Muscle Physiology Structure and Function - Lecture 27 Flashcards
What is Muscle Health Split into?
Powering Movement & Energy Expenditure
What do muscles help us do?
Helps us move and allows our body to function.
Calorie burning
Takes place in muscle
Functions associated with powering movement
ADLs (Activities of daily living), LTPA (Leisure Time Physical Activity), Occupation, Sport Performance
Good muscle health enables good performance of these?
Powering Movement
Presence or Absence of Comorbidities associated with?
Metabolic Engine
What are some comorbidities that form from muscle inactivity
Obesity, Diabetes, Sarcopenia
What happens to our energy expenditure and muscle mass as we become inactive?
Go down; less muscle, less calories burned, less metabolically active tissue
Consequences of unhealthy muscle?
Reduced Quality of Life and Independence (ADLs), Reduced Productivity, Limited Career options, increased risk of death/disease.
3 Types of Muscle in our body?
Cardiac, Smooth and Skeletal
Skeletal Muscle
Majority of the muscle in humans (70%), voluntary, multinucleated, cylindrical and long.
What does striation mean?
Pattern of lines or grooves
Is skeletal muscle striated?
Yes
Cardiac Muscle
Single nucleus per cell, Myogenic (own contraction pattern)
In cardiac muscle; apart of the sarcolemma and makes passage ways for cells to communicate, coordinate contraction and cohesive connection between cells
Intercalated disks
Is cardiac muscle striated?
More of a lattice like pattern/branched network
Sarcomere
Main contractile unit of contraction; in region of myofibril and makes patterns known as striations
Smooth Muscle
Single nucleus, fusiform (narrow at end and wide at front), non-striated, involuntary
How are the contractions for Smooth Muscle
Weak, slow and sustained because does not generate a lot of force in order to last a long time.
Where is smooth muscle usually found?
Internal organs - bladder, colon, stomach, esophagus, uterus, etc.
Types of Contraction?
Isometric (Not changing), Eccentric (Increasing), Concentric (Decreasing)
Outer most muscle dense sheath?
Epimysium
Perimysium (Fascicles)
Groups muscle fibres into bundles; packages the individual fibres.
Endomysium
Surrounds the individual muscle fibres
Single muscle fibre (muscle cell) is found within?
Endomisyium
Myofibrils
Contractile muscle containing filaments; contraction takes place, and give striated appearance
Does a muscle fibre have multiple myofibrils
Yes; a muscle cell will have multiple myofibrils with the purpose of having filaments for muscle contraction
Purpose of Motor Neurons and Blood Vessels in muscle fibres
They are intricately woven because muscles need blood flow and signals to contract and stay alive. They deliver and take things out of muscles
Muscle Fibre Nucleus/Nuclei
Governs cell behaviour, contains DNA
Sarcolemma
Muscle cell membrane; wraps around muscle fibre
Sarcoplasm
Cytoplasm, holds organelles
Sarcoplasmic Reticulum
Key for Calcium storage which is used for muscle contraction.
Contains filaments where muscle contraction takes place
Myofibrils
T-Tubule
Extensions of sarcolemma; allows signals from nervous system to penetrate into muscle fibre
Filaments in Sarcomere
Actin (Thin) and Myosin (Thick)
Actin and Myosin
Contractile proteins; Filaments arranged within sarcomere are what make striations in muscles
How do Actin and Myosin work
Actin and Myosin overlap and when muscles contract they overlap more, and when they relax they overlap less.
Z-line/disc
Divides sarcomeres as there are many in myofibril while acting as an anchor for actin filament.
Within the sarcomere; expands and shrinks with muscle contraction and has an M line running down the middle
H-zone
How many bands are there
A band and I band
A band?
Dark band which is Myosin (little actin)
I band
Light band (Actin)
Synapse
Connection between (synaptic cleft) end of one nerve to a muscle fibre
Action potential
Threshold of electric depolarization that causes signal to move down the line
How is action potential (signals) driven?
Driven by ions in the body
All or none response
The signal once it reaches the threshold must give an all out response or nothing at all.
Neuromuscular Junction
Where nerve meets with muscle
Axon
Passes signal down it and it’s covered by myelin sheath
Acetylcholine
Inside the axon terminal in the neuromuscular junction and released into space between nerve and muscle called synaptic cleft.
What happens after signal reaches the neuromuscular junction and releases acetylcholine
Signal travels down T-Tubules into muscle fibre cells and causes release of calcium.
What releases calcium?
Sarcoplasmic reticulum
Where does the process of signal reaching from nerve to muscle take place?
Neuromuscular Junction
What’s in Actin?
Tropomyosin and Troponin
Tropomyosin
Thin protein wrapped around actin that blocks binding sites for myosin while relaxed
Binding site for calcium; moves tropomyosin when calcium binds
Troponin
The Role of Calcium
When the signal reaches the sarcoplasmic reticulum, calcium releases and binds to troponin and exposes myosin binding site.
Sliding Filament Theory?
A formation of cross bridges with actin and myosin that involves ATP and calcium.
Step 1 of SFT?
Myosin heads energize by going from bent to stretched. ATP is hydrolyzed by heads into ADP and P
Step 2 of SFT?
Phosphate disappears and crossbridge is formed between Actin and Myosin
Power stroke; myosin head rotate to middle of sarcomere and pull actin along with it. ADP gets released
Step 3 of SFT
Detachment via ATP binding to Myosin
Step 4 of SFT
How does contraction happen continuously if ATP appears and blocks the connection?
As long as signal keeps going more calcium is released and ATP is available contractions can continue to happen
