BSC 2086L Anatomy Physiology Lab II Chap 21 Human Reflex Physiology Chap 22 General Sensation Chap 21 Reflex Physiology Reflex Arc mediated by neural paths connections of neurons to yield rapid involuntary muscle response to stimuli Two main groups of reflexes 1 Autonomic mediated thru autonomic nervous sys smooth muscles in digestion glands in sweating 2 Somatic involve sensory stimulation that causes skeletal muscles to react withdrawal reflex from pain Components of Reflex Arc 1 Receptor site of stimulus 2 Sensory neuron transmits afferent impulse to central nervous system CNS Integration center one or more synapses in CNS Sensory neuron Receptor Skin Stimulus 4 Motor neuron conducts efferent Integration center impulse to effector Effector muscle glands respond to impulses Effector Motor neuron 3 5 1 2 3 4 5 Interneuron Spinal cord in cross section Note you are responsible for the structures terms on a figure if it is underlined in blue or in a blue box Monosynaptic Polysynaptic Spinal Reflex Arcs Spinal reflexes initiated completed at spinal cord level without involvement of higher brain centers Remember these are somatic reflexes Knee jerk reflex utilizes a 2 neuron sensory and motor neurons monosynaptic reflex arc Flexor reflex utilizes sensory and motor neurons connected by interneurons polysynaptic reflex arc Fig 21 2 Spinal cord Interneurons Sensory receptor muscle spindle Sensory afferent neuron Motor efferent neuron Motor efferent neuron Effector quadriceps femoris muscle Effector biceps brachii muscle Monosynaptic reflex Polysynaptic reflex Sensory afferent neuron Sensory receptor endings in fingertip Nail Fig 21 2 Spinal cord Interneurons Sensory receptor muscle spindle Sensory afferent neuron Motor efferent neuron Motor efferent neuron Effector quadriceps femoris muscle Effector biceps brachii muscle Monosynaptic reflex Polysynaptic reflex Sensory afferent neuron Sensory receptor endings in fingertip Nail Somatic Reflexes cont Spinal reflex 1 Stretch reflex maintains posture balance locomotion tendon stretch causes agonist muscle contraction and antagonistic relaxation e g Patellar knee jerk reflex 2 Crossed extensor reflex flexion of one limb followed by extension of opposite limb 3 Superficial cord reflex result from pain and temperature changes e g Plantar reflex Babinski s sign abnormal response is flared toes 2 Fig 21 3 Quadriceps extensors 1 3a 3b Patella Hamstrings flexors Patellar ligament Excitatory synapse Inhibitory synapse 3b Spinal cord L2 L4 1 Tapping the patellar ligament excites muscle spindles in the quadriceps 2 Afferent impulses blue travel to the spinal cord where synapses occur with motor neurons and interneurons 3a The motor neurons red send activating impulses to the quadriceps causing it to contract which extend the knee 3b The interneurons green make inhibitory synapses with ventral horn neurons purple that prevent the antagonist muscles hamstrings from resisting the contraction of the quadriceps Somatic Reflexes cont Cranial Nerve Reflex 1 Corneal reflex a function of cranial nerve V trigeminal Touching of the cornea causes blinking to occur 2 Gag reflex a function of cranial nerves IX glossopharyngeal X vagus Touching of the uvula causes gag reflex Autonomic Reflexes Pupillary reflexes reflex caused by light stimulation of cranial nerve II optic causing iris constriction by cranial nerve III oculomotor 1 Pupillary light reflex pupil constricts due to light stimulus 2 Consensual reflex light stimulation of one eye causes pupil constriction in contralateral opposite side eye Ciliospinal reflex stimulation of back of neck causes ipsilateral same side pupil dilation Salivary reflex food odor detection causes salivation Chap 22 General Sensation General senses general sensory receptors respond to touch pressure pain heat cold stretch vibration body position Found throughout body Special senses localized in groups receptors for sight hearing equilibrium smell taste Types of Receptors that can detect stimuli Exteroceptors react to external stimuli Interoceptor visceroceptor react to internal stimuli Proprioceptor detects body limb position Flower spray endings secondary sensor endings Anulospiral endings primary sensory endings Muscle spindle Capsule connective tissue Tendon organ Efferent motor fiber to muscle spindle Fig 22 2 Efferent motor fiber to extrafusal muscle fibers Extrafusal muscle fiber Intrafusal muscle fibers Sensory fiber Tendon Extrafusal muscle fibers Capsule Intrafusal muscle fibers General Sensory Receptors Structures Free naked nerve endings Hair follicle receptor non encapsulated detects light touch Free nerve endings detects pain temperature Encapsulated nerve endings Tactile Meissner s corpuscle detects light touch light pressure Bulbous Ruffini s corpuscle detects deep pressure stretching Lamellar Pacinian corpuscle detects deep pressure high frequency vibrations Tactile corpuscle touch light pressure Fig 22 1 Free nerve endings pain temperature Epidermis Dermis Free nerve endings Epidermal cells Tactile corpuscle Dermal papilla Epidermis Dermis Bulbous corpuscle deep continuous pressure Hair follicle receptor hair movement light touch Lamellar corpuscle deep pressure Lamellar corpuscle Receptor Physiology Four qualities of cutaneous sensations touch heat cold pain They are non uniformly distributed throughout the body hands have more touch receptors than arm etc Distribution based on the importance of the area and the need for those receptors Receptor Physiology cont Stimulus detection terminology Two point threshold smallest distance 2 points of contact can be perceived use a vernier caliper for this activity Tactile localization determining which point on skin has been stimulated Adaptation sensory receptor discharge from stimulus slows causing the perception of stimulus to decrease Referred pain perception of pain from one area of body when another area is actually receiving the noxious stimulus How to use read a vernier caliper 1 Using the rounded tab push the outer slide to the right 1 Place your thumb here and move the outer slide to the right This will open the caliper 2 Read the caliper 2 The distance between the prongs of the caliper is shown on top where the outer zero mark lines up with the marks on the bottom of the inner ruler 3 Read the caliper 3 The outer zero mark lines up with the fourth mark indicating that the distance between the two prongs is 4 mm 4 Adjusting the caliper 4 You can adjust the
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