unit #4d: autonomic nervous system

ch.17: autonomic nervous system

what type of bodily functions does the autonomic nervous system control? give 5 examples.

* unconscious bodily functions
* body temp.
* blood pressure
* heart rate
* breathing rate
* digestion

what are the types of effectors in somatic n.s. vs. autonomic n.s.? which part of the somatic n.s. vs. autonomic n.s. neurons are myelinated?

* somatic n.s.: skeletal muscle effectors
* single efferent nerve fiber, myelinated
* autonomic n.s.: visceral effectors (smooth/cardiac muscles, glands, thoracic/abdominopelvic organs)
* myelinated preganglionic efferent nerves (originates in CNS)
* unmyelinated postganglionic efferent nerves (originates in peripheral ganglia)

what are the 2 ANS subdivisions?

* sympathetic
* parasympathetic

describe the sympathetic division of ANS. what is its saying? what does it prepare the body for?

* “fight-or-flight”; prepared body for stressful, dangerous situations and for exertion

describe the parasympathetic division of ANS. what is its saying? what 3 functions does it focus on?

* “rest-and-digest”; focuses on digestive functions, nutrient absorption, reproductive functions

define dual innervation and the effects the sympathetic vs. parasympathetic subdivisions have.

* innervation of the same organs; however, have opposing effects toward each other
* ex. sympathetic raises heart rate, but parasympathetic decreases heart rate

define enteric division.

network of neurons located in the walls of the digestive tract

in the sympathetic division,

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1. where are cell bodies located? in what spinal cord segments are included?
2. how are its preganglionic and postganglionic fibers different? (hint: refer to length and myelination)
3. what neurotransmitters does its preganglionic vs. postganglionic fibers release, making them what type?
4. does it exude a high or low degree of divergence?

1. cell bodies located in lateral horn of T₁ - L₂ spinal cord segments
2. preganglionic = short and myelinated; postganglionic = long and unmyelinated
3. preganglionic release acetylcholine (ACh) → cholingeric’ postganglionic release norepinephrine (NE) → adrenergic
4. high degree of divergence (1 preganglionic → 30+ postganglionic)

in the sympathetic division, preganglionic fibers synapse with postganglionic neurons in one of what 3 peripheral ganglia?

* chain ganglia
* collateral ganglia
* adrenal medulla

describe chain ganglia. how many paired structures and where are they located? where do their postganglionic fibers innervate?

* 22-23 paired structures located on either side of spinal cord
* postganglionic fibers innervate: body wall, head/neck, limbs, thoracic organs

describe collateral ganglia. how many major collateral ganglia and where are they located in relation to spinal cord? where do their postganglionic fibers innervate?

* 3 major ganglia located anterior to spinal cord
* postganglionic fibers innervate abdominopelvic organs

describe adrenal medulla. how many and where are they located? what do they do when stimulated?

* 2 modified ganglia that sit above kidneys
* release hormones into bloodstream when stimulated

describe the somatic motor/efferent nerve pathway.

* sensory/afferent fibers enter dorsal root → dorsal root ganglion
* then, synapses in posterior gray horn
* motor/efferent cell bodies in anterior horn; fibers exit thru ventral root
* then, travel thru dorsal and/or ventral rami (depending on target’s location in body) to skeletal muscle effectors

describe the sympathetic synapse pathway of a chain ganglia with the target: sweat glands on skin.

1. start from lateral horn of segments T₁ - L₂
2. preganglionic fibers exit thru ventral root
3. enter adjacent chain ganglion thru white ramus communicans (myelinated)
4. preganglionic fiber synapses with postganglionic neuron
5. postganglionic fiber exits ganglion thru gray ramus communicans (unmyelinated)
6. rejoin spinal nerve
7. travel thru dorsal and/or ventral rami (depending on back of body or to limbs) to visceral effectors

describe the sympathetic synapse pathway of a chain ganglia with the target: thoracic organ (heart or lung). what spinal cords segments do these thoracic organs occupy?

1. start from lateral horn of segments T₁ - L₂
2. preganglionic fibers exit thru ventral root
3. enter adjacent chain ganglion thru white ramus communicans (myelinated)
4. preganglionic fiber synapses with postganglionic neuron
5. postganglionic fiber exits ganglion thru sympathetic nerve
6. travels to visceral organ in thoracic cavity (T₁ - T₃)

describe the sympathetic synapse pathway of a chain ganglia with the target: eye. how about if the target was: urinary bladder?

1. start from lateral horn of segments T₁ - L₂
2. preganglionic fibers exit thru ventral root
3. enter adjacent chain ganglion thru white ramus communicans (myelinated)
4. preganglionic fiber travels up to another ganglion, then synapses with its postganglionic neuron
5. postganglionic fiber travels to visceral organ in head (thru ventral ramus)

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* if urinary bladder, same process but preganglionic fiber travels down to another ganglion → postganglionic fiber travels to visceral organ in pelvic area

describe the sympathetic synapse pathway of a collateral ganglia with the target: abdominal organ (stomach). what spinal cord segments does the stomach or intestines occupy?

1. start from lateral horn of segments T₁ - L₂
2. preganglionic fibers exit thru ventral root
3. enter adjacent chain ganglion thru white ramus communicans (myelinated)
4. continues to form splanchnic nerve with other preganglionic fibers
5. preganglionic fibers enter collateral ganglion and synapse w/ postganglionic neurons
6. postganglionic fiber exits ganglion and travels to visceral organ in abdominal cavity (stomach or intestines, occupying T₅ - L₂)

describe the sympathetic synapse pathway of a adrenal medulla with the target: kidney.

1. start from lateral horn of segments T₁ - L₂
2. preganglionic fibers exit thru ventral root
3. enter adjacent chain ganglion thru white ramus communicans (myelinated)
4. preganglionic fiber passes thru chain ganglion & collateral ganglion, continuing descent into adrenal gland
5. preganglionic fiber innervates modified neurons in adrenal medulla
6. adrenal medulla neurons release epinephrine and norepinephrine into bloodstream (longer-lasting effects on entire body)

list 6 effects of sympathetic stimulation.

* increased alertness
* increased heart rate
* pupil dilation
* bronchodilation
* increases breathing rate
* increased energy reserves for ATP production

in the parasympathetic division,

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1. what cranial nerves and spinal segments is it associated with
2. how are its preganglionic and postganglionic fibers different? (hint: refer to length and myelination)
3. what neurotransmitters does its preganglionic vs. postganglionic fibers release, making them what type?
4. does it exude a high or low degree of divergence?

1. associated w/: CN III, VII, IX, X & S₂ - S₄
2. preganglionic = long and myelinated; postganglionic = short and unmyelinated
3. both preganglionic and postganglionic fibers release Ach → both cholingeric
4. low degree of divergence → high specificity and localized effects; 1 preganglionic → 6 postganglionic

what 2 types of ganglia do preganglionic fibers synapse with postganglionic fibers at in the parasympathetic subdivision? describe them both what cranial nerves/spinal cord segments they’re associated with, along with their innervated muscles.

* terminal ganglia: next to target organ
* CN III, VII, IX; innervates lacrimal gland, eye, salivary glands (organs in head)
* intramural gland: within wall of organ
* CN X (thoracic/abdominal organs like heart, lungs, liver, spleen, stomach, small and large intestines)
* S₂ - S₄ (pelvic organs like uterus, penis, ovaries, testes, urinary bladder)

list 7 effects of parasympathetic stimulation.

* pupil constriction
* secretion by digestive organs (salivary, gastric, intestinal glands)
* stimulation of smooth muscle activity in digestive tract
* reduction of heart rate and contraction force
* constriction of respiratory passages
* sexual arousal & stimulation of sex glands (ex. ejaculation)
* increases storage of energy from food/diet

describe visceral reflexes. how do they differ from other reflexes?

* autonomic reflexes initiated in viscera (changes by hypothalamus)
* doesn’t require conscious control
* all polysynaptic; preganglionic and postganglionic fibers, some ganglia in wall of organ → bypass CNS

name and describe the 2 types of visceral reflexes.

* long reflexes: sensory neurons synapse w/ interneurons in spinal cord (CNS), then motor neurons innervate effector thru peripheral ganglion
* short reflexes: sensory neuron synapses w/ interneurons in peripheral ganglion (no CNS), then synapse w/ motor neurons
* ex. stretch receptors in digestive wall innervate smooth muscle → contract; very short pathway w/ no CNS input