Somatosensory Flashcards
What are the 4 sensory pathways?
Fine Touch (discriminative)
Proprioception
Pain
Temperature
Touch : Stimulus? Receptor? Sense Organ?
Mechanical deformation
Skin Mechanoreceptors
Pacinian Corpuscle
Proprioception : Stimulus? Receptor? Sense Organ?
Mechanical Deformation
Mechanoreceptors
Muscle Spindl, Golgi Tendon Organs, Joint Receptors
Temperature :Stimulus? Receptor? Sense Organ?
Thermal Energy
Hot/Cold Thermoreceptors
Nerve Endings in Skin
Pain :Stimulus? Receptor? Sense Organ?
Noxious Stimulus - extreme mechanical, thermal, chemical energy
Nociceptors - Mechanoreceptive, thermal, chemoreceptive, polymodal
Nerve endings in the skin
What is Adequate Stimuli?
Differential sensitivity of sensory receptors
What is a Pacinian Corpuscle?
Rapidly Adapting Mechanorecptor
Depolarization occurs via stretch-activated Na+ channels
Detects mechanical pressure vibrations of 200-300Hz
What is Receptor Potential?
The depolarizing or hyper polarizing response to a sensory stimulus
Other Sensory Receptors
Hyperpolarization is due decreased Na current (photoreceptors) or increased K+ current (auditory mechanoreceptors)
Stereotypic encoding of stimulus intensity
The intensity of the stimulus in encoded by the frequency (number per time) of action potentials (AP)
What is frequency code?
Temporal Summation: increase in AP frequency of a single fiber associated with the sensory receptor
What is population code?
Spatial summation of is when more sensory receptors and their fibers are activated and Fire APs
What is Transduction?
The process of changing physical energy into electrical signals
What is a generator potential for transduction?
Change in membrane potential of the sensory receptors, caused by stimulus; may be depolarization (mechanoreceptors) or hyperpolarization (photoreceptor)
What is a first order neuron?
The first neuron to fire an action potential after stimulation
Labeled Line Code of Sensory Modality
Quality of the Stimulus is encoded by pathway of transmission
- quality = modality = sensory channel
What is a sensory modality?
A communication channel that is associated with individual senses e.g. Touch, smell, vision
What is Adaptation?
Nerves adjust to repetitive stimuli
Hyperalgesia
Heightened sensation of pain - Endogenous chemicals (prostaglandins) from damaged tissue directly activate or sensitize (lower activation threshold) nociceptors. Others are histamine, substance P, serotonin, and bradykinin
Neuralgia
Severe persistent pain in the distribution of a spinal or cranial nerve. Trigeminal neuralgia is treated by: tractotomy, injection of alcohol into the Trigeminal nerve, oral anticonvulsants
Thalamic Pain Syndrome
Lesions of Posterior Thalamus
Peripheral Neuropathy
Numbness and ulcers in limbs often seen in diabetic patients (stocking glove). Mechanism not well understood.
Referred Pain
Pain arising from deep visceral structures is felt at sites at the periphery of body.
Phantom Limb Pain
Limb removal leads to sensation of pain in missing limb
Analgesia
Inability to feel pain while still conscious
Sedation
A sedative is a drug that calms a patient down, easing agitation and permitting sleep, reducing irritability. Sedatives depress cardiovascular and respiratory functions, cannot be used with alcohol, and can become additive
Anesthesia (A State of Unconsciousness)
Has three components:
- analgesia: pain relief
- amnesia: loss of memory
- immobilization
Hereditary Sensory Autonomic Neuropathy Type 5
Loss of ability to feel pain, heat, or cold. Loss of deep pain perception - unable to feel broken bone, ligaments or muscle
