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   An intereting study. However, at least in humans, whiplash =
injuries (or acceleration-deceleration injuries) are caused by overstretchi=
ng of neck ligaments and muscles, not by reduced blood supply to the brain.=
. And our carotid and vertebral arteries are normally connected, too, =
through the circle of Willis, even though we cannot rotate our necks a=
s much as the owls...
<br/>   Dusan Soudek
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<br/>---------- Original Message ----------
<br/>From: "Laviolette, Lance (EXP)" <lance.laviolette@lmco.=
com>
<br/>To: "naturens@chebucto.ns.ca" <naturens@chebucto.ns.ca&=
#62;
<br/>Date: February 25, 2013 at 10:46 AM
<br/>Subject: [NatureNS] Owl's Extreme Head Rotation Explained
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Hi Everyone,
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I came across an article noting that scientists at Johns Hopkins Medici=
ne had uncovered the reasons why an owl can almost fully rotate its heads. =
I=E2=80=99ve pasted a summary of the article below with a link to the full =
article afterward for those of you who are interested. All the best,
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Lance
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;">=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D</span>
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<span style=3D"font-size: small;">After much research, scientists at Jo=
hn Hopkins University have determined how owls are able to rotate their hea=
ds up to 270 degrees without damaging their blood vessels.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;">Humans get whiplash from rapid, twist=
ing head movements because that damages the arteries supplying blood to the=
brain. Researchers have discovered four special adaptations that keep owls=
from having a stroke every time they turn to watch potential prey.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"><strong>Arterial Reservoirs</strong><=
/span>
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<span style=3D"font-size: small;">The scientists discovered that blood =
vessels at the base of owl=E2=80=99s heads get larger and fill with blood a=
s the head turns. These arteries are pooling blood to minimize any interrup=
tions in blood flow to the owl=E2=80=99s brain and eyes. Human arteries, in=
comparison, remain small and do not increase in size as they branch out.</=
span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"><strong>Larger Holes in Vertebrae</st=
rong></span>
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<span style=3D"font-size: small;">The holes in an owl=E2=80=99s vertebr=
ae are ten times the size of the arteries which run through them. The large=
r holes create cushioning air pockets which allows for more flexibility and=
movement of the arteries, which prevents them from being damaged. This dif=
fers from human=E2=80=99s vertebral holes, which hug the arteries snugly.</=
span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"><strong>Higher Artery Entrance</stron=
g></span>
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<span style=3D"font-size: small;">Owl=E2=80=99s vertebral arteries were=
also found to enter the vertebrae higher up than in most birds, entering t=
he 12th vertebrae instead of the 14th. This gives the arteries more room an=
d slack , which allows for greater movement.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"><strong>Carotid and Vertebral Artery =
Connections</strong></span>
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<span style=3D"font-size: small;">The vertebral and carotid arteries in=
owls contain small connections that allow them to share blood between each=
other. This allows blood to be exchanged in the event that one or the othe=
r is blocked, ensuring continuous blood flow to the owl=E2=80=99s brain. Th=
ere are only rare examples of this found in human anatomy.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;">According to the scientists, these fo=
ur adaptations are what allow owls to turn their heads in such an extreme f=
ashion without any adverse effects.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;">The team from John Hopkins had their =
findings acknowledged in the journal Science February 1st as the winners of=
the National Science Foundation=E2=80=99s 2012 International Science &=
Engineering Visualization Challenge.</span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"><a href=3D"http://www.hopkinsmedicine=
.org/news/media/releases/owl_mystery_unraveled_scientists_explain_how_bird_=
can_rotate_its_head_without_cutting_off_blood_supply_to_brain"><span style=
=3D"color: #0000ff;"><span style=3D"text-decoration: underline;">http://www=
.hopkinsmedicine.org/news/media/releases/owl_mystery_unraveled_scientists_e=
xplain_how_bird_can_rotate_its_head_without_cutting_off_blood_supply_to_bra=
in</span></span></a></span>
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<span style=3D"font-size: small;"> </span>
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<span style=3D"font-size: small;"> </span>
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