Muscle Physiology (Lectures 29-32) Flashcards
Name the 3 types of muscles and whether or not they are voluntary or involuntary
- Skeletal Muscle – voluntary
- Cardiac Muscle – Involuntary (pumps blood)
- Smooth Muscle – involuntary ( regulate blood pressure)
Skeletal muscles are connected to _______ bones
at least 2
Muscles are connected to bones by _____. (include def.)
tendons. Connective tissue that transmits force from muscle to bone
The part of the muscle that generates force is called the ______
meat
What is the epimysium
The outer layer connective tissue that extends from the tendons. These are a dense, irregular connective tissue layer.
What is the perimysium
The perimysium extends into the body , dividing into numerous bundles
what are fascicles
The numerous bundles divided from the perimysium
What are muscles fibers
Muscle fibers are contained within fascicles , and have an elongated shape
What is endomysium
A thin sheath that encases muscle fibers, and contains loos connective tissue, capillaries, and individual neuronal axons
(T/F) Muscle Fibers have many nucleus
True.
What are sarcoplasm
A muscle fiber’s semifluid cytoplasm.
It is packed with mitochondria and myofibrils
What are myofibrils
rod-like elements within the sarcoplasm that contains contractile machinery
what are sarcolemma
Plasma membrane of muscle fiber
What are sarcoplasmic reticulum
saclike membranous network that surrounds each myofibrils. These play an important role in muscle contraction
What are sarcomere
Fundamental units of myofibrils
Each sarcomere comprises a bundle of overlapping ____ and __________ made of the proteins _____ and _____
thick and thin filaments
proteins actin and myosin
Myosin I is a ____ unit while Myosin II forms ____.
Single // dimers
Muscles contract by a ______ mechanism
sliding filament
What is the sliding filament theory ?
Contraction is caused by the simultaneous shortening of all the sarcomeres. There is no change in either kind of filaments.
Explain the myosin activity cycle
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
_____ and ____ respond to _____ signaling to regulate muscle contraction
Troponin and Tropomyosin
calcium
An increase in _______ triggers coordinated Actin/ Myosin II interaction
Calcium
How does Ca+ affect Actin/ Myosin II interaction ?
Binding of Calciums to Troponin leads to an conformational change to tropomyosin. This reveals the binding site for actin/ myosin II binding.
What causes the increase of Ca+ in the cytoplasm ?
An electrical signal is communicated to t-tubules. This arrival in electrical signal allows the release of Ca+ in the sarcoplasmic reticulum
Explain how muscle contraction works by the rise of Ca+ (5 steps)
- An action potential stimulates the muscle
- The action potential reaches the T-tubules of the muscle fiber
- This results in the release of Ca+ from the sarcoplasmic reticulum
- Together calcium and ATP is required for the filament contraction between Myosin II and Active filaments
- When the electric potential reaches normal. Ca+ is pumped back into the sarcoplasmic reticulum by a powerful Ca pump
How does action potential stimulate the release of Ca+ in the sarcoplasmic reticulum
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.
The only mechanism used to stimulate an action potential in a skeletal muscle membrane is the activation of a _______
motor neuron
Motor neuron cells bodies are located in the _____ of the _____ or the ______
ventral horn of the spinal cord
brainstem
What are 2 characteristics of motor neurons
They are myelinated and have the largest diameter axons
A ____ motor neuron innervates ____ muscle fibers, but each muscle fiber is controlled by a branch from ______ motor neuron
single many
a single
What is a motor unit ?
The motor neuron and the fibers it innervates
(T/F) When an action potential occurs in a motor neuron, muscle fibers contract one at a time
False. When an action potential occurs in a motor neuron, all muscle fibers contract all together
The vesicles found within the axon terminals of a motor neuron contain the neurotransmitter ______
ACh
What is the neuromuscular junction.( NMJ)
The gap between the end axon terminal and the muscle motor end plate
What are two main differences between interneuronal synapses and neuromuscular junctions
- 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.
- inhibitory postsynaptic potentials do not occur. All neuronal muscular junctions are excitatory.
______ receptors are found at the motor end plate
N-ACh (nicotinic )
What is the function of tubocurarine
They are antagonists of N-AcH receptors which competes with AcH and leads to paralysis
(T/F) NMJ can be both excitatory or inhibitory
false. NMJs are all excitatory.
