Peripheral Nervous System Flashcards
What are the 3 structures of the PNS
Sensory receptors and neurons (respond to stimulus and initiate AP in sensory neurons), motor neurons and endings (innervate end structures/cells), and structures that transmit/package neurons (nerves and dorsal root ganglia)
How can sensory receptors be grouped
Simple (dendrite or free nerve ending), complex (specialized cell), by structure, location, or function
What are the 5 types of sensory receptors functionally
Mechanoreceptors, thermoreceptors, chemoreceptors, photoreceptors, and nociceptors
What are the characteristics of mechanoreceptors
Respond to distortion caused by pressure changes, vibration, etc, located just deep to epithelium of lips, hairless skin, and fingertips, e.g. Meissner’s corpuscles, root hair plexus
What is a root hair plexus
Free nerve ending wrapped around hair follicle to respond to movement
What are proprioceptors and where
Free nerve endings found around skeletal muscle fibers, tendons, or joins that detect stretch in the fiber when it moves (e.g. muscle spindle and golgi tendon organ)
What are thermoreceptors
Free nerve endings responding to temp changes (distinct/separate ones respond to cold vs hot temps), found throughout body
What do chemoreceptors do
Respond to specific chemicals (nutrients and oxygen of blood/blood chemistry), smell, taste buds
What do photoreceptors do
Respond to light (in retina and melanocytes)
What are nociceptors
Free nerve endings that respond to mechanical, thermal, or chemical stimuli in extremes (excessive pressure, extreme temps, chemicals released from damaged cells, etc)
What is congenial insensitivity to pain (CIP)
Nociceptors damaged or not functional so the individual can’t feel pain (dangerous because could be hurt without knowing)
What is a motor unit
A somatic motor neuron and all the muscle fibers if innervates
What is the neuromuscular junction
Where axon terminal communicates with skeletal muscle fiber (sits right in top of cell membrane/sarcolemma)
What neurotransmitter is released at neuromuscular junction with skeletal muscle cells
Acetylcholine (ACh)
What neurotransmitter is released at synapse with smooth muscle cells
Acetylcholine or norepinephrine (NE)
What’s different about innervation of smooth muscle
Happens at multiple locations (varicosities are like bulbs full of synaptic vesicles)
How many cranial nerves are there
12
How many pairs of spinal nerves are there
31: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
What are dermatomes
Map showing relationship between sensory receptors of the skin and spinal nerves
What is paraplegia
Permanent spinal cord damage between vert T1 - L2 causing loss of feeling/function to legs
What is guadriplegia
Permanent spinal cord damage above vert T1, loss of feeling/function of all 4 limbs (partial to full of upper limbs), if above C4 impacts diaphragm and loses ability to breath on own
What are the spinal nerve plexuses and where
Cervical and brachial up by neck and shoulders, lumbar and sacral in lower torso
What is polio
Virus that (sometimes) targets (usually somatic) motor neurons, level of paralysis determined by what motor neurons where infected, epidemic mid 1900s, iron lungs for people who couldn’t breathe
What is postpolio syndrome
Surviving motor neurons developed axons sprouts to attach to muscle fibers that had lost innervation, but because of overuse these neurons are losing their connections and dying earlier
