Physiology Flashcards
Why is pulse pressure determined by SV?
Pulse pressure is the difference between the highest (systolic) and lowest (diastolic) arterial pressures. It reflects the volume ejected by the left ventricle (stroke volume). Pulse pressure increases when the capacitance of the arteries decreases, such as with aging.
What is aortic insufficiency?
In aortic insufficiency the loss of blood from the arterial system during each diastole is abnormally high, and, therefore, the aortic diastolic pressure is low, and the pulse pressure (= systolic pressure - diastolic pressure) is high. This increased diastolic runoff of pressure during each cycle is also seen when the heart rate, total systemic resistance, or arterial compliance is decreased.
Reduction in the permeability of the sodium ion will result in
hyperpolarization of the cell. The permeability of the cell membrane to Na and the “leakage” of Na into the cell contributes to the resting membrane potential, making it less negative than would be predicted on the basis of potassium concentration and permeability, alone. Reduction in potassium ion permeability, on the other hand would cause depolarization of the cell, as would influx of calcium ion to increased extracellular concentration of sodium or potassium ion.
The resting membrane potential is not exactly equal to the Nernst potential for potassium because:
the membrane has some permeability to species other than potassium. At the normal external potassium concentration the permeability of the membrane to other ions (Na, Cl, Ca) resulting in positive or negative charge transfer across the membrane also influences and contributes to the resting membrane potential. However, the dominant determinant of the resting potential is the K permeability.
Under a particular set of experimental conditions, a mammalian axon was found to be permeable to only one ion, K+. The equilibrium potential for K+ in this axon was -97mV. On the basis of these data, we expect to find a resting membrane potential of:
-97 mV. Because this membrane is permeable to only K+, its resting membrane potential will equal the K+ equilibrium potential (EK). EK is determined by the concentration gradient for K+ that exists between the extracellular and intracellular fluids, as described by the Nernst equation. The EK is the transmembrane potential difference necessary to perfectly balance, thermodynamically, a K+ concentration gradient of a given magnitude. At EK the flux or transport of K+ across the membrane, in both directions, is equivalent and therefore, net flux or transport of K+ is 0. We can estimate EK using the Nernst equation if the concentration gradient for K+, (K+OUT)/(K+IN), is known. As shown above, EK=61.5log (K+OUT)/(K+IN) = -97mV. If the concentration gradient for K+ were 0.1, it would mean that K+ was 10 times more concentrated inside the cell than outside the cell and the EK would equal -61.5 mV, because the log of 0.1 is -1. As shown above, EK equals -97 mV, therefore the concentration of K+ inside the cell must be more than 10 times the concentration outside the cell, and therefore, statements A and B must be incorrect. When the resting potential is -97 mV, there is a “microscopic” separation of charge across the immediate vicinity of the membrane, which does not measurably change the anion or cation concentration of the intracellular or extracellular solution. An increase in sodium conductance or channel-mediated Na transport across the membrane, will decrease the trans-membrane potential difference toward more positive values (depolarization) in a direction toward ENa, which is approximately +66 mV. This is due to the outward-to-inward direction of the Na gradient across the membrane resulting in net transfer of positive charge into the cell.
If the concentration gradient for K+ were 0.1, it would mean that
K+ was 10 times more concentrated inside the cell than outside the cell
Which autonomic receptor mediates secretion of epinephrine by the adrenal medulla?
Cholinergic nicotinic receptors. Preganglionic sympathetic fibers synapse on the chromaffin cells of the adrenal medulla at a nicotinic receptor. Epinephrine and, to a lesser extent, norepinephrine are released into the circulation.
Heart rate is increased by the stimulatory effect of norepinephrine acting on β1 adrenergic receptors in the:
sinoatrial (SA) node (positive chronotropic effect). There are also sympathetic β1 adrenergic receptors in the heart that regulate contractility (positive inotropic effect).
Which receptor mediates constriction of arteriolar smooth muscle?
alpa 1. The α1 receptors for norepinephrine are excitatory on vascular smooth muscle and cause vasoconstriction. There are also β2 receptors on the arterioles of skeletal muscle, but they produce vasodilation.
Which autonomic receptor is activated by low concentrations of epinephrine released from the adrenal medulla and causes vasodilation?
β2 receptors on vascular smooth muscle produce vasodilation. α receptors on vascular smooth muscle produce vasoconstriction. Because β2 receptors are more sensitive to epinephrine than are α receptors, low doses of epinephrine produce vasodilation, and high doses produce vasoconstriction.
A 45-year-old woman complains of pain in her fingertips and toes during cold exposure or emotional stress. This “Raynaud phenomenon” is caused by exaggerated sympathetic vasoconstriction in the extremities, producing ischemic pain. What receptors are involved in this activity? Would an ACh inhibitor be an appropriate treatment for her?
Vasoconstriction is mediated by norepinephrine release from sympathetic nerve terminals. Norepinephrine binds to α-adrenergic receptors on vascular smooth muscle cells, so the patient’s vasospasm may be relieved by an α-adrenergic inhibitor. Sympathetic ganglia are located close to the vertebral column, not peripherally, and postganglionic neurons are unmyelinated. Synaptic transmission within sympathetic ganglia is cholinergic, and, thus, an acetylcholinesterase inhibitor would augment sympathetic efferent activity thereby worsening the symptoms.
Which autonomic receptor is blocked by hexamethonium at the ganglia, but not at the neuromuscular junction?
Cholinergic nicotinic receptors (N2). Hexamethonium is a nicotinic blocker, but it acts only at ganglionic N2-type (not neuromuscular junction N1-type) nicotinic receptors. This pharmacologic distinction emphasizes that nicotinic receptors at these two locations, although similar, are not identical.
What is the dichrotic notch?
small change in pressure when the aortic valve closes (backfilling)
What is normal TPR value?
1.2 PRU (peripheral resistance unit)
What is systolic P?
The blood pressure when the heart is contracting. It is specifically the maximum arterial pressure during contraction of the left ventricle of the heart. The time at which ventricular contraction occurs is called systole.
What is diastolic P?
Referring to the time when the heart is in a period of relaxation and dilatation (expansion).
What is the mean aterial pressure?
avg P during entire cardiac cycle, = DP + 1/3(SP-DP)
What is pulse pressure?
PP = SP - DP = SV/compliance difference between SP and DP
What is the osmolarity of sweat?
100mOsm
What is a sweat gland innervated by?
ACh-secreting sympathetic nerve
What does ADH do in the brain in response to exercise?
Sweating results in volume depletion and an increase in ECF osmolarity, which drives water from ICF to the ECF. When this occurs in the brain, a decrease in cell volume induces the release of ADH (vasopressin) which stimulates thirst and triggers water retention by the kidneys.
What is important about the axon hillock?
Lots of voltage-sensitive sodium channels that contribute to the all or none response of the AP down the axon
What is the difference between large and small axon diameters?
Large axon diameters conduct impulses faster, internal electrical resistance reduced due to larger cross-sectional area
What is axoplasm?
Cytoplasm of the axon, axoplasmic transport renews the contents of synaptic terminals, contains arrays of microtubules and neurofilaments that provide structural stability to transport materials back and forth between cell body and presynaptic terminal
Give a chemical transmission with fast transmission (ie 1msec)
Ach (nicotinic), or amino acids
Give a chemical transmission with fastISH transmission?
Ach (muscarinic), catecholamines, GPCR’s
What is an ionotropic receptor?
Contain an ion channel as part of their structure, transmitter binding yields rapid reponse
What is a metabotropic receptor?
Commonly linked to G-proteins that transduce a slower biochemical signal
What does a muscarinic AChR do in cardiac muscle?
End result is decreased heart rate
What does a nicotinic AChR do in skeletal muscle?
End result is muscle contraction
What is an effect of GABA on postsynaptic cells?
Influx of Cl- to hyperpolarize cell
Give an example of an ionotropic receptor that produces an EPSP.
nicotinic cholinergic receptor for ACh, certain glutamate receptors ie AMPA, NMDA
Give an example of an ionotropic receptor that produces IPSP’s
GABA-A receptors, glycine receptors
What is decremental conduction?
Dendrites are thin and leaky to electric current. EPSP’s can reach the cell soma but a large amount of potential is lost by leakage though the membrane.
What does axon myelination do to capacitance?
Decreases it, C = sumA/d where d is the thickness
What is the difference between spacial and temporal summation?
Spatial summation is the summing of simultaneous postsynaptic potentials from multiple terminals. Temporal summation occurs when EPSP’s from the same cell arrive in rapid succession.
Match the receptor type to the agonist: N1
nicotine, ACh
Match the receptor type to the agonist: N2
nicotine, ACh
Match the receptor type to the agonist: a1
adrenergic, norepinephrine
Match the receptor type to the agonist: M1, M3, etc.
muscarine, ACh
Match the receptor type to the agonist: b2
adrenergic, epinephrine
Match the receptor type to the agonist: b1
adrenergic, epinephrine
Name an antagonist of: b1
propranolol
Name an antagonist of: a1
phentolamine
Name an antagonist of: N1
tubocurarine
Name an antagonist of: N2
hexamethonium
Name an antagonist of: the muscarinics
atropine
Name an antagonist of: b2
butoxamine
Name functions of b2-adrenergic receptor.
dilates bronchioles, relaxes smooth muscle, dilates skeletal muscle and surrounding vasculature, gluconeogenesis, glycogenolysis
Name the functions of b1-adrenergic receptor.
SA node and AV node conduction increase, increase in contractility, increase in saliva secretion, renin secretion and lipolysis
Name the functions of a1-adrenergic receptor
dilates pupil, contracts sphincter, contracts smooth muscle, constricts skin, splanchnic nerves, constricts skeletal muscle
Name one process where the SNS and the PNS are not acting to oppose one another
Penile erection (PNS) and ejaculation (SNS)
In both the parasympathetic and sympathetic divisions, the preganglionic neuron releases ____
ACh
The SNS directly innervates the _____ cells of the adrenal medulla which release primarily _____
chromaffin; epinephrine
What is special about the adrenal medulla?
Can secrete enough epi and norepi to normalize BP if sympathetic innervation to the heart is interrupted.
In the postsynaptic PNS neurons, the receptor is ____ and the NT is ____
muscarinic cholinergic (GPCR); ACh
In the postsynaptic SNS neurons, the receptor is ____ and the NT is ____
adrenergic (GPCR); norepinephrine
ACh onto _____ receptors for sweat release–an exception to the rule
muscarinic, even though sympathetic response
What are seven major effects of a massive SNS discharge?
- mydriasis/eyelid retraction (a1) 2. increased heart rate and force of contraction (b1) 3. bronchial dilation (b2) 4. vasoconstriction (a1) to GI system and kidneys (to shunt blood to skeletal muscles) 5. sweating (muscarinic) 6. increased cellular metabolism, epinephrine release from adrenal medulla (a and b) 7. decreased GI motility (a and b)
Name a positive chronotropic effect.
stimulation of SA node (SNS)
Name a positive dronotropic effect.
stimulation of AV node (SNS)
Name a positive inotropic effect
increased heart contractility (SNS)
Name a negative chronotropic effect.
inhibition of heart rate at SA node (PNS) via activation of muscarinic cholinergic receptors
Name a negative inotropic effect.
inhibition of atrial contractility (PNS) **mild effect** via strong vagal stimulation of heart
What is vasomotor tone?
Impulses of SNS (norepinephrine), maintain a partial state of contractility in the blood vessels, can be inhibited with total spinal anesthesia
What are three main points where MAP is being monitored?
- high P aterial baroreceptors 2. renal juxtaglomerular apparatus 3. low P baroreceptors (mostly volume receptors, only get involved with acute blood loss)
MAP = COxTPR=
SVxHRxTPR
_________ is the single most important mechanism providing short-term regulation of arterial pressure
Arterial baroreceptors
Carotid stretch receptors send signals via
increased firing of AP’s in response of MAP
Where are high P baroreceptors concentrated?
Carotid sinus and aortic arch
What is the primary function of the arterial baroreceptor system?
Reduce minute to minute variation in aterial pressure to about 1/3x that which would occur w/o the baroreceptor was not present
What is the baroreceptor reflex?
NFL by which increased MAP leads to ANS response to decrease heart rate, can make long-term adjustments, as with a raised set point in the case of hypertension
What is the valsalva maneuver?
Bearing down, way to test baroreceptor reflex
What is one way to bypass the capillary network?
Metarterioles, not present in all areas
What is convective transport?
substances are carried between organs and w/in the cardiovascular system, transport rate depends on concentration of substance and flow rate
What is happening when the transcapillary efflux rate is negative?
The tissue is producing the substance
What is Fick’s Law of Diffusion?
The flux (J) across the membrane is directly proportional to the area A of the membrane, and the concentration gradient across the membrane
Antergograde transport in the axoplasm involves:
microtubules
What happens in response to prolonged, continuous exposure of a ligand-gated channel to its ligand?
Refrection–it becomes desensitized
NMDA acts on what kind of receptors?
Excitatory aa receptors.
Hyperpolarization of the neuron is governed by what two ions?
Chloride and potassium.
How do GABA-A and glycine act in the neuron?
They act on a chloride channel which permits Cl- to enter the cell to hyperpolarize it
What is hematocrit?
rbc volume/total blood volume
Name three functions of microcirculation
- Thermoregulation of skin/extremeties 2. Filtration in renal glomeruli 3. Nutrient source and waste removal in (most) vascular beds
What spans a microcirculatory circuit?
From arteriole to venule (both have smooth muscle)
What are four important determinants of capillary diffusion?
- [] difference 2. available area for exchange 3. distance needed for diffusion 4. permeability of capillary walls to the substance being diffused
What is the total osmotic pressure of normal plasma?
5000 mm Hg
What are the two most important types of pressure in transcapillary fluid movement?
Osmotic (oncotic) and hydrostatic
Capillary flow, Jv, is proportional to:
filtration pressure
Define paracellular.
Between cells
Jv (capillary flow) from the capillaries to IF are:
positive
Flows from the IF into the capillary are:
negative
What channels are responsible for transcapillary water movement?
Aquaporin 1 channels
What is Pc? What does a high or low Pc value mean?
Pc is the capillary hydrostatic pressure, avg 25 mm Hg. High Pc favors filtration into IF.
Why is Pc in a normal capillary about 25 mm Hg, but only 5-15 mm Hg in the lungs?
Lower Pc prevents filtration and subsequent edema
In loose tissues such as lungs and subcutaneous, interstitial fluid pressure favors _____
filtration, and is slightly negative
In tight tissues, such as the heart or bone marrow, interstitial fluid pressure favors ______
absorption
Arteriolar constriction or venular dilation _______ capillary hydrostatic pressure
DECREASE
Arteriolar dilation or venular constriction ________ capillary hydrostatic pressure
INCREASE
Why is the net result filtration in arterioles, in pressure terms?
At the arteriolar end, hydrostatic pressure (favors filtration) exceeds the colloid osmotic pressure (favors absorption)
At the venular side of the capillary bed, more absorption occurs than filtration, why?
Because of the gradual increase in interstitial colloid osmotic pressure along the length of the capillary bed. The plasma contains protein, which gradually draws fluid out
When calculating the net capillary pressure, ADD the ___; and SUBTRACT the ______
ADD the Pc and πc, and subtract the IF values, πif and Pif
What is an average net daily filtration from the plasma to the interstitium?
2-4 L per day
What is ascites?
Fluid from hepatic and intestinal capillaries moves into the peritoneal cavity
Define SIADH
secretion of inappropriate ADH, by certain lung tumors or any cancer
Give two causes of pulmonary edema (not AMS related
left heart failure (CHF) and pulmonary hypertension (ie COPD)
What kind of edema is caused by right heart failure?
Edema of lower extremities and viscera
Log 0.01
-2
Log 0.1
-1
Why is there more K+ inside the cell than out?
The Na/K pump
Concentration gradient of K+ and the opposing electrochemical gradient create _____
potential across the membrane, an electrochemical equilibrium
Where can you find the highest vascular resistance?
Arterioles
What are the two most important and fastest acting responses to a sudden change in BP?
- CNS ischemic response 2. baroreceptors
After a change in BP, what i the long-term mechanism of maintenance?
Renin-angiotensin-aldosterone system, ***infinite gain***
Why does the CNS ischemic response kick in?
When blood flow to the vasomotor center of the lower brain is severely decreased
Why is the CNS ischemic response?
Becomes active below 60 mm Hg arterial pressure, emergecy pressure control system, heart will pump as much as possible to try to perfuse the brain, one of the most powerful activators of the sympathetic vasoconstrictor system
What kind of response is the CNS ischemic response?
Sympathetic, vasocontrictor
What is the Cushing reaction?
A special type of CNS ischemic response, happens with cerebral edema or hemmorhage that causes such severe swelling in the brain as to cut off circulation. The arterial pressure then rises to a level higher than the CSF pressure to force fluid to start moving again.
What are the characteristics of Cushing’s Triad?
- HR down 2. BP up 3. pupils blown
What is the function of renin?
Cleaves angiotensinogen –> angiotensin I
What is the function of ACE?
Converts angiotensin I –> angiontensin II in lungs
What are the three main functions of angiotensin II?
- acts directly on kidney to retain salt and water 2. causes adrenal gland to release aldosterone (which also increases salt and water reabsorption by kidneys) 3. promotes release of ADH by posterior pituitary gland
What are the tags for ANG II?
Short acting but strong vasoconstrictor, raises MAP
What is given for long term prophylaxis against hypokalemia?
acetozolamide
During a hemmorhage, high pressure baroreceptors do what?
Decrease firing rate –> HR up, cardiac contractility up, vasocontriction
During a hemmorhage, low pressure baroreceptors do what?
decrease firing rate –> SNS-mediated vasocontriction
During a hemmorhage,, central chemoreceptors do what?
respond to brain ischemia (acidosis) –> powerul SNS output is kidneys stop making urine
During a hemmorhage, what are the 4 kinds of receptors that produce an orchestrated response by the medulla?
- high P baroreceptors 2. low P (volume) baroreceptors 3. central chemoreceptors 4. peripheral chemoreceptors
During a hemmorhage, peripheral chemoreceptors do what?
respond to local hypoxia by increasing afferent firing –> SNS vasoconstrictor firing up
During a hemmorhage, what are the main orchestrated responses?
Increase ECF, produce and use ANG II
What is stressed volume?
Volume in arteries, creates a pressure. Unstressed volume in veins creates no pressure
What is the main (normal, non-emergency) function of the renin-angiotensin system?
To allow a person to eat either very small or very large quantities of salt, with no effect on [Na ECF] or volume or pressure
Name 7 things that stimulate ADH secretion
- decreased blood volume 2. pain 3. stress 4. decreased BP 5. nausea and vomiting 6. increased body fluid osmolality 7. ANG II
Name 5 things that inhibit ADH secretion
- decreased body fluid osmolality 2. increased blood volume 3. increased BP 4. ethanol 5. atrial natriuretic peptide, ANP
ANP decreases the release of
ADH
ADH is a vaso______
constrictor
tag for smooth muscle under the microscope
not striated
tag for discerning between skeletal muscle and cardiac muscle
no intercalated discs in skeletal muscle
What is the sarcolemma
pm of muscle cell
What is the innervation of the Auerbach’s plexus?
autonomic, PS ganglion
What is the smallest of the muscle cells, in terms of thickness?
Smooth muscle
What is the epimyseium?
Dense irregular connective tissue that surrounds muscle fiber groups
What is the perimysium?
Divides muscle into fasicles
Where are the nuclei in skeletal muscle?
Peripheral
Where are the nuclei in smooth muscle?
Central
What is the banding structure of skeletal muscle?
Z-I-A-H-M-H-A-I-Z
Why is skeletal muscle striated?
Myofibrils
Why are satellite cells around skeletal muscle important?
They play a role in regeneration
What kind of “twitch”are red fibers (type I)?
SLOW. numerous mitochondria, fatigue resistant, slow contractions over a long period of time
Why are red/type I fibers red?
Succinic dehydrogenase (a Kreb’s enzyme)
What “twitch” are white fibers? (type IIB)
FAST, derive energy from anaerobic glycolysis, lower myoglobin content
Are cardiac muscle cells multinucleate or mononucleate?
Usually have 1, maybe 2 nuclei
What are intercalated discs?
Interface between cardiac myocytes, occur at level of z lines, provide mechanical stability to gap junctions
What does atrial natriuretic factor do?
ANF is released in response to wall stretch in the heart, helps to control water and electrolyte balance and BP
What is the function of Purkinje fibers?
distribution of electrical stimulus to the myocardium
Give an example of ischemic heart disease/event
myocardial infarction
Give an example of inflammatory lesions of the heart
rheumatic fever
Give an example of valvular lesions of the heart
bacterial endocarditis
What is the only muscle that has branching?
cardiac
Where is ANF produced and released?
Heart muscle
What component of a cardiac muscle fiber is responsible for mechanical stability, transmission of electrical and chemical stimuli and contractile force?
Intercalated discs
What is the most common type of heart arrhythmia?
Atrial fibrillation
What is the sarcomere?
Z line to Z line, basic unit of a muscle fiber
What is the genetic defect that is responsible for malignant hyperthermia?
Defect in gene for ryanodine receptor
Give an example of heat being conducted away from the body
Ice pack on skin - a contact force
Give an example of convective heat loss
Windchill factor, air or water moving over the body
Give an example of evaporative heat loss
Just the heat you lose from being a person and metabolism
What is mass balance?
Homeostatic mechanisms match heat production to heat loss
What is a node of Ranvier?
The place where 1 Schwann cell meets another
What is special about the perineurium?
Several layers of specialized fibroblastic cells that for **right junctions** to provide a barrier to most macromolecules to protect nerve fibers
What is the preferred stain for seeing nodes of Ranvier?
Osmic acid
The sensory or dorsal root ganglion contain the cell bodies of what shape of neuron
pseudounipolar - no synapses in this ganglion!
Meissner’s corpuscles are receptors for _____ while Pacinian corpuscles are receptors for _____
light touch; pressure/vibration
What are intrafusal fibers?
Specialized muscle fibers that are proprioceptors for detection of length change in muscle fiber
The postsynaptic membrane of a skeletal muscle contains what receptors
ACh receptors
What is a good stain for seeing myelin?
Luxol fast blue (LFB) stain
