Lecture 26 Unit 4

Question 1

what does smooth muscle control

Answer 1

luminal pressure and tension

Question 2

where is smooth muscle tissue present

Answer 2

in sheets, bundles, or sheaths around tissues

Question 3

what body systems in SM tissue present in

Answer 3

• cardiovascular
• respiratory
• digestive
• urinary
• reproductive system

Question 4

what system controls smooth muscle

Answer 4

ANS so its involuntary

Question 5

what are the transmitters in smooth muscle

Answer 5

ACh and NE

Question 6

what is the membrane potential in SM

Answer 6

-50 to -60 mV

Question 7

what are the smooth muscle cell types

Answer 7

single/unitary and multi-unit

Question 8

where are unitary SM cells located

Answer 8

walls go digestive tract, gall bladder, urinary bladder

Question 9

do unitary SM cells have direct contact with motor neurons

Answer 9

it may not

Question 10

what does it mean that unitary SM cells are auto rhythmic?

Answer 10

adjacent cells connect via gap junctions which transmit APS from one fiber to another

Question 11

how is force transmitted in SM cells

Answer 11

cell membranes adhere to one another

Question 12

how do you describe unitary SM cell contractions

Answer 12

slow synchronized “graded” contractions

Question 13

how does an entire sheet of muscle contract

Answer 13

as a functional syncytium

Question 14

where does SM release neurotransmitters to

Answer 14

diffuse junctions in the general area of the SM fiber

Question 15

describe sarcoplasmic reticulum in SM cells

Answer 15

it is poorly developed relative to skeletal muscle

Question 16

what do thick filaments of SM have

Answer 16

actin gripping heads

Question 17

how are thick and thin filaments arranged in SM

Answer 17

diagonally, so when cell contracts it results in a twisting motion

Question 18

what are the special features of SM

Answer 18

• capable of sustained contraction without fatigue and at very little energy cost
• maintains a low level of tension or tone even in the absence of APs
• stress-relaxation response

Question 19

what is the stress relaxation response

Answer 19

stretch causes initial increase in tension > tension decreases within 1-2 minutes > allows SM to change length but maintain ability to contract

Question 20

what is the length-tension relationship in SM

Answer 20

• smooth muscles operate over a wider range of resting lengths
• generally broader length-tension relationship in smooth muscle compared to skeletal muscle

Question 21

what does stomach filling trigger

Answer 21

secretions and motiltiy

Question 22

what is happening as the stomach empties

Answer 22

small squirts of chyme leave through the pyloric sphincter

Question 23

what is the function of parietal cells

Answer 23

HCl secretion

Question 24

what do gentle mixing waves in the stomach do

Answer 24

mix the bolus of food with gastric juice and turn it into chyme

Question 25

what do more vigorous waves in the stomach do

Answer 25

move chyme along

Question 26

what do intense waves near the pylorus do

Answer 26

lead to the opening of the pyloric sphincter quirting 1-2 teaspoons into the duodenum with each wave

Question 27

where does protein digestion begin

Answer 27

in the stomach

Question 28

what occurs in protein digestion in the stomach

Answer 28

- HCl denatures protein molecules | - HCl activates pepsinogen into pepsin

Question 29

what does pepsin do

Answer 29

breaks peptide bonds between certain amino acids

Question 30

what happens in fat digestion in the stomach

Answer 30

gastric lipase splits the triglycerides in milk fat

Question 31

what does HCl do

Answer 31

kill microbes in food

Question 32

what does the stomach absorb

Answer 32

- water - electrolytes - some drugs (aspirin) and alcohol

Question 33

how is alcohol absorbed more slowly

Answer 33

is taken with a meal

Question 34

what slows the passage of alcohol to the small intestine

Answer 34

fat content in the stomach

Question 35

what are some neural influences over stomach activity

Answer 35

- stretch receptors and chemoreceptors signal bolus entry leading to an increase in parasympathetic nerve impulses to effectors in the stomach - vigorous peristalsis and gastric gland secretions result - chyme periodically released into the duodenum until return to homeostasis

Question 36

what are some endocrine influences over stomach activity

Answer 36

-distention and presence of food in the stomach cause G cells to secrete gastrin into the bloodstream which increases gastric gland secretions and motility and causes pyloric sphincter relaxation