general physiology final exam

dalton’s law

total pressure of a mixture of gases is the sum of the individual partial pressures exerted by each gas

barometric pressure value at sea level

760 mmHg

barometric pressure

sum of all gas partial pressures in ambient atmospheric air

partial pressure og a gas in atmospheric air formula

fractional concentration times barometric pressure

Px = PB x Fx

what determines passive net flux of a gas (magnitude and direction of gas flux

differences in the partial pressure of a particular gas

gradients

how does partial pressure of oxygen change through the path it takes to the mitochondria?

decreases from air to

alveolar gas, to

arterial blood, to

systemic capillary blood, to

mitochondria

what is the normal gas pressure of O2 in the atmosphere and alveoli?

atmosphere: 160 mmHg

alveoli: 105 mmHg

O2 moves from high to low pressure, from atmosphere to alveoli

what is the normal gas pressure of CO2 in the atmosphere and alveoli?

atmosphere: 0.3 mmHg

alveoli: 40 mmHg

CO2 moves from high to low pressure, from alveoli to atmosphere

is there an active transport mechanism for O2?

no

what is the effect of altitude on the oxygen cascade?

high altitude decreases barometric pressure but not % of oxygen in air (which is always 29.5%)

decreases pO2 in atmosphere

decreases alveolar pO2

decreases arteriolar pO2

explain the variation in gas partial pressures in the cardiorespiratory system

Pulmonary arteries:

• systemic blood in the pulmonary capillaries has low PO2 (40) and high PCO2 (46)

• Alveoli have higher PO2 (105) and lower PCO2 (40)

• O2 moves into the pulmonary veins

• CO2 moves out of into alveoli

Pulmonary veins

• Blood becomes oxygenated (100) with less CO2 (40)

• Blood moves from pulmonary veins into the left heart, then to the systemic arteries

Systemic arteries

• Blood is oxygenated (100) with less CO2 (40)

• Tissue capillaries have lower PO2 (40) and higher CO2 (46)

• O2 moves into tissue capillaries

• CO2 moves into systemic veins

Systemic veins

• Blood becomes deoxygenated (40) with more CO2 (46)

• Blood moves from systemic veins into right heart, then to the pulmonary arteries

what does blood PO2 refer to?

partial pressure of O2 dissolved in plasma

O2 poor blood entering the pulmonary capillaries has PO2 = ?

40 mm Hg
Equivalent to PO2 of mixed blood

O2 rich blood exiting the pulmonary capillaries has PO2 = ?

100 mm Hg

Equivalent to alveolar PO2 and systemic arterial blood

when is diffusion equilibrium reached?

1/3 along the length of the pulmonary capillary

what percent saturation are RBCs when entering pulmonary capillaries?

75%

what percent saturation are RBCs when exiting pulmonary capillaries?

100%

what affects lung diffusing capacity, DL?

surface area (Increased surface area increases DL)

diffusion distance (increased distance decreases DL)

where is the majority of O2 in the blood?

bound to hemoglobin

rest is physically dissolved (1.5%)

explain the structure of hemoglobin

• tetramer

• 2 alpha globin polypeptides

• 2 beta globin polypeptides

  • each posesses a heme group: poryphyrin ring with central Iron that binds to O2

what are the two configurations of heme groups?

oxyhemoglobin

• HbO2

• with bound oxygen

deoxyhemoglobin

• Hb

• without bound oxygen

how do you calculate % Hb saturation?

• # of heme groups with bound O2

• divided by total # of heme groups among all Hb molecules

• times 100

explain the oxygen-hemoglobin dissociation curve

• non-linear function of blood PO2

• As plasma PO2 decreases, O2 dissociates from Hb

• As plasma PO2 increases, O2 binds to Hb

• Slope increases at lower PO2s and then it flattens out

• PVO2 = 100

• PVCO2 = 40

what is P50?

measure of Hb’s overall affinity for O2

PO2 at which Hb is 50% saturated with O2

explain trends of partial pressure in O2 blood released by tissues

blood at high partial pressures must fall greatly to release the same amount of of oxygen from blood, but at lower partial pressures it must only fall a little to release the same amount

what factors decrease Hb’s affinity for O2? what do they cause?

1. decrease in pH

   1. from higher H+ or higher PCO2

2. increase in temperature

3. increase in [2,3-diphosphoglycerate]

these cause a right-shift of the O2-Hb dissociation curve, aka increase in P50

bohr effect

right shift of O2-Hb dissociation curve due to low pH

explain right shift

p50 increases

Hb affinity decreases

less O2 bound to hemoglobin

more O2 released into plasma and available to diffuse into tissues

how does exercise affect Hb-O2 affinity?

lactic acid build up

increase in [H+]

increase in body temperature

right shift

hemoglobin is less saturated and O2 is available

how is CO2 incrementally transported in the blood?

• 20% carbamino hemoglobin

• 70% bicarbonate ions

carbamino hemoglobin

CO2 + Hb → HbCO2

• CO2 attaches to hemoglobin on amino acid sequences without blocknig O2 binding spots

bicarbonate ions

CO2 + H2O → H2CO3 → HCO3 + H+

• catalyzed by carbonic anhydrase within RBCs

how are alveolar and arterial PO2 related to alveolar ventilation rate?

proportional

how are alveolar and arterial PCO2 related to alveolar ventilation rate?

inversely

hypoventilation

CO2 retention in bloodstream and alveoli

inadequate O2 uptake

increase in PCO2

decrease in PO2

hyperventilation

excessive CO2 elimination from blood and alveoli

excessive O2 uptake

decrease in PCO2

increase in PO2

what is the integrating center for control of ventilation rate?

medullary respiratory center

what are the inputs to the MRC?

peripheral chemoreceptors

central chemoreceptors

peripheral chemoreceptors

• located in carotid and aortic bodies

• monitor arterial PO2, PCO2, and H+

central chemoreceptors

• located in brain

• monitor brain ECF for H+

explain hypoxemia

• hypoxemia: low PO2 in arterial blood

• stimulates peripheral chemoreceptors

• increases minute ventilation rate

  • relatively insensitive

explain hypercapnia

• hypercapnia: high PCO2 in blood

• stimulates peripheral chemoreceptors

• increases minute ventilation rate

  • chemoreceptors are more sensitive to changes in PCO2

ventilation rate reflex arc:
stimulus

• low PO2

• high PCO2

• high H+

in arterial blood

ventilation rate reflex arc:
sensory receptors

glomus cells of carotid and aortic bodies

ventilation rate reflex arc:
afferent pathways

• carotid → glossopharyngeal

• aortic → vagus nerve

ventilation rate reflex arc:
integrating center

MRC

ventilation rate reflex arc:
efferent pathway

phrenic nerve

ventilation rate reflex arc:
effector

diaphragm

ventilation rate reflex arc:
response

• increased diaphragm contraction rate

• increased minute ventilation rate

exocrine

secretes products via ducts

ie. salivary, sweat, secretory glands

endocrine

ductless

secrete hormonal products into bloodstream

things that compose the endocrine system

• all tissues that secrete hormones into the bloodstream

  • hypothalamus

  • anterior/posterior pituitary

  • thyroid

  • adrenal glads

  • pancreas

  • ovaries/testes

hormone

chemical messenger released into bloodstream

binds to target receptors to produce specific actions in target tissues

how can hormones be released into the blood?

1. epithelially derived cells

2. neurons

   1. neuron gets synaptic input in response to AP and released chemical via exocytosis into bloodstream

generalizations about the endocrine system

1. a single endocrine gland may secrete multiple hormones

2. single hormone may have diverse effects

3. single process may be regulated by multiple hormones

4. hormones are effective at low concentrations

redundancy

hormones that serve the same purpose

example: glucagon and cortisol increase glucose concentration in blood

how are hormones classified by secretory cell type?

1. classical hormones: released by epithelially derived cells

2. neurohormones: released by neurons

how are hormones classified by chemical class?

1. amine

2. peptide

3. steroid

types of amine hormones

1. catecholamines

   1. neurohormones

   2. derived from Tyrosine

2. thyroid hormones

   1. classical hormones

   2. derived from Tyrosine

3. melatonin

   1. neurohormone

   2. derived from tryptophan

types of catecholamines

1. dopamine

2. norepinephrine

3. epinephrine

dopamine

• secreted by hypothalamus

• inhibits proactin release via anterior pituitary

norepinephrine and epinephrine

• secreted by adrenal medulla

• early-phase acute stress response

• liver and skeletal muscle glycogenolysis

types of thyroid hormones

1. thyroxine (T4)

2. tri-idothyroxine (T3)

effects of thyroid hormones

stimulatory effects on metabolic rate

calorgenic: burns calories to increase metabolic rate

thermogenic: increased body temperature as byproduct

melatonin

secreted nocturnally by pineal glad

regulates clock gene expression by mammalian circadian clock, suprachiasmatic nucleus og hypothalamus (SCN)

what are included in peptide hormones?

• all major hormones of hypothalamus except dopamine

• all major hormones of anterior/posterior pituitary

• pancreatic hormones

• angiotensin II

• insulin

post-translational modification/release of peptide hormones

1. preprohormone cleaved enzymatically in rough ER to form prohormone

2. prohormone packaged into secretory vesicles by Golgi apparatus

3. prohormone enzymatically cleaved within secretory vesicles to form active hormone

4. active peptide hormone released into interstitial fluid via exocytosis and enters bloodstream

types of steroid hormones

1. hormones of adrenal cortex

2. hormones of the gonads

hormones of adrenal cortex

1. aldosterone

2. glucocorticoids

aldosterone

mineralcorticoid

renal Na+ reabsorption

K+ secretion

glococorticoids

cortisol/corticosterone

delayed phase acute stress responses

liver gluconeogenesis (from scratch)

hormones of the gonads

1. testosterone

2. estradiol

3. progesterone

what converts testosterone → estradiol?

aromatase

explain the mechanism for peptide and non thyroid amine hormones

• polar and hydrophillic → can’t enter target cell

• released via exocytosis

• bind to cell-surface receptors

  • GPCRs

  • enzyme linked receptors

• effects

  • change in enzyme phosphorylation state/activity

  • change in ion channel activity

explain the mechanism of action for steroid and thyroid hormones

• nonpolar/hydrophobic/lipophobic

• released via simple diffusion

• transport bound to carrier proteins

  • albumin: nonselective carrier protein

  • globulin: selective carrier protein

• bind to intracellular receptors

  • cytoplasmic

  • nuclear

• intracellular effect: change in gene expression

hypothalamus pituitary axis (HPA)

possess neurons that release hormones

• posterior pituitary secretes neurohormones

• anterior pituitary secretes classical hormones

posterior pituitary

• hypothalamus contains

  • paraventricular nuclei (PVN)

  • supraoptic nuclei (SON)

• these contain magnocellular neurons that release neurohormones

paraventricular nuclei (PVN)

releases oxytocin and some agrinine vasopressin

supraoptic nuclei (SON)

releases arginine vasopressin

arginine vasopressin

• inreases renal H2O absorption, increases plasma volume

• vasocontriction (increases BP)

oxytocin

increases uterine wall smooth muscle contractions

increases milk ejection from mammary glands during nursing

anterior pituitary

• non neural, epithelially derived

• secretes classical hormones

• parvocellular neurons of hypothalamus secrete hypophysiotropic hormones

• hypophysiotropic hormones travel through hypothalamo-hypophysial portal vessels

• third gland secretes classical hormone

types of hypophysiotropic hormones

• releasing hormones

• inhibiting hormones

regulation of growth hormone secretion

1. hypothalamus:

   1. GHRH (growth hormone releasing hormone)

   2. GHIH (growth hormone inhibiting hormone)

2. anterior pituitary:

   1. growth hormone

3. 3rd gland: IGF-1 (insulin-like growth factor) causes protein synthesis and linear bone growth

regulation of prolactin secretion

1. hypothalamus: dopamine (inhibition)

2. anterior pituitary: prolactin

   causes growth of mammary glands and milk productio

folicular cells of thyroid

contain colloid within lumen of follicles

trap iodine in

thyroid hormone mechanism

1. thyrotropin-releasing hormone (TRH)

2. thyroid stimulating hormone (TSH)

3. thyroxine (T4) → Triiodothyroxine (T3)

increases metabolic heat production in response to T3

increase non-shivering thermogenesis (calorgenic and thermogenic)

T3

deiodated active form

binds to nuclear receptors to alter rates of gene expression

how do goiters form?

pituitary gland increases production of thyroid-stimulating hormone (TSH)

stimulates the thyroid to grow in an attempt to compensate (negative feedback)

layers of adrenal gland and what they form?

adrenal cortex

1. zona glomerulosa: aldosterone

2. zona fasiculata: cortisol and androgens

   adrenal medulla

3. zona reticularis: epi/NE

mechanism of chronic stress response of cortisol

1. hypothalamus: corticotropin-releasing hormone (CRH)

2. anterior pituitary: adrenocorticotropic hormone (ACTH)

3. adrenal cortex: cortisol (CORT)

causes liver gluconeogenesis

lipolysis in fat tissue

extrahepatic proteolysis

what produces ACTH?

in anterior pituitaru

by enzymatic cleavage of proopiomelanocortin (POMC)

hypothalamo-pituitary gonadal axis in females

hypothalamus: gonadotropin releasing hormone (GnRH)

anterior pituitary: FSH and LH

ovaries: estradiol (follicle maturation) and triggers ovulation of mature follicles

hypothalamo-pituitary gonadal axis in males

hypothalamus: gonadotropic releasing hormone (GnRH)

anterior pituitary: FSH and LH

testes: spermatogenesis and testosterone (secondary sex characteristics)

ovarian follicle

oocyte surrounded by supportive endocrine cells (granulosa and theca)

follicular phase

FSH stimulates estradiol from granulosa cells

stimulates follicle maturation and proliferative phase

proliferative phase

growth of endometrium stimulated by estradiol in follicular phase

ovulation

LH surge

luteal phase

progesterone secreted by corpus luteum prepares endometrium for implantation and pregnancy

inhibits uterine smooth muscle contraction until late pregnancy

three cell types of the islets of langerhands

1. alpha cells: secrete glucagon

   1. liver glygogenolysis

2. beta cells: secrete insulin

   1. liver and skeletal muscle glycogenolysis

   2. liver and fat cell lipogenesis

3. delta cells (δ): somatostatin

   1. inhibits digestion/absorption