UNIT 9- SYNAPTIC TRANSMISSION + MUSCLE PHYSIOLOGY

Question 1

Stimulation of electrical synapses causes phosphorylation or dephospho rylation of ___________ to open or close channels

Answer 1

connexin proteins (form gap junctions)

Question 2

pre and post synaptic membranes are held together by…

Answer 2

Cell Adhesion Molecules (CAMs)- project from pre and post membranes into synaptic cleft where they stick together

Question 3

Number of vesicles that undergo exocytosis (fusion to membrane) depends on ___________

Answer 3

frequency of action potentials

Question 4

Why is the release of some neurotransmitters rapid?

Answer 4

because many synaptic vesicles are already docked at the presynaptic membrane before arrival of AP which triggers release of NXTs

Question 5

Arrival of AP at axon terminals open ________

Answer 5

Ca2+ channels- rapid inward diffusion of Ca+ triggers rapid fusion of synaptic vesicle with axon membrane and release NXTs

Question 6

Ca2+ release triggers activation of ___________ and ___________. Both of these proteins contribute to synaptic vesicle exocytosis

Answer 6

calmodulin (activates protein kinases which phosphorylate other proteins) and synaptotagmin (subunits C2A and C2B insert into membrane upon Ca2+ binding)

Question 7

What represents the EPSP and what represents IPSP?

Answer 7

EPSP- depolarization
IPSP- hyperpolarization

Question 8

List the 5 major NXTs

Answer 8

1. Acetylcholine- excites skeletal, inhibits cardiac
2. Norepinephrine- excites cardiac
3. Epinephrine- excites cardiac
4. Dopamine- elevates mood + motor control
5. Serotonin- elevates mood, sleep/wake cycles, homeostasis, gastrointestinal

Question 9

Skeletal muscles are composed of longitudinal muscle fibers grouped into _________ held together by _________

Answer 9

fascicles
epimysium

Question 10

Each fasiculus is composed of muscle fibers held together by _______ . Longitudinally arranged muscle fibers are called ___________

Answer 10

perimysium
myofibrils

Question 11

Myofibrils contain contractile fibers ________ and _________

Answer 11

actin and myosin

Question 12

Nerve impulses originating ins somatic motor neurons of spinal cord synapse directly on _______ and release _________

Answer 12

sarcolemma and release acetylcholine (muscle fiber depolarization)

Question 13

What is the difference between neuromuscular junction and motor end plate?

Answer 13

Neuromuscular junction- where motor neuron stimulates muscle fibers
Motor end plate- where motor neuron stimulates using acetylcholine

Question 14

I bands

Answer 14

thin filaments primarily made up of actin

Question 15

A bands

Answer 15

thick filaments with some think filament overlap, made up of myosin

Question 16

H bands

Answer 16

centre of A band, NO filament overlap

Question 17

Z discs

Answer 17

centre of each I band (lines)

Question 18

Sacromere is composed of…

Answer 18

overlapping thick filaments (myosin) and thin filaments (actin)

Question 19

What is bound to Z discs and form Z-line (boundary of sarcomere)- Myosin or actin??

Answer 19

ACTIN

Question 20

Light I bands
Do these shorten?

Answer 20

actin does not overlap myosin
do shorten (thin filaments do NOT overlap)

Question 21

Dark A bands
Do these shorten?

Answer 21

overlapped actin and myosin
do NOT shorten (move closer together)

Question 22

What is the sliding filament theory?

Answer 22

sliding of thick and thin filaments shortens sarcomere

Question 23

What are the 6 steps of sliding filament theory?

Answer 23

1. Resting phase- myosin head not connected to actin and bound ADP and inorganic phosphate
2. Myosin head binds to sites on actin filament
3. Binding of myosin and actin releases bound Pi, causes conformation change in myosin
4. Power stroke occurs- filaments slide across each other- shortening sarcomere (release ADP)
5. New ATP binds to myosin head, releases connection to actin
6. Hydrolysis of ATP into ADP and Pi powers return of myosin to original conformation

Question 24

What is exciting contraction coupling?

Answer 24

provides control of muscular contraction

Question 25

Tropomyosin differences in activated and resting state, controlled by _______?

Answer 25

resting state- blocks interaction between myosin and actin (no contraction)
activated- reveals myosin binding sites, leads to attraction between myosin and actin (cross bridge formation occurs instantly)
controlled by troponin (induces the conformation change of tropomyosin to reveal myosin binding sites)

Question 26

What is responsible for controlling muscle contraction?

Answer 26

Ca2+

Question 27

Depolarization of transverse (T) tubules
- function
- receptors involved

Answer 27

function- transmit APs through muscle fibre to myofibrils
- depolarization activates Ca2+ channels- DHP receptors
- activation of DHP receptors leads to connection to ryanodine receptor- opens Ca2+ channels

Question 28

What is the function of pacemaker in cardiac muscle?

Answer 28

controls contraction (group of cells in left atrium)

Question 29

What is the role of Ca2+ in cardiac muscle?

Answer 29

acts as a secondary messenger to induce its own release- Calcium Induced Calcium Release (CICR)

Question 30

In smooth muscle, extracellular Ca2+ binds to ________ and activates __________

Answer 30

calmodulin and activates myosin light chain kinase (MLCK) which phosphorylates myosin light chain that allows for cross bridge formation between actin and myosin

Question 31

Relaxation in smooth muscle occurs after…

Answer 31

closure of Ca2+ channels and lowering of sacroplasmic Ca2+ concentration

Question 32

Dephosphorylation of myosin light chain leads to disruption of …

Answer 32

myosin and actin cross bridge and contraction