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Chapter 16
The Autonomic Nervous System and Higher-Order Functions
91
Anatomy
Undergraduate 2
12/03/2017

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Term
Somatic nervous system
Definition
Operates under conscious control

Seldom affects long-term survival

Controls skeletal muscles
Term
Autonomic nervous system
Definition
Operates without conscious instruction

Controls visceral effectors

Coordinates system functions:
cardiovascular, respiratory, digestive, urinary, reproductive
Term
Autonomic integrative centers
Definition
located in hypothalamus

These neurons comparable to upper motor neurons in SNS
Term
Preganglionic neurons
Definition
Visceral motor neurons in the brain stem and spinal cord, they extend to ganglia

Part of visceral reflex arcs-most of their activities represent direct reflex responses

Axons of preganglionic neurons-preganglionic fibers

Leave CNS and synapse on ganglionic neurons (PNS)
Term
Ganglionic neurons
Definition
Visceral motor neurons in peripheral ganglia

-Contain many ganglionic neurons-autonomic ganglia

Axons of ganglionic neurons-postganglionic fibers

Innervate visceral effectors:
cardiac muscle, smooth muscle, glands, adipose tissue
Term
Sympathetic Division
Definition
Increases alertness, metabolic rate, muscular abilities

"Fight or Flight"

Kicks in only during exertion,stress, or emergency
Term
Parasympathetic Division
Definition
Reduces metabolic rate and promotes digestion

"Rest and Digest"

Predominates during resting conditions
Term
7 responses to increased sympathetic activity
Definition
1. Heightened mental alertness
2. Increased metabolic rate
3. Reduced digestive and urinary functions
4. Energy reserves activated
5. Increased respiratory rate and respiratory passages dilate
6. Increased heart rate and blood pressure
7. Sweat glands activated
Term
5 Responses to Parasympathetic activity
Definition
1. Decreased metabolic rate
2. Decreased heart rate and blood pressure
3. Increased salivary and digestive glands secretions
4. Increased motility and blood flow in digestive tract.
5. Urination and defecation stimulation
Term
Enteric Nervous System
Definition
Extensive network in digestive tract walls
-over 100 million neurons

Sympathetic, parasympathetic influence

Many complex visceral reflexes coordinated locally without instruction from CNS
Term
Where are the preganglionic neurons located?
Definition
Between segments T1 and L2 of spinal cord

Cell bodies are located in the lateral gray horns
Term
Where are the ganglionic neurons located?
Definition
In ganglia near vertebral column
Term
In what 3 locations do you find ganglionic neurons?
Definition
1. On both sides of the vertebral column (sympathetic chain ganglia). Control effectors in body wall, thoracic cavity, head, and limbs.

2. anterior to vertebral bodies (collateral ganglia). innervate tissues and organs in abdominopelvic cavity

3. Suprarenal medulla. modified ganglion. Very short axons, release neurotransmitters into the bloodstream, not at a synapse. Function as hormones affecting target cells throughout the body.
Term
Where do sympathetic preganglionic fibers originate?
Definition
from the lateral gray horns
Term
What do ventral roots of spinal segments T1-L2 contain and what do they give rise to?
Definition
They contain sympathetic preganglionic fibers which give rise to myelinated white ramus
Term
What does the white ramus do?
Definition
Carries myelinated preganglionic fibers into a nearby sympathetic chain ganglion.
Term
Sympathetic Chain Ganglia
Definition
Only spinal nerves T1-L2 have white rami

Every spinal nerve has a gray ramus that carries sympathetic postganglionic fibers for distribution in the body wall.
Term
Splanchnic nerves
Definition
preganglionic fibers that innervate collateral ganglia

In dorsal wall of abdominal cavity
Term
Collateral ganglia
Definition
Abdominopelvic viscera receive sympathetic innervation via sympathetic preganglionic fibers that pass through sympathetic chain without synapsing
-synapse in collateral ganglia
Term
General functions of collateral ganglia
Definition
1. Reduce blood flow and energy use by organs that are not important to immediate survival

2. Release stored energy
Term
What 3 collateral ganglia do the splanchnic nerves innervate?
Definition
1. The celiac ganglion-postganglionic fibers from this ganglion innervate the stomach, liver, gall bladder, pancreas, and spleen.

2. Superior mesenteric ganglion-postganglionic fibers innervate the small intestine and the proximal 2/3 of the large intestine

3. Inferior mesenteric ganglion-postganglionic fibers innervate kidney, urinary bladder, terminal portions of the large intestine, and the sex organs
Term
What is the adrenal (suprarenal) medullae?
Definition
It is a modified sympathetic ganglion where preganglionic fibers synapse on neuroendocrine cells
Term
What are neuroendocrine cells?
Definition
specialized neurons that secrete hormones into the bloodstream.

They secrete the neurotransmitters epinephrine and norepinephrine.

Epinephrine (adrenaline) makes up 75-80% of the secretory output.
Term
Changes that happen when sympathetic activation occurs
Definition
Increased alertness, feel "on edge"

feelings of energy and euphoria
(insensitivity to pain)

Increased heart rate, blood pressure,
breathing rate, and depth of respiration

Mobilization of energy reserves
Term
Cholinergic
Definition
Synapses that use ACh as the transmitter
Term
Adrenergic
Definition
Neurons that release norepinephrine
Term
Varicosity
Definition
In the sympathetic nervous system, the telodendria form a branching network, with each branch resembling a string of pearls. Each "pearl" is a swollen segment called a varicosity, and is packed with neurotransmitter vesicles.
Term
Where are the varicosities that release ACh?
Definition
In the body wall, the skin, the brain, and skeletal muscles.
Term
Nitroxidergic synapses
Definition
Release nitric oxide (NO) as a transmitter

Neurons innervate smooth muscles in walls of blood vessels in skeletal muscles and brain

Produce vasodilation and increased blood flow.
Term
2 types of adrenergic receptors
Definition
Alpha receptors (NE more potent)
Beta receptors

These receptors are G-protein receptors
-Activate 2nd messengers via G-proteins
-2nd messenger: chemical messenger that is not a protein (Ca2+, cAMP)
Term
2 types of alpha receptors
Definition
A1:
More common type of alpha receptor
Releases intracellular Ca2+ into cytosol from reserves in ER
Has excitatory effect on target cell

A2:
Lowers cAMP levels in cytoplasm
Has inhibitory effect on target cell
Helps coordinate sympathetic and parasympathetic activities
Term
Where are beta receptors located?
Definition
on the plasma membranes of cells in many organs, including skeletal muscles, lungs, heart, and liver.
Term
3 types of beta receptors
Definition
!. B1: increases metabolic activity

2. B2: triggers relaxation of smooth muscles along respiratory tract, causing respiratory passages to dilate.

3. B3: found in adipose tissue. Stimulation of B3 receptors leads to lipolysis, the breakdown of triglycerides
Term
The parasympathetic Division consists of?
Definition
Preganglionic neurons in the brain stem and in sacral segments of the spinal cord.

Ganglionic neurons in peripheral ganglia within or adjacent to the target organs.
Term
Terminal ganglion
Definition
A ganglion located near the target organ, usually paired.

-
Term
Intramural ganglion
Definition
A ganglion that is embedded in the tissues of the target organ.

-Interconnected masses,clusters of ganglion cells
Term
Major effects of parasympathetic division:
Definition
Constriction of the pupils
Secretion by digestive glands-exocrine and endocrine
The Secretion of hormones-nutrient absorption and utilization
Changes in blood flow and glandular activity-sexual arousal
Increase in smooth muscle activity along digestive tract
Defecation-stimulation and coordination
Contraction of urinary bladder during urination
Constriction of respiratory passageways
Reduction in heart rate and force of contraction
Term
All parasympathetic neurons release ___as a neurotransmitter.
Definition
ACh
Term
What inactivates ACh?
Definition
Acetylcholinesterase (AChE)
Term
Vagus nerve
Definition
Provides preganglionic parasympathetic innervation to structures in:
Neck
Thoracic and abdominopelvic cavity as distal as a distal portion of large intestion

Provides 75% of all parasympathetic outflow

Branches intermingle with fibers of sympathetic division forming plexuses
Term
Pelvic nerves
Definition
Preganglionic fibers in the sacral segments of the spinal cord

Innervate intramural ganglia in the walls of the kidneys, urinary bladder, terminal portions of the large intestine, and sex organs
Term
Signs of nicotine poisoning
Definition
Vomiting, diarrhea, high blood pressure, rapid heart rate, sweating, profuse salivation, convulsions

May result in coma or death
Term
Nicotinic receptors
Definition
On surfaces of ganglionic cells (sympathetic and parasympathetic), causes excitation of ganglionic neuron or muscle fiber
Term
Muscarinic receptors
Definition
At cholinergic neuromuscular or neuroglandular junctions (parasympathetic) and a few cholinergic junctions (sympathetic)

G-protein receptors-effects last longer than nicotinic receptors, response reflects activation or inactivation of specific enzymes, can be excitatory or inhibitory
Term
Muscarine
Definition
Found in mushrooms

Targets parasympathetic neuromuscular or neuroglandular junctions

Signs and symptoms of poisoning:
salivation, nausea, vomiting, diarrhea, constriction of respiratory passageways, low blood pressure, slow heart rate
Term
Dual innervation
Definition
Parasympathetic postganglionic fibers accompany cranial nerves to peripheral destinations

Sympathetic innervation reaches same structures by traveling directly from superior cervical ganglia of sympathetic chain
Term
Autonomic plexuses
Definition
A series of nerve networks in the thoracic and abdominopelvic cavities where the sympathetic postganglionic fibers mingle with parasympathetic preganglionic fibers
Term
What do autonomic motor neurons do?
Definition
They maintain resting level of spontaneous activity
Term
Autonomic tone
Definition
Even without stimuli, autonomic motor neurons show a resting level of spontaneous activity. This background level of activity determines an individual's autonomic tone.
Term
When is autonomic tone more important?
Definition
When dual innervation does not occur.
Term
Autonomic tone-no dual innervation
Definition
Blood vessel dilates and blood flow increases

Blood vessel constricts and blood flow is reduced.
Background sympathetic tone keeps muscles partially contracted
Term
Visceral reflexes
Definition
autonomic reflexes initiated in the viscera

They provide automatic motor responses that can be modified, facilitated or inhibited by higher centers, especially those of the hypothalamus.
Term
Consensual light reflex
Definition
Constrict pupils of both eyes
Term
Visceral reflex arc
Definition
Consists of a receptor, a sensory neuron, a processing center (one or more interneurons), and 2 visceral motor neurons
Term
pupillary reflex
Definition
Causes pupils to dilate in the dark
Term
sexual arousal (emotional state)
Definition
Pupils dilate
Term
Long reflexes
Definition
Autonomic equivalent of polysynaptic reflexes
Visceral sensory neurons deliver information to CNS
ANS carries motor commands to visceral effectors
Typically coordinate the activities of an entire organ
Term
Short reflexes
Definition
Bypass the CNS entirely
Involve sensory neurons and interneurons located within autonomic ganglia
Interneurons synapse on ganglionic neurons
Motor commands distributed by postganglionic fibers
Control simple motor responses with localized effects-one small part of target organ
Term
3 characteristics of higher-order functions (memory, learning)
Definition
1. The cerebral cortex is required.

2. They involve both conscious and unconscious information processing

3. They are NOT part of the programmed "wiring" of the brain, subject to adjustment over time.
Term
Fact memories
Definition
Specific bits of information, such as the color of a stop sign
Term
Skill memories
Definition
Learned motor behaviors
-Incorporated at unconscious level with repetition
-Programmed behaviors are stored in appropriate area of brain stem
-Complex skill memories involve the integration of motor patterns in the basal nuclei, cerebral cortex, and cerebellum
Term
Short-term memories
Definition
Do not last long

While they last, the information can be recalled immediately

Contain small bits of information
Term
Long-term memories
Definition
1. Secondary memories: fade with time and require effort to recall

2. Tertiary memories: are with you for a lifetime
Term
Memory consolidation
Definition
The conversion from short-term to long-term memory
Term
Brain regions involved in memory consolidation and access
Definition
Amygdaloid body (amygdala),Hippocampus (2 components of the limbic system)

Nucleus basalis

Cerebral cortex
Term
Damage to the Amygdaloid body and hippocampus may cause ___________.
Definition
Inability to convert short-term memories to new long-term memories

Existing long-term memories remain intact and accessible
Term
Nucleus basalis
Definition
Cerebral nucleus near diencephalon

Plays uncertain role in memory storage and retrieval

Tracts connect with hippocampus, amygdaloid body, and cerebral cortex

Damage changes emotional states, memor, and intellectual functions
Term
Cerebral cortex
Definition
Stores long-term memories
Conscious motor and sensory memories referred to association areas
Occipital and temporal lobes:
Special portions crucial to memories of faces, voices, and words

A specific neuron my be activated by a combination of sensory stimuli associated with a particular individual; called grandmother cells
Term
Cellular mechanisms of memory formation and storage
Definition
Involves anatomical and physiological changes in neurons and synapses

Increased neurotransmitter release

Facilitation at synapses

Formation of additional synaptic connections
Term
Increased Neurotransmitter release
Definition
Frequently active synapse increases the amount of neurotransmitter it stores

Releases more on each stimulation

The more neurotransmitter released, the greater the effect on the postsynaptic neurons.
Term
Facilitation at synapses
Definition
Neural circuit repeatedly activated
Synaptic terminals begin continuously releasing neurotransmitter
Neurotransmitter binds to receptors on postsynaptic membrane
Produces graded depolarization
Brings membrane closer to threshold
Facilitation results affect all neurons in the circuit.
Term
Formation of additional synaptic connections
Definition
Neurons repeatedly communicating

Axon tip branches and forms additional synapses on postsynaptic neuron

Presynaptic neuron has greater effect on transmembrane potential of postsynaptic neuron
Term
Memory engram
Definition
single circuit corresponds to single memory, forms as a result of experience and repetition

Efficient conversion of short-term memory takes at least 1 hour, repetition crucial
Term
Factors of conversion
Definition
Nature, intensity, and frequency of original stimulus

Strong, repeated, and exceedingly pleasant or unpleasant events likely converted to long-term memories
Term
Deep sleep
Definition
Also called slow-wave sleep or non-REM sleep

Entire body relaxes

Cerebral cortex activity minimal

Heart rate, blood pressure, respiratory rate, and energy utilization decline up to 30%
Term
Rapid eye movement (REM) sleep
Definition
Active dreaming occurs

Changes in blood pressure and respiratory rate

Less receptive to outside stimuli than in deep sleep

Muscle tone decreases markedly

Intense inhibition of somatic motor neurons

Eyes move rapidly as dream events unfold
Term
Nighttime sleep pattern
Definition
Alternates between levels

Begins in deep sleep, lasts about 1-1.5 hours

REM periods average 5 minutes in length, increase to 20 minutes over 8 hours
Term
What impact does sleep have on the CNS?
Definition
Produces only minor changes in physiological activities of organs and systems
Protein synthesis in neurons increases during sleep

Extended periods without sleep lead to disturbances in mental function

25% of U.S.population experiences sleep disorders
Term
Function of the reticular activating system
Definition
Arousal, awaking from sleep
diffuse network in reticular formation extends from the medulla oblongata to the mesencephalon

Output of RAS projects to thalamic nuclei that influence large areas of cerebral cortex

When RAS inactive, so is cerebral cortex; stimulation of the RAS produces widespread activation of the cerebral cortex
Term
Huntington's disease
Definition
Destruction of ACh-secreting and GABA-secreting neurons in basal nuclei

Symptoms appear as basal nuclei and frontal lobes slowly degenerate

Difficulty controlling movements

Intellectual abilities gradually decline
Term
LSD (Lysergic Acid Diethylamide)
Definition
Powerful hallucinogenic drug that affects sensory interpretation and emotional states

Activates serotonin receptors in brain stem, hypothalamus, and limbic system
Term
Depression
Definition
Not enough serotonin, activation blocked

Prozac, Paxil, Zoloft, Luvox, Celexa, slows removal of serotonin
Term
Parkinson's disease
Definition
Inadequate dopamine production causes motor problems
Term
Speed (amphetamines)
Definition
Stimulated dopamine production

Large doses can produce symptoms resembling schizophrenia
Term
Aging and the Nervous system
Definition
A reduction in the brain size and weight
-narrower gyri and wider sulci
-decrease in volume of the cerebral cortex
-larger subarachnoid space

Reduction in number of neurons
-Brain shrinkage linked to loss of cortical neurons
-No neuronal loss in brain stem nuclei

Decrease in blood flow to the brain
Term
Arteriosclerosis
Definition
Fatty deposits in walls of blood vessels

Reduces blood flow through arteries

Increases chances of rupture

May damage surrounding neural tissue

Increase chances of a cerebrovascular accident (stroke)
Term
Lipofuscin
Definition
granular pigment with no known function
Term
Changes in the synaptic organization of the brain due to aging
Definition
The number of dendritic branches, spines, and interconnections decreases, synaptic connections are lost

The rate of neurotransmitter production declines
Term
Intracellular and Extracellular changes in CNS neurons due to aging
Definition
Neurons in brain accumulate abnormal intracellular deposits:

Lipofuscin-granular pigment with no known function


Neurofibrillary tangles-masses of neurofibrils form dense mats inside cell body and axon

Plaques-extracellular accumulations of fibrillar proteins surrounded by abnormal dendrites and axons

Plaques and tangles contain 2 forms of amyloid B proteins (fibrillar and soluble)
Appear in brain regions specifically associated with memory processing
Term
Anatomical changes linked to functional changes
Definition
Neural processing becomes less efficient with age
Memory consolidation more difficult
Secondary memories harder to access

Sensory Systems:
hearing, balance, vision, smell, and taste become less acute
reaction times are slowed, reflexes weaken or disappear

Motor control:
precision decreases
takes longer to perform
Term
Alzheimer's disease
Definition
Most common cause of senile dementia

abnormal plaques, neurofibrillary tangles in regions associated with memory, emotion, and intellectual function
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