Presented by: Jessica Forbes

Introduction

• If you touch a hot stove, you do not stop to think about how your body tells you that it’s hot

• This is an example of REFLEX ARC

• the simplest possible arrangement of elements to permit a response to stimuli (in this example the heat), and in which the final element in the chain is skeletal muscle

• simplest nerve pathway

Reflex Arc Works By• feeling heat on your

body is detected by specialized receptors in the skin

• nerve pulse is then carried to the spinal cord.

• sensory neuron passes the impulse on to an interneuron

• interneuron passes impulse to a motor neuron

• motor neuron causes muscles to contract and pull away from stimuli

http://img.tfd.com/dorland/thumbs/arc_reflex.jpg

This Happens Fast• all of this happens in

less than a second• before the information

even travels and reaches the brain

• once the message reaches the brain, you will begin to feel the pain

• reflexes are involuntary and often unconscious

• you move your hand away before you "know why" you're doing it

http://www.free-ed.net/sweethaven/MedTech/NurseCare/fig91902_05.jpg

Five Essential Components

1. The receptor (finger, hand, etc)

2. The sensory neuron (travels message to the interneuron)

3. The interneuron (in spinal cord)

4. The motor neuron (travels message to the muscle)

5. The effector (the muscle)

http://www.bbc.co.uk/schools/gcsebitesize/flash/bireflexarc.swf

Sources • Di Giuseppe, Maurice, and Angela Vavitsas. Biology 12 . Toronto,

Ontario: Nelson & thomson Canada Limited, 2003.

• Norton, W.. "Reflex Arcs." Animated Tutorials: Introductory Biology . 2006. Sumanas Inc. 7 Jun 2007

<http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/reflexarcs.html>.

• "Revision that's easier to digest." BBC. BBC. 7 Jun 2007 <http://www.bbc.co.uk/schools/gcsebitesize/flash/bireflexarc.sw f>.

• "Somatic Reflex Arc ." 7 Jun 2007 <http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab9/Examples/exsomarc.htm>.