exam 1 lecture 8 Smooth muscle

Question 1

Primary pathologies of smooth muscle in veterinary medicine are very ___ and have yet to be identified

Answer 1

rare

Question 2

many diseases result in changes in smooth muscle activation or ___, resulting in pathology AND

Answer 2

relaxation

Question 3

smooth muscle can be innervated by ___

Answer 3

Additionally, neurotransmitters and endocrine and paracrine factors can both stimulate and inhibit contraction

Question 4

smooth muscle contracts quickly or slowly?

Answer 4

slowly

anatomy and chemistry of smooth muscle has eliminated speed as a characteristic of excitation-contraction coupling

Question 5

what type of muscle has an all or nothing response

Answer 5

skeletal

Question 6

where to find smooth muscle

Answer 6

Lines hollow organs

GI tract

Urinary Bladder

Endothelium

Uterus

Vas Deferens

Bronchioles ………

Question 7

smooth muscle is normally is sheet shapes, where is it in bundles?

Answer 7

eye

Question 8

smooth muscle is always covered by ___

Answer 8

protective cell layer- epithelium

Question 9

muscle cell shape

Answer 9

spindled

single cell

single nucleus

shorter and smaller than skeletal muscle

Question 10

why irregular pattern in smooth muscle?

Answer 10

generate force over huge changes in length

example: urinary bladder- works if a drop or is a liter of urine is present

Question 11

___ muscle undergoes extensive tissue damage if stretched and also doesn’t generate force if the overlap between the thick and thin filaments is damaged.

Answer 11

Skeletal

Question 12

___ help transfer force from thick and thin filaments onto the surface of smooth muscle cells

Answer 12

dense bodies

Question 13

Z lines in skeletal muscle are similar to ___ in smooth muscle

Answer 13

dense body

distribute force

Question 14

smooth muscle is stimulated to contract by affecting either calcium or ___

Answer 14

myosin light chain kinase or phosphatase

Question 15

two distinct sources of neural stimulation of smooth muscle

Answer 15

extrinsic: ANS

Intrinsic: within the organ (enteric NS)

Question 16

extrinsic innervation of smooth muscle

Answer 16

Autonomic Nervous System

Parasympathetic and Sympathetic

Organ specific (Vascular smooth muscle almost exclusively sympathetic)

Question 17

intrinsic innervation of smooth muscle

Answer 17

Neural plexuses within organs

Motor, sensory and interneurons

Allows function if CNS input lost - doesn’t need brain to tell it what to do

example: Myenteric plexus

Question 18

Generally ___ neural stimulation provides primary control of the smooth muscle and ____ input modifies activity

Answer 18

intrinsic

extrinsic

Question 19

describe multi-unit neural stimulation of smooth muscle

Answer 19

each muscle cell has its own nerve and acts independently of other smooth muscle cells

1:1 muscle to nerve

(eye muscles: iris, piloerector muscles, some vascular smooth muscle)

Question 20

describe single unit neural stimulation of smooth muscle

Answer 20

Gap junctions between smooth muscle cells exist to allow direct signaling between muscle cells

1 nerve impulse gets spread to other cells by gap junctions

(urinary bladder, GI, uterus, vascular smooth muscle)

Question 21

example for single unit neural stimulation of smooth muscle

Answer 21

urinary bladder

Gap junctions between smooth muscle cells exist to allow direct signaling between muscle cells

Question 22

example for multi-unit neural stimulation of smooth muscle

Answer 22

eye muscle

each muscle cell has its own nerve and acts independently of other smooth muscle cells

Question 23

True or false

smooth muscle have motor endplates

Answer 23

false

no motor endplates, they have synaptic troughs, the axon released neurotransmitters to many muscle cells through varicosities

Question 24

what neurotransmitter is released for parasympathetic stimulation of smooth muscle

Answer 24

acetylcholine

(rest and digest)

Question 25

what neurotransmitter is released for sympathetic stimulation of smooth muscle

Answer 25

Norepinephrine (fight or flight)

Question 26

what are some neurotransmitters released at the synaptic troughs of smooth muscle?

Answer 26

Acetylcholine (parasympathetic- rest and digest) Norepinephrine (sympathetic- fight or flight) Nitric oxide

Question 27

two types of receptors for acetylcholine

Answer 27

**muscarinic-** smooth muscle, CNS, G-protein linked (slower) **Nicotinic-** skeletal muscle, CNS, no second messenger (fast)

Question 28

which acetylcholine receptor is used in smooth muscle and why?

Answer 28

**muscarinic** CNS second messenger system- G protein linked **makes it a slower reaction**

Question 29

example of paracrine stimulation of smooth muscle

Answer 29

(particularly vascular smooth muscle) Nitric oxide Prostacyclin Adenosine Endothelin

Question 30

endocrine stimulation of smooth muscle is by \_\_\_

Answer 30

Epinephrine Angiotensin

Question 31

all smooth muscle cells have ___ cell surface receptors

Answer 31

many different ## Footnote (muscarinic, adrenergic, nitric oxide etc.) meaning that smooth muscle can respond appropriately to many different physiological stimuli, and that some conditions will result in an over-expression of the receptors.

Question 32

Some factors will cause contraction of ___ in one tissue and relaxation in another (i.e. histamine and epinephrine/norepinephrine) Balancing these effects will be critical in therapeutic use of the drugs.

Answer 32

smooth muscle

Question 33

example of a factor that causes contraction in one type of smooth muscle and relaxation in another smooth muscle

Answer 33

**histamine** contractions- bronchi dilation- blood vessels

Question 34

where does smooth muscle get calcium?

Answer 34

Sarcoplasmic reticulum extracellular calcium

Question 35

there is more calcium inside or outside the cell?

Answer 35

outside- if you open a gate calcium will flow into the cell

Question 36

two types of calcium channels

Answer 36

**ligand-gated calcium channels** **voltage-gated calcium channels** -calcium induced calcium release (no voltage gated sodium channels)

Question 37

how is myosin in smooth muscle different than smooth muscle in skeletal muscle

Answer 37

smooth muscle: 2 **regulatory myosin light chains** **these control activation**

Question 38

how do regulatory myosin light chains work in smooth muscle

Answer 38

4 calcium bind to **calmodulin** which activates **myosin light chain kinase** which phosphorylates (adds a phosphate) to the **Regulatory myosin light chain**. When this happens the **myosin heavy change** undergoes a **conformation change** and allows actin-myosin interaction

Question 39

myosin light chain kinase does what in smooth muscle?

Answer 39

**adds phosphate group**/ phosphorylates the **regulatory myosin light chain** which causes the **myosin heavy chain** to change shape and allow for actin-myosin interactions

Question 40

in smooth muscle, calcium binds to ___ to cause actin-myosin interactions

Answer 40

**calmodulin** calmodulin triggers **myosin light chain kinase** **phosphylated Regulatory myosin light chain** causes **myosin heavy chain** to change shape this allows actin-myosin interactions

Question 41

when regulatory myosin light chain is phosphorylated, the smooth muscle is \_\_\_

Answer 41

contracted

Question 42

when regulatory myosin light chain is not phosphorylated, smooth muscle is \_\_\_

Answer 42

relaxed

Question 43

what enzyme relaxes smooth muscle

Answer 43

myosin light chain **phosphatase**

Question 44

what % of myosin is working at maximum?

Answer 44

50% never fully relaxes- 5% still working

Question 45

Calcium, through Calmodulin only affects MyLC ___ activity. It does not affect MyLC \_\_\_.

Answer 45

kinase (only forward to contraction) phosphatase (relaxation)

Question 46

increased myosin light chain kinase leads to what in smooth muscle

Answer 46

more contracting from the regulated myosin light chain. balance between kinase and phosphatase= amount of force generated by the smooth muscle

Question 47

why does smooth muscle not have an all or none response

Answer 47

some always have to work or else they would just pull on the relaxed one and nothing would move example: heart and vessels, if they all relaxed- blood would pool and not move

Question 48

tonic form of myosin heavy chain encodes for a \_\_\_

Answer 48

slower, more energy efficient contraction (aorta)

Question 49

phasic form of myosin in smooth muscle produces a \_\_\_

Answer 49

faster contracting muscle (bladder)

Question 50

phasic smooth muscle is much __ than slow skeletal muscle

Answer 50

slower phasic is fast contracting smooth muscle but even so it is much slower than skeletal muscle

Question 51

the aorta has what isoform of myosin heavy chain

Answer 51

tonic slower, more energy efficient

Question 52

the bladder has what isoform of smooth muscle myosin heavy chain?

Answer 52

phasic faster contracting

Question 53

Enzymatic inhibition of ___ results in a shift towards muscle contraction, with **no change in calcium**

Answer 53

MyLC phosphatase (stop the relaxation of a smooth muscle)

Question 54

explain latch mechanism for smooth muscle

Answer 54

Actin-myosin complexes **remains attached** and **force generating** despite the loss of ATP from the myosin pocket

Question 55

explain calcium sensitization of smooth muscle

Answer 55

keep a smooth muscle contracted **without using calcium** but stopping/inhibiting the backwards reaction by myosin light chain phosphatase

Question 56

true or false. a drug will affect all smooth muscle the same way.

Answer 56

false can have different reactions/side effects in different tissues or different areas of the body.

Question 57

Feline asthma is a type I hypersensitivity reaction to an inhaled allergen, that causes the the immune system to release histamine which causes constriction of \_\_\_

Answer 57

smooth muscle: bronchus/airways can breathe in but oxygen can't transfer

Question 58

treatment of asthma

Answer 58

glucocorticoids (suppress immune system)- primary problem bronchodilators (relax smooth muscle of airways)- secondary response

Question 59

in a long term obstruction of the urinary bladder what can happen?

Answer 59

atonic(flaccid bag) bladder due to massive distension of bladder wall. damage is actually to the nerves, which do not stretch as well as the smooth muscle of the bladder wall

Question 60

treatment for urinary tract obstruction

Answer 60

bethanechol- **muscarinic agonist** with selective activity in the detrusor muscle **help bladder contract** muscarinic- type of acetylcholine receptor for smooth muscle- second messanger- g protein linked does not effect skeletal muscle

Question 61

dystocia

Answer 61

abnormal delivery of pups long delivery- uterus uses up all the extracellular calcium→ decrease in calcium influx into the muscle cell **↓ Calcium calmodulin complex→ ↓ MLC kinase activation → ↓ Myosin activation and force** **treatment:** give calcium slowly similar to milk fever

Question 62

milk fever is similar to ___ in dogs

Answer 62

dystocia

Question 63

Early in heart failure, increasing vascular resistance is a good thing, maintaining tissue perfusion. Eventually the resistance exceeds the hearts ability to adequately push blood out of the \_\_\_. Death ensues rapidly

Answer 63

ventricles

Question 64

treatment for canine heart failure

Answer 64

**nitro**prusside → decrease blood pressure, heart doesn't have to work as hard paracrine transmitter to smooth muscle- cNOS is an enzyme that causes **vasodilation** through a second messenger signaling pathway that lowers intracellular calcium

Question 65

what kind of muscle lack all-or-none response?

Answer 65

smooth allows either pharmacological increase or decrease in smooth muscle activation

Question 66

The ability to generate force over tremendous changes in fiber ___ are critical to smooth muscle function

Answer 66

length

Question 67

Tissue ___ activation or relaxation is critical to therapeutic success

Answer 67

specific have to know what drug will do to different types of smooth muscle throughout the body, can have bad side effects.