Muscle Tissue Flashcards
Relevance of muscle tissue? (3)
Muscle tissue is relevent…
- general knowledge
- physiology
- muscle disease and response to injury
- myopathies
- inflammation(myositis)
- myasthenia gravis
- cardiovascular disease
Muscle tissue: define, cells, origin,
Muscles= specialized cells capable of contraction to produce movement.
- aka myofibers
- Cells: spindle shaped
- Origin: from mesoderm (myoblasts)
- myoblasts fuse to make myotubes
- myotubes form myofilaments
- spme cells remain as mesenchymal= Satelite cells
Define: myotubes, myofilaments, satellite cells
Origin of muscle
Originates from from mesoderm (myoblasts)
- myoblasts fuse to make myotubes
- myotubes form myofilaments
- some cells remain as mesenchymal= Satelite cells
Define: sarcoplasm, sarcolemma, sarcoplasmic reticulum
Sarcoplasm: cytoplasn of muscle cells (w/glycogen and myoglobin)
Sarcolemma: plasma membrane of muscle cell
Sarcoplasmic reticulum: specialized smooth ER (Ca+)
Types of muscle
Types of muscle
Striated muscle
- skeletal muscle
- cardiac muscle
Smooth muscle
Myoepithelial muscle (basket cells)
Compare Striated Muscle types
Striated Muscle: Skeletal and Cardiac
Skeletal:
- myofibers= multi-nucleated
- voluntary contraction (sns)
Cardiac:
- Cardiomyocytes= one-nucleas in single cell (central)
- involuntary contraction (ans)
- intercollated discs
Skeletal Muscle
Skeletal muscle= type of striated muscle
- contracts fast and voluntarily
- 50% of body weight
- multiple nuclei
- Structure:
- whole muscle surrounded by epimysium
- perimysium divides muscle into smaller fascicles
- each fascicle is made of many myocytes/myofibers, which are surrounded by endomysium
- myofibers have bundles of myofibrils
- myofibrils contain smaller myofilaments (ACTIN/MYOSIN)
Structure of Skeletal Muscle
Structure of Skeletal Muscle
- whole muscle surrounded by epimysium
- perimysium divides muscle into smaller fascicles
- each fascicle is made of many myocytes/myofibers, which are surrounded by endomysium
- myofibers have bundles of myofibrils
- myofibrils contain smaller myofilaments (actin/myosin)
- myofilaments are what make muscle contract
Sarcomere: structure and function
Skeletal Muscle
Sarcomere= contractile unit of myocyte
*** distance from one I band to the next (A band in between)
- I band only has actin (lignt)
- z line is in middle of zone
- A band is where both overlap (dark)
- H zone is middle zone where only myosin is
- M line is middle line
Contraction of skeletal muscle: Legnths
Contraction of Skeletal Muscle
Each sarcomete shortens
- full contraction, Z lines are drawn closer to each other.
- I band almost dissappears
Myofilament legnth is constant
- thin filaments slide past thick filaments
Skeletal muscle contraction: molecular
Skeletal Muscle Contraction (after AP)
- Calcium binds troponin, moving tropomysin so myosin can bind actin.
- Atp moves myosin head
- contraction
t-tubules
Skeletal muscle: t-tubules
= deep invagination in sarcolemma that allows depolarization of membrane to penetrate to sarcoplasmic reticulum causing release of ca+
** terminal cisterna: expanded ends of sarcoplasmic reticulum
Red Muscle vs. White Muscle
Skeletal Muscle Fibers
Red Muscle vs. White Muscle
Red Muscle= slow twitch
- dark color- lots of myoglobin
- aerobic metablilsm= fatigue resistant
- high fat, low glycogen content
- many mitochondria
White Muscle= fast twitch
- anaerobic metabolism= prone to fatigue
- low fat, high glycogen content
Cardiac muscle: 5 facts
Cardiac muscle
- striated
- one nucleus
- Intercalated disk:
- gap junctions
- desmosomes
- sarcoplasmic reticulum
- many mitochondria!
Intercalated Discs
Intercalated Discs: attach cardiac muscle cells to each other providing stregnth and ability to function s a syncytium.
- Transverse element=anchor= Desmosome
- Longitudinal element=communication= gap junctions
NOTE: cardiac muscle is not a true syncytium because the cells work together but are not actually one unit.
(skeletal=true syncytium)
Cardiomyocytes: 2 types
Cardiomyocytes: 2 types
Contractile (red)
- duh…contraction
Conductile (pink)
- conduct impulses throughout heart
- less myofibrils (because they are more for communication than contraction)
- “smoother” cytoplasm
ANF/ANP
Cardiac muscle: ANF/ANP
Atrial Natriuretic Factor/Peptide= in atrial myocardium
- atrial muscle cells have atrial granules that have an ENDOCRINE function because of ANF/ANP
Smooth Muscle: 5 Facts
Smooth Muscle
- no striations
- still have actin and myosin (just not organized)=dense bodies
- desmosomes and gap junctions
- do NOT have sarcoplasmic reticulum and t-tubes
- INVOLUNTARY CONTRACTORS
Single-unit vs. multi-unit
Smooth Muscle: types
Single unit
- sparse innervation
- cells communicate via gap junctions
- in visceral organs (gut, bladder, reproductive syst…)
- wave like contraction
Multi unit
- precise contraction
- individual innervation of each myocyte
- no gap junctions (cells function individually)
- iris of eye
Smooth Muscle: Function (4)
Smooth Muscle: Function
Peristalsis- wave-like contractions (ex. gut)
Vascular dynamics- alters blood flow and pressure
Propulsion- urinary bladder, uterus
Secretion- minor role
Identify
Smooth muscle
Inner layer is circular layer (cells will be viewed as spindle)
outer layer is longitudinal (only see cross section of spindle cells)
Smooth Muscle Contraction
Smooth Muscle Contraction
- dense bodies= equivelent of z disk in skeletal muscle. anchors filaments
- can contract 80% shorter than normal
- Ach, NE, EP neurotransmitters!
Myoepithelial cells
Myoepithelial cells
- Origin: ectodermal
- Structure:
- actin and myosin
- basket cells (basket shape)
- Location:
- salivary glands
- mamary glands
- lacrimal glands
- Function:
- squeeze glandular cells
Satellite cells
Skeletal muscle has limited regeneration capacity
Sattelite cells: cells retain mitotic potential and can accomplish some repair
- Location: between basal lamina and sarcolemma of muscle cells
- scar tissue is formed by fibroblasts in repair process
NOTE: Cardiac cannot regenerate. Smooth limited regeneration.
Identify
Identify: Purkinje fibers
Purkinje fibers: modified cardiac muscle cells
- 1 or 2 nuclei
- bigger/paler cells than other cardiac muscle
- few myofibrils at periphery of cell
