Peripheral Nervous System (Chapter 13) Flashcards
Sensation
Conscious or subconscious awareness of internal or external stimuli; conscious awareness -> sent to cerebral cortex; Subconscious awareness -> sent to medulla
Perception
Conscious awareness and interpretation/meaning of sensations; Associated with cerebral cortex
Sensory Modalities
Unique types of sensations; One sensory neuron -> one type of sensory modality
General Senses
Tactile - touch, pressure, vibration; Thermal - warm/cold; Proprioceptive - position of body part in 3D space; Pain; Visceral
Special Senses
Smell, vision, taste, hearing, equilibrium/balance
1st Step of the Process of Sensation
Stimulation of sensory receptor -> via change in internal/external environment
2nd Step of the Process of Sensation
Transduction of Stimulus -> stimulus energy converted to graded potential, 1 sensory receptor sensitive to only 1 type of stimulus
3rd Step of the Process of Sensation
Generation of AP -> when graded potentials reach threshold, PNS to CNS
4th Step of the Process of Sensation
Integration of sensory input -> APs interpreted by association areas within cerebral cortex
Signaling Pathways: 1st Order Neurons
Somatic sensory receptors; conduct information from various body regions to brainstem or spinal cord
Signaling Pathways: 2nd Order Neurons
Conduct impulses from brainstem and spinal cord to thalamus
Signaling Pathways: 3rd Order Neurons
Conduct impulses from thalamus to primary sensory are in cerebral cortex
Sensory Receptors: Free Nerve Endings
Bare dendrites (1st Order) not covered by CT capsule; No special adaptations
Sensory Receptors: Encapsulated Nerve Endings
Dendrites (1st Order) enclosed by CT capsule
Sensory Receptors: Separate Specialized Cells
Sensory Receptors that synapse with 1st Order neurons; Epithelial-like cells that release neurotransmitters
Sensory Receptors: Exteroreceptors
Located at or near body surface; Provide information about external environment
Sensory Receptors: Interoreceptors
Located in blood vessels, internal organs, muscles, and nervous system; Usually not consciously perceived with exceptions being pain and pressure
Sensory Receptors: Stimuli Detected
Mechanoreceptors (Mechanical Stimuli: pressure, tactile, vibration) - detects changes in mechanical pressure; Thermoreceptors (Electromagnetic Stimuli) - detect changes in temperature; Nociceptors - detect stimuli resulting from physical or chemical damage to tissues; Photoreceptors (Electromagnetic Stimuli) - detect light striking the retina of eye; Chemoreceptors (Chemical Stimuli) - detect chemicals in mouth (taste), smell (nose) and body fluids; Osmoreceptors
Sensory Receptor Adaptation
Occurs when frequency of nerve impulses from 1 order neurons decreases due to prolonged stimulus; Rapidly adapting stimulus (adapt quickly) - specialized for signaling changes in stimulus; Slowly adapting receptors (adapt slowly) - trigger APs as long as stimulus persists
Somatic Sensory Receptors (Non-Encapsulated): Free nerve endings
Located in skin and mucous membranes
Somatic Sensory Receptors (Non-Encapsulated): Modified free nerve endings
Saucer-shaped dendrites; Located in epidermis; Stimulus: touch, light pressure (mechanical)
Somatic Sensory Receptors (Non-Encapsulated): Hair root plexuses
Surrounds hair follicles; Stimulus: bending of hair (mechanical)
Somatic Sensory Receptors (Encapsulated): Meissner’s corpuscles
Located in dermal papillae; Stimuli: light touch, light pressure, slow vibrations
Somatic Sensory Receptors (Encapsulated): Pacinian Corpuscles
Located in the dermis, subcutaneous layer, submucosal tissue, joints, and periosteum; Stimuli: deep pressure, tickling, fast vibrations
Somatic Sensory Receptors (Encapsulated): Ruffini corpuscles
Located in the dermis, tendons, and ligaments
Proprioceptors (Muscle Spindles)
Composition: nerve endings wrapped around specialized muscle fibers; Located: usually skeletal muscles; Stimuli: muscle stretch which initiates reflexes to resist muscle stretching
Proprioceptors (Golgi Tendon Organs)
Location: junction of tendons and muscle; Stimuli: tendon stretch which initiates reflexes to resist tendon stretching
Proprioceptors (Joint Kinesthetic Receptors)
Both free and encapsulated dendrites; Location: articular capsules of synovial joints; Function: determine joint position and movement in 3D space