Ch. 16 The ANS

Skill memories

(cerebral and cerebellar cortex) learned motor behaviors - driving a car

Fact memories

(cerebral cortex) stored bits of information, such as the color of a stop sign

Sensory (afferent) division

*brings* sensory signals *to* CNS from receptors in peripheral tissues and organs. Receptors detect signals.

Motor (efferent) division

*carries* motor commands *from* the CNS to effectors (gland, muscles and adipose tissue). The efferent division has 2 divisions: *somatic and autonomic (visceral)*

Somatic division (voluntary)

*controls skeletal muslce contractions* carry signals from (afferent) or to (efferent) receptors in in the skin, muscles, bones and joints.

Effectors of the ANS

*smooth muscle, cardiac muscle, glands* adipose tissue

Autonomic (visceral) division (involuntary)

- automatically regulates smooth muscle, cardiac muscle, glandular secretions, and adipose tissue at the subconscious level. - carries signals from or to viscera (organs) *The ANS includes parasympathetic and sympathetic division, which commonly have antagonostic (opposite) effects*

Long term memories

-*secondary memories* - long term memories that fade with time and may require effort to recall. -*tertiary memories*- long term memories that are with you for a lifetime Most long-term memories are stored in the cerebral cortex.

Sympathetic postganglionic neurons that release ACh innervate

-Sweat glands of skin -Smooth muscles of blood vessels to skeletal muscles and brain

Higher order functions share three characteristics

1. The cerebral cortex is required for their performance, they involve complex interactions among areas of the cortex and between the cortex and other areas of the brain 2. They involve both conscious and unconscious information processing. 3. Higher order functions are subject to adjustment over time. They are not innate (inborn), fixed reflexive behaviors.

Cellular mechanisms of memory formation and storage include the following:

1. increased neurotransmitter release 2. facilitation at synapses 3. the formation of additional synaptic connections

The ganglionic neurons (of sympathetic division) occur in these 3 locations

1. sympathetic chain ganglia (paired) --> innervated by postganglionic fibers -->*visceral effectors in thoracic cavity, head, body wall, and limbs.* 2. collateral ganglia (unpaired) -> innervated by postganglionic fibers -> visceral *effectors in abdominopelvic cavity* 3. suprarenal medullae (paired) -> through release of hormones into the circulation -> *organs and systems throughout the body (WEIRD ONE)*

How much nicotine ingested or absorbed through the skin can cause poisoning?

50 mg

Memory engram

A single circuit that corresponds to a single memory. Memory engrams form as the result of experience and repetition.

Peripheral nervous system (PNS)

All other nerves outside CNS.• The PNS is divided into sensory (afferent) and motor (efferent) divisions, and each are further divided into somatic and visceral

Neurotransmitters and Parasympathetic Function

All parasympathetic neurons release ACh as a neurotransmitter ▫The overall effect is short-lived, due to the break down of ACh by enzymes ▫Effects on postsynaptic cell can vary widely due to variations in second messengers. ▫Two types of ACh receptors: nicotinic and muscarinic

Receptors of the sympathetic nervous system

Alpha and beta receptors are G proteins, results vary on secondary messengers produced. ▫a1 receptors: excitatory response ▫a2 receptors: Inhibitory response ▫b1 receptors: Excitatory response ▫b2 receptors: Inhibitory response ▫b3 receptors: Adipose stimulation

A progressive disorder characterized by the loss of higher-order cerebral functions is

Alzheimer's disease

Memory consolidation

Conversion from short-term to long-term memory; occurs in the amygdaloid body and hippocampus of the limbic system.

Superior Mesenteric Ganglion (Collateral Ganglia)

Found near the base of the superior mesenteric artery, which provides blood to the stomach, small intestine and pancreas. *Postgangleonic fibers leaving the superior mesenteric ganglion innervate the small intestine and the proximal 2/3 of the large intestine.*

All visceral reflexes are polysynaptic, and they are either long or short.

Long reflex: Control organ as a whole Short reflex: More local, part of an organ

Dual Innervation

Most vital organs receive innervation by both divisions At dual innervation sites, the effects are usually opposing (heart, digestive tract, and lungs), other sites may see separate or complimentary responses.

Sympathetic Chain Ganglia

Postganglionic fibers that control visceral effectors in the body wall, head, neck, or limbs enter the gray ramus and return to the spinal nerve for subsequent distribution. ▫Postganglionic fibers innervating structures in the thoracic cavity form bundles known as *sympathetic nerves* ▫Each sympathetic chain ganglion contains 3 cervical, 10-12 thoracic, 4-5 lumbar, and 4-5 sacral ganglia, plus 1 coccygeal ganglion. ▫Preganglionic neurons are limited to spinal cord segments T1-L2, and have both white and gray rami. ▫Every spinal nerve has a gray ramus that carries sympathetic postganglionic fibers for distribution in the body wall.

Collateral Ganglia

Preganglionic fibers pass through the sympathetic chain without synapsing. ▫Preganglionic fibers that innervate the collateral ganglia from the *splanchnic nerves.* 1. Celiac ganglion 2. Superior mesenteric ganglion 3. Inferior mesenteric ganglion

Sympathetic postganglionic neurons that release NO (Nitrous Oxide) innervate

Smooth muscles of blood vessels to skeletal muscles and brain

Neurotransmitters and Sympathetic Function

Stimulation of sympathetic preganglionic neurons lead to the release of ACh at synapses with ganglionic neurons. ▫Telodendria form branching networks with swollen segments called *varicosities.* ▫Most sympathetic ganglionic neurons release norepinephrine (NE) ▫Effects of NE last a few seconds ▫The effects of NE and E released from the adrenal medulla last even longer.

Higher levels of Autonomic Control

Sympathetic and parasympathetic processes are subject to regulation by the hypothalamus ▫Because the hypothalamus interacts with all portions of the brain, activity in the limbic system, thalamus, and cerebral cortex can have a dramatic effect on autonomic function.

Sympathetic division

The "fight or flight" response -preganglionic fibers from the spinal cord synapse in ganglia *near the spinal cord.* -increased sympathetic activity generally stimulates tissue metabolism and increases alertness. -also decreases digestive and urinary activities.

Parasympathetic division

The "rest and digest" response -preganglionic fibers from the brain and spinal cord synapse in ganglia *very close to (or within) the target organs.* -stimulates visceral activity: digestion and urination for example

Pathway of ANS

Visceral motor nuclei starts in hypothalamus -> travels down to either brain stem or spinal cord --> preganglionic neuron goes to ganglia --> snapses with postganglionic fiber --> communicates to effector (smooth mucle, cardiac or glands)

cAMP is

a second messenger

The neurotransmitter at all synpases and neuromuscular or neuroglandular junctions in the parasympathetic division of the ANS is

acetylcholine

All preganlionic autonomic fibers release ____ at their axon terminals, and the effects are always ____

acetylcholine; excitatory

When a G-protein receptor is activated, it

activates an enzyme, such as adenylate cyclase

Which of the following will result in an inhibitory effect on the target cell?

alpha-2 receptors being stimulated

Autonomic Tone

autonomic motor neurons show a resting level of spontaneous activity, even in the absence of stimuli. ▫Allows for an increase or decrease in activity, providing a wide range of control options.

Visceral reflexes

autonomic reflexes initiated in the viscera. provide automatic motor responses that can be modified, facilitated, or inhibited by higher centers, especially those of the hypothalamus.

Celiac Ganglion (Collateral Ganglia)

commonly consists of a pair of interconnected masses of gray matter located at the base of that artery, may alsoform a single mas or many small interwoven masses. *Postganglionic fibers from this galnglion innervate the stomach, liver, gallbladder, pancreas and spleen.*

States of Consciousness

conscious individuals are awake and alert, unconscious individuals are not. There are many gradation levels of both states. Sleep- unconscious but can still be awakened by normal sensory stimuli, two general levels of sleep are recognized; deep sleep and REM sleep. -Periods of REM and deep sleep alternate throughout the night. -Roughly 25% of the US population has a sleep disorder. ▫Arousal- awakening from sleep, one of the functions of the RAS. -the center of the RAS is located in the mesencephalon -stimulation of the RAS will result in activity of the cerebral cortex and other brain areas. -inhibition of the RAS will result in lethargy and sleep.

Visceral reflex arc

consists of a receptor, a sensory neuron, a processing center, and two visceral motor neurons.

Which of the following is *NOT* a result of parasympathetic activation? A. constriction of pupils B. lowered strength in heart contractions C. decreased stimulation of salivary glands D. lessened airflow through the lungs E. stimulation of defecation

decreased stimulation of salivary glands

Short term memories (primary memories)

do not last long, but while they last can be recalled immediately.

Which of the following is a *NOT* associated with both the somatic and autonomic nervous systems? A. signals are initiated in the brain B. effectors are skeletal muscles C. efferent divisions D. controls reflexes E. contains motor neurons

effectors are skeletal muscles

Visceral motor neurons in autonomic ganglia are called

ganglionic neurons their axons are called postganglionic fibers.

Which of the following is NOT a result of sympathetic activation? A. increased activity of the respiratory centers of the pons B. temporary insensitivity to painful stimuli C. release of glucose from the breaking down of glycogen D. increased blood flow to the stomach and small intestines E. shivering

increased blood flow to the stomach and small intestines

Effects produced by the parasympathetic branch of the ANS include

increased secretion by digestive glands

The suprarenal medulla is different than other sympathetic ganglia because

its neurotransmitters are actually hormones, being released into the bloodstream

Muscarinic

located at cholinergic neuromuscular or neuroglandular junctions in the parasympathetic division as well as a few cholinergic junctions in the sympathetic division. *G protein receptors, results vary, could be excitatory or inhibitory*

Inferior Mesenteric Ganglion (Collateral Ganglia)

located near the base of inferior mesenteric artery, which supplies the large intestine and other organs in the inferior portion of the abdominopelvic cavity. *Postganglionic fibers from this ganglion provide sympathetic innervation to the kidneys, urinary bladder, terminal segments of the large intestine, and the sex organs.*

Nicotinic

located on both sympathetic and parasympathetic ganglion cells, as well as neuromuscular junctions of the somatic nervous system. *always excitatory response*

Supradrenal Medullae

modified sympathetic ganglion ▫preganglionic fibers synapse on neuroendocrine cells, specialized neurons that secrete hormones (epinephrine and norepinephrine) into the blood stream. ▫cells not innervated by postganglionic fibers are affected ▫effects last much longer than direct innervation.

The autonomic division of the nervous system directs

processes that maintain homeostasis

During sympathetic activation, a person may begin to feel "on edge"; this is the result of

stimulation of the reticular activating system (RAS)

Memory

stored bits of information gathered by experience

A postganglionic sympathetic fiber innervates the smooth muscle of the small intestine. Which of the following locations did it most likely synapse with its preganglionic fiber?

superior mesenteric ganglion

The division of the ANS that prepares the body for activity and stress is the _____ division

sympathetic

The ANS contains two major subdivisions

the sympathetic and parasympathetic divisions.

Dual innervation refers to situations in which

vital organs receive instructions from both sympathetic and parasympathetic fibers

The Sympathetic Division

▪Preganglionic neurons are located in lateral gray horn between segments T1 and L2 of the spinal cord ▪Cell bodies of preganglionic neurons are situated in the lateral gray horns, and their axons enter the ventral roots of these segments. ▪Ganglionic neurons are located in ganglia near the vertebral column

The Parasympathetic Division

▪Preganglionic neurons are located in the *brain stem and in the sacral segments of the spinal cord* ▪Ganglionic neurons are in peripheral ganglia within or adjacent to the target organs.

Parasympathetic Activation- The major effects include

▫Constriction of pupils ▫Secretion of digestive glands; salivary, gastric, duodenal, intestinal, pancreatic, and livers ▫Secretion of hormones that promote the absorption and utilization of nutrients by peripheral cells. ▫Changes in blood flow and glandular activity associated with sexual arousal ▫Increase in smooth muscle activity along digestive tract ▫The stimulation and coordination of defecation ▫Contraction of the urinary bladder during urination ▫Constriction of respiratory passageways ▫Reduction of heart rate and in force of contraction

Anatomy of Dual Innervation

▫Head and neck innervations ▫Thoracic innervations ▫Abdominopelvic innervations ▫Nerves leaving these networks travel with the blood vessels and lymph vessels that supply visceral organs.

Sympathetic Activation - Major Effects Include

▫Increased alertness via RAS ▫Feeling of energy or euphoria ▫Increased activity in the cardiovascular and respiratory centers of the pons and medulla oblongata (increased BP, HR, breathing rate, and depth of respiration) ▫General elevation in muscle tone ▫Mobilization of energy reserves, through the accelerated breakdown of glycogen in muscle and liver cells and release of lipids by adipose tissue