Peripheral Nervous System Part II Study Guide

Question 1

12 cranial nerves

Answer 1

I Olfactory (S): smell
II Optic (S): vision
III Oculomotor (M): eye movement, pupil reflex
IV Trochlear (M): eye movement
V Trigeminal (B): facial sensation; mastication
VI Abducens (M): eye abduction
VII Facial (B): facial expression; taste sensation
VIII Vestibulocochlear (S): equilibrium, balance, hearing sensation
IX Glossopharyngeal (B): movement of tongue + pharynx; taste sensation
X Vagus (B): parasympathetic efferents, sensory afferents of the viscera
XI Accessory (M): movement of trapezius + SCM
XII Hypoglossal (M): movement of tongue

Question 2

All spinal nerves are _______ nerves.

Answer 2

mixed

Question 3

nerve plexus

Answer 3

except for some in the thoracic region, all ventral rami branch and join one another lateral to the vertebral column – this creates cervical, brachial, lumbar, and sacral nerve plexuses

Question 4

phrenic nerve

Answer 4

(C3-C5): innervates the diaphragm

Question 5

median nerve

Answer 5

(C8 -T1 + C5-C7): innervates the flexor muscles of the forearm and the intrinsic muscles of the lateral hand; sensation of the lateral hand

Question 6

ulnar nerve

Answer 6

(C8-T1): innervates the flexor muscles of the forearm and most of the intrinsic muscles of the hand; sensation of the medial hand

Question 7

femoral nerve

Answer 7

sensation of anterior and medial thigh + medial leg and foot; motor innervation of quadriceps, sartorius, pectineus

Question 8

sciatic nerve

Answer 8

(L4-L5, S1-S2): widespread sensation and motor function of the thigh, leg, and foot

Question 9

nervous system is primarily responsible for maintaining homeostasis

Answer 9

Autonomic nervous system

Question 10

effectors of the somatic nervous system

Answer 10

innervates skeletal muscles

Question 11

effectors of the autonomic nervous system

Answer 11

innervates cardiac + smooth muscle and glands

Question 12

efferent pathway of the somatic nervous system

Answer 12

a motor neuron’s cell body is in the cns; a single, thick, myelinated group A axon extends directly to skeletal muscle

Question 13

efferent pathway of the autonomic nervous system

Answer 13

uses a 2-neuron chain to reach effectors
- Preganglionic Neuron: cell body resides in the CNS with a thin, lightly myelinated preganglionic axon extending to a ganglion
- Postganglionic (Ganglionic) Neuron: cell body synapses with preganglionic axon in the autonomic ganglion; a nonmyelinated postganglionic axon extends to the effector organ
- Impulse conduction through the autonomic efferent chain is slower than conduction in the somatic motor system

Question 14

ganglion

Answer 14

a collection of neuronal bodies found in the voluntary and autonomic branches of the peripheral nervous system (PNS)

Question 15

All somatic motor neurons release acetylcholine at their targets, and its effect is always _________.

Answer 15

stimulatory

Question 16

In the autonomic nervous system, preganglionic fibers release ___________. Postganglionic fibers release either ___________________ or _____________.

Answer 16

• ACh
• norepinephrine (NE)
• ACh

Question 17

Running through the woods to get away from a bear is an example of the overlap between somatic and autonomic function. Describe the somatic roles in this process. Describe the autonomic roles.

Answer 17

• active skeletal muscles require more Oxygen and glucose, so the ANS speeds up HR and dilates the airways
• SNS to contract muscles to run, ANS to supply oxygen and glucose by contracting heart faster and moving blood from gut into legs —

Question 18

The parasympathetic division of the ANS promotes _____________________-___________________________

Answer 18

maintenance functions and conserves energy.

Question 19

the sympathetic division of the ANS

Answer 19

mobilizes the body during activity

Question 20

Dual innervation

Answer 20

almost all visceral organs are served by both divisions, but the divisions cause opposite effects (dynamic antagonism) this tightly controls our viscera

Question 21

dynamic antagonism

Answer 21

one division produces an excitatory response and the other system produces an inhibitory response (think heart rate) the divisions go against each other to maintain homeostasis (only rarely dominate each other, which would be in an emergency situation)

Question 22

physiological symptoms of parasympathetic activation

Answer 22

Blood pressure, heart rate, and respiratory rate are low
GI tract activity is high
Pupils are constricted, lenses accommodated for close vision

Question 23

physiological symptoms of sympathetic activation

Answer 23

increased heart rate, dry mouth, cold, sweaty skin, dilated pupils
- During vigorous physical activity: shunts blood to skeletal muscles and heart, dilates bronchioles, causes liver to release glucose

Question 24

In terms of the spinal cord, where do parasympathetic fibers originate

Answer 24

Parasympathetic fibers are craniosacral – originate in the brain and sacral spinal cord

Question 25

In terms of the spinal cord, where do sympathetic fibers originate

Answer 25

Sympathetic fibers are thoracolumbar – originate in the thoracic and lumbar regions of the spinal cord

Question 26

lengths of the pre and post ganglionic fibers in the parasympathetic division

Answer 26

has long preganglionic and short postganglionic fibers

Question 27

lengths of the pre and post ganglionic fibers in the sympathetic division

Answer 27

short preganglionic and long postganglionic fibers

Question 28

locations of ganglia in the parasympathetic and sympathetic divisions.

Answer 28

- Most parasympathetic ganglia are in or near the visceral effector organs - Sympathetic ganglia lie close to the spinal cord

Question 29

How does referred pain happen?

Answer 29

- Visceral sensory neurons can converge on the same second-order sensory neurons that receive input from somatic sensory neurons - Referred pain - visceral sensory neuron of gallbladder shares tract with somatic sensory neuron of the shoulder, causing pain in the gallbladder to be confused

Question 30

what is different about a visceral reflex arc compared to a somatic reflex arc

Answer 30

- Visceral reflex arc has 2 consecutive neurons in its motor pathway - Afferent fibers are visceral sensory neurons – not somatic - Effectors are smooth muscle, cardiac muscles, and glands – not skeletal muscle

Question 31

2 major neurotransmitters of the PNS

Answer 31

Acetylcholine (ACh) and Norepinephrine (NE)

Question 32

Where is ACh released

Answer 32

ACh is released by cholinergic fibers at: All ANS preganglionic axons All parasympathetic postganglionic axons at their synapses with effectors

Question 33

Where is NE released?

Answer 33

NE is released by adrenergic fibers at: Almost all sympathetic postganglionic axons – except for those at sweat glands

Question 34

ACh-binding receptors are called _________ receptors.

Answer 34

cholinergic

Question 35

NE-binding receptors are called __________ receptors.

Answer 35

adrenergic

Question 36

All ACh-binding receptors are either ___________ or ____________.

Answer 36

- nicotinic - muscarinic

Question 37

location of nicotinic receptors

Answer 37

Found on postganglionic neurons – sympathetic and parasympathetic

Question 38

Is the effect of ACh on a nicotinic receptor always stimulatory

Answer 38

The effect of ach at nicotinic receptors is always stimulatory – it opens ion channels and leads to depolarization of the postsynaptic cell

Question 39

muscarinic receptors location

Answer 39

Found on all effector cells stimulated by postganglionic cholinergic fibers - all parasympathetic target organs and a few sympathetic target organs

Question 40

Is the effect of ACh on a nicotinic receptor always stimulatory

Answer 40

The effect of ach can either be inhibitory or excitatory at muscarine receptors – it depends on the subclass of muscarinic receptor - ex. binding of ACh to cardiac muscle cells slows HR, binding of ACh to intestinal smooth muscle increases tract motility

Question 41

2 major classes of adrenergic receptors

Answer 41

alpha and beta

Question 42

NE can either be excitatory or inhibitory – what does it depend on?

Answer 42

which subclass of receptor predominates in the target organ - ex. ne binding to beta1 receptors of the cardiac muscle prods the heart into more vigorous activity, but ne binding to beta2 receptors in the bronchioles smooth muscle causes it to relax

Question 43

How do beta blockers (a very common cardiac medication) work?

Answer 43

Blocks beta receptors and prevents ne from getting in, slows heart rate down and preserves heart for longer

Question 44

Almost all the smooth muscle in blood vessels is entirely innervated by __________ fibers.

Answer 44

sympathetic

Question 45

sympathetic tone

Answer 45

Continual state of partial constriction of blood vessels

Question 46

How does the sympathetic nervous system raise and lower blood pressure?

Answer 46

- When BP drops, sympathetic fibers fire faster than normal to increase blood vessel constriction and elevate BP - When BP rises, sympathetic fibers fire less often than normal to decrease blood vessel constriction and decrease BP

Question 47

Where does the parasympathetic division normally predominate

Answer 47

The heart and the smooth muscle of the digestive and urinary organs – it also activates most glands except for the adrenal and sweat glands

Question 48

Parasympathetic tone

Answer 48

consistent state of slight activation

Question 49

A drug that overrides the parasympathetic response can help with ________________, but it might cause ________________.

Answer 49

- increasing heart rate - fecal + urinary retention.

Question 50

The best example of the sympathetic and parasympathetic divisions of the ANS working together is in the external genitalia. What is the parasympathetic role here? How about the sympathetic role?

Answer 50

- The parasympathetic system dilates blood vessels to produce erection of sexual organs - Activation of the sympathetic system causes ejaculation of semen and reflex contractions of the vagina

Question 51

body areas that are ONLY innervated by the sympathetic division

Answer 51

Adrenal medulla, sweat glands, arrector pili muscles, kidneys, and almost all blood vessels receive only sympathetic fibers

Question 52

How does the sympathetic division regulate our body temperature

Answer 52

- Dilation of skin blood vessels - to allow heat to escape - Activation of sweat glands

Question 53

How does the sympathetic division regulate our metabolic rate

Answer 53

- Increases the metabolic rates of cells - Raises blood glucose levels - Mobilizes fats for use as fuel

Question 54

What part of the CNS is the main integrative center for ANS activity?

Answer 54

Hypothalamus

Question 55

Create an example of the cerebral cortex exerting some influence on the function of the ANS.

Answer 55

Recalling a scary event can make your heart race, thinking about your favorite food can make your mouth water

Question 56

Define Hypertension (high blood pressure) in terms of ANS function.

Answer 56

- Overactive sympathetic vasoconstrictor response to stress - Forces the heart to work harder; artery walls are subject to increased wear + tear - Treated with adrenergic receptor-blocking drugs (beta blockers)

Question 57

Define Raynaud’s Disease in terms of ANS function.

Answer 57

- Painful, exaggerated vasoconstriction in fingers + toes - Digits turn pale, then cyanotic - Provoked by cold or emotion; treated with vasodilators