KPDS 2012-1 Soru=42

According to the passage, the knee jerk reflex is ----.

A behavioural pattern is considered to be innate when
it is essential for survival and already present at birth,
as it is predetermined by the genetic make-up of the
organism. A reflex is the simplest form of an innate
behaviour. It is a programmed reaction to an outside
stimulus that is carried out unconsciously. For example,
the eyelids close automatically as soon as a draft of air
stimulates the surface of the eye and the pupils of a cat
will contract as soon as it looks into bright light. These
are reflexes that an organism does not have to learn;
they are referred to as unconditioned reflexes. An
unconditioned reflex is always an unconscious
response, and therefore it is impossible to suppress it
at will. Such a reflex always requires a stimulus that
triggers a certain behaviour. Many unconditioned
reflexes exist in order to protect the organism, for
example coughing, nausea, or the draw back reflex of
the body part that touches a hot object. Anatomically,
a reflex is based on a chain of stimulus and reaction,
which is referred to as a reflex arc. A well-known
example is the knee jerk or patellar reflex in humans,
which is triggered by a light hit to the patellar tendon in
the knee. The knee jerk reflex is often used in medicine
to test the function of the spinal cord and associated
nerves. The real purpose of this reflex is to protect
humans from injury when tripping.