Sensory Receptors and PNS Flashcards
(16 cards)
5 types of Receptors
Chemoreceptors - respond to biomechanical stimulus (smell, taste, etc.)
Photoreceptors - light
Thermoreceptors - temperature
Mechanoreceptors - physical deformation (touch, pressure, etc.)
Nociception - pain (can be extreme heat or cold)
Define Sensory Transduction
the process by which sensory receptor cells convert stimulus energy into an electrical signal
Receptor Potential
- Local, graded potentials
- May be depolarizing or hyperpolarizing
- Can be direct ion channels or G-protein channels
Two types of adaptation
Slow adapting - better for sustained stimulus (clothes on back)
Rapid Adapting - better for changing, or sensing beginning or end of stimulus (pulling a hair on arm)
Receptor Potential and Action Potentials
All sensory receptors produce receptor potentials
-Local potential (spreads passively to synapse) postsynaptic potential trigger zone change AP frequency
-Photoreceptors, auditory, vestibular receptors
Some also produce action potentials
-Some receptors must convey information over long distances
-Receptor is capable of propagating an AP (AP freq. is modulated by receptor potential)
-No peripheral synapse
-Trigger zone is part of same neuron that contains receptor ending
Somatosensory receptors examples? what type of neuron?
- Stimulate by specific stimuli (touch, temperature, vibration, etc)
- Pseudounipolar that terminate in CNS
2 Categories of Somatosensory Receptors
Encapsulated
-Meissner’s Corpuscle – rapid adaptation - fine touch
-Pacinian Corpuscle – rapid adaptation – vibration
-Ruffini Ending – slow adaptation – pressure
Nonencapsulated
-Hair follicle receptor – movement/touch
Rapid adaptation – quick touch
-Merkel ending – touch
Slow adaptation - sustained touch
-Free nerve endings – pain, touch (some mechanoreceptors) and temperature receptors
-Nociceptors – respond to intense mechanical stimuli (pinching), extreme heat or cold, chemicals
-Fast pain (delta pain) - fast, sharp, well-localized pain - (myelinated)
-Slow pain - slow, dull, aching, longer-lasting pain - (unmyelinated)
Muscle Spindle function
Small muscle fibers within a spindle that informs the nervous system of the length of the muscle (provides sense of limb position, movement and MOSTLY kinesthesia)
Two Types of Muscle Spindle Endings
- Primary endings- respond to onset of stretch – rapidly adapt
- Secondary endings- respond to maintained stretch – slowly adapt
Two sources of motor innervation for all muscles
- Alpha motor neurons- to extrafusal muscle – for contraction
- Gamma motor neurons- to (intrafusal) muscle spindle – for sensitivity maintenance in contracted muscle
Golgi Tendon Organ function
(At union between muscle and tendon), informs the brain to the amount of tension in the muscle and tendon
- Contributes MOST to the sense of force exerted during movement
What structures are found in joint receptors?
Free nerve endings, golgi tendon organs, and pacinian corpuscles
Visceral Receptors
- Mechanoreceptors of hollow organs (aorta) – monitor blood pressure/volume
- Chemoreceptors (carotid body/sinus) – monitor blood gases and pH
- Nociceptors (organ capsule) – monitor distention
Connective Tissue covering of nerve
- Endoneurium — loose connective tissue that encloses axons and their myelin sheaths
- Perineurium — coarse connective tissue that bundles fibers into fascicles (continuous with arachnoid)
- Epineurium — tough fibrous sheath around a nerve
Nerve Fiber Diameter Classification
-A fibers = myelinated sensory and motor fibers
A fibers are subdivided
—Aα (A alpha) - largest and most rapidly conducting
—Aδ (A delta) - smallest and slowest of group A
-B fibers = myelinated visceral fibers (preganglionic autonomic and afferents)
-C fibers = unmyelinated
2nd Classification of Nerve Fiber Diameter
I, II, III- larger number = smaller size
IV - unmyelinated
