Neuro 500 -- ANS & pathology (class 11/12)

Question 1

Autonomic Tone

Answer 1

-most organs receive innervation from both divisions of the ANS, which typically work in opposition to one another

-autonomic tone is the balance between sympathetic and parasympathetic activity

Question 2

What regulates autonomic tone?

Answer 2

Hypothalamus

Question 3

A few structures only receive sympathetic innervation:

Answer 3

-sweat glands
-arrector pili muscles
-kidneys
-spleen
-most blood vessels
-adrenal medullae

-although they don’t have opposition from the parasymp nervous system, they still exhibit a range in responses: an increase in sympathetic tone has one effect and a decrease in sympathetic tone has the opposite effect

Question 4

Sympathetic responses

Answer 4

-pupils dilate
-heart rate, force of heart contraction and BP increases
-airways dilate (faster movement of air into and out of lungs)
-BV to skeletal muscles dilate
-BV to cardiac muscles dilate
-BV to GI tract constrict
-BV to kidneys constrict

-BV to liver dilate
-BV to adipose tissue dilate

Question 5

Parasympathetic responses

Answer 5

Salivation
Lacrimation
Urination
Digestion
Defecation

-decreased heart rate
-decreased diameter of airways
-decreased diameter of pupils

Question 6

ANS sensory input

Answer 6

-from interoreceptors (sensory receptors located in BVs, visceral organs, mm and nn that monitor conditions in the internal environment)

-not usually consciously perceived

Question 7

somatic nervous system motor output

Answer 7

-Primary motor area of cerebral cortex

-voluntary

(with contributions from basal nuclei, cerebellum, brainstem and SC)

Question 8

ANS motor output

Answer 8

-involuntary control from hypothalamus

Question 9

somatic nervous system motor neuron pathway

Answer 9

-one neuron pathway

-somatic motor neuron goes from CNS to skeletal muscle

Question 10

ANS motor neuron pathway

Answer 10

-two neuron pathway

-to chromaffin cells in adrenal medulla

Question 11

somatic nervous system neurotransmitters

Answer 11

-somatic motor neurons only release ACh

-autonomic motor neurons release ACh or NE
—> hormones: NE (norepinephrine) & Epinephrine

Question 12

effectors

Answer 12

-skeletal muscle

vs.

-smooth muscle, cardiac muscle or glands

Question 13

responses

Answer 13

-contraction of skeletal muscle

vs.

-contraction or relaxation of smooth muscle
-increase or decreased rate & force of contraction of cardiac muscle
-increased or decreased secretion of glands

Question 14

anatomy of autonomic motor pathways – main parts

Answer 14

1) Preganglionic neuron

2) Postganglionic neuron

3) Autonomic ganglion

Question 15

1) Preganglionic neuron

Answer 15

-the first neuron in an autonomic motor pathway

-cell body is in CNS

-axon is a type B fiber

-usually goes to an autonomic ganglion and synapses with a postganglionic neuron

Question 16

A fibers

Answer 16

-largest diameter
-myelinated
-brief absolute refractory period
-fast
-sensory neurons, motor neurons to skeletal mm

Question 17

B fibers

Answer 17

-medium diameter
-myelinated
-medium absolute refractory period
-conduct nerve impulses from viscera to CNS
-all preganglionic neurons

Question 18

C fibers

Answer 18

-smallest diameter
-unmyelinated
-longest absolute refractory period
-pain from viscera
-all postganglionic neurons

Question 19

preganglionic neuron …

Answer 19

Thoracolumbar division/sympathetic

Craniosacral division/parasympathetic

Question 20

Thoracolumbar division/sympathetic

Answer 20

-in the sympathetic division, preganglionic neurons have their cell bodies in the lateral horns of gray matter in T1 to L2 (sometimes L3)

—> In the sympathetic system,
the preganglionic axons
travel out from the SC
with spinal nerves T1-L2 (L3)

Question 21

Craniosacral division/parasympathetic

Answer 21

-in the parasympathetic division, cell bodies of preganglionic neurons are in the nuclei of 4 cranial nerves (10, 9, 7, 3) and in the lateral gray matter of S2 to S4

—> In the parasympathetic, preganglionic axons travel out with 4 cranial nn

—> Parasympathetic, preganglionic axons
also travel out the spine in the sacrum

Question 22

2) Postganglionic neuron

Answer 22

-the second neuron in an autonomic motor pathway

-in the PNS

-cell body is in an autonomic ganglion

-type C fiber

-terminates in a visceral effector

Question 23

3) Autonomic Ganglia

Answer 23

-where the preganglionic and post ganglionic neurons synapse

Question 24

Sympathetic division

-the sympathetic division has 2 different groups of ganglia:

Answer 24

1) Sympathetic trunk ganglia

2) Prevertebral ganglia

Question 25

1) Sympathetic trunk ganglia AKA Vertebral chain ganglia/ Paravertebral ganglia

Answer 25

-aka vertebral chain ganglia -aka paravertebral ganglia -lie in a vertical row on either side of vertebral column -the post ganglionic axons from here innervate organs above the diaphragm

Question 26

-the sympathetic trunk ganglia in the neck have specific names:

Answer 26

---> superior cervical ganglia ---> middle cervical ganglia ---> inferior cervical ganglia

Question 27

2) Prevertebral ganglia AKA collateral ganglia

Answer 27

-aka collateral ganglia -they lie anterior to the vertebral column -their post ganglionic axons innervate organs below the diaphragm

Question 28

-5 major prevertebral ganglia:

Answer 28

Celiac ganglion Superior mesenteric ganglion Inferior mesenteric ganglion Aorticorenal ganglion Renal ganglion

Question 29

Parasympathetic division -the parasympathetic division has only one group of ganglia

Answer 29

1) Terminal ganglia

Question 30

1) Terminal ganglia

Answer 30

-most of these are located close to or within the wall of a visceral organ -in the head they have specific names:

Question 31

-in the head terminal ganglia have specific names:

Answer 31

Ciliary ganglion Otic ganglion Pterygopalatine ganglion Submandibular ganglion

Question 32

4 ways sympathetic preganglionic neurons connect with post postganglionic neurons:

Answer 32

1. In the first ganglion it reaches 2. The axon may ascend or descend to a higher or lower ganglion and synapse there 3. The axon may go through the sympathetic trunk (paravertebral) ganglion to synapse in a prevertebral ganglion 4. The axon may pass through the sympathetic trunk (paravertebral) ganglion and prevertebral ganglion to synapse with chromaffin cells of the adrenal medulla

Question 33

SNS & divergence

Answer 33

A single sympathetic preganglionic fiber has many axon collaterals and may synapse with 20+ postganglionic neurons. This is an example of divergence and helps to explain why many sympathetic responses affect almost the entire body simultaneously.

Question 34

does parasympathetic nervous system have divergence?

Answer 34

Not really Parasympathetic preganglionic neurons pass to terminal ganglia near or within a visceral effector. They usually only synapse with 4 or 5 postsynaptic neurons, all of which supply a single effector. So parasympathetic responses are localized to a single effector.

Question 35

Autonomic Plexuses

Answer 35

-tangled networks of axons of sympathetic and parasympathetic neurons -in thorax, abdomen and pelvis -also contain sympathetic ganglia and axons of autonomic sensory neurons

Question 36

autonomic plexus list

Answer 36

Cardiac plexus (in thorax) Pulmonary plexus (in thorax) Celiac (solar) plexus: ---> largest autonomic plexus ---> surrounds celiac trunk ---> contains 2 large celiac ganglia, 2 aorticorenal ganglia, autonomic axons ---> supplies stomach, spleen, pancreas, liver, gallbladder, kidneys, adrenal medullae, testes, ovaries

Question 37

more autonomic plexuses

Answer 37

Superior mesenteric plexus ---> supplies small + large intestines Inferior mesenteric plexus ---> supplies large intestine Hypogastric plexus ---> supplies pelvic viscera Renal plexus ---> supplies renal arteries and ureters

Question 38

4 ways sympathetic postganglionic neurons connect with visceral effectors:

Answer 38

1) spinal nerves 2) cephalic periarterial nerves 3) sympathetic nerves 4) splanchnic nerves

Question 39

1. Spinal nerves

Answer 39

-postganglionic neurons enter a short pathway called the ‘grey ramus’ and then merge with the anterior ramus of the spinal nerve -grey rami communicantes contain sympathetic post ganglionic axons -these axons provide sympathetic innervation to visceral effectors in skin of neck, trunk, limbs (sweat glands, smooth muscle in blood vessels and arrector pili muscles)

Question 40

2. Cephalic periarterial nerves

Answer 40

-axons coming off the superior cervical ganglion leave the trunk by forming cephalic periarterial nerves -these are nerves that extend to the head by wrapping around and following the course of various arteries that pass from the neck to the head -these neurons provide sympathetic innervation to visceral effectors in the skin of the face (sweat glands, blood vessels, arrector pili muscles) and visceral effectors of the head (smooth muscle of the eye, lacrimal glands, pineal gland, nasal mucosa and salivary glands)

Question 41

3. Sympathetic nerves

Answer 41

-axons leave the sympathetic trunk by forming sympathetic nerves that extend to visceral effectors in the thoracic cavity -axons coming off the superior, middle, inferior ganglia and T1-T4 ganglia form sympathetic nerves that enter the cardiac plexus to supply the heart -axons coming off T2-T4 ganglia form sympathetic nerves that enter the pulmonary plexus to supply smooth muscle of the bronchi and bronchioles of the lungs

Question 42

4. Splanchnic nerves

Answer 42

-these are preganglionic neurons that don’t synapse in the sympathetic trunk ganglia – once they leave the trunk they form splanchnic nerves which go to prevertebral ganglia Greater splanchnic nerve Lesser splanchnic nerve Least (lowest) splanchnic nerve Lumbar splanchnic nerve

Question 43

to adrenal medulla

Answer 43

-preganglionic axons go to chromaffin cells in adrenal medullae of adrenal glands -adrenal medullae are modified sympathetic ganglia -chromaffin cells release hormones into blood: ---> epinephrine ---> norepinephrine

Question 44

Horner’s syndrome

Answer 44

Sympathetic innervation is lost when trauma or disease affect the sympathetic outflow through the superior cervical ganglion -ptosis -miosis -anhydrosis -enopthalmos -on the affected side

Question 45

Structure of the Parasympathetic Division (cranial) (Recall: in the head terminal ganglia (of parasympathetic division) have specific names)

Answer 45

Cranial parasympathetic outflow Cell bodies in nuclei in brain stem Preganglionic axons that extend from the brain stem along 4 cranial nerves 4 pairs of ganglia: 1. ciliary ganglia – their post ganglionic neurons supply smooth muscle of the eye 2. pterygopalatine ganglia – their post ganglionic neurons supply nasal mucosa, palate, pharynx and lacrimal glands 3. submandibular ganglia – their post ganglionic neurons supply submandibular and sublingual salivary glands 4. otic ganglia – supply parotid salivary glands

Question 46

*preganglionic axons that leave the brain as part of the vagus nerve carry about ____% of the total craniosacral outflow

Answer 46

*preganglionic axons that leave the brain as part of the vagus nerve carry about 80% of the total craniosacral outflow

Question 47

Structure of the Parasympathetic Division (sacral)

Answer 47

Sacral parasympathetic outflow Cell bodies in lateral gray matter of S2-S4 Preganglionic axons that extend from the anterior roots of S2-S4 spinal nerves Preganglionic axons travel with spinal nerves and then branch off to form pelvic splanchnic nerves Then they synapse with parasympathetic postganglionic neurons in terminal ganglia Post ganglionic neurons innervate smooth muscle and glands in the walls of the colon, ureters, urinary bladder and reproductive organs

Question 48

ANS NEUROTRANSMITTERS & RECEPTORS receptors are integral membrane proteins in plasma membrane of post-synaptic cell

Answer 48

Cholinergic neurons: - release ACh (- ACh is stored in synaptic vesicles and released by exocytosis) Cholinergic neurons: ---> all preganglionic neurons ---> all parasympathetic postganglionic neurons ---> sympathetic postganglionic neurons that innervate sweat glands

Question 49

2 types of cholinergic receptors:

Answer 49

nicotinic receptors muscarinic receptors

Question 50

1. Nicotinic receptors

Answer 50

- sympathetic & parasympathetic post ganglionic neurons - chromaffin cells - motor end plate at NMJ

Question 51

2. Muscarinic receptors

Answer 51

- all effectors innervated by parasympathetic post ganglionic neurons - sweat glands

Question 52

Adrenergic neurons

Answer 52

-release norepinephrine (NE) aka noradrenalin -most sympathetic post ganglionic neurons -NE is stored in synaptic vesicles and released by exocytosis -adrenergic receptors bind to both NE and epinephrine -NE can be released as a neurotransmitter by sympathetic postganglionic neurons or as a hormone by chromaffin cells -epinephrine is released as a hormone by chromaffin cells

Question 53

2 main types of adrenergic receptors

Answer 53

- alpha α - beta β

Question 54

alpha vs beta adrenergic receptors classification

Answer 54

- are further classified into subtypes: alpha 1, alpha 2, beta1, beta2, beta3 - alpha1 + beta1 receptors generally produces excitation - alpha2 + beta2 causes inhibition - beta3 receptors are only on cells of brown adipose tissue, where their activation causes thermogenesis (heat production)

Question 55

adrenergic vs cholinergic neurons effect length

Answer 55

Effects triggered by adrenergic neurons are usually longer lasting than those triggered by cholinergic neurons

Question 56

NE taken up

Answer 56

NE is either taken up by the axon that released it or inactivated by enzymes enzymes e.g.: -COMT (catechol-O-methyltransferase) -MAO (monoamine oxidase)

Question 57

Receptor agonists & antagonists

Answer 57

..

Question 58

receptor agonist

Answer 58

- is a substance that binds to and activates a receptor - so it mimics the effect of a natural neurotransmitter or hormone

Question 59

receptor antagonist

Answer 59

- is a substance that binds to and blocks a receptor - so it prevents a natural neurotransmitter or hormone from exerting its effect

Question 60

Effects of sympathetic stimulation are longer lasting and more widespread that in the parasympathetic system because:

Answer 60

1) Sympathetic postganglionic axons diverge more so many tissues are activated simultaneously 2) Acetylcholinesterase quickly inactivates ACh but NE lingers in the synaptic cleft 3) NE and E secreted into the blood from the adrenal medullae intensify and prolong the responses caused by the neurotransmitter norepinephrine