Musculoskeletal System

Question 1

List the three types of muscle within the body.

Answer 1

1. Smooth
2. Skeletal
3. Cardiac

Question 2

Types of muscle responsible for voluntary movement (innervated by SNS), support, thermoregulation, and blood propulsion within the venous system.

Answer 2

Skeletal Muscle

Question 3

List the major characteristics of skeletal muscle as well as the two major types of fibers within this muscle type.

Answer 3

1. Striated (due to actin/myosin arrangements in sarcomeres)
2. Multi-nucleated
3. Two types of Fibers
   
   1. Slow Twitch fiibers
   2. High Twitch Fibers

Question 4

Skeletal Muscle fibers that appear dark red, have a high myoglobin concentration, and contract slowly. (also have tons of mitochondria that carry out oxidative phosphorylation)

Answer 4

Slow Twitching (Red Fibers)

Question 5

Type of skeletal muscle that have much less myoglobin, rapidly contract, and fatigue quickly.

Answer 5

Fast Twitching (White) Skeletal Muscle Fibers

Question 6

List the important features of smooth muscle.

Answer 6

1. Responsible for Involuntary Muscle Actions
2. Controlled by autonomic system
3. Single nucleated
4. Has actin and myosin, but not as well organized as skeletal muscle
5. Capable of more sustained contractions (tonus)
6. Exhibits myogenic activity

Question 7

Myogenic Activity

Answer 7

Ability to contract without nervous system acitivity. Muscle cells are able to contract or stretch in response to stimuli (smooth muscle)

Question 8

List major characteristics of skeletal muscle.

Answer 8

1. Uninucleated (but may containt two nuclei)
2. Innervated by autonomic nervous sysyem
3. Appear striated
4. myogenic activity

Question 9

How does cardiac cells communication during depolarization?

Answer 9

Intercalated discs and gap junctions (allow for rapid and coordinated muscle cell deporalization during heart contractons)

Question 10

How do the nervous and endocrine play a role in the contraction of cardiac muscle?

Answer 10

1. Vagus nerve: slows HR (via parasympathetic system)
2. Nor-epinephrine from sympathetic nerves
   
   1. Increase HR (greater contractility)
3. Epinephrine from adrenal medulla
   
   1. Increase HR (greater contractility)

Question 11

Basic Contractile unit of Skeletal Muscle

Answer 11

Sacromere

Question 12

Name the major structures of sacromere.

Answer 12

1. Actin (Thin Filaments)
2. Myosin (Thick Filaments)
3. Tropomyosin
4. Troponin

Question 13

Name the lines that divide the sarcomere into different zones/bands.

Answer 13

1. Z-lines: Define boundary b/t each sarcomere
2. I-Bands: Only actin filaments
3. H-Band: Only thick Filaments
4. A-Band: Thick filaments w/ overlapping thin filaments
5. M-Line: Runs down the center of a sarcomere

Question 14

Which band remains a constanr size during contraction of a muscle?

Answer 14

A-Band (all other bands/lines decrease in size)

Question 15

What are myofibrils?

Answer 15

sacromeres attached end to end (contain actin and myosin filaments)

Question 16

What are myocytes?

Answer 16

Muscle cells (muscle fibers)

Question 17

Modified endoplasmic reticulum. Stores Ca++ ions necassary for muscle contractions.

Answer 17

Sarcoplasmic Reticulum

Question 18

Cell membrane of a myocyte

Answer 18

sarcolemma

Question 19

Neurotransmitter that travels through the neuromuscal junction and binds to ligand gated receptors on sarcolemma, ultimately initiating an action potential.

Answer 19

Acetylcholine

Question 20

Modified cytoplasm located just outside of sarcoplasmic reticulum.

Answer 20

Sarcoplasm

Question 21

Nerve terminal + myocytes it signals

Answer 21

Motor Unit

Question 22

Explain steps of muscle contraction (starting from depolarization after threshold has been reached).

Answer 22

1. AP spread down sarcolemma to Transverse Tubules to sarcoplasmic reticulum
2. Sarcoplasmic Reticulum releases Ca++
3. Ca++ binds to Troponin, changing confirmation ofn Tropomyosin, exposing the “myosin binding site” on actin
4. Myosin head moves toward and binds with actin
5. Myosin head expels phosphate and ADP and bends into a low energy position
6. Myosin “pulls” actin during power stroke, shortening sarcomere, resulting in a muscle contraction
7. ATP reattaches to myosin head (after contraction is complete), releasing myosin from actin active site
8. Myosin is now in high energy position, and ready to repeat cycle of binding to actin.
9. Acetylcholine is degraded by ACh-esterase in neuromuscular junction
10. AP terminates
11. Sarcoplasmic reticulum take up Ca++ that was released
12. Ca++ is no longer bound to Tropomyosin, and the active site of actin is now covered
13. Myosin stops binding to actin and goes back to high energy “cocked” position, bound to ATP.

Question 23

Reponse of a single muscle fiber to a brief stimulus at or above threshold. Consists of a latent, contraction, and relaxtion period.

Answer 23

Simple Twitch

Question 24

What s frequency summation and what can it lead to?

Answer 24

1. Frequent and prolongue stimulation, resulting in insufficient time to relax
2. Tetatus: prolongued contraction resulting in the inability for muscle to relax.

Question 25

Muscle cell have energy reserves to reduce oxygen debt and forestall fatigue. What are two ways muscles cells can do this?

Answer 25

1. Creatinine Phosphate: Transfer phosphate group to ADP, produces ATP 2. Myoglobin: Heme containing protein that is a muscular oxygen reserve. (only has one heme subunit)

Question 26

Exoskeleton vs Endoskeleton

Answer 26

External Skeletons va. Internal Skeletons

Question 27

Axial Skeleton vs. Appendicular Skeleton

Answer 27

midline strucutes (head and trunk) vs limbs (pelvis and all limbs)

Question 28

Name two major components of our skeleton.

Answer 28

Bone and cartilage

Question 29

Dense bone vs Cancellous Bone

Answer 29

Compact Bone vs. Spongy Bone

Question 30

What are the two types of marrow within the marrow cavity of bone marrow?

Answer 30

1. Red Marrow: filled with hematopoietic stems cells (respnsible for generating red blood cells) 2. Yellow Marrow: composed of fat (relatively inactive)

Question 31

Describe the main bone structures within skeletal muscle.

Answer 31

1. **Long Bones** that include: 1. **Diaphyses** that swells into **metaphayses** and terminates into **epiphyses** 2. Diaphyses and Metaphyses: composed on compact bone and contain bone marrow 3. Epiphysis: consists of spong bone 1. Includes **epiphyseal (growth) plate** (between epiphyses and metaphyses

Question 32

Cartilaginous Structure that causes linear growth in bone and close during puberty

Answer 32

Epiphyseal Growth Plate

Question 33

Surrounds Long Bone and attaches it to muscles

Answer 33

Periosteum

Question 34

\_\_\_\_\_\_\_ attach muscle to bone, \_\_\_\_\_\_\_hold bones together at joints.

Answer 34

1. Tendons 2. Ligaments

Question 35

The bone matrix is important for storage of organic and inorganic compounds. What are the inorganic compounds? What are the organic compounds that make up the Hydroxyapatite.

Answer 35

1. Inorganic Compounds: glycoproteins, peptides, and collage 2. 2) Hydroxyapatite: Calcium, Phosphate, Hydroxide Ions

Question 36

What is the purpose of Hydroxyapatite?

Answer 36

1. Strength 2. Maintanence of these ions concentrations in the blood

Question 37

What is the purpse of fat stored in bone?

Answer 37

Energy Storage

Question 38

Describe the organization of the Osteon/Haversion System

Answer 38

1. Each osteon contains concentric circles of lamellae, surrounding a central channel 1. Longitudinal Channel: Haversion Canals 2. Transverse Channel: Volkman's Canals 2. B/t lamellae are lacunae (house osteocytes) 3. Lacunae are interconnected by canaliculi 1. Canaliculi allow for exchange of nutrients between osteocytes trapped in lacunae

Question 39

Macrophages that "Chew" bone and release nutrients/minerals to blood stream. Create the canals for which osteoblasts and vessels can travel through. Important for bone remodeling

Answer 39

Osteoclasts

Question 41

Follow the canals built by osteoclasts and secrete collagen and organic compounds to create matrix. Also become encased in matrix and differentiate in osteocytes.

Answer 41

Osteoblasts

Question 42

The inorganic compounds are absorbed by the out of the blodstream, and harden the matrix secreted by the osteoblasts

Answer 42

Calcium and Phosphate

Question 43

This hormone is secreted by the parathyroid gland and triggers increased activity of osteoclasts, releasing calcium and phosphate back into the bloodstream when these levels are low.

Answer 43

PTH Hormone

Question 44

This hormone is released by the thyroid and triggers increased osteoblast activity, decreasing calcium levels in the blood when they become too high.

Answer 44

Calcitonin

Question 45

Activated by parathyroid home to increase resorption of bone. These leads to high bone turnerover, resulting in stronger bones.

Answer 45

Vitamin D

Question 46

Chondrin

Answer 46

Matrix secreted by chondrocytes for cartilage formation

Question 47

Describe three important characteristics of cartilage

Answer 47

1. Elastic 1. Found in areas requiring more flexibility and cushioning 2. Avascular 3. Not innervated.

Question 48

Immovable Joints

Answer 48

Joints fused together

Question 50

Moveable Joints

Answer 50

Joints connected by ligaments and contain synovial capsule

Question 51

Fluid within sinovial capsules that lubricate the joint.

Answer 51

Synovial Fluid

Question 52

Aticular Cartilage

Answer 52

Coats joints and aids in movement/cushioning

Question 53

Muscles that serve opposite functions. When one muscle contracts, the other lengthens.

Answer 53

Antogonist Pairs