Peripheral Nervous System

Question 1

What are the 3 structures of the PNS

Answer 1

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)

Question 2

How can sensory receptors be grouped

Answer 2

Simple (dendrite or free nerve ending), complex (specialized cell), by structure, location, or function

Question 3

What are the 5 types of sensory receptors functionally

Answer 3

Mechanoreceptors, thermoreceptors, chemoreceptors, photoreceptors, and nociceptors

Question 4

What are the characteristics of mechanoreceptors

Answer 4

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

Question 5

What is a root hair plexus

Answer 5

Free nerve ending wrapped around hair follicle to respond to movement

Question 6

What are proprioceptors and where

Answer 6

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)

Question 7

What are thermoreceptors

Answer 7

Free nerve endings responding to temp changes (distinct/separate ones respond to cold vs hot temps), found throughout body

Question 8

What do chemoreceptors do

Answer 8

Respond to specific chemicals (nutrients and oxygen of blood/blood chemistry), smell, taste buds

Question 9

What do photoreceptors do

Answer 9

Respond to light (in retina and melanocytes)

Question 10

What are nociceptors

Answer 10

Free nerve endings that respond to mechanical, thermal, or chemical stimuli in extremes (excessive pressure, extreme temps, chemicals released from damaged cells, etc)

Question 11

What is congenial insensitivity to pain (CIP)

Answer 11

Nociceptors damaged or not functional so the individual can’t feel pain (dangerous because could be hurt without knowing)

Question 12

What is a motor unit

Answer 12

A somatic motor neuron and all the muscle fibers if innervates

Question 13

What is the neuromuscular junction

Answer 13

Where axon terminal communicates with skeletal muscle fiber (sits right in top of cell membrane/sarcolemma)

Question 14

What neurotransmitter is released at neuromuscular junction with skeletal muscle cells

Answer 14

Acetylcholine (ACh)

Question 15

What neurotransmitter is released at synapse with smooth muscle cells

Answer 15

Acetylcholine or norepinephrine (NE)

Question 16

What’s different about innervation of smooth muscle

Answer 16

Happens at multiple locations (varicosities are like bulbs full of synaptic vesicles)

Question 17

How many cranial nerves are there

Answer 17

12

Question 18

How many pairs of spinal nerves are there

Answer 18

31: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

Question 19

What are dermatomes

Answer 19

Map showing relationship between sensory receptors of the skin and spinal nerves

Question 20

What is paraplegia

Answer 20

Permanent spinal cord damage between vert T1 - L2 causing loss of feeling/function to legs

Question 21

What is guadriplegia

Answer 21

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

Question 22

What are the spinal nerve plexuses and where

Answer 22

Cervical and brachial up by neck and shoulders, lumbar and sacral in lower torso

Question 23

What is polio

Answer 23

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

Question 24

What is postpolio syndrome

Answer 24

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

Question 25

What is the Autonomic Nervous System (ANS)

Answer 25

Visceral motor neurons

Question 26

What are the 5 functions of the ANS

Answer 26

Works with visceral sensory division, self governing and usually involuntary motor responses, innervate smooth muscle (digestion, blood pressure, and urination), cardiac muscle (heart rate) and glands (sweating, salivation, digestive enzymes, etc)

Question 27

What does the parasympathetic division of the ANS do

Answer 27

Resting and digesting, conserves energy and oversees standard bodily functions, localized affect

Question 28

What does the sympathetic division of the ANS do

Answer 28

Fight, flight, or fright, mobilized body in extreme situations (fear, anger, exercise), short term response that needs more energy

Question 29

Is one system of the ANS ever active without the other

Answer 29

No, the other gets less active but never shuts down completely, they balance each other out

Question 30

Where does the parasympathetic division come from

Answer 30

Exits the brainstem and sacral spinal nerves (very high or low, not the middle)

Question 31

Where does the sympathetic division come from

Answer 31

Exits thoracic and lumbar regions

Question 32

What’s the difference between somatic and visceral motor neurons (other than what they innervate)

Answer 32

Somatic has one neuron between spinal cord and skeletal muscle, visceral had two between spinal cord and target tissue that synapse via an autonomic ganglion

Question 33

Describe the parasympathetic pathway

Answer 33

Not much branching, long preganglionic axon, short postganglionic axon, and autonomic ganglion near or inside target tissue (both ganglionic and target tissue synapse release ACh)

Question 34

Describe the sympathetic pathway

Answer 34

Lots of branching, short preganglionic axon (releases ACh at synapse), long postganglionic axon (releases NE at synapse), autonomic ganglion near spinal cord

Question 35

What is the sympathetic trunk

Answer 35

Runs parallel to spinal cord, outside vertebrae, pathway for neurons of sympathetic division

Question 36

What are sympathetic trunk ganglia

Answer 36

Expansions of sympathetic trunk where pre and post ganglionic neurons synapse (bulges fill of cell bodies)