Download Understanding Reflexes in Physiological Psychology: Mono- to Polysynaptic Responses - Prof and more Study notes Psychology of Human Development in PDF only on Docsity! 1 Listen to the audio lecture while viewing these slides 1 Psychology 372 Physiological Psychology Steven E. Meier, Ph.D. Spinal Reflexes 2 Psyc 372 – Physiological Psychology Overview • Importance first recognized Sherrington • Believed that simple reflexes activated by receptors in the skin and muscles were the basic units of movement. • Also, complex sequences of movement were the combinations of simple reflexes. • Has been the dominant view for 100 years. • New data shows that you can complete coordinated movement without sensory information. • Is still important 3 Psyc 372 – Physiological Psychology Overview Continued • Stimuli for reflexes comes from receptors in: • Skin • Joints • Muscles 4 Psyc 372 – Physiological Psychology Past • Reflexes were automatic and stereotyped • Occurred in response to some stimulus being applied to peripheral receptors. 5 Psyc 372 – Physiological Psychology Today • Know reflexes can be modified and adapt to tasks. • Can be smoothly incorporated with movements initiated by the cortex. 6 Psyc 372 – Physiological Psychology Three Principles of Reflexes • Transmission in reflex pathways is set according to the motor task. • Called a functional set. • Sensory input from a localized stimulus source produces reflex responses in many muscles • Some responses can be far away from the stimulus • Supraspinal centers modulate and help spinal reflexes adapt. 2 7 Psyc 372 – Physiological Psychology Reflexes • Two types • Monosynaptic • Polysynaptic 8 Psyc 372 – Physiological Psychology Monosynaptic Reflex • Involves one synapse between a sensory fiber from a muscle and an alpha-motor neuron • Monosynaptic stretch reflex (posture) • Patellar reflex 9 Psyc 372 – Physiological Psychology Stretch Reflex • Is a contraction of a muscle that occurs when a muscle is lengthened. • As you begin to stretch out the muscle, it begins to contract. • Also, the opposing muscles relax • Thus, stretch stimuli cause excitation in some motor neurons and inhibition in others. 10 Psyc 372 – Physiological Psychology How • Sensory receptors in the muscle sense that the muscle is beginning to stretch. Their signals to neurons in the spinal cord tell other neurons to • Relax opposing muscles • Contract the muscle that begins to stretch • Allows a feedback loop 11 Psyc 372 – Physiological Psychology Polysynaptic Reflexes • Involves multiple synapses between sensory axons, interneurons, and motor neurons • Axons from the afferent muscle spindles can synapse onto • Alpha motor neuron connected to the agonist muscle • An inhibitory interneuron connected to the antagonist muscle • Signals from the muscle spindle activate the agonist and inhibit the antagonist muscle 12 Psyc 372 – Physiological Psychology Example, Noxious Stimulus Withdrawal - Reflex Arcs • Occurs from interaction with • Afferent neurons (sensory) • Internuncial neurons • Efferent neurons (Motor) • Also sends information to cortical structures.
