PNS II

Question 1

PNS

Answer 1

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

Question 2

Divsions

Answer 2

1. Functional: sensory and motor 2. Motor: somatic motor and autonomic

Question 3

Principles of somatice motor pathways

Answer 3

• 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

Question 4

Reflex arc

Answer 4

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

Question 5

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Question 6

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Question 7

Reflex

Answer 7

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

Question 8

Cranial reflex

Answer 8

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

Question 9

Spinal reflexes

Answer 9

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

Question 10

Somatic reflexes

Answer 10

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

Question 11

Autonomic reflexes

Answer 11

Contractions of smooth or cardiac mm or secretion by glands

Question 12

Why are reflexes important?

Answer 12

• 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

Question 13

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Question 14

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Question 15

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Question 16

Knee jerk

Answer 16

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

Question 17

Answer 17

Question 18

Ankle jerk

Answer 18

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

Question 19

Plantar réflex

Answer 19

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

Question 20

Babinski reflex

Answer 20

• 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

Question 21

Corneal reflex

Answer 21

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

Question 22

Abdominal reflex

Answer 22

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

Question 23

ANS divisions

Answer 23

• 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

Question 24

Enteric nervous system

Answer 24

• 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

Question 25

Structure of ANS

Answer 25

- 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

Question 26

Preganglionic neuron

Answer 26

Conducts impulses from CNS to an autonomic ganglion

Question 27

Postganglionic neuron

Answer 27

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

Question 28

Pic

Answer 28

Question 29

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Question 30

Autonomic transmitters

Answer 30

- axon terminal of autonomic neurons release one of two neurotransmitters - norepinephrine - acetylcholine

Question 31

Functions of ANS

Answer 31

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

Question 32

Loops

Answer 32

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

Question 33

ANS functions in loops

Answer 33

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

Question 34

Sym vs para

Answer 34

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

Question 35

Functions of the SNS

Answer 35

- 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

Question 36

Functions of PSNS

Answer 36

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

Question 37

Big picture

Answer 37

- 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

Question 38

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Question 39

Answer 39