Unit 4 Lecture 26

Question 1

What does smooth muscle control?

Answer 1

pressure and tension within organ layers

Question 2

Where is smooth muscle present?

Answer 2

Sheets???, bundles or sheaths around tissues

Question 3

What nervous system controls smooth muscle?

Answer 3

Mostly the autonomic (involuntary) nervous system

Question 4

What are the transmitters of smooth muscle?

Answer 4

ACh and NE

Question 5

What are the 2 smooth muscle cell types based on excitation?

Answer 5

• Single/ unitary (visceral)

- multi-unit

Question 6

Where are unitary smooth muscle cells found?

Answer 6

Walls of digestive tract, gall bladder and urinary bladder

Question 7

How do adjacent unitary SM cells connect?

Answer 7

gap junctions

Question 8

What occurs in gap junctions?

Answer 8

Transmission of APs from one fiber to another

Question 9

How do unitary SM cells contract?

Answer 9

AUTORHYTHMIC and

“graded” contractions

Question 10

Define autorhythmic and graded contractions

Answer 10

Autorhythmic - contract on their own

Graded contractions - contractions vary in intensity and degree

Question 11

Define function syncytium

Answer 11

The ability to perform rapid, coordinated contractions of smooth muscle along an entire length of fibers

Question 12

What types of nerve fibers innervate onto smooth muscle?

Answer 12

Autonomic nerve fibers

Question 13

What is a major component of autonomic nerve fibers found on smooth muscle?

Answer 13

Varicosities

Question 14

What are found in viscosities of autonomic nerve fibers?

Answer 14

Mitochondria and synaptic vesicles

Question 15

What do viscosities do?

Answer 15

Release neurotransmitters into DIFFUSE JUNCTIONS in the area of the SM fiber

Question 16

What is scarce in smooth muscle vs. skeletal muscle?

Answer 16

Sarcoplasmic reticulum

Question 17

What is the importance of the sarcoplasmic reticulum?

Answer 17

It is the main intracellular calcium store in muscle and it plays regulates excitation contraction-coupling (ECC)

Question 18

What does the calcium released from the SR effect?

Answer 18

Thick and thin filaments

Question 19

What is found on thick filaments?

Answer 19

Actin-gripping myosin heads that connect to actin on thin filament to make a crossbridge

Question 20

How are thin and thick filaments arranged and how do they contract?

Answer 20

Arranged diagonally and contract w twisting motion….. like ringing out a towel

Question 21

Describe the energy used during contractions of smooth muscle

Answer 21

sustained contraction without fatigue and little energy cost

Question 22

Describe tension or TONE during contractions of smooth muscle

Answer 22

low levels of tension or tone even without action potentials

Question 23

List the steps of the stress-relaxation response

Answer 23

Stretch causes initial increase in tension -> tension decreases within 1-2 minutes -> allows SM to change length but maintain ability to contract (important for storage organs)

Question 24

What is the relationship between length and tension in smooth muscle?

Answer 24

broader length-tension relationship in smooth muscle vs. skeletal

Question 25

How does smooth muscle operate?

Answer 25

operates over a wider range of resting lengths