MUSCLES

3 main categories of muscles : Smooth- Another name is visceral muscle Involuntary muscles- have no control over them Stomach, digestive tract, urethra, and ureters. Non-striated, smooth shape Cardiac- Myocardium Striated and branched Skeletal- Voluntary muscles Also called striated (because of its cross stripes under a microscope) Every movement we make is produced by a skeletal muscle. Give me some examples. Muscle cells are also called muscle fibers

Skeletal Muscles Made up of striated muscle fibers and connective tissue. Most attach to two bones that have a joint in between them. One of the bones is more stationary than the other. The muscle’s attachment to the more stationary bone is called its origin. The attachment to the more moveable bone is called the muscle’s insertion. The rest of the muscle is call the body of the muscle. Tendons connect the muscles to the bones... Remember... Muscles get “tender” therefore they are tendons Tendons are made up of connective tissue that is STRONG! What are connective tissue that connects bone to bone called?

Skeletal Muscles

Functions of Skeletal Muscles 1.Movement 2.Posture or Muscle Tone 3.Heat Production

Movement Muscles move bones by pulling on them. The length of the muscles gets shorter as the fibers contract. The insertion bones moves towards the origin bones. This is muscle contraction.

Voluntary Muscle Movement Muscle movement is normally smooth and free from tremors. Muscles work in coordinated teams, not singly! Prime Mover/ Agonists- muscles that is mainly responsible for producing the desired movement (think you are in agony when you get sore! ) Synergists- other muscles that help the prime mover with the desired movement Antagonists- produces the opposite movement to the prime mover. Ex. When the prime mover contracts, the antagonists relax. EX. Biceps, brachialis, and triceps muscles.

Posture We maintain our body posture because of continuous, low- strength muscle contractions called tonic contraction Tonic contraction do not create movement

Heat Production The contraction of muscle fibers produces most of the heat necessary to maintain our body temperature.

Muscle Fatigue We have all experienced muscle fatigue. Do one too many push-ups and our arms feel like tree trunks. Why does that happen? ATP = energy When we exercise, we use all the ATP in our muscles. The muscles quickly try to make more ATP which drains all of our oxygen and nutrients. When the oxygen runs low, the body switches to an energy conservation that makes lactic acid. Lactic acid is what makes our muscles sore when we’re done exercising. “Oxygen debt” is the increased metabolism that occurs for the cells to remove excess lactic acid from our cells. Labored breathing after exercise is the body’s way of “paying that debt” and replenishing our muscles of their needed oxygen. COOL!

Other Body Systems Many other body systems are involved in the muscular system: Skeletal Nervous Respiratory Circulatory All work together to make movements! What happens when the muscular, skeletal, respiratory, and circulatory systems work fine, but the nervous system is impaired?

How do muscles contract? Before a muscle can move, it has to be stimulated by nerve impulses. Muscle cells are stimulated by a nerve fiber called a motor neuron. The point of contact between the motor neuron and the muscle fiber is the neuromuscular junction. Muscles do not contract until the stimulus reaches a certain level of intensity. The minimal level of stimulation required to cause a muscle fiber to contract is called the threshold stimulus. Once the threshold stimulus has been met, the muscle fiber contracts. It’s either “all or none”. Either the threshold has been met or it hasn’t. Let’s Play Jenga!

Muscle Memory Muscle memory is the concept that once you learn to do something, when you do it again, it becomes easier. Your muscles “remember” how to do that movement. Now just because each individual muscle fiber contracts at an “all or nothing” unit, NOT EVERY SINGLE MUSCLE fiber contracts at the same time. This is why when you pick up a book you use less force than if you were picking up a table. Your muscles (and nervous system) remembers what a book should weigh or how much a table should weigh and automatically contracts the appropriate amount of muscle fibers. OUR BODY IS SO COOL!!!

Types of Skeletal Muscle Contraction 1.Twitch- quick jerky response to a stimulus (eye twitch) 2.Tetanic- rapid series of stimuli bombarding the muscle all at once (cramp) 3.Isotonic- contraction of the muscle that causes the muscle to change length (bicep curl) 4.Isometric- contracting of the muscle that does not cause a change in length, but causes increased tension (planking)

Effects of Exercise Atrophy- muscles shrink due to inactivity Hypertrophy- muscles increase because of exercise

Muscle Movement Flexion-makes the joint angle between two bones smaller Extension- makes the joint angle larger/ opposite of flexion Abduction- moving a body part away from the body Adduction- moving a body part towards the body Rotation-movement along a longitudinal axis (shaking your head no) Supination & Pronation- both are hand positions as the forearm turns. Supination means hands up, Pronation means hands down (supine is laying face up, prone is laying face down). Dorsiflexion & Plantar Flexion- refer to ankle movements. Dorsiflexion- toes are pointing upwards, Plantar flexion- toes are pointed downward

Muscles of the Head and Neck These are the muscles of facial expressions! Smile, frown, etc. Frontal- raise your eyebrows Orbicularis Oris- kissing muscle, puckers your lips Orbicularis Oculi- closes your eyes Zygomaticus- Smiling muscle Masseter- helps with chewing, elevates the mandible Temperol- assists in closing the jaw Sternocleidomastoid-rotates and flexes head and neck Trapezius- extends head and neck

Upper Extremities Muscles Pectoralis major- chest muscle Latissimus dorsi- lower back Deltoid- shoulder Biceps brachii- primary flexor of the forearm Triceps brachii- extensor of the elbow

Abdominal Muscles Rectus abdominis- runs down the middle of your abdomen from the thorax to the pubis. External Oblique- outermost layer of your abdomen- on your side

Lower Extremities Muscles Iliopsoas (il-ee-o-SO-us) (“p” is silent)- muscle that is deep in the pelvis. Originates on the lower vertebrae and inserts on the lesser trochanter on the femur. Flexes the thigh, stabilizes the trunk, helps with sit-ups. Sartorius- origin at the iliac crest and travels all the way to the top of the tibia! Longest muscles in our body! Helps flex, adduct, and rotate the hip. Gluteus maximus- butt muscle

Lower Extremities Muscles Adductor Group- inner thigh muscles. Made up of multiple muscles that originate on the bony pelvis and insert on the femur. Responsible of pressing the thighs together Hamstring Group- back of upper leg. 3 muscles working together that serve as flexors of the lower leg. They originate on the ischium and insert on the tibia or fibula.

Lower Extremities Muscles Quadriceps Group- top of upper leg. 4 thigh muscles. Extend the lower leg Tibialis anterior- on the front of the shin. Dorsiflexes the foot. “Shin splints”. Gastrocnemius- calf muscle. Plantarflexes the foot. “Toe dancer’s” muscle

Peroneus Group Peroneus Group- group of 3 muscles found along the sides of the lower leg. Soleus- is under the gastrocnemius Peroneus Longus- outside, Peroneus Brevis- inside