The Muscular System Flashcards by Bri :)

What are the 3 types of musculature?

skeletal
cardiac
smooth muscle

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Where do MOST muscles arise from?

the paraxial mesoderm

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What is included in the paraxial mesoderm and what do they turn into?
(the 3 parts)

Somites -> muscles of the axial skeleton, body wall, and limbs
Somitomeres -> develop into the muscles of the head
Ventrolateral & dorsomedial lips -> progenitor cells for skeletal muscle

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What are myogenic cells separated into?

Epimere (dorsally)
Hypomere (ventrally)
Somites (somatic mesoderm and neural crest cells)

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Myoblasts from the epimere fuse to form the _______ m. of the _______ ____.

extensor muscles of the vertebral column

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The myoblasts of the hypomere form the _______ and _________m.

limb and body wall muscles

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Connective tissue derived from somites, somatic mesoderm, and neural crest (in the head region) form the template for the _______.

muscle patterns

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Tendons arise from the _______.

syndetome

sounds like tendon

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What are some characteristics of skeletal muscle?

multinucleated
cylindrical monocytes (in bundles)
peripherally located nuclei
striations
voluntary (quick and forceful)

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What are some characteristics of cardiac muscle?

Branched cardiac myocytes
Centrally located nuclei (united by intercalated discs = gap junctions)
Involuntary, vigorous, rhythmic movement

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What are some characteristics of smooth muscle?

Fusiform (spindle) cells
NO striations
Involuntary, slow
Central, single elongated nucleus

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Muscle cells are specialized for ______.

contractility

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What is the difference between a myocyte and myofiber?

A myocyte is a muscle cell, while a myofiber is a muscle fiber

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What are some characteristics of skeletal myofibers?

non-branching
elongated
cylindrical
multi-nucleated
striations

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The multiple nuclei of the myofibers are arranged at the _______ of the cell beneath the sarcolemma

periphery

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Sarcomeres are regular repeating subunits of myofibers, and they lead to the ____ of skeletal muscle.

striation pattern (myofilaments)

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What are some macroscopic/ gross characteristics of skeletal muscle?

surrounded by dense fibrous CT, that consists of deep fascia blending internally with the epimysium

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The thin septa from the epimysium extend into the muscle and divide it into _____ (groups) of myofibers. This is called the _______.

fascicles; perimysium

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The endomysium surrounds the _______.

sarcolemma

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The sarcolemma is the ________ of the cell.

plasma membrane

Individual muscle fibers are surrounded by _______.

Endomysium

What transfers the mechanical force of contracting muscle cells through all the layers?

Structural transmembrane proteins which attach to the basal lamina

The sarcoplasm (cytoplasm) contains abundant _______.

myofibrils

Each sarcomere is composed of thin and thick _______.

myofilaments

Thin and thick filaments align precisely to form ___ and ___ bands

A; I

What are some features of A bands?

- wider and darker than I bands (anisotropic = alter polarized light)

What are some features of I bands?

- lighter and narrower than A bands (isotropic = don't alter polarized light)

What do thin myofilaments consist of?

Actin, tropomyosin, and troponin

What do thick myofilaments consist of?

Myosin

What is the function of the sarcoplasmic reticulum?

It is the site of storage and release of Ca2+ for uniform myofiber contraction

Where are Z lines found and what do they do?

- In the middle of I bands - Define the length of a sarcomere ( from Z line to Z line)

Where are neuromusclular junctions located?

At the termination of motor nerve axons

What occurs at the neuromotor junctions?

- The terminal axon has synaptic vesicles containing the neurotransmitter acetylcholine - Between the axon & muscle is the synaptic cleft

What are Satellite cells (resting myoblasts), and what do they do?

Adult monocyte stem (progenitor) cells They are the main cell involved in muscle regeneration/ repair- they produce new myofibers following an injury

What are the 3 major physiologic features that classify the different fiber types?

- Rate of contraction (slow or fast) - Rate of fatigue (fatigue resistant or fatigue sensitive) - type of metabolism (oxidative, glycolytic, or intermediate)

What is type 1 fibers called and what are its characteristics?

Red muscle - Slow twitch - Fatigue resistant - Oxidative (aerobic) metabolism -> have a high concentration of mitochondria and myoglobin (ex: diaphragm and postural muscles)

What is type 2 fibers called and what are its characteristics?

White muscle - Fast twitch - Fatigue sensitive (due to accumulation of lactic acid) - Glycolytic (anaerobic) metabolism --> high [glycogen] w/ few mitochondria & [myoglobin] (ex: sprinting muscles (athletic muscles)

What are type 2a fibers?

(intermediate, oxidative-glycolytic) - Fast contracting - Fatigue resistant - Use oxidative metabolism and anaerobic glycolysis to produce energy - intermediate amnts of mitochondria, myoglobin, and glycogen

What are type 2b fibers?

(Glycolytic) - Fast contracting - fatigue sensitive (rapid accumilation of lactic acid)

Do dogs have Type 2b fibers?

What are cardiac muscle cells called?

- Cardiac myocytes - Cardiomyocytes (most used) - Myocardiocytes

What are some characteristics of cardiomyocytes? (cardiac muscle cells)

- Striated - 1 centrally located nucleus per myocyte - Branch to join with other myocytes via intercalated discs (gap junctions) - intercalated discs contain many junctional complexes providing strong intercellular adhesion

How is an electrical impulse carried throughout cardiac muscle?

Intercalated discs have gap junctions, which provide ionic continuity between cells. This promotes rapid impulse conduction through cardiac muscle cells simultaneously, and allows contraction of many adjacent cells as a unit.

How do cardiac myocytes rhythmically contract in the heart?

By the conduction system - SA node, AV node, & Purkinje fiber network (NOT THE SAME AS PURKINJE CELLS) - contractile elements (myofibrils) similar to skeletal muscle, but fewer and less organized - Abundant mitochondria, glycogen granules, and small lipid droplets

Smooth muscle is the major component of _______/______.

tubular structures/ organs

What are some examples of smooth muscle areas?

digestive, respiratory, urinary, reproductive systems and blood vessels

Smooth muscle cells are linked by numerous __________.

gap junctions

The myofibers of smooth muscles are surrounded by an ________ and a _______.

external lamina; scant endomysium