Unformatted text preview: anging state of the
environment. For example, pain withdrawal response
prevents a burned hand, running away from a snarling
dog avoids attack etc. 3. (a) any from the examples provided (or others).
Answers provided as stimulus (receptor):
Internal stimuli and their receptors: Blood pH/
carbon dioxide level (chemoreceptors in blood Anatomy and Physiology 3. membrane, e.g. nicotine.
Drug can act as an indirect agonist, preventing the breakdown of Ach, thereby causing continued
response in the postsynaptic cell, e.g. therapeutic
drugs used to treat Alzheimer’s disease.
Drug can act as an antagonist, competing for Ach binding sites and reducing or blocking the
response of the postsynaptic cell, e.g. atropine or
vessels); blood pressure (baroreceptors); stretch
(proprioreceptors, e.g. muscle spindle).
(b) Chemoreceptors maintain breathing and
heart rates, baroreceptors maintain blood
pressure, proprioreceptors maintain movement,
photoreceptors maintain vision. The Basis of Sensory Perception (page 84)
1. Linking the size of a sensory response to stimulus
energy allows the incorporation (into the message) of
valuable information about the strength of the stimulus
(i.e. is the stimulus worth responding to or not). 3. 4. Anatomy and Physiology 4. (a) Point of focus is in front of the retina.
(b) Point of focus is behind the retina (image on the
retina is blurred). 5. (a) Myopia: Concave lens diverges the incoming light
rays so that they have to travel further through the
eyeball and are focused directly on the retina.
(b) Hypermetropia: Convex lens converges incoming
light so that the image falls directly on the retina. Sensory receptors convert stimulus energy (e.g.
electromagnetic radiation) into electrochemical energy
(a change in membrane potential). 2. optimized without the need to consider the action
necessary (which would be slow and inefficient). Sensory adaptation allows the nervous system to
cease responding to constant stimuli that do not
change in intensity. This prevents nervous system
overstimulation and allows con...
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- Winter '13