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