Muscle Physiology (Lectures 29-32)

Question 1

Name the 3 types of muscles and whether or not they are voluntary or involuntary

Answer 1

1. Skeletal Muscle – voluntary
2. Cardiac Muscle – Involuntary (pumps blood)
3. Smooth Muscle – involuntary ( regulate blood pressure)

Question 2

Skeletal muscles are connected to _______ bones

Answer 2

at least 2

Question 3

Muscles are connected to bones by _____. (include def.)

Answer 3

tendons. Connective tissue that transmits force from muscle to bone

Question 4

The part of the muscle that generates force is called the ______

Answer 4

meat

Question 5

What is the epimysium

Answer 5

The outer layer connective tissue that extends from the tendons. These are a dense, irregular connective tissue layer.

Question 6

What is the perimysium

Answer 6

The perimysium extends into the body , dividing into numerous bundles

Question 7

what are fascicles

Answer 7

The numerous bundles divided from the perimysium

Question 8

What are muscles fibers

Answer 8

Muscle fibers are contained within fascicles , and have an elongated shape

Question 9

What is endomysium

Answer 9

A thin sheath that encases muscle fibers, and contains loos connective tissue, capillaries, and individual neuronal axons

Question 10

(T/F) Muscle Fibers have many nucleus

Answer 10

True.

Question 11

What are sarcoplasm

Answer 11

A muscle fiber’s semifluid cytoplasm.

It is packed with mitochondria and myofibrils

Question 12

What are myofibrils

Answer 12

rod-like elements within the sarcoplasm that contains contractile machinery

Question 13

what are sarcolemma

Answer 13

Plasma membrane of muscle fiber

Question 14

What are sarcoplasmic reticulum

Answer 14

saclike membranous network that surrounds each myofibrils. These play an important role in muscle contraction

Question 15

What are sarcomere

Answer 15

Fundamental units of myofibrils

Question 16

Each sarcomere comprises a bundle of overlapping ____ and __________ made of the proteins _____ and _____

Answer 16

thick and thin filaments

proteins actin and myosin

Question 17

Myosin I is a ____ unit while Myosin II forms ____.

Answer 17

Single // dimers

Question 18

Muscles contract by a ______ mechanism

Answer 18

sliding filament

Question 19

What is the sliding filament theory ?

Answer 19

Contraction is caused by the simultaneous shortening of all the sarcomeres. There is no change in either kind of filaments.

Question 20

Explain the myosin activity cycle

Answer 20

Originally, Myosin head is binded to actin filament ( rigor state)
Step 1: ATP binds to myosin, causing a detachment of myosin and active filament. (unbind)
Step 2: ATP hydrolysis results the head to move into a “cocked” position, leading a change in angle and weak binding to the actin unit.
Step 3: The binding of the Actin head results in a confrotational change which releases an inorganic phosphate
Step 4: The release of the inorganic phosphate causes a power stroke that returns the head to its uncocked position. This is then followed by a release of ADP

Question 21

_____ and ____ respond to _____ signaling to regulate muscle contraction

Answer 21

Troponin and Tropomyosin

calcium

Question 22

An increase in _______ triggers coordinated Actin/ Myosin II interaction

Answer 22

Calcium

Question 23

How does Ca+ affect Actin/ Myosin II interaction ?

Answer 23

Binding of Calciums to Troponin leads to an conformational change to tropomyosin. This reveals the binding site for actin/ myosin II binding.

Question 24

What causes the increase of Ca+ in the cytoplasm ?

Answer 24

An electrical signal is communicated to t-tubules. This arrival in electrical signal allows the release of Ca+ in the sarcoplasmic reticulum

Question 25

Explain how muscle contraction works by the rise of Ca+ (5 steps)

Answer 25

1. An action potential stimulates the muscle
2. The action potential reaches the T-tubules of the muscle fiber
3. This results in the release of Ca+ from the sarcoplasmic reticulum
4. Together calcium and ATP is required for the filament contraction between Myosin II and Active filaments
5. When the electric potential reaches normal. Ca+ is pumped back into the sarcoplasmic reticulum by a powerful Ca pump

Question 26

How does action potential stimulate the release of Ca+ in the sarcoplasmic reticulum

Answer 26

A muscle action potential triggers a conformational change in the DHP receptors that are located in the T-tubules. This triggers the open of ion channels ryanodine receptors, located in the sarcoplasmic reticulum which releases Ca into the cytoplasm.

Question 27

The only mechanism used to stimulate an action potential in a skeletal muscle membrane is the activation of a _______

Answer 27

motor neuron

Question 28

Motor neuron cells bodies are located in the _____ of the _____ or the ______

Answer 28

ventral horn of the spinal cord

brainstem

Question 29

What are 2 characteristics of motor neurons

Answer 29

They are myelinated and have the largest diameter axons

Question 30

A ____ motor neuron innervates ____ muscle fibers, but each muscle fiber is controlled by a branch from ______ motor neuron

Answer 30

single many

a single

Question 31

What is a motor unit ?

Answer 31

The motor neuron and the fibers it innervates

Question 32

(T/F) When an action potential occurs in a motor neuron, muscle fibers contract one at a time

Answer 32

False. When an action potential occurs in a motor neuron, all muscle fibers contract all together

Question 33

The vesicles found within the axon terminals of a motor neuron contain the neurotransmitter ______

Answer 33

ACh

Question 34

What is the neuromuscular junction.( NMJ)

Answer 34

The gap between the end axon terminal and the muscle motor end plate

Question 35

What are two main differences between interneuronal synapses and neuromuscular junctions

Answer 35

1. The magnitude in a single depolarization of the motor end plate ( EPP) is much larger than excitatory graded potential. This is because at the NMJ, neurotransmitters are released in a much larger area, which contains more N-ACh receptors.
2. inhibitory postsynaptic potentials do not occur. All neuronal muscular junctions are excitatory.

Question 36

______ receptors are found at the motor end plate

Answer 36

N-ACh (nicotinic )

Question 37

What is the function of tubocurarine

Answer 37

They are antagonists of N-AcH receptors which competes with AcH and leads to paralysis

Question 38

(T/F) NMJ can be both excitatory or inhibitory

Answer 38

false. NMJs are all excitatory.