Chapter 14: Muscles and Movement

Subdivision of the motor division of PNS

1) Somatic division - controls skeletal muscle

2) Autonomic division - controls smooth muscle, cardiac muscle, and glands

• Involuntary actions such as moving food down the digestive tract or heart rate are part of the autonomic division 

Somatic

skeletal muscle

• reflex’s, pupil dilation/constriction in the eye, yawning

• voluntary: running writing

Proprioception

sensory neurons send our brain info about location, movements, and actions of the body

Cerebellum 

Region of our brain that info gathered by sensory neurons about body position is processed. 

Tendons

very strong connective tissues, and are surrounded by a sheath made of connective tissue to reduce the friction that results from movement

What is the structure of myofibril?

bundles of linear protein scaffolds that make up muscle cells

Fascicles 

structure of muscle cells that are bundled together 

Hypertrophy

Enlargement of muscle tissue from an increase in cell size

• Muscle cells increase the # of myofibrils within them, not because more muscle cells are made

Atrophy

myofibrils break down and your muscle cells get smaller and weaker

Motor Neurons 

PNS neurons that receive CNS output information and carry signals to muscle cells instead of neurons 

sensory signals > Brain/spinal cord (CNS) > motal neurons > muscle

Myosin

Motor protein for contraction, uses ATP

Sarcomere

Functional unit of striated muscle

• contains actin and myosin

Myofibril 

Contains sarcomeres, rode like tissues in muscle cells 

Slow Twitch Muscle Cells

Tyle I

• pinkish

• specialized for aerobic ATP production

• smaller but can contract for long periods of time

• higher concentration of mitochondria are surrounded by capillaries

• can also temporarily store oxygen (reducing lactic acid build up)

• When trained muscles don’t increase in size

  • # of mitochondria increase and capillary network expands

Fast-Twitch Muscle Cells

Type II

• Larger, white

• more myofibrils

• powerful rapid contractions,

• greater force but shorter burst

• lower number of mitochondria and blood supply

• Instead rely on creatine phosphate and anaerobic respiration of gluclose for ATP production

• store creatine and glycogen for a quick source of energy

Oxidative Muscle 

Type III

Equal balance between fast and slow twitch 

both aerobically and anaerobically inclined 

Muscle Properties and Energy Requirements

ATP direct - 10 seconds

Creatine - 30 seconds

Glyocen - 3-5 minutes

^ cells do this first through aerobic respiration then anaerobically when oxygen delivery can no longer keep up with muscle demand