ANS Spinal Reflexes Part 1 (Slides 1-34, Quiz 1) Flashcards
What is a reflex?
-a rapid, predictable automatic response to a stimulus/message
-involuntary
-involves a receptor, the CNS, and an effector
-outside of conscious control
define monosynaptic reflexes
-afferent in, efferent out
-only one junction
(whereas polysynaptic reflexes are afferent> interneuron(s) > efferent out)
What are the 7 steps of a somatic reflex/reflex arc?
1) stimulus
2) receptor
3) sensory neuron
4) integration center
5) motor neuron
6) effector
7) response
Where are interneurons located?
in CNS
A skeletal m. contracts in response to…
being stretched
Which nerve class is associated with a muscle spindle and sends APs when the muscle spindle fibers are stretched?
1a
T/F: CNS inhibition of ANS output is common
true
T/F: all neurons can decide to inhibit reflexes
false, only interneurons can do this
Golgi tendon organs (GTO) are proprioceptive. They stimulate 1b fibers and often causes inhibition of __________ neurons. Autogenic inhibition is thought to be a protective mechanism preventing excess tension or for contributing to fine adjustments
alpha motor
What is a withdrawal/flexor reflex?
-a somatic reflex
-involves a whole limb and several spinal segments
-painful stimuli from cutaneous receptors
-synapse on interneurons on the gray matter
-leave via multiple efferents to different muscles
-all primary afferents must bifurcate on the interneuron
-always polysynaptic
1 stimulus will have 1 afferent go in, multiple efferents go out. The interneuron spreads up and down to adjacent spinal segments, so it activates multiple different circuits. There will be withdrawal from stimulus w/o “checking in” with the brain
What are some examples of crossed effects in reflexes?
-only 1 eye constricts with light when both eyes should constrict
-flex a limb to withdraw from pain and then fall over, contralateral limb extends and supports
What are the 4 types of reflexes of the ANS?
1) somato-somatic reflex
2) viscero-visceral
3) somato-visceral
4) viscerosomatic
What is the pupillary light reflex?
shine bright light in one eye and both pupils should constrict
What are viscerosomatic reflexes?
-reflex between an organ and a closely related body part
-hard to pinpoint pain, sweaty, referred pain, muscle spasm
Shoulder pain can later be diagnosed as….
gallbladder disease
Flank pain is a precursor to what diagnosis?
kidney stones
cardiac ischemia or hypoxia presents as….
L arm pain
Fibers from cord segment T1 generally follows up the sympathetic chain to terminate in the….
head
Fibers from cord segment T2 generally follows up the sympathetic chain to terminate in the….
neck
Fibers from cord segment T3-T6 generally follows up the sympathetic chain to terminate in the….
thorax
Fibers from cord segment T7-T11 generally follows up the sympathetic chain to terminate in the….
abdomen
Fibers from cord segment T12-L2 generally follows up the sympathetic chain to terminate in the….
legs
What spinal cord segments have lateral horns?
T1-L2
The white ramus can be remembered as “white out” What classification of nerve fibers exit through here?
B fibers
Parasympathetic fibers leave the CNS through cranial nerves 3, 7, 9, and 10; additional parasympathetic fibers leave the lowermost part of the spinal cord through the 2nd and 3rd sacral spinal nerves and occasionally the 1st and 4th sacral nerves. What nucleus does each CN 3, 7, 9, and 10 run through in brainstem?
CN 3 runs through Edinger-Westphal (EW) nucleus
CN 7 runs through superior salivary nucleus
CN 9 runs though the inferior salivary nucleus
CN 10 runs through the dorsal motor nucleus of vagus (DMX nucleus)
About 75% of all parasympathetic nerve fibers are in the….
vagus nerve
Fibers that secrete ACh are said to be…
cholinergic
Fibers that secrete NE are said to be….
adrenergic
All preganglionic neurons are _____________ in both the sympathetic and parasympathetic NS
cholinergic
T/F: ACh, when applied to the ganglia, will excite both sympathetic and parasympathetic postganglionic neurons
true!!!
All/almost all of the postganglionic neurons of the parasympathetic NS are…
cholinergic
Most of the postganglionic sympathetic neurons are…
adrenergic
What type of transport is used to move ACh or NE from the soma (nissl bodies) to the axon terminal?
anterograde transport
What are varicosities?
enlargements/swellings with neurotransmitter vesicles on the postganglionic axon
2 functions of the eyes are controlled by the ANS (dual innervation). What are they?
1) the size of the pupillary opening within iris
2) the focus of the lens
What is accommodation?
eye maintaining focus
What muscle group helps with accommodation?
ciliary body (meridional fibers and circular muscle)
Sympathetic stimulation contracts the ______________ of the iris which ________ the pupil
meridional fibers, dilates
Parasympathetic stimulation contracts the ______________ of the iris to ___________ the pupil
circular muscle, constrict
The parasympathetic NS controls the pupil as a reflex and it is stimulated when there is an excess of light. The response is to…
reduce the amount of light that hits photoreceptors by constricting the pupil
In general, sympathetic stimulation increases the overall activity of the heart. This effect is accomplished by increasing both the….
rate and force of heart contraction
(parasympathetic stimulation causes mainly opposite effects- decreased heart rate and strength of contraction)
What is the average heart rate for adults?
70 bpm
What is the average stroke volume for adults?
70 mL
What is stroke volume?
volume of blood that leaves the heart
Which ANS increases heart rate?
sympathetic NS
Which ANS increases stroke volume (contracts with more force)?
sympathetic NS
Which ANS contracts/constricts the tunica media to increase BP?
sympathetic NS
Which ANS decreases heart rate?
parasympathetic NS
Which ANS decreases stroke volume (don’t need a lot of blood out of the heart)?
parasympathetic NS
Which ANS dilates the tunica media in blood vessels to decrease BP?
parasympathetic NS
What is the central autonomic network (CAN) composed of?
hypothalamic and extra-hypothalamic nuclei
The single most important hypothalamic nucleus of the central autonomic network is the….
paraventricular nucleus (PVN)
The ________________ descends from the hypothalamus down the brainstem to the spinal cord. It can influence and control the activity of parasympathetic and sympathetic nuclei along the way and projects to the IML in lateral horns- sympathetic out
dorsal longitudinal fasciculus (DLF)
What ANS receptors are there for afferent activity in cardiovascular system?
baroreceptors (mechanoreceptors) within arteries and chemoreceptors sending info on pH (detects H+), carbon dioxide, oxygen (partial pressure) which initiates an AP
Receptors and afferents from the aortic arch reach the brainstem via the ______ nerve
vagus (CN X)
Receptors and afferents from the carotid artery enter via the ___________ nerve
glossopharyngeal (CN IX)
Info goes to brainstem within which cranial nerves to synapse on the solitary nucleus?
CN X and CN IX
Inputs from the heart/blood vessels synapse in the….
solitary nucleus
The solitary nucleus relays info from the heart and blood vessels to the autonomic centers in the _______________ and sends down negative feedback to visceral motor neurons and ______ nucleus
reticular formation, DMX
If chemoreceptors detect low oxygen, then the body wants to….
increase sympathetic NS
If baroreceptors detect high BP, then the body wants to….
inhibit sympathetic NS and activate parasympathetic NS
The tunica media only receives ___________ output
sympathetic
What is the major source of excitatory input to sympathetic nerves controlling the vasculature?
rostral ventrolateral medulla (RVLM)
A blood vessel that is neither constricted or dilated has weak or strong sympathetic tone?
weak sympathetic tone
When does a blood vessel have no sympathetic input?
when its dilated
When does a blood vessel have strong sympathetic tone?
when its constricted
What 3 substances function as vasoconstrictors in blood vessels?
1) NE
2) ATP
3) neuropeptide Y (NPY)
Which 2 substances regulate vasodilation in blood vessels?
ACh and calcitonin gene-related peptide (CGRP)
Endothelial dysfunction and inflammation are associated with ______________ nerve activity
sympathetic
2 separate neural mechanisms regulate respiration- one is responsible for ____________ control and the other for ___________ control
voluntary, autonomic
(the voluntary control system is located in the cerebral cortex and sends impulses to the respiratory motor neurons via the corticospinal tracts, whole to automatic system is driven by a group of pacemaker cells in the medulla)
Neurons in the cervical spinal cord activate the diaphragm via the __________ nerves
phrenic
Neurons in the thoracic spinal cord activate the _________________ muscles
external intercostal
T/F: inspiration is from low pressure to high pressure
false, its the opposite- high to low pressure
When is the diaphragm the longest?
when its relaxed
When is the diaphragm the smallest?
when its contracted
T/F: inspiration is always active, you cannot have inspiration without muscle contraction
true
T/F: expiration is always passive
false, not always
The respiratory center is composed of several groups of neurons located bilaterally in the medulla oblongata and pons of the brainstem.
1) a dorsal respiratory group which is located in the dorsal portion of the medulla and mainly causes ____________
2) a ventral respiratory group which is located in the ventrolateral part of the medulla and mainly causes _____________
3) the pneumotaxic center which is located dorsally in the superior portion of the pons and mainly controls _____________________
inspiration, active expiration, rate and depth of breathing
Where are most of the neurons located for the dorsal respiratory group?
solitary nucleus
The pneumotaxic center is located in the dorsolateral pontine tegmentum, caudal to the inferior colliculus. Located within…..
nucleus parabrachialis
Which nuclei is essential for maintaining a normal breathing pattern (switching between inspiration and expiration)?
respiratory nuclei/ nucleus parabrachialis
When the pneumotaxic signal is strong (small/short volume), inspiration will last for 0.5 second, thus filling the lungs ________
slightly
When the pneumotaxic signal is weak (large/long volume), inspiration will last for 5+ seconds, thus filling the lungs ___________
fully
The function of the pneumotaxic center is primarily to limit ____________, which has a secondary effect of increasing the rate of breathing
inspiration
Which nucleus is the ventral respiratory group found in?
nucleus ambiguos
The neurons of the ventral respiratory group remain….
almost totally inactive during normal quiet respiration
Which respiratory center operates as an overdrive mechanism during heavy exercise?
ventral respiratory group
The hormones of the adrenal medulla are the….
catecholamines
The adrenal medulla is formed from….
neural crest cells
The adrenal medulla itself is a modified neural tissue. The medulla functions like a….
modified sympathetic ganglion (stress response)
