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S2 Bio 109 A&P 2 > PNS II > Flashcards

PNS II Flashcards

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1
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PNS

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All nervous pathways outside the brain and spinal cord - includes fibers present in: cranial nerves, spinal nerves, individual branches of cranial and spinal

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2
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Divsions

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  1. Functional: sensory and motor 2. Motor: somatic motor and autonomic
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3
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Principles of somatice motor pathways

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  • involves the peripheral pathways to the skeletal muscles (somatic effectors) - all somatic motor pathways involve a single motor neuron whole axon stretches from the cell body in the CNS to the effector innervates by that neuron (motor unit) - involves all motor pathways outside of CNS
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4
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Reflex arc

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Signal conduction route to and from CNS - most common are 3 neurons, simplest have 2

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7
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Reflex

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The action that results from a nerve impulse passing over a reflex arc - predictable response to a stimulus - usually involuntary but can be conscious - consists of either muscle contraction or glandular secretion

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8
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Cranial reflex

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Center of reflex arc is located in the brain (eye tracking while reading)

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9
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Spinal reflexes

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Center of reflex arc is located in eh spinal cord (knee jerk)

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10
Q

Somatic reflexes

A

Contractions of skeletal mm - motor neurons are somatic motor neurons 1. Stretch 2. Tendon 3. Flexor (withdrawal) 4. Crossed extensor

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11
Q

Autonomic reflexes

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Contractions of smooth or cardiac mm or secretion by glands

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12
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Why are reflexes important?

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  • clinical interest in reflexes stems from the fact that they deviate from normal in certain diseases/disorders - the testing of reflexes is a valuable diagnostic aid - stretch reflex tests neuromuscular integrity - protective reflex tests cranial nerve integrity
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16
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Knee jerk

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Patellar reflex - stretch reflex - extension of the lower leg in response to tapping the patellar tendon - the tap results in stretch of the tendon and its mm; stimulates the mm spindles - conduction over a 2-neuron reflex arc - femoral nerve and spinal levels L2-4

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18
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Ankle jerk

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Achilles reflex - plantarflexion of the foot in response to tapping the Achilles’ tendon - stretch reflex mediated by 2-neuron spinal arcs - spinal levels s1-s2

19
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Plantar réflex

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Curling under of all toes (plantarflexion) plus a slight turning in and flexion of the anterior part of the foot - in response to stimulation of the outer edge of the sole

20
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Babinski reflex

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  • extension of the great tow, with or without fanning of the other toes - in response to stimulation of the outer margin of the sole of the foot - normal infants show the babinski sign - 18 mo, corticospinal fibers have become fullly myelinated and the babinski sign becomes suppressed
21
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Corneal reflex

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  • blinking in response to the cornea being touched - 5th and 7th cranial nerves, pons
22
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Abdominal reflex

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Umbilicus moves in response to stroking the side of the abdomen - superficial reflex - decrease or absence of this reflex occurs in lesions involving pyramidal tract upper motor neurons - may be absent during pregnancy

23
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ANS divisions

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  • regulates involuntary effectors to maintain homeostasis or respond to threats (internal and external) - heartbeat, smooth mm contraction, glandular secretions, metabolism - contains afferent and efferent components 1. Sypmathetic 2. Parasympathetic - consist of neural pathways that are separate from each other - many autonomic effectors are dally innervates (fibers from both sym and para) which allows the effector to be controlled with remarkable precision
24
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Enteric nervous system

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  • intestinal aspect of ANS - controls visceral effectors in gut wall: endocrine cells, exocrine cells, smooth muscle - can funciton independice y, but is modulated by sympathetic and parasympathetic divisions
25
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Structure of ANS

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  • each efferent autonomic pathway is made up of autonomic nerves, ganglia, and plexuses - all autonomic neurons function in reflex arcs - efferent autonomic regulation ultimately depends on feedback from sensory receptors - some effector organs regulated by ANS include: blood vessels, smooth mm, cardiac mm, sweat glands
26
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Preganglionic neuron

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Conducts impulses from CNS to an autonomic ganglion

27
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Postganglionic neuron

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Wishing the ganglion the pre-ganglionic neuron synapses with a second efferent neuron that conducts impulses away from the ganglion and to the effector

28
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Pic

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30
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Autonomic transmitters

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  • axon terminal of autonomic neurons release one of two neurotransmitters - norepinephrine - acetylcholine
31
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Functions of ANS

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Regulate visceral effectors to maintain or quickly restore homeostasis - both sym and para are tonically active (continually conduct impulses to autonomic effectors) - exert antagonistic influences on visceral effectors - sym impulses tend to stimulate an effector - para impulses tend to inhibit it

32
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Loops

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The more chains involved in the loop the more complex the response and the longer the response takes to cause effect - the shorter the loop the quicker and shorter lasting the response

33
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ANS functions in loops

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  1. Spinal loops: afferent neuron to spinal cord to efferent neuron 2. Brain stem loop: afferent to spinal cord to brain stem to efferent 3. Hypothalamus loop 4. Hypothalamus + limbic system loop
34
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Sym vs para

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Dally innervates effectors continually receive both sympathetic and parasympathetic impulses - summation of the two opposing influences determines the dominating or controlling effect

35
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Functions of the SNS

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  • serves as an emergency system “fight-flight-freeze” - only sym fibers innervates the smooth muscle in blood vessel walls - maintenance of normal vessels tone - crucial role in blood pressure under resting and active conditions
36
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Functions of PSNS

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Primary controller of most autonomic effectors most of the time - dominant during the rest and repair times

37
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Big picture

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  • PNS is made of all afferent nervous pathways coming into the CNS and all the efferent pathways going out of the CNS - peripheral pathways are pathways that lead from he integrator (CNS) to the effectors - allows the CNS to communicate regulatory information to all of the nervous effectors - every major organ is influenced (directly or indirectly) by peripheral nervous system output
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S2 Bio 109 A&P 2 (29 decks)

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