Biology Questions and Answers
roots contain motor fibers. Therefore
the dorsal roots are the ventral roots are motor rsensory roots anoots. d
- Which are the brain
regions associated with
memory?
Accordinmain regions og to researchf the nervous systemers some of the
associated with the memory
phenomenon are the hippocamsituated in the interior portion of thepus, (^)
temporal locortex, both part of the cerebralbes, and the frontal lobe
hemispheres.
- How is it structurally
explained that the motor
activity of the left side of the
body is controlled by the right
cerebral hemisphere and the
motor activity of the right side
of the body is controlled by
the left cerebral hemisphere?
In the cerebral heneurons that centrally commamispheres thnd andere are
control muscle movneurons are called superior mements. Theseotor
neurons and they are located in a
special gyrus of both frontal lobesknown as motor gyrus (or precentral (^)
gyrus). The superior motor neurons
send axons that transmitthe inferior motor neurons of the spinal impulses to (^)
cord (for neck, trumovements) and to the motor nnk and limb (^) uclei of
the cranial nerves (for face, eyes and
mouth movements).
The fibers cross to the other side in
specific areas ofAbout 2/3 of the fibers that go those axon paths. down the (^)
spinal cord cross at the medullar level
forming a structure decussation. The other (1/3) of fibersknown as pyramidal
descend in the same side of their
original ceronly within tebral hemisphehe spinal cord re and crossat the level
where their associated motor spinal root
exit. The fibers that commaninferior motor neurons of the craniald the (^)
nerves cross to the other side just
before the connection with ththese nerves. e nuclei of
The motor fisuperior motor nbers that descend from theeurons to the inferior
motor the pyramidal tract.neurons of the spinal cor Injuries in thisd form
tract, for example, caused by spinal
sections omay lead to r by central or paraplegia and tetraplespinal tumorsgia.
- What is meant by the arch
reflex?
In some situations thskeletal striated musclese movement of the does not
depend upon commamotor neurons, i.e., it is not triggnds of the superiorered
by volition.
Involuntary movmuscles may happen when sensoryements of those (^)
fibers that make direct or indirectconnection with inferior motor neurons (^)
are unexpectedly stimulated in
situations that sugbody. This happens, fgest danger to theor example, in the (^)
patellar reflex, or knee jerk reflex, wa sudden percussion on the knee patellahen
(kneecap) triggers an involuntary
contractionextension muscle o of the quadriceps (thf the thigh). Anothere (^)
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