MT2 Flashcards
1
Q
how much of body is skeletal muscle
A
30-40% body weight
2
Q
which type of muscle are striated muscle
A
skeletal and cardiac
3
Q
which type are unstriated
A
smooth
4
Q
voluntary muscle
A
skeletal muscle
5
Q
involuntary msucle
A
cardiac and smooth
6
Q
sarcomere
A
Functional unit of SHORTENING
interactions between myosin (thick) and actin filaments
7
Q
thick filament
A
1 thick surrounded by 6 thin filaments
MYOSIN molecules: 2 golf-club shaped subunits
tails aligned toward middle
globular heads protrude out at regular intervals
8
Q
thin filaments
A
joined at Z-line
helical actin molecules
each with a myosin binding site to allow for cross-bridge formation
9
Q
t tubules
A
an extension of membrane through the muscle cell
allows for propagation of action potential
deep channel into the cell from the surface
the sarcoplasmic reticulum surrounds t-tubules and myofibrils
10
Q
motor unit
A
motor NEURON and all the muscle FIBERS it innervates
vary in size- range of <10 to >1000 muscle fibers per unit; bigger can generate more force
each muscle fiber is innervated by just ONE AXON
each AXON BRANCHES to innervate all of the fibers in its UNIT
11
Q
how are motor units intercalated in bulk muscle
A
can elicit a range of strengths from the SAME muscle
lots of motor units inside; each with a different strength
12
Q
neural control with single action potential
A
has a reaction which causes muscle contraction but it will return to rest due to no new neural input (change in tension due to AP)
13
Q
what happens to the lateral sac after the DHP activation by the AP
A
depolarization releases Ca2+ from lateral sac
DHP activation directly gate open ryanodine receptors on the SR membrane
14
Q
what happens when the Ca2+ binds to the troponin
A
removes blocking action of tropomyosin
Ca2+ reflux from SR baths the myofibrils in Ca2+
15
Q
what allows the muscles to relax
A
Ca2+ transported back into SR via ATP-dependent pump
16
Q
what happens once Ca2+ is removed from cytoskeleton
A
troponin restores tropomyosin blocking action
17
Q
low cytosolic Ca2+; relaxed muscle
A
actin binding sites are covered!
cross bridge is energized
18
Q
high cytosolic Ca2+, activated muscle
A
Ca2+ uncovers binding sites
binding of activated cross bridge to actin generates force
conformational rearrangement occur so now the cross bridge can bind
19
Q
myosin is
A
motor protein
20
Q
actin is
A
highway
21
Q
H zone
A
1 thin end to the end of another
22
Q
start of power stroke
A
TROPOMYOSIN ropes covering ACTIN BINDING SITES
Ca2+ then RISES…
Cross bridge binds to actin
- ropes shifted and uncovered binding sites
23
Q
how is the flex allowed (cross bridge)
A
Loses the ADP+Pi
24
Q
how does the cross bridge detach from the binding sites
A
addition of ATP and its binding to myosin
25
how is cross bridge energized
hydrolysis of ATP
26
what happens if there is no ATP in the power stroke
cross bridge stays flexed and bound
27
muscle spindle is
proprioceptor; a sense organ that receives information from muscle, that senses STRETCH and the SPEED of the stretch
when you stretch and feel the message that you are at the ENDPOINT of your stretch, the spindle is sending a REFLEX ARC signal to your spinal column telling you to NOT STRETCH ANY FURTHER
PROTECTS from overstretching or stretching too fast and hurting yourself
28
golgi tendon organ is a proprioceptor...
sense organ that receives information from the tendon, that senses TENSION
when you lift weights, the golgi tendon organ is the sense organ that tells you how much tension the muscle is exerting
too much tension and the golgi organ will inhibit the muscle from creating any force, prevent injury
29
tension
force exerted on an object BY A CONTRACTING MUSCLE
30
load
force exerted on the muscle BY AN OBJECT
31
Isotonic contraction
muscle changes length while the load remains constant
concentric- SHORTENING
tension exceeds load
eccentric- LENGTHENING (extend)
load exceeds tension
32
isometric contraction
muscle develops tension but does NOT SHORTEN OR LENGTHEN
33
isotonic twitch
at heavier loads, latent period is longer
the shortening velocity (distance shortened per unit of time) is slower
distance shortened is less
34
what happens if you recruit more motor units
increases tension
more strength
35
tetanus
PERSISTENT firing of AP
Can’t relax bc the inhibitory pathways are inhibited ]
gets to a point where it can stay contracted so it fatigues out
the toxin from Clostridium tetani prevents inhibitory signals from reaching the motor neurons, causing them to fire action potentials continuously
36
length and tension
shortened muscle isnt capable of generating much more tension
there is an ideal resting muscle length in which the maximal tension is able to be produced
37
Sarcomeres WITHIN MUSCLE
if they are arranged SIDE BY SIDE- act very fast
or STACKED- very strong
38
Muscle hypertrophy
increase in muscle fiber size resulting from resistance training, where micro-tears in the fibers stimulate repair processes that add more protein filaments, leading to thicker and stronger muscles
39
why do kidneys receive the second most amount of blood??
Kidneys do FILTRATION
kidneys make sure ion balance of blood and liquid surrounding cells remains homeostatically regular
kidneys filter blood
kidney is able to clear large amount of blood volume from toxins
quickly adjust [sodium] and water volume of blood
40
kidneys are responsible for
maintaining stable volume, electrolyte composition, and osmolarity of the ECF
by controlling the [salt] of blood, automatically also controlling the [] of liquid around the organs
41
Nephron is...
the FUNCTIONAL UNIT of the kidney
42
juxtamedullary nephron
(20%) lie in the inner cortex layer
goes deep into renal medulla
long loop of henle
43
how many nephrons
approximately 1 million nephrons per kidney
44
Vascular component of the nephron
glomerus, afferent arterioles, efferent articles, and peritubular capillaries
45
tubular component of nephron
starts at Bowman's capsule
46
why are the capillaries so close to the tubular system
there is constant exchange of water and ions so the capillaries and tubular system are close together
capillaries are wrapped tightly around
47
afferent arteriole
carries blood to the glomerulus
48
glomerulus
tuft of capillaries that filter a protein-free plasma into the tubular component
49
peritubular capillaries
supply the renal tissue; involved in exchanges with the fluid in the tubular lumen
50
what happens to the large amount of plasma that enters the capillaries
gets filtered out
majority plasma is NOT FILTERED OUT; it continues on into the venous system
if not we would be peeing all day
51
juxtaglomerular apparatus
produces substances involved in the control of kidney function
region where the ascending loop of henle passes through the fork formed by the afferent and efferent arteriole, close to the glomerulus
52
what helps determine how much filtrate is made
AFFERENT and EFFERENT articles can constrict and expand
process is regulated
53
when do hormones start to play a role
hormones begin to play a significant role in reabsorption after the loop of Henle, primarily in the distal convoluted tubule and collecting ducts
54
What is the daily volume of plasma that is filtered
Approx. p180 liters of filtrate is formed each day
average plasma volume (blood-blood cells)= 2.75 liters
entire plasma volume in our body is filtered 65 times every day
approx. 178.5 of 180 liters of filtrate are reabsorbed
1.5 liters are secreted as urine
55
Glomerular Filtration
push plasma out of glomerular to capsule
glomerular membrane is considerably more permeable than capillaries elsewhere
glomerular capillary wall consists of a single layer of flattened endothelial cells
56
major force for glomerular filtration
glomerular capillary BLOOD PRESSURE
57
to be filtered, must pass through
pore between endothelial cells of the glomerular capillary (100x more permeable to H2O and solutes than regular capillaries)
acellular basement membrane (collagen for structural strength, negatively charged glycoproteins to repel proteins
filtration slits between the foot processes of the podocytes in the inner layer of the Bowman’s capsule
58
what if there is no pressure or filtrate?
suffer in pH, toxins stay in, kidney failure
As long as there is pressure in the capillaries, some plasma will get filtered out
59
glomerular capillary blood pressure
favors filtration; typically 55 mm Hg; CAN VARY
60
plasma-colloid osmotic pressure
caused by unequal distribution of protein between plasma and glomerular filtrate (no protein)
CONSTANT
opposes filtration
water wants to move down osmotic gradient INTO GLOM
61
Bowman's capsule hydrostatic pressure
fluid pressure by the filtrate in Bowman's capsule
Opposes filtration from GLOM to bowmans capsule
CONSTANT
62
Glomerular filtration rate (GFR); actual rate of filtrate depends on
net filtration pressure (major)
glomerular surface areas available for penetration (minor)
permeability of the glomerular membrane (minor)
controlled by glom capillary blood pressure
63
autoregulation
MYOGENIC, local response within arteriolar smooth muscle wall
tubuloglomerular feedback in response to salt concentration
vasoconstriction (decrease blood flow to GLOM) = reduce filtration
vasodilation (increases blood flow into GLOM)
REFERS TO THE COMBINED EFFECTS OF THE MYOGENIC RESPONSE AND TUBULOGLOMERULAR FEEDBACK
64
extrinsic sympathetic control
65
macula densa cells
detect and release paracrine factors that constrict the adjacent afferent arteriole in tubuloglomerular feedback
66
How would changes in blood pressure affect GFR ?
Increase blood pressure during exercise would increase GFR and lead to unnecessary loss of water and salts to urine
tubuloglomerular feedback prevents this
67
reabsorption allows
to reduce the ultimate filtrate amount to 0.5-1.5 liters
68
tubular reabsorption
selective movement of filtered substances from the TUBULAR LUMEN into the PERITUBULAR CAPILLARIES (e.g. H2O, Na+, Cl-)
69
tubular epithelium
entire length; tubule is ONE cell-layer thick
tubular epithelial cells have a luminal membrane and a basolateral membrane
70
adjacent tubular epithelial cells
form tight junctions (barrier; cant pass)
71
properties of capillary endothelium
through length; capillary is one very thin cell-layer thick
NO tight junction between endothelial cells (little barrier for water and solutes)
72
transepithelial transport requires substance cross 5 barriers
1. luminal membrane of the tubular cell
2. cytosol of tubular cell
3. basolateral membrane of the tubular cell
4. interstitial fluid
5. capillary wall
73
two types of tubular reabsorption
1. Passive reabsorption: movement down an osmotic or electrochemical gradient (e.g H2O)
H2O absorbed back bc it follows absorpotion of Na+
2. Active: requires energy (ATP), includes Na+, glucose, amino acids, other electrolytes
74
how much Na+ is reabsobred in proximal tubule
67%
2/3 reabsorbed before entering loop of henle
75
how much is reabsorbed in loop of henle
25%
76
how much is reabsorbed in distal and collecting tubules
8%
77
proximal tubule role in reabsorption
Na+ reabsorption plays a pivotal role in the reabsorption of glucose, amino acids, H2O, Cl-, and urea
78
loop of henle role in reabsorption
Na+ reabsorption plays a critical role in the kidney's ability to produce urine of varying concentrations and volumes
79
distal tubule role in reabsorption
Na+ reabsorption is subject to hormonal control, important in the regulation of ECF volume
80
What does BILIRUBIN do?
If your urine is dark yellow, you are seeing secreted bilirubin
it gives urine its color
get it by taking hemoglobin and breaking it down
81
is Na+ reabsorption active or passive
really only one step in the 5 step process that requires ATP and therefore is ACTIVE
Transported by Na/K ATPase across the basolateral membrane
every other step is DIFFUSION
82
why does Na+ diffuse into pertitubular capillary
bc interstitial concentration of Na+ is high
82
why does Na+ diffuse into TUBULAR CELL
bc intracellular concentration of Na+ is low (ATPase)
83
why does reabsorption take place all the time
there is a CONSTANT number of sodium channels in the luminal membrane and Na/K ATPase pumps
proximal tubule and loop of Henle, a constant percentage of filtered Na+ is reabsorbed regardless of the amount of Na+ in the body fluids
84
extent of reabsorption in relation to the na+ in the body reabsorption is related to the magnitude of the Na+ load in the body
reabsorption is inversely related to the magnitude of the Na+ load in the body
85
aldosterone (hormone)
stimulates Na+ reabsorption
determine faith of final 8% Na+ of filtrate at end of loop of henle
86
atrial natriuretic peptide
inhibits Na+ reabsorption
87
what happens with water as Na+ is reabsorbed
As Na⁺ is reabsorbed, it creates an osmotic gradient because the reabsorption of solute (Na⁺) decreases the concentration of solutes in the tubular fluid
Following the reabsorption of Na⁺, water passively follows sodium due to this osmotic gradient. This occurs primarily through aquaporins (water channels) in the tubular epithelial cells
88
Na+ reabsorption is followed by passive reabsorption
h2o down osmotic grad
Cl- down its electrochemical gradient
urea (waste product of protein breakdown); diffusion is not very effective
89
Aldosterone increases Na+ reabsorption in the distal and collecting tubules by
inserting additional Na+ leak channels in the luminal membrane
inserting additional Na/K ATPase in the basolateral membrane
BASICALLY increase the capacity of Na/K pumping & Na leaking in tubular cells
release controlled by RAAS system
89
aquaporins
proximal tubules express AQP1 (ALWAYS OPEN)
distal and collecting tubules express AQP2 (regulated by VASOPRESSIN)
90
aldosterone and RAAs; low BP
want to retain H2O: by retaining Na+ you also retain H2O;
preserve volume and NOT make more urine
91
angiotensinogen
synthesized in liver, always present in plasma
When blood pressure drops or when there is a decrease in blood volume (such as during dehydration), the kidneys release an enzyme called renin.
Renin converts angiotensinogen into angiotensin I, which is an inactive form
92
renin
released from kidneys (granular cells) into plasma
activates/converts angiotensinogen (precursor) into angiotensin I (active hormone)
(BP drops)
93
Angiotensin-converting enzyme (ACE)
enzyme present in the lungs; converts angiotensin I into angiotensin II
94
angiotensin II
has many effects (stimulates vasopressin, thirst, arteriolar vasoconstriction)
also stimulates the adrenal cortex to release aldosterone
travels to kidney ——- drives insertion of additional Na+ channels and ATPase ——-cause reabsorption
general constriction of arterioles in body helps to maintain BP (vasoconstriction)
95
when is RAAS shut down
Shut down RAAS system once goal is reached; restored to normal levels
96
treatments for hypertension
diuretics
counteracts vasopressin and prevents from reabsorbing all the water (you pee more)
ACE inhibitors
prevents kidneys from responding as effectively to RAAS = wont reabsorb as much H2O as kidneys otherwise do
pee out
counteract hypertension
97
natriuretic peptides
atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)
inhibit Na+ reabsorption
98
when are natriuretic peptides released
in response to high blood pressure/volume/NaCl load
99
what do ANP/BNP inhibit
Na+ reabsorption
RAAS activity
smooth muscle of afferent arterioles ----- increased GFR
inhibit sympathetic NS to reduce cardiac output and peripheral resistance
REDUCE BP!!!!!
100
when do we use BNP/ANP
response to High BP
101
reabsorption of glucose and amino acids
reabsorbed in PROXIMAL tubules by Na+ dependent specific symport carriers across tubular membrane into the cell (=secondary active transport)
102
secondary active transport
ex. SGLT- influx of Na⁺ into the cell, driven by its concentration gradient (established by the Na⁺/K⁺ pump), is coupled with the transport of glucose into the cell against its concentration gradient
103
glucose reabsorption
efficient and complete, number of sodium-glucose symporters is finite---- tubular maximum
excess glucose lost in urine
104
Hydrogen ion secretion is important in acid-base balance...
tubular secretion of H+ happens mostly in distal tubules (key way by which kidneys help control pH)
renal H+ is secreted in the proximal tubules
renal H+ can be either secreted or reabsorbed by special “intercalated cells’ in the distal and collection tubules depending on the acid balance in the plasma (final pH determined by if the distal tubules secrete more protons)
105
which way does K+ move
in opposite directions along tubules
106
where is most of the K+ reabsorbed
in the PROXIMAL tubules via leak channels in the basolateral membrane, tubular reabsorption
107
if there is K+ in the urine; what does that mean
tubular secretion at distal tubules
(have leak channels)
108
what does high plasma K+ stimulate
directly stimulates aldosterone from the adrenal cortex
109
vertical osmotic gradient
increasing osmolarity of the interstitial fluid in the renal medulla as you move from the outer region toward the inner region. This gradient is crucial for the kidney's ability to concentrate urine and regulate water balance.
The interaction between the descending and ascending limbs of the loop of Henle enhances the gradient
109
aldosterone and K+
aldosterone stimulates the insertion of K+ leak channels in the luminal membrane of the distal and collecting tubules
almost all the K+ in urine is the result of secretion
promote excretion
110
is 1200 mOsm/liter hyper or hypotonic
severely hypertonic; too little H2O relative to solute
111
descending limb
Permeability: Highly permeable to water
Function: Water is reabsorbed into the interstitium due to the osmotic gradient
Transport Mechanisms: Primarily passive transport; water exits through aquaporin channels.
112
ascending limb
permeability: Impermeable to water but permeable to sodium, potassium, and chloride
Function: Actively reabsorbs sodium, potassium, and chloride from the tubular fluid into the interstitium, which dilutes the tubular fluid as it ascends
113
why is osmotic gradient essential for vasopressin
osmotic gradient is essential for the reabsorption of water in the collecting ducts; the insertion of AQP2
114
net effect of countercurrent multiplication
ability to concentrate urine
115
When the body needs to conserve water...
vasopressin enhances the permeability of the collecting ducts to water, allowing more water to be reabsorbed into the bloodstream, resulting in concentrated urine
116
2 purposes of countercurrent multiplication
produces hypotonic urine that can be excreted if ECF within the body has too much H2O
est. vertical osmotic gradient (in interstitial fluid) that can be used by collecting ducts to concentrate urine if the ECF within the body doesnt have enough H2O
117
where does vasopressin have an impact
vasopressin controls H2O reabsorption in the COLLECTING TUBULES
118
water excess; no vasopressin
hypotonic urine; large volume of dilute urine
distal and collecting tubules are IMPERMEABLE to H2O
119
in water deficit; vasopressin
leads to insertion of AQP2 in luminal membrane
water leaves the tube and goes to medulla; get very concentrated
distal and collecting tubules are PERMEABLE to H2O
120
how does excess alcohol consumption interfere with kidney function
dehydrated... vasopressin release is impaired; more filtrate so urinate a lot
121
vasa recta
hairpin loop of the vasa recta by passive countercurrent exchange preserves the vertical osmotic gradient while supplying blood to medulla
122
relative amounts of sodium and water reabsorption in proximal tubule
equal amounts of each
123
relative amounts of sodium and water reabsorption in loop of henle
more Na+ than water
124
relative amounts of sodium and water reabsorption in distal and collecting tubules
more water than Na+
125
micturation (urination)
process of emptying the bladder
126
urine is transported...
from kidneys to the bladder via the ureters
127
what propels the urine to the bladder
peristaltic contractions of smooth muscle within the uretal wall
128
what prevents back flow of urine
as bladder fills pressure against the ureters prevents
129
bladder smooth muscle
rich innervated by parasympathetic fibers
stimulation of the parasympathetic fibers causes bladder contraction
130
what prevents the bladder from emptying continuously
internal and external sphincter
131
which sphincter is under voluntary control
external urethral sphincter
132
internal urethral sphincter
composed of SMOOTH muscle and NOT under voluntary control
when bladder is relaxed, CLOSES OUTLET of bladder
133
external urethral sphincter
composed of SKELETAL muscle and under VOLUNTARY control
motor neurons continuosly firing unless they are inhibited
134
micturation reflex (spinal cord reflex)
initiated when stretch receptors in bladder wall stimulate the parasympathetic supply to the bladder and inhibit the bladder motor neurons
prevented by tightening external sphincter,
135
Three principal components that make up the circulatory system
the heart (the pump)
• the blood vessels (the pipes)
• the blood (the fluid to be moved)
136
What is the circulatory system impacted by
The endocrine system, nervous system, and kidneys
137
Overall function of the circulatory system
Move blood around the body!
Supply oxygen and nutrients
Remove “wastes”
Temperature regulation
Distribute hormones
Clotting of open wounds
Immuno-vigilance
138
Components of blood
Cells, cell fragments, and plasma (55%)
Erythrocytes (45%); leukocytes and platelets; plasma (55%)
139
Plasma
at least 90% water and carries electrolytes and nutrients (glucose, amino acids, vitamins)
as well as wastes (urea, creatinine, bilirubin)
gases (O2 and CO2)
hormones
proteins produced by the liver such as albumin and fibrinogen.
140
Erythrocytes (red blood cells)
Function in oxygen and carbon dioxide transport. Biconcave disk in shape with a flexible membrane. They have a large surface area which favors diffusion.
NO NUCLEUS/ORGANELLES
Limited lifetime; no division of mature RBC
141
RBC enzymes
– Glycolytic enzymes
– Carbonic anhydrase
142
Hemoglobin
Binds oxygen and carbon dioxide
143
RBC life span
~ 120 days
144
Synthesis of RBC
Synthesized in red bone marrow by the process called erythropoiesis
145
What filters the RBC
Filtered by spleen and liver
146
What triggers differentiation of stem cells to erythrocytes
Erythropoietin (hormone from the kidneys)
147
Loops in cardiovascular system
2: systemic and pulmonary
148
Pulmonary loop
carries oxygen- poor blood to the lungs and back to the heart.
149
Systemic loop
carries blood from the heart to the rest of the body.
150
Is the circulatory system closed or open
Closed system!
LEAKS WOULD BE BAD
151
4 chambers
Left and right atria
Left and right ventricles
152
Where do the chambers on the right pump to
Pump deoxygenated blood through the pulmonary circulation to the lungs
153
Where do the chambers on the left pump oxygen-rich blood through
Systemic circulation to the body tissues
downnn
154
Power of left ventricle
Most powerful pumping chamber of heart
Pumps throughout the entire body
155
Right AV flows to
Right ventricle
156
Right ventricle flows to
Pulmonary artery
157
Left AV flows to
Left ventricle
158
Left ventricle flows to
Aorta
159
What do heart valves ensure
Ensure a one-way flow of blood
160
Right AV valve
Tricuspid
Experience lower pressures
Flows “up” (lungs)
161
Left AV valve
Bicuspid
Lower pressures
Up into aortic
162
Aortic or pulmonary valve
Semilunar
Experience highest pressures
Aortic (down to body)
Pulmonary (pulmones!! Up)
163
When will a valve open
When pressure is greater behind the valve
164
When will valve close
When pressure is greater IN FRONT of the valve
165
Endocardium
thin layer of endothelial tissue lining the interior of each chamber. It is continuous with the lining of the blood vessels entering and leaving the heart.
166
Myocardium
Middle layer of the heart wall, composed of cardiac muscle
167
Cardiac muscle cells connected end-to-end by
intercalated disks where two types of contacts are formed: desmosomes and gap-junctions
168
Desmosomes
Mechanically hold the cells together
169
Gap junctions
provide paths of low resistance to the flow of electrical current between muscle cells
enable the cardiac muscle to form a functional syncytium.
170
Epicardium
is a thin external membrane covering the heart and is filled with a small volume of pericardial fluid.
171
Cardiac cells
99% of cells are FORCE PRODUCING CELLS
• Called myocytes or contractile cells
• Contain striated muscle
• Muscle contraction follows a myosin/actin interaction.
1% of cells are the CONDUCTION SYSTEM
• Called pacemaker cells
• Do not have contractile components
172
Pacemaker cells set
Rhythm of heart
Communicate to contractile cells that through the syncytium they are all electrically coupled together
173
Autorhythmic
Heart muscle is capable of generating its own rhythmic electrical activity
174
Pacemaker cells grouped together
specialized regions called nodes that together control the rate and coordination of cardiac contractions
175
Do pacemakers initiate their own action potentials
Pacemaker cells intrinsically initiate their own action potentials at a regular frequency.
This process is referred to as pacemaker activity and is controlled by the generation of pacemaker potentials
176
Pacemaker potential (in 1% of heart cells that do; pacemaker cells)
Oscillation of the membrane potential which causes the cell to reach threshold and generate an action potential at a regular interval
It involves changes in K+, Na+ and Ca2+.
177
Do pacemaker potentials use different channels
There are 4 phases by 4 different channels
VG F-type Na Channel (F: funny)
• VG-T type Calcium Channel (T: transient)
• VG-L type Calcium Channel (aka DHP channel) (L: long-lasting)
• VG-Potassium Channels (several types)
178
What does hyperpolarization in pacemaker potentials lead to
Transient increase in Na+ permeability (Na funny channels) which causes membrane potential to depolarize
179
What does the membrane potential depolarization cause (pacemaker potential)
depolarization causes an increase in permeability to Ca++ (T-channel) that leads to further depolarization of the membrane potential and causes the cell to reach threshold.
180
What happens when a second increase in permeability to Ca2+ occurs
cell generates an action potential when a second increase in permeability to Ca++ occurs (L- channel).
Note: spike itself does not involve voltage-gated Na+ channels.
181
What happens as a result of depolarization from the action potential
causes an increase in K+ permeability
(K channels) and the membrane potential repolarizes.
182
What happens once the cell repolarizes
cell repolarizes, the K+ permeability again decreases and the process starts over again.
183
Sinoatrial (SA) node
Bundle of specialized cardiac pacemaker cells located in the wall of the right atrium near the opening of the superior vena cava.
exhibits an autorhythmicity of 70 action potentials per minute and leads the activity of the other pacemaker structures in the heart.
184
Atrioventricular (AV) node
Bundle of specialized, cardiac pacemaker cells located at the base of the right atrium
exhibits an autorhythmicity of 50 action potentials per minute.
Under normal conditions, this node follows the faster SA node at 70 A.P./min.
185
Bundle of His
A tract of specialized, cardiac pacemaker cells that originates at the AV node and divides and projects into the left and right ventricles.
186
Purkinje fibers
Small terminal fibers of specialized, cardiac pacemaker cells that extend from the Bundle of His and spread throughout the ventricular myocardium.
Very fast conduction velocity.
exhibits an autorhythmicity of 30 action potentials per minute.
Under normal conditions, they follow the faster AV node which is following the faster AV node at 70 A.P./min.
187
Interatrial pathway
pathway of specialized, cardiac cells that conducts pacemaker activity from the right atrium to the left atrium.
Fast conduction velocity.
188
Intermodal pathway
a pathway of specialized, cardiac cells that conducts pacemaker activity from the SA node to the AV node
189
AV Nodal Delay
Pacemaker activity is conducted relatively slowly through the AV node resulting in a delay of approximately 100 ms.
ensures that the ventricles contract after atrial contraction. Make sure ventricles are full and topped off
190
Resting potential of cardiac action potential
Very negative : -90mV
191
What causes the rising phase of the AP in cardiac AP
Fast Na+ influx; VG Na Channel
192
Does the cardiac AP have a plateau phase
exhibits a plateau phase.
The plateau is due to an increase in membrane permeability to Ca2+ (L channel) and a decrease in membrane permeability to K+ (VG K channel).
193
When does the falling phase of the cardiac AP occur
falling phase occurs when there is decrease in Ca2+ permeability and a rise in K+ permeability (VG K channel)
194
Heart muscle contraction vs voluntary muscle
Longer action potentials
Plateau period
Does not require nerve stimulation (usually stimulated by either an autorhythmic cell or an adjacent myocyte)
Calcium enters through L-type calcium channels, which ‘triggers’ more calcium to be released from the SR.
Contraction occurs DURING the action potential!
195
Refractory period of the heart
long twitch and the prolonged refractory period (that prevents tetanus) allow time for ventricles to fill with blood prior to pumping.
196
Excitation contraction coupling in cardiac muscle
197
Electrocardiogram
electrical currents generated by the coordinated action potentials of the heart muscle can reach the surface of the body and be detected as voltage differences between two points on the body surface.
The reading is a composite of the electrical activity, not a single action potential.
record resulting from measuring these voltage changes is referred to as the electrocardiogram or ECG. Disturbances in heart function can be detected as changes in the ECG.
198
Electrocardiogram
electrical currents generated by the coordinated action potentials of the heart muscle can reach the surface of the body and be detected as voltage differences between two points on the body surface.
The reading is a composite of the electrical activity, not a single action potential.
record resulting from measuring these voltage changes is referred to as the electrocardiogram or ECG. Disturbances in heart function can be detected as changes in the ECG.
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P wave
component of the ECG represents depolarization of the atria.
Begin of next heartbeat
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QRS complex
represents depolarization of the ventricles.
Sharp spike
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T wave
repolarization of the ventricles.
Bigger hump
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Atrial excitation
Begin w SA node
Complete w AV node
Top off ventricles
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Ventricular excitation
Begin w atrial relaxation
Complete with contraction of ventricles
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End of sequence of EKG
Ventricular relaxation
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Tachycardia
Fast heartbeat
Lots of QRS spikes
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Cardiac cycle
all the events involved with blood flow through the heart during one heart beat.
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Systole
Ventricular contraction phase
- pressures start to rise; force semilunar valves open (blood can leave)
Volume: ventricle topped off; squeeze blood out and volume decrease
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Diastole
Ventricular RELAXATION PHASE
pressure falls bellow and valve snaps shut (no more pressure holding valves open)
Refill ventricular
Atria contracts and tops off to restart cycle
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Cardiac output
= heart rate x stroke volume.
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Heart rate is regulated by
both branches of the autonomic nervous system
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stroke volume is regulated extrinsically
by the sympathetic nervous system and intrinsically by the volume of venous return (Frank-Starling mechanism)
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The mechanisms (neurotransmitter, receptors, downstream effects on ion channels and
slop of AP) by which sympathetic and parasympathetic input speed and slow heart rate,
respectively.
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The influence of the sympathetic branch on ventricle contractility and stroke volume.
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The Frank-Starling mechanism
the greater the volume of blood filling the heart (preload), the stronger the heart's contraction will be. This allows the heart to efficiently adjust its output to match the volume of blood returning to it, ensuring balanced circulation.
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aorta
largest artery in the body, responsible for carrying oxygen-rich blood from the heart to the rest of the body. It originates from the left ventricle and arches upward before descending
there ONE
2nd biggest internal radius
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arteries
blood vessels that carry oxygen-rich blood away from the heart to the body's tissues and organs. They have thick, elastic walls to withstand high pressure as blood is pumped from the heart, and they branch into smaller arterioles
100s
.2 cm internal radius
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arterioles
small blood vessels that branch from arteries and lead to capillaries. They play a crucial role in regulating blood flow and pressure by constricting or dilating in response to various signals, helping to control the distribution of blood to different tissues in the body.
1/2 million
very very small internal radius .003
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capillaries
smallest blood vessels in the body, connecting arterioles to venules. They facilitate the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues due to their thin walls and large surface area.
10 billion
EXTREMELY small internal radius .00035
largest cross sectional area
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inferior vena cava
large vein that carries deoxygenated blood from the lower half of the body back to the heart
1 of 2
biggest in internal radius
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superior vena cava
connects to right atrium
1 of 2
biggest internal radius
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Flow =
pressure gradient / resistance. While resistance is determined by several factors, the
main regulation is vessel radius. R is proportional to 1/r4 and therefore flow is proportional
to r4 . Thus, small changes in vessel radius can lead to large changes in local flow rate
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(smooth) muscular arteries constrict or dilate to change
relative blood flow to different
organs in a task-specific manner.
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Elastic arteries serve as pressure reservoirs to ensure
continuous blood flow
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sphygmomanometer
used to measure blood pressure
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intrinsic control of arteriole constriction/dilation
LOCAL
example
Myogenic Response: Arterioles can constrict or dilate in response to changes in internal blood pressure. An increase in pressure causes the smooth muscle in the vessel walls to stretch, leading to contraction, while a decrease in pressure results in relaxation.
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extrinsic control of arteriole constriction/dilation
mediated by the autonomic nervous system and hormones
Activation of the sympathetic nervous system leads to the release of norepinephrine, which typically causes vasoconstriction of arterioles, increasing blood pressure
Hormones such as epinephrine (adrenaline) can cause vasodilation in certain vascular beds while promoting vasoconstriction in others, depending on the type of adrenergic receptors present
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capillaries
extremely small blood vessels that serve to exchange materials between blood and tissues
SINGLE LAYER of endothelial cells
connections between endothelial cells form small water filled pores
LOOK SLIDES
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plasma carries
electrolytes, nutrients, wastes, gases and hormones for delivery to and from virtually all
cells in the body
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conduction through AV node
100ms delay ensures
that the ventricles contract only after the atria do
otherwise VERY FAST EVERYWHERE ELSE
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long twitch and prolonged refractory period of contractile cells
allow time for ventricles
to fill with blood prior to pumping
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read an ECG
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Note: these are bulk current source recordings, not intracellular
recordings, and therefore you cannot interpret upward and downward deflections as
depolarization and hyperpolarization
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cardiac cycle
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sounds/murmurs
pg 45
