Final Slides Flashcards
(165 cards)
1
Q
reflex
A
A reflex is a patterned, involuntary response to a stimulus that is unlearned.
There are two major types of reflexes:
Monosynaptic: A response from a sensory neuron to a motor neuron through a single synapse.
Polysynaptic: One or more interneurons connect sensory and afferent signals.
2
Q
components of reflex arc
A
Receptor: Converts stimulus to an electrical signal, activating an action potential in the afferent neuron.
Afferent nerve fibers: Propagates the action potential to the integrator.
Integrator: Within the central nervous system (CNS), determines response to the afferent neuron.
Efferent nerve fibers: Propagates the action potential from the integrator.
Effector: Receives the signal and carries out the response.
3
Q
muscle spindle
A
Sensory receptors within the body of the muscle, parallel to the muscle fibers.
Function: Measures length and rate of stretch of the muscle.
Are modified (intrafusal) muscle fibers (typical muscle fibers are extrafusal).
Encircled by 1A afferents.
4
Q
Monosynaptic reflex
caused by the stretching of
the muscle spindle
A
○ Tap deflects tendon,
stretching muscle spindle
○ Excites 1A afferents (sensory
nerve)
○ 1A axons make a
monosynaptic connection to
α-motor neuron
○ Dorsal root of the spinal cord
integrates the signal
○ α-motor neuron (efferent)
synapses with muscle fibers
(effector), causing
contraction
5
Q
The Hoffman Reflex (H-Reflex)
A
The Hoffman Reflex (H-Reflex)
● Electrically induced monosynaptic reflex
● In lab, we will be directly stimulating the tibial nerve, & therefore bypassing the
muscle spindle (receptor)
● The tibial nerve contains both the 1A afferent and the α-motor neurons so we will
see 2 types of waves:
○ H-wave: caused by 1A afferent activation (normal myotatic reflex)
○ M-wave: caused by directly activating α-motor neurons
● Latency – time period between stimulation and response
6
Q
do 1A afferents have a larger diameter ? how is it helpful
A
Typically 1A afferents have a
lower threshold to direct
stimulation than α-motor
neurons due to their larger diameter
7
Q
antidromic
A
reverse direction
8
Q
what is seen with DIRECT stimulation
A
Wave amplitudes seen will
also depend on the
phenomenon of antidromic
(reverse-direction) AP’s
9
Q
which wave should appear first
A
M wave
10
Q
how will the waves change with increased voltage
A
Continuing to increase
the voltage should
increase the size of both
waves at first. Then
H-wave decreases
11
Q
what will make the H wave decrease
A
Holding at a moderate voltage and
increasing frequency should cause
H-wave to decrease
○ Low frequencies - α-motor neuron
recovers from the IPSP before the next
stimulus, a peak is seen
○ High frequencies - neuron can’t recover
from recurrent inhibiton, so the peak is decreased
12
Q
does M wave depend on afferent neruons
A
M-wave not dependent on input from
afferent neurons
13
Q
renshaw cell
A
an inhibitory interneuron
utilizing Glycine, in gray matter of spinal cord
14
Q
waht synapses iwth the renshaw circuit
A
axon collateral
15
Q
when is RC stimulated
A
RC stimulated when α-motor neuron activated at
high frequency
16
Q
what induces IPSPs
A
The RC synapses with its own motor neuron and
others nearby to induce IPSP’s (inhibitory
postsynaptic potential)
17
Q
recurrent inhibition
A
Recurrent inhibition: single interneuronal
synaptic self-inhibition
18
Q
Vestibular-Ocular Reflex (VOR)
A
Polysynaptic reflex: one or
more interneurons between
the afferent and efferent
branches.
○ Interneurons allow integrator
to collect multiple sources of
information before sending
out a final “decision” to the
efferent.
● VOR involved in sensing
angular acceleration and
deceleration, balance, and
centering of visual field.
19
Q
primary sensory structure of VOR
A
semicircular canals
20
Q
orientation of semicircular canals
A
3 orthogonally oriented canals in
each ear
○ X, Y, & Z axis
Are situated at a 30-degree
posterior angle to the head
○ X-axis becomes horizontal when head
is tilted forward
21
Q
semicircular canals contain
A
Contain specialized hair cells
(sensory receptors for angular
acceleration), and endolymph
(fluid medium that
detects/measures motion)
22
Q
hair cells
A
● Contain mechanoreceptors able to detect axial movement caused by
flow of endolymph
● One large Kinocilium (tallest) & many stereocilia (shorter) branch
off membrane
○ interlinked by the mechanoreceptors
● Cell synapses with vestibular nerve fibers (aff.)
● Hair bundles (cilia) are embedded in a gelatinous mass called the
cupola
23
Q
mechanotransduction: what opens as response to bending
A
xTip links on stereocilia are mechanoreceptors that open K+ channels in response to
bending
○ Bending stereocilia toward kinocilium causes increased K+ influx
○ Bending stereo- away from kino- causes decreased K+ influx
○ Endolymph has a very high K+ content compared to inside the cells so opening
mechanoreceptor channels causes K+ influx
24
Q
movement of base of hair cell
A
base of the hair cell is embedded in the semicircular canal
○ Moves with the direction of acceleration/deceleration
25
endolymph
extremely viscous so it does not move at first
○ Stereo- and kinocilia bend in the same direction of spin
26
what happens at constatnt speed for endolymph and hair cells
Once constant speed is achieved, endolymph catches up with hair cells and they
move together
○ Stereo- and kinoclia are no longer being bent
27
what happens during initial deceleration
During initial deceleration, endolymph continues at faster speed while hair cells
start to slow down
○ Stereo- and kinocilia bend opposite direction of spin
28
VOR reflex arc
Hair Cells (receptor) sense angular momentum (stimulus)
● AP’s are propagated along the vestibular nerve (afferent) to the brainstem
(integrator)
● Motor neurons (efferents) to the lateral and medial eye muscles (effectors) are
either activated or inhibited according to response program
● Nystagmus (response) is an alternating slow & fast pattern of eye movements in
response to changing acceleration of the head
○ Saccades: the fast component which occurs in the direction of acceleration or
perceived motion
○ Slow eye movement occurs in the opposite direction of acceleration or perceived
motion
29
nystagmus (response)
Nystagmus (response) is an alternating slow & fast pattern of eye movements in
response to changing acceleration of the head
○ Saccades: the fast component which occurs in the direction of acceleration or
perceived motion
○ Slow eye movement occurs in the opposite direction of acceleration or perceived
motion
30
case 3 look slides
31
delta
difference between end point and beginning point of selected range on y-axis
32
delta t
difference between end point and beginning point of selected range on
x-axis (delta T = difference in time, time is almost always going to be the unit on the
x-axis)
33
BPM
stands for beats per minute, measures cycles per minute
34
Freq
measures cycles per second
35
frog heart differences
Ventricle is trabeculated or grooved inside
* Primary pacemaker structure is the Sinus Venosus
* channels oxygenated and deoxygenated blood.
* the atrioventricular myocardium is a collection of cells that form a
funnel between the atria and ventricle that is similar to the AV Node
* No specialized ventricular conduction system (No Purkinje fibers)
* No equivalent to Bundle of His
* Less well developed SR – primary source of calcium is extracellular
* No coronary circulation – heart is oxygenated by direct diffusion
36
cardiac m
Cardiac muscle
* striated
* cells shorter than
skeletal muscle
* cells are connected by
intercalated discs
37
intercalated discs
Desmosomes –
mechanically bind the
cells together with
adherins proteins
* Gap junctions –
electrically couple cells
together
38
AP travel
AP from SA node travel from right
atrium to left, then to
atrioventricular (AV) node.
* AP travels from AV node to
His-Purkinje fiber system (if
present) and to ventricles
* Neural innervation (from ANS) can
modulate pacemaker activity, not
necessary for contraction.
39
overdrive suppression
When faster pacemaker cells
suppress the activity of slower
pacemaker cells
40
refractory periods
Ventricular muscle has a Refractory Period
* Effective Refractory Period - equivalent to the absolute refractory
period in nerves, and the ventricles cannot be activated
* Relative Refractory Period - an action potential can occur but
takes longer/greater stimulation
41
ventricular AP
42
SA node AP
43
cardiac m contraction
Ca2+ needed for contraction
* L-type Ca2+ channels on the
T-tubules
* Unlike skeletal muscle, channels
are NOT mechanically linked to
the RyR
* Influx of extracellular Ca+ is
absolutely necessary for Ca+ efflux
from the SR - Ca2+ induced Ca2+
release (CICR)
* Ca2+ acts as a ligand on the RyR
to cause further Ca2+ release
* Increase in intracellular Ca2+ will
induce contraction in the same
manner as with skeletal muscle
44
ventricular filling
AV valves open, semilunar valves closed
45
systole
contraction and emptying
46
diastole
relaxation and filling
47
pressure volume loop
Shows the relationship
between left
ventricular pressure
and volume during the
cardiac cycle
* Can be used to analyze
changes in
pressure-volume
relationships and
contractility in
response to a stimulus
48
frank starling law
heart will contract with more force
during systole if filled to a greater
extent during diastole.
* Can be demonstrated with P-V
Loop
* More filling = increased end
diastolic volume = increased SV
49
look at "electrocal mechanical act of heart slide"
50
extrasystole
a premature ventricular contraction (PVC)
* Often caused by depolarization in the ventricle rather than at the SA Node
An extrasystolic beat can be either larger or smaller than the beat immediately previous
* Smaller: the Frank-Starling Law (reduced filling time)
* Larger: increased Calcium buildup – similar to the effect of frequency in Lab 2, except
that cardiac muscle cannot achieve tetany due to the ERP
51
compensatory pause
A skipped beat sometimes caused by extrasystole to resume
the proper timing of the SA Node
* Beats following a compensatory pause are usually much larger in force than the
previous beat --- the Frank-Starling Law applies here!
52
look at extrasystole examples
53
vagal stim
vagus nerve contains
parasympathetic efferents to the
heart
* Neurotransmitter: ACh, Receptor: mAChR
* Vagal stimulation decreases HR (bradycardia)
* prolonged stimulation -> cardiac arres
54
is vagal innervation to the conduction nodes of the heart uniform
NOT UNIFORM
Many vagal fibers to SA node (or
equivalent), but few to other non-SA node
pacemakers
* Vagal stimulation slows/halts spontaneous
AP generation of the SA node, but has less
effect on the non-SA pacemakers
* Other pacemakers will “take over” in
generation of the heart rate at the next
fastest pace – vagal escape
55
epi and norepinephrine
Epinephrine and Norepinephrine
are ligands of the β-Adrenergic
receptor in the heart and the
α-Adrenergic receptor in the
vasculature.
* Postganglionic Sympathetic
fibers primarily release NE;
receptors will also respond to
Epi released from the adrenal
medulla
* Epi will cause an increase in HR,
and a decrease in cardiac AP
duration – increase in strength of
contractions
* Increases stroke volume
independent of ventricular
filling
56
internal respiration
process by which O2 is consumed to produce ATP and CO2
57
external respiration
process by which O2 and CO2 are exchanged from the environment into the body
1. ventilation of air from the environment into the lungs
58
primary function of the respiratory system
is to exchange gases from the environment to the
tissues (providing Oxygen for metabolism)
59
during ventilation, how does air travel
into airways down a
pressure gradient through several tissues
* Entry through nose/mouth
* Passage through nasopharynx and
oropharynx, glottis, larynx
* Entry into tracheobronchial tree
* Exchange at alveoli
60
secondary functions of ventilation
water and heat
balance, acid base balance, respiratory pump,
immunity, vocalization, production of some
enzymes & hormones, & olfaction (smell)
61
blood in pulmonary circulation
flows such
that oxygen will move into the blood and carbon
dioxide will move out
62
carbon dioxide diffuses from the cell into
capillary blood and can react in 3 major ways:
~8% will react slowly to form bicarbonate
2. ~65% will enter red blood cells and react
rapidly with water and carbonic anhydrase
(CA) to form bicarbonate
3. ~27% will enter the RBC and react with
terminal amine groups of blood proteins,
primarily hemoglobin – forming
carbaminohemoglobin.
Gas exchange
63
alveoli
clusters of thin walled,
inflatable sacs at the terminal
ends of branching generations in
lungs.
64
type I alveolar cells
Flattened single layer of cells forming
the wall of the alveoli & performing
gas exchange with the capillary.
* Total surface area of Type I to
Capillary contact is about 75 square
meters!
65
type II alveolar cells
About 5% of total alveolar cells
* Secrete pulmonary surfactant –
facilitates lung expansion and
decreases resistance.
66
inspiration
Air is taken into the
lungs using diaphragm and
external intercostals (active)
Diaphragm
* Innervated by phrenic nerve
* Contracts and pulls downward,
expanding the intrapulmonary space.
* External intercostal muscles
* Innervated by the intercostal nerves
* Contract between the ribs contract and
pull upward to enlarge the rib cage.
Overall, there is an increase in the
size of the thoracic cavity and a
decrease in the intrapulmonary
pressure. As a result, air rushes in
and fills the lungs.
67
expiration
Air flows out,
passive (no muscle use in
quiet expiration).
* Inspiratory muscles relax,
diaphragm rises
* Similar to a deflating balloon,
the lung pressure rises to
force air out of the lungs and
airways.
* Forced expiration 🡪
abdominal wall muscles &
internal intercostal muscles
can contract to force out
additional air
* Exercising, coughing, sneezing,
etc.
68
tidal volume TV
volume of air entering and leaving the lungs with each normal breath
69
inspiratory reserve volume
amount of air that can be forcefully inspired after normal TV inspiration
70
expiratory reserve volume
amount of air that can be forcefully expired after normal TV inspiration
71
residual volume
residual volume of air in the lungs after a forced expiration
72
vital capacity
amount of air that can be inspired and then expired with maximal effort
73
forced vital capacity
amount of air that can be expelled when a forced inspiration is taken, then forcefully expired as much as possible
74
alveolar ventilation
Amount of fresh air that reaches alveoli/minute.
● Due to anatomical dead spaces, not all air reaches alveoli – part of each breath remains in
the conducting pathways (trachea/bronchi).
● There is some capacity for altering depth & rate of breathing to increase or decrease gas
exchange as needed.
75
Atmospheric pressure (Patm)
Pressure of gasses in the
surrounding air. Respiration pressure values are normally
discussed in relation to Patm
76
Intra-alveolar pressure (Palv):
Pressure of alveoli, which
changes with the phases of breathing. Alveoli are connected via
tubing to the atmosphere, so Palv always equalizes with Patm
77
what helps create inward pull
Elastic properties of the lungs
* Pulls lungs inward away from thoracic
wall
* Surface tension in alveoli also creates
an inward pull.
2. Inward tension is opposed by the
tendency of chest wall to recoil and
expand outward
* Surface tension in pleural cavity pulls
lungs out
Ultimately, outward pull is slightly greater
than the inward pull which creates the – 4
mmHg intrapleural pressure
78
what spontaneously initiates breathing
Pons and Medullary
respiratory centers
79
Dorsal Respiratory Group (DRG)
contain mostly inspiratory neurons (i.e.
phrenic nerve)
80
Ventral Respiratory Group (VRG)
contain both inspiratory and expiratory
neurons, but more important in pacing
(exercise)
81
pre botzinger complex
cont pacemakers
82
pneumotaxic center
involved in
stopping inspiration
83
apneustic center
involved in initiating inspiration
84
hyperventilation
is an increase in ventilation
achieved by increasing respiratory rate and/or
tidal volume, not related to metabolic drive.
* Rate of ventilation is higher than what is needed
to remove CO2 from blood
* Leads to a decrease in PCO2 (hypocapnia)
* Decreased PCO2 causes decreased inspiratory
drive
85
prolonged hyperventilation
will lead to
respiratory alkalosis (increase in pH)
* Leads to vasoconstriction in brain arterioles
* Decreases blood flow in the brain -> dizziness
86
hypoventilation
is a decrease in ventilation,
leading to an increase in arterial PCO2
(hypercapnia)
* The increase in PCO2 will cause a decrease in pH
(respiratory acidosis)
* This activates chemoreceptors to increase
respiratory rate
87
peripheral chemoreceptors
*Found in the carotid
bodies and aortic
arch
*Able to sense
decreases in arterial
PO2 (hypoxia) and to
a lesser extent
increases in PCO2,
decreases in pH
88
what will come from the activation of perioheral chemoreceptors
Activation of
receptors will cause
an increase in
ventilation rate
89
central chemoreceptors
located in the medullary respiratory center
sense increases in PCO2 and decreases in pH by sensing [H+] in cerebrospinal fluid
SLOW reaction but when the chemorecpetors are activated it will cause an increase in ventillation rate
90
stretch receptors
are located in the smooth muscle of large and
small airways, also in lung parenchyma (connective tissue around
lungs)
91
afferent fibers and vagus nerve relation
Afferent fibers travel through the vagus nerve and project into
the brainstem
92
hering breuer reflex
When there is an increase in stretch there will be an inhibition of
inspiratory neurons. The opposite will happen if there is a decrease in stretch. (Hering-Breuer Reflex
reflex contributes to pacemaking and initiation of
inspiration & expiration. (NOT actually a significant contributor
to prevention of overinflation – the ribs do that!)
93
high levels of inflation
= increased
stretch = decreased respiratory
drive
94
low levels of inflation
= decreased
stretch = increased respiratory
drive
95
factors that affect ventillation
Arterial PCO2 and PO2
* Blood PH
* Temperature
* Exercise or anticipation of exercise
* Voluntary control
96
receptors involved in control
Central chemoreceptors (medulla
oblongata)
* Peripheral chemoreceptors (aortic
arch & carotid body)
* Muscle spindle / stretch receptors
(lung parenchyma)
97
cardiac output
Volume of blood pumped by each of the
ventricles per minute
○ CO = HR x SV = heart rate (bpm) x stroke vol (vol/beat)
○ What are the units for CO?
■ Vol/minute -> L/min
98
capacitance
degree of active constriction of
vessels
constant in arteries
holding capacity
Venous system acts as a storage reservoir
99
increase in volume in arteries
arteries when blood is
ejected from the ventricles during systole
○ ~1/3 of the blood in arteries flows out during
systole
○ The increase in volume causes the arteries to
distend slightly, increase Pressure
○ During diastole, the arteries passively recoil
due to their elastic properties, pushing more
blood out
100
MAP
Mean Arterial Pressure (MAP): average effective pressure that drives
blood through the systemic organs
○ MAP = CO x TPR
○ TPR = Total Peripheral Resistance; overall resistance to flow through the entire
systemic circulation
101
MAP approx
MAP = 1/3 SBP + 2/3 DBP
○ This is a weighted average because the heart spends more time in diastole than
systole
102
pulse pressure
PP = SBP – DBP
● Typical/normal human blood pressure:
○ 120/80 mmHg
103
korotkoff sounds
“tapping” sounds that a partially occluded artery
makes due to turbulent blood flow
● When pressure is low enough to allow some blood to pass, intermittent
turbulent flow is heard as a tapping sound.
○ Systolic BP – Pressure where the first Korotkoff sounds are heard
(Peak pressure generated by artery)
○ Diastolic BP – Pressure where Korotkoff sounds are no longer heard
104
blood flow is achievd thru
differences in pressure
105
flow causes
friction between blood and vessel walls, causing vessels to resist
fluid movement
106
vascular resistance
measure of how hard it is for blood to flow through a
vessel
Generally pressure is regulated (constant) so changes in resistance are used to
alter flow rate
107
poiseulle's equation
Describes pressure changes in regards
to fluid viscosity
○ Flow rate is primarily regulated by
changes in the radius of the vessel
108
pressure in blood vessel is determined by
Volume of blood in the vessel
○ How easily the vessel can be stretched (Compliance
109
Increasing inflow or decreasing outflow will cause vessel volume to
increase
In arteries: Increase in SV, CO, HR, or increase in arterial resistance =
increase in volume
○ In veins: Decrease in right heart pumping, Change in body position
from reclining to upright = increase volume
110
decreasing inflow or increasing outflow will cause
venous volume
to decrease
○ Increase in arterial resistance, increase in SV or HR due to increased
cardiac contractility
111
hydrostatic pressure
gravity produces difference between 2
points of different height
112
move rapidly from supine to standing
gravity
causes increased
hydrostatic pressure in
lower body
○ Decrease in venous return,
HR, CO, arterial blood
pressure
○ This can cause inadequate
cerebral blood flow resulting
in dizziness
113
baroreceptors
Maintains BP at a normal level
● Baroreceptors detect stretch,
located in the carotid sinus and
aortic arch
● Baroreceptors send afferents to the
brain (CV center of Medulla)
○ Changes in firing rate signal changes
in BP:
■ Increase P = increase firing
● Response is mediated through
sympathetic and parasympathetic
activity
114
Sympathetic nerves release
norepinephrine which bind to
α1
-adrenergic receptors on smooth
muscle cells in the vessel walls, causing
vasoconstriction
115
Sympathetic efferents to the heart
release
norepinephrine which bind to
β-adrenergic receptors and cause
increases in HR and contractility (SV, CO)
116
parasympathetic nerves innervate
only certain vascular beds and
locations, and release acetylcholine to bind to the muscarinic
AChR
○ Causes vasodilation
Parasympathetic efferents to the heart release acetylcholine and
bind to muscarinic AChR, causing a decrease in HR and contractility
(SV, CO)
117
increase in BP:
decrease
sympathetic and increase parasympathetic
118
decrease in BP
Decrease firing rate of baroreceptors, decrease
parasympathetic and increase sympathetic
119
reactive hyperemia
Reactive Hyperemia: Reaction to a
decrease in blood flow to a tissue with no
change in the tissue’s metabolism
○ Result: Transient higher than normal blood
flow after removal of the occlusion
○ Example: when you sit on your leg and
your foot “falls asleep”, then feels warm
when it “wakes up
120
why do veins have low amounts of pressure
because of compliance
121
active hyperemia
Increased
blood flow caused by an increase
in metabolic activity, such as
exercise
122
response to exercise
Increase in sympathetic activity
at the onset of exercise
increases HR and CO – leading
to an increase in MAP
123
diving reflex
Allows prolonged submersion by limiting rate of oxygen use and
directing blood flow to essential organs
● Mechanism: bradycardia (reduced heart rate), vasoconstriction at
non-essential organs
○ Increased Vagal activity → bradycardia
○ Increased general SNS activity → peripheral vasoconstriction
124
125
Functions of the kidney
Regulation of water concentration and fluid volume
► Regulation of inorganic ion concentrations
► Regulation of acid-base balance
► Some gluconeogenesis & synthesis of hormones
► Excretion of metabolic waste products & xenobiotics
126
Four essential renal processes
Filtration – substances move from glomerular capillary to lumen
Reabsorption – substances reclaimed from lumen to blood
Secretion – substances move from peritubular capillary to lumen
Excretion – substances are removed in the urine
127
Kidney anatomy
2 Kidneys located at
either side of vertebral
column at
posterior/dorsal wall
► (outside main
visceral cavity =
retroperitoneal)
► 2 Ureters connecting
each kidney to the
urinary bladder
► 1 Urethra connecting
the bladder to the
exterior for excretion
128
Tissue of kidney
Cortex and medulla
129
Cálices
Minor calices collect each
pyramid; Major calices collect
groups of minor calices; Ureter
collects Major calices
130
Nephron
Functional unit of the kidney
= nephron (~1 million total)
► Extends through both cortex
and medulla
► Depth into medulla tubules
extend determines how
much it can concentrate
urine
► 15% Juxtamedullary
nephrons contribute to
medullary osmotic gradient
► Remainder Cortical
nephrons
131
Renal corpuscle
The Renal Corpuscle includes:
► Glomerulus: capillary filtration
unit
► Bowman’s capsule: surrounds
the glomerulus to capture
filtrate in Bowman’s space
► Connects to proximal
convoluted tubule to pass on
filtrate
► Creates a filtrate similar to
plasma, free of blood cells and
proteins
► Input: Afferent arteriole
► Outflow: efferent arteriole
132
Glomerular filtration
Endothelial cells are
fenestrated (holes ~70nm
wide)
► Basement Membrane
composed of gel-like
acellular network of
collagen and
glycoproteins surrounds
endothelial cells
► Podocytes interdigitate
around the basement
membrane, leaving gaps for flow-thru (~4-14nm)
► Large negatively charged
proteins are repelled, small
solutes pass through
133
Filtration driven by
Pressure differences
134
Tubular system
Tubules are lined with
epithelial cells that have
differing channels & pumps
all along the length
► Proximal Convoluted Tubule
► Loop of Henle
► Distal Convoluted Tubule
► Collecting Ducts
► Peritubular Capillaries are a
second capillary bed that
comes off the efferent
arteriole & surrounds the
tubule system
135
Tubular secretion
Some substances are NOT filtered at
the glomerulus, but instead secreted
into the tubule by the peritubular
capillary
► Important for acid/base balance
► K+, H+, NH4+, urea, some creatinine,
some hormones, & some drugs
► Usually occurs by active transport
across epithelial cell membranes
136
Reabsorption
Tubular epithelial cells transport certain
substances back across into the
peritubular capillary.
► Glomerulus filters ~180L/day but most
essential substances are reabsorbed
► 99% of water
► 100% of sugar
► 99.5% of NaCl
► At normal pH, most of bicarbonate
► Reabsorption can be passive (using flux
down gradients) or active (using pumps
or exchangers)
137
Potassium balance
Mostly reabsorbed – 60% at proximal
tubule, 20% at Loop of Henle
► Depending on balance, secretion
occurs in cortical and medullary
collecting ducts
► Requires H-K-ATPase channel in Type
A Intercalated cells
► Requires H+ secretion to reabsorb K+
► Works fine normally but plasma
acid/base balance can affect K+ levels
► Aldosterone, hypernatremia, volume
depletion, ACTH -> stimulate K+
secretion.
► Reduced secretion – Dopamine, ANP
138
Sodium reabsorption
Proximal convoluted tubule
reabsorbs ~65% (Uncontrolled
active transport)
► Loop of Henle reabsorbs ~25%
(uncontrolled passive transport)
► Distal tubules and collecting
ducts reabsorb remainder
► Aldosterone & AVP increase
reabsorption
► ANP increases excretion by
inhibiting reabsorption
► Many drugs act on Na
reabsorption - diuretics
139
Water reabsorption
Proximal tubule ~65%
(uncontrolled)
► Water follows sodium reabsorption
to keep osmotic balance
► Loop of Henle ~10% (uncontrolled)
► Distal tubules and collecting ducts
~5-25% depending on fluid need
► Controlled largely by AVP
► Chloride also follows Na+ and
water
140
Acid/base balance
Body naturally produces acid from metabolism, respiration, digestion
► Under normal conditions:
► Bicarbonate is reabsorbed in the proximal tubule (80%) and loop of henle (10-20%)
► Acid is secreted using buffers like H2PO4- and NH4+
141
Glom filtration rate
GFR = Kf x Pnet
► Kf = filtration coefficient
► Pnet = net filtration pressure
► Typical adult GFR = 125 mL/min
► Due to the small size of the renal
corpuscle, we have no way to
directly measure GFR
► Instead we can estimate it using
substances that are freely filtered
but not secreted or reabsorbed
► Assumes relationship between
substance excretion and GFR
142
Clearance
Clearance volume of
plasma that is completely
“cleaned” of a substance
(vol/time)
► No natural substance in
the body where Cx=GFR
► Inulin – plant compound
► Creatinine – metabolite
of creatine phosphate
that is freely filtered, not
reabsorbed, & only
secreted a little
► Cx = (Ux x Vurine) / Px
► Ux : [x] in urine (mmol/mL urine)
► Vurine : urine flow rate (mL/min)
► Px : [x] in plasma(mmol/mL plasma)
► If Cx is equal to GFR then
substance is only filtered
► If Cx is greater than GFR then
net secretion of substance
► If Cx is is less than GFR then net
absorption of substance
143
Creatine
Because creatinine is also secreted in small amounts by the proximal
tubules, it overestimates GFR by 10-20%
► Produced at a relatively constant rate, so easily monitored
► C
cr = (Ucr
x Vurine)/ Pcr
≈ GFR
► GFR is proportional to creatinine clearance and to Urine creatinine
► GFR is inversely proportional to Plasma creatinine
► Pcr is often used clinically as a rough measure to monitor kidney function
144
Specific gravity
Specific gravity is a ratio of the density of a material to the density of
water
► Specific gravity = pmaterial/ pwater
► This will be used as an index of the total solute within the urine
(osmolarity)
145
Arginine Vasopressin (Antidiuretic Hormone)
Arginine Vasopressin (Antidiuretic Hormone)
► AVP (aka Antidiuretic hormone) – hormone made in the
hypothalamus and stored in the posterior pituitary
► AVP release is controlled by blood pressure, plasma osmolality and
ANG II
► AVP acts to increase water permeability of distal tubules and
collecting ducts -> increase water reabsorption
► Note: Ethanol (alcohol) inhibits the release of ADH, so you will excrete
dilute urine -> dehydration -> contribute to symptoms of hangover
146
Atrial natriuretic peptide
Synthesized and secreted by cells in the cardiac atria
► Released when pressure (or stretch) in the atrium gets too high, ie.
high BP.
► Causes relaxation of afferent arteriole into the renal corpuscle
► Inhibits release of renin
► Which will cause an increase or decease in Na+ reabsorption?
Water reabsorption?
147
Mechanical work
application of a force resulting in the movement of an object
148
Fatigue
a decrease in the muscle’s ability to generate force
149
Tonus
a constant state of slight tension of the skeletal muscle
150
Grading
changing strength of a muscle contraction based on input
151
Electromyogrpahy
Recording of bio electrical activities EMG
152
Skeletal m
Contract to perform mechanical work (picking up a weight).
○ Must exert enough force to overcome the weight of the object (if less, object will not move).
●Review the basics of skeletal muscle
○ Striated, made up of muscle fibers that contain myofibrils.
■ Type I- slow twitch (postural maintenance & endurance)
■ Type II- fast twitch (anaerobic respiration, easily fatigued)
○ Sarcomere is the contractile unit (actin & myosin)
○ Excitation contraction coupling
■ Electrical stimulus triggers Ca2+ release, which results in sarcomere shortening
153
Motor units
Stimulation of contraction
occurs when brain or spinal
cord activates motor units.
● Motor unit – a motor
neuron and all the muscle
fibers it innervates.
When contraction is needed,
a train of APs (enough to
induce tetany)are sent to the
muscle fibers of the motor
unit.
Tetany = fusion of individual
muscle twitches.
154
Myosin and actin
thick and
thin respectively) are arranged
in repeating patterns called
sarcomeres
155
Myofibrils
chains of
sarcomeres
○ Hyperplasia: growth of
muscle due to increase
of cell number
○ Hypertrophy: growth of
muscle due to increase
of cell size
● Muscle fibers are groups of
myofibrils
156
Motor unit recruitment
The number of motor units activated by the brain is proportional to the
amount of work to be done
○ More motor units are simultaneously activated when you lift 50kg than when you lift 10kg
○ Small motor units: tens to a hundred of motor units
○ Large motor units: hundreds+ motor units
Brain utilizes sensory information from stretch receptors in the
muscle/tendons/joints.
157
Motor unit recycling
Once you lift an object, the brain recruits about the same # of motor units, but cycles through them.
○ Allows motor units to relax and replenish fuel sources
158
Excitation contraction coupling
1. AP from motor neuron to NMJ,
release of ACh
2. ACh binds to receptors on cell
membrane → depolarization
3. AP on cell membrane travels
through T-tubules, activates
DHPR’s (VG-calcium channels),
signal to RyR’s (calcium channels
on SR)
4. Ca2+ release from SR
5. Calcium binds to troponin, moves
tropomyosin away from
myosin-sites on actin
6. Myosin attaches to actin to form
cross-bridges → power strok
159
Muscle fatigue
●Fatigue – decrease in the muscle’s ability to generate force
○ Caused by depletion of fuel supply – when the muscle uses its
energy sources faster than can be generated by metabolism.
●Contraction converts chemical energy 🡪
thermal/mechanical
○ Produces waste products (metabolites)
○ Normally carried away in circulation, and blood brings back
nutrients to the muscle
○ If metabolites are not removed, increases onset to muscle fatigue
160
Mental fatigue
Mental Fatigue - if an individual loses motivation/focus
○ Crowd cheering on runners in a marathon
161
Metab of ATP
Creatine phosphate
a) ADP → ATP
2) Anaerobic Pathway
a) Creates 2-4 ATP
3) Aerobic Pathway
a) Creates 28-32 ATP
162
Reading EMG
Motor unit recruitment measurement:
○ Motor unit activation causes electrical impulses under the skin – we will detect
these with surface electrodes – and record via EMG.
○ EMG recording is caused by:
■ Propagation of motor nerve impulses to the neuromuscular junction (NMJ) of the
motor unit.
■ Propagation of muscle impulses that eventually result in excitation-contraction
coupling.
○ The 2 above both involve depolarization & repolarization, so we will see negative and
positive “spikes” in the data.
■ We “integrate” the data – which takes an average of the noisy spikes to create
and integrated EMG to clearly show the pattern of muscle activit
163
Renal Lab: Hypotonic Subject (water)
, Dramatic increase in volume
○ Nephrons reabsorb about 65% and 10% of water (consumed in regular amounts) in the proximal
convoluted tubule and Loop of Henle (respectively)
■ Excess of water is passed out into the bladder and eventually excreted
● Maybe slight increase in pH
○ Natural body pH ~ 7.4
○ Drinking water pH: 6.5 - 8.5
● Decreased specific gravity
○ Specific gravity of water is 1
○ pmaterial/ pwater → increased water intake dilutes materials and brings ratio closer to 1
● Decreased sodium
○ Dilutes sodium in blood, urine will have a higher water:sodium ratio
● Increased creatinine clearance
○ Increases blood flow to glomeruli → more creatinine is being filtered out
● Controlled by AVP/ADH and ANP
○ Reduces AVP activity → reduces kidney activity in reabsorbing water
○ Low pressure barorecepters sense changes in BP (generally higher because of increase in blood
volume) → releases ANP → inhibits thirst and stimulates water excretion
164
Isotonic Gatorade
Isotonic: same osmotic concentration as a normal body fluid
● Increase in volume
○ Only a percentage of liquid gets reabsorbed, excess fluid gets excreted
● No change or slight decrease in pH
○ Consumed solution might have some acidic components
● No change in specific gravity
○ Osmotic concentration is the same, ratio of material to water should stay similar
● No change in slight increase in sodium or no change at all
○ Reabsorption at PCT and LOH is inhibited → more sodium excretion
● Increased creatinine clearance
○ Increased blood flow to glomerulus → increased filtration rates
● Controlled by: ANP
○ Low pressure baroreceptors sense increase in BP (increase in BV) → release of
ANP → increases excretion of sodium by inhibiting reabsorption
165
Alkalotic bicarbonate
No change in volume
○ Too little volume consumed
● Increase in pH
○ Increase in [HCO3-] in the blood
○ Reabsorption of bicarbonate in the PCT and LOH is about 80% and 20%, excess
is excreted
● No change in specific gravity
○ Small increase may occur, excreted bicarb can increase material:water ratio
● No change in sodium
○ Too little volume consumed
● No change in creatinine clearance
○ Too little volume consumed
● Controlled by: Type B intercalated cells that are used to excrete HCO2- to return
blood pH to homeostatic range (found in PCT, generally dispersed throughout the
nephron)
