Lecture 14 - The PNS Flashcards
how many pairs of cranial nerves are there?
12
how many pairs of spinal nerves are there?
31
what structures are innervated by the somatic nervous system?
skin, muscle, bone, parietal membranes
what type of tissue does the somatic motor system innervate?
skeletal muscle, voluntary control (exception - reflex arc)
what types of sensation are somatic sensory neurons responsible for feeling?
pain, temperature, touch, proprioception
what type of pain is felt by somatic sensory neurons?
direct pain arising from the site of the injury; sharp, focussed and well-localized
what type of tissue does the autonomic nervous system innervate?
supplies viscera (glands, smooth muscle, cardiac muscle, visceral membranes)
what type of pain is felt by the autonomic sensory neurons?
stretch or lack of oxygen at the organs, vague, ill-defined and ache like, perceived as indirect or referred pain
spinal nerves are bundles of:
axons
at what point do the spinal nerves exit the vertebral column below the vertebrae and not above?
transition point at C8
what are the four main classes of spinal nerves?
- somatic afferents (GSA)
- visceral afferents (GVA)
- somatic efferents (GSE)
- visceral efferents (GVE)
detects pain, temperature, touch, and proprioception from the body wall
somatic afferents (GSA)
detects pain, distension, and chemical changes in visceral structures
visceral afferents (GVA)
motor neurons in the ventral horn projecting to skeletal muscles
somatic efferents (GSE)
autonomic fibres (sympathetic or parasympathetic) innervating smooth muscle, cardiac muscle, and glands
visceral efferents (GVE)
what are the two primary branches of the spinal nerve?
dorsal primary ramus, ventral primary ramus
the dorsal and ventral roots are _____ long, and join up to form the ______
~1cm, spinal nerve
the spinal nerve exits the vertebral column through the:
intervertebral foramen
a dense irregular connective tissue that surrounds a whole spinal or peripheral nerve and fills the spaces between the nerve fascicles
epineurium
a protective sheath that surrounds an individual nerve fascicle
perineurium
a protective sheath that acts like a saran wrap around an individual axon and its myelin sheath
endoneurium
an area of skin supplied by nerves from a single spinal root (all spinal nerves innervate a band of skin)
dermatomes
what are the three somatic nerve plexuses?
- brachial plexus
- lumbar plexus
- lumbosacral plexus
in a nerve plexus, all of the nerves ____ with one another
interact
which spinal nerves form the brachial plexus?
C5, C6, C7, C8, and T1
what are the five main nerves that stem from the brachial plexus?
1) axillary (shoulder)
2) musculocutaneous (biceps)
3) median (forearm flexors, thenar)
4) radial (posterior arm and forearm)
5) ulnar (hand muscles - except thumb)
which spinal nerves form the lumbar plexus?
L1, L2, L3, L4
what is the main nerve that stems from the lumbar plexus?
the femoral nerve (anterior compartment of thigh)
which spinal nerves form the lumbosacral plexus?
L4, L5, S1, S2, S3
what are the two main nerves that stem from the lumbosacral plexus?
1) tibial (posterior thigh, toe muscles)
2) common peroneal (lateral leg, ‘foot drop’)
what are the five main steps of the reflex arc?
1) arrival of stimulus and activation of receptor
2) activation of a sensory neuron
3) interneuron sends information to be processes in the CNS
4) interneuron activates the motor neuron
5) response by effector
what is the purpose of the reflex arc?
to remove the body from a painful or uncomfortable stimulus
the autonomic nervous system is a _____ pathway
two neuron
which region of the of the spinal cord/brainstem is part of the sympathetic nervous system?
thoracolumbar –> T1-L2
which region of the spinal cord/brainstem is part of the parasympathetic nervous system?
craniosacral –> CN III, CN VII, CN IX, CN X, S2, S3, S4
in the somatic motor system, one axons emerges from the ____, and travels to the ____. this is known as the ____
CNS, effector site, ‘common final pathway’
in the autonomic motor system, the preganglionic fibre travels from the _____, and travels to the _____
CNS, autonomic ganglion
in the autonomic motor system, the postganglionic fibre travels from the _____, and travels to the _____
ganglion, effector site
- has a short preganglionic fibre
- has a long postganglionic fibre
- releases norepinephrine/epinephrine into the bloodstream (adrenal medulla) or onto the target tissue
these are all characteristics of the:
sympathetic nervous system
- has a long preganglionic fibre
- has a short postganglionic fibre
- releases acetylcholine at the target tissue
these are all characteristics of the:
parasympathetic nervous system
what effect does the sympathetic nervous system have on the eyes?
dilates pupils
what effect does the sympathetic nervous system have on the salivary glands?
thick viscid secretion
what effect does the sympathetic nervous system have on the trachea and bronchioles?
dilation
what effect does the sympathetic nervous system have on the heart?
increases heart rate and contractility
what effect does the sympathetic nervous system have on the ureters and bladder?
relaxes detrusor m., contracts trigone and sphincter (prevents voiding)
what effect does the sympathetic nervous system have on the gastrointestinal system?
decreases motility and tone, contracts sphincters
what effect does the sympathetic nervous system have on the genetalia?
male - stimulates ejaculation
female - relaxes uterus (partuition)
what effect does the sympathetic nervous system have on the blood vessels?
skeletal muscle - dilates
viscera - constricts
list the steps that sympathetic nerves takes to innervate the skin
1) preganglionic sympathetic neuron travels down the ventral root in the white ramus communicantes
2) synapses in sympathetic chain ganglion
3) signal exits the ganglion and travels to the skin down the gray ramus communicantes
list the steps that sympathetic nerves takes to innervate the heart and lungs
1) preganglionic sympathetic neuron travels down the ventral root in the white ramus communicantes
2) synapses in sympathetic chain ganglion
3) signal travels up the chain
4) the signal exits the chain and travels to the heart/lungs
list the steps that sympathetic nerves takes to innervate the abdominal viscera
1) preganglionic sympathetic neuron travels down the ventral root in the white ramus communicantes
2) signal passes through the sympathetic chain ganglion and travels down the splanchnic nerves
3) synapses at the celiac ganglia
4) signal travels along nerves surrounding the celiac artery
cutaneous and visceral sensory (pain) neurons share the same:
ascending tracts to the brain
what is referred pain?
pain in the visceral organs is often felt at the skin because the brain can’t tell the difference between cutaneous and visceral signals
what effect does the parasympathetic nervous system have on the eyes?
pupil constriction and accomodation reflex
what effect does the parasympathetic nervous system have on the lacrimal glands?
stimulates tears
what effect does the parasympathetic nervous system have on the salivary glands?
copious watery secretion
what effect does the parasympathetic nervous system have on the trachea and bronchioles?
constricts them and increases secretion
what effect does the parasympathetic nervous system have on the heart?
decreases heart rate and decreases contractility
what effect does the parasympathetic nervous system have on the ureters and bladder?
contracts the detrusor m., relaxes trigone and sphincter (voids bladder)
what effect does the parasympathetic nervous system have on the gastrointestinal system?
increases motility and tone
what effect does the parasympathetic nervous system have on the genetalia?
stimulates erection
the autonomic motor system is controlled by the:
hypothalamus
