BIPN100 F15
Human Physiol 1 (Kristan) Problem Set #3
Page 1
1. This diagram of a touch-sensitive sensory neuron with a receptive field in the skin of
your index finger.
A. Diagram plausible voltage changes that you might expect to see at the points
numbered 1, 2, and 3 if the skin in the cell's receptive field were touched gently
with a blunt probe.
B. Diagram the voltage changes at those points if the probe pushed harder on the
skin.
C. Diagram the responses at those points if there was a hard touch on another finger.
D. Diagram the responses at those points if a very warm probe was touched gently to
the skin in the receptive field.
E. If the person whose cell this is had eaten too much fugu (puffer fish sushi, which
contains TTX), what effect would a stimulus have at each of the points shown on
the diagram?
2. A. How are pain and touch information separated in the spinal cord? Where do these
kinds of sensory information intersect with motor pathways?
B. What effect on perceived touch and pain in the right hand would you expect if the
right dorsal columns of the cervical spinal cord were severed in C1?
C. What effect on finger strength in the right hand would you expect if the dorsal
columns of the right cervical spinal cord were severed in C1?
D. What effect on perceived touch and pain in the right hand would you expect if the left
dorsal columns were severed in C1?
3. How could spinal cord damage lead to loss of somatosensory perception, but leave
muscle strength unimpaired?
4. Ingesting muscarine, a molecule synthesized by some species of mushrooms, can be
fatal if you eat too many of the mushrooms that make it.
a. Why could it be fatal to eat these mushrooms?
b. What symptoms would you expect to see in a person who mistakenly gathered and
ate mushrooms that contain muscarine?
BIPN100 F15
Human Physiol 1 (Kristan) Problem Set #3
Page 2
5. The movements of breathing are generated and controlled by neurons in several nuclei
located in the brain stem. They are carried out by the diaphragm, a "voluntary" muscle
that has NMJs like frog skeletal muscle and is not driven by autonomic neurons.
Contraction of the heart, on the other hand, is initiated within the heart muscle itself and is
modulated, but not initiated, by neurons of the autonomic nervous system. In each of your
answers below describe the mechanism behind the effect that you predict.
a. When a South American native hits a deer with a blow dart poisoned by curare:
i. what effect will the toxin have on the deer's breathing?
ii. what immediate effect would you expect it to have on the heart rate?
iii. what effect would it have on the deer's ability to run away? Explain your answers.
b. If curare was scarce, but mushrooms were plentiful, and an enterprising South
American native used muscarine instead of curare, predict what direct effect the
muscarine would have on:
i. the animal's breathing?
ii. the heart rate?
iii. the deer's ability to run away?