Skeletal and Muscular Systems 2024 Student PDF

Unit 5 Skeletal and Muscular Systems 1 ORGAN SYSTEMS OF THE BODY: skeletal and muscular systems Muscular system All of the muscle tissues movement (voluntary and involuntary) Skeletal system: Bones (206 unique bones) Cartilage (cushions the bones)...

Unit 5 Skeletal and Muscular Systems 1 ORGAN SYSTEMS OF THE BODY: skeletal and muscular systems Muscular system All of the muscle tissues movement (voluntary and involuntary) Skeletal system: Bones (206 unique bones) Cartilage (cushions the bones) Ligaments (bone-bone connection) Protection and support Formation of blood cells (hematopoietic tissue) 2  The Skeletal System FUNCTIONS: Support Protection Movement Storage Primarily calcium Blood cell formation Hematopoiesis Bone marrow stem cells RBC WBC 3 BONE STRUCTURE 4 types of bones: Long bones (arm bone) Short bones (wrist bones) Flat bones (skull bone) Irregular bones (spinal bones) 4 BONE STRUCTURE 4 types of bones: Long bones (arm bone) Short bones (wrist bones) Flat bones (skull bone) Irregular bones (spinal bones) All bones consist of two main structures: Spongy (cancellous) bone – inside of bone; small cavities filled with marrow Compact bone – no open spaces; thin sheets that Let’s learn from the long bone… surround the cancellous bone (osteons) 5 BONE STRUCTURE Let’s learn from the long bone… Diaphysis (shaft) – hollow tube comprised of hard compact bone Medullary cavity – hollow area containing yellow bone marrow (inside the Diaphysis) Epiphyses – ends of the bone; red bone marrow fills in the spaces inside the spongy bone Articular cartilage – cushion of cartilage covering the Epiphysis Periosteum – dense fibrous tissue covering the bone Endosteum – thin membrane covering Medullary Cavity Yellow bone marrow = fat Red bone marrow = produces red + white blood cells BONE STRUCTURE The skeletal system contains two types of connective tissue: Bones Cartilage 7 BONE STRUCTURE – cartilage vs bone Cartilage and bone are both connective tissues Cartilage and bone are made up cells embedded in an extracellular matrix The nature of the matrix defines the differences Cartilage is more flexible than bone (fibers are embedded in a firm gel) Cartilage does not have blood vessels Cartilage cells receive nutrients through diffusion Cartilage recovers slowly from injury (due to lack of blood vessels) 8 BONE STRUCTURE Compact bone – organized into numerous osteons Cancellous Bone – “spongy bone”; contains cavities filled with red bone marrow Bone has a vast blood supply… …each vessel is central to the osteon (the smallest functional unit of the bone) Osteon: calcified matrix arranged in layers of rings; blood vessels and Visible Body nerves found at the center BONE STRUCTURE: CELLS Osteoblasts - bone-forming cells Osteoclasts – bone-resorbing cells; multi-nucleated Osteocytes- mature bone cells; locked in lacunae (space between the rings of the osteon) of compact bone Chondrocytes- cartilage cells Osteon: 10 BONE FORMATION AND GROWTH A skeleton in a newborn is made up of cartilage, not bone Cartilage is gradually replaced by a calcified bone matrix The process of forming bone out of cartilage is called endochondral ossification 1. Osteoblasts lay down collagen fibers and release calcium salts that will crystallize on the fibers 2. Osteoblasts eventually become trapped within the bone matrix; become osteocytes (stop making bone until surrounding bone is removed) 3. Osteoclasts dissolve calcium crystals to break down bone 11 A quick review… Visible Body: 12 https://www.youtube.com/watch?v=9eUDHcyfLaY BONE DISORDERS October 24: Group 9 *fractures *osteoporosis *osteopenia *Paget’s Disease *Osteogenesis Imperfecta *Osteomalacia 13 ORGAN SYSTEMS OF THE BODY: skeletal and muscular systems Muscular system All of the muscle tissues movement (voluntary and involuntary) Skeletal system: Bones (206 unique bones) Cartilage (cushions the bones) Ligaments (bone-bone connection) Protection and support Formation of blood cells (hematopoietic tissue) 14  THE MUSCULAR SYSTEM RECALL: Muscle tissues Voluntary contractions Attached to bones Striated – cross stripes 1. Skeletal muscle Involuntary contractions Tightly interconnected (intercalated disks) Contract as a group 2. Cardiac muscle Involuntary contractions No striations Function in blood vessel walls and hollow organs 15 3. Smooth muscle SKELETAL MUSCLE: FUNCTION 1. Movement 2. Posture: Body position is maintained by skeletal muscle tonic contraction, e.g. muscle tone 3. Heat production: due to breakdown of ATP Muscles produce most of the body’s heat. Fatigue occurs when ATP level gets low 16 SKELETAL MUSCLE: STRUCTURE Consists of muscle fibers and connective tissue Most skeletal muscles attach to two bones that have a movable joint between them Tendons anchor muscles firmly to bones. They are made up of strong dense connective tissue Bursae are fluid-filled sacs that lie between tendons and bone and provide lubricating fluid (synovial fluid) 17 SKELETAL MUSCLE: STRUCTURE Nucleus (note: there’s more than one in a single cell) Myocyte Muscle Cells myofiber = muscle fiber = myocyte = muscle cell 18 SKELETAL MUSCLE: STRUCTURE Bundles of muscle fibers (fascicles) are wrapped within connective tissue (perimysium) Bundles of fascicles are clustered (connective tissue) together along with blood vessels Fascia (epimysium) – loose (Fascia) connective tissue outside muscle organs; found between muscle, bone, and skin 19 myofiber = muscle fiber = myocyte = muscle cell SKELETAL MUSCLE: STRUCTURE Muscle fibers made up of thick and thin myofilaments Functional unit of the muscle fiber = sarcomere (actin + myosin) Thick myofilaments = form myosin Thin myofilaments = form actin Actin (thin myofilaments) Myosin (thick myofilaments) 20 SKELETAL MUSCLE: STRUCTURE Sarcomere- basic contractile unit of skeletal muscle Sarcomeres contract because of interactions between two proteins: myosin and actin 21 (Nature Education) SKELETAL MUSCLE: Muscle Contraction What initiates a contraction? Motor nerves of your peripheral nervous system control muscle contraction by releasing neurotransmitters on the surface of the muscle fibers. The point of contact between the nerve ending and the muscle fiber is called a neuromuscular junction. Specialized chemicals like acetylcholine (AKA: neurotransmitters) are released by the motor neuron in response to a nervous impulse. SKELETAL MUSCLE: Muscle Contraction Connecting bridges between the myofilaments only form if calcium (Ca++) is present Relaxed state – Ca++ in cell ER Stimulated muscle – Ca++ released and binds to thin filaments The contraction process requires energy (ATP) which is supplied by glucose http://www.dnatube.com/video/1952/Sliding-filament-causes-contraction-of-muscle SKELETAL MUSCLE: MUSCLE CONTRACTION 24 SKELETAL MUSCLE: MUSCLE CONTRACTION Endoplasmic Reticulum Neuromuscular Junction Actin Calcium 25 Myosin SKELETAL MUSCLE: RED VS. WHITE Red Red (Dark) Vs. White (Light) White 26 SKELETAL MUSCLE: RED VS. WHITE Myoglobin The more myoglobin (protein that binds iron and oxygen) in a muscle, the redder it is in appearance. Also, red muscle is highly vascular, so there is more blood to red vs. white muscle, thereby adding to the ‘redness’ of the red muscle 27 SKELETAL MUSCLE: RED VS. WHITE www.ingnycmarathon.org/ news/story_6.php Red muscle White muscle www.london2012.org/.../Athletics.htm www.badwater.com/.../ pamreedspot.html Long Distance Sprinting 28 SKELETAL MUSCLE: MUSCLE FIBER TYPES Muscle fiber types are classified by their contractile and metabolic characteristics: 1. Type I: Slow oxidative fibers (red) 2. Type II-A: Fast oxidative fibers (red) 3. Type II-B: Fast glycolytic fibers (white) 29 SKELETAL MUSCLE: MUSCLE FIBER TYPES Pure Type I A “ mixed” muscle fiber The % of Type I and Type II fibers per muscle are determined by our genes and gene expression… …so you can blame your mom and dad as to why you aren’t a world-class athlete!! Pure Intermediate Type II-B fibers Type II-A 30 SKELETAL MUSCLE: MUSCLE FIBER TYPES Characteristics Slow oxidative Fast oxidative Fast glycolytic (Type I) (Type II-A) (Type II-B) Diameter small intermediate large Color red pink white Contraction speed slow fast fast ATP synthesis aerobic (oxidative) aerobic (oxidative) anaerobic and anaerobic (glycolytic) (glycolytic) Vascularization/ high intermediate low/scarce capillary supply Myoglobin content high high low Mitochondria high intermediate few Fatigue resistance high intermediate low Activities endurance speed/endurance speed/sprints 31 SKELETAL MUSCLE: Exercise Skeletal muscles undergo changes that correspond to how much work they do… Atrophy – prolonged inactivity; muscles shrink Hypertrophy – increase in muscle size; enhanced by strength training Strength training – contracting muscles against heavy resistance (weight lifting); increases the # of myofilaments in each muscle fiber Endurance training (aerobic) – increases muscle’s ability to sustain exercise; increases # of blood vessels which allows for increased delivery of oxygen and glucose to the muscle SKELETAL MUSCLE FIBERS: STRUCTURE Nuclear domain of an average cell nucleus Anatomy of a muscle cell Skeletal muscle fibers are multi-nucleated A little help, please! Nuclear domain of a muscle cell 33 SKELETAL MUSCLE: GROWTH Problem: Muscle fibers normally express myostatin- a protein that naturally inhibits muscle differentiation and growth RESULT: muscle fibers and muscle fiber nuclei cannot divide Question: We know that skeletal muscle can get bigger (hypertrophy), but how does this occur? Answer: satellite cells can grow and divide! GREEN: nucleus of satellite cell Pink: cytoplasm of satellite cell Satellite cell of skeletal muscle fiber Muscle fiber nucleus within the fiber 34 SKELETAL MUSCLE: growth Satellite cells are in the G0 (resting) state until activated by external stimuli External stimulus, released by damage, can emanate from within the skeletal muscle or from nearby structures (connective tissue) The satellite cell has receptors for these stimuli that will trigger it to enter the cell cycle Daughter satellite cells and divide 1. Satellite cells can either send its nuclear components into 2.? the muscle fiber and add to the nuclear population, OR 2. Resume being a satellite cell 1. for future events 35 SKELETAL MUSCLE: growth Hypertrophy is regulated by nuclear number Satellite cell Time (weeks or months) Hypertrophy: increase in muscle cell size (volume) by increasing the nuclear number, cytoplasm and contractile elements 36 SKELETAL MUSCLE: GROWTH Myostatin- a protein that naturally inhibits muscle differentiation and growth Norwegian Blue cow …naturally occurring muscles DON’T express myostatin 37 MYOSTATIN AND MUSCLE GROWTH These block myostatin Myostatin knockout mouse…scientifically produced back Gluts Quads Shin muscle Se-Jin Lee and Alexandra C. McPherron Regulation of myostatin activity and muscle growth PNAS | 38 July 31, 2001 | vol. 98 | no. 16 | 9306-9311 MUSCULAR SYSTEM DISORDERS October 24: Group 6 *Myopathies *Disorders of muscle contraction (sarin gas poisoning, malignant hyperthermia) *Multiple Sclerosis (MS) *Amyotrophic Lateral Sclerosis (ALS) 39 Unit 5 quiz now available on Canvas: Complete by October 9 @ 11:59 pm QUESTIONS? 40