Antomy Exam 2 pt3

What are the 3 types of muscles in the body?

What are the 3 types of muscles in the body?

skeletal, cardiac, and smooth

Smooth muscle

-narrow cilindrical fibers, non striated and uninucleate

-occurs in walls of internal organs

-involuntary

Cardiac muscle

-striated, branched, generally uninucleated fibers

-occurs in walls of heart

-involuntary

skeletal muscle

-striated, tubular, multinucleated fibers

-usually attached to skeleton

-voluntary

What are the functions of skeletal muscle?

body movement

maintenance of posture

protection & support

regulating elimination of materials

heat production

Characteristics of skeletal muscle tissue

excitability

conductivity

contractility

extensibility

elasticity

What is a bundle of muscle fibers?

fascicle

What are the 3 concentric layers of wrapping?

epimysium, perimysium. & endomysium

What is epimysium made up of?

-dense irregular connective tissue wrapping whole muscle

what is perimysium made up of?

-dense irregular connective tissue wrapping fascicle

-houses many blood vessels and nerves

what is endomysium made up of?

-areolar connective tissue wrapping individual fiber

-delicate layer for electrical insulation, capillary support, and binding of neighboring cells

Deep fascia

dense irregular CT superficial to epimysium; separates individual muscles

Superficial fascia

areolar and adipose CT superficial to deep fascia; separates muscles from skin

What bridges the gap between muscle ends and bony attachment?

tendons

What are the 3 parts of a muscle?

origin, belly, insertion

Origin

bony attachment at stationary end of the muscle

belly

thicker, middle region of muscle between origin and insertion

insertion

bony attachment to mobile end of muscle

What does vascularized mean?

deliver oxygen and nutrients, removing waste products

What does innervated mean?

axons of neurons branch terminate at neuromuscular junctions

-can allow for voluntary control of contraction

Sarcoplasm

has typical organelles plus contractile proteins and other specializations

Sarcolemma (plasma membrane)

-has t-tubules that extend deep into the cell

-voltage-gated ion channels that allow for conduction of electrical signals

-has voltage-sensitive calcium channels responsive to the electrical signals

Myofibrils

bundles of myofilaments enclosed in sarcoplasmic reticulum

Sarcoplasmic reticulum

internal membrane complex similar to smooth ER

Terminal cisternae

blind sacs of sarcoplasmic reticulum

-serve as reservoirs for calcium ions

-two cisternae with t-tubule in between= triad

What does calcium bind to be imported in?

calmodulin & calsequestrin

calcium release channels

triggered by electrical signal traveling down t-tubule; calcium released into sarcoplasm

Thick filaments

consists of bundles of many myosin protein molecules

What way does the myosin head point in thick filaments?

towards the end of the filament

Thin filaments

consists of bundles of many myosin protein molecules

What is thin filament made of?

-twisted strands of F-actin

-each F-actin composed of G-actin monomers

What regulatory protein are present in thin filament?

tropomyosin & troponin

Myofilaments

-elastic filament

-at least seven other accessory proteins

-dystrophin

What is the name of repeating myofilaments ?

sarcomeres

I bands

light-appearing regions that contain only thin filaments

-get smaller when muscle contracts

A band

dark-appearing region that contains thick filaments and overlapping thin filaments

-makes up central region of sarcomere

H zone

central portion of A band

-only thick filaments present; no thin filament overlap

-disappears with maximal muscle contraction

M line

middle of H zone

-protein meshwork structure

-attachment site for thick filaments

Connectin

extends from z disc to M line

-stabilizes thick filaments and has “springlike” properties (passive tension

Dystrophin

anchors some myofibrils to sarcolemma proteins

-abnormalities of this protein cause muscular dystrophy

Duchenne muscular dystrophy (DMD)

-defective or insufficient dystrophin

-sarcolemma damaged during muscle contraction

-problems can begin in early childhood

Myoglobin

cells allows storage of oxygen used for aerobic ATP production

motor unit

a motor neuron and all the muscle fibers it controls

Axons

motor neurons from spinal cord (or brain) innervate numerous muscle fibers

Synaptic knob

-expanded tip of the motor neuron axon

-houses synaptic vesicles

-has Ca+2 pumps in plasma membrane

-has voltage-gated Ca+2 channels in membrane

Motor end plate

specialized region of sarcolemma with numerous folds

-has many ACh receptors

synaptic cleft

narrow fluid-filled space

-separates synaptic knob from motor end plate

-acetylcholinesterase resides here

Resting membrane potential (RMP)

fluid inside cell is negative compared to fluid outside cell

-RMP of muscle cell is about -90mV