Physiology II

Question 1

how does AP in motor neuron lead to AP in sacolemma then t-tubule?

Answer 1

AP opens voltage gated Ca channels (depolarization) –> Ca stimulates vesicles of neuron –> aCh released to cleft –> binds with receptor in sarcolemma –> opens cation channel in muscle (mainly Na) –> cell now more positive (end plate potential) –> GP produced traveling along sarcolemma –> T-tubule to anterior –> SR –> sarcoplasm

Question 2

sliding filament theory (5 steps)

Answer 2

1. ADP released from myosin head, making room for ATP to bind.
2. ATP binds myosin had causing actin myosin to dissociate
3. ATP hydrolized to ADP + Pi causing conformational change in myosin
4. If Ca present –> Ca binds troponin C –> troponin T “tugs” on tropomyosin and moves from active site on actin. Now myosin binds actin.
5. Pi released from myosin head, Z disc attached to actin also moves

Question 3

why does a tetanically stimulated individual muscle fiber stretched to various lengths develops different levels of tension (3)

Answer 3

• sarcomere stretched. no actin/myosin overlap
• 2 actins overlap interfering with cross bridge formation so decrease tension
• short sarcomere, Z lines colide with thick (myosin) filaments causing them to crumple so decrease tension

Question 4

single unit smooth m

Answer 4

entire muscle groups respond to stimulation as single unit

connected via gap junctions

Question 5

multiunit smooth m

Answer 5

contain few or no gap junctions

each cell responds independently

innervated by ANS

contraction depends on: # activated fiber + nerve frequency stimulation

Question 6

in smooth muscle, what does Ca and troponin play

Answer 6

no troponin in smooth muscle so tropomyosin never blocks actins binding sites for myosin

cross bridge required via Ca activation by myosin light chain kinase

Question 7

smooth m contraction mechanism

Answer 7

increase signal –> in Ca in cytoplasm –> Ca binds calmodulin (reversibly) –> complex binds/activates MLCK –> ATP causes phosphorylation of myosin head –> head binds actin –> contraction

Question 8

nephron

Answer 8

functional unit of kidney

Question 9

renal corpuscle

Answer 9

filtering component

contains: glomerulus, bowmans capsule, bowmans space

Question 10

renal tubule

Answer 10

extends out from corpuscle and surround by peritubular capillaries

prox tubule, LOH, distal tubule, CD

Question 11

tubular resorption

Answer 11

excreted < filtered

tubules –> blood

Question 12

tubular secretion

Answer 12

excreted > filtered

blood –> tubules

Question 13

glomerular filtration

Answer 13

low molecular weight substances in glomerular capillary plasm filtered across thin membrane of capillaries and of BC –> BS

ex. water, glucose, urea, ions

substance –> endothelium –> basement membrane –> btwn foot processes –> BS

Question 14

GFR

Answer 14

volume of fluid filtered into combined Bowmans space per unit time

(volume/time)

Question 15

filtered load

Answer 15

total amount of given substance filtered per unit time

GFR x [substance in plasma]

Question 16

blood pathway in kidney

Answer 16

afferent arteriole –> glomerular capillaries –> efferent arteriole –> peritubular capillaries

Question 17

filtrate pathway in kidney

Answer 17

bowmans capsule –> PCT –> LOH –> DCT –> CD

Question 18

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

Answer 18

cortex and the body: 300

the deeper you go, the more concentrated it is

max renal medulla: 1400

**high concentration is good because it allows drawing of water**

Question 19

what these release and what it does

liver –>

kidneys –>

lungs –>

adrenal cortex –>

kidneys –>

Answer 19

liver release angiotensinogen –> kidneys release renin converts angiotensinogen to angiotensin 1 –> lungs release coverting enzyme converts angiotensin 1 to angiotensin 2 –> angiotensin 2 to adrenal cortex –> adrenal cortex release aldosterone to blood –> aldosterone acts on kidneys to increase tubule Na reabsorption

Question 20

aldosterone vs ADH

Answer 20

ADH –> increases water reabsorption/permeability in distal tubule and CD to water

aldosterone –> increases Na resabsorption in distal tubule and CD

**without ADH, not water permeable and no water reabsorption**

Question 21

reflexes controlling body sodium (3)

Answer 21

stimulus: low plasma volume (due to low body Na)

via arterial baroreceptors and medulla oblongata (increase symp activity to kidney –> increase renin)

via direct effect on JG cells (increase renin)

via paracrines released from macula densa (increase renin)

Question 22

does aldosterone increase or decrease potassium

Answer 22

increase potassium

Question 23

describe 3 main effects of PTH and effect of active vitamin D3

Answer 23

PTH: increase calcium by…

1. desolve bone matrix
2. release Ca to blood
3. activate enzymes to inactive –> active vitamin D

Vitamin D: increase rate of Ca from diet (intestinal absorption)