Solved by a verified expert:5/16/16
The Circle of Willis (cerebral arterial circle) is a vascular
structure that allows confluence between the blood arriving from the left and
right sides of the body through several arteries. After you have explored the
anatomy of this structure, answer the following questions.
How does the organization of this structure
help to perform its function(s)?
In light of this function, what is the main
potential advantage for the brain for such an organization?
According to A&P Revealed, the Circle is
complete in only about 20% of individuals. Why might even an incompletecircle
be better than no connection between sides at all in performing its main
An incomplete circle might be better than no
connection at all because
Finally, undertakers find that the Circle of
Willis complicates their task of embalming the body of a deceased person. How
might this structure affect the ability to infuse the brain with embalming
fluid, replacing all the blood in the vessels of the brain?
Think of a revolving door or a traffic circle.
For the following description, identify FOUR (4) structures and
pathways in the nervous system that are responsible for the experiences
Specify whether each pathway is somesthetic or autonomic; and
whether the response is reflexive or voluntary, cognitive or subconscious.
As they proceeded down the slope into the ghat, the rocks were
slick and greasy. Once, he lost his footing as the moist soil gave way. His
arms swung out wildly as he arched his back and pumped his legs to regain his
balance—the left leg flexing to lower the center of gravity and the right leg
extending straight out into space. When he was fully upright, he sat against a
rock to “catch his breath”.
When his work was done, he was grateful to be climbing back into
the sunlight. Only a few feet to go. His right leg was flexed at the knee and
hip, and his left fully extended, Just as he transferred the weight from his
left to his right foot, it happened. The soil gave way again under his right
He jackknifed his body hard at the waist to change his center of
gravity and reached out wildly with his right hand, grabbing onto a small bush
just above his shoulder. He was already tumbling down the side of the gully
before he realized the pain caused by the four 2-inch long thorns that skewered
his right palm. He hadn’t even known he was injured or consciously decided to
let go of the bush. He only realized these things when he landed at the bottom
of the gully with a loud thump.
Now let us reconsider the case of Will Thatcher.
Using the material in muscle and nerve parts of the APR program
— and combining it with other information from the course materials…
describe the structure that is injured and how that damage may
have caused the effects on his performance that you observed—especially his
loss of grip and lower-arm control.
Hint: If you use the Layer 1 controls to fade down through the
skin, you can use the surface features of the skin to compare the wound in the
movie with the underlying anatomy.
Which nerves are responsible the actions that Will found
difficult to perform (Hint: Use the information in the Muscles section to
identify the nerve supplies for various muscles whose functions Will lost).
Give your evidence for this conclusion.
Which nerves are associated the actions that Will still could
Give your evidence for this conclusion.
your conclusions about the nature of the injury, and explain how the evidence
in your answers above led you to your conclusions about the nature of this
injury and why it produced the problems that it did for our hero.
Two different types of peripheral nerve damage produce similar
hand deformities. One is called the “Bishop’s sign” or
“benediction” because of the similarity to the way that clerics
position their hands when blessing a congregation. The other is sometimes
called the “ulnar claw”. These occur when nerve damage affects the
relative positions of the fingers in similar ways, but for different reasons.
the neuromuscular interactions that are responsible for these two phenomena.
How do the nerves, muscles, bones, and joints interact in making these hand
signs different from each other and from the unmodified positions of these
structures in the hand?
Be sure to identify the muscles involved in these conditions and
the nerves that supply them, and to describe how the interactions of the nerves with
the muscles, bones, and joints accomplish this phenomenon.
speaking, explain how these two conditions (what nerves supply the
“normal/natural” actions of these muscles and how their activation
must be changed to produce these movements of the bones and joints).
In addition, identify where the “motor program” is
primarily affected … at the level of the hand muscles, in the PNS, in the
spinal cord, or in the brain (and where in the brain)..so that these signs are
remember that this assignment is in the unit on the brain and nervous system,
so your answers should be focused accordingly.