Physiology

Question 1

Endocrine - peptides that regulate CV function

ANP

BNP

Answer 1

 ANP [Atrial Natriuretic Peptide] in response to increased atrial pressure

 BNP [B-type Natriuretic Peptide] in response to overstretched ventricles

Question 2

Cardiac muscle

involuntary muscle with cross-__________

individual cells are connected by _______ discs with gap ________ which allow for passage of ions and uniform contraction

Answer 2

o involuntary muscle with cross striations
o the individual cells are connected by intercalated discs with gap junctions
o the gaps junctions allow for the passage of ions between the myocytes
o these allow the action potentials to spread between the cardiac myocytes
o the intercalated discs allow the heart to contraction in synchrony as one unit [syncytium]

Question 3

Cardiac muscle contraction phases

Phase 0 - rapid depolarization 
Phase 1 - initial repolarization
Phase 2 - plateau
Phase 3 - rest of repolarization
Phase 4

Answer 3

 Phase 0: Na + influx into cardiac myocytes causes rapid depolarization-the rapid upstroke

 Phase 1: inactivation of fast Na + with K + efflux with a notch of initial repolarization

 Phase 2: Ca ++ influx through L-type Ca ++ channels-the plateau phase

 Phase 3: inactivation of Ca ++ channels with K + efflux-rest of repolarization

 Phase 4: removal of excess Na + and Ca ++ with restoration of membrane potential

Question 4

Cardiac muscle contraction phases

Absolute vs. relative refractory periods

Answer 4

i. absolute-no action potential can be initiated regardless of the stimulus strength
because the Na channels are closed as in Phase 1 and 2

ii. relative-an action potential can be elicited, however a greater stimulus is
needed-extends between the middle of Phase 3 to the start of Phase 4

iii. cardiac musce is incapable of sustained contration [tetany] as in skeletal muscle
because of the refractory period

Question 5

Frank-Starling law

What is directly proportional to venous return?

Answer 5

cardiac output (CO)

The Frank-Sterling Law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume ) when all other factors remain constant.

i. force of contraction of a myocardial fiber is proportional to the length of the
myocardial fiber
ii. the greater the amount of blood entering the heart during diastole [venous
return], the greater is the stretching of the cardiac myocytes
iii. greater stretch results in a greater force of contraction resulting in an increase
in the cardiac output
iv. Cardiac output is the volume of ejected blood from the heart per minute

Question 6

Cardiac cycle and heart sounds

1st HS
Systole (contraction)
2nd HS
3rd HS
4th HS
Diastole (relaxation)

Answer 6

 1st heart sound due to the closure of the tricuspid and mitral valves [LUB]
 2nd heart sound due to the closure of the pulmonary and aortic valves [DUB]
 3rd heart sound occurs after the 2nd heart sound-congestive heart failure [DUBup]
 4th heart sound is heard just before 1
st heart sound-hypertrophic ventricles [beLUB]

 systole [contraction] occurs between heart sounds 1 and 2
 diastole [relaxation] occurs between heart sounds 2 and 1

Question 7

Intrinsic bpm of the SA node

Intrinsic bpm of the AV node

Answer 7

SA: 80-100 bpm

AV: 40-60 bpm

Superimposed impulses of SA + AV results in the average 70 bpm.

Question 8

T or F: conduction velocity is slowest at the AV node and fastest towards the Purkinje fibers

Answer 8

T

Question 9

ECG

P wave
PR interval
QRS
QT interval
ST segment
T wave

Answer 9

o P wave represents atrial depolarization
o PR interval-extends from the P wave to the start of the Q wave [,200 milliseconds]
o QRS complex-represents ventricular depolarization [<120 milliseconds]
o QT interval-extends from the beginning of the Q wave to the end of the T wave
o ST segment-extends from the end of the S wave to the start of the T wave
o T wave-ventricular repolarization
o Atrial repolarization is not seen on the ECG because it is buried by the QRS complex
o In some people there may be a U wave after the T wave
o The U wave may represent repolarization of the Purkinje fibers or the papillary muscles

Question 10

2 main mechanisms that regulate BP

baroreceptors - why is this one a very fast response?

renin-angiotensin-adolsterone (RAA)

Answer 10

baroreceptors - fast due to NT

o baroreceptors located in the carotid sinus and in the aortic arch [afferents are carried
by CN IX and CN X respectively] relay pressure information to the brain stem
o there is a reflexive response to a rise or drop BP via sympathetic or parasympathetic
system
o a drop in the blood pressure will cause the heart rate to increase

renin-angiotensin-adolsterone (RAA) - slow due to hormones

Question 11

Blood flow is inversely proportional to _________ of the blood vessel

How about resistance?

Answer 11

diameter

smaller the diameter, the more resistance

Question 12

4 capillary pressures

IC HS
IC oncotic
ISHSP
IS oncotic

Answer 12

 intracapillary hydrostatic pressure which tends to force fluids out into the interstitial space [+]
 intracapillary oncotic [protein-related] pressure which tends to pull fluids into the capillary [-]
 interstitial hydrostatic pressure which forces fluids into the capillary [-]
 interstitial oncotic pressure which pulls fluid out of the capillary [+]

Question 13

Anterior pituitary lobe (adenohypophysis) - secretes hormones under the influence of releasing factors (with one exception) from the (hypothalamus)

What are the 6?

Answer 13

ACTH
FSH
LH
GH
TSH
PRL

Question 14

Where are each of these?

 GLUT 1 (2)
 GLUT 2 (2)
 GLUT 3 (1)
 GLUT 4 (2)

Answer 14

 GLUT 1 erythrocytes and brain
 GLUT 2 liver and beta islet cells
 GLUT 3 neurons
 GLUT 4 skeletal muscle and adipose tissue

Question 15

Growth Hormone Inhibitory Hormone (somatostatin) - which hormones does it inhibit?

RIGGG

Answer 15

  Renin 
  Insulin 
  Growth hormone 
  Gastrin 
  Glucagon

Question 16

Enzyme in the mouth when you are chewing food?

Answer 16

amylase - breaks down carbs and starches into maltose

Question 17

Gastric glands contain 3 types of cells

Answer 17

mucosal (neck) cell - mucus, gastrin

chief cells - pepsinogen

parietal cell - HCl (activates pepsinogen) and intrinsic factor

Question 18

Bacteria in which intestine produces vitamin K

Answer 18

large intestine

Question 19

What do you need to absorb Vit B12

Answer 19

intrinsic factor

Question 20

Folic acid and iron is absorbed where?

Answer 20

jejunum

Question 21

Role of the liver

Answer 21

 carbohydrate metabolism: glycogenesis, glycogenolysis and gluconeogenesis
 protein metabolism: builds proteins
 lipid metabolism: makes fat and cholesterol
 stores glycogen and vitamins A, D and B 12
 detoxifies toxic substances such as hormones, drugs, poisoning including alcohol
 conjugates bilirubin
 produces antibodies
 makes steroid hormones
 manufactures clotting factors
 makes red blood cells in the fetus
 involved in the immune system through the Kupffer cells

Question 22

Role of the gallbladder

Answer 22

 stores bile [approximately 50 cc] and concentrates bile
 excretes bile in response to the presence of fat in the duodenum
 controlled by cholecystokinin by the small intestine when fat enters the duodenum
 cholecystokinin causes the contraction of the gallbladder

Question 23

 totipotent
 pluripotent
 unipotent

these cells are located in the marrow in the _____ and in the liver, spleen, lymph nodes and bone marrow in the ____

Answer 23

 totipotent cells give rise to any and all cell types
 pluripotent cells may give rise to several cell types
 unipotent cells can only develop into one cell type

these cells are located in the marrow in the adults and in the liver, spleen, lymph nodes and bone marrow in the fetus

Question 24

2 blood cell lineages

Answer 24

myeloid and lymphoid

Question 25

lymphoid cell line gives rise to two cell lines:

myeloid cell line gives rise to several cell lines (4)

Answer 25

o B cells [activated in the Bone marrow]: plasma cells
o T cells [activated in the Thymus]: lymphocytes

o erythroblasts which develop into reticulocytes and finally adult red blood cells
 stimulated by erythropoietin released by the kidney
o granulocytes which develop into basophils, eosinophils and neutrophils
o monocytes which become macrophages once they migrate into the tissues
o megakaryocytes which develops into platelets

Question 26

Granulocytes

Agranulocytes

Answer 26

basophils, eosinophils, neutrophils

lymphocytes and monocytes

Question 27

Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils

Answer 27

Bacteria

Viral or chronic infections

Macrophage activity

Parasitic infection

Hypersensitivity or allergies

Question 28

Phagocytosis

2 main cell types

Answer 28

neutrophils and macrophages

Question 29

2 major subdivisions of immunity

Answer 29

non-specific (innate)

specific (acquired after exposure)

Question 30

Nonspecific or Innate Immunity

Complement activation - OILCAN

Answer 30

 Opsonization which makes target cells more susceptible to phagocytosis. Complement fragments known as opsonins bind to the surface of bacteria. Phagocytic cells with receptors for these fragments become attached to the
opsonized bacteria. Thus increasing the binding of bacteria for phagocytosis [C3b]
 Inflammation by activation of mast cells in anaphylaxis [C3a, C4a and C5a]
 Lysis due to the increased efficiency of bacterial phagocytosis [C5b6789]
 Chemotaxis to attract specific white blood cells [C5a]
 Agglutination: changes the surface of the invading bacteria making them sticky
 Neutralization of toxic sites on the surface of the antigen

Question 31

Specific or Acquired Immunity

involves the production of antibodies against specific foreign antigens by ____________

can also be mediated by cell-mediated or _______ (antibody) responses

products of immune cells include: TICIT

antibody mediated immunity depends on: which two cells?

Answer 31

lymphocytes

humeral (antibodies/immunoglobulins)

o  Tumor Necrosis Factor 
o  Immunoglobulins 
o  Cytokines-interleukins 1-18 
o  Interferons 
o  Transforming Growth factor 

o B lymphocytes
 involved in the generation of humoral immunity
 mature in the bone marrow [Bursa of Fabricius in birds]
 make antibodies in the form of immunoglobulins
o T lymphocytes [95% of circulating lymphocytes]
 mature in the thymus
 involved in cell-mediated immunity
 through the production of activated T lymphocytes

Question 32

Differentiation of T cells

Answer 32

 T cell precursors in the bone marrow go to the thymus where they differentiate into CD8 or CD4 T
cells
 The CD8 T cells become Cytotoxic T cells which kill virus-infected, neoplastic and donor graft cells
 The CD4 T cells further differentiate into Helper T cells which develop into Th 1 and Th 2 cells. Th1 cells activate macrophages. Th2 cells help B cells to make antibodies

Question 33

IgG
IgA
IgM
IgD
IgE

Which one is most abundant?

Answer 33

o IgG-most abundant, promotes phagocytosis and cell lysis, confers passive immunity
o IgA-present in saliva, tears and breast milk
o IgM- secreted early on, promotes agglutination, phagocytosis and cell lysis
o IgD-surface antibody on B lymphocytes, role unclear
o IgE-important in parasitic infections and some allergic responses

Question 34

Cell-mediated Immunity relies on activated T lymphocytes. This is important to fight against viral and fungal infefctions and potential cancer cells.

3 types of T lymphocytes are….

T or F: cell-mediated responses are persist for shorter periods of time compared to anti-body responses.

Answer 34

o cytotoxic [killer] T lymphocytes:
 lyse cells carrying the antigens to which they are sensitive
o helper T lymphocytes [most numerous]
 activated by macrophage-processed antigens
 once stimulated, lymphokines are released: Interleukin 2-6 and Interferon
o suppressor T lymphocytes:
 inhibit lymphocytic function

F

Question 35

Hypersensitivity Reactions [ACID]

Answer 35

o Type I-Anaphylactic
o the antigen reacts with IgE causing mast cells to release histamine, heparin, as seen in
allergies and asthma

o Type II-Cytotoxic
o IgG, IgM, destroys RBCs-erythoblastosis fetalis, acute transfusion reaction, ITP

o Type III-Immune complex
o IgG mediated-immune complex triggers inflammation, as seen in serum sickness, drug
reactions, SLE, RA, post-streptococcal glomerulonephritis andfarmer’slung

o Type IV-Delayed hypersensitivity
o T cell mediated as seen in Mantoux testing for TB, leprosy, Touching poison ivy contact dermatitis, chronic Transplant rejection and Type 1 Diabetes mellitus
o No immunoglobulins are involved in this type of reaction

Question 36

Sarcomere anatomy

thick vs. thin filaments

Answer 36

 the sarcomere is the functional unit of a muscle:
o it lies between two Z lines which bisects the I band
o the dark band is the A [anisotropic] band which has both actin and myosin
o H band bisects the A band and has only myosin [thick filaments]
o the light band is the I [isotropic] band and has only actin [thin filaments]
o the A band always remain the same length during contraction
o the HIZ bands shorten during contraction

o the thick filaments contain myosin
o the thin filaments contain actin, troponin and tropomyosin

Question 37

Three types of troponin

Answer 37

 Troponin C binds to calcium ions
 Troponin T binds to tropomyosin
 Troponin I binds to actin and inhibits the interaction between actin and myosin
 Troponin is the calcium-binding protein in skeletal and cardiac muscle

Question 38

NMJ action potential

Answer 38

 the neuromuscular junction is a specialized region where the ends of the axons of the α-motor
neurons are connected to motor end plates of a specific group of muscle fibrils
 each NMJ has a nerve bouton that is filled with vesicles that release Acetylcholine when the
nerve is stimulated and calcium flows into the bouton
 released Acetylcholine passes through the presynaptic membrane and into the synaptic cleft
 the post-synaptic membrane [motor end plate] on the muscle contains nicotinic ACh receptors
 when acetylcholine binds with these receptors, an end plate potential is generated and this spreads
to cause the skeletal muscle to contract
 the enzyme acetylcholinesterase is found in the synaptic cleft

Question 39

Skeletal muscle contraction (sliding filament theory)

Answer 39

 The action potential arrives at the end of the motor neuron
 Acetylcoholine is released
 Acetylcholine binds to receptors in the motor end plate
 This changes the permeability of the sarcolemma so that sodium rushes in generating an
action potential
 The action potential in the muscle passes into the T tubules
 This releases calcium from the cisterna of the sarcoplasmic reticulum
 Calcium binds to Troponin C causing the troponin to change its shape
 This change causes a shift in Tropomyosin exposing the binding sites on actin for myosin
 Myosin binds with Actin forming a cross bridge
 The myosin head pivots and pulls the actin closer [the sliding filament theory] using 1 ATP
 During relaxation, Ca
++ is pumped back into the sarcoplasmic reticulum by Ca++
ATPase
 This requires energy and the speed at which the sarcoplasmic reticulum pumps the Ca
++ back in
will determine whether the muscle is a fast [Type I] or slow twitch [Type II] fiber
 Repetitive stimulation results in tetany [sustained contraction without relaxation]

Question 40

Slow Twitch [1 Small Slow Red Ox]

Fast Twitch [2 Fast Skinny White Chickens]

Answer 40

Type 1 - red (more myoglobin), long distance runners, smaller, less glycogen, mitochondria

Type 2 - whiter, sprinters, large, more glycogen, few mitochondria

Question 41

3 main types of motor reflexes

Answer 41

flexor withdrawal reflex

crossed extensor reflex

stretch or deep tendon [myotactic] reflex

Question 42

flexor withdrawal reflex

Answer 42

 consists of a painful stimulus in the skin passing along afferent [sensory] axons of A-delta and
class C dorsal root fibers located in the dorsal root ganglion
 its dendrites synapse in the dorsal horn of the spinal cord with an interneuron which in turn
synapses with an alpha motor neuron located in the ventral horn
 from here, the axon of the motor neuron [efferent] innervates a flexor muscle which allows the
limb to be withdrawn from the painful stimulus
 this is an example of a somatosomatic reflex

Question 43

crossed extensor reflex

Answer 43

 is activated by a noxious stimulus of the skin
 this excites A-delta and class C dorsal root fibers
 these fibers enter the spinal cord at the dorsal root and activate multiple interneurons within the
gray matter
 through polysynaptic pathways, the interneurons are connected to the extensor muscles on
both sides of the spinal cord
 so while the flexor withdrawal response is being facilitated by contraction of the flexor muscles on
the side of the stimulus, the interneurons facilitate the contraction of the extensors on the
opposite limb
 this provides support of the body during withdrawal of the affected limb as a righting reflex

Question 44

stretch or deep tendon [myotactic] reflex

Answer 44

 striking a muscle tendon with a reflex hammer causes the muscle spindle in the muscle to be
suddenly stretched
 this sudden stretch generates an impulse which travels along an afferent neuron
 this neuron synapses with the alpha motor neuron that innervates the stimulated muscle
 the stimulated muscle contracts
 at the same time a small branche from the afferent axon synapses with another small neurone
called a Renshaw cell which in turn synapses with the same alpha motor neuron
 Glycine is the neurotransmitter for the Renshaw cells which are located in Lamina IX
 the Renshaw cell generates an inhibitory impulse which causes the antagonist muscle to relax
 this stretch reflex is further modified by inhibitory influences from the brain
 these influences prevent the reflex from being too brisk
 removal of these inhibitory impulses will result in the deep tendon reflex being hyperactive

Question 45

Types of nerve endings

Answer 45

 Merkel cells are found in the epidermis-crude touch and pressure
 Pacinian corpuscles are found deep subcutaneous tissue-vibration
 Meissner’scorpuscles in the dermal papillae-two-point discrimination [fine touch]
 Ruffini endings are found in deep subcutaneous tissue-joint position sense
 Naked nerve endings are found in the epidermis and dermis-pain and temperature
 Golgi tendon organs found in tendons and detect load or tension
 Muscle spindles found in muscle, detect changes in the length of the muscle

Question 46

NT classification

CNS: all are _______ (GSAND) except which 2?

Answer 46

o All are Excitatory [Glutamine, Serotonin, Acetylcholine, Norepinephrine and Dopamine]
EXCEPT Glycine and GABA [Gamma Amino Butyric Acid which are Inhibitory

Question 47

NT classification

PNS - what is found at NMJ? What are found in the ANS

Answer 47

o  Neuromuscular junction 
  Acetylcholine 
o  Autonomic Nervous System 
  Acetylcholine 
  Norepinephrine

Question 48

T or F: all ANS NTs are cholinergic receptors except sympathetic receptors

T or F: cholinergic receptors in the neuromuscular junction is nicotinic

Answer 48

all cholinergic receptors are nicotinic EXCEPT:
 parasympathetic postganglionic fibers which are muscarinic

T

Question 49

Types of adrenergic receptors

Answer 49

o alpha 1-smooth muscle in blood vessels, gut, sphincters and skin-constriction
o alpha 2-foundinisletsofLangerhan’s-decrease insulin secretion
o beta 1-found in cardiac muscle-increase rate and force
o beta 2-smooth muscle in bronchi, coronary vessels and skeletal muscle-dilation
o beta 3-found in brown fat-increase lipolysis

Question 50

Nerve fiber classification (fastest, largest listed first)

A-alpha
A-beta
A-gamma
A-delta
B
C

Answer 50

AA - motor skeletal muscle
AB - fine touch, vibration, proprio
AG - muscle spindles
AD - fast pain, temperature, touch
B - pre-ganglionic autonomic
C - post-ganglionic autonomic, olfactory, slow pain

Question 51

Functional unit of the kidney = nephron (cortical or juxta-medullary)

two hormones that are secreted by the kidney-

Answer 51

 a glomerulus enveloped in a double-layered Bowman’scapsule
 two convoluted tubules-proximal and distal
 two parts of the loop of Henle-thin descending and ascending thin and thick

erythropoietin and renin

Question 52

Glomerular Filtration

Forces at play during filtration

Answer 52

o hydrostatic [+60 mm Hg] pushes water out of the capillary
o oncotic pressure [-32 mm Hg] pulls water back into the capillary
o Bowman’scapsulepressure[-18 mm Hg] pushes water back into the capillary
o resulting in a positive net pressure of 10 mm Hg

pores [fenestrations] in the capillary membrane, slits between the pedicles of the podocytes in
Bowman’scapsuleandthespecialized negatively-charged basement membrane sandwiched in
between allow free passage of small molecules and the repulsion of negatively charged proteins
 the size of the openings does NOT allow red blood cells to be filtered

Question 53

Proximal Convoluted tubule

Answer 53

 main function of the PCT is related to reabsorption
 most of the bicarbonate and phosphate are reabsorbed by the PCT
 60-70% of Na+
[exchanged for H+], K+, Ca++
and HCO 3 occurs in the proximal convoluted tubule
 H 2 O and urea [50%] is absorbed by the PCT which is lined by cuboid cells with microvilli on the
luminal side
 100% of the filtered amino acids and glucose are reabsorbed here

Question 54

Loop of Henle

Answer 54

 two structurally and functionally different parts of the loop of Henle-thin and thick
 the thin descending part is permeable to H 2 O and impermeable to urea
o purpose is to concentrate the urine as it moves from descending into ascending parts by trapping Na+ and Cl-

o water moves out of the descending limb and the urine becomes concentrated
 the thick ascending part is impermeable to H 2 O and is the diluting segment of the loop

Question 55

Distal Convoluted Tubule

Answer 55

 it is involved in Na + , Cl - , H 2 O and Ca ++ reabsorption
 Aldosterone acts mainly on the distal convoluted tubules to facilitate Na + resorption [in exchange for H + ] and K + secretion
 in addition, Parathormone converts 25 hydroxycholecalciferol to 1, 25 dihydroxycholecalciferol which is the active form of Vitamin D o Vitamin D produced by the skin is converted to 25 hydroxycholecalciferol in the liver
 1, 25 dihydroxycholecalciferol acts on the DCT to facilitate Ca ++ resorption and PO 4 secretion

Question 56

Collecting duct

Answer 56

Anti-Diuretic Hormone acts mainly on receptors in the cells of the collecting ducts and increase
water permeability which allows more water to be reabsorbed

Question 57

Renin-Angiotensin-Aldosterone mechanism:

Answer 57

 drop in renal blood flow results in a decrease NaCl delivery to the macula
densa
 the macula densa is located in the distal convoluted tubule near the afferent
and efferent arterioles of the glomerulus
 it is sensitive to salt [NaCl] concentration
 this triggers the secretion of renin from cells of the juxtaglomerular apparatus
 the juxtaglomerular apparatus is made up of a segment of the distal
convoluted tubule in close relation with the afferent and efferent arterioles of
the glomerulus
 renin is released from the juxtaglomerular cells located in the walls of the
afferent arteriole immediately proximal to the glomerulus
 renin is a proteolytic enzyme which causes angiotensinogen secreted by the
liver to be converted into angiotensin I
 angiotensin 1 is converted to angiotensin II by Angiotensin Converting
Enzyme which is found in the lung
 angiotensin II is a powerful vasoconstrictor which will cause an elevation of
the blood pressure
 in addition, angiotensin II stimulates the release of aldosterone
 aldosterone causes NaCl reabsorption and thus water
 the increased water causes an increase in the blood volume
 this in turn causes an increase in venous return
 increased venous return increases the cardiac output which in turn raises the
blood pressure

Question 58

Anti-Diuretic Hormone [aka vasopressin]

Answer 58

 secreted by the supra-optic nucleus in the hypothalamus
 due to stimulation of osmoreceptors in the hypothalamus
 acts mainly on the principal cells in the collecting ducts of the kidney
 increases water permeability
 causes reabsorption of water

Question 59

Atrial Natriuretic Peptide

Answer 59

 peptide hormone produced by stretched atrial myocardial fibers
 causes decreased Na reabsorption resulting in increased urine production
 also causes relaxation of vascular smooth muscle causing decrease peripheral
resistance

Question 60

The Menstrual Cycle - Proliferative Phase

Answer 60

o after menstruation, the residual basal layer of uterine endometrium regenerates under
the influence of estrogen
o estrogen is secreted by the ovarian follicles under the stimulation of FSH

Question 61

The Menstrual Cycle - Ovulation

Answer 61

o on Day 14 [counting from the 1
st day of menstruation], one Graafian follicle matures and
migrates to the periphery of the ovary to release its ovum covered by a layer of follicular
cells under the stimulation of a pre-ovulatory surge of LH
o this is associated with a 0.50C rise in body temperature at the time of ovulation

Question 62

The Menstrual Cycle - Secretory or Luteal Phase

Answer 62

o the empty ovarian follicle becomes the corpus luteum [yellow] which continues to
secrete estrogen and begins to secrete progesterone under the stimulation of LH
o progesterone will cause the regenerated uterine endometrium to become secretory in
anticipation of implantation of a fertilized ovum

Question 63

The Menstrual Cycle - Menstrual Phase

Answer 63

o if fertilization does not occur, then at about Day 26, the corpus luteum dies [and
becomes the corpus albicans] and the level of progesterone drops precipitously
o this will cause the spiral arteries feeding the endometrium to go into spasm
o this leads to ischemia and death of most of the endometrium
o the dead endometrium is shed as menstrual blood and the cycle is repeated

Question 64

Increased CO 2 and decreased pH cause the oxyhemoglobin to give up O 2 –Bohr effect

Shift towards the

Answer 64

right