REFLEXES

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REFLEXES
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WHAT IS A REFLEX?

• Rapid, automatic response to a stimulus.

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Neurons in a Reflex

• Sensory(Afferent)-carry messages to brain and
  spinal cord.
• Motor(Efferent)-carry messages away from brain
  and spinal cord.

• Interneurons-send messages between nerve cells
  within the brain, spinal cord, and periphery.

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WHAT IS A REFLEX ARC?

• Nerve pathway involved in a reflex action.

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COMPONENTS OF A REFLEX ARC

• RECEPTOR-Site of stimulus action.
• AFFERENT NEURONS-transmits the afferent impulse
  to the CNS.
• INTERGRATING CENTER-Control center.
• EFFERENT NEURONS-Conducts efferent impulses from
  the integration center to an effector organ.

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COMPONENTS CONT.

• EFFECTOR- Muscle fiber or gland cell that
  responds to the efferent impulses by contracting
  of secreting.

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TYPES OF REFLEX ARCS

• SOMANTIC REFLEX ARCS-single motor neuron in the
  path and skeletal muscle is always the effector.
  May be deep or superficial.
• VISCERAL REFLEX ARCS-Two motor neurons in the
  path,and effector can be smooth muscle and/or
  glands, but never skeletal muscle.

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KNEE-JERK REFLEX

• STRETCH REFLEX-work together to help maintain
  upright posture.
• Controls the movement of legs during running.

• MONOSYNAPTIC REFLEX-Has only a single synapse.

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WHY DO WE..

• COUGH- Irritant enters our windpipe and we need
  to expel it through our mouth.
• SNEEZE- Need to cleat our nasal air passages of
  irritants and allergens.
• BLINK-When danger threatens the sensitive tissue
  of the eye and when we need to moisten and clean
  the cornea. Occurs 900 times per hour.

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WHY DO WE.CONT.

• YAWN-When nerves in the brain stem find there's
  too much carbon dioxide in the blood.

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HYPNIC JERK

• Happens before falling fully asleep.
• Feels like you are losing your balance.

• Involves a temporary disruption in the part of
  the nervous system that controls our sense of
  balance.