smooth and cardiac muscle

Question 1

what is the main function of smooth muscle?

Answer 1

mechanical control of organ systems

Question 2

describe the shape and structure of a smooth muscle fibre

Answer 2

spindle shaped

single central nucleus

Question 3

is smooth muscle voluntary or involuntary?

Answer 3

involuntary

Question 4

is smooth muscle striated or non-striated?

Answer 4

non-striated

Question 5

what is the function of cardiac muscle?

Answer 5

intrinsic myogenic activity that’s responsible for heart beat

Question 6

how are cardiac myocytes organised?

Answer 6

in a branched network that runs in different directions

Question 7

is skeletal muscle voluntary or involuntary?

Answer 7

voluntary

Question 8

what kind of movements is skeletal muscle responsible for?

Answer 8

locomotion
maintenance of posture
breathing via contraction of the diaphragm

Question 9

is skeletal muscle striated or not?

Answer 9

striated

Question 10

how many nuclei are found in skeletal muscle cells and how are they arranged?

Answer 10

multiple

peripherally-located

Question 11

what cellular junctions are found in cardiac muscle?

Answer 11

intercalated discs

gap junctions

Question 12

what cellular junctions are found in smooth muscle?

Answer 12

gap junctions

Question 13

what calcium binding mechanisms do skeletal, smooth and cardiac muscle have?

Answer 13

skeletal - troponin
cardiac - troponin
smooth - calmodulin

Question 14

what are A bands in cardiac muscle fibres?

Answer 14

thick bands

dark bands

Question 15

what are I bands in cardiac muscle fibres?

Answer 15

thin bands

light bands

Question 16

what is the sarcolemma?

Answer 16

the plasma membrane of the muscle

Question 17

what are intercalated discs?

Answer 17

sites of thickening of the sarcolemma

Question 18

what are intercalated discs made up of and what are their functions?

Answer 18

gap junctions - allow ions to pass from cell to cell so the AP can move between cells in a coordinated fashion

desmosomes - anchor ends of the cells together

Question 19

define automaticity

Answer 19

the ability to spontaneously depolarise

Question 20

define rhythmicity

Answer 20

the ability to depolarise in a regular and repetitive way

Question 21

what is an electrical syncytium?

Answer 21

where myocardium functions as a single contractile unit

Question 22

which ions form repolarising currents?

Answer 22

K+

Question 23

which ions form depolarising currents?

Answer 23

Na+ and Ca2+

Question 24

which type of cardiac cells show automaticity?

Answer 24

pacemaker cells

atrial and ventricular cells in disease

Question 25

what is the refractory period?

Answer 25

the period of time during which the ion channels are inactivated and the muscle is unresponsive

Question 26

what is the advantage of long refractory periods in ventricular cells?

Answer 26

individual contractions don't fuse together like in skeletal muscle

Question 27

explain the process of calcium signalling in cardiac muscle contraction

Answer 27

membrane depolarises sodium influx causes calcium to enter through LTCC triggers calcium release from SR via ryanodine receptor calcium associates with troponin C to initiate contraction contraction ends when calcium dissociates from troponin c and goes back to SR

Question 28

how does the sympathetic NS affect cardiac muscle?

Answer 28

increases HR and force of contraction

Question 29

what receptors does noradrenaline act on in cardiac muscle?

Answer 29

beta1 adrenoreceptors

Question 30

what receptors does acetylcholine act on?

Answer 30

M2 muscarinic receptors

Question 31

describe the structure of smooth muscle

Answer 31

loose lattice of thick and thin filaments held together by dense bodies

Question 32

what do intermediate filaments do in smooth muscle?

Answer 32

help in the transmission of force generated by contraction

Question 33

what are the 2 types of attachment in smooth muscle?

Answer 33

mechanical attachment between cells gap junction - pathway for electrical signals between cells

Question 34

gives examples of where smooth muscle is found in the body

Answer 34

``` bladder gut uterus blood vessels bronchi urethra, bladder erector pili in the skin ```

Question 35

what are the functions of smooth muscle?

Answer 35

Regulation of the diameter of blood vessels Regulating diameter of airways Propulsion of food through GI tract Contraction of the uterus delivery of baby

Question 36

what are the types of action potential that can be seen in smooth muscle action potentials?

Answer 36

simple repetitive spiking of action potential spike followed by plateau (seen in ventricular APs) spikes on top of slow waves (pacemaker cells)

Question 37

why are smooth muscle APs longer than skeletal muscle Abs?

Answer 37

Ca2+ channels open more slowly than Na+ channels

Question 38

what are varicosities?

Answer 38

structures which release neurotransmitters into the space surrounding muscles

Question 39

what are the types of smooth muscle organisation?

Answer 39

multi-unit smooth muscle | single-unit smooth muscle

Question 40

describe the innervation of cells in multiunit smooth muscle

Answer 40

each cell receives their own synaptic input little electrical coupling can contract independently of their neighbour

Question 41

give examples of where multiunit smooth muscle is found

Answer 41

iris of the eye | larger blood vessels

Question 42

describe the innervation of cells in single unit smooth muscle

Answer 42

ANS innervates one cell within a sheet/bundle gap junctions propagate APs to neighbouring cells whole sheet contracts as a single functional syncytium

Question 43

give examples of where single unit smooth muscle is found

Answer 43

walls of all visceral organs apart from the heart

Question 44

what kind of contractions are produced by visceral smooth muscles

Answer 44

slow and steady contractions to allow movement of substances through the body

Question 45

what are the two ways in which calcium can enter smooth muscle cells

Answer 45

depolarisation of the membrane opens VG calcium channels agonist induced release of calcium via IP3

Question 46

explain the process of agonist induced release of calcium in smooth muscle

Answer 46

``` agonist binds to receptor G protein complex activated binds to phospholipase C (PLC) PLC generates IP3 IP3 triggers calcium release from SR ```

Question 47

explain the process of excitation-contraction coupling in smooth muscle

Answer 47

calcium is released binds to calmodulin activates enzyme myosin light-chain kinase (MLCK) MLCK phosphorylates regulatory region on myosin light chains increases ATPase activity myosin head groups bind actin and undergo cross-bridge cycling leads to contraction

Question 48

how do thick and thin filaments work in smooth muscle cells to cause contraction?

Answer 48

thin filaments slide past thick filaments to pull on dense bodies dense bodies pull on intermediate fibres muscle fibres contract ends are pulled to the centre, causing mid-section to bulge

Question 49

what triggers smooth muscle contraction?

Answer 49

hormones neural stimulation by the ans local factors stretching the muscle (walls of visceral organs)

Question 50

what type of smooth muscle is found in blood vessels and where is it found?

Answer 50

vascular smooth muscle | under the endothelium

Question 51

what type of blood vessels have vascular smooth muscle mainly?

Answer 51

arteries

Question 52

how is smooth muscle found in airways?

Answer 52

in bands surrounding the airway