4.1 Joints and Muscles

What would life be like without Joints Move a joint that you use often How do different joints move

Essential Question 1. What role do joints play in the human body? Joints are the places where two bones meet and allow movement & flexibility and provides support to the human skeleton. 2. How are joints classified by both structure and function? Functionally, joints are classified by how much motion they allow. Structurally, joints are classified as fibrous, cartilaginous, or synovial.

Joint Classification Immovable/Fibrous Do not move—EX: joints in dome of skull and between teeth and jawbone Partially Moveable/Cartilaginous Move little—linked by cartilage—EX: vertebrae in spine Immovable joints and slightly movable joints are restricted mainly to the axial skeleton where protection and stability are key

Joint Classification Freely Moveable/Synovial Move in many directions— found at the hip, shoulders, elbows, knees, wrists, and ankles —filled with synovial fluid (acts as lubricant)—these joints have synovial cavities Freely movable joints are found on the appendicular skeleton and permit flexibility in the limbs.

Activity 4.1.1 Bones, Joints, Action! Obtain a body system graphic organizer (skeletal view) Research the six main types of synovial joints Complete activity through question 6

Essential Question 3. What are the different types of synovial joints? Pivot joint Ball-and-Socket joint Saddle joint Condyloid (Ellipsoidal) joint Hinge joint Plane (Planar or Gliding) joint

Types of Synovial Joints

Types of Synovial Joints

Activity 4.1.1 Bones, Joints, Action! http://www.youtube.com/watch?v=9fZkne0GE9g- cow elbow dissection Create groups of 3 or 4 Obtain Gloves, Goggles and Cow Elbow Look for the movement of the joint, cartilage, tendons and ligaments Complete the rest of Activity 4.1.1 and Conclusion Questions

Dissected Cow Elbow

Activity 4.1.1 Bones, Joints, Action! How are cow elbows and human elbows similar and different? In the cow joint, the ulna and the radius are fused; whereas in the human, they are two separate bones Human elbow joint allows for rotation and overall dexterity (not needed by the cow) What type of synovial joint was modeled by cow elbow?

Connective Tissue Connective tissue protects, supports, and binds together other body tissues. Connective tissue is made up of different types of cells in varying amounts of a nonliving substance around the cells, called the matrix. Fibrous connective tissue which is found in tendons and ligaments. Fibrous connective tissue is composed of large amounts of closely packed collagenous fibers. Cartilage is a form of fibrous connective tissue that is composed of closely packed collagenous fibers in a rubbery gelatinous substance called chondrin. 

Essential Question 4. What role do cartilage, tendons, and ligaments play at a joint? Cartilage - Cushions/protects bones where they meet and rub against each other. The cartilage found in joints is hyaline cartilage—the same kind found in a fetal skeleton & it’s referred to as articular cartilage where it attaches to articular bone surfaces. Tendons - Fibrous tissue that connects muscles to bones Ligaments -Fibrous straps that fasten bones to other bones

Motion with the Cow Elbow How did your cow elbow move? Think about the type of synovial joint How do human elbows move?

What makes our bodies flexible? Flexibility What makes our bodies flexible? Joints

Joints Joints with a large range of motion has limited stability Joint with limited mobility, such as the sutures in the skull, have great stability Move your hip and shoulder and describe the range of motion of each joint Joints make up for a lack of stability by the addition of muscle Joints that are very stable and produce little movement are assisted by limited amounts of muscle Joints that are very flexible, but offer little stability are surrounded by large amounts of muscle

Describing Motion How do we describe the motions of a joint ? Bending Flexing Scientists and medical professionals use precise terms to describe the direction of motion as well as the relationship of one body part to another Depression and Elevation (Make this Motion)

Elevation and Depression Movement Elevation Depression

Activity 4.1.2: Range of Motion In groups of 3 research the following Terms and Document on your Body Organizers (Complete Steps 1 & 2) Depression and elevation Rotation and circumduction Flexion and extension (and hyperextension) Abduction and adduction Plantar flexion and dorsiflexion When you know all the Motion as a group demonstrate them to your teacher

Essential Question 5. What terms describe the path of movement at a joint?

Essential Question 6. What is range of motion? Range of motion is the range through which a joint can be moved & can be measured using a goniometer to determine angles.

Essential Question 7. How do you measure the range of motion of a particular joint movement? Each specific joint has a normal range of motion that is expressed in degrees. Devices to measure range of motion in the joints of the body include the goniometer and inclinometer which use a stationary arm, protractor, fulcrum, and movement arm to measure angle from axis of the joint. As measurement results will vary by the degree of resistance, two levels of range of motion results are recorded in most cases.

Normal ROM for Joints in Adults

Finish Activity 4.1.2: Range of Motion You will need Activity 4.1.2 Range of Motion Activity 4.1.2 Student Resource Sheet - ROM ROM Schematics Goniometer http://www.youtube.com/watch?feature=player_embedded&v=ZUF7tpkVAIY- or http://www.youtube.com/watch?v=J_R-igYFj98&feature=player_embedded Instructions on how to use a goniometer

Key Terms

Essential Question 8. How do bones, muscles and joints work together to enable movement and locomotion for the human body? Our bones provide support and give our bodies shape, but cannot move on their own. The muscles provide the movement. The joints help attach bones to one another to provide flexibility & allow the muscles to help give the bones a way to move.

Lesson 4.2 Muscles

Essential Question 1. How do muscles assist with movement of the body and of substances around the body? Our muscles are what allow all movement of our bodies (and within our bodies). They help us involuntarily by helping food move down the esophagus and into the stomach (peristalsis) and helping blood move through our bodies (the heart is a muscle). They also help us move our bodies voluntarily from place to place (the muscles in our limbs). Our bodies each have about 650 muscles & are ~ 50% muscle by weight!

Activity 4.2.1 Muscle Rules Part 1 With a partner research the following 3 muscle tissues skeletal muscle smooth muscle cardiac muscle Create this table in your Journal View prepared slides Complete Part 1 only

Essential Question 2. How do the structure and function of the three types of muscle tissue compare? Cardiac - They are striated muscle fibers form the wall of the heart & function involuntarily. Skeletal -They are attached to bone, mostly in the legs, arms, abdomen, chest, neck and face. They are striated muscle fibers (lined under microscope) & attach to bone by a tendon. They hold the skeleton together and give the body shape. They are voluntary (we control them) and contract quickly and powerfully), but they tire easily. Smooth -They are smooth (not striated) & are controlled automatically by our nervous system. They are also called ―involuntary‖ muscles. They make up the walls of the stomach and intestine to help break down and move food. They also line the walls of blood vessels. They take longer to contract than skeletal muscles, but also don’t tire as easily.

Skeletal Muscle Voluntary – we control the movement Striated – looks like long fibers Linked to bones by tendons Function – to help us move / move our bones

Smooth Muscle Involuntary Action – controlled by our CNS Non-striated Found in arteries, veins, intestines, etc. Function : Maintain organ dimensions – stretch and recoil

Cardiac Muscle Involuntary Striated – but, may be branched which is unlike skeletal muscle. Found in walls of the heart Function : To pump the heart! Highly resistant to fatigue w/lots of mitochondria

Let’s Start By Building a Muscle from Spaghetti Activity 4.2.1 Muscle Rules Part 2 Let’s Start By Building a Muscle from Spaghetti Pick up one piece of spaghetti. Each piece of spaghetti will represent one skeletal muscle cell or fiber Each muscle fiber is enclosed by a delicate membrane called the endomysium. (For the purposes of this activity, the yellow outer coating of the spaghetti represents this membrane.)

Spaghetti Muscle Cont’d Pick up a handful of spaghetti. This bundle of fibers represents a fascicle. Each fascicle, however, is covered by a membrane called the perimysium. Place the bunch of spaghetti on the end of a piece of plastic wrap. Roll the spaghetti up in the plastic used to represent the perimysium. Hold up the completed fascicle. Pull the ends taut, and notice that this tissue has little to no bumps. These ends represent dense regular connective tissue.

Spaghetti Muscle Cont’d Fascicles group together to form a skeletal muscle. Combine your fascicle w/ three other pairs’ to form a whole muscle. These fascicles are bound together by an even tougher outer membrane called the epimysium. Wrap the combined fascicles in another piece of plastic wrap. This layer of wrap will represent the epimysium. Twist the plastic wrap on each end of the completed muscle. At the ends of the muscle, the epimysia blend together to form tendons, cordlike structures that attach muscle to bone, cartilage or other connective tissue.

Essential Question 3. How are muscle fibers and membranes organized to form a whole skeletal muscle? The epimysium (“upon muscle”) is the outermost layer of connective tissue. The perimysium (“around muscle”) is made of connective tissue and forms casings for bundles of muscle fibers. The endomysium (“within muscle‖) is connective tissue surrounding each individual muscle fiber. Each fascicle is a small cluster of muscle fibers, with endomysium between the individual fibers. Blood vessels run between the fascicles, bringing the tissue nutrients & removing waste. Nerves also run throughout, controlling the movement of the muscles. Together, the network of nerves and blood vessels are referred to as the plexus

Activity 4.2.1 Muscle Rules Part 3 Will need your Manikins Clay Lab Journals We will create a muscle together

Step 1 Locate the ventral side and use a pencil to place a dot on the lateral and medial side of the radial groove (about halfway up the humerus).

Step 2 Locate the ulna just below the fold of the elbow. Help the students see the hollowed out area in the antecubital region. Place a pencil dot above this area.

Step 2 Cont’d - Rule 1 These dots each represent an attachment point for a muscle. Note that there are at least two attachments (in this case three) and the muscle will cross a joint at the elbow. This leads us to Muscle Rule #1: Muscles must have at least two attachments and must cross at least one joint.

Step 3 – Brachialis Muscle Using terra cotta clay, form two balls about the diameter of a nickel. Rolling the clay between the tabletop and a palm, roll each ball into a long carrot. The total length of the carrots should stretch from the humeral attachment to the ulnar attachment. Bring the fat part of the carrots together, leaving the tops free (rabbit ears).

Muscles always “pull” and get shorter. Step 4 – Rule 2 Using your left thumb to represent the humeral attachments and your left middle finger to represent the ulnar attachment, place the left hand on the right arm where the attachments would be. Make sure to cross the joint. Pull your forearm towards your heart and watch the position of your fingers. You should notice that your index finger and thumb are closer together than when you started. This lead to rule 2: Muscles always “pull” and get shorter.

Step 5 – Rule 3 Repeat the motion and identify which attachment is “pulling” or moving closer to the other attachment. The attachment that moves is known as the insertion of the muscle. The insertion is usually the distal attachment. The attachment that does not move and pulls the other attachment toward it is referred to as the origin. The origin is usually the proximal attachment. This leads to Rule 3: The attachment that moves is known as the insertion and the attachment that remains stationary is known as the origin.

Step 6 Extend your arms out in front of their bodies. Notice this angle is 180°. Show the movement again of the muscle you have just built. This time pay attention to what happens to this angle when the muscle shortens. Notice that the angle decreases. Do you remember what we call motion at a joint that decreases the angle between articulating bones? Flexion and thus a muscle such as this is referred to as a flexor.

Step 7 – Rule 4 Flex your arms one more time, but stop at the end of the movement. If muscles only pull, then how can the arm be straightened? What do we call motion at a joint that increases the angle between articulating bones? Extension and thus a muscle that controls this movement is referred to as an extensor. Muscles that decrease the angle between ventral surfaces of the body are known as flexors. Muscles that increase the angle between ventral surfaces of the body are known as extensors

Step 8 Place a pencil dot halfway up the dorsal side of the humerus. Place another dot just distal of the elbow onto the ulna

Step 9 –triceps medial head Using terra cotta clay, form a ball the diameter of a nickel. Roll the ball into an even tube. Attach the ends of the clay tube to dots on the humerus and on the ulna. Since the back of the humerus is flat, the muscle shapes to the bone and is also flat. Use your thumbs to flatten the clay. Remove any clay that makes its way to the ventral side.

Step 9 Cont’d Act out the action of this muscle. With the right arm in the flexed position, place the left thumb on the back of the humerus and the left index finger on the back of the elbow. “Pull” with your index fingers and the angle should increase to 180°. Repeat the motion and think of Rules 2, 3 and 4. Since the angle in this motion increases, the muscle is an extensor.

The Triceps Origin = proximal half of dorsal humerus Insertion = distal of elbow on the ulna Action = extends elbow

Muscles work in opposing pairs. Flexors and Extensors Flexors are on the ventral side of the body and extensors are located dorsally. “For smooth movements to occur, can both extensors and flexors be contracting at the same time?” When the flexors are pulling, the extensors are relaxing. This brings us to Rule #5: Muscles work in opposing pairs.

Rule # 6 Muscle striations point to the attachments and show the direction of pull.

Naming Muscles Each muscle is given a Latin name based on one or more of its features Take a look at the following muscle names and brainstorm what you can tell about these muscles simply by their names Trapezius and Rhomboid minor Gluteus maximus and Gluteus minimus Frontalis and Temporalis Orbicularis Oculi and Transverse abdominis Flexor Carpi Ulnaris and Extensor digitorum longus SternoCleidomastoid and Brachioradialis Biceps Brachii and Triceps Brachii

Essential Question 4. What do skeletal muscle structure and attachment to bones tell you about function? Muscles each have an insertion, where they attach to the moveable bone and an origin, where they attach to the stationary bone.

Essential Question 5. How are muscles named? Several factors are considered when naming a muscle, including 1) Location (EX: tibialis anterior is on the front of the tibia) 2) Shape (EX: deltoid ―resembles‖ (- oid ) a ―triangle‖ ( delt )) 3) Points of attachment (EX: sternocleidomastoid—the muscle attaches to the sternum and the tendons attach to the mastoid process of the skull.) 4) Relative size (EX: gluteal or ―rump‖ region – the gluteus maximus is bigger and the gluteus minimus smaller). 5) Number of muscle ―heads‖ or divisions (EX: Biceps means ―two-headed‖ and has two divisions) 6) Direction of muscle fibers (EX: the rectus abdominis muscle is located in the front of the abdomen and its fibers are oriented in a ―straight‖ (rect), vertical direction). 7): Association with characters (EX: sartorius means ―presence of‖ (-us) a ―tailor‖ (sartori )! Tailors used to sit cross-legged upon the ground. The sartorius is actually located along the inner aspect of each thigh. Thus, when it contracts, it flexes (bends) the lower leg like an ancient tailor.

Activity 4.2.2: Building a Better Body

HBS - A.4.2.2 How to Build a Better Body Please grab your maniken and a tool kit and sit with your partner! Use the wrench to take the arm off your Maniken. DO NOT LOSE THE SCREWS!

Muscle #1: Intercostals We will build the external intercostals of the chest. These muscles are found in between the ribs and extend from the front of the ribs, around back and past the bend in the bones. Describe the function of the muscles that are found between the ribs. These muscles help move air in and out of the chest. When you eat ribs, you are actually eating the intercostal muscles between the bones, not the ribs themselves.   Place a strand of spaghetti between each rib, starting at the back of the rib where it attaches to the vertebral column, all the way around to the rib’s attachment at the sternum.   Use your thumb or one of the clay tools to flatten down these strands. The intercostal muscles do not stick out of the chest.

Muscle #2 – Serratus Anterior Attach the stand-off to the torso. The indentation in the stand-off should face the midline of the model. Do not yet tighten the screws completely. The Maniken® displays vertical dashes midway around the ribs to indicate where the bone becomes cartilage. Origin = lateral surface of ribs 1-8 (bone only) Insertion = medial border of the scapula

Muscle #2 – Serratus Anterior Take small pieces of spaghetti and attach these strands from the medial side of each rib (where the dashes are shown) to the stand-off on the arm. Attach one strand from each of ribs 1-8 to form a saw-like structure – a “serrated” edge. This muscle helps move the scapula forward and is often used at the end of big movements such as a bench press, a baseball pitch, or a swimming stroke. Attach the arm of your Maniken®. The screws should thread in as easily as they unthreaded on removal.

Muscle #3- Pectoralis Minor Where are the origin and insertion of the pectoralis minor? Origin = anterior surface of ribs 3 – 5 (just past the origins of the serratus anterior) Insertion = coracoid process of the scapula (piece of the scapula visible on the front) Use spaghetti strands to form the pectoralis minor. Place one small strand at the origin of each rib and run these three strands together as they attach at the scapula. The muscle is built in a manner similar to the serratus anterior. Act out the movement of this muscle. This muscle works to rotate the shoulder forward.

Muscle #4 – Pectoralis Major Even though this muscle only has one name, there are actually three different “heads” or pieces to this muscle. Each part will be built separately and will be formed from a carrot-shaped tube that has been rolled flat. Keep these muscles thick and striate each muscle as it is built. Have students first construct the abdominal head of the pectoralis major. Given the name only, ask students where they think this muscle might attach. What are the origin and insertion of the abdominal head of the pectoralis major? Origin = ribs 5-7 (actually attaches to fascia of abdominal muscles) Insertion = lateral edge of the most proximal part of the humerus Make a long carrot out of terra cotta clay. Flatten the carrot slightly to make a tongue.

Muscle #4 – Pectoralis Major Gently lay the muscle across the chest of the Maniken® from the origin to the insertion. The long end of the carrot should point towards the shoulder and the wide end should run down towards the 5th through 7th rib. The muscle will have a teardrop shape. Keep the insertion very narrow and the origin much wider. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®. Use the wire tool or a pencil to carefully outline the shape of the muscle and trim off any jagged edges. Take the muscle off the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment. Attach the muscle to the model. Ask students to striate the muscle. Remember that the striations of the muscle indicate the direction the muscle moves.

Pectoralis Major Act out the motion of this portion of the pectoralis Which sports or exercises utilize this muscle? Tennis serve or a volleyball spike. We will now create the largest portion of the muscle – the sternal or sternocostalis head. Where do you think this muscle might attach. Origin = ribs 1-5 on the lateral edge of the sternum (no clay should be on the sternum) Insertion = lateral edge of the humerus, inferior to the insertion of the abdominal head. Make a short, fat carrot out of terra cotta clay. Flatten the carrot slightly to make a thick triangle. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®.

Pectoralis Major Gently lay the muscle across the chest of the model from the origin to the insertion. The long end of the carrot should point towards the humerus and the wide end should run along the lateral edge of the sternum. The origin of this muscle will overlap the origin of the abdominal head. Use the wire tool or a pencil to carefully outline the shape of the muscle. Take the muscle off of the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment. Make sure no clay extends over the sternum. Attach the muscle to the Maniken®. Ask students to striate the muscle. Remember that the striations of the muscle indicate the direction it moves.

Pectoralis Major Ask students to act out the motion of this portion of the pectoralis major. Which sports or exercises utilize this muscle? This muscle adducts the arm across the chest and is at the route of a tennis forehand shot. The butterfly machine in the gym allows a person to isolate and train this portion of the muscle. Create the smallest portion of the muscle – the clavicular head. What are the origin and insertion of the clavicular head of the pectoralis major? Origin = medial half of inferior edge of the clavicle Insertion = lateral edge of the proximal humerus, inferior to the insertion of the sternal head

Pectoralis Major Make a small carrot out of terra cotta clay. Flatten the carrot slightly to make a shape similar to an isosceles triangle. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®. Gently lay the muscle across the chest of the model from the origin to the insertion. The long end of the carrot should point towards the humerus and the slightly wider end should run up against the bottom of the clavicle. The insertion of this muscle will cross over the insertion of the other two muscles on its way to the humeral attachment. 

Pectoralis Major Use the wire tool or a pencil to carefully outline the shape of the muscle.   Take the muscle off the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment.   Attach the muscle to the Maniken®. Striate the muscle. Remember that the striations of the muscle indicate the direction it moves.

Building Muscles Thinking about the muscles we built, why would one exercise not tone all of the muscles.

Essential Question 6. What are the requirements for muscle contraction? Calcium and ATP are cofactors required for the contraction of muscle cells. ATP supplies the energy Calcium is required by two proteins that regulate muscle contraction by blocking the binding of myosin to filamentous actin Troponin Tropomyosin In a resting sarcomere, tropomyosin blocks the binding of myosin to actin

Essential Question 7. What role do calcium and ATP play in muscle contraction? 1) Calcium ions cause troponin and tropomyosin to shift, exposing myosin binding sites 2) Myosin heads connect with actin binding sites & move the thin filament, contracting the muscle 3) The ADP & P that caused the myosin heads to cock back are left behind during the power stroke 4) Introduction of ATP causes myosin heads to release the actin 5) ATP is broken down into ADP & P, causing myosin heads to cock back and prepare for another power stroke

Muscle Contraction http://www.youtube.com/watch?v=hqynCsign8E- Video discussing muscle contraction

Activity 4.2.4 Laws of Contraction Pair up You will need: Disposable transfer pipettes (1ml) 5 Test tubes 5 Micorscopic slides Laboratory journal Salt solution, no ATP Teasing needles (from dissection kits) or straight pins 0.25% ATP in distilled water 0.25% ATP in salt solution Forceps or tweezers Millimeter ruler 0.10% ATP in salt solution Microscope Frog Muscle 0.05% ATP in salt solution

Essential Question 8. What is a sarcomere? The contractile unit of a myofibril; sarcomeres are repeating structural units of striated muscle fibrils, delimited by the Z bands along the length of the myofibril. 9. How does a sarcomere contract and lengthen to cause muscle contraction?

Muscle Contraction-Sacomere

Molecular Muscle Movement Muscle filaments are called myofibrils. Myofibrils are made up of two kinds of filament: Thin filaments made of actin protein Thick filaments made of myosin protein. Actin and myosin filaments work together to make muscles contract. These fibers are located between protein sheets called Z-discs

Muscle Contraction Actin and myosin are layered. Myosin filaments have hooked parts that will stretch and pull themselves along the actin filaments when ATP attaches to them.

Muscle Filament Contraction

Muscle Filament Relaxation Calcium (Ca2+) must be removed for the muscle fibers to relax Moving (Ca2+) back into the sarcoplasmic reticulum is ACTIVE TRANSPORT (requires ATP) If the muscle cannot remove the (Ca2+) the muscle cannot relax and will stay contracted.

Rigor Mortis

Rigor Mortis How is the condition rigor mortis related to muscle contraction? After death actin and myosin shorten muscle fibers. ATP is needed to release the myosin heads from the actin fibers and allow muscles to relax, but ATP reserves are quickly depleted, causing muscles to remain contracted. It can take 10 minutes to hours to occur, with maximum stiffness 12-24 hours after death. Eventually tissue decays and lysosomal enzymes leak and cause muscles to relax.

Essential Question 11. How do nerves interact with muscles? In order for muscles to contract (shorten and thicken), they must receive a message from the CNS to do so. The messages come through efferent neurons (nerves that move away from the CNS). Afferent neurons send messages back from muscles to the CNS. If there are problems with nerves, it can lead to issues with muscle function (i.e. Carpal Tunnel Syndrome)

Activity 4.2.6: You’ve Got Nerve Building Nerves Part 1 Brachial Plexus and Radial Nerve

Activity 4.2.6: You’ve Got Nerve Part 2 Carpal Tunnel Carpal tunnel syndrome is related to pinching of the medial nerve. How can repetitive movement cause damage. Complete Part 2

Essential Question 12. How can we assess muscle function? Heart rate can help assess cardiac muscle function. Strength tests can help assess function of voluntary muscles. What equipment and testing have we used that could be used on muscles. Labview EMG data

Key Terms Actin -A contractile protein that is part of the thin filaments in muscle fibers Afferent neurons-Nerve cells that carry impulses towards the central nervous system Cardiac muscle- Striated muscle fibers (cells) that form the wall of the heart; stimulated by the intrinsic conduction system and autonomic motor neurons Carpal tunnel syndrome-A condition caused by compression of the median nerve in the carpal tunnel and characterized especially by weakness, pain, and disturbances of sensation in the hand and fingers Contract -To shorten and thicken

Key Terms Efferent neurons- Nerve cells that conduct impulses away from the central nervous system Endomysium - The delicate connective tissue surrounding the individual muscular fibers within the smallest bundles Epimysium - The external connective-tissue sheath of a muscle Fascicle - A small bundle or cluster, especially of nerve or muscle fibers Insertion - The attachment of a muscle tendon to a moveable bone or the end opposite the origin Muscle - An organ composed of one of the three types of muscular tissue (skeletal, cardiac, and smooth), specialized for contraction to produce voluntary and involuntary movements of parts of the body

Key Terms Myofibril - A threadlike structure, extending longitudinally through a muscle fiber (cell) consisting mainly of think filaments (myosin) and thin filaments (actin, troponin, and tropomyosin) Myosin- The contractile protein that makes up the thick filaments of muscle fibers Nerve- A cordlike bundle of neuronal axons and/or dendrites and associated connective tissue coursing together outside the central nervous system Origin - The attachment of a muscle tendon to a stationary bone or the end opposite the insertion Perimysium-The connective-tissue sheath that surrounds a muscle and forms sheaths for the bundles of muscle fibers

Key Terms Plexus- Network of interlacing blood vessels or nerves Rigor mortis-Temporary rigidity of muscles occurring after death Sarcomere- Any of the repeating structural units of striated muscle fibrils Skeletal muscle- An organ specialized for contraction, composed of striated muscle fibers (cells), supported by connective tissue, attached to bone by a tendon or aponeurosis, and stimulated by somatic motor neurons Sliding filament mechanism-The explanation of how thick and thin filaments slide relative to one another during striated muscle contraction to decrease sarcomere length Smooth muscle- A tissue specialized for contraction, composed of smooth muscle fibers (cells), located in the walls of hollow internal organs, and innervated by the autonomic motor neurons

Key Terms Striation- Any of the alternate dark and light cross bands of a myofibril of striated muscle Tropomyosin - A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction Troponin - A protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction