1. The Muscular System

2. The Muscular System Muscle tissue found everywhere in the body
Tendons connect muscle to bone

3. Muscle Types
Three types of muscle tissue – skeletal, smooth, and cardiac
Smooth
Skeletal
Cardiac

4. Skeletal Muscle
Usually attached to bones and are responsible for voluntary movement (voluntary muscle)
Striated/striped – light and dark bands
Cells very large with many nuclei

5. Smooth Muscle Muscles not under voluntary control (involuntary muscle)
One nucleus in cells and not striated
Found in organs and blood vessels
Helps move food through digestive tracts, decrease size in pupils, as well as operate other organs in the body

6. Cardiac Muscle Muscle found in heart
Small, striated cells with one to two nuclei
Involuntary muscle found ONLY in the heart

7. Muscle Bundle of Nuclei muscle fibers Single muscle fiber (cell)
Figure 27.31
Muscle
Bundle of
muscle fibers
Nuclei
Single muscle fiber
(cell)
Myofibril
Light
band
Light
band
Dark band
Sarcomere
Thick
filaments
(myosin)
TEM
Light
band
Dark band
Light
band
Thin
filaments
(actin)
Sarcomere

8. Muscle Contraction
Striations in skeletal muscle cells are formed by alternating patterns of thick and thin filaments
Thick filaments = myosin protein
Thin filaments = actin protein
Tiny myosin and actin filaments are the force-producing engines that cause muscles to contract
A muscle contracts when the thin filaments (actin) slide over the thick filaments (myosin)
Myosin forms cross-bridge with actin and pulls the actin, making the muscle contract
Energy for muscle contraction is supplied by ATP

9. Muscle Contraction (continued)
Relaxed Muscle
Myosin
Actin
Z disc
Movement of Actin Filament
Actin
Cross-bridge
Sarcomore
Binding sites
Contracted Muscle
Myosin
Cross-bridges
Z disc

10. Motor Neurons: Control of Muscle Contraction
are part of the central nervous system,
release neurotransmitters that cause muscle muscle fibers to contract, and
can branch to a number of muscle fibers.
A motor unit consists of
a neuron and
all the muscle fibers it controls.

11. Muscle Contraction (continued)
Contraction of a single muscle fiber is an all-or-none process – either the fiber completely contracts or it doesn’t
The NUMBER of fibers stimulated by the nervous system to contract varies with the amount of work/strength needed
Muscle fatigue caused by not enough ATP getting to muscle
Lactic cid fermentation kicks in = burning sensation in muscles

12. How Muscles and Bone Interact
Individual muscles can only PULL in one direction, so how does your arm move in two directions?
Skeletal muscle is joined to bones by tendons, which pull on bones and make them work
Several muscles surround each bone joint to allow pulling in different directions

13. How Muscles and Bone Interact (continued)
Muscles work in opposing pairs – when one contracts, the other relaxes. Ex. Upper arm with biceps and triceps
Biceps contracts = bend elbow (triceps relaxes)
Triceps contracts = extend elbow (biceps relaxes)
Exercise is important to keep muscles firm and working properly; however, too much exercise all at once can tear and stress muscles and be painful

14. Opposing Muscle Pairs Movement Movement Biceps (relaxed)
Biceps (contracted)
Triceps (contracted)
Triceps (relaxed)

15. The Skin

16. The Skin – aka Integumentary System
Largest sense organ in the body – deals with the sense of touch

17. Functions of the Skin
Regulate internal body temperature (warming, cooling, sweating, etc.)
Block the sun’s radiation with melanin
Sense organ
Produces essential vitamins – Vitamin D
Protective layer to underlying tissues (invasion of microbes, chemicals, etc.)

18. Two Layers of the Skin Epidermis Dermis
Outermost layer – dead cells slough off
Has melanin pigments = skin color
Dermis
Innermost layer
Helps insulate body
Contains blood vessels, nerves, nerve endings, sweat glands, hair follicles, oil glands

19. Two Layers of the Skin Nerves Hair Sweat pore Hair follicle
Epidermis
Dermis
Subcutaneous layer
Muscle
Sweat gland
Fat
Sebaceous gland