Exam #4 Flashcards
3 types of cells the ANS controls
smooth muscle cells
cardiac muscle cells
gland cells
where do SNS preganglionic fibers originate
thoracolumbar region of the spinal cord (T1-L2/3)
where do SNS preganglionic cell bodies lie in the spinal cord
intermediolateral horn
where do SNS preganglionic cell fibers pass through in the spinal cord
ventral root
where do SNS preganglionic fibers travel once they leave the spinal canal
pass through white ramus, into one of the ganglia of the sympathetic chain
what can SNS preganglionic neurons do once they are inside the sympathetic chain
synapse with post ganglionic neuron in the ganglion (travel through gray rami to periphery)
Go up or down the sympathetic chain to synapse at another level
exit the chain to an outlying collateral ganglion where they can synapse with a peripheral synpathetic ganglion
where do post ganglionic sympathetic neurons originate
one of the sympathetic chain ganglia
one of the peripheral sympathetic ganglia
5 peripheral sympathetic ganglia
celiac
superior mesenteric
aorticorenal
inferior mesenteric
hypogastric
what is released at the terminal end of the SNS preganglionic neuron
ACh
SNS preganglionic fiber length
short
SNS post ganglionic fiber length
long
what is released at the terminal end of the post ganglionic neuron at synapses with target organ
NE
chromaffin cells
ACh interacts with them to release EPI and NE in the adrenal medulla
catecholamine content released by chromaffin cells
80% EPI
20% NE
how long do hormonal EPI and NE last vs direct stimulation
10x longer
what is the result of SNS stimulation of the liver
glycogenolysis– glucose released into the blood
synthesis of NE
tyrosine+ tyrosine hydroxylase->
DOPA+ decarboxylase->
dopamine+ DBH->
transported into vesicles and converted to NE
3 mechanisms by which NE is removed after the release into the synapse
reuptake into the presynaptic terminals (active transport)
diffusion away from nerve endings
destruction by tissue enzymes (MAO and COMT)
What does the metabolism of NE form
VMA
what is VMA
the major metabolite (80-90%) of NE found in urine
are SNS preganglionic fibers myelinated or unmyelinated
myelinated
preganglionic fiber to postganglionic fiber ratio in SNS
1:20-30
NE negative feedback loop
NE binds in the presynaptic post ganglionic sympathetic nerve terminal to a2 receptors and NE release is decreased
where does PSNS arise from
CN3,7,9,10
sacral segments 1-4
The craniosacral outflow
PSNS preganglionic nerve terminals release _____ which binds to what receptor
ACh
nicotinic
PSNS post ganglionic nerve terminals release ____ which binds to what receptor
ACh
muscarinic
define nerve
bundle of axons
define dendrite
receive incoming signals
the strength of the signal dictates whether the nerve will pass the signal on which is an action potential
at rest, there are more ____ charged ions outside the cell
positively
the inside of the cell has a net ____ charge at rest
negative
what is the membrane potential threshold voltage
-55
what is the membrane potential resting voltage
-70
what are myelin sheaths made of in PNS
schwann cells
gaps in schwann cells are called and what is their impact
nodes of ranvier
jumping from node to node speeds the transmission
what are myelin sheaths made of in the SNS
oligodendrocytes
ACh synthesis
Acetyl-CoA +choline via the enzyme choline acetyltransferase
where is ACh synthesized and stored
synaptic vesicles in axon terminal
how is ACh hydrolyzed
acetylcholinesterase to choline and acetate
choline is reused
SNS solely provides innervation to the (3)
blood vessels
spleen
piloerector muscles
define cholinergic
nerves that operate by using ACh
define adrenergic
nerves that operate using NE
define muscarinic
drugs that mimic the effects of muscarine which activates the PNS (heart, smooth muscle, glands)
define nicotinic
drugs that interact with ganglionic and skeletal muscle synapses and on nerve membranes and sensory endings
where to preganglionic neurons originate
brainstem or spinal cord
where are nicotinic receptors located
on preganglionic fibers in the PNS, SNS, NMJ, and adrenal medulla
what activates nicotinic receptors
ACh and nicotine
ACh binds to the alpha subunit on the receptor-> conformational change-> increased conductance for ___ which leads to a strong inward electrical and chemical gradient for ___ which leads to what
Na+
Na+
depolarization of the postsynaptic cell
where are muscarinic receptors located
post ganglionic fibers in the PNS on the heart, smooth muscle, and exocrine glands
how do muscarinic receptors affect the heart
inhibitory
(blocked by atropine)
how do muscarinic receptors affect the smooth muscle and glands
excitatory
what activates muscarinic receptors
ACh
muscarine
CNIII
oculomotor
CNVII
facial
CNIX
glossopharyngeal
CNX
vagus
which nerve transmits 75% of the PNS
vagus
vagus nerve supplies what(6)
heart
tracheobronchial tree
liver
spleen
kidney
entire GI tract (except distal colon)
length of preganglionic fibers in the PSNS
long
length of the postganglionic fibers in the PSNS
short
preganglionic to postganglionic ratio in the PSNS
1:1-3
all post ganglionic parasympathetic neurons are
cholinergic
all preganglionic parasympathetic neurons are
cholinergic
all preganglionic sympathetic neurons are
cholinergic
postganglionic sympathetic neurons that innervate the sweat glands and blood vessels are
cholinergic
preganglionic sympathetic neurons that arise from the greater splanchnic nerve and innervate the adrenal medulla are
cholinergic
all motor nerves that innervate skeletal muscle are
cholinergic
where are alpha1 receptors located
postsynaptic membrane of sympathetic postganglionic neurons
where are alpha1receptors found (8)
peripheral vasculature
renal vascular smooth muscle
coronary arteries
myocardium
skin
uterus
intestinal mucosa
splanchnic beds
alpha1 receptors mediate what
smooth muscle vasoconstriction
post synaptic alpha 2 responds primarily to what
epi
6 actions of alpha 2 receptors
arterial and venous constriction
platelet aggregation
inhibition of insulin release
inhibition of bowel motility
stimulation of growth hormone release
inhibition of ADH release
4 central actions of alpha 2 receptors
sedation
anxiolysis
analgesia
hypnosis
where are beta 1 receptors located
post synaptic membrane
3 locations of beta 1 receptors
cardiac tissue
kidneys
adipose tissue
what neurotransmitter are beta 1 receptors primarily responsive to
NE
3 actions of beta 1 receptors on cardiac tissue
increase HR, conduction velocity, and contractility
where are beta 2 receptors found
both presynaptic and post synaptic membranes
where are beta 2 receptors lcated
smooth muscle of blood vessels in
skin
muscle
mesentery
bronchi
cardiac tissue
effects of beta 2 activation on smooth muscle
vasodilation, bronchial smooth muscle relaxation, and renal vessel relaxation
cardiac effects of beta 2 activation
increase in HR and contractility
what is the result of presynaptic beta 2 activation
opposes the presynaptic alpha 2
accelerates NE release
what neurotransmitter do beta 2 receptors primarily respond to
Epi
effects of NE on inotropism in the normal heart is mediated by what receptor(s)
beta 1 receptors
inotropic effects of epi are mediated through what receptor(s)
beta 1 and 2 receptors
alpha receptor effect on vessels
vasoconstriction
alpha receptor effect on eyes
iris dilation
alpha receptor effect on intestines
relaxation
alpha receptor effect on intestinal sphincter
contraction
alpha receptor effect on skin
pilomotor contraction
alpha receptor effect on bladder
sphincter contraction
beta receptor effect on vessels
vasodilation
beta receptor effect on heart
cardioacceleration
increased myocardial strength
beta receptor effect on intestines
relaxation
beta receptor effect on uterus
relaxation
beta receptor effect on lungs
bronchodilation
beta receptor effect on bladder
wall relaxation
beta receptor effect on metabolism (4)
thermogenesis
calorigenesis
glycogenolysis
lipolysis
term for measurable, gas filled spaces in the lung
lung volume
term for combination of two or more lung volumes
lung capacity
define expiratory reserve volume
volume of gas that can be maximally exhaled from the end-expiratory level
normal expiratory reserve volume
1L or 2x Vt
define inspiratory reserve volume
volume of gas that can be maximally inhaled from the end-inspiratory level
normal inspiratory reserve volume
2L or 6x Vt
define residual volume
volume of gas remaining in that lung after maximal exhalation
fick’s law
rate of diffusion through sheet of tissue is proportional to:
issue area
difference in gas partial pressures b/w the 2 sides and
solubility
inversely proportional to:
tissue thickness
molecular wt
CO2 vs O2 diffusion
CO2 diffuses 20x faster than O2 d/t increased solubility and equal molecular weight
define functional residual capacity
volume of gas present in the lung at end expiration during tidal breathing
FRC= ERV+RV
normal functional residual capacity
2-2.5L
define inspiratory capacity
max vol. of gas that can be inspired
IC=IRV+VT
define vital capacity
the volume change between max inspiration and expiration
VC= IRV+VT+ERV
define total lung capacity
sum of all volume compartments
TLC=IRV+VT+ERV+RV
define alveolar ventilation
the amount of fresh gas that gets to alveoli
define dead space ventilation
portion of ventilation that does not participate in gas exchange
define minute ventilation
volume exhaled with each breath * RR/min= minute ventilation
define anatomic dead space
the volume of the conducting airways
how much is anatomic dead space
150mL
define alveolar dead space
volume of the alveoli where normal gas exchange takes place, but due to disease or trauma, is not able to do so
define physiologic dead space
the total volume of the lung that does not eliminate CO2
normal alveolar ventilation
4.2L/min
500mL inhaled - 150mL anatomic dead space= 350 in gas exchange *12RR= 4.2L
which alveoli are better ventilated
dependent areas
pleural pressure and compliance of upper zone
less pleural pressure, distended more, less compliant
pleural pressure and compliance of lower zone
more pleural pressure, less distended, more compliant
fick’s law equation
R= (D A ∆p)/d
R= rate of diffusion
D=diffusion constant
A= area over which diffusion occurs
∆p= difference in pressure between the two sides
d= distance over which diffusion occurs
3 characteristics of pulmonary vasculature
low pressure
highly elastic
vessel walls thin
how much of the circulating blood volume is in the pulmonary circulaiton
10%
normal mPAP
15
normal PAP
25/8
normal pulmonary capillary pressure
8-10
normal LA pressure
5
normal LV pressure
120/0
normal systemic capillary pressure
30
20
10
4 determining factors of pulmonary circulation pressure
cardiac output
pulmonary arterial pressure
pulmonary vascular resistance
left atrial pressure (pulmonary venous pressure)
what happens when alveolar pressure>capillary pressure
alveoli collapse
define transmural pressure
pressure difference between the inside and outside of the capillaries
normal mean pressure in the pulmonary venous circulation
6-12
what does the pulmonary venous pressure waveform look like
CVP/PA wedge
resistance is ______ in the pulmonary circulation than systemic circulation
more evenly spread
which zone is PA>Pa>Pv
zone 1
which zone is Pa>PA>Pv
zone 2
which zone is Pa>Pv>PA
zone 3
which zone is blood flow tamponaded by alveolar pressure
zone 1
which zone is ventilated but not perfused (alveolar dead space)
zone 1
what conditions does zone 1 occur
reduced arterial pressure (septic shock, hemorrhage)
alveolar pressure elevated (positive pressure ventilation)
what is the waterfall effect
arterial pressure is increasing down the zone but alveolar pressure stays the same so the pressure difference responsible for flow increases moving downward
which zone is blood flow determined by the difference between arterial and alveolar pressures
zone 2
which zone is flow determined by the arterial-venous pressure difference
zone 3
in zone 3, the pressure inside capillaries _____ down the zone, while the pressure outside (alveolar) remains constant which results in _________
increases
rising transmural pressure
3 causes of zone 4
PE
mitral stenosis
pulm. edema
what is zone 4
lung has positive interstitial pressure
in zone 4, flow depends on what
difference between arterial pressure and interstitial pressure
which zone has a high V/Q ratio
zone 1
which zone has a low V/Q ratio
zone 4
define absolute pulmonary shunt
whats the V/Q ratio?
perfusion with no ventilation
V/Q=0
what are the O2 and CO2 levels in absolute pulmonary shunt
O2 decreased
CO2 increased
define absolute physiological dead space
whats the V/Q ratio?
ventilation with no perfusion
V/Q= infinity
what is the average V/Q
0.8
define hypoxemia
low concentration of o2 in the arterial blood
define hypoxia
inadequate delivery of o2 to the tissue
example of hypoxemia without hypoxia
mountain climber at the summit of Mt. Everest
example of hypoxia without hypoxemia
cardiogenic shock
4 causes of hypoxemia
hypoventilation
diffusion limitation
shunt
ventilation-perfusion inequality
2 causes of hypercapnia
hypoventilation
ventilation-perfusion inequality
causes of hypoventilation
drugs
damage to the chest wall
weakness/paralysis of resp muscles
high resistance to breathing
morbid obesity
how does obesity cause hypoventilation
affects both central resp drive and resp mechanics
if alveolar ventilation is halved, PCO2 is _____
doubled
alveolar gas equation CO2
PCO2= (VCO2/VA)*K
VCO2= CO2 production
VA= alveolar ventilation
K= constant
how is hypoxemia due to hypoventilation reversed?
increasing inspired o2 content
define diffusion limitation
decreased o2 diffusion through the blood-gas barrier
2 causes of diffusion limitation
decreased SA (ARDS)
decreased permeability (pulm. fibrosis)
2 causes of shunt
intracardiac right-to-left shunt
blood passes through a diseased or collapsed lung
what is the normal shunt fraction in healthy adults at RA
0-1%
what is the only cause of hypoxemia that is not responsive to an increase in inspired o2
shunt
why is there not an increase in PCO2 in shunting
chemoreceptors sense any elevation of arterial PCO2 and respond by increasing ventilation
this reduces the PCO2 of the unshunted blood until the arterial PCO2 is normal/ low
alveolar gas equation describes what
the concentration of gases in the alveolus and thus the effectiveness of gas exchange
can be used to calculate the tension-based indices of oxygenation such as A-a gradient or a/A ratio
What is the A-a gradient
magnitude of the gradient between the alveolus and the arterial blood
what is a normal A-a gradient at 21% FiO2
7mmHg in young
14mmHg in old
how is hypercapnia corrected in V/Q mismatch
increase ventilation
how is hypoxemia corrected in V/Q mismatch
increase FiO2
