Ch. 15: The Autonomic Nervous System

How does the ANS operate

Via reflex arcs without conscious control

What is difference between somatic nervous system & autonomic?

Autonomic has ganglia, no UMN/LMN/LCN instead has pre/postganglionic neurons

The ANS receives sensory from

Interoceptors

The afferent information of the ANS are mostly

Subconsciously perceived visceral sensations

The sympathetic division

Excites

The parasympathetic division

Relaxes

What is dual innervation?

Most organs receive impulses from both sympathetic and parasympathetic fibers

Preganglionic neurons have

Its cell body in the CNS, myelinated axon extends to autonomic ganglion or chromaffin cells

Postganglionic neurons have

Its cell body in the autonomic ganglion, unmyelinated axon extends go effector

What regulates balance between sympathetic & parasympathetic?

Hypothalamus regulates the autonomic tone

What is autonomic tone

Total activity rate of the ANS, balancing the 2 divisions

How are autonomic responses subconscious?

Because control centers are in lower brain areas, now cerebral cortex

What are the inputs to the hypothalamus

Emotions & visceral sensory information

What are the outputs from the hypothalamus

Nuclei in brainstem (cranial nerves), spinal cord (nerves), to preganglionic neurons

The sympathetic preganglionic neurons are called

The thoracolumbar division

Preganglionic neurons in the thoracolumbar division are located in

Lateral greyhorns

Sympathetic ganglia are the

Sympathetic trunk ganglia or prevertebral ganglia

Sympathetic preganglionic neurons are divergent meaning

Axons may synapse with many postganglionic neurons in different ganglia

The sympathetic trunk ganglia lie on

Either side of the spinal cord, short preganglionic & long postganglionic neurons

The sympathetic trunk ganglia mostly innervate

Organs above the diaphragm

Prevertebral ganglia lie

Anterior to vertebral column

Prevertebral ganglia mostly innervate

Organs below the diaphragm

Sympathetic preganglionic synapses with postganglionic, what are the different options

Synapses in ganglion at the same level, high or lower ganglion, in prevertebral ganglion or chromaffin cells in suprarenal medulla

Where do preganglionic neurons synapse?

White communicating ramus

The white communicating ramus connect

The spinal nerve to ganglia of sympathetic chain

Where do postganglionic in sympathetic chain ganglia enter?

Grey communicating rami

The postganglionic neuron from the grey communicating rami go to

Visceral effector organs

In the sympathetic, 1 preganglionic neuron can synapse with

20 postganglionic neuron, supplying main body regions

Preganglionic axons that pass through the sympathetic trunk w/o synapsing form

Splanchic nerves that extend to prevertebral ganglia and suprarenal medulla

Splanchnic nerves in suprarenal medulla synapse with

Chromaffin cells

Chromaffin cells secrete

Epinephrine & NE

Axons of postganglionic neurons exit in what ways?

Joining spinal nerves (grey rami), form cephalic periarterial nerves, form sympathetic nerves, form splanchnic nerves

Parasympathetic preganglionic neurons have

Its cell bodies in cranial nerve nuclei (3,7,9,10), lateral grey matter

The parasympathetic preganglionic neurons are called

The craniosacral division, long preganglionic, short postganglionic

Parasympathetic preganglionic axons emerge as part of a

Cranial nerve of as part of the anterior root of the sacral spinal nerve (pelvic splanchinic nerve)

All preganglionic neurons in the parasympathetic synapse with postganglionic neurons in

Terminal ganglia, located very near or in effector organ

Parasympathetic preganglionic neurons can only synapse

With 4-5 postganglionic neurons, specialized localized response

Parasympathetic preganglionic axons from cranial nerves form

Cranial parasympathetic outflow

Parasympathetic preganglionic axons that exit as sacral spinal nerves form

Sacral parasympathetic outflow

Neurons of the ANS are classified as either

Cholinergic of Adrenergic

Cholinergic ANS neurotransmitters release

Acetylcholine (Ach)

Cholinergic ANS neurons are

All preganglionic neurons, all parasympathetic postganglionic neurons, sympathetic postganglionic neurond supplying sweat glands

Ach can cause

Excitation or Inhibition

Acetycholine is quickly degraded by

Acetycholinesterase

Cholinergic receptors are either

Nicotinic or Muscarinic

Nicotinic receptors cause

Excitation of postsynaptic cell (ionotropic)

Nicotinic receptors are found on

Dendrites & cell bodies of sympathetic & parasympathetic postganglionic neurons; chromaffin cells

Muscarinic receptors are found on

All parasympathetic receptors, sweat glands innervated by cholinergic sympathetic nerves

Muscarinic receptors cause

Excitation or Inhibition (metabotropic)

Ach can bind go both

Nicotinic & Muscarinic

Adrenergic releases

Norepinephrine (NE)

NE can cause

Excitation or Inhibition

Adrenergic receptors are found in

Most sympathetic postganglionic neurons

Norepinephrine lingers at synapse until

Enzymatically inactivated by monoamine oxidase or catechol-O-methytransferase

Why are NE effects longer lasting than cholinergic neurons?

Because NE is able to linger while Ach is quickly degraded

Norepinephrine is released as a

Neurotransmitter & hormone

Epinephrine is released as a

Hormone

NE & epinephrine bind to

Adrenergic receptors

An agonist

Mimics neurotransmitter of hormone, activates receptor

An antagonist

Prevents neurotransmitter or hormone function, blocks a receptor

What will stimulate gut motility after surgery?

Muscarinic Ach receptor agonists

What will dilate pupils?

Muscarinic Ach receptor antagonists

What will promote bronchodilation?

Adrenergic receptor agonists

What will protect following a myocardial infarction?

Adrenergic receptor antagonists

What will release dopamine?

Adrenergic agonists

Sympathetic responses dominate during

Situations of physical or emotional stress

Examples of sympathetic responses

Dilation of pupils, increase hr/bp/bf to skeletal/cardiac muscles, decreased blood flow to GI/kidney

Parasympathetic system dominates in

Times of rest

Parasympathetic conserve & restore body energy through

SLUDD: Salivate, lacrimate, urinate, defecate, digest

Examples of parasympathetic responses

Decreased hr, airway & pupil diameter