Transcript of Assignment 1: Structure and Function of the Skeletal System
Principles of Anatomy and Physiology:
1.1 Structure of the Skeletal System
P1: To describe the structure and function of the skeletal system
To know all three classifications of joint and the movement available at each
P2: To describe the different classifications of joints
P1: Structure of the skeletal system
The skeletal system is made up of:
The function of the skeletal system is to provide:
Joints are also important, giving you the freedom to flex or rotate parts of your body. However this gets harder with age, as your bones lose their strength and density.
The human body is made up of 206 bones, which are divided into two groups: 80 form your axial skelton; the other 126 form your appendicular skelton.
P1: Bones of the Human Skeleton
Label the bones of the human skeleton.
P1: Axial Skeleton
The axial skeleton forms the main axis or core of your skeletal system, it is made up of 80 bones and consists of the:
Skull (cranium andd facial bones)
Thorax (sternum and ribs)
Task: colour in the axial section of the skeleton
Task: Label the axial skeleton
P1: Appendicular Skeleton
The appendicular skeleton consists of the shoulder and the pelvic girdle
The shoulder girdle consists of four bones which connect the limbs of the upper body to the thorax
The upper limbs consist of 60 bones. Each upper limb is made up of:
P1: Appendicular Skeleton
The pelvic girdles main function is to provide a solid base through which to transmit the weight of the upper body and protect the digestive and reproductive organs. The pelvic girdle consists of three bones:
The lower limbs consist of 60 bones. Each lower limb is made up of:
The principle function of the pelvic girdle is to provide a solid base through which to transmit the weight of the upper body. It also provides attachment for muscles of the lower back and legs, and protects the digestive and reproductive organs.
P1: Appendicular Skeleton
P1: Types of major bone
Task: Watch the following video and answer the questions
P1: Types of major bone
Bones vary in shape and size according to their location and function. They are classified as follows:
• Long bones
• Short bones
• Flat bones
• Sesamoid bones
• Irregular bones
are found in the limbs such as the femur, tibia, and fibula. They have a shaft known as the diaphysis and two expanded ends known as the epiphysis.
are small, light, strong, cubed shaped bones. The carpals and tarsals are of the wrists and ankles are examples of short bones.
P1: Types of major bone
have a specialised function. They are usually found within a tendon such as the patella in the knee.
have complex shapes that for none of the above categories. The bones of the spine are a good example.
are thin, flattened and slightly curved, and have a large surface area, examples include the scapula, sternum, and cranium.
Write the following term into your workbooks:
Anterior: To the front or in front
Posterior: To the rear of behind
Medial: Towards the midline
Lateral: Away from the midline
Proximal: Near to the root or orgian
Distal: Away from the root or orgian
P1: Vertebral Column
The vertebrae column has many functions. It protects the spinal cord and supports the ribcage. The larger vertebrae of the lumbar region support a large amount of body weight. The flatter thoracic vertebrae offer attachment for the large muscles of the back and the curves of the spine – four in all. These, along with the intevertebral discs, receive and distribute impact associated with the dynamic functioning of the body in action, reducing shock.
The vertebrae can be classified as:
Cervical vertebrae (in the neck)
Thoracic vertebrae (in the chest region)
Lumbar vertebrae (in the small of the back)
Sacral vertebrae (fused vertebrae that form the sacrum)
Coccygeal vertebrae (fuses vertebrae that form the coccyx)
Label the vertebrae column:
Using the image in your books label the anatomical positions.
Principles of Anatomy and Physiology:
1.2 Function of the skeletal system
To know the function of the skeletal system
Support: Your bones give your body shape and provide a frame work for the soft tissues of your body.
Protection: Your skeleton protects vital tissues and organs in your body e.g. cranium (brain),rib cage (lungs), vertebrae (spinal column) .
Movement: Parts of your skeleton provide a surface for your skeletal muscles to attach to, allowing you to move. Muscles pulling on bones act as leavers and movement occurs at joints so you can walk, run, jump etc.
Blood cell production: Blood vessels feed the centre of your bones and stored within them is bone marrow. Blood cell production in prevalent in long bones e.g. femur, fibula and tibula.
Store minerals: None is a reservoir for minerals such as calcium and phosphorus, essential for bone growth and the maintenance of bone health.
P2: Joint Classification
A joint is formed where two or more bones meet. The function of a joint is to hold bones together and allow movement.
There are three classifications of joints:
Fixed / immovable (fibrous)
Slightly movable (cartilaginous)
Freely moveable (synovial)
Are also known as fibrous or immovable joints, they do not move. They interlock and overlap and are held together by bands of tough fibrous tissue e.g. the plates in your cranium.
These joints allow slight movement. The ends of the bone are covered in articular or hyaline cartilage that reduces friction. Slight movement at these articulating surfaces is made possible because the pads of cartilage compress e.g. between most vertebrae.
P2: Joint Classification
P1: Vertebrae Column
Cervical: the vertebrae of the neck. The first two are known as atlas (C1) and axis (C2). They form a pivot that allows the head and neck to move freely. There are 7 vertebrae in this area (C1-C7)
Thoracic: the vertebrae of the mid spine, which articulate with the ribs. The thoracic section has12 vertebrae (T1-T12).
Lumbar: the largest of the moveable vertebrae, situated in the lower back. They support more weight than other vertebrae and provide attachment for many of the muscle in the lower back. The lumber has 5 vertebrae (L1-L5).
Sacrum: Five sacral vertebrae are fused to form the sacrum, a triangular bone located below the lumber vertebrae. It forms the back wall of the pelvic girdle, sitting between tow hip bones.
Coccyx: at the bottom of the vertebral column there are four coccygeal vertebrae, which are fused to form the coccyx or tail bone.
Synovial joints / freely moveable
joints offer the highest level of mobility at a joint. These joints make up most of the joints of your limbs. They are surrounded by a
, lined with a
When movement occurs the synovial membrane secretes a fluid known as
into the joint cavity to lubricate and nourish the joint. The synovial fluid acts like a buffer between articulating bones to prevent injury. The
is held together by though bands of connective tissue known as
. This provides the strength to avoid dislocation, while being flexible enough to allow movement.
The characteristics of a synovial joint are:
An outer sleeve or joint capsule to help to hold the bones in place and protect the joint
A synovial membrane, secreting synovial fluid to lubricate the joint
A joint cavity - the cap between the articulating bones
Articular cartilage on the ends of the bones to provide a smooth and slippery covering to stop the bones knocking or grinding together
Ligaments to hold the bones together
P2: Types of Synovial Joints
Hinge - Allows movement in one direction e.g. flexion/extension at the knee/elbow joint - kicking a football.
Ball and socket - The round end of one bone fits into a cup shaped socket in the other bone, allowing movement in all directions e.g. Flexion/Extension/Adduction/Abduction/Internal & External Rotation at the hip and shoulder joint - front crawl
Condyloid/Ellipsoid - Movement is backwards and forwards and from side to side e.g. Flexion/Extension/Adduction/ Abduction/Circumduction at the wrist joint (intercarple) - dribbling in basketball
P2: Types of Synovial Joints
Gliding - These joints allow movement over a flat surface in all directions, but this is restricted by ligaments e.g. carpels and tarsals - dribbling the ball in hockey by moving the hockey stick over and back.
Pivot - A ring of one bone fits over a peg of another, allowing controlled rotational movement, such as the joint of the atlas and axis in the neck e.g bilateral breathing in swimming
Saddle - Movement occurs backwards and forwards and from side to side, like that at the base of the thumb e.g. flexion/Extension/Adduction/Abduction/Circumduction e.g. holding a tennis racket or golf club.
P2: Types of movement
reducing the angle at the joint e.g. bicep curl
increasing the angle at a join e.g. straightening your arm to return to your starting position of the bicep curl
movement away from the midline of the body e.g. side step in gymnastics
: movement towards the midline of the body e.g. pulling the oars whilst rowing
circular movement of the limb e.g. occurs at the shoulder joint during a serve in tennis
an inward rotation of the forearms so the palm of the wrist is facing backwards and downwards e.g. table tennis forehand top spin
an outward rotation of the forearm so that the palm of the hand is facing forwards and upwards e.g. table tennis backhand top spin
points the toes downwards by straightening the ankle e.g. jumping in gymnastics
an upward movement, as in moving the foot to pull the toes towards the knee when walking
involves movement beyond the normal anatomical position in a direction opposite to flexion. This occurs at the spine when a cricketer arches their back when approaching the crease to bowl.
when we start to exercise the movements of our joints means that synovial fluid starts to secrete within the joints. The fluid becomes less viscous and therefore the range of movement within the joint increases. An example of this in sport is the need for a warm up for a butterfly swimmer. So they can get the full range of movement at the shoulder joint that area must be warmed up prior to the race.
To know the structure and function of the skeletal system
To describe the axial and appendicular skeleton
To learn the location and names of all major bones
To know all three classifications of joints and the movement available at each
Label the bones of the human skeleton.
Task: colour in the appendicular section of this skeleton
Q: Name the five types of bones and provide two examples for each
P2: Joint Classification
Assignment 1 Weight: 5% Minimum Pass Grade: 50% Each question is worth 10 marks. 1. Maintenance of calcium ion homeostasis is critical to neurological, cardiac and skeletal muscle function. Consider the roles of two hormones involved in the regulation of the concentration of calcium ions in the blood. Parathyroid hormone increases the concentration of calcium ions in the blood, while calcitonin decreases the concentration. Based on this information predict the body’s response to restore calcium balance if a person swallowed 100 antacid tablets made of a calcium compound in 10 minutes. Include in your answer the definition of homeostasis, the type of feedback loop involved and all of the components of a feedback loop. Answer: Homeostasis is the condition of equilibrium in body’s internal environment due to constant interaction of the body’s many regulatory processes. As these regulatory processes create a shift in equilibrium, dynamic feedback system will bring them back to the small range of condition that is necessary for life. The antacid (made of calcium compound) will increase the calcium in the blood, so in response the thyroid would release calcitonin (hormone that opposes the action of the parathyroid hormone) in an attempt to achieve homeostasis once again. Calcitonin works by inhibiting the activity of osteoclasts (breakdown bone tissue which in turn lessens the amount of calcium in the blood). Parathyroid hormone would also be inhibited which would inhibit the further increase of calcium. The type of feedback involved is a negative feedback (the body will stop the loop once optimal state has been reached and homeostasis is achieved). The stimulus ( increase level of calcium in the blood) affects the optimal levels of calcium in the blood ( controlled condition). This causes the thyroid (receptor) to releases the hormone calcitonin. Osteoclast (effector) breakdown tissue and increase the rate of calcium deposition in the bone. Result includes decrease level of calcium in the blood stream (response). Once the calcium level reaches an optimal level, homeostasis has been achieved and negative feedback loop will stop. 2. Provide one important example (in the human body) of each of the following: a. a molecule containing ionic bonds NaCl-Sodium Chloride Sodium chloride is necessary to maintain body’s fluid balance, plays a role in muscle relaxing and transmitting of nerve signals. Sodium chloride also plays a major role as an electrolyte and is the principle ion in the extracellular compartment which includes blood plasma and interstitial fluid . Another role of sodium chloride is how it playa role in the electro-chemical gradient known ad membrane potential. Sodium absorption plays role absorption of glucose, water and amino acid. Another major role of sodium is seen in the sodium-potassium pump. Sodium is a crucial for the normal functioning of the pump. b. a molecule containing covalent bonds Oxygen-02 Assignment 1 :: Biology 235: Human Anatomy and Physiology 1 One of the main functions of oxygen is for body function such as respiration. Oxygen is required to release waste gas in the form of CO2. Oxygen plays a role in the metabolic processes. Adequate O2levels are required to support cell respiration. Oxygen is essential in energy metabolism (the sum of all of body’s chemical processes) and needed for growth, repair and maintenance of cells and tissues. Oxygen plays a vital role in cellular respiration (release energy that is stored as ATP that the body uses in different process as needed. c. a molecule containing hydrogen bonds H20-water Water plays a role in thermoregulation (through sweating to decrease body temp), homeostasis, and cell function and is vital for normal functioning of some organs. Water acts as a lubricant in some organs such as the lungs and GI track to prevent friction and to allow normal body functioning to take place Water is needed for some chemical and metabolic reactions by playing a role in the breakdown of what we consume (lipids, protein, and carbohydrates). Water is essential for transport of nutrient and removal of waste from the body. What is the function of each of these three molecules you have identified in the human body? Explain why each of these three molecules must have its specific types of bonds in order to perform that molecule’s function. A) It must be an ionic bond so it can break into positive and negative ions in solution, which becomes electrolytes. Sodium ion loses an electron so chloride can gain the electron, which allows the two to attract and form the sodium chloride. B) In covalent bonds, atoms share electrons rather than gaining or loosing electrons. This allows the oxygen to achieve stable structure through the sharing of the two electrons. C) Hydrogen bond provides stability and strength. Such bonds link water molecule together , give water molecule cohesion (tendency of like particles to stay together), which creates surface tension (influence is seen when breathing s increased). 3. Define mitosis and meiosis, and describe the differences between these two processes. Mitosis results in the formation of two identical diploid cells. First the distribution of 2 sets of chromosomes into two separate nuclei. Mitosis involves four stages: prophase, metaphase, anaphase and telophase. Mitosis also undergoes the process of cytokinesis (develops in late anaphase with formation of a cleavage furrow and ends once mitosis is completed). Mitosis is used by single cells to reproduce. Meiosis is involved in sexual reproduction. Meiosis is a process that produces haploid gametes cells and occurs in two successive stages. This process consists of two nuclear divisions called meiosis 1 and meiosis 2. In meiosis 1, homologous chromosomes undergo synapsis and crossing over, which results in genetically different offspring. Generally meiosis 1 begins with diploid starting cells and ends with two cells each with haploid number of chromosomes. Meiosis one results in two unlike haploid cells. Meiosis 1 like mitosis also includes the same 4 stages. 2nd stage of meiosis also includes 4 stages as well, similar to those of mitosis and meiosis 2. 4. List the skin glands and write details about their functions. What would be the consequences if a person’s skin glands stopped functioning? Assignment 1 :: Biology 235: Human Anatomy and Physiology 2 Sebaceous (Oil) Gland Sebaceous glands are found in the lips, groin, penis, labia majora and tarsal glands of the eyelid. Sebum secretion consists of a mixture of cholesterol, protein, inorganic salts and triglycerides. It also plays a role in preventing hair from drying out, prevents water loss from the skin, keeps skin soft, inhibits growth or some bacteria. Some of the consequences that may be experience if this gland stopped working would include alteration in temperatures (as the gland isn’t able to prevent water loss), skin becomes dry and flaky, and potential for bacteria growth. Ceruminous Gland Ceruminous gland is found in the external auditory canal and produces a waxy lubricating secretion (Cerumen). It plays a role in preventing entrance of foreign bodies, prevents microbes from entering cells and waterproofs the canal. Consequences of this gland not functioning are entering of microbes, water and foreign object entering the ear canal, which could lead to ear damage. Sudiriferous Glands Sudoriferous gland is also knows as sweat gland. Cells of this gland releases perspiration into hair follicle or skin surface. There are 2 main type of sweat gland depending on structure and secretion. Waste buildup and increase body temperature (from lack of perspiration) are some of the consequences if this sweat gland stops functioning. The first is Eccrine gland. Eccrine gland is found throughout the skin. Perspiration consist of water, ions( NA, CL, Urea, Uric acid, ammonia, amino acid, glucose and lactic acid). Through perspiration, eccrine gland plays a role in regulating body’s temperature, removing waste. Second gland is apocrine gland. Apocrine gland is usually found in the axillae, groin, areola, bearded region of the face, clitoris and labia minora. Secretions released are the same as eccrine gland with the addition of lipids and proteins. Mammary Gland Mammary gland is a modified sweat gland that produces milk. The function of mammary gland is synthesis, secretion and ejection of milk (lactation). Consequences as a result of this gland not working includes lack of production of milk, resulting in lack of breastfeeding and the need for formula supplementation. 5. Describe how the structures of the epidermis allow it to provide immediate and indirect protection to underlying tissues. The epidermis is made up of keratinized stratified squamous epithelium, allowing the epidermis to be play a role in protection of skin from dehydration, UV ray damage and foreign objects. The epidermis is made up of four different types of cells that play a role in the function of the epidermis. Such cells include: keratinocytes, melanocytes, Langerhans and merkel cells. Keratinocytes of course produce keratin ( helps protect the skin and underlying tissue from heat, abrasion, microbes and chemicals). It also produces lamellar granules (releases water repellent sealant that decreases water entry and also inhibits entry of foreign material). Melanocytes produce melanin (responsible for skin color and provides protection against damaging UV radiation). Langerhans cell play a role in immunity. Major role of these cells is to assist immune cells in recognizing microbes and to destroy those invading microbes. Merkel cells are located in the deepest layer of epidermis where that contact disc that can detect touch ( Merkel disc). There are places on the body that have thin skin and some that have thick skin, depending on the amount of friction at the certain area. Thin skin contains four layers( stratum basale, stratum spinosum, stratum granulosum and stratum corneum) and is found all over the body. Thick skin contains five layers, all of the Assignment 1 :: Biology 235: Human Anatomy and Physiology 3 ones that think skin contains, with the addition of stratum lucidum. Stratum lucidum contains keratin. Thick skin is found on areas of the body that are exposed to lots of friction such as the fingertips, palms, and soles of the feet. A callus also help protect the skin as it thickens the skin by adding extra keratin to area exposed to extensive amount of friction. 6. Fill in the words or phrases that best complete each of the following sentences. a. Functions of the skeletal system include support, protection, assisting in movement, mineral homeostasis, and blood cell production and triglyceride storage. b. The hollow space inside of long bones that is lined with endosteum and filled with yellow marrow is the medullar cavity. c. The protein that provides flexibility and tensile strength to bone is collagen. d. compact bone tissue is organized into concentric rings of bone tissue, which are called osteons or haverisan system . e. nerves accompany blood vessels within bone tissue; the periosteum is enriched with sensory neurons. f. Ossification may also be called osteogenisis; in an embryo, it begins with the organization of mesenchyme tissue into the general shape of bones. g. Intramembranous ossification occurs between fibrous connective tissue sheet-like layers that resemble membranes. h. Activity of the epiphyseal plate causes the diaphysis region of a bone to grow in length. i. Human growth hormone (HGF), IGFs, insulin and T3/T4 are the primary stimulators of bone growth before puberty. j. calcitriol is the hormone that inhibits the effects of parathyroid hormone. 7. Match the items in column A with the descriptions in column B to create the BEST MATCHES. Items in column A can be used more than once when making matches to column B. However, there is only one correct answer for each blank space. Column A Column B a. articular cartilage X raises blood Ca2+ levels by increasing osteoclast activity and blocking kidney secretion of Ca2+ J struts or plates within spongy bone that assist in withstanding stresses in a specific direction F channels in bone matrix; allow osteocytes to communicate with each other D expanded ends of a long bone K occurs after development of ossification center during intramembranous bone development; occurs prior to b. c. d. e. f. g. h. i. j. diaphysis endosteum epiphyses periosteum canaliculi lacunae lamellae osteons trabeculae Assignment 1 :: Biology 235: Human Anatomy and Physiology 4 k. l. m. n. o. p. q. r. s. t. u. v. w. x. y. calcification development of cartilage model development of ossification center development of periosteum osteoblast intramembranous ossification osteoclast zone of hypertrophic cartilage zone of proliferating cartilage zone of calcified cartilage calcitonin calcitriol foramen parathyroid hormone fossa formation of trabeculae C lines the marrow cavity E protects bone; assists in fracture repair W a rounded passageway through a bone that permits blood vessels and/or nerves to pass B shaft of a long bone P process where the bone develops from mesenchyme, often forming flat bones I structural units of compact bone Q bone cell that breaks down old bone matrix G spaces in bone matrix that contain osteocytes F tiny channels connecting osteocytes with the central canal of an osteon M occurs when mesenchymal cells cluster and differentiate during intramembranous bone development U inhibits osteoclastic activity A reduces friction and absorbs shock at joints that have a wide range of motion P the highly vascularized mesenchyme on the outside of the new bone that develops in the periosteum L does not occur during intramembranous bone development; must arise from mesenchyme template A part of a long bone that is not covered by the periosteum is covered by this structure 8. a. Match the items in column A with the descriptions in column B to create the BEST MATCHES. Items in column A can be used more than once when making matches to column B. However, there is only one correct answer for each blank space. Column A Column B 1. pronation a. 7 straightening the elbow joint 2. abduction 3. inversion 4. gliding 5. depression 6. dorsiflexion 7. extension 8. retraction 9. lateral flexion 10. circumduction 11. plantar flexion b. 15 moving the arm anteriorly c. 2 spreading the fingers apart d. 5 opening the jaw e. 11 bending the ankle joint so that the foot moves downward f. 13 moving a thigh straight toward the other thigh g. 14 bending the wrist joint so that the hand moves posteriorly h. 9 bending the head so that it moves toward the right shoulder i. 15 bending the knee joint Assignment 1 :: Biology 235: Human Anatomy and Physiology 5 12. elevation 13. adduction 14. hyperextension 15. flexion 16. medial rotation 17. eversion 18. protraction 19. supination 20. lateral rotation j. 10 moving the thumb around in a circle b. From the movements listed in column B, list the scientific names of the bones (learned in earlier chapters) that meet at each joint, i.e., where each movement occurs. Note: The spaces below require one or two bones of a certain region. Be very specific when required. a. Trochlea and capitulum of humerus articulates with trochlear notch of the ulna and head of radius b. Head of humerus articulates with glenoid cavity of scapula c. Metacarpals articulates with proximal phalanges d. Mandible articulates with zygomatic process of temporal bone e. Lateral malleolus of fibula and medial malleolus of tibia articulates with calcaneous f. femur articulates with acetabulum of pelvis g. lunate of carpals articulates with lateral styloid process of radius and medial styloid process of ulna h. anterior arch of the atlas articulates with dense of the atlas i. femur articulates with tibia j. trapezium of carpals articulates with metacarpals bones 9. Compare the organization and functions of axial and appendicular skeletons, and describe in detail the girdles of the latter. The axial skeleton is the central core of the human body. It consists of 80 bones, 29 bones in skull ( 8 cranial and 14 facial), Hyoid bone, 6 auditory ossicles, and 25 bones of the thorax (the sternum and 24 ribs). Their function is to protect the vital organs of the body, including the brain, spinal cord, heart and lungs. They also contribute to the support of the body and calcium homeostasis. The appendicular skeleton is made of the bones of the upper limbs and the bones forming the girdle that connects the limb to the axial skeleton. The Appendicular skeletons consist of a total of 126 bones. These bones include the pectoral girdles bones, 60 bones of the upper limb (radius, ulnar, humerus, carpals, metacarpals and phalanges), 2 bones of the pelvic girdle. It also includes 60 bones of the lower limbs (includes femur, patella, fibula, tibia, tarsals, metacarpals and phalanges). Theses bones are connected to one another and with the skeletal muscle (this in turn allows movement). The 2 pectoral girdle each consist of a clavicle and a scapula ( theses also attach the bones of the upper limb to the axial skeleton). The pelvic girdle consists of 2 hipbones that join at the pubic symphysis. Assignment 1 :: Biology 235: Human Anatomy and Physiology 6 The bony pelvis provides a strong and stable support for the vertebra column, organs of the lower pelvis and abdomen and it also connects bones of the lower limbs to axial skeleton. 10. Match the items in column A with descriptions in column B to create the BEST MATCHES. Items in column A can be used only once when making matches to column B. There is only one correct answer for each blank space. Column A Column B 1. contractility 2 property allowing muscle tissue to return to its original shape after contraction 2. elasticity 3. electrical excitability 4. extensibility 5. thermogenesis 6. endomysium 7. epimysium 8. fascicles 9. perimysium 10. tendon 11. myoblasts 12. myofibers 13. sarcolemma 14. sarcoplasm 15. sarcoplasmic reticulum 16. A band 17. H zone 18. I band 19. M line 20. Z discs 21. actin 22. myosin 23. titin 24. troponin 25. tropomyosin 26. acetylcholine 27. acetylcholinesterase 28. Ca2+ 29. calsequestrin 30. Na+ 31. myogram 32. relaxation period 33. twitch contraction 34. contraction period 35. wave summation 15 modified smooth endoplasmic reticulum of muscle cell; stores Ca2+ 5 function of muscle; heat generation 34 type of contraction responsible for most of the smooth, sustained movements performed by the skeletal muscle 1 property allowing muscle to shorten forcefully when stimulated by an action potential 29 molecule needed for maximum storage of Ca2+ in sarcoplasmic reticulum 10 formed by fusion of connective tissues; joins muscles to bones 24 regulatory protein associated with thin filament; binds Ca2+ 8 bundles of muscle fibers 11 embryonic cells; fuse to form muscle cells 16 region where thick and thin filaments overlap each other 9 connective tissue around one bundle of muscle fibers 20 sites delineating ends of sarcomeres 23 structural protein; anchors thick filament to M line and Z disc 19 site where support proteins hold thick filaments together 21 contractile protein found in thin filament 27 enzyme that removes neurotransmitter from synaptic cleft; helps muscle relax 35 phenomenon in which successive stimulations cause stronger contractions 30 ion that enters muscle fiber, causing depolarization and allowing muscle action potential to propagate 33 contraction of a single muscle following a single stimulation Assignment 1 :: Biology 235: Human Anatomy and Physiology 7 Assignment 1 :: Biology 235: Human Anatomy and Physiology 8