THE NERVOUS SYSTEM made up of the brain, spinal cord, and peripheral nerves. senses the environment and creates a response. Central Nervous System (CNS) brain and the spinal cord protected from injury by bones and cerebrospinal fluid 2. Peripheral Nervous System (PNS) nerves that carry the signals between the CNS and body. relays instructions from brain to other parts of the body Reflexes - actions that do not require the brain: spinal cord acts as a short cut for reflexes.

NERVES bundles of special cells called neurons, surrounded by connective tissue send information around the body using electrical signals. approximately 100 billion neurons in the human brain. Sensory receptors - special cells that receive input from the environment and send signals to CNS Information from different sensory receptors goes to specific parts of the brain YouTube - Nerve impulse Animation

THE MUSCULOSKELETAL SYSTEM all of the bones and muscles supports the body and protects organs. Skeleton: consists of bones, ligaments, and cartilage (three types of connective tissue).

2. Muscles consists of bundles of long cells called muscle fibres contain specialized proteins that contract (controlled by nerve cells). 3 kinds: skeletal muscles - attached to the bone by tendons. smooth muscles - located in the intestines cardiac muscles - heart. Osteoporosis: disease that involves the loss of bone tissue, makes bones weak and brittle. common among older women.