Vertebrates 9 - Muscular Flashcards Preview

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Flashcards in Vertebrates 9 - Muscular Deck (32)
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1

Muscle function

Support, movement of body or materials in it, vocalization, heat is a by-product

2

Smooth muscle

Looks smooth. Line the gut, bladder, blood vessels. Involuntary. Small, spindle-shape, mononucleate. Actin/myosin irregular arrangement.

3

Striated muscle

Regular cytoskeleton protein arrangement. Cardiac and

4

Cardiac muscle

Mononucleate or bi, separated by intercalated discs with gap junctions. Involuntary, myogenic contraction (autorhythmic)

5

Skeletal muscle

Large, polynucleate cells = myofibers made from fusing myoblasts. Neurogenic contraction (needs nerve stimulus). Similar in all vertebrates.

6

Structure of muscle

Muscle made of bundles of muscle fibers (cells), muscle fiber contains of bundles of myofibrils. Each segment of myofibril is a sarcomere

7

Sarcomere

I band (Z line in middle holding thin filaments), A band, H zone (M line in middle holding thick filaments) Thin filaments have actin.

8

Sliding filament theory (it’s proven)

I band disappears when contracted, sarcomere shrinks. Thick filaments have myosin heads which walk along actin of thin filaments. ATP binds, myosin head unbinds, cocks and cleaves ATP and binds to actin, ADP and P unbind and myosin flexes.

9

Why do the myosin heads change shape when ATP binds?

Energy interferes with the bonds that create the 3º struture

10

Proof for sliding filament theory study

electron microscopy on living rabbit muscle. Labelled the myosin heads with gold (electron dense). With no ATP added the heads didn’t move, did move with ATP about 20nm.

11

Regulation of Contraction

Thin filament is actin wrapped with tropomyosin with troponin attached. Ca binds to sites on troponin which exposes the binding sites for myosin. Troponin will be saturated with enough Ca, strongest force.

12

Excitation-Contraction coupling

Neuromuscular junction. Open Ca channels, NT released into cleft by exocytosis, lots of surface area on the muscle side for receptors, receptors release Ach, causes action potential in muscle.

13

Motor unit

A motor neuron and all the muscle fibers attached to it.

14

Innervation

In agnathans, not all of them are innervated, possibly “share”. All other vertebrates each muscle is innervated.

15

Electromyography

Measure electrical activity in muscles with electrodes

16

Latent period

Time b/w action potential in muscle and muscle contraction. The action potential has to travel down T tubule and release Ca from sarcoplamsic reticulum.

17

Sarcoplasmic reticulum

Modified ER. Spread throughout the cells, and wraps all the way around the myofibrils. Not used in protein formation etc. Ca retention and release.

18

Triad

One T tubules and two SRs that meet near the myofibrils.

19

How are action potentials linked to contraction?

Calcium. Helps actin and myosin interact in contraction.

20

Calsequestrin

Protein in the SR that binds Ca loosely. Helps regulate contraction

21

How does SR regulate Ca?

Contain Ca pumps which are always on. Help reuptake of Ca

22

Ryanodine receptors

Help in Ca movement. Found on SR membrane

23

DHPR

Dihydro puridine receptor. Voltage gated ion channel. On T Tubule membrane.

24

Steps to contraction

Depolarize T Tuble; change shape of receptors, Ca can leak out Ryano and DHPR. To stop we need to stop the nerve, everything repolarizes.

25

Reading: what is PEPCK

Phosphoenolpyruvate carboxykinase. PEP is the precursor to pyruvate in glycolysis (but PEPKC works in the other direction)

26

Reading: Roles and location of PEPKC

Involved in gluconeogenesis in the liver. Glyceroneogenesis in adipocytes (pyruvate/lactic acid made to fat)

27

Reading: What does lactic acid do? Where from?

Made from pyruvate when there is no oxygen. Leaks out of cell, changes pH and affects muscle activity. Goes through blood to liver, gluconeogenesis (Cori Cycle)

28

Reading: PEPCK experiment

Turn on PEPCK in skeletal muscle. Knock-in PEPCK gene with skeletal muscle actin promoter to be expressed in muscle; insert into stem cells, put into embryo, implant into surrogate mother, next generations will have the gene in their germ line

29

Reading: How to check that the PEPCK knock-in worked

Western blot using antibodies to show which tissues have that protein. WT only liver and kidney, no heart or skeletal muscle; +/+ also in skeletal muscle

30

Reading: Phenotypic differences in the PEPCK mice

Ate way more but stayed slimmer. Why? They were more active and burned it off. Huge endurance difference. Also, they aged slower and were fertile longer. And more aggressive.