3A: Somatosensory Disorders Flashcards
Cutaneous senses
perception of touch and pain from stimulation of the skin
Proprioception
ability to sense position of the body and limbs
Kinesthesis
ability to sense movement of body and limbs
Skin
the largest organ in the body both in surface and in weight. The skin provides protection, regulation of body temperature and water loss, and sensation.
Epidermis
the outermost, protective layer of the skin, composed mostly of dead cells
Basement membrane
immediately below the epidermis is the basement membrane, a specialized structure that lies between the epidermis and dermis. It includes various protein structures liking the basal layer of keratinocytes (skin cells) to the basement membrane and the basement membrane to the underlying dermis. Once skin cancer cells cross this boundary, they can begin to spread through the body through the vascular system of the dermis.
Dermis
the middle layer of skin below the epidermis that forms the true skin, containing blood capillaries, nerve endings, sweat glands, hair follicles, and other structures.
Subcutaneous tissue
the deepest layer of the skin, made up of vessels, fat, and connective tissue.
Hairy skin
most of our skin has hair. The primary somatosensory receptor in hairy skin is the follicle receptor, which is a mechanoreceptor triggered by distortion of the hair shaft.
Glabrous skin
hairless skin (ex. palms, soles, lips, labia, penis); contains more specialized types of mechanoreceptors
Mechanoreceptor
a sensory receptor that responds to mechanical pressure or distortion via mechanotransduction: movement of the cell membrane physically pulls open/pushes closed ion channels in the membrane, leading to changes in cell signaling.
Slowly adapting fibers (SA)
fire continuously as long as pressure is applied to provide detailed/high acuity tactile info; found in Merkel’s disks (upper dermis) and Ruffini cylinders (lower dermis)
Rapidly adapting fibers (RA)
fire at onset and offset of stimulation to provide info about the start of a sensation; found in Meissner’s corpuscles (upper dermis) and Pacinian corpuscles (lower dermis)
Acute nociceptive pain
-Part of a rapid warning relay instructing the motor neurons of the central nervous system to minimize detected physical harm. It is mediated by nociceptors, on A-δ and C fibers.
-these nociceptors are free nerve endings that terminate just below the skin, in tendons, joints, and in body organs. They serve to detect cutaneous pain, somatic pain and visceral pain.
-nociceptors are specialized for heat, chemicals, severe pressure, and cold. Hot and cold sensations are carried via thermoreceptors.
-threshold of eliciting receptor response must be balance to warn of damage but not be affect by normal activity.
Chronic inflammatory pain
-inflammatory nociceptive pain is associated with tissue damage and the resulting inflammatory process
-it is adaptive in that it elicits physiologic responses that promote healing
Chronic inflammatory pain
-inflammatory nociceptive pain is associated with tissue damage and the resulting inflammatory process
-it is adaptive in that it elicits physiologic responses that promote healing
Chronic neuropathic pain
-neuropathic pain is produced by damage to the neurons in the peripheral and central nervous systems and involves sensitization of these systems.
-In peripheral sensitization, there is an increase in the stimulation of peripheral nociceptors that amplifies pain signals to the central nervous system.
-In the central sensitization, neurons that originate in the dorsal horn of the spinal cord become hyperstimulated, increasing pain signals to the brain and thereby increasing pain sensation.
Spinal cord
a long, thin, tubular bundle of nervous tissue and support cells (like glia) that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the CNS. In contrast to cortex, gray matter is in the inside of the spinal cord and is surrounded by white matter. The spinal cord has three major functions: as a conduit for motor information, which travels down the spinal cord, as a conduit for sensory information in the reverse direction, and finally as a center for coordination certain reflexes.
Vertebral column
bony structure made of multiple vertebrae that protects the relatively shorter spinal cord. Spinal nerves project through small openings in the vertebral bones.
Dorsal root ganglion
the sensory nerves of the peripheral nervous system have their cell bodies in the dorsal rot ganglion. These cells have projections that carry information from the peripheral sensory receptors-peripheral nerve- and also projections that carry information into the spinal cord- dorsal root.
Ventral root
is the motor nerve exiting the spinal cord to innervate muscle fibers
Fascicle
a bundle of neuronal axons surrounded by a connective tissue; a component of a nerve
Spinal reflex pathway
A neural pathway that controls a reflex action. As most sensory neurons synapse in the spinal cord before going to cortex, spinal motor neurons can be rapidly activated without waiting for signals to go to/ come from the brain first. Sensory input is sent to the brain while the reflex is being carried out.
Posterior columns
a set of somatosensory white matter tracts in the posterior spinal cord that carry information about fine touch, vibration, pressure, and joint position from the spinal cord to the thalamus (and then to S1). Name turns into ‘medial lemniscus’ when tracts reach the brainstem, where the dorsal root ganglion axons then synapse and cross to opposite side. Organized somatotopically.
