week 8

Question 1

what does Hb bind to and carry

Answer 1

Hb binds and carries O2 from the lungs to the tissues (iron is required for O2 binding to the Heme group of hemoglobin)

Hb binds and carries CO2 from the tissues back to the lungs

Question 2

the more O2 bound to 1 Hb molecule …

Answer 2

… the stronger the bond

once Hb loses its first O2, it changes shape and has a lower affinity for the remaining 3. The last O2 is the least tightly bound to Hb

Question 3

factors that decrease the affinity of O2-Hb binding

Answer 3

increased temp, decreased pH, increased PCO2 in the blood

Question 4

list the 3 methods of transport of CO2 in the blood

Answer 4

1. dissolved in the blood plasma (7-10% of CO2)
2. bound to hemoglobin: carbaminohemoglobin (20% of CO2)
3. as HCO3- (bicarbonate) in the blood (70%)

Question 5

what enzyme catalyzes the reaction of CO2 to HCO3-

Answer 5

carbonic anhydrase

HCO3- is reconverted to CO2 once it reaches the pulmonary capillaries

Question 6

what is the pH of blood under normal conditions

Answer 6

7.34-7.45 - maintained by HCO3-

Question 7

hyperventilation vs. hypoventilation effect on blood PCO2

Answer 7

more CO2 expired = low blood PCO2

less CO2 expired = high blood PCO2

Question 8

describe eupnea

Answer 8

normal breathing, one of the most vital functions body carries out as absence of breathing leads to death

Question 9

define chemoreceptors

Answer 9

specialized cells that respond to changes in concentration of specific chemical

Question 10

what are central and peripheral chemoreceptors

Answer 10

specialized cells that detect changes in PCO2, PO2 and H+ in the blood and cerebrospinal fluid - in order to control the rate and depth of ventilation

Question 11

where are central chemoreceptors found

Answer 11

in the medulla - they detect changes in PCO2 and in H+ by monitoring levels in the cerebrospinal fluid - signal sent to regulate rate and depth of breathing in order to return to levels of normal

Question 12

where are peripheral chemoreceptors found

Answer 12

in the aorta and carotid arteries - they detect changes in PCO2, H+ and PO2 (<70mmHg) - signal sent to medulla to increase rate and depth of ventilation

Question 13

where does digestion begin

Answer 13

the oral cavity

Question 14

where does most digestion occur

Answer 14

the stomach

Question 15

where does most nutrient absorption occur

Answer 15

the small intestine

Question 16

what are macronutrients used for

Answer 16

used for fuel and as building blocks for many components in the body

• carbs
• fats
• protein

Question 17

what are micronutrients used for

Answer 17

critical components in all physiological processes

• vitamins
• minerals

Question 18

what is the primary goal of the digestive system

Answer 18

to break food down in order to get all nutrients into absorbable units

Question 19

what is the role of the alimentary canal (gastrointestinal (GI) tract

Answer 19

• food moves through this continuous passage (a 9m tube)
• sphincters regulate flow from one compartment to the other

Question 20

accessory organs

Answer 20

• assist in GI processes
• secretion into the lumen of the GI tract

Question 21

define digestion

Answer 21

chemical and mechanical breakdown of food into absorbable units

Question 22

define absorption

Answer 22

nutrients, water and electrolytes are moved from the GI lumen to circulation

Question 23

define secretion

Answer 23

endocrine and exocrine glands secrete substances into the lumen

Question 24

define motility

Answer 24

mvmt of material through the GI tract

Question 25

what are the 4 layers of the wall of the GI tract

Answer 25

1. inner epithelium (mucosa) - the innermost component - a layer of epithelial cells: simple columnar epithelium, with many goblet cells (mucus coats the entire epithelium of the GI tract) 2. layer of connective tissue (submucosa) - contains the submucosal plexus (nerve network) 3. layer of smooth muscle (muscularis externa) - 2 layers of smooth muscle - contains the myenteric plexus (nerve network) 4. outer layer of connective tissue (serosa)

Question 25

how does the body maintain homeostasis in terms of digestion

Answer 25

in order to maintain homeostasis, the volume of fluid entering the GI tract by intake or secretion must equal the volume leaving the lumen

Question 25

what are the basic functions of the digestive system (digestion, absorption, secretion and motility) regulated by?

Answer 25

they are regulated by endocrine and nervous systems - the autonomic nervous system and enteric nervous system (a branch of the ANS that is completely contained within the GI tract)

Question 25

describe peristaltic contractions

Answer 25

peristaltic contractions occur when circular muscles contract just behind the bolus of food - there is a direction of movement

Question 26

describe segmental contractions

Answer 26

segmental contractions occur when segments of smooth muscle alternatively contract and relax - there is no net forward movement

Question 27

what are the 3 phases of regulation

Answer 27

1. cephalic phase 2. gastric phase 3. intestinal phase

Question 28

REVIEW SLIDE 12 (MAR 7)

Question 29

describe the cephalic phase

Answer 29

- the cephalic phase is mediated by the vagus nerve which carries an output from higher order brain centers - this phase prepares the GI tract in advance for incoming food - it is activated in response to sight, smell, taste, and even thought of food - it stimulates saliva production, gastric and pancreas secretions, and GI hormone release

Question 30

describe the oral cavity and its role in digestion

Answer 30

main digestive functions: - mechanical and chemical digestion, secretion, and propulsion - chewing initiates the process of mechanical digestion - saliva secretions moisten and soften food, and begin the process of chemical digestion - propulsion of food from oral cavity to the pharynx (throat) to the esophagus through the process of swallowing

Question 31

describe saliva as well as its role in digestion

Answer 31

there are 3 pairs of salivary glands that secrete saliva into the oral cavity: 1. parotid glands 2. submandibular glands 3. sublingual glands saliva consists of: water, electrolytes, mucus, salivary amylase, lysozyme, antibodies, and bicarb ions salivation is regulated by both the parasympathetic (mainly) and sympathetic divisions of the ANS

Question 32

define salivary amylase

Answer 32

enzyme that starts the chemical digestion of carbs

Question 33

what is the role of bicarbonate ions

Answer 33

to help neutralize the acid that may have escaped the stomach

Question 34

outline the swallowing reflex

Answer 34

1. voluntary phase - the tongue pushes the bolus posteriorly towards the oropharynx 2. pharyngeal phase - the bolus enters the oropharynx: the soft palate and epiglottis seal off the nasopharynx and larynx respectively 3. esophageal phase - peristaltic waves move the bolus down the esophagus to the stomach

Question 35

describe the esophagus and its roles in digestion

Answer 35

main functions: propulsion (peristalsis) and secretion (mucous) top end: upper esophageal sphincter bottom end: lower esophageal (gastroesophageal) sphincter

Question 36

what are the 5 anatomical regions of the stomach

Answer 36

1. cardia 2. fundus 3. body 4. pyloric antrum 5. pylorus (contains the pyloric sphincter which controls the flow between stomach and small intestine)

Question 37

REVIEW SLIDE 20 (MAR 7)

Question 38

what are the 3 main digestive functions of the stomach

Answer 38

1. secretion - HCl + intrinsic factor from parietal cells - pepsinogen + gastric lipase from chief cells - hormones from neuroendocrine cells 2. digestion - mechanical digestion through mixing and churning - chemical digestion of protein by the enzyme pepsin - chemical digestion of fat by the enzyme gastric lipase 3. motility - mixing and churning of contents: mechanical digestion and mixing of all the secretions with the food bolus - produces chyme

Question 39

Why do our cells secrete an inactive form of pepsin (pepsinogen)

Answer 39

to protect the cells of these secretory glands from strong protein digesting action of the enzyme

Question 40

describe the gastric phase

Answer 40

distention of the stomach wall from incoming food triggers neurons of the enteric NS and sensory receptor that stimulate the vagus nerve

Question 41

describe the intestinal phase

Answer 41

- triggered by the entry of partly digested protein into the duodenum - followed by inhibition of HCl secretion via the enterogastric reflex. - hormones that inhibit HCl secretion when released: 1. secretin 2. gastric inhibitory peptide

Question 42

describe the motility of the stomach

Answer 42

- receives the bolus from the esophagus by relaxation of the gastroesophageal sphincter, fundus and body of the stomach - mixing and churning of the food into chyme through waves of peristalsis and segmental contractions - chyme released into the small intestine is regulated