Bio 201 Exam 4

Front 1

From where does the energy come to shorten muscles?

Back 1

Muscle cells convert the chemical energy of ATP into mechanical energy.

Front 2

Three types of Muscle Tissue

Back 2

- Skeletal
- Cardiac
- Smooth

Front 3

Two Visual Categories of Muscle Tissue

Back 3

- Striated: Skeletal & Cardiac
- Unstriated: Smooth

Front 4

Two Functional Categories of Muscle Tissue

Back 4

- Voluntary: Skeletal
- Involuntary: Cardiac & Smooth

Front 5

Four Functions of Muscle Tissue

Back 5

- Movement of body parts & organ contents
- Control of passageways & openings
- Prevent movement - Communication
- Body heat production

Front 6

Universal Characteristics of Muscle

Back 6

- Excitability: responds to chem, stretch, elec. signals
- Conductivity: electrical change triggers excitation wave
- Contractility: Shortens when stimulated
- Extensibility - Elasticity

Front 7

Describe Skeletal Muscle

Back 7

- Voluntary striated muscle attached to bones
- Alternating light and dark transverse bands

Front 8

What are those Alternating light and dark transverse bands in Skeletal Muscle?

Back 8

- Overlapping arrangement of internal contractile proteins

Front 9

Three Parts of Skeletal Muscle

Back 9

- Origin: Attachment to stationary end of muscle
- Body: thicker middle region of muscle
- Insertion: attachment to mobile end of muscle

Front 10

Connective Tissue Elements of Muscle

Back 10

- Endomysium, Perimysium, epimysium, fascia, tendon
- Not excitable or contractile
- Somewhat extensible & elastic
- Called Series-elastic components

Front 11

What Do Series-Elastic Components Do?

Back 11

- Are connected to each other in linear series
- Help return muscles to their resting lengths
- Add Significantly to muscle power output and efficiency

Front 12

Describe Epimysium

Back 12

- Covers whole body of muscle
- Blends into connective tissue that separates muscles

Front 13

Describe Perimysium

Back 13

- Slightly thicker layer of CT than Epimysium
- Surrounds a bundle of muscle cells called a fascicle

Front 14

Describe Endomysium

Back 14

- Thin layer of areolar tissue surrounding each cell
- Allows room for capillaries and nerve fibers

Front 15

Location of Fascia: a fibrous connective tissue

Back 15

- Deep Fascia between adjacent muscles
- Superficial fascia (= hypodermis) found between skin and muscles. Contains adipose tissue

Front 16

Four Muscle Attachments

Back 16

- Direct (fleshy) attachment to bone
- Indirect bone attachment: epimysium - tendon - bone
- Attachment to dermis
- Attachment to other muscles

Front 17

Three Coordinated Muscle Actions

Back 17

- Prime Mover (antagonist): produces most force
- Synergist: aids PM, stabilizes joint, modifies direction
- Antagonist: Opposes PM, prevents excess movement & injury

Front 18

Describe Intrinsic & Extrinsic Muscles

Back 18

- Intrinsic: contained within region of movement
-- muscles of hand moving fingers
- Extrinsic: found outside region of movement
-- muscles of forearm moving fingers

Front 19

Skeletal Muscle Anatomy (8 major parts)

Back 19

- Muscle Belly - Fascicle
- Muscle Fiber/Cell - Myofibril
- Thick Filaments - Thin Filaments
- Actin - Myosin

Front 20

Sliding Muscle Theory

Back 20

- Muscle contraction is the result of thin filaments sliding past thick filaments.
- Pull on Z lines & shorten the sarcomere & the cell as a whole.

Front 21

Skeletal Muscle Fiber Anatomy

Back 21

- A band - H band - I band - M band - Z band - Z disc
- Nucleus - Mitochondria - Myofibrils
-Sarcoplasm - Sarcoplasmic reticulum - Sarcolemma
- Triad: - 2 Terminal cisternae - 1 Transverse tubule

Front 22

Muscle Fiber

Back 22

- Single skeletal muscle cell (up to 2.5 feet long)
- Multiple Mitochondria for ATP production
- Made of multiple myofibrils and nuclei from fused cells

Front 23

Parts of Muscle Fiber

Back 23

- Sarcoplasm: may contain glycogen & myoglobin
- Sarcolemma: Plasma membrane
- T (Transverse) -tubules: infoldings of sarcolemma

Front 24

Triad

Back 24

- 2 terminal cisternae & 1 Transverse Tubule
- Connects electrical signal on sarcolemma to release Ca from Sarcoplasmic reticulum

Front 25

Myofibrils

Back 25

- Specialized contractile element
-- 80% of muscle cell
-- 100s lie in parallel in a muscle cell
- Appears banded (striated) by thick & thin filaments

Front 26

Myofilaments

Back 26

- Thick filaments made of myosin with titin core
- Thin filaments made of Actin, Tropomyosin & Troponin

Front 27

Thick Filaments

Back 27

- 200 to 500 myosin molecules
-- 2 entwined polypeptides
- Core of titin recoils after stretching
- Arranged in bundle w/ heads out and bare zone

Front 28

Myosin Protein Making Thick Filament

Back 28

- 2 subunits with tails intertwined
- Globular head (paddle) has actin binding site and myosin ATPase site

Front 29

Thin Filaments

Back 29

- "String" of Balls of actin each with active site
- Double bands of tropomyosin (blocking protein)
- Troponin: Regulating protein of 3 subunits: Ca Binding, Actin binding, Tropomyosin binding

Front 30

3-D Actin-Myosin Interaction

Back 30

- Cross bridging: 16B thick & 32B thin filaments/fiber
- Geometric relationship: 1 thick surrounded by 6 thin

Front 31

Neuromuscular Junction

Back 31

- Where nerve fiber makes functional connection with a target muscle cell
- Acetylcholine (Ach) opens ligand-gated channels on muscle cells

Front 32

Motor End Plate

Back 32

- Specialized muscle cell membrane under terminal button
- Has ACh receptors, ligand-gated channels, ion channels
- Electrical change = end plate potential

Front 33

Nerve-Muscle Relationships

Back 33

- Cell bodies of somatic (alpha) motor neurons in brainstem or ventral horn of spinal cord
- Axons of SMN are called somatic nerve fibers
- Each branches to supply 200 fibers (motor units)

Front 34

Motor Unit

Back 34

- One motor neuron & innervated fiber
- Weak contraction over wide area
- Motor units take turns (asynchronous recruitment)
- Small and Large motor units

Front 35

Small Motor Unit for Fine Control

Back 35

- Contains as few as 20 muscle fibers per nerve fiber
- Small, controlled movements - e.g. eye muscles

Front 36

Large Motor Unit for Strength

Back 36

- Large contractions - e.g. posture
-- gastrocnemius has 1000 fibers per nerve fiber

Front 37

Acetylcholinesterase: The OFF Signal for the Neuromuscular Junction

Back 37

- Enzyme inactivates ACh by degrading it
- Always present in synaptic cleft
- Stops end plate potential (& muscle contraction)
- Keeps contraction proportional to nerve stimulation

Front 38

Toxins and Paralysis: Cholinesterase Inhibitors

Back 38

- Bind to AChesterase to prevent Ach degradation
-- Spastic paralysis, possible suffocation
-- Contracted muscles unable to relax
-- Used in some pesticides

Front 39

Toxins and Paralysis: Tetanus or Lockjaw

Back 39

- Spastic Paralysis caused by Clostridium bacteria toxin
- Blocks glycine release in the spinal cord

Front 40

Toxins and Paralysis: Curare

Back 40

- Competes w/ ACh: Binds to ACh receptors
- Prevents contraction, causing flaccid paralysis
- Can lead to respiratory arrest

Front 41

4 Actions Involved in Muscle Contraction and Relaxation

Back 41

- Excitation: APs in Nerve lead to APs in muscle fiber
- Excitation-contraction coupling link AP to myofilament activation (via Ca) -Contraction of muscle fibers
- Relaxation of muscle fiber to resting length

Front 42

Excitation of Muscle Fiber: Steps 1 & 2

Back 42

- Nerve signal (AP) stimulates voltage-gated calcium channels
- Causes exocytosis of synaptic vesicles containing ACh
- ACh released into synaptic cleft

Front 43

Excitation of Muscle Fiber: Steps 3 & 4

Back 43

- ACh binds to ligand-gated channels on muscle cell
-- Allows Na and K to diffuse
-- Results in an end-plate potential (EPP)
--- local/graded potential

Front 44

Excitation of Muscle Fiber: Step 5

Back 44

- Voltage change in end plate region (EPP) opens nearby voltage-gated channels in plasma membrane
--Produces AP on muscle cell (sarcolemma
- Whole sarcolemma gets action potential

Front 45

Excitation-Contraction Coupling

Back 45

- Links muscle APs and contraction
- ACh stimulates APs over the surface of whole fiber
- Transverse (T-) tubule: sarcolemma extention conducts AP along SR deeply into cell (triad) between A & I bands

Front 46

Sarcoplasmic Reticulum

Back 46

- Modified ER
-- Stores Ca++
-- Terminal cisternae sacks sit at junction of A & I bands

Front 47

Excitation-Contraction Coupling: Steps 6 & 7

Back 47

- 10,000x more Ca++ in SR than in sarcoplasm
- AP spreads over sarcolemma
- Enters T-tubules where Voltage-gated channels open
- Opens Ca gates in SR & Ca released to sarcoplasm

Front 48

Excitation-Contraction Coupling: Steps 8 & 9

Back 48

- Ca release by SR into sarcoplasm
- Ca binds to Troponin
- Troponin-tropomyosin complex changes shape and exposes active sites on actin - regulates contraction

Front 49

Contraction: Steps 10 & 11

Back 49

- Myosin ATPase in Myosin head hydrolyses ATP
-- Activates head and cocks it in extended position
-- Energy is now stored in myosin head
- Myosin binds to active site on actin

Front 50

Contraction: Steps 12 & 13

Back 50

- Power Stroke: head releases ADP and P as it flexes and pulls thin filament
- Binds more ATP, releases thin filament & attaches to new active site further down thin filament

Front 51

Power Stroke

Back 51

- Ca++ binds Troponin, which slides tropomyosin over, allowing Myosin to bind actin
- Binding causes conformational change: myosin bends inward, new ATP causes release, returns to original form

Front 52

Role of ATP

Back 52

- Myosin ATPase splits ATP, Energy stored (cocking)
- Ca allows power stroke: release of ADP & P from myosin
- New ATP binds to myosin/Mg complex for release (or else rigor mortis)

Front 53

Single Contraction

Back 53

- Shortens muscle by 1%
- Each head 5 strokes per second = 5 ATP
- Skeletal muscle can shorten up to 40%

Front 54

Relaxation: Steps 14 & 15

Back 54

- Nerve stimulation ceases
- AChesterase removes ACh from receptors
-- Ends stimulation of the muscle cell

Front 55

Relaxation: Step 16

Back 55

- Ca moved to Sr from sarcoplasm via active transport pumps
- ATP needed for relaxation as well as contraction
- Ca binds to calsequestrin in SR

Front 56

Relaxation: Steps 17 & 18

Back 56

- Loss of Ca from Carcoplasm results in troponin-tropomyosin complex moving back over the active sites
- Muscle fiber returns to resting length by stretching series-elastic components & antagonistic contractions

Front 57

Rigor Mortis

Back 57

- Begins in 3-4 hrs. Peak at 12 hrs. Next 48 to 60 hours
- Deteriorating SR releases Ca, activating contraction
- Relaxation needs ATP
- Fiber contraction continues until myofilaments decay

Front 58

Sarcomere: The Functional Unit of Skeletal Muscle

Back 58

- Z-line to Z-line
- Smallest component of muscle that can contract

Front 59

Striations: Organization of Filaments

Back 59

- Dark anisotropic (A) bands / Light isotropic (I) bands
- A band of thick filaments end to end
- H band: lighter central area without thin filaments
- I band: light region, thin filaments w/ Z-line & connectin

Front 60

A Band (Dark Band)

Back 60

- Thick filaments
- Part of thin filaments
- H zone where thin filaments do not reach
- Support Proteins of M-line anchoring thick Filaments

Front 61

I Band (Light Band)

Back 61

- Contains only thin filaments, but not their whole length
- Space between thick filaments
- Z-line: Cytoskeletal structure, protein called connectin, anchoring elastic & thin filaments

Front 62

Elastic Filaments

Back 62

- Titin: Huge springy protein runs through core of each thick filament, connects thick filament to Z disc structure
- Functions: keep thick & thin aligned, resist overstretching, help cell recoil to resting length

Front 63

Sarcomere Contraction: Muscle Cells Shorten Because Their Individual Sarcomeres Shorten

Back 63

- Sliding filaments: thin slide closer together
-- I band shorter, A band unchanged, H zone shorter
- Filaments don't change length, only overlap increases

Front 64

Twitch

Back 64

- contraction produced by one action potential on one muscle fiber

Front 65

Tension

Back 65

- amount of contraction per fiber
-- number of muscle fibers contracting

Front 66

Recruitment

Back 66

- turning on more and more motor units
-- to increase tension in whole muscles

Front 67

Length-Tension Relationship

Back 67

- Amount of tension generated depends on length of muscle before it was stimulated
- Central Nervous System maintains optimal length
-- muscle tone

Front 68

Phases of a Twitch Contraction

Back 68

- Latent period: between stimulus and contraction start
-- only elastic components, so no shortening
- Contraction: external tension develops/muscle shortens
- Relaxation: tension loss, returns to resting length

Front 69

Twitch Summation

Back 69

- incomplete tetnus
- next signal to contract comes before muscle has fully relaxed
- Each stimulus creates identical response 10/sec max

Front 70

Complete Tentus

Back 70

- Sustained maximal contraction
-- increased cytosolic Ca++
- twitchs fuse into smooth prolonged contraction; no relaxation; 40-50 stimuli per second

Front 71

Treppe

Back 71

- Each twitch has time to recover but develops more tension than the one before; 10-20 stimuli per sec
- Ca++ not completely back into SR
- Heat of tissue increases myosin ATPase efficiency

Front 72

Incomplete Tetnus

Back 72

- sustained fluttering contractions generates gradually more strength of contraction
- higher frequency 20-40/sec
-- each stimulus arrives before recovery of the previous

Front 73

Recruitment & Stimulus Intensity

Back 73

- stimulating the whole nerve with higher and higher voltage produces stronger contractions of motor units
- multiple motor unit summation: more motor units are being recruited as more work is done

Front 74

Isometric & Isotonic Muscle Contractions

Back 74

- Isometric: develops tension without changing length
- Isotonic:
-- Equal tension while shortening: Concentric
-- Equal tension while lengthening: Eccentric

Front 75

Muscle Sensors: Muscle Spindles

Back 75

- monitor change in muscle length
- has own efferent and afferent nerve supply (gamma motor neurons) to keep spindles taut
- annulospiral and flowerspray sensory nerve endings

Front 76

Muscle Spindle Nerve Endings: Annulospiral

Back 76

- Wrapped around intrafusal fiber
- Sense length and rate of stretch

Front 77

Muscle Spindle Nerve Endings: Flowerspray

Back 77

- at end of intrafusal fiber
- senses length

Front 78

Muscle Sensors: Proprioception

Back 78

- Sense of body position and movement

Front 79

Stretch Reflex

Back 79

- Stretch sensed by muscle spindles
-- activate alpha motor neurons
-- cause contraction
--- e.g. patellar tendon reflex

Front 80

Golgi Tendon Organs

Back 80

- Located in tendons
- Sense muscle tension; tension stretches receptors
- Reaches conscious level: proprioception
-- ability to weight objects

Front 81

Muscle Metabolism

Back 81

- Need ATP for power stroke, release of actin/myosin cross bridge, active transport of Ca into SR
- 3 major sources: Phosphagens (1-20 seconds), Glycolysis (10-120 secs), Aerobic Respiration (2+ min)

Front 82

Phosphagen System

Back 82

- Provide energy for immediate needs
- Transfer phosphate groups to ATP
- Myokinase system: P from ADP to ADP = ATP + AMP
- Creatine kinase sys: P from creatineP = ATP + creatine

Front 83

Glycolysis

Back 83

- Anaerobic: makes 3 ATP net
- Pyruvic acid converted to lactic acid

Front 84

Aerobic Respiration

Back 84

- Citric Acid Cycle in mitochondria
- Aerobic
- 36 to 38 ATP net
- limits: glycogen depletion and fluid/electrolyte loss

Front 85

Fatigue

Back 85

- Progressive weakness and loss of contractility from prolonged use

Front 86

Endurance

Back 86

- Ability to maintain-intensity exercise
- Depends on the supply of organic nutrients

Front 87

Slow & Fast Twitch Fibers

Back 87

- Slow oxidative fibers: more mitochondria, myoglobin & capillaries
- Fast glycolytic fibers: phosphagen enzymes & glycogen lactic acid systems SR releases Ca quickly

Front 88

Oxygen Supply

Back 88

- Slow Red Fibers rich in Myoglobin
- Fast White Fibers poor in Myoglobin

Front 89

Oxygen Debt

Back 89

- Excess Post Exercise Oxygen Consumption
- Replaces Oxygen reserves
- replenishes phosphagen system
- reconverts lactic acid to glucose

Front 90

Muscle Efficiency

Back 90

- At rest: 58% of energy lost to body heat
- Active skeletal muscle: 85% loss to body heat

Front 91

Smooth Muscle

Back 91

- Around tube and hollows
- Sheets of spindle-shaped cells; no Z-lines or banding
- No troponin or tropomyosin; little SR; No T-tubules
- Very slow cycles; uses 10 to 300x less ATP

Front 92

Smooth Muscle

Back 92

- Dense Bodies: Same protein as Z-lines
- 10 - 15 thin per thick filaments
- Huge contractility

Front 93

Smooth Muscle Contraction

Back 93

- Ca++ from ECF binds to calmodulin
- complex binds to myosin light chain kinase
- MLCK uses an ATP to phosphorylate cross-bridge
- Cross-bridges bind to actin

Front 94

Smooth Muscle Response to Stretch

Back 94

- Opens mechanically gated calcium channels
- Tissues briefly contract then relax

Front 95

Types of Smooth Muscle

Back 95

- Multiunit: Nerves to individual myocytes in motor unit
- Single Unit

Front 96

Multi Unit Smooth Muscle

Back 96

- Neurogenic contraction

Front 97

Cardiac Muscle

Back 97

- Combination of features from skeletal and single unit smooth muscle
- Involuntary & striated

Front 98

Single Unit Smooth Muscle

Back 98

- Electrically linked via gap junctions
- self excitable
- Autonomic Nervous System

Front 99

Cardiac Muscle

Back 99

- Cells are shorter, thicker, have anastamoses
- linked at intercalated discs
- Autorhythmic due to pacemaker cell
- Use Aerobic Respiration

Front 100

Spontaneous Depolarization

Back 100

- Pacemaker Potentials
- Slow wave potentials: in digestive tract