3.8 – The Musculoskeletal System The organ system that is made up of bones and skeletal muscle; the system that supports the body, protects delicate organs, and makes movement possible

musculo  muscles that make your body move skeletal  all the bones that make up your body The musculoskeletal system provides structure and support for the body and enables movement. (See Figure 1, pg 99)

Structural Features The skeleton contains three types of connective tissue: bone, ligaments, and cartilage. Bone tissue is hard and dense. Ligaments are tough, elastic connective tissues that hold bones together at the joints. Cartilage is a dense connective tissue that provides a strong, flexible, low-friction support for bones and other tissues. Muscles contain muscle tissue and are connected to bones by special tissues called tendons.

How Muscles Make Bones Move Each end of a skeletal muscle is connected by tendons to one or more different bones in the skeleton. Muscle cells and tissues can contract, causing the bones to move. Skeletal muscles always work in opposing pairs or groups. (See Figure 5, pg 100)

Problems with Musculoskeletal System Loss of bone tissue due to osteoporosis makes bones more susceptible to fractures. (See Figure 6, pg 101) Osteoporosis is linked to a loss of calcium in the bones, so women are encouraged to consume foods containing calcium and vitamin D. Physical exercise can also help increase bone mass.

The Skeletal System of Other Animals Many invertebrates have exoskeletons to protect their internal organs. Muscles attached inside the exoskeleton enable the animal to walk, fly, eat, etc.

3.10 – The Nervous System Nervous system: The organ system that is made up of the brain, the spinal cord, and the peripheral nerves; the system that senses the environment and coordinates appropriate responses

Structural Features The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of nerves that connect all parts of the body with the central nervous system. The peripheral nervous system can be further divided into three groups: • nerves that control the voluntary muscles • nerves that carry information from the sensory organs, such as the eyes, ears, taste buds, and touch receptors, to the brain • nerves that regulate involuntary functions such as breathing, heartbeat, and digestion. The central nervous system is protected by bones and cerebrospinal fluid.

Nerve Tissue Nerves are made up of bundles of neurons, each surrounded by connective tissue. Neurons send information throughout the body by conducting electrical impulses from one area of the body to another. (See Figure 3, pg 105)

Sensory Receptors The body has millions of sensory receptors (eyes, ears, mouth, nose, muscles, and skin) that receive information from the environment. The peripheral nervous system sends this information to the central nervous system.

Communication, Coordination, and Perception The main functions of the nervous system are communication and coordination of body activities. This allows the body to respond to both the outside world and the internal environment. The brain is also responsible for our perception: interpreting or making sense of all the information we receive from our environment. The spinal cord is responsible for reflexes – actions that do not require the brain; they occur without conscious thought.

Diseases and Disorders of the Nervous System Diseases and injuries can cause serious damage to the nervous system. Multiple Sclerosis is a disease that destroys the myelin sheaths of neurons in the central nervous system. Symptoms include: muscle weakness, slurred speech, and difficulty walking. Physical trauma can cause sever damage to the spinal cord that can even result in paralysis. A CT scan or MRI scan are used in situations where doctors suspect brain injury. (See Figure 8, pg 107)