Physiology Comp

Question 1

• what are the 2 main fluid compartments:
• what separates them:
• ____ is high in poatssium and ____ is high in Na and Cl
• how permeable is the barrier between the ECF and ICF
• how permeable is the barrier between the 2 components of the ECF
• which of the 2 compartments is called the “internal environment?”

Answer 1

• ECF (interstitial fluid and plasma) and ICF
• plasma membrane
• ICF, ECF
• fairly impermable
• fairly permeable
• ECF

Question 2

what is a homeostatic control system:

what are the 5 components of a control system:

what is set point

Answer 2

controls and maintains homeostasis

receptor, sensory (afferent) pathway, integration center, motor (efferent) pathway, effector organ

preferred value of a homeostatic variable

Question 3

allosteric modulation of protein binding sites

covalent modulation of protein binding sites

Answer 3

modulator temporarily binds to allosteric site which changes conformation of active site allow for substrate to bind

protein kinase is turned on (activated by modulator), which covalently binds to protein that changes conformation of active site and allows substrate to bind (enzymatically driven)

Question 4

what are the 3 ways in which a gated ion channel can be opened and closed

Answer 4

ligand gated (chemcially or receptor gated): ligand binds to receptor that is either part of the channel or part of an adjacent protein that allows the channel to open

voltage gated: at rest, inside of cell is negative and outside of cell is positive; when voltage across membrane changes, gate is opened (or closed)

mechanically gated: when membrane is physically distorted, gate opens and allows ions to pass

Question 5

peptide/protein hormones are ____ soluble

steroid hormones are ____ soluble

aldosterone and cortisol are examples of ____ hormones

Answer 5

water

lipid

steroid

Question 6

describe how hormones activate genes

Answer 6

steroid hormones diffuse through plasma membrane → and bind to intracellular receptor (receptor can also be present in nucleus) → hormone receptor complex translocates into nucleus and acts as a transcription factor that impacts gene transcription → gene is transcribed as mRNA → mRNA leaves nucleus and is translated as protein on a ribosome

Question 7

describe how hormones open/close ion channels

Answer 7

hormone binds to receptor → ion channels is opened → ions can flow

Question 8

describe how hormones influence target cells by binding to GPCRs

Answer 8

hormone binds to GPCR → binding allows intracellular portion of GPCR to interact with intracellular G-protein → alpha subunit dissociates and interacts with adenylyl cyclase → changes ATP to cAMP → cAMP activates a cAMP-dependent protein kinase → protein kinase phosphorylates a protein that is now activated that leads to cell’s response to hormone

Question 9

a cell’s ultimate response to a hormone include

Answer 9

change in contraction

change in secretion

change in water or solute movement (transport) across plasma membrnae

change in synthesis or breakdown of specific substances

Question 10

what are the 3 types of inputs to an endocrine cell that can influence its secretory rate

Answer 10

hormone

neurotransmitter released by neuron

ion or organic nutrient

Question 11

anytime the secretion of a homrones is controlled by the plasma concentration of an ion or nutrient, a major function of that hormone is

Answer 11

regulate the plasma level of that very same ion or nutrient

Question 12

describe how one hormone can regulate the rate of secretion of a differnet hormone

Answer 12

hypothalamus → H1 → anterior pituitary → H2 (directly to effect cell or interact with peripheral endocrine gland) → H3 → effector cells

Question 13

what 2 endocrine glands release at least 5 hormones that function to control the secretion rate of some other endocrine gland

Answer 13

hypothalamus and anterior pituitary

Question 14

describe the four general scenarios in which input from (transmitters released by) the nervous system can regulate the rate of secretion of a hormone

Answer 14

1. neuron from hypothalamus (called a neuroendocrine cell) is controlled by another neuron that secretes hormone onto the hypothalamic neuron telling it to secrete hormone
   
   1. releasing hormone
2. neuron from hypothalamus (called a neuroendocrine cell) is controlled by another neuron that secretes hormone onto the hypothalamic neuron (this neuron is not completely contained in the hypothalamus as the axon grows down into the posterior pituitary) telling it to secrete hormone
   
   1. vasopressin (ADH) and oxytocin
3. autonomic preganglionic neuron synapses into the adrenal medulla (which is a basically a postganglionic nueron cell body that never developed axons) which tells the adrenal medulla to secrete its hormone into the blood
   
   1. epinephrine
4. autonomic preganglionic neuron synapses with postganglionic neuron in a peripheral endocrine cell (such as in the pancreas) that tells that gland to secrete hormone
   
   1. glucagon

Question 15

1. what are the 2 main subdivisions of the central nervous system
2. what are the 2 main subdivisions of the peripheral nervous system
3. what are the 2 main subdivisions of the efferent (motor division) of the PNS
4. what are the 2 main subdivisions of the autonomic nervous system?
5. which subdivision of the autonomic nervous system prepares the body for intense phsyical activity such as fighting or fleeing

Answer 15

1. brain and spinal cord
2. sensory and motor (afferent and efferent)
3. somatic and autonomic
4. sympathetic and parasympathetic
5. sympathetic

Question 16

for the somatic nervous system, what type of effector cells does it control?

for the somatic nervous system, what transmitter is released and is it ever inhibitory?

for the autonomic nervous system, what type of effector cells does it control?

Answer 16

skeletal muscle

acetylcholine, it is always excitatory

smooth muscle, cardiac muscle, and glands

Question 17

in the autonomic nervous system, the first neurotransmitter released from the first neuron in the 2 neuron chain is ____ and it is always ____

Answer 17

acetylcholine

stimulatory

Question 18

in the sympathetic nervous system, the second neuron (in the 2 neuron chain) always releases ____ with the adrenal medulla also releasing ____ and these neurotransmistters can be ____ and ____

in the parasympathetic nervous system, the second neuron (in the 2 neuron chain) always releases ____ and these neurotransmitters can be ____ and ____

Answer 18

norepinephrine

epinephrine

stimulatory or inhibitory

acetylcholine

stimulatory or inhibitory

Question 19

what is a membrane potential

what is the resting membrane potential

in a resting neuron, is the neuron membrane more permeable to sodium or potassium

Answer 19

voltage across a membrane

voltage across a neuron at rest

potassium

Question 20

what are the 2 forces that can act on an ion to produce its net movement from point A to point B

Answer 20

electrical force and concentration gradient

Question 21

describe how potassium movements are the chief factor resulting in the production of the resting membrane potential

Answer 21

neuron membrane is permable to potassium and only slightly permable to sodium (assume not permable at all) → potassium slowly leaks of the neuron making the outside more positive and inside more negative → negative inside now attracts positively charged potassium back into the cell (now have an electrical charge pulling potassium back into the cell from negative inside, in addition to potassium concentration gradient still pushing potassium outside which is the stronger force) → as this continues, eventually the negativity inside become so large that the electrical force pulling potassium inside is equal to the concentration gradient pushing potassium outside → net potassium movements stop → resting potential (-94mV is reached)

Question 22

what are the 2 other factors that play a role in the resting membrane of a neuron

Answer 22

Na/K pump → move 3 Na out for every 2 K in, which results in more positivity outside → making the inside more negative

a little Na also leaks back into the cell (which contributes a very little amount of positivity inside the cell)

Question 23

graded potential and action potentials:

1. graded potential are ____ and action potentials are ____
2. graded potentials are initiated by either some stimulus acting on a sensory ____ or by transmitter acting on a ____ - synaptic potential or ____
3. action potentials are initaited by
4. graded potentials ____ as they travel whereas action potentials remain the same ____ as they travel
5. graded potentials can be ____ whereas action potentials are never

Answer 23

1. smaller, larger
2. receptor, post - , spontaneously
3. depolarizing graded potentials that reach threshold
4. die-out, size
5. hyperpolarizations

Question 24

graded potentials and action potentials:

• functions of graded potentials
• functions of action potentials

Answer 24

• to make a neuron more or less likely to make an action potential
• to cause transmitter release

Question 25

describe the 3 main types of graded potentials

Answer 25

pacemaker potentials: produced spontaneously (by ion leakage)

receptor potentials: caused by sensory stimulus acting on a sensory neuron

postsynpatic potentials: caused by transmitter acting on a postsynpatic neuron

Question 26

____ moving into the cell is resonsible for the rising phase of an action potential

____ moving out of the cell is responsible for the falling phase of an action potential

the ion channels involved are always ____ gated

Answer 26

Na

K

voltage

Question 27

what is meant by action potentail threshold

Answer 27

amount of depolarization that a graded potential has to produce so that the voltage gated channels will open up and result in an action potential

Question 28

describe the relationship between the lungs, pleural cavity, and thoracic cavity

Answer 28

fist and baloon analogy

lung is the fist with baloon (pleural cavity) all around the lung

portion of pleural membrane attached to lung → visceral pleura

portion of pleural membrane attached to thoracic cavity → parietal pleura

pleural cavity has its own fluid and pressure

Question 29

interpleural presure is always slightly ____ than atmospheric pressure

describe the mechanics of inspiration

Answer 29

less (negative pressure, but doesn’t mean less than zero)

inspiration: pressure in lungs (interalveolar) is same as atmostpheric between breaths (no air flow) → when you begin to inspire, the size of the pleural cavity increases, which leads to a decreased pressure in the pleural cavity → interalveolar pressure doesn’t change (so it is now greater than interpleural pressure) → now lungs expand which decreases interalveolar pressure → now pressure in lungs is less than atmospheric pressure→ air flows into lungs

Question 30

what is lung compliance

how does surface tension and surfactant play a role in lung compliance

Answer 30

lung stretchability

surface tension develops anywhere that air and water meet → wall of alveolus is lined with water so alveolus tries to collapse → this makes lungs hard to expand

walls of alveolus secrete detergent-like substance surfactant → this reduces surface tension → which INCREASES lung compliance

Question 31

what does percent hemoglobin saturation mean

what does partial pressure of oxygen in plasma mean

hows does partial pressure of oxygen in plasma influence percent hemoglobin

Answer 31

each hemoglobin moleulce binds 4 oxygens, percent hemoglobin saturation tells us in a group of hemoglobin molecules, how many out of 1 hundred are binding all 4 of their oxygens

how much (free) oxygen (not bound to Hb) is dissolved in plasma

PO2 in blood largely determines percent Hb saturation (when PO2 is high - roughly 100 in systemic arterial blood - the percent Hb saturation is high - about 97%)

Question 32

the plateau on the right side of the Oxygen-Hb Saturation curve acts as a

Answer 32

safety factor (can have a dramatic drop in PO2 without a big drop in percent Hb saturation - high altitudes)

Question 33

what are some factors that can shfit the oxygen-Hb dissociation curve down/right

Answer 33

increased hydrogen ions

increased CO2

increased temperature

increased BPG

Question 34

what is the benefit of the fact that certain factors can shift the oxygen-Hb dissociation curve

Answer 34

when a tissue become active (e.g. active muscles) there is increased production of CO2 which leads to increased Hydrogen ions and tissue gets warmer. this is beneficial because as blood flows through these tissues, Hb gives up oxygen more readily than usual, allowing active tissues to recieve more oxygen

these are local effects (blood still picks up as much oxygen as usual as it flows through the lungs)

Question 35

why does adding CO2 to a watery solution cause the pH to fall

Answer 35

CO₂ + H₂O ⇔ H₂CO₃ ⇔ HCO₃^- + H⁺

more CO₂ leads to more H⁺ which causes the pH to fall (become more acidic)

Question 36

is the ECF concentration of oxygen or the ECF concentration of CO₂/ECF pH the more important stimulus that controls the rate and depth of breathing

Answer 36

ECF concentration of CO₂/ECF pH

Question 37

describe the heart chambers and blood vessels, in order, through which blood passes in the pulmonary circulation.

decribe the heart chambers and blood vessels, in order, through which blood passes in the systemic circulation

Answer 37

right side of heart to lungs and back to left side of heart: blood enters right side of heart through superior/inferior vena cava → right atrium → right AV value (tricuspid) → right ventricle → pulmonary trunk → 2 pulmonary arteries → picks up oxygen in lungs → pulmonary veins → left atrium

left side of heart to system and back to right side of heart: blood enters left atrium from pulmonary veins → left AV valve (bicuspid) → left ventricle → aorta → systemic arteries → capillary beds → gives off oxygen to tissues → systemic veins → inferior and superior vena cava → right atrium

Question 38

describe the sequence in which electrical excitation travels over the heart, beginning at the SA node

Answer 38

SA node spontaneously produces action potential → spread via gap junctions to muscle fibers in both atria → one pathway through atria leads to AV node → excitation through AV node happens slowly → AV bundle (bundle is His) → right and left bundle branches → purkinje fibers → ordinary muscle fibers of ventricles that excite other muscles via gap junctions leading to near simultaneous contraction of both ventricle

Question 39

the concentration of what ion must increase inside a cardiac muscle cell for the cell to contract

Answer 39

calcium

Question 40

systole =

diastole =

Answer 40

contraction

relaxtion

Question 41

ventricular systole is divided into 2 parts:

ventricular diastole is divided into 2 parts:

Answer 41

1 short- isovolumetric contraction and 1 long-ventricular ejection

1 short- isovolmetric relaxation and 1 long- ventricular filling

Question 42

describe the mechanical events of the cardiac cycle

Answer 42

• second stage of diastole: ventricular filling → AV valve is open (because pressure in atria is greater than ventricle and semilunar valve is closed (because pressure in aorta leaving ventricle is greater than ventricular)
• near the very end of diastole: atria is contracting → ventricle are getting ready to contract
• first stage of systole: isovolumetric ventricular contraction → AV valve is closed (because ventricle begins to contract) and semilunar valve is closed (because although ventricular pressure is rising, its not yet greater than aortic pressure)
• second stage of systole: ventricular ejection → semilunar valve opens (becuase pressure in ventricle increased rapidly) and blood flows through semilunar valve
• first stage of diastole: isovolumetric ventricular relaxation → both AV and semilunar valve is closed (ventricular pressure is beginning to fall becuase it is relaxing and pressure in aorta leaving the ventricle is now greater because of all the blood that has just been pumped into the aorta) (ventricular pressure is still a little higher than atrial pressure so the AV valve remains closed

Question 43

1. what 2 factors directly determine mean systemic arterial pressure
2. what 2 factors directly determine cardiac output
3. what factors directly influence heart rate
4. what factors directly influence stroke volume

Answer 43

1. cardiac output and total peripheral resistance
2. stroke volume and heart rate
3. activity of parasympathetic nerves to heart, plasma epinephrine, and activity of sympathetic nerves to heart
4. end-diastolic ventricular volume, plasma epinephrine and activity of sympathetic nerves to heart

Question 44

1. what 2 factors directly determine total peripheral resistance
2. what factors directly influence arteriolar radius
3. what factor directly influences blood viscosity

Answer 44

1. arteriolar radius and blood viscosity
2. sympathetic vasoconstrictor Nn; plasma vasopressin, plasma angiotensin II, plasma epinephrine; local controls (O2, K, CO2, H,); plasma atrial natruretic peptide and epinephrine; nitric oxide
3. hematrocrit

Question 45

what is the Frank-Starling law of the heart

Answer 45

if ventricle fills up with more blood than usual, that streches the walls, stretched cardiac muscle contracts stronger, which increases stroke volume

an increase in end-diastolic volume increases stroke volume → increases cardiac output → increases blood pressure

Question 46

what factors can influence venous pressure (and thus the rate of venous return and the degree of ventricular filling before contraction)

Answer 46

inspiration movements

skeletal muscle pump

blood volume

Question 47

what are the receptors, integration center, motor pathways, and effectors in the control system known as the baroreceptor relex (which control arterial blood pressure from minute to minute)

Answer 47

• arterial baroreceptors: stretch detectors in walls of arteries
• sensory pathway: afferent neurons
• integration center: cardiovascular center in medulla
• efferent pathway: efferent neurons via sympathetic and parasympethic systems
• effectors
  
  • sympathetic
    
    • to arterioles → total peripheral resistance
    • veins → stroke volume → cardiac output
    • heart → stroke volume → cardiac output
  • parasympathetic
    
    • heart → heart rate → cardiac output

Question 48

a ____ lens is needed for viewing near objects

a ____ lens is needed for viewing distant objects

Answer 48

strong (rounded)

weak (flattened)

Question 49

1. how is eye able to focus on nearby objects
2. how is eye able to focus on distant objects
3. this change if focusing is called

Answer 49

1. ciliary muscle contracts → contraction moves ciliary body towards lens → decreases tension in suspensory ligaments→ decreases pull on lens exerted by suspensory ligaments → lens assumes its normal spherical shape → clear image of nearby object is formed
2. ciliary muscle relaxes → relaxation moves ciliary body away from lens → increases tension in suspensory ligaments → increases pull on lens exerted by suspensory ligaments → lens flattens → clear image of distant object if formed
3. accommdation

Question 50

describe how at the neuromuscular junction in skeletal muscle, does an action potential in a motor neuron lead to the production of an action potential in the sarcolemma and then in a t-tubule

Answer 50

• events in the neuron
  
  • action potential arrives at axon terminal
  • calcium enters terminal through calcium channels
  • acetylcholine is released from terminal
• events in the synaptic cleft
  
  • acetylcholine diffuses across synaptic cleft, binds to receptors on sarcolemma, and is broken down by acetylcholinesterase
• events in the muscle fiber
  
  • cation channels open and cations enters (mostly Na)
  • fiber produces end plate potential because Na adds positive charge to fiber
  • fibe produces action potential if end plate potential reaches threshold
  • action potential travels into interior of the fiber along transverse tubules where it excites sarcoplasmic reticulum that contains calcium ions
  • calcium ions released into sarcoplasm (cytoplasm of cell) that causes contraction

Question 51

describe the sliding filament theory of muscle contraction, including the role of calcium and the sarcoplasmic reticulum

Answer 51

• ATP attaching to myosin head causes dissociation of myosin head to actin
• myosin head is an ATPase that hydrolyzes ATP into ADP and P_i
• when ATP spits, this causes cocking of myosin head (ADP and P_i remain attached to myosin head
• when calcium is present it binds to troponin which pulls on tropomyosin, which exposes myosin binding sites on actin allowing mysoin head to bind
• release of P_i (that was still attached to myosin head along with ADP) causes pivoting of myosin head on actin and pulls it towrads the middle of the sarcomere

Question 52

why does a tetanically stimulated individual muscle fiber stretch to various lengths develop different levels of tension

Answer 52

• if you stretch a muscle fiber too much, to the point where actin and myosin don’t overlap, there’s no way for myosin to bind to actin and no force can be produced
• if sarcomere is shortened too much, actin filaments are overlapping each other, and that interferes with ability of some of the cross-bridges to bind
  
  • if very short, thick filament can crumple by z lines interacting with myosin heads

Question 53

in ____- unit smooth muslce, all the fibers contract together because they are electrically connected by ____ ____ and can include ____ activity

in ____- unit smooth muscle, the fibers contracts ____ of each other

Answer 53

single, gap junctions, pacemaker

multi, individually

Question 54

in smooth muscle, what calcium-binding protein roughly plays the role in contraction that troponin plays in skeletal muscle?

what other protein is activated by this calcium-binding protein when it is bound to calcium?

Answer 54

calmodulin

MLCK (myosin light chain kinase)

Question 55

describe the micoranatomy of a nephron

Answer 55

consists of renal corpuscle and renal tubule (surrounded by peritubular capillaries)

renal corpuscle consists of glomerular capillaries and Bowman’s capsule (containing Bowman’s space)

renal tubule contains: proximal tubule, loop of Henle, distal tubule, and collecting duct (peritubular capillaries surrounds these structures)

Question 56

describe blood flow to and through the kidneys

Answer 56

blood approaches kidney via afferent arteriole, enters Bowman’s capsule (some filtration takes place here) and exists Bowman’s capsule via efferent arteriole which then travels around nephron via peritubular capillaries

Question 57

describe glomerular filtration

describe tubular secretion

describe tubular reabsorption

Answer 57

movement out of glomerular capillaries into Bowman’s space

movement from peritubular capillaries into tubule (blood → filtrate)

movement from tubule into peritubular capillaries (filtrate → blood)

Question 58

what is glomerular filtration rate

what is filtered load

Answer 58

the rate at which fluid moves out of glomerular capillaries and into all the body’s combinded Bowman’s spaces (mL/min)

filtered load of a substance is the amount of that substance that’s filtered per unit time (g/min) (filtration rate of a specific substance, for instance Na+)

Question 59

why is sodium reabsorption necessary before water can be reabsorbed?

why is water rebsorption necessary before urea can be reabsorbed?

Answer 59

• concentration of substances in intial filtrate (Bowman’s space) is equal to the plasma concentration because this filtration is passive
• since water and urea are reabsorped passively and because the concentration is the same in blood and filtrate, they are dependent upon concentration differences to be reabsorbed
• once sodium is reabsorbed activly, the decreases the water concentration in the peritubular capillaries and allows water to move down its concentration gradient
• the reabsorption of water changes the concentration of urea, allow urea to move down its concentration to be reabsorbed into peritubular capillaries

Question 60

what is the osmolarity of the renal medullary interstitial fluid relative to the osmolarity of the rest of the body’s fluids?

Answer 60

body’s fluid 300 mosm/L compared to much greater osmolarity as one moves deeper into medulla (up to 1200-1400 mosm/L

Question 61

ADH (vasopressin) is secreted by ____ and results in increased reabsorption of ____ in renal distal tubule and ____ duct

Answer 61

posterior pituitary (produced by hypothalamus)

water

collecting

Question 62

describe the RAAS

Answer 62

• liver → angiotensinogen
• kidneys → renin → converts angtiotensinogen into angtiotensin I
• lungs → converting enzyme → converts angiotensin I into angiotensin II → adrenal cortices → aldosterone → kidneys → increased tubular reabsorption of Na⁺ in late distal tubule and collecting duct

Question 63

describe the steps of the reflex that regulate the rate at which the kidney reabsorbs sodium

Answer 63

the receptors are: arterial baroreceptors and medulla oblongata, juxtaglomerular cells of the kidneys, and cells of the macula densa

the receptors recognize low plasma volume, low blood pressure, and low sodium → renal juxtaglomerular cells to secrete renin → increased plasma renin → increased plasma angiotensin II → adrenal cortex: secrete aldosterone → increased plasma aldosterone → collecting ducts: increased Na+ and (due to osmotic considerations) water reabsorption → decreased Na+ and water excretion

Question 64

describe the steps of the reflex that regulates the rate at which the kidney reabsorbs water

Answer 64

ingestion of excess water → decreased ECF osmolarity (increased water concentration in ECF) → inhibition of (decreased firing by) hypothalamic osmoreceptors → decreased ADH secretion from posterior pituitary → decreased plasma ADH → decreased permeability of renal collecting ducts to water → decreased water reabsorption → increased water excretion

Question 65

aldosterone ____ potassium levels in the body

Answer 65

decreases

Question 66

what are the 3 main effects of parathyroid hormone in calcium homeostasis

Answer 66

increases bone resorption → releasing Ca²⁺ into ECF

increases rate of Ca²⁺ reabsorption in kidneys

activates in enzyme in the kidneys that catalyzes the conversion within the kidney, of inactive vitamin D into active vitamin D

Question 67

what is the main effect of active vitamin D3 in calcium homeostasis

Answer 67

increases intestinal absorption of calcium

Question 68

digestion:

absorption:

secretion:

motility:

Answer 68

breaking down of food

movement of digested molecules from GI lumen into ECF

moving molecules into the lumen of the GI tract (e.g. acid, bile)

churning and peristaltic movments that mix and propel GI luminal contents

Question 69

in regards to the digestive system, the body tries to maximize ____ and ____

Answer 69

digestion and absorption

Question 70

in regards to the digestive system, the body regulates ____ and ____

Answer 70

secretion and motility

Question 71

by regulating secretion and motility, the body is able to maximize the chance for ____ and ____

Answer 71

digestion and absorption

Question 72

what dietary components are digested in the small intestine:

the absorbable products of carbs are:

the absorbable products of lipids are:

the absorbable products of proteins are:

Answer 72

everything

monosaccharides (glucose)

free fatty acids and glycerol

amino acids

Question 73

the products of carb, lipid, and protien digestion are absorbed

Answer 73

in the small intestine

Question 74

stomach produce the hormone ____

what are the stomach exocrine secretions:

Answer 74

gastrin

hydrochloric acid, pepsinogen, mucus, intrinsic factor

Question 75

what are the 4 tunics of the GI tract wall

Answer 75

mucosa - consists of outer layer of cells (mucosal epithelium) where molecules are absorbed and secretion of hormones and contain enzymes

submucosa - contains submucosal plexus

muscularis externa - contains 2 layers of muscle and myenteric plexus

serosa or adventitia - single layer of serous secreting cells

Question 76

hepatic portal circulation:

• veins draining the SI (and LI, pancreas, and part of the stomach) do not empty directly into the inferior vena cava, instead these veins merge to form the ____ ____ ____ , which travels to and gives rise to a second capillary network within the liver
• products of digestion absorbed into the SI blood (but not the lacteal) are processed ( ____ , ____ , ____ , etc.) by liver enzymes before entering the general ____

Answer 76

hepatic portal vein

metabolized, detoxified, stored

circulation

Question 77

amylase:

secreted from:

performs actions in:

digests:

Answer 77

salivary glands and pancreas

mouth

carbs

Question 78

lactase:

secreted from:

performs actions in:

digests:

Answer 78

luminal membranes (brush border)

Small intestine

sugar (lactose) carb

Question 79

lipase:

secreted from:

performs actions in:

digests:

Answer 79

pancreas

small intesteine

lipids

Question 80

pepsin:

secreted from:

performs actions in:

digests:

Answer 80

stomach

stomach

proteins

Question 81

trypsin:

secreted from:

performs actions in:

digests:

Answer 81

pancreas

small intestine

proteins

Question 82

aminopeptidase:

secreted from:

performs actions in:

digests:

Answer 82

pancreas

small intestine

protein fragments

Question 83

what is the diffferent about the digestion and absorption of lipids

Answer 83

they are not water soluble, have to make them water soluble by forming micelles that are surrounded by molecules that are partly water soluble and partly lipid soluble

this makes the outside water soluble (and makes the entire molecule look water soluble) and contents (fatty acids and monoglyercides) are absorbed into GI cells, which then are packaged into chylomicrons which enter lacteal (not blood capillary)

Question 84

what is different about the reflexes that control the digestive system relative to the control reflexes for other organ systems?

Answer 84

reflexes control secretion and motility in order to maximize opportunitiy for digestion and absorption. THE STIMULUS AND RESPONSE FOR THE REFLEXES ARE NOT IN THE ECF BUT IN THE GI LUMEN

most receptors are located in the wall of the GI tract itself

receptors respond to the distenstion of the lumen wall, the osmolarity or acidity of the chyme, or the products of digestion

reflexes are triggered by the activation of these mechano-, osmo-, and chemoreceptors, and influence the muscles of the GI tract wall and the exocrine glands that secrete into its lumen

Question 85

how is a GI receptor and GI effector (in a reflex) connected neurally (3 ways)

Answer 85

1. receptors use just the enteric nervous system
2. neural signals are routed through CNS
3. some reflexes (rather than starting from stimulus in the GI tract lumen) start from CNS (sight, smell of food; emotional states and hunger)

Question 86

describe how a GI receptor and a GI effector can be mediated hormonally

Answer 86

stimulus is in lumen of GI tract → bumps into mucosal epithelial cell that is a receptor for the reflex that also happens to be an endocrine cell → endocrine cell secretes hormones into blood → blood carries hormones to 1. smooth muscle or GI tract wall, 2. another endocrine cell, or 3. exocrine gland

Question 87

acetylcholine, gastrin, and histamine, all function to increase parietal cell’s secretion of ____

Answer 87

acid