Chapter 16 Autonomic Nervous System (ANS) Flashcards
The overall pathway Autonomic Nervous system (ANS) generate visceral effectors
1) general sensory receptor
2) sensory pathways (ch.15)
3) sensory processing centers in brain
4) conscious and subsonscious motor centers in brain
5) motor pathways
* somatic nervous system (SNS) = skeletal muscle
*** autonomic nervous system **(ANS) = visceral effectors
(e.g. smooth muscles, glands, cardiac muscle, adipocytes)\
what are the two divisions of autonomic nervous system?
1) the sympathetic nervous system (SNS)
* the sympathetic division is capable of mobilizing us during extreme conditions (e.g. fear, exercise, anger), and is often called the flight or fight system
* increases heart rate & respiratory rate, catabolism, sweating and dilates our puplis
2) the parasymphathetic nervous system (PSNS)
= the two divisions often oppose one another to maintain our bodily functions
* the parasymphathetic division is capable of slowing us down and conserving energy, and is often called the rest and digest system
* increases digestion, defacation, urination, while decerasing heart rate, breathing rate, and constricts our pupils -> chilling
however, these systems are rarely wrok at extremes. Most often there is a subtle balancing act beween sympathetic & parasymphathtic tone
The functions of autonomic nervous system (ANS)
- routine homeostatic adjustment of physiological systems through ANS reflexes, regulated by centers in the hypothalamus and brainstem
- occurs independently of the Somatic nervous system
What is the autonomic nervous system stimulated by?
- sensory receptors = interoceptors located in blood vessles, visceral organs, muscles and nervous system monitor conditions in the internal environment
(e.g. chemoreceptors - monitor blood pH & CO2 levels, mechanoreceptors -detect the degree of stretch in the walls of organs or blood vessels = barareceptors -
motor neurons that originate in the CNS synapse with visceral motor neurons located in autonomic ganglia outside CNS and provide biofeedback response
* ganglionic motor neurons directly controls visceral effectors (-smooth or cardiac muscles, glands or GI neurons)
* b/c autonomic responses cannot be consciously altered to any great degree, some autonomic responses are the basis for polygraph (“lie detector”) tests
how does a polygraph test work?
it records several ANS-controlled physiological signs including: blood pressure, pulse (HR), respiration rate & skin conductivity (rate of sweat) while the subject is asked and answers a series of questions
where is the location of integrative centers for autonomic activity? (three neuron pathway)
- visceral motor neurons in the hypothalamus, synapse (heading towards visceral organs)
- preganglionic neurons (autonomic nuclei) locations of cell bodies; in CNS (in autonomic nuclei or spinal cord)
- preganaglionic neurons synapse with Ganglionic neurons (post-ganglionic neurons) which synapse on visceral effectors
what is the difference of integrative centers location between somatic system and autonomic system
somatic system: starts at uppoer motor neuron in priamry motor cortex
autonomic system: starts at visceral motor in hypothalamus
what is dual ANS meaning?
most body organs have dual ANS innervation; i.e. receive impulses from both sympathetic & parasympathetic neurons
- however, in some cases, tissues are innervated by only one ANS pathway-which is either on (low, med, or high freq.) or off.
- usually nerve impulses from one division stimulate an organ, & impulses from the other division decrease activity
what does the sympathethic division increase and decrease?
increases metabolic rate
i.e. genates responses assoicated with “fight or flight”
increases
- metabolic rate (by much as 2x) activtates energy reserves
- alertness RAS activity
- breathing (rate & depth)
- heart rate
- blood pressure
- body temperature
- perspiration & goose-bumps
decreases
- digestion
- urinary function
where is the location of preganglionic cell bodies in sympathtic system?
location of preganglionic cell bodies of sympathetic system:
between T1 and L2 of spinal cord in lateral gray horns
* the sympathetic division is called thoracolumbar division, even though sympathetic ganglia extend in the vicinvity o f the cord from the cervical to the saral region
three types of ganlionic cell bodies in sympathetic division
symphathetic chain ganglia
* chain of ganglia running along each side of vertebral column
* innervate visceral effectors located on each side of the body in body wall, thoracic cavity, head, neck & limbs.
* only T1-L2 spinal nerves have white ramin communicantes
cervical (3 pairs), thoracic (11-12 pairs), lumbar (4-5 pairs) and sacral (4-5 pairs)
collateral ganglia
* outside sympathetic chain (usually not paired)
* splanchnic nerves innervates 3 collateral ganglia (celiac, superior & inferior mesenteric)
innervate: a variety of abdominopelvic tissues & organs
adrenal medulla
= suprarenal medullae
- core of adrenal gland: modifed sympathetic ganglion
* nature of ganglionic fibers: short axons, release neurotransmitters into a capillary that act as hormones to affect target cells throughout the body
* pregangionic fibers; the end of it = endocrine cells (specialized ganglionnic neurons) in the adrenal medullae
* it secretes neurotransmitters intog generla circulation
What are the three types of preganglionic fiber pathways: the three directions
a) synapse within the sympathetic chain ganglia with a ganglionic neuron at the same level
b) travel up or down the chain to synapse within the sympathetic chain ganlion with a more superior or inferior ganglionic neuron
c) travel right through the sympathetic chain ganglia to synapse with ganglionic neuron in collateral ganglia or adrenal medulla
what are the target organs of sympathetic chain ganglia (paired)?
p. 21
preganglionic neurons: lateral gray horns of spinal segments T1-L2
Ganglionic neurons: sympathetic chain ganglia (paired)
target organ: visceral effectors in thoracic cavity, ead, body wall and limbs
what is the target organ of collateral ganglia (unpaired)?
preganglionic neurons: lateral gray horns of spinal segments T1-L2
ganglionic neurons: collateral ganglia (unpaired)
target organs: visceral effectors in abdominopelvic cavity
what is the target organ of suprarenal medullae (paired)?
preganglionic neurons: lateral gray horns of spinal segments T1-L2
ganglionic neurons: superenal medullae (paired)
target organs: organs and systems throughout the body
what are the neurotransmitters released by sympathetic postganglionic fibers?
= NE and E
(these cells are said to be adrenergic visceral motor neurons)
- NE: norepinephrine; the mainneurotransmitter released by postganglionic fibers (to speed up the effect)
- E: Epinephrine (adrenaline)
which ganglionic cell body is related in releasing NE and E?
Adrenal medulla cells are said to be neuroendocrine cells horomes = they can release neurotransmitters that act as hormone»_space; those hormones help to prolong the SNS effect
- chemical messengers released by cells of the adrenal medulla once stimulated by sympathetic preganglionic neurons (by ACh)
80% E = Epinephrine (adrenaline)
20% NE = norepinephrine
released by adrenal medulla into the bloodstream.
WHY sympathetic effects lasts longer?
- release of catecholamines (mostly epinephrine) from the adrenal medulla thus enhancing the sympathetic effects via the endocrine system
- norepinephrine is broken down more slowly than acetylcholine
- there are more SNS axon collaterals that synapse with more SNS postganglionic neurons than in the PSNS division
- more visceral effectors have receptors for catecholamines (epinephrine) than for acetycholine
which situation is it when the cells can only respond to a chemical messenger?
cells can only respond to a chemical messenger if they have receptors for that messenger in the cell membrane or inside of the cell
effect of norepinephrine & epinephrine binding to receptors on target cell: stimulate 2nd messengerswithin the cell
the life of sympathetic ganglia
- ganglionic fiber (axon) brancehs into telodendria which have varicosities (swollen enlargements) filled with vesicles of NE (or sometimes ACh or NO, nitric oxide)
- Monoamine oxidase (MAO) recycles used reabsorbed neurotransmitters
- rest of neurotransmitter is broken down by COMT (catechol-O-methyltransferase)
what is the general effect of parasympathetic division?
“rest and digest”
- decreases: metabolic rate, heart rate, bood pressure (=rest)
- increases: motility and blood flow to the digestive tract, urinary function, salivary and digestive glands (=digest)
Parasympathetic division is called the craniosacral division
where is the location of preganglionic cell bodies in parasympathetic division?
Brain stem & sacral segments of the spinal cord
- in nuclei of cranial nerves in the brain stem
- lateral gray matter of 2nd-4th sacral segments of the spinal cord
where is the location of ganglionic cell bodies in parasympathetic division?
terminal ganglia (reallly small) - located near target organ
intramurla ganglia - embedded in the tissues (wall of teh target organs) of the target organ
What does the ANS consist of that is connected by ganglion (unlike the single neuron pathway of the somatic system)?
the ANS consists of a two neuron pathway
the neurons are named preganglionic and postgangliionic
- all preganglionic neurons arise from the CNS and use acetylcholine as a neurotransmitter;
- however, postganglionic cells of the sympathetic division use norepinephrine and postganglionic cells of the parasympathetic division use acetylcholine
what does it happen if the alpha receptors are stimulated by noreplnephrine?
the stimulation of alpha receptors by noreplenphrine, activating enzymes on the inside of the target cell’s plasma membrane
If it’s Alpha 1:
a) second messengers activated
b) release of Ca2+ from ER
c-1) blood vessle & arrector pill smooth muscle contraciton, pupil dilation (e.g. blood vessels vasoconstriction; systemic arterioles)
c-2) gland cell secreation (e.g. bronchial mucus)
if it’s Alpha 2
a) reduction of cAMP levels
b) inhibition of cell (e.g. deceased gastrointestinal & insulin secretions)
what if Beta receptors are stimulated?
the stimulation of beta receptors by epinephrine, triggering changes in the metabolic activty of the target cells.
Beta 1 receptor:
- cardiac muscle stimulation and increased tissue metabolism
Beta 2 receptor:
- relaxation of smooth muscle in respiratory passages and in the blood vessels of skeletal muscle, lungs, heart and skin
Beta 3 receptor:
- release of fatty acids by adipose tissue for metabolic use in other tissue
what are the effects of the binding ACh to nicotinic and musarinic receptors of the parasympathetic division?
-
nicotinic receptor
- nicotinic receptors are used by the sympathetic division in sweating from eccrine (body) sweat glands as well as on postganglionic fibers -
muscarinic receptor
- muscarinic receptors are also used by the sympatheti division in sweating from palms and soles
Nicotine, the highly addictive plant toxin, activates nicotinic receptors in the peripheral nervous system. This means it will facilitate synaptic transmission at all autonomic ganglionic synapses.
what are the functional interaction between sympathetic & parasympathetic division?
usually opposing effects
dual innervation: most vital organs * tissues receive innervations from both SNS and PSNS
exceptions include:
- lacrimal glands (PSNS only)
- sweat glands (SNS only)
(SNS)
- arrector pill muscles
- blood vessels (normally 1/2 dimeter, SNS can vasolidate & vasoconstrict)
- adrenal gland
- respiratory mucus glands
- skeletal muscles
- adipose tissues
what does autonomic motor neuron shows in absence of stimuli?
(autonomic tone)
in absence of stimuli, autonomic motor neurons show a background level of activity from both SNS & PSNS
- various simuli can increase or decrease activity
what are the motor output in visceral reflexes the Autonomic Nervousy system provided?
1) long reflexes - similar to polysynaptic somatic reflexes
2) short reflexes - bypasses CNS (many are ENS) generates simple motor responses on the small target area
what is levels of sympathetic and parasympathetic acticity are controlled largely by? (in spinal reflexes)
(higher levels of autonomic control)
by centers in brain stem that regulate specific visceral functions = hypothalamus controlling
examples: the medulla oblongata contains
- cardiovascular control centers
- respiratory control centers
- digestive centers including: salivation, swallowing
- urinary function
brainstem is in turn controlled by hypothalamus, which interacts with all other parts of brain (e.g. cerebral cortex, limbic system) to integrate SNS and ANS activities
what is the best way to build memories (e.g. when studying for a test?)
chucnking and rehearsal (repetition)
what is the difference ebtween short and long-term memory?
duration of retention
where are long-term memories stored?
cerebral cortex & cerebellar cortex
