Aaron Wu, Kat So, Joanna Gochuico, and Chris Evans Reflexes Aaron Wu, Kat So, Joanna Gochuico, and Chris Evans

History of Reflexes Reflexes were considered important since the time of Descartes (1600’s) Studies involved physiologists, neurologists, and psychologists. First to really study reflexes were René Descartes and Thomas Willis.

BELIEFS Decartes: When a sensation reached the pineal gland, it serves to orientate the “spiritus animus” in the right direction, to cause a reaction. Animal spirit = nerve impulse Spirit penetrate brain via very fine pores. Willis: nerve impulses journeyed to and from the brain, and that “animal spirits” were reflected back toward the periphery 3 types of movement

Decartes and De Homine De Homine’s :1st european book on physiology by Decartes (1662) Shows infant looking at a fire (A) and withdrawing his left foot (B). The 'pain' message is represented going to the pineal gland (F).

Reflexes Reflex: an automatic motor response to a specific stimulus Message route = PNS  CNS Purpose: help preserve homeostasis through rapid adjustments in function of organs systems

Simple Reflexes Monosynaptic: most rapid, requires one synapse Stretch Reflex Receptors = muscle spindles (m. fibers) Stimulus = increase muscle length Motor response= contraction Regulates muscle length Automatic response to maintain posture and balance by adjusting muscle tone Ex. Knee Jerk Reflex

Complex Reflexes Polysynaptic Reflexes: Withdrawal Reflexes: More synapses = longer delay between stimulus and response Withdrawal Reflexes: Move stimulated part away from source Strongest reflex initiated by pain Flexor reflex: reflex affecting muscle of limb ex. Hand to hot pan Reciprocal Inhibition: One set of motor neurons is stimulated, those controlling antagonistic muscles are inhibited

Control of Spinal Reflex Sensitivity of reflex can be modified Higher centers of the brain can stimulate or inhibit interneuron's and motor neurons involved Descending fibers have inhibitory effect on spinal reflexes Babinski sign (+) = fanned toes, (-) = plantar reflex If signs return in adulthood, CNS injury Descending pathways from brain facilitate, inhibit, fine- tune established reflexes

Reflex Arc (pg 273)

Types of Reflexes Somatic Reflexes: skeletal muscles. Autonomic Reflexes: Smooth and Cardiac muscle. Ex. Digestion, blood pressure Innate Reflex Actions: Involuntary Action Withdrawal Reflex: Response generated without brain analyzing stimulus fully Stretch Reflex: When a muscle is struck, causes contraction For a quiz - I was thinking to give two examples and ask them which type of reflex it is. Touching a hot object - withdrawal Knee Jerk reflex - stretch Blinking when bright - involuntary

Bibliography http://outreach.mcb.harvard.edu/teachers/Sum mer05/JerryHalpern/Reflexes.pdf http://www.bbc.co.uk/science/humanbody/bod y/factfiles/reflexes/reflexes.shtml http://www.pennmedicine.org/health_info/bod y_guide/reftext/html/nerv_sys_fin.html http://www.ibro.info/Pub/Pub_Main_Display.a sp?LC_Docs_ID=3155 Human Anatomy Textbook Pg. 272-274