 How many bones and muscles can you name?!
Without using your phone or book, name as many as
possible. The person with the most CORRECT will get
a prize!
 To understand the structure of muscle.
 To explain the components and significance of the
sarcomere.
 To identify the parts of the neuromuscular junction
 To explain how muscle contracts.
 Muscles do work by contracting
 skeletal muscles come in
antagonistic pairs
 flexor vs. extensor
 contracting = shortening
 Tendons (t=two!)
 connect bone to muscle
 ligaments
 connect bone to bone
 Composed of skeletal muscle tissue, nervous tissue,
blood, and connective tissues.
 Fascia: layers of fibrous




connective tissue that
separate an individual
muscle from adjacent
muscles.
Epimysium: tissue closely
surrounding muscle
Perimysium: separates
muscle tissue into small
compartments.
Fascicles: bundles of
skeletal muscle fibers
Endomysium: surrounds
each fiber within a fascicle.
 Muscle Fiber
 muscle cell
 divided into sections = sarcomeres
 Sarcomere
 functional unit of muscle
contraction
 alternating bands of
thin (actin) & thick (myosin)
protein filaments
 Interacting proteins
 thin filaments
 braided strands
 actin
 tropomyosin
 troponin
 thick filaments
 myosin
 Complete the internet investigation to take a closer
look at the sarcomere and discover how muscle
contraction occurs!!
 Complete the Do Now on the “Unit of Muscle
Contraction”
 To determine the role of actin and myosin in muscle
contraction.
 To identify the steps of muscle contraction.
 To explain how the neuromuscular junction works.
 Complex of proteins
 braid of actin molecules & tropomyosin fibers
 tropomyosin fibers secured with troponin molecules
 Single protein
 myosin molecule
 long protein with globular head
bundle of myosin proteins:
globular heads aligned
 A (dark) band- thick and thin filaments
 H zone- region of A band having only thick filaments
 M line- bisects H zone
 I (light) band- thin filaments only
 Z-band- intersects I band; anchors actin filaments
Figure 7-2 b-c
 Myosin tails aligned together & heads pointed away
from center of sarcomere
 Cross bridges
 connections formed between myosin heads (thick
filaments) & actin (thin filaments)
 cause the muscle to shorten (contract)
sarcomere
sarcomere
 Sliding filament theory
 Thin filaments of sarcomere slide toward M line,
alongside thick filaments
 The width of the A band remains the same
 Z lines move closer together
 Place where a motor
neuron meets a muscle
cell
 Action potential travels
down neuron, stimulates
release of acetylcholine
from vesicles, received by
receptors on muscle cell,
action potential is
propogated and
stimulates contraction.
 Muscle Contraction
 Is caused by interactions of thick and thin filaments
 Structures of protein molecules determine interactions
1.
A. Upon stimulation, Ca2+ binds to receptor on
troponin molecule.
B. The troponin–tropomyosin complex changes,
exposing the active site of actin.
2. The myosin head attaches to actin, forming a crossbridge.
The attached myosin head bends/pivots towards
the sarcomere, and ADP and P are released.
4. The cross- bridges detach when the myosin head
binds another ATP molecule.
5. The detached myosin head is reactivated as ATPase
splits the ATP and captures the released energy.
3.
Figure 7-3
*H zone and I bands shorten, NOT A-bands
 Five Steps of the Contraction Cycle
 Exposure of active sites
 Formation of cross-bridges
 Pivoting of myosin heads
 Detachment of cross-bridges
 Reactivation of myosin
Figure 7-5
Figure 7-5
Figure 7-5
Figure 7-5
Figure 7-5
Figure 7-5
1
Put it all together…
2
3
ATP
7
4
6
ATP
5
 Explain what is going on during the contraction of a
sarcomere.
 Read the beginning of the lab as well as the intro’s to
the different activities and answer the following
questions:






Explain motor unit summation.
What is a single contraction of skeletal muscle called?
What are the 3 phases of this?
What is the different between active and passive force?
What is “treppe”?
What is “tetanus”? What causes it? Why must you get a
tetanus shot?
 To further understand muscle contraction.
 To observe muscle response to increased stimulus
intensity.
 To observe treppe, wave summation, and tetanus.
 To compare and contrast isometric vs. isotonic
contraction.
 PhysioEx Excersize 2
 After answering the questions in the Do Now, begin the
experiment on the physioEx disc on our NEW
LAPTOPS!! WOOHOO!!!
 The other packet is to help you understand some of the
terms they go through in the lab.
 You will have today AND tomorrow to work on this and
should answer the questions in BOTH packets.
 Quiz on sarcomere structure and muscle contraction on
FRIDAY!
 The all-or-none principle
 As a whole, a muscle fiber either contracts completely or
does not contract at all
 Recruitment (multiple motor unit summation)
 In a whole muscle or group of muscles, increasing tension
is produced by slowly increasing the size or number of
motor units stimulated
Figure 7-8
 Muscle tone
 The normal tension and firmness of a muscle at rest
 Muscle units actively maintain body position, without
motion
 Increasing muscle tone increases metabolic energy used,
even at rest
 Sustained muscle contraction uses a lot of ATP energy
 Muscles store enough energy to start contraction
 Muscle fibers must manufacture more ATP as needed
 When muscles can no longer perform a required
activity, they are fatigued
 Results of Muscle Fatigue
 Muscle exhaustion and pain
 Lack of blood supply
 Depletion of glucose and glycogen
 Damage to sarcolemma and sarcoplasmic reticulum
 Low pH (lactic acid)
 Oxygen debt:
 After exercise or other exertion the body needs more oxygen
than usual to normalize metabolic activities
 Muscle Hypertrophy
 Muscle growth from heavy training:
 Increases diameter of muscle fibers
 Increases number of myofibrils
 Increases mitochondria, glycogen reserves
 Muscle Atrophy
 Lack of muscle activity:
 Reduces muscle size, tone, and power
 Fibers decrease in size and become weaker
 *this can happen to people while they
 Primary Action Categories
 Prime mover (agonist):
 Main muscle in an action
 Synergist:
 Helper muscle in an action
 Antagonist:
 Opposed muscle to an action
-Take out your physioEx Labs.
-Complete the worksheet using your physioEx lab if
necessary.
 To identify the graphs of different types of muscle
contraction.
 To identify the different types of bones.
 To classify bones based on shape.
 To identify different features of bones.
 Complete the checklist you were given.
 Fill in “M” if it is a muscle and “B” if it is a bone or a
feature of a bone.
 CIRCLE the muscles/bones that you are still unfamiliar
with. Make sure you focus on these today!
 To identify the bones of the skull as well as the
different features found within the skull.
 To identify the muscles of the head and be able to
explain what movement they are responsible for.
 To locate the muscles and bones in the head of a sheep
through dissection.
 EVERYBODY STAND UP!!!
 Labeling
 The Anterior view of the skull 1
 The anterior view of the skull 2
 Side view skull
 Superior view of skull
 Muscles of Facial Expression (note: you do not need to
know all of these but it is good practice)
* Another good website to explore at home…
 Purpose:
 Compare/contrast the
sheep skull with a human
skull.
 Review knowledge of
tissues.
 Identify as many
structures as possible.
 What are some main
differences in the sheep
skull that you don’t see in
the human skull? Why
might they be better
suited for a sheep?
 What tissues are you able
to see in the specimen?
 If you remove the muscle
tissue, what bones are you
able to identify?
 Take a look back at the worksheet you completed for
the Do Now Activity… are you able to fill in more of it?