Tuesday, Oct. 7 - The Human Body -Skeletal Muscular and Nervous System

The skeletal, muscular and nervous systems work together to allow your body to react to the world you encounter every day

Skeletal System

The skeletal system is a framework of bones that provides structure to your body and protects internal organs. Skeleton also serves as reservoir for the storage of minerals, produces blood cells and allows movement of the body.

Human skeletons have 206 bones. – spine supports skull and moves back; Ribs protect internal organs, bones in hand allow for many tasks.

Bones are living, growing tissue. If a bone breaks, one kind of bone cell breaks down damaged tissue and one type of bone cells rebuild the bone. Outside of the bone is hard and the inside is filled with soft tissue called marrow, which is where blood cells are made. You actually have red and yellow bone marrow running through the center of the long bones (legs and arms). Red bone marrow makes red blood cells, which transport oxygen throughout the body, and some white blood cells, which fight disease. Yellow bone marrow is made up of fat that are a source of fat.

Bones are all different shapes and sizes:

• Long bones (legs and arms)
• Short bones (fingers and toes)
• Flat bones (skull and pelvis)
• Irregular bones (backbone and ears)

Joints are where bones meet. There are tough strands of connective tissue (ligaments) which connect the bones. Bones at joints are covered in cartilage, which protects them from rubbing against each other. There are:

• Ball and socket joints (shoulders, hips)
• Hinge joints (elbows, knees)
• Gliding joints (wrists, ankles, move in many direction)
• Pivot joints (between vertebrae in the spine)
• Fixed joints (skull, no movement)

The Muscular System

Skeletal and muscular systems are interrelated. The muscular system uses muscles to move the bones of the skeletal system. Muscles contract when the fibers shorten and pull together – this is what lets you walk and run and throw.

You have voluntary muscles are the muscles you chose to control – they are connected to bones by tendons – bands of strong connective tissue. Muscles can only contract, so all joints are controlled by opposing muscles. Involuntary muscles in the lungs, intestines, bladder, blood vessels and heart function without you doing them.

The Nervous System

Muscles move in response to signals that travel through the nervous system – the brain, spinal cord and specialized nerve cells called neurons. You decide to move your arm, and your brain sends a nerve impulse down the spinal cord; it hits the muscle and make it contract.

The spinal cord consists of nerve fibers that that send impulses to and from the brain. Sometimes spinal cord functions as an emergency defense system without the brain when it would take too long for the message to get to the brain. Think touching a hot stove – how fast you pull away.

The brain contains 90 percent of the neurons in the body and controls all the actions except reflex responses. Different portions of the brain control different body functions.

At the base of the brain is:

• Cerebellum (controls coordination, posture, balance)
• Medulla Oblongata (involuntary functions like digestion)
• Pons (controls rate of breathing and relays signals between cerebellum and cerebrum)

The cerebrum is the large structure at the top of the brain. It controls motor coordination and interpretation of sensory information. There are four lobes:

• Frontal lobe regulates voluntary movements, decision-making, problem-solving
• Temporal lobe regulates memory, emotions, language
• Parietal lobe process signals from the body
• Occipital lobe is involved with sight and visual meeting