smooth muscle

Question 1

what is smooth muscle?

Answer 1

• type of muscle that is found in organs that need to operate on their own

Question 2

what do smooth muscle cells form?

Answer 2

• form layers and line cavities (inner part) of hollow organs so they have the ability to change shape of organs to help processes e.g. swallowing

Question 3

what are smooth muscle contractions controlled by?

Answer 3

• autonomic nervous system

Question 4

how can cells be connected?

Answer 4

• both electrically and mechanically

Question 5

what contraction does smooth muscle allow?

Answer 5

• sustains contractions over a long period of time without fatigue when muscle stimulated consistently

Question 6

do smooth muscles have striations?

Answer 6

• no as have no sarcomere arrangement

Question 7

how are actin and myosin filaments arranged? what does this allow?

Answer 7

• arranged in form of lattice around the cell
• allows shape to change

Question 8

what are the specialised areas called where actin filaments attach to cells?

Answer 8

• dense bodies in cytoplasm
• anchors proteins

Question 9

where does myosin sit?

Answer 9

• floats in-between thin filaments (actin)

Question 10

what are dense bands at the end of fibre movement of one affects other?

Answer 10

• smooth muscle cells are mechanically connected to neighbouring cells

Question 11

how is neurotransmitter released?

Answer 11

• no muscular junctions so NTs released non- specifically from varicosities that line the nerve
• NTs released and find specific receptors in order to excite cell

Question 12

what is a single unit? give examples

Answer 12

• cells electrically coupled by a gap junction so function as a unit
  e.g. blood vessels, intestines

Question 13

what is a multi unit? when are these found? give examples

Answer 13

• not electrically coupled or very few cells so act independently of each other
• found where precision of movement is important e.g. lung, airways

Question 14

is there more myosin or more actin?

Answer 14

• more actin and less myosin

Question 15

what is the benefit of no Z lines?

Answer 15

• myosin and actin can slide past each other without encountering the end of sarcomere

Question 16

what does the long distance between filaments mean?

Answer 16

• force can be regulated when shortening

Question 17

does it follow the all or none law?

Answer 17

• No so can be graded

Question 18

what is pacemaker potential similar to?

Answer 18

• sinoatrial node, activation of smooth muscle that relies on rhythmic activity is achieved by spontaneously occurring APs due to unstable resting membrane potential

Question 19

what are slow waves?

Answer 19

• graded potentials that are wavering below threshold as muscle is influenced by a combo of excitatory and inhibitory inputs

Question 20

what state is the muscle kept in? until when?

Answer 20

-readiness
- until exciting stimulus pushes the threshold line so action potential fired

Question 21

what must the first action potential do before the second action potential comes?

Answer 21

• first action potential must finish

Question 22

how are calcium ions sourced?

Answer 22

• intracellular (sarcoplasmic reticulum) or extracellular

Question 23

how does calcium act on thick myosin filaments?

Answer 23

• enters the cell to activate protein calld calmoulin, which further activates enzyme myosin kinase

Question 24

what does the enzyme use ?

Answer 24

• uses ATP to phosphorylate myosin chains in the head

Question 25

what happens if calcium is maintained?

Answer 25

• head of myosin is energised and can keep recycling and maintaining conc.

Question 26

how does relaxation occur?

Answer 26

• by myosin light chain phosphate

Question 27

what happens if phosphatase is overwhelmed?

Answer 27

• if overwhelmed by kinase then the muscle contracts