Lecture 15 Flashcards by Danika Boltz

What are the general characteristics of the autonomic nervous system?

-composed of efferent fibers forming a reflex pathway responding to visceral afferents
-visceral information can come from general or specific visceral afferent system

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Which receptors are part of the general visceral afferent system?

-pressure
-stretch
-chemical changes

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Which receptors are part of the specific visceral afferent system?

-taste
-olfaction

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What are the characteristics of ANS control?

-cannot directly control actions of ANS
-independent/autonomous motor system
-actions of ANS are influenced by hypothalamus and reticular formation

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How does the parasympathetic nervous system differ from the sympathetic nervous system on a broad scale?

-parasympathetic NS conserves and stores energy (rest and digest)
-sympathetic NS prepares body for emergency situations (fight or flight)

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How do the activity levels of the PNS and SNS differ?

-PNS is relatively continuously active
-SNS has low resting tone but is capable of bouts of great activity

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What are the characteristics of the two neuron system in the ANS?

-first neuron cell body is in the central nervous system
-first neuron is called preganglionic neuron
-second neuron cell body is in the peripheral nervous system
-second neuron is called the postganglionic neuron

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Where are ALL preganglionic cell bodies located?

PNS (craniosacral):
-CN 3, 7, 9, and 10
-spinal cord segments S1 to S3

SNS (thoracolumbar):
-lateral horn of spinal cord; T1 to L3

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What are the characteristics of the enteric nervous system?

-considered its own nervous system or a branch of the ANS
-contains its own sensory neurons, interneurons, and motor neurons
-functions in gut control
-local reflexes control peristalsis and defecation
-allows paralyzed patients to continue experiencing peristalsis and defecation

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What is a neurotransmitter?

molecule (AA, protein), released by a neuron at the level of the synapse following an action potential

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What is the pathway of function for a neurotransmitter once it is released?

-acting as a chemical messenger ->
-binds to post-synpatic receptors ->
-generates a change in function of target cell

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What are the neurotransmitters in the PNS?

Preganglionic:
-Ach acting upon Ach nicotinic receptors

Postganglionic:
-Ach acting upon muscarinic receptors on effector organs

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What are the neurotransmitters in the SNS?

Preganglionic:
-Ach acting upon Ach nicotinic receptors

Postganglionic:
-norepinephrine/epinephrine acting upon alpha and beta receptors on effector organs

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What are the characteristics of neurotransmitters in the adrenal medulla?

-innervated by sympathetic fibers
-preganglionic neuron secretes Ach
-postganglionic chromaffin cells acting as 2nd neurons secrete epinephrine

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What happens to the epinephrine produced by the adrenal medulla?

-released into blood circulation
-allows for diffuse systemic effects following sympathetic stimulation
-creates the response to stress and threats

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Which tissue is the exception to having both PNS and SNS receptors and instead only has SNS receptors?

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blood vessels

What is the summary for key anatomical features of the PNS?

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-CNS origin is craniosacral
-location of ganglion is terminal/close to organ
-neurotransmitter released by ganglion is Ach
-neurotransmitter released at termination is Ach

What is the summary for key anatomical features of the SNS?

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-CNS origin is thoracolumbar
-location of ganglion is distant from organ
-neurotransmitter released by ganglion is Ach
-neurotransmitter released at termination is noradrenaline

How do the PNS and SNS act on the pupils?

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-pupillary constriction is mediated by parasympathetic activation
-pupillary dilation is mediated by sympathetic activation

What is the parasympathetic pathway for pupil constriction?

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light stimulus
optic nerve
optic chiasm (cross over)
optic tract
pretectal nucleus
caudal commissure (cross over)
parasympathetic nucleus III
oculomotor nerve (CN 3)
ciliary ganglion

What is the sympathetic pathway for pupil dilation?

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lateral tectotegmentospinal tract
cervicothoracic ganglion
middle thoracic ganglion
cranial cervical ganglion
postsynaptic nerve

What are the characteristics of the SNS and micturition?

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-storage phase
-originates in thoracolumbar region

What are the characteristics of the PNS and micturition?

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-micturition/peeing phase
-originates in craniosacral region

What are the characteristics of sympathetic innervation of the bladder?

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*hypogastric nerve: L1-L4 in dog, L2-L5 in cat
-beta receptor stimulation relaxes detrusor muscle to store urine
-alpha receptor stimulation constricts internal urethral sphincter
-sensory branches to perceive pain

What are the characteristics of parasympathetic innervation of the bladder?

*pelvic nerve: S1-S3 -Ach receptor stimulation contracts detrusor to evacuate urine -sensory branches sense bladder wall stretch and transmit information to pontomedullary micturition center

What are the characteristics of somatic innervation of the bladder?

*pudendal nerve: S1-S3 -Ach receptor stimulation constricts external urethral sphincter -sensory and motor to external urethral sphincter

How does the brainstem function in micturition control?

*pontine micturition center: -reticular formation -storage and evacuation -receives info. from spinal cord regarding bladder -sends information to bladder via spinal cord

How does the cerebrum function in micturition control?

-conscious control of micturition

How does the cerebellum function in micturition control?

-inhibitory influence on micturition

How does the spinal cord function in micturition control?

-reticulospinal tracts terminate in ventral horn gray matter -provides LMN to bladder

What are the steps to urine storage/sympathetic activity?

-bladder filling puts pressure on sensory branch of pelvic nerve -sensory information is sent to spinal cord, brainstem, and cerebral cortex -facilitation of pudendal nerve to contract external sphincter -facilitation of hypogastric nerve to alpha receptors to contract internal sphincter -facilitation of hypogastric nerve to beta receptors to relax detrusor muscle -inhibition of pelvic nerve to allow detrusor muscle relaxation

What are the steps to micturition/parasympathetic activity?

-full bladder with resultant stretch of detrusor muscle causes ascending sensory info. to travel via pelvic nerve -sensory info. travels to spinal cord, brainstem, cerebellum, and cerebrum -when appropriate to urinate, signal to activate micturition is sent from brainstem down spinal cord via reticulospinal tracts -inhibition of hypogastric nerve beta receptors at detrusor muscle -inhibition of hypogastric nerve alpha receptors at internal sphincter -inhibition of pudendal nerve at external sphincter -facilitation of pelvic nerve to contract detrusor muscle

What are the characteristics of sympathetic innervation and defecation?

-input from hypogastric nerve and L1 to L4/5 spinal cord segments -innervates descending colon, rectum, and smooth muscle of internal anal sphincter -excitatory to internal anal sphincter; inhibitory to descending colon and rectum

What are the characteristics of parasympathetic innervation and defecation?

-input from pelvic nerve and S1 to S3 spinal segments -innervates descending colon and rectum

What are the characteristics of somatic innervation and defecation?

-input from pudendal nerve and S1 to S3 spinal segments -innervated striated muscle of external anal sphincter

What are the steps of normal fecal continence?

-filling of colon/pressure stimulates sensory branch of pelvic nerve -sensory information is sent to spinal cord, brainstem, and cerebral cortex -facilitation of pudendal nerve to contract external anal sphincter -facilitation of hypogastric nerve to contract internal anal sphincter -inhibition of pelvic nerve to relax colon and rectum

What are the steps of defecation?

-full colon results in colon and rectal stretch -ascending sensory information travels via pelvic nerve to spinal cord, brainstem, and cerebrum -if appropriate to defecate, signal to activate defecation is sent from brainstem and down spinal cord via reticulospinal tracts -inhibition of hypogastric nerve to allow colon contraction and internal anal sphincter relaxation -inhibition of pudendal nerve to allow external anal sphincter relaxation -facilitation of pelvic nerve to cause contraction of colon and rectum

Lecture 15 Flashcards

(37 cards)