Reflexes Rapid, predictable, involuntary response to stimuli Maintain homeostasis Autonomic reflexes include smooth and cardiac muscle and glands Somatic reflexes include skeletal muscle
Reflex Arc Receptor (ex. In skin to detect pain, cold, heat, pressure) Sensory Neuron Interneuron (spinal cord) Motor neuron Effector (skeletal muscle, smooth muscle, glands, heart)
Stretch Reflexes Prevent overstretching of muscle Important for posture Equipment: Reflex hammer Patellar reflex assesses spinal cord L2 to L4 Achilles reflex assesses first two sacral segments
Superficial Cord Reflexes Stimulated by receptors in the skin Depend on upper motor pathways and cord level reflexes
Plantar Reflex Babinski Equipment: Reflex Hammer Handle Normal response: toes curl Positive Babinski: toes flare Normal Babinski response in infant indicates damage area between spinal cord and brain.
Cranial Nerve Reflexes Pupillary Reflexes Equipment: flashlight A reflex in which light shone into one eye causes the pupils of BOTH eyes to constrict involuntarily protecting against damage to the retina
Pupillary Reflex cont’d Absence of normal reflex, indicates: Severe trauma Deterioration of vital brain tissue due to metabolic imbalance Death!
Human Reflexes Biology 12