Chapter 06: Detecting & Regulating Change

Question 1

• What are receptors?
• What is osmotic pressure?
• What are osmoreceptors?
• What are chemoreceptors
• Give 2 external chemoreceptors examples
• Describe some examples of internal chemoreceptors.
• What are touch receptors.
• What 3 places are touch receptors found?
• What does it mean when we say that receptors adapt to a stimulus?
• What are pain receptors?
• Where are pain receptors found?

Answer 1

• A structure that detects a stimulus
• Concentration of substances dissolved in the water of the blood plasma.
• Receptors that respond to water concentration in the blood found in hypothalamus.
• Receptors sensitive to particular chemicals.
• In the nose, creating sensitivity to odours, in the mouth creating sensitivity to tastes.
• Receptors in the blood vessels sensitive to the pH of the blood and to the concentrations of oxygen and carbon dioxide.
• Receptors sensitive to touch.
• They are found in 3 places. 1st, close to the surface of the skin that are very sensitive to touches. 2nd, base of hair follicles that are sensitive to touches that bend the hair. 3rd, deeper in the skin that are sensitive to pressure and vibrations.
• They adapt to a stimulus when they no longer respond to the stimulus eg when first putting on a tee, we’re aware of it touching the skin, but that sensation disappears very quickly.
• Receptors sensitive to damage to the tissues.
• Heavily concentrated in the skin, and mucous membranes. They occur in most organs, but not in the brain.

Question 2

• Where are thermoreceptors found?
• How is pain good?
• How are pain receptors different to touch receptors?
• What is a reflex?
• What are the 4 characteristics of a reflex?
• Define spinal reflex
• Define spinal reflex arc
• What are the 5 steps of a reflex arc?

Answer 2

• Skin where they detect changes in the environmental temp and hypothalamus where they detect the temp of the blood flowing through the brain.
• Warning of damage occurring so action is taken to minimise damage.
• Pain receptors doesn’t adapt so that pain continues as long as the stimulus is present.
• A rapid, automatic response to a change in the external or internal environment.
• Triggered by a stimulus, involuntary, rapid as only small number of neurones are involved and are stereotyped as the response to a stimulus is always the same.
• A reflex carried out by spinal cord without involvement of brain.
• The pathway travelled by a nerve impulse from receptor to effector during a spinal reflex.
  1. Receptor reacts to change in the internal/external environment by initiating a nerve impulse in the sensory neurone.
  2. Sensory neurone carries impulses from the receptor to the CNS.
  3. There is at least 1 synapse to a motor neurone or to interneurones, which direct the impulse to the motor neurone.
  4. Motor neurone carries the nerve impulse to an effector.
  5. Effector receives impulse and carries out the appropriate response.

Question 3

• Define acquired reflexes.
• What 6 internal environmental factors needs to regulated?
• How is the steady state (homeostasis) achieved?
• What do the nervous and endocrine systems have to do with homeostasis?
• What are tolerance limits?
• What is a feedback system?
• Explain the idea of negative feedback with the situation of muscles using up glucose during exercise.

Answer 3

• A response to a stimulus that has been learned through practice.
• Core temp, pH of body fluids, blood glucose levels, concentration of O2 and CO2 in the blood, blood pressure and concentration of metabolic wastes.
• Process of dynamic equilibrium in which input and output of materials and energy are balanced.
• They’re the main sensory and controlling systems which controls homeostasis through negative feedback systems.
• Limits of body which causes malfunctions if goes beyond.
• A situation where the response to a stimulus changes the original stimulus.
• During exercise, muscles uses up glucose to release energy for muscle contraction. The muscles absorb glucose from blood so blood glucose level falls. This is the stimulus. The liver responds by breaking down glycogen into glucose into the blood. The response causes the blood glucose level to rise, which is opposite of the stimulus.

Question 4

• What is a model?
• What is a set point?
• What is positive feedback?
• Give an example of positive feedback.
• Name 3 protective/birth reflexes.
• Name 3 learnt reflexes.

Answer 4

• A simplified representation of something complex.
• In a feedback system, the level at which a variable is to be maintained.
• Feedback that reinforces the original stimulus.
• Childbirth must be completed fast to avoid stress and injury to the mother and baby. Labour initiates from oxytocin secretions from the P.L, causing contractions of the uterus, pushing the baby’s head against the cervix. Stimulation of the cervix causes the pituitary to secrete more oxytocin, increasing contraction strength.
• Secretion of saliva in response to sight, removing hand from danger, smell of food.
• Suckling, chewing and following movement with eyes.

Question 5

• Sometimes positive feedback can be harmful. Give an example.
• Define dynamic equilibrium
• List 3 protective reflexes
• When you withdraw your hand from a painful stimulus, the response occurs before you are consciously aware that you have hurt yourself. Explain how this is possible.

Answer 5

• A high fever: A small rise in body temperature can be beneficial in fighting infection but if the temp rises above 42°C, a dangerous positive feedback loop can occur. The raised body temp causes a higher metabolic rate, producing more heat, which raises the temp further. This increases the metabolic rate and so the temp spirals upwards.
• The fluctuation of internal environmental factors around the normal level
• Blinking to protect the eye, sneezing to remove irritate from nasal cavity and vomiting to remove irritating substances from stomach.
• This is an a example of a reflex action. When the nerve impulse enter the spinal cord from pain receptors via a sensory neurone in the hand, they are passed to motor neurones in the same level of the spinal cord. The motor neurone carry the impulse to the arm muscles causing contraction and withdrawal of the hand. At the same time, messages are transmitted to the brain so that the person is consciously aware of what is happening. However the pathways to the brain involve more synapses than those of the simple reflex so is slower.

Question 6

• Why does the body have receptors?

- Where are pain receptors located?

Answer 6

• To monitor changes in the internal or external environment of the body.
• Located in the epidermis. They are the closest receptors to the surface of the skin to detect pain asap.