Autonomics Flashcards
The functional unit of the autonomic nervous system is a ___-____ ___ pathway
two-neuron motor
ex: heart rate, sphincter tone, digestion
What is the reflex, regulatory role of the ANS?
homeostasis
This is the site of integration and control for many autonomic functions. It is also the origin of the neuroendocrine, hypothalamic-pituitary axis
hypothalamus
This nervous system is anatomically confined to the GI tract but it is intimately related to both sympathetic and parasympathetic divisions of the ANS.
enteric
Besides homeostasis, what else is the hypothalamus involved in?
emotional behavior and motivational drives
Temperature regulation is a complex process affected by both ____ and ____ ____ changes
hypothalamic; skin temperature
The ____ effects of changes in hypothalamic temperature include alterations in blood flow, sweat production, shivering, metabolism and posture
direct
Changes in skin temperature produce reflex effects which modulate the hypothalamic “set point”. What occurs at this set point?
point at which sweating or shivering will begin
A direct effect of osmolarity exists in the organum vasculosum of the lamina terminals and subfornical organ which lack what?
blood-brain barrier
note: osmoreceptors in this area are extremely sensitive to osmolarity
Reflexy, mouth dryness stimulates thirst via the ______
hypothalamus
Input from sense organs and the neocortex influence a variety of specific hypothalamic and limbic areas to produce complex reflex changes such as?
fear, rage, grief, fight or flight
In regards to sexual behavior, a direct effect of circulating ____ and _____ in the anterior ventral area of the hypothalamus has been shown to stimulate aggressive-receptive behavior in non-human species
estrogens; androgens
True or false? All reflex effects are stimulated by the hypothalamus.
false; reflex effects are stimulated via all sensory systems although not all reflexes are mediated via the hypothalamus
The hypothalamus has direct influence over the _____ to control release of many hormones
pituitary
The hypothalamus sends excitatory and inhibitory signals to the pons and medulla which can control or override normal autonomic homeostatic mechanisms. ____ ____ signals can then modify control via either the hypothalamus or by influences on nuclei in the medulla or pons
peripheral “feedback”
micturition
a pontine micturition center coordinates emptying of the bladder which is otherwise an autonomic reflex.
The medulla is the site of ____ ____ ____ of the circulation.
final global integration
note: it contains several integrating centers that may interact with one another. They all receive information from peripheral receptors and cause reflex adjustments in heart rate and ultimately, blood pressure
In regards to the medulla, a ____ area controls vasoconstriction
vasomotor
In regards to the medulla, _____ and _____ areas are critical in control of heart rate and contractility
cardioinhibitory; cardioacceleratory
Other ANS functions integrated in the medulla include:
respiration, gagging, swallowing, coughing, sneezing, and vomiting
The parasympathetic outflow tracts are characterized by _____ preganglionic neurons and ____ postganglionic neurons
long; short
Where are most of the synapses in the parasympathetic system located?
on or in the target organ
Parasympathetic preganglionic nerves originate in 4 regions. Where does CN III project?
projects to ciliary ganglia and is responsible for lens accommodation and pupillary contraction
Parasympathetic preganglionic nerves originate in 4 regions. Where does CN VII project?
projects to lacrimal and salivary glands via pterygopalatine and submandibular ganglia
Parasympathetic preganglionic nerves originate in 4 regions. Where does CN IX project?
projects to the otic ganglion and parotid salivary gland
The dorsal motor nucleus of the vagus is the origin of CN X which innervates viscera where?
throughout thorax and upper abdomen
The pelvic nerves originating from S2,3,4 innervate the lower abdominal and pelvic viscera and contribute to the regulation of what?
micturition (bladder control), defecation, sexual functions
In regards to sympathetic outflow, signals from cells in the hypothalamus and brainstem descend the spinal cord in cells of the ____ _____ ____
intermediolateral cell column (IML)
Axons in the IML synapse with sympathetic preganglionic neurons in the thoracolumbar region. The sympathetic preganglionic fibers project in 3 ways. Describe.
- may synapse in adjoining chain ganglion (paravertebral projection)
- may extend up or down before synapsing (paravertebral projection)
- may pass outside the chain to their synapse (prevertebral projections)
Sympathetic preganglionic neurons originate where in the spinal cord?
between T1-L3
Describe the length, myelination status, and fiber type of sympathetic preganglionic neurons.
small, myelinated, B fibers
Ordinarily, sympathetic preganglionic fibers have conduction velocities of ___-___ m/sec
3-15
These are ganglia within the sympathetic chain which lie parallel to the spinal cord.
paravertebral ganglia
These ganglia lie outside the sympathetic chain and include the celiac, superior, and inferior mesenteric ganglia in the abdomen
prevertebral ganglia
Adrenal medullae behave like two giant sympathetic ganglia. Preganglionic fibers project directly to the adrenal gland where they synapse on ____ cells which release Epi and NE into the blood
chromaffin cells
Describe the length, myelination status, and fiber type of sympathetic postganglionic neurons
long, unmyelinated, C fibers
What is the postganglionic to pregnaglionic neurons ratio in the enteric nervous system?
10^5 : 1
note: one autonomic fiber can influence thousands of enteric fibers
Physiologically the autonomic nerves are crucial for the coordinated function of the enteric control of what?
muscular and secretory activity
In regards to autonomic transmitter-receptor interaction, the magnitude of response is directly related to what 2 things?
- number of receptors available
2. transmitter concentration
____ is the cholinergic transmitter
Ach
Ach is released by axon endings of all preganglionic neurons in the ANS. This is _____ transmission and includes the parasympathetic and sympathetic fibers
synaptic
Ach is released by axon endings of somatic motor neurons to ____ _____
skeletal muscle
Ach is released by axon endings of parasympathetic postganglionic neurons. This is _____ _____ transmission
neuroeffector junction
Ach is released by axon endings of sympathetic postganglionic neurons to eccrine type sweat glands. These are referred to as _____-____ fibers
sympathetic-cholinergic
What is the principle adrenergic transmitter?
NE
NE is released by what?
most sympathetic postganglionic neurons at the neuroeffector junction; adrenal medulla
In regards to nonadrenergic/noncholinergic, this is the first substance proven to play a role in the ANS. It is released by some interneurons in autonomic ganglia and is released by some postganglionic parasympathetic neurons in the gut
VIP (vasoactive intestinal peptide)
Where are nicotinic receptors found?
- cell bodies of all postganglionic neurons
- motor end plates of skeletal muscle
- effector organs
Where are alpha and beta adrenergic receptors found?
on effector organs and on postganglionic axon terminals
Nicotinic receptors are cholinergic receptors stimulated by nicotine. How does this receptor work?
a pore forms when 5 subunit complex responds to nicotine
There are two types of cholinergic - Nicotinic receptors, Nm (N1) and Ng (N2). Where are they found?
N1: neuromuscular junction;
N2: autonomic ganglia and in the adrenal medulla
What competes for the N1 receptor?
curare competes with Ach
What competes for the N2 receptor?
Hexamethonium
Muscuarinic receptors are cholinergic receptors stimulated by muscarine. How do these receptors work?
operate through G-proteins and second messengers
Where are muscarinic receptors found?
only on visceral organs
What competes for muscarinic receptors?
atropine
In regards to muscarinic receptors where are M1, M2, and M3 found?
M1: glands
M2: heart and smooth muscle
M3: smooth muscle and secretory glands
Adrenergic receptors are stimulated by NE and Epi. They are sub-classed on the basis of _____ _____
selective antagonists (blockers)
Alpha adrenergic receptors. What are they stimulated by? What competes for them? Where are the two types?
- stimulated by Epi, NE, and PE
- Phentoalmine competes and blocks effects of receptor stimulation
- Alpha 1 (post junctional); Alpha 2 (pre or post junctional)
Beta adrenergic receptors. What are they stimulated by? What competes for them? What are the 3 types?
- stimulated by Epi, NE, and ISO
- propranolol competes and blocks effects of receptor stimulation
- Beta 1 (heart and kidney), Beta 2 (elsewhere), Beta 3 (fat cells)
When does up regulation of adrenergic receptors occur?
when there is increased receptor number which leads to increased responsiveness of the tissue
When does down regulation of adrenergic receptors occur?
when there is decreased receptor number making the tissue less response to stimulation
What is the cholinergic mechanism?
- Ach is released from nerve ending
- APs induce influx of Ca2+ - trigger release of Ach from synaptic vesicles
- Ach activates muscarinic receptors on effector organ
After muscarinic receptors on the effector organ have been activated, Ach is degraded by what enzyme? What are the two products?
acetylcholinesterase; acetate; choline
Some choline is take up directly by the nerve ending and acetate passes into capillaries and reappears in the nerve ending as ____
Acetyl-CoA
The enzyme ____ ____ catalyzes the production of Ach
choline acetyltransferase
What is the rate limiting step of the cholinergic mechanism?
reuptake of choline
In regards to adrenergic transmitters, ____ is released from adrenergic postganglionic neurons
NE
In regards to adrenergic transmitters, ____ is the major hormone of the adrenal medulla
Epi
In regards to adrenergic transmitters, ____ is released from small, intensely fluorescent cells to produce an IPSP in autonomic ganglia.
Dopamine
note: plays role in regulation of renal blood flow but is the dominant transmitter within the CNS
In regards to adrenergic transmitters, ____ is co-released form postganglionic vasoconstrictor neurons and contributes to vascular constriction
ATP
In regards to adrenergic mechanisms, biosynthesis of ____ occurs within adrenergic nerves and the adrenal medulla
catecholamines
Adrenergic nerves have two storage pools for NE and Epi. The cytoplasmic pool regulates ___ ____ activity
tyrosine hydroxylase
As NE and Epi accumulate, tyrosine hydroxylase is ____
inhibited
In the cytoplasmic pool, Catecholamines can be degraded by ____ ____
monoamine oxidase (MAO)
note: this contributes to stability of the pool
In the cytoplasmic pool pre junctional alpha2 receptors contribute to the concentration of ____ by inhibiting its release
NE
Adrenergic nerves have two storage pools for NE and Epi. The intragranular pool is in equilibrium with the cytoplasmic pool. It is released when what happens?
AP in nerve allows Ca2+ movement in nerve terminal
note: ATP, NPY, and dopamine are also released
In regards to storage of NE and Epi, ____ selectively stimulates Epi synthesis by inducing the N-methyltransferase
cortisol
What causes release of NE by postganglionic neurons?
AP -> Ca2+ influx -> exocytosis of granules
At released from preganglionic neurons acts on N2 receptors of chromaffin cells, causing depolarization. What does this induce?
Ca2+ influx -> exocytosis of granules
In regards to adrenal medulla hormones causing release, Epi and NE are released into the blood at a ratio of __:__
4:1
The parasympathetic system generally conserves and restores energy and is therefore, _____
anabolic
Effects of parasympathetics can be characterized generally by DEM BBLUES
defecation
emesis
miosis
bradycardia bronchoconstriction lacrimation urination erection salivation
The sympathetic system generally burns energy and provides adjustments in dealing with physiological stress and is therefore, ____
catabolic
The erection is controlled by the parasympathetic system, but ejaculation is controlled by the sympathetic system. True or false?
true
Production of thick saliva and sweating are effects caused by ____ system stimulation
sympathetic
Alpha1 excitatory responses of Epi, NE, and PE are what?
vasoconstriciton, secretion of thick saliva, sphincter contraction, and ejaculation
second messengers involved: IP3 and DAG or Ca2+
Alpha2 inhibitory responses of Epi, NE, and PE are what?
decreased motility and secretory activity in the GI tract
stimulation of alpha2 receptors ____ adenylate cyclase cAMP production
inhibits
Beta1 excitatory responses due to ISO, Epi, or NE are what?
positive chronotropic and inotropic effects on the myocardium, as well as renin release
Beta2 inhibitory responses due to ISO, Epi, or NE include what?
relaxation of smooth muscle
Beta3 metabolic response due to ISO, Epi, or NE is ____
lipolysis
Stimulation of Beta receptors ____ adenylate cyclase. Beta1 makes more ____ available for contraction/cardiac acceleration; Beta2 increased uptake of Ca2+ into the SR results in smooth muscle _____
activates; Ca2+; relaxation
Autonomic nerves are tonically active at rest. True or false?
true - this allows for fine adjustments up and down
