Muscle Anatomy
Anatomy and Physiology L2/L3
Lets Review!!What type of muscle tissue does each describe?
Long, thin & multinucleated
Striated Involuntary Contracts
rhythmically Found in cardiac
tissue
Voluntary Contractions are slow
and steady Walls of visceral
organs & blood vessels
Contract rapidly & vigorously
Functions of skeletal muscle
Movement: of skeleton by use of muscles acting in pairs or groups
Posture Maintenance: keeping upright
Heat generation: product of movement. Serves to maintain norm. body temp (homeostasis)
Gross Anatomy of skeletal muscle
muscle cell aka (fiber): made up of many myofibrils
Epimysium (deep fascia: outer, toughest covering of Dense connective tissue
Fascicles/fasciculus :name given to bundles of muscle fibers/cells
Anatomy of skeletal muscle
Anatomy of skeletal muscle (cont)
Myofibril: many make up a cell/fiber
Sarcolemma (plasma
membrane): it is the cell membrane surrounding cell/fiber
SR: similar to ER Sarcomere:
contractile units making up myofibrils containing actin &myosin.
-Multi-nucleated
Myofibril: many sarcomeres make up the myofibrils
Thread-like protein structures
2 types: Thick– Myosin Thin – Actin Alternating light/dark
create striations Allow muscle to
contract (shorten) and relax (lengthen)
Contaction and Relaxation of Skeletal Muscle fiber
Chemical Part of Muscle Contraction: Motor Unit: Composed of motor neuron & all the muscle fibers
NM Jxn Terminal
end stores ACh
ACh released into fiber
ACh acts as stimulus
Steps in Muscle Contraction
1. Nerve impulse travels down motor neuron to NM junction
2. Acetylcholine (ACh) released into muscle
3. ACh diffuses across muscle fiber4. Signals the SR to release stored
Calcium5. Ca initiates formation of cross bridges
between Actin and Myosin *Ca stimulates a change in actin shape6. sacrcomeres shorten and muscle fibers
contract
Steps in Muscle Relaxation
1. Motor neuron impulse to stop contraction so Ach is inactivated.
2. Ca moves (Active transport) back into SR (to be stored) (*ATP)
3. Absence of Ca causes crossbridges to break because actin changes back its shape (*ATP)
4. Actin filaments slide back RESULT: Muscle relaxes
Homework: #1and #2
#1 Based on knowledge of muscle physiology; what steps must or do not occur in the condition Rigor Mortis at the chemical level and what happens to the body?
#2. What causes Botulism?and how might we (humans) come in contact with the toxin?
What physiological/chemical effects can Botulism have? What treatments?
Homework: #3 and #4
#3. Look up compartment syndrome1. Cause: what happens at the chemical level?2. symptoms3. Treatment
#4. Look up multiple sclerosis Be able to discuss:1. Cause; and what happens at the chemical level?2. symptoms3. treatment
Homework: #5 Muscular Dystrophy
Protein structure of muscle is mainly Actin & Myosin.
What is the function of dystrophin? Muscular Dystrophy? Cause: at the chemical level? Types? Physiological effects on body
Take a Break and Review!
Go to following animation www.brookscole.com/chemistry_d/te
mplates/student_resources/shared_resources/animations/muscles/muscles.html
Great animations and review activities!
Quick Quiz: 18 pts (3 each)
1. Describe each: epimysium, fascicles, fiber/cell, sarcoplasm
2. Explain where the sarcomere is and what is has to do with muscle contraction
3. What has to happen in order for a body part to move?
Quiz cont.
4. What happens at the neuromuscular junction?
5. Explain steps in muscle contraction
6. Explain steps in muscle relaxation