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Physio 202 Lecture > Lecture 26 Unit 4 > Flashcards

Lecture 26 Unit 4 Flashcards

1
Q

what does smooth muscle control

A

luminal pressure and tension

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2
Q

where is smooth muscle tissue present

A

in sheets, bundles, or sheaths around tissues

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3
Q

what body systems in SM tissue present in

A
  • cardiovascular
  • respiratory
  • digestive
  • urinary
  • reproductive system
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4
Q

what system controls smooth muscle

A

ANS so its involuntary

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5
Q

what are the transmitters in smooth muscle

A

ACh and NE

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6
Q

what is the membrane potential in SM

A

-50 to -60 mV

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7
Q

what are the smooth muscle cell types

A

single/unitary and multi-unit

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8
Q

where are unitary SM cells located

A

walls go digestive tract, gall bladder, urinary bladder

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9
Q

do unitary SM cells have direct contact with motor neurons

A

it may not

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10
Q

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

A

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

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11
Q

how is force transmitted in SM cells

A

cell membranes adhere to one another

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12
Q

how do you describe unitary SM cell contractions

A

slow synchronized “graded” contractions

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13
Q

how does an entire sheet of muscle contract

A

as a functional syncytium

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14
Q

where does SM release neurotransmitters to

A

diffuse junctions in the general area of the SM fiber

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15
Q

describe sarcoplasmic reticulum in SM cells

A

it is poorly developed relative to skeletal muscle

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16
Q

what do thick filaments of SM have

A

actin gripping heads

17
Q

how are thick and thin filaments arranged in SM

A

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

18
Q

what are the special features of SM

A
  • 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
19
Q

what is the stress relaxation response

A

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

20
Q

what is the length-tension relationship in SM

A
  • smooth muscles operate over a wider range of resting lengths
  • generally broader length-tension relationship in smooth muscle compared to skeletal muscle
21
Q

what does stomach filling trigger

A

secretions and motiltiy

22
Q

what is happening as the stomach empties

A

small squirts of chyme leave through the pyloric sphincter

23
Q

what is the function of parietal cells

A

HCl secretion

24
Q

what do gentle mixing waves in the stomach do

A

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

25
Q

what do more vigorous waves in the stomach do

A

move chyme along

26
Q

what do intense waves near the pylorus do

A

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

27
Q

where does protein digestion begin

A

in the stomach

28
Q

what occurs in protein digestion in the stomach

A
  • HCl denatures protein molecules

- HCl activates pepsinogen into pepsin

29
Q

what does pepsin do

A

breaks peptide bonds between certain amino acids

30
Q

what happens in fat digestion in the stomach

A

gastric lipase splits the triglycerides in milk fat

31
Q

what does HCl do

A

kill microbes in food

32
Q

what does the stomach absorb

A
  • water
  • electrolytes
  • some drugs (aspirin) and alcohol
33
Q

how is alcohol absorbed more slowly

A

is taken with a meal

34
Q

what slows the passage of alcohol to the small intestine

A

fat content in the stomach

35
Q

what are some neural influences over stomach activity

A
  • 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
36
Q

what are some endocrine influences over stomach activity

A

-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

Physio 202 Lecture (38 decks)

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