Use the diagrams in the book to enhance comprehension of these concepts.

The function of Muscles

Movement - contraction of the sarcomere; this is the primary function.  Movement gives the organism the ability to access food and avoid predators.
Support - muscles support the tissues around them.
Protection - muscles are a physical barrier that cushions the bones and internal, soft
     organs from blunt force trauma.
Heat - produced during aerobic cellular respiration.  Aerobic CR releases 60% of
     the energy in a glucose molecule as HEAT.  We use this to maintain homeostasis
    of body temperature - 98.6 F

The functional unit of muscle is the SARCOMERE
   What is the functional unit of the muscle cell?
   Why is the sarcomere the functional unit?
The sarcomere is the unit that contracts, and contraction of the sarcomere is the function that produces movement.

What is THE primary function of muscle tissue?
Movement - movement allows the organism to respond to its environment by running away or fighting, foraging for food, passing food through the digestive tract, and passing absorbed nutrients through the vessels.+

Movement: two types

Locomotion - movement of the entire organism: walking, running, etc movement of the
     skeletal muscle
Propulsion - movement of a substance through a tube, or other body part. 
      Blood through arteries and veins; food through the alimentary canal.
 

Describe the 3 types of muscle tissue and the general characteristics of each type

Skeletal muscle is 'voluntary' - this means that your nervous system consciously, willingly controls these muscles.  They are controlled by the Somatic Nervous System.

Smooth and Cardiac muscle is INvoluntary - you do NOT consciously control these - they are controlled by the Autonomic Nervous System.

Cardiac is 'automatic' because it will contract due to stimulation by stretching - and does NOT require direct control by the nervous system.

Sarcomeres are arranged in STACKS in skeletal and cardiac muscle - which gives them a striated (striped) look when viewed under a microscope (see illustrations in the book)..  In Smooth muscle fibers, the sarcomeres are haphazardly arranged - therefore, no striations.

Skeletal muscle is called skeletal because it is attached to the bones of the skeletal system and MOVES those bones as the somatic nervous system dictates.  Skeletal muscle's function is LOCOMOTION - movement of the whole organism.

Cardiac muscle is called cardiac because it makes up the heart wall.  Cardiac muscle's function is PROPULSION of blood.  Cardiac muscle squeezes blood inside the heart, which causes high blood pressure inside the heart, and blood is propelled out of the heart to areas of lower blood pressure.

Smooth muscle is found in the walls of the hollow organs: blood vessels, gastrointestinal tract, bladder(s), etc. Smooth muscle has several functions:
      1. to control propulsion of blood through vessels (and vascular blood pressure)
      2. propel substances through ducts and hollow organs:
               - food through the digestive tract,
               - urine through the ureters,
               - bile through the bile duct, etc.
     It is called 'smooth' because it is NONstriated and looks smooth under a microscope. 
     Smooth muscle fibers contract more slowly than do Skeletal and Cardiac.

Ca++ is stored in the cisternae (sarcoplasmic reticulum) in both Skeletal and Cardiac muscle.  Ca++ is extracellular in Smooth muscle.

Tetany is a sustained muscle contraction - a contraction that does NOT relax.  Think cramp.  Skeletal muscles experience tetany, while Smooth muscle is resistant to tetany, and Cardiac muscle does NOT experience tetany.  Tetanus is a potentially lethal infection in which the Clostridium tetani bacterium causes 'paralysis' of the diaphragm - and respiration stops, the victim dies of asphyxia. 

What is the function of the heart? (see the chapter on cardiac tissue)
   Why is it a real good thing that cardiac muscle does NOT experience tetany?

Cardiac muscle fibers are branched an have intercalated discs (gap junctions) that connect each cell to the adjacent cells.  This structure allows the cells to communicate with each other VERY rapidly, which allows them all to contract at the same time.

All muscle cells have myoglobin (which is similar to hemoglobin).  Myoglobin and hemoglobin both bind to O2.  Hemoglobin carries O2 in the blood, while myoglobin STORES O2 in the muscle tissues. 
    Why do we need a molecule that binds to O2?
         What is the role of O2 in the body?
O2 is required for aerobic cellular respiration to extract stored energy from glucose and transfer that energy to ATPs.  Muscle requres LOTS of ATP for contraction. 
     What is the role of ATP in muscle contraction? 
        ATP 'energizes' the myosin swivel head causing it to 'break the bond' with the active site and
           release from the active site - which either allows the swivel head to pivot and grab another
           active site for more contraction - OR - allows the myofilaments to slide back apart - which
           allows the muscle to RELAX..

Cardiac fibers contain LOTS of myoglobin molecules - which gives heart muscle its deep, dark red color.  Skeletal muscle fibers have an intermediate amount of myoglobin which gives skeletal muscle its red color.  Smooth muscle fibers contain less myoglobin and are therefore, pink in color.

A muscle cell is also called a muscle fiber.
Each individual muscle cell (like every other cell in your body) is surrounded by the
       endomysium - which is Areolar LOOSE Connective Tissue.  The endomysium protein
       fibers hold each cell (connect each cell) to one another to maintain the integrity of each
       to one another.  This helps the fibers to move together, to produce a coordinated
       movement.
   A group of muscle fibers is called a Fascicle.
Each Fascicle is surrounded by the perimysium - Irregular DENSE CT.  The perimysium is
       a membrane between fascicles that allows individual fascicles to move against other
       fascicles without damaging either - as well as connecting the fascicles and holding
       them together in a coherent unit - which allows the fascicles to work together in a
       coordinated movement.
   A group of Fascicles forms a Muscle.
Each MUSCLE is surrounded by the Epimysium AKA Fascia -  Irregular DENSE CT.  (The
       fascia is that really tough, white 'membrane' that you can see on the surface of meat in the
       grocery store.)  The fascia seperates individual muscles and allows them to move
       (contract) against each other and other structures such as bone, without damage to the
        muscle or to other structure.

A muscle cell contains myofibrils which are made of myofilaments.
The two major myofilaments are mysosin (thich myofilament) and actin (thin myofilament).
The myofibril extends the length of the muscle fiber and is made up of subunits called sarcomeres.

Each Myofibril is made up of thousands of Sarcomeres, laid end to end.
There are hundreds of myofibrils in each muscle fiber.  I.e. there are LOTS of sarcomeres
   in each muscle cell!  Each sarcomere contracts - just a little bitty bit.  But, add up all the little
   bits, and you have a muscle that shortens by a couple of inches.

A sarcomere is the basic contractile unit of a muscle cell.
The myofibril consists of a chain of sarcomeres and each sarcomere begins and ends with a Z-line.
When the sarcomere shortens (the Z-lines get closer together) the muscle cell is contracting.

What is the basic contractile unit of a muscle fiber?
What is the basic functional unit of a muscle?
What is the function of muscle tissue?

Refer to the diagram of a sarcomere, in your book.  Locate these structures:

Z-line - one at each end of each sarcomere
Actin myofilament - one end attached to a Z-line
  Active sites on Actin myofilament
Myosin myofilament - in between Z-lines and parallel with actin myofilaments.
   Myosin swivel heads on myosin myofilament
   Myosin has 2 (two) ends and is NOT connected to the Z-line.

Notice that the ACTIVE sites on the actin are covered up by troponin and tropomyosin molecules.

During a muscle contraction, the Actin and Myosin myofilaments slide passed each other. 

Imagine that you and 5 other people, are pulling on a rope, attached on the other end to a car.  As you pull on the rope, your hands come close to you and you let go with one hand, reach forward and grab the rope again and keep pulling.  As you and your friends continue this, you 'slide' along the rope, and the car is pulled toward you.  AND, you are using energy. 

Now, imagine that the myosin swivel heads 'grab' the active site on the actin and swivel, which PULLS the actin and myosin passed each other. The swivel heads release, reach forward and grab the next active site and swivel again.  The myosin is pulling the Z-line toward the end of the myosin.  Each end of the myosin pulls a Z-line towards the myosin.  This causes the sarcomere to shorten - i.e. contract.

All the sarcomeres in a muscle cell do this at the same time - contraction of that cell.
All the muscle cells in a fascicle do this at the same time - contraction of that fascicle.
All the fascicles in a muscle do this at the same time - muscle contraction.

NOW - WHY does a sarcomere 'contract'?
The nervous system sends a signal (and Action Potential) that TELLS the muscle cell to contract.  I.e the AP excites/stimulates the muscle cell.

How does the Neuron stimulate the muscle cell?

Review Chapter 3, the Cell and its parts. 
  Review the types of organelles.
    The myofilaments in the sarcomere are proteins - cytoskeleton type. Muscle tissue contains LOTS of proteins - which is why you eat meat to get protein in your diet.
Review the different types of Organic molecules and their building blocks.

Look at the diagram of the neuromuscular junction in your book.  Locate these parts:

The goal is to create an AP in the post synaptic membrane:

This part is the neuromuscular junction:

Axon - part of neuron (see chap 4, anatomy of a neuron), carries AP from neuron
Synaptic terminal (AKA: presynaptic knob) - part of neuron, attaches to
             post synaptic membrane
Ca++ enters synaptic terminal
Vesicles with Acetylcholine - in presynaptic knob/neuron  release ACh into cleft
Acetylcholine (ACh) - neurotransmitter - TRANSMITS signal across the cleft to the
             post synaptic membrane
Synaptic cleft - tiny space between end of axon and adjacent cell membrane
Acetylcholinesterase (ACh-ase) - enzyme that breaks down ACh.
Post synaptic membrane - AKA Sarcolemma of muscle cell
Receptors on the post synaptic membrane - binding site for ACh
Local AP created at ligand gated Na+ channels

This part is begins the sliding filament theory and is continued a little farther down on this page

Voltage gated Na+ channels respond to AP created by adjacent ligand gated
         Na+ channels
AP travels through CM, to T-tubules
AP goes down T-tubules into muscle fiber and contacts the Cisternae
Ca++ channels in the cisternae membrane open,
Ca++ diffuses into the cytoplasm (sarcoplasm)

What are the 6 types of proteins in the CM. List them and the function of each.
What are the 2 main types of channels?
What are ligand gated channels and voltage gated channels?
Which type of gated channel are the receptors?

Review the discussion of the Na/K pump in Chapter 4, Tissues.

Remember, the Na/K pump uses ATP to pump 3 Na+ OUT of and 2 K+ into the cell.   This creates and maintains a DIFFERENCE in electrical charge between the extracellular and intracellular fluids - the intracellular is 70mV less than the extracellular fluid.  Now, all the Na+ is OUTSIDE and and wants to diffuse into the cell - if it gets the chance, it will diffuse - it POTENTIALLY will diffuse into the cell.  All the K is INSIDE, and POTENTIALLY will diffuse out of the cell.

Because one side of the CM has a different charge than the other- we say that the CM is POLARIZED (two poles).  (remember, the water molecule is dipolar because it has a different charge on one side of the molecule vs the other side.)

In a cell that is at rest, (NOT stimulated) this maintains the RMP (resting membrane potential).  The cell membrane is impermeable to Na+ and K+ (they are polar molecules) which must pass through channels.  Remember the types of channels:

open - always open
gated.- usually the 'gate' is closed and nothing can pass through
   3 types of gated channels
        ligand gated - a chemical causes the 'gate' to open
        voltage gated - an electrical charge causes the 'gate' to open
        other gated - some condition such as temperature or stretch causes the 'gate' to open

When these gates open - Na+ and K+ POTENTIALLY will diffuse through, until the concentration of each reaches its respective equilibrium -->  0 (zero!) or, equal concentration of Na+ outside and inside; equal concentration of K+ inside and outside.

so... when do the gates open? 
   Ligand gated channels open when the ligand is present
   Voltage gated channels open when the correct 'Potential voltage difference'  exists.
   Other gate:
        Temperature gated channels (other) open when the correct T exists.
         Stretch gated channels (other) open when the CM is stretched.

Describe the RMP, the AP, and the return to RMP.

In a RESTING cell, the CM is polarized at the RMP. 
ACh, the neurotransmitter will cause ligand 'gated' Na+ channels to open and allow Na+ to diffuse into the cell, causing the membrane 'potential' in that region of the CM to decrease (go toward 0).  When the difference in charge drops to -35mV (it is DEPOLARIZED) it creates an AP which stimulates the adjacent VOLTAGE gated Na+ channels to open, allowing Na+ to come in which causes that region of the CM to depolarize.  This opens more adjacent voltage gated Na+ channels, and so on, and so on.  This 'wave' of opening channels, and depolarizations produce an Action Potential that travels along the CM in a domino like effect.

Meanwhile, back at the ligand gated channel, ACh-esterase, breaks down ACh, and the ligand gated Na+ channels close, the voltage gated K+ channels open, K+ diffuse OUT and reestablish the difference in charge - pushing the potential difference toward the RMP - this REPOLARIZES the CM.  When the membrane potential again exceeds -35 mV, the K channels close.  The Na/K pump pumps Na+ out and K+ in to the cell and maintains the RMP.  The wave of opening K+ channels and REPOLARIZING CM follows the wave of AP in a domino like fashion.

NOW, let's look at the whole NeuroMuscular Junction - remember the list from above?
  The function is to stimulate the muscle to contract.  The neuron sends an AP (signal) down the axon, the signal crosses from the end of the axon to the muscle cell, and stimulates the muscle cell to contract.

The AP travels down the axon to the presynaptic knob.  There, the AP opens voltage gated Ca++ channels, and Ca++ enters the presynaptic knob where it causes vesicles filled with ACh to move to the cell membrane and be released into the synaptic cleft.  The ACh diffuses across the cleft, and binds to ACh-receptor molecules on LIGAND gated Na+ channels, causing these channels to open.  Na+ diffuses into the muscle cell, depolarizing the CM and producing an AP right there.  This LOCAL AP opens adjacent voltage gated Na+ channels, Na+ diffuses into the cell at that point, causing a local AP at THAT site, and the AP propagates through the CM in a domino-like wave. 

NOW - to continue the sliding filament theory that started above here on this page.

Remember, the AP travels through the CM in a domino-like wave.  It reaches the T-tubule and goes down it to the cisternae, which is storing Ca++.  Ca++ channels in the cisternae membrane open, Ca++ diffuses out of the cisternae, into the cytoplasm around the sarcomere.  Ca++ binds to troponin, causes it to move the tropomyosin, which uncovers the active sites on the Actin myofilament.

What is another name for the cisternae?
   Sarcoplasmic reticulum.
   What is stored in the sarcoplasmic reticulum?

Once the Active sites are available, the myosin swivel heads attach, swivel, pick up an ATP, then release from the active site and reach for the next active site.

When there is Ca++ in the cytoplasm, the active sites are available... and contraction can occur.  Ca++ uncovers the active sites.

ATP, the useable form of energy, must be present in the cytoplasm so that the myosin swivel heads can release from the active site.  ATP is produced via aerobic cellular respiration.

What is the function of Ca++?
       When do the active sites on Actin become available?
   Where is Ca++ when the muscle is contracting?
   Where is it when the muscle is relaxed?
What is the function of ATP?
   What is ATP and how is it produced?

Notice that Ca++ has two + signs with it ... what does this mean?

Describe the All or Nothing Principle and Graded Strength Principle

A motor unit is neuron and all the muscle fibers that it innervates.  A motor unit can be 1 neuron and 1 muscle cell, or it can be 1 neuron and a few or many muscle cells.  The fewer the cells innervated, the finer the movement produced by a contraction.  Fine motor control is exhibited in the fingers (writing) and iris (pupil diameter).  A large number of cells innervated by a single neuron, produces gross motor movements.   Gross (large) motor control (large muscles produce large movements) is exhibited by the thigh muscles, hip muscles, etc. 

All of None Principle: The arrival of a 'stimulus' at a muscle (entire motor unit) either produces an AP, or it does not.  If the polarization of the CM decreases to -35 mV, an AP is produced and you get a total contraction of the motor unit.  If the stimulus does not reach -35 mV -there is NO response.  If the stimulus reaches -35 mV, you get a TOTAL response.

Graded Strength Principle: Only the number of motor units needed to accomplish a task are stimulated.  For instance - you need fewer motor units to pick up an egg than you need to pick up a 10 kg barbell.  Your body stimulates just enough motor units to pick up the egg without crushing it.  As a baby, while playing with blocks and stacking them, your body 'learns' to recognize and estimate/control the number of motor units needed for each activity. 
Have you ever picked up an empty carton of milk, thinking it was full?
What happened?

 

ATP - energy is transferred from glucose to ATP during aerobic cellular respiration
Creatine-phosphate - another high energy molecule, like ATP, the energy can be easily used.
Cellular respiration - anaerobic and aerobic - transfer energy from storage molecules (glucose
      and fat) to ATP.

What is THE energy molecule that is used exclusively in the body for all chemical reactions and body functions?
    What is ATP?
What is Creatine phosphate?

Review Chapter 3: Cells, and Chapter 17 Nutrition and Metabolism.

What is Cellular respiration?
  What are the two types?

What does anaerobic mean?
  What is the product?
     How much ATP is produced?

What is aerobic cellular respiration?
   What does aerobic mean?
    What are the products of aerobic cellular respiration?
      How much ATP is produced?

What are the 3 steps in aerobic cellular respiration?
  Where does each step occur?

Which type of cellular respiration do humans require? WHY?

What happens when miners get trapped in an airtight chamber of a mine?
   Why don’t they just go ‘anaerobic’ till help arrives?

What mechanism produces ATP?
   Where is the MOST ATP produced?

The agonist muscle is the muscle that is directly causing a movement. 
The antagonist is the muscle that opposes the agonist. 
   When you flex your arm, the bicep is the agonist, and the tricep is the antagonist.
   When you extend your arm, the tricep is the agonist, and the bicep is the antagonist.
Synergist muscles 'help' control the movement. 
In reality, the agonist, antagonist, and synergists all work together to produce a smooth
     controlled movement.

What is an agonist? Antagonist? Synergist?

The ORIGIN is the end of the muscle that does NOT move during contraction.  This is usually the end that is attached to the trunk, or that is proximal (closest) to the midline.
The INSERTION is the end of the muscle that DOES move during contraction.  This is usually the end that is attached to the head, a limb, or is distal (farther) from the midline.

What is the origin of a muscle? The insertion? Give some examples.

How are muscles named?

Shape - deltoid is a triangular muscle

Size - pectoralis major is the biggest pectoral muscle, while p. minor is the smallest

Location - the biceps brachii is found on the upper arm, the biceps femoris is found on the thigh

Orientation -The rectus abdominis and rectus femoris run straight up and down.

Function -  the masseter moves the mandible for chewing

Origin and insertion - sternocleidmastoid - origin is the sternum and clavicle, insertion is the
     mastoid process just behind the ear.

Nervous system is less efficient - cannot generate and transmit APs.
Neurotransmitter is not produced or is nonfunctional.
Muscle cells are lost and not replaced.
 

Remember – all the systems have to work together to maintain homeostasis.

Frontalis
Occipitalis
Orbicularis oculi
Orbicularis oris
Masseter
Sternocleidomastoid
Trapezius
Pectoralis major and minor
Serratus anterior
Latissimus dorsi
Rectus abdominus
External oblique abdominal
Internal oblique abdominal
Transverse abdominal
Diaphragm
Internal intercostals
External intercostals
Erector spinae muscles.
Internal and external anal sphincter

What is the function of a sphincter muscle?

Deltoid
Biceps brachii
Triceps brachii
Flexor muscles of the forearm
Extensor muscles of the forearm

Rectus femoris
Vastus medialis and lateralis
Tensor fascia latae
Gluteus maximus
Gluteus medius
Hamstrings
Biceps femoris
Gracilis
Sartorius
Gastrocnemius
Achilles tendon (calcaneal tendon)
Tibialis anterior