Anatomy & Physiology Semester Exam Review



Anatomy & Physiology Semester Exam Review

1. Differentiate between anatomy and physiology

Anatomy – study of structure; physiology – study of function; structure determines function

2. List and explain the function necessary for maintaining life (characteristics of life)

Responsiveness, conductivity, growth, respiration, digestion, absorption, secretion, excretion, circulation, reproduction

3. List and describe the levels of organization within the body

Subatomic particles ( atom ( molecule ( macromolecule ( organelle ( cell ( tissue ( organ ( organ system ( organism

4. List the three basic components of every feedback control system

Sensor (receptor), integrator (control center), effector

5. Explain the mechanisms of action (overall goal) of negative and positive feedback control systems

Negative – to correct, stop, inhibit a change; positive – stimulates a change

6. Compare and contrast the following: superior/inferior, posterior/anterior, proximal/distal, lateral/medial. Be able to use these terms to describe parts of the body.

Superior – towards the head

Inferior – towards the feet

Posterior – back of the body

Anterior – front of the body

Proximal – towards the core of the body (referring to appendages)

Distal – away from the core (referring to appendages)

Lateral – away from the midline

Medial – towards the midline

7. Name and describe the 3 planes used to divide the body

Sagittal – right & left halves

Transverse – superior and inferior halves

Frontal or coronal – anterior and posterior halves

8. Differentiate between ionic and covalent bonds.

Ionic – electrons are transferred

Covalent – electrons are shared

9. Explain the importance of water within the human body. What percentage of the body is water?

Makes up 70% of the human body

10. Distinguish between each of the 4 classes of organic molecules in terms of structure and function.

Carbohydrates:

Monomer – monosaccharide

Function – energy for cellular activities

Proteins:

Monomer – amino acid

Function – defense system (antibodies), receptor sites, structural support (skin, tendons, nails), enzymes, communication (insulin is a protein hormone)

Lipids:

Structure: glycerol & 3 fatty acid tails

Function: concentrated energy source

Nucleic Acids:

Monomer: nucleotide (sugar, phosphate group, nitrogen base)

Function: store genetic information (DNA), transfer genetic information (RNA)

11. Differentiate between acids and bases.

Acid – any substance that releases H+ when in soluntion (“proton donor”); lowers pH

Base – any substance that increases the OH- concentration when dissociated in solution (“proton acceptor”); increases pH

12. Discuss the structure and function of the following: endoplasmic reticulum, ribosomes, golgi apparatus, mitochondria, lysosomes, peroxisomes, cytoskeleton, cell fibers, centrosome, centrioles, cell extensions and nucleus.

Endoplasmic reticulum: protein synthesis and intracellular transport

Ribosomes: site of protein synthesis (cell’s “protein factory”)

Golgi apparatus: “processing and packaging plant”; exports proteins made in rough ER

Mitochondria: “power plant”; ATP is synthesized

Lysosomes: “digestive bags”; rid cell of wastes

Peroxisomes: detoxifying function; important to liver and kidneys

Cytoskeleton: cell fibers, centrioles, centrosome

Cell fibers:

Microfilaments: “cellular muscles”

Intermediate filaments: main components of the supporting framework in many cells

Microtubules: cell “engine” – help with movement within cell and of the cell itself

Centrosome: “microtubule-organization center”; important in cell division b/c helps move chromosomes around the cell

Centrioles: cylindrical structures within the centrosome; role in cell division

Cell extension:

Microvilli – increase surface area; increases absorption (small intestine)

Cilia – transport fluid across cell surface (ex: respiratory tract, reproductive tract)

Flagella – aids in locomotion (ex: sperm cells)

Nucleus: Cell’s “brain”; contains DNA; site of transcription

13. Differentiate between embedded and peripheral proteins (structure and function).

Embedded: penetrate the entire plasma membrane; transport mechanism; act as channels or gates

Peripheral: identification markers (immune system); receptor sites

14. Compare and contrast the processes of diffusion, dialysis, facilitated diffusion, osmosis and filtration.

**All PASSIVE transport ** do NOT require energy ** occur DOWN a concentration gradient**

Diffusion: tendency of small particles to spread out within a given space

Dialysis: selectively permeable membrane separates small and large particles

Facilitated diffusion: diffusion across a membrane with the help of a carrier protein (also called carrier-mediated passive transport)

Osmosis: diffusion of water across a selectively permeable membrane

Filtration: passive of water and permeable solutes through a membrane by the force of hydrostatic pressure

15. Contrast isotonic, hypotonic and hypertonic solutions. Explain how they affect osmosis.

**Refers to SOLUTE concentrations ** water will diffusion to area of HIGH solute concentration b/c there is a LOWER water concentration**

Isotonic: ECF = ICF; no net movement of water

Hypotonic: ECF < ICF; water diffuses into the cell; cell swells (remember hypO)

Hypertonic: ECF > ICF; water diffuses out of the cell; cell shrinks

16. Name and explain the 3 types of active transport discussed in class.

**REQUIRE energy (ATP) ** occur AGAINST a concentration gradient (“uphill”)**

Sodium-potassium pump: transports Na+ out of the cell and K+ into the cell; 3Na+ for 2K+

Endocytosis: brings large molecules into the cell

Exocytosis: large molecules exit the cell

17. Differentiate between the purines and pyrimidines.

Purines: adenine & guanine

Pyrimidines: cytosine & thymine

18. How do the base pairs differ in RNA?

Uracil replaces thymine (uracil binds with adenine)

19. Explain the processes of transcription and translation.

Transcription:

DNA “unzips”

RNA nucleotides attach themselves to the exposed bases along one side of the DNA molecule

RNA polymerase binds RNA nucleotides

Results in messenger RNA (mRNA) (“transcript of the gene”)

mRNA pulls away from the DNA template

non-coding portions (introns) are removed

exons are spliced back together

mRNA travels to cytoplasm via the nuclear pores

Translation:

Ribosomal subunits attach to one end of the mRNA

Transfer RNA (tRNA) bring specific amino acids to the ribosomal site (based on each mRNA codon)

Amino acids are joined together by polypeptide bonds

Many polypeptide chains result in a protein

20. What is the overall goal of mitosis?

Production of TWO IDENDICAL daughter cells

21. What are the phases of mitosis? What is occurring in each phase?

(PMAT)

Prophase: chromosomes shorten & thicken; nuclear envelope breaks down; spindle fiber formation

Metaphase: chromosomes line up in the middle of the cell; spindle fibers attach at centromere

Anaphase: spindle fibers pull sister chromatids away/apart from each other

Telophase: cleavage furrow forms; nuclear envelope reappears

22. What is the overall goal of meiosis? What is it referred to as “reduction division”?

2 haploid gametes; reduces the number of chromosomes from 46 to 23

23. List the 4 tissue types in the human body.

Epithelial, connective, muscle, nervous

24. Describe the function of each tissue type (general terms)

Epithelial: protection (covers body surfaces), sensory, secretion (glandular epithelium), absorption (gut; respiratory tract – exchange of O2 and CO2), excretion

Connective: support, connection, transport, protection

Muscle: move body, specialized for contraction

Nervous: provides communication; coordinates body’s functions

25. Name the 3 primary germ layers and state which tissue types develop from each layer

Ectoderm – nervous, epitherlial

Mesoderm – muscle, epithelial, connective

Endoderm - epithelial

26. Explain and apply the classification methods used to classify membranous epithelial tissues

Cell Shape:

▪ Squamous: flat, plate-like

▪ Cuboidal: cube-shaped; larger cytoplasm

▪ Columnar: narrow and cylinder-shaped

▪ Pseudostratified: single-layered; all cells touch the basement membrane but may not extend to the top of the membrane

Layers of Cells:

▪ Simple: single layer

▪ Stratified: cells are layered on top of one another

▪ Transitional: cell shape & layers differ

27. Differentiate between endocrine and exocrine glands

Exocrine glands:

▪ Discharge/secrete into ducts

▪ Ex: salivary glands

Endocrine glands:

▪ “ductless glands”

▪ Secrete hormones directly into blood or interstitial fluid

▪ Ex: pituitary and thyroid glands

28. Explain and apply the structural and functional classification methods for classifying exocrine glands

Structural:

Shape: tubular or alveolar (sac-like)

Complexity: simple (one duct) or compound (multiple ducts)

Functional:

1. Apocrine

– Collect secretory products at apex (tip)

– Apex of cell pinches off

– Cell repairs itself & repeats process

– Ex: milk-producing mammary glands

2. Holocrine

– Collect secretory product inside the cell

– Rupture to release (self-destructs)

– Ex: sebaceous glands (oil glands)

3. Merocrine

– Discharge through plasma membrane

– This type applies to most exocrine glands

– Ex: salivary glands

29. Describe the structure and function of the 4 types of connective tissues (remember the subtypes! – study your flow chart!) **connective tissue is the most abundant tissue in the body**

Fibrous

▪ Loose (areolar)

o Stretchable

o most abundant connective tissue in the body

o Connects adjacent structures

▪ Ex: btwn other tissues and organs

▪ Ex: superficial fascia

▪ Adipose

o Contains mainly fat cells

o Supportive/protection pads around kidneys & other body structures

o Storage deposit for excess food

o Insulating material, conserves body heat

▪ Reticular

o 3D web of reticular fibers

o Forms the framework of the spleen, lymph nodes & bone marrow

o Meshwork filters harmful substances out of the blood

▪ Dense

o Regular

▪ Fibers arranged in parallel rows

▪ Ex: tendons; ligaments

o Irregular

▪ Fibers intertwine; sustain stress from any direction

Bone

Cartilage

▪ Hyaline

▪ Most common

▪ Covers ends of long bones (where joints articulate)

▪ Found in supporting rings of respiratory tubes

▪ Fibrocartilage

▪ Strongest, most durable

▪ Intervertebral disks

▪ Menisci in knee joint

▪ Elastic

▪ Fine elastic fibers

▪ High degree of flexibility

▪ External ear

Blood

▪ Matrix = plasma

▪ Formed elements = blood cells

▪ Function ( transport respiratory gases (O2, CO2), nutrients, wastes

30. List the structural characteristics of skeletal, cardiac and smooth muscle tissue.

Skeletal: voluntary, striations, multi-nucleated, long, tread-like cells, bundles of microfilaments

Cardiac: striated, involuntary, intercalated disks (where plasma membranes meet up), branching

Smooth: non-striated, involuntary, spindle-shaped cells, uninucleated

31. List where the 3 types of muscle tissue can be found in the body:

Skeletal – muscles (attached to bone)

Cardiac – heart

Smooth – lines walls of hollow organs (stomach, intestines, blood vessels)

32. What are the 3 main parts of a neuron? Explain the function of these 3 parts.

Soma – cell body; hold nucleus

Dendrites – carry signals towards soma

Axon – carry signals away from soma

33. Which two tissue types have the greatest capacity for repair?

Epithelial and connective

34. How does connective tissue repair differ from epithelial tissue repair?

35. Describe muscle tissue repair:

Damaged muscle tissue is replaced by connective tissue; results in some or all loss of normal function

36. Differentiate between benign and malignant tumors.

Benign Tumors

▪ Do not spread to other tissues

▪ Slow growth

▪ Encapsulated

▪ Usually not lethal unless interfere w/ organs

Malignant tumors (cancer)

▪ Not encapsulated

▪ Spreads (metastasizes)

▪ Cancer cells spread via blood or lymphatic system

▪ Rapid growth/spread to nearby tissue

37. Complete the table relating to body membranes (you may need to refer to your textbook):

|Membrane |Tissue Type |Common Locations |Function(s) |

|Mucous |epithelial |Line body surfaces open to exterior |Mucous which coats cells provides |

| | |Ex: respiratory, digestive, urinary & |protection, lubrication for food & trap |

| | |reproductive tracts |for contaminates in respiratory tract |

|Serous |epithelial |Single membrane covering two surfaces: |Secrete thin, watery substance to |

| | |*Parietal membrane – lines walls of body|prevent rubbing |

| | |cavities | |

| | |*Visceral membrane – covers surface of | |

| | |organs | |

|Cutaneous |epithelial |Cover body surfaces exposed to external |protection |

| | |environment (skin) | |

| | | | |

|Synovial |connective |Lines spaces btwn bones & joints |*Secrete thick, colorless, lubricating |

| | | |fluid (synovial fluid) |

| | | |*Fluid helps reduce friction btwn bone |

| | | |surfaces |

38. What does integument mean? What are appendages? What are the skin’s appendages?

Integument = skin

Appendages = attachments (hair, nails, skin glands)

39. List and describe the 7 functions of the skin

Protection – from infection, dehydration, chemical/mechanical damage, ultraviolet radiation

Sensation – sensory receptors w/in skin

Movement w/o injury – elastic fibers allow movement & growth

Excretion – excretion of sweat; skin regulates volume & composition of sweat

Endocrine function (vitamin D) - First steps of vitamin D production occurs in the skin when exposed to ultraviolet light

Immunity – langerhan cells in skin help trigger immune response

Temperature regulation –

Vasoconstriction ( prevents heat loss ( warm blood circulating deeper within the body

Vasodilation ( increases heat loss ( increases skin’s blood supply ( heat lost to the external environment

40. Differentiate between thick and thin skin. (Remember these terms only apply to the epidermis).

Thin skin – covers most of body surface

Thick skin – palms of hands, soles of feet, finger tips

▪ All 5 layers of epidermis present

▪ Raised dermal papillae (fingerprints or footprints)

▪ No hair is present in thick skin

41. What are the two main layers of skin? Briefly describe the characteristics of these two layers. Which layer is vascular? Avascular?

Epidermis

▪ Avascular

▪ Outer, thinner layer

▪ 5 layers

▪ Thick & thin (see #40)

▪ 3 cell types (see #42)

▪ 5 strata (layers) – see #43

Dermis

▪ Vascular

▪ “true skin”

▪ Thicker than epidermis

▪ Protective function against mechanical injury

▪ Storage area for water and electrolytes

▪ Contains somatic sensory receptors (nerves & nerve endings)

▪ Process information such as: pain, pressure, touch, temperature

▪ Muscle fibers, hair follicles, sweat & sebaceous glands, blood vessels

42. List and describe the 3 cell types of the epidermis.

Keratinocytes: synthesize keratin

Melanocytes: synthesize melanin (brown pigment – gives skin color)

▪ Melanin: protects deeper layers from ultraviolet light

Langerhan cells (immune cells)

▪ Provide defense mechanism for the body

43. List and describe the 5 strata of the epidermis. Which layers are found only in thick skin? Where does keratinization begin? Which layer does mitosis take place in?

Stratum corneum (horny layer)

▪ Most superficial

▪ Shingle-like (squamous) dead cells

Stratum lucidum (clear layer)

▪ Only in thick skin

Stratum Granulosum (granular layer)

▪ Keratinization begins here

Stratum spinosum (spiny layer)

▪ 8-10 layers of irregular shaped cells

Stratum basale (base layer)

▪ Single layer of columnar cells

▪ Mitosis occurs here

44. How are “goose bumps” produced?

Contraction of the arrector pili muscles

45. What causes us to have distinct fingerprints and footprints?

Dermal papillae – bumps that project into epidermis

▪ Creates distinct ridges on epidermal surface of fingers & toes (finger/footprints)

▪ unique for every person

▪ in papillary layer of dermis

46. How does the vascular supply within the dermis play a role in the regulation of body temperature?

Vasocontriction: prevents heat loss ( warm blood circulating deeper within the body

Vasodilation: increases heat loss ( increases skin’s blood supply ( heat lost to the external environment

Negative feedback mechanism

47. What is the significance of cleavage lines?

If a surgeon cuts along a cleavage line there will be less incidence of a scar; cutting perpendicular to the cleavage line will cause increased stress on the incision which increases healing time and increases visibility/incidence of a scar

48. How do the quantity of melanocytes and the amount of melanin produced differ in people of different skin colors?

Quantity of melanocytes is constant among all races; amount of melanin produced differs

49. Describe the two “rules” for estimating the body surface area affected by a burn.

“Rule of palms” – the size of the patient’s palm is approximately 1% of their body surface

“Rule of nines”

▪ Body surface divided into 11 areas (anterior and posterior) of 9% (see figure in book)

▪ Perineum (genital area) accounts for 1 %

50. Describe the structure of hair (fig 6-10)

51. Describe the function of sebaceous glands. Why are teenagers going through puberty more prone to acne?

Secrete oil for skin & hair

Activated at puberty (stimulated by sex hormones)

Explains why teenagers are prone to acne

52. List and describe the 5 function of bones.

Support - Shape, alignment, positioning of body parts

Protection - Protects organs

Movement - Bones and joints act as levers; Muscles attached to bones produce movement of joints

Mineral storage - Calcium and phosphorous; Homeostasis of blood calcium levels

Hematopoiesis - Blood cell formation

53. What are the 2 types of skeletal tissue? Give a brief description of each type.

Compact bone

▪ Dense or solid appearance

Cancellous or spongy bone

▪ Open spaces filled with needle-like bone structures

54. List and describe the parts of a long bone.

Diaphysis

▪ Shaft of the bone

▪ Hollow, compact bone

Epiphyses

▪ Ends of the long bones

▪ Points of muscle attachment

▪ Stability to joints

▪ Spongy bone filled with red marrow

▪ Epiphyseal plate: area between diaphysis and epihyses (“growth plate”)

Articular cartilage

▪ Hyaline cartilage that covers joint surfaces

Periosteum

▪ Dense, white fibrous membrane that covers bone (excepts joint surfaces)

▪ Tendon fibers interlace with these fibers creating a firm attachment

Medullary (marrow) cavity

▪ Hollow space in diaphysis of long bones

▪ Filled with yellow marrow (CT rich in fat)

Endosteum

▪ Epithelial membrane that lines the medullary cavity

55. Bones can be classified into 4 groups based on their structure. List the four groups; give a brief description of each group and examples of each group.

Long bones

▪ typically longer than wide

▪ Have shaft w/ heads at both ends

▪ contains mostly compact bone

▪ Ex: femur, humerus, ulna, radius

Short bones

▪ Cube or box-shaped

▪ Mostly spongy bone

▪ Ex: carpals & tarsals

Flat bones

▪ Thin, flattened

▪ Usually curved surface

▪ Thin layer of compact bone covering spongy bone

▪ Ex: ribs, skull, sternum, scapulae

▪ Bone marrow aspirations occur here

Irregular bones

▪ Various shapes/sizes

▪ Do not fit into other categories

▪ Ex: vertebrae, facial bones

▪ Sesamoid bones: occur singularly (ex: patella)

56. How are fractures repaired? What must occur for this process to be successful?

Vascular damage initiates repair sequence

Vascular damage ( hemorrhage ( blood clot (fracture hematoma)

Hematoma resorbed ( callus

Callus replaced by normal bone tissue

**proper alignment & immobilization are necessary for healing to occur**

57. How does stress on bones affect the arrangement of the trabeculae?

Bony spicules of spongy bone arrange along lines of stress

▪ Varies for different types of bone

58. What is the structural unit of compact bone? List and describe the 4 components of an osteon.

Osteon

• Lamellae: concentric, cylinder-shaped layers of calcified matrix

• Lacunae (“little lakes”): small spaces filled with tissue fluid which hold bone cells

• Canaliculi: very small canals connecting lacunae together

• Haversian canal: extend lengthwise through the center of an osteo

59. What are volkmann’s canals?

Volkmann’s canal: (not part of osteon) transverse canals containing nerves and blood vessels

▪ Carry blood from exterior surface of bone to osteons

60. Be familiar with the names of the 7 tarsals.

Calcaneous (heel bone), navicular, cuniforms (3), talus, cuboid

61. How many vertebrae make up the cervical, thoracic and lumbar sections of the vertebral column? What is the correct order from superior to inferior?

Cervical – 7

Thoracic – 12

Lumbar – 5

62. Explain the function of the foramen magnum.

Hole through which the spinal cord enters the skull

63. Explain how joints can be classified both functionally and structurally.

Structural

Fibrous

Cartilaginous

synovial

Functional

Synarthroses

Amphiarthroses

diarthroses

64. What degree of movement is permitted in each category of joints (Table 9-1).

Synarthroses/fibrous – immovable (some slightly movable)

Amphiarthroses/cartilaginous (slightly movable)

Diarthroses/synovial – freely moveable

65. Describe how the three categories of joints are subdivided. What are the characteristics of each subcategory? Be able to identify examples.

Synarthroses/fibrous – immovable

Syndesmoses – fibrous bands connect two joints (ex radioulnar interosseous ligament)

Sutures – sutures in skull

Gomphoses – tooth socket

Amphiarthroses/cartilaginous (slightly movable)

Synchondroses – hyaline cartilage (ex: epiphyseal plates)

Symphyses – fibrocartilage (ex: symphysis pubis)

Diarthroses/synovial – freely moveable

Uniaxial: (move around one axis or one plane)

Hinge: knee, elbow

Pivot: atlas pivoting around axis (dens)

Biaxial (move around 2 axes or 2 planes)

Saddle joint: thumbs

Condyloid (ellipsoidal): radius & carpal bones

Multiaxial (move around 3+ axes or 3+ planes)

Ball & socket: hip, shoulder

Gliding: btwn successive vertebrae

66. Compare the hip and humeroscarpular joint (shoulder) in terms of mobility and stability. What causes this difference?

Hip ( more stable; less mobile; deep joint cavity

Shoulder ( less stable; more mobile; due to shallow joint cavity

67. Describe the structure and function of menisci.

Pads of fibrocartilage located btwn articulating ends of bones in some diarthroses

68. Be able to explain and identify examples of the following types of movements:

▪ Angular

o Flexion – decrease the angle

o Extension – increase the angle

o Hyperextension – increase the angle beyond 180 degrees

o Abduction – movement of appendages away from the midline

o Adduction – movement of the appendages towards the midline

o Plantar flexion – pointing the toe towards the ground (planting the toe)

o Dorsiflexion – pointing the toe towards the sky (walking on your heels)

▪ Circular

o Rotation – rotating on an axis (atlas on the axis – shaking your head “no”)

o Circumduction – making circles with appendage or body part

o Supination – twisting the palms outward (making a bowl of soup)

o Pronation – twisting the palms inward (passing a basketball)

▪ Special

o Inversion – soles of feet face inward (towards midline)

o Eversion – soles of feet face outward (lateral)

o Protraction – pushing a body part forward (push jaw forward – “under bite”)

o Retraction – pulling a body part back into place (correcting the “under bite”)

o Elevation – raising a body part (ex: closing the mouth – raising the mandible)

o Depression – lowering a body part (ex: opening the mouth – lowering the mandible)

69. What are the 3 function of muscle?

Movement, heat production, posture

70. Describe the specialization of a muscle fiber: specialized organelles, number of nuclei?, number of nuclei, number of mitochondrion?

Plasma membrane = sarcolemma

Cytoplasm = sarcoplasm

Sarcoplasmic reticulum = network of tubules and sacs (analogous to endoplasmic reticulum)

Multinucleated

Multiple mitochondria (directly related to energy needs of the muscle fiber; ex: athlete’s muscle fibers will have more mitochondria compared to someone w/ a sedentary lifestyle)

71. Explain the organization of a muscle (from muscle to myofilaments)

Muscle ( fascicle ( muscle fiber ( myofibril ( myofilament (thick and thin)

72. What is a sarcomere?

Contractile unit of a muscle fiber

73. Describe excitability, contractility and extensibility.

Excitability – ability of a muscle fiber to become stimulate by a nerve impulse

Contractility – ability of a muscle fiber to contract or shorten

Extensibility – ability of a muscle fiber to relax or extend back to its resting position

74. What is the purpose of the t-tubules? What is a triad?

Brings the nerve impulse deeper into the muscle fiber to simulate the sarcoplasmic reticulum

A triad is a t-tubule surrounded by two sacs of sarcoplasmic reticulum

75. What is the role of acetylcholine in skeletal muscle contractions? The role of calcium?

Acetylcholine stimulates the scarolemma causing a nerve impulse to travel along the muscle fiber

Calcium is binds with troponin causing tropomyosin to expose the actin binding sites for myosin (cross bridges can occur)

76. Where does the body get energy for muscle contractions? Is there an alternate source?

ATP ( ADP (ATP is produced by breaking down glucose in the presence of oxygen – aka cellular respiration)

Creatine phosphate can be broken down to provide energy to resynthesize ATP

77. What is a motor unit?

A motor neuron and all the muscle fibers it innervates

Lower ratio = precise movements

Higher ratio = less precise movements

78. Differentiate between isotonic and isometric contractions.

Isotonic – tension remains the same; length of muscle changes

Isometric – tension changes; length remains the same

79. Be able to describe the events of muscle stimulation/excitement, contraction and relaxation. Be able to put these events in order.

▪ Nerve impulse reaches the end of a motor neuron ( releases acetylcholine (Ach)

▪ Ach diffuses across the neuromuscular junction and binds with the receptors on the motor endplate

▪ Impulses travel along the sarcolemma ( t tubules ( sacs of SR

▪ Ca2+ is released from the sarcoplasmic reticulum ( binds with troponin

▪ Tropomyosin shift to expose actin’s binding site

▪ Energized myosin heads bind with myosin’s binding site and pulls thin filament towards center of sarcomere

▪ Nerve impulse is complete ( Ca2+ is pumped back into the sacs of the SR

▪ Ca2+ is stripped from the troponin ( tropomyosin covers the actin’s binding site

▪ Myosin heads can no longer bind with myosin ( muscle fiber returns to its resting length

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