What happens when you get a shock?

  If you get a shock, your body releases the hormone adrenaline, automatically-doesn't let you decide.
• What is the reflex arc?


  -The passage of information in a reflex from the receptor to the effector

  -Neurons in reflex arcs go through the spinal cord or an unconscious part of the brain.
• What happens when you hand touched something hot?

  What happens in the synaptic transmission of this?

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

  2)When the impulses reach the synapse, between the sensory neurone and the relay neurone, they trigger chemicals to be released. These impulses chemicals cause impulses to be sent along the relay neurone.

  3)The impulses then travel along the motor neurone to the effector-muscle?

  4)Muscle then contracts and moves your hand away.

  Don't have to think about response so it is quicker
• What is reaction time?


  -Reaction time is the time it takes to respond to a stimulus.

  -It is often less than a second.

  -Can be affected by drugs, age and gender.
• How does caffeine effect someones reaction time?

  Caffeine is a drug-speeds up someone's reaction time.
• Describe the experiment when the effect of caffeine can be measured

  1)Person being tested sits with their arm on edge of table. (Stop them from moving arm up/down)

  2)Hold a ruler vertically between their thumb and forefinger. Make sure that the zero end of the ruler is in level with their thumb/finger.

  Then let go without any warning

  3)Reaction time measure by number on ruler when it is caught. The further down their ruler its caught (the higher number), the slower their reaction time was.
• What are the control variables in this experiment?

  o Use same person to catch the ruler each time

  o That person always uses same hand on the ruler

  o Ruler must always be dropped from the same height

  o Make sure the person being tested on has not had an intake of caffeine (anything that changes their reaction time) before the experiment.
• What does too much caffeine do to a person?

  causes unpleasant side effects
• How can the reaction time also be measured?

  Can also be measured using a computer:

  1)Person being tested on clicks the mouse as soon as they see a stimulus on the screen

  
  

  o Computers-can give a much more precise reaction time because they remove the possibility of a human error.

  o Computer can also measure the time in milliseconds-making it more accurate measurement.

  o Can also remove the possibility of that the person may predict when to respond-catcher may learn to anticipate the drop by reading the testers body language.
• What are hormones?


  -Hormones are chemical molecules released directly into the blood.

  -They also control things in organs and cells which need constant adjustment.

  -Hormones tend to have relatively long-lasting effects.

  -They are carried in the blood to other parts of the body but only affect cells in particular organs.
• Where are hormones created?

  Hormones are produced or secreted by various glands, called endocrine glands. These glands make up your endocrine system.
• What is the pituitary gland and what does it do?

  Pituitary gland-produces many hormones that regulate body conditions.

  It is sometimes called the master gland because these hormones act on other glands, directing them to release hormones that bring about change.
• What is the thyroid and what does it do?

  Thyroid-This produces thyroxine which is involved in regulating things like the rate of metabolism, heart rate and temperature.
• What is the adrenal gland and what does it do?

  Adrenal gland-produces adrenaline which is used to prepare body for a 'fight or flight' response.
• What is the pancreas and what does it do?

  The Pancreas-produces insulin, which is used to regulate the blood glucose level.
• What are the ovaries and what do they do?

  Ovaries (females only)-Produces oestrogen, which is involved in the menstrual cycle.
• What are the testes and what do they do?

  Testes (males only)-Produces testosterone which controls puberty and sperm production in males.
• What are the abilities of nerves?

  -Very FAST action

  -Act for a very short time

  -Act on a very precise area
• What are the abilities of hormones?

  -SLOWER action

  -Act for a long time

  -Act in a more general way.