Muscles

Question 1

What level of complexity is a reflex movement and where is it integrated?

Answer 1

Simple

In spinal cord/brain stem

Question 2

Where are more complex movements integrated?

Answer 2

Cerebral cortex

Question 3

What is the sensor of muscle length and where are they located?

Answer 3

Muscle spindle

Embedded in extrafusal muscle fibres

Question 4

What is the muscle spindle reflex?

Answer 4

Negative feedback loop

Increases muscle contraction in response to stretch or load

Question 5

What is the Golgi tendon reflex?

Answer 5

Excessive contraction stretches Golgi tendon

At threshold, reflex causes muscle relaxation

Question 6

What is a motor unit?

Answer 6

A single alpha motor neuron

+ all the fibres it innervates

Question 7

How many fibre types are contained in one motor unit?

Answer 7

One type

Question 8

How is a greater contraction generated?

Answer 8

Recruiting more muscle fibres

Question 9

What are some characterstics of slow twitch fibres?

Answer 9

High oxidative capacity

Earlier recruitment

Fatigue resistant

Question 10

What are some characteristics of fast twitch fibres?

Answer 10

High glycolytic capacity

Easily fatigued

Question 11

What wraps each muscle fibre?

Answer 11

Sarcoplasmic Reticulum

Question 12

What structure is associated with the thick filaments of a muscle?

Answer 12

Myosin

Question 13

What structure is associated with thin filaments of muscle fibre?

Answer 13

Actin

Question 14

What is a sarcomere?

Answer 14

A unit of thick and thin filament wrapped by SR

Question 15

What allows AP to easily interact with sarcomeres?

Answer 15

T tubules

Question 16

What enables greater muscle contraction through increased cross-bridge cycle activity?

Answer 16

Greater release of calcium from the SR

Question 17

What receptor controls the exit of calcium from the SR?

Answer 17

Ryanodine receptor

Question 18

What is tetanus and how does it occur?

Answer 18

Maximum contractile force of muscle

Build up of Ca²⁺ intracellular fluid as uptake is not keeping up

Saturation of Ca²⁺ binding sites

Result of burst of subsequent AP

Question 19

How can twitch duration be increased?

Answer 19

Keep calcium in intracellular fluid

Slow uptake of calcium

Question 20

What structure blocks myosin from binding to actin? How is this fixed?

Answer 20

Tropomyosin blocks actin molecules

Ca²⁺ binds to troponin to move tropomyosin

Question 21

What state is myosin in when no ATP is bound?

Answer 21

Bound to actin molecule at 45 degree angle

Question 22

When ATP binds to myosin what happens?

Answer 22

Myosin stops binding to actin

Question 23

What process occurs before myosin swings back and binds to actin again?

Answer 23

Hydrolyzation of ATP

Question 24

What is released from the myosin head when the powerstroke occurs?

Answer 24

Phosphate

(Tropomyosin also moved aside at this point)

Question 25

What is the last step of the crossbridge cycle?

Answer 25

ADP is released

Myosin resumes tightly bound 45 degree state

Question 26

In an isometric contraction, what happens?

Answer 26

Load exceeds contraction force

Muscle length is not changed

Question 27

What is the movement when a muscle is contracting but lengthening?

Answer 27

Eccentric contraction

Question 28

What is the relationship between contraction force and velocity of contraction?

Answer 28

Inverse

Question 29

At which point of contraction is the most force being exerted?

Answer 29

Isometric phase

Question 30

Power is a product of?

Answer 30

Force and velocity

(Cross sectional area and muscle length)

Question 31

What is optimal length?

Answer 31

Number of actin and myosin head bonds at a maximum

Greatest strength can be exerted by muscle

Question 32

Why is there a plateau in the AP in cardiac cells?

Answer 32

Calcium flows into the ICF

Ca²⁺ channel has slow gates

Allows heart to fill/prevents overworking

Question 33

Unlike the mechanical trigger to release Ca²⁺ in skeletal muscle from an electrical signal, cardiac muscle relies on what to release Ca²⁺ for the crossbridge cycle?

Answer 33

Influx of calcium through ryanodine receptor channels

(Calcium dependent calcium release)

Question 34

What helps uptake of extra Ca²⁺ in cardiac muscle?

Answer 34

Ca²⁺ and Na⁺ exhangers in combination with

K⁺ and Na⁺ ATP-ase

Question 35

In autorhythmic cells what voltage gate channel opens when an AP is intiated?

Answer 35

Ca²⁺ channels

Question 36

How does pacemaker potential regulation (the slow, spaced out depolarisation) occur?

Answer 36

An inward trickle of cations causing consistent depolarisation

Brings membrane potential closer to threshold always

Question 37

How are muscle fibres arranged in smooth muscle?

Answer 37

In bands/bundles

Fishnet of filament bundles allowing contraction all over

Question 38

What defines a single unit smooth muscle?

Answer 38

Muscle cells are linked electrically by gap junctions

Cells contract together

Question 39

What defines a multi-unit smooth muscle cell?

Answer 39

Each muscle cell is individually stimulated

Not electrically linked

Question 40

What is the process of smooth muscle contraction after Ca²⁺ dependent Ca²⁺ release?

Answer 40

Ca²⁺ binds to Calmodulin

Ca²⁺ Calmodulin activates MLCK

Active MLCK phosphorylates (adds phophate) to myosin (breaks down ATP)

Crossbridge cycle occurs

Question 41

What chemical is involved in smooth muscle relaxation?

Answer 41

Myosin phophatase

(Dephosphorylates myosin, myosin relaxes)

(Calcium reuptake as per cardiac process)