Bulging MUSCLES Flashcards
What are the 3 types of muscle tissue?
- Cardiac Muscle - found only in the heart
- Smooth Muscle - found lining hollow tubes and hollow organs
- Skeletal Muscle - found mainly attached to bone
Voluntary muscle (skeletal) is controlled by…
Skeletal Muscle, like nervous tissue, supports…
How many muscles are in the human body?
- somatic motor neurons and may be influenced by conscious decision-making centers in the cerebrum, subconscious fine-tuning (cerebellum for ex), or even initiated by reflex centers in the spinal cord
- supports an action potential
- well over 600 muscles in the human body
Functions of muscle
Movement: of bone, skin, and other tissue
Support: of body posture and position
Heat generation: resulting from metabolism of muscle tissue
What is a muscle fiber made from?
- embryologic myoblasts fuse to form a multi-nucleated muscle cell (muscle fiber)
(this is a distinguishing characteristic from smooth and cardiac muscle, both of which are composed of individual, single-nucleus cells)
- some myoblasts will become individual muscle stem cells called satellite cells, residing near nuclei in mature muscle fibers
Each muscle fiber is surrounded by___??
The fibers are bundled together into groups, enveloped by___??
Multiple groups are held together by___??
All of which are surrounded by___?
What is the tendon formed by?
- endomysium
-perimysium
- epimysium
- all surrounded by fascia, defining the individual muscle
- Tendon is formed by the convergence of all 3 layers of CT and serves as the attachment of the muscle to bone*
Organelle Nomenclature of Muscle
Sarcoplasm: cytoplasm within a muscle fiber
Sarcoplasmic Reticulum: the muscle fiber anatomic equivalent of the endoplasmic reticulum, which in this case stores calcium
Myoglobin: an oxygen-storing compound within muscle fibers
Each muscle fiber is innervated by only 1 motor neuron, but that neuron may innervate multiple muscle fibers..
Describe Motor Unit, Fine Motor Control, Motor Neuron Pool, Neuromuscular Junction
Motor Unit: motor neuron + all muscle fibers it innervates
The finest motor control is acheived by a neuron that innervates relatively fewer muscle fibers, while broader motor control involves a single neuron innervating 1000s of fibers
Every muscle has a motor neuron pool: a cluster of neuron cell bodies in CNS that innervate just that muscle
Each synaps of motor nerve to muscle fiber is termed neuromuscular junction
Sarcomere
- an individual contractile unit on a myofibril (100-1000s of myofibrils per fiber)
- sarcomere length is is determined by the longitudinal arrangement of 2 actin filaments each overlapping 1 central myosin filament (the degree of overlap varies depending on the sarcomere’s state of contraction vs relaxation)
Excitability
- muscle fibers at rest have a membrane potential similar to nervous tissue
- muscle responds to stimulation by nerves and hormones, making it possible for the nervous system to regulate muscle activity
Contractility
- muscle’s ability to shorten – based on myosin pulling actin
– both myosin and actin have multiple binding sites, allowing degrees of overlap (ROWBOATS)
Elasticity
- the ability of tissue to regain its original shape after being stretched, squeezed, or otherwise deformed
Action Potential
Where does it reach?
What neurotransmitter is released?
Directions of AP, AP eventually opens what?
- an action potential from a motor neuron reaches the neuromuscular junction at about midpoint of a muscle fiber. The neurotransmitter acetylcholine (ACh) is released from the axon terminal end (remember this is Ca dependent)
- the ACh opens Na channels on the muscle fiber membrane allowing Na to pour into the fiber, triggering the openin of voltage-gated Na channels and initiation of the action potential
- AP spreads in BOTH DIRECTIONS and TRANSVERSLY, intersecting with each end of every myosin filament – eventually AP opens Ca channels on Sarco Ret allowing Ca to flood sarcoplasm
- Ca helps expose actin for myosin bind, myosin uses ATP to pull actin and unit contracts
ATP also needed for myosin to disengage from actin
Sliding Filament Theory
- both actin and myosin have many binding sites along the length of their filaments so that multiple, sequential “pull and release” will lead to further shortening of the unit
Once the Action Potential ceases…
- ATP will again be needed both to move Ca back in to the sarcoplasmic reticulum to allow muscle relaxation and for the Na/K pump to reestablish normal resting membrane potential
ATP concentrations in resting membrane potential are sufficient to maintain about a _____ contraction
1-2 second
- beyond this, additional sources of evergy are required to re-phosphorylate adenosine diphosphate (ADP to ATP)
