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Provide anatomy and
physiology advice to clients
Reflexes
Reflexes
• A reflex is a rapid, unlearned an involuntary action that
occurs as a response to a stimulus. If you were to touch
something hot then you automatically pull your arm away
before you even have the sensation of pain. This is a
reflex. It is interesting that both serial and parallel
processing occurs in reflexes. The sensor determines
that something is too hot. A signal travels to the spinal
cord to make you pull your hand away and a signal goes
to the brain to register pain. Study this slide carefully to
make sure that you understand about the components of
a reflex arc.
Spinal reflexes
• Body reflexes that are controlled by the spinal
cord are called spinal reflexes. These are very
important in skeletal muscle activity. The brain
must always know about the current state of
skeletal muscle. We saw in the last session how
the information about this is transferred from
muscle spindles and Golgi tendon organs. Now
for muscles to be active they must also have
healthy muscle tone. This depends on stretch
reflexes that are initiated by muscle spindles.
The stretch reflex
• Stretching the muscle spindle can work
either when we lengthen a muscle such as
when we carry a heavy load or when
antagonistic muscles contract. In both
these cases the sensory neurons around
the spindle transmit impulses at a higher
frequency to the spinal cord. The reflexive
muscle contraction which follows resists
further stretching. You can see both these
in this slide.
The patellar reflex
• Study this slide closely to come to terms
with a stretch reflex.