Lecture 6 - Neuromuscular System 1

Question 1

Hierarchy of Muscle Structure

Answer 1

Largest to smallest

Tendon - Attached to bone
Deep Fascia - Fibourus, surrounds muscle
Empimysium - type of tissue
Blood vessels - embedded in epimysium
Perimysium - bundles of muscle
Fascicle- group of muscle fibers
Endomysium- muscle surrounding membrane
Muscle fiber - cell
Blood capillary
Sarcolemma- muscle membrane
Motor neurone-causes muscle to contract, embedded in muscle mem
Myofibril-Sarcomeres, Myofilaments and Actin/Myosin

Question 2

Sarcolemma

Answer 2

Muscle membrane, phospholipid bilayer. Important for action potential propagation.

Hormone receptors (glycoproteins), receive ACh and insulin among other things

Ion channels

Ion pumps/transporters

Enzymes and binding proteins, structural proteins

Question 3

Myofibril and Sarcomere structure

Answer 3

Myofibrils are made up of repeating units called sarcomeres

Contain thick (myosin) and thin (actin) filaments

Question 4

Muscle contraction 1. Excitatory-contraction coupling

Process of transforming AP to muscle contraction

Answer 4

1. ACh released from pre synaptic terminal (neuron) to post synaptic receptor (muscle)

Synaptic vesicles leave presynaptic terminal through diffusing across the synaptic cleft. Then attach to receptors on sarcolemma

2. Action potential long sarcolemma, requires ATP as it moves against diffusion gradient
3. AP depolarizes T tubules as it travels down and causes Calcuim release from sarcoplasmic reticulum
4. Calcuim goes to cross bridge cycling step. Requires SERCA pump and requires ATP

Question 5

Muscle contraction 2. Cross bridge cycling

Answer 5

ATP is hydrolysized ATP turns into ADP + P

When calcuim binds to troponin it exposes site and this is where actin and myosin bind

The bound myosin pulls on the actin performing a power stroke

ADP + P will release and a new ATP will attach so the myosin cause detach from actin

Question 6

Sliding Filament Theory

How the muscle contracts

Answer 6

Myosin (thick) slides past actin (thin) while lengths stay the same

Question 7

Types of muscle contractions

Answer 7

Isometric = no movement, some actin and myosin overlap. Muscle tightens but not moving along join

Concentric =muscle shorting (bicep curl) Sliding movement allows myosin to become overlapped by
actin

Eccentric = muscle lengthening
External stretching force pulls actin away from myosin. Sarcomeres get pulled from each other

When one muscle concentrically contracts (shortens), another one eccentric contracts (lengthens). Antagonist muscle does oppisite

Bicep curl = bicep short while tricep long

Question 8

Force length relationship

Answer 8

About finding optimal length to maximize force

Longer the muscle the more force BUT if its too long it starts to weaken

Optimal amount of myosin and actin attachments

Question 9

Frequency, force and calcium relationship

Answer 9

1 HZ=1 stimulus per second
-aka how much calcium is releases

More frequency of stimulus the more spikes, more spikes, less chance to relax.

Single muscle twitch is a high spike and lots of rest

Unfused tetanus means the force is spikey with less height and more of them

Fused tetanus is when the force is continuously being produced and it adds up

When a threshold is reached it becomes a plateau is reached with no spikes but highest force

Question 10

Force velocity relationship

Answer 10

Really high force at lower shortening velocity

Inverse relationship

Higher the shortening velocity , the less opportunity for cross bridges to form

Question 11

power velocity relationship

Answer 11

Max force/power at 1/3 of Vmax

P=F x V

Relationship between power and shortening velocity