Nervous System: Anatomy and Function

• Human anatomy is the study of the structure of the human body
• Human physiology is the study of the function of the human body

Nervous System

• The nervous system coordinates and controls bodily activities
• The nervous system consists of the brain, spinal cord, and nerves
• Neurons are the basic functional units of the nervous system, transmitting electrical and chemical signals
• The central nervous system (CNS) includes the brain and spinal cord
• The peripheral nervous system (PNS) includes all nerves outside the CNS
• Sensory neurons transmit signals from sensory receptors to the CNS
• Motor neurons transmit signals from the CNS to muscles and glands
• The somatic nervous system controls voluntary movements
• The autonomic nervous system controls involuntary functions such as heart rate and digestion
• The sympathetic nervous system prepares the body for "fight or flight" responses
• The parasympathetic nervous system promotes "rest and digest" functions
• Neurotransmitters are chemical messengers that transmit signals across synapses

Respiratory System

• The respiratory system facilitates gas exchange between the body and the environment
• It includes the nose, pharynx, larynx, trachea, bronchi, and lungs
• The primary function is to take in oxygen and expel carbon dioxide
• The diaphragm is the primary muscle involved in breathing
• Inhalation occurs when the diaphragm contracts and the chest cavity expands
• Exhalation occurs when the diaphragm relaxes and the chest cavity contracts
• Oxygen diffuses from the alveoli into the blood
• Carbon dioxide diffuses from the blood into the alveoli
• The medulla oblongata in the brainstem controls the rate and depth of breathing
• External respiration involves gas exchange between the lungs and the blood
• Internal respiration involves gas exchange between the blood and the tissues

Cardiovascular System

• The cardiovascular system transports blood, oxygen, nutrients, and hormones throughout the body
• It includes the heart, blood vessels, and blood
• The heart is a muscular organ that pumps blood through the circulatory system
• Arteries carry blood away from the heart
• Veins carry blood back to the heart
• Capillaries are small vessels where gas exchange occurs
• The systemic circuit carries blood to and from the body tissues
• The pulmonary circuit carries blood to and from the lungs
• Blood consists of plasma, red blood cells, white blood cells, and platelets
• Red blood cells carry oxygen
• White blood cells are involved in immune responses
• Platelets help with blood clotting
• Blood pressure is the force of blood against the walls of the arteries
• Systole is the contraction phase of the heart
• Diastole is the relaxation phase of the heart

Muscular System

• The muscular system enables movement, maintains posture, and generates heat
• There are three types of muscle tissue: skeletal, smooth, and cardiac
• Skeletal muscle is voluntary and attached to bones
• Smooth muscle is involuntary and found in the walls of internal organs
• Cardiac muscle is involuntary and found only in the heart
• Muscles contract due to the interaction of actin and myosin filaments
• ATP provides the energy for muscle contraction
• Skeletal muscles are controlled by the somatic nervous system
• A motor unit consists of a motor neuron and the muscle fibers it innervates
• Muscle hypertrophy is the increase in muscle size due to exercise
• Muscle atrophy is the decrease in muscle size due to disuse or disease
• Tendons connect muscles to bones
• Ligaments connect bones to bones at joints

Digestive System

• The digestive system breaks down food into smaller molecules that can be absorbed into the bloodstream
• It includes the mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, and gallbladder
• Digestion begins in the mouth with saliva
• The esophagus transports food from the mouth to the stomach
• The stomach mixes food with gastric juices and begins protein digestion
• The small intestine is the primary site of nutrient absorption
• The large intestine absorbs water and electrolytes
• The liver produces bile, detoxifies substances, and stores glycogen
• The pancreas produces enzymes that aid in digestion and regulates blood sugar
• The gallbladder stores and concentrates bile
• Peristalsis is the rhythmic contraction of muscles that moves food through the digestive tract
• Enzymes such as amylase, protease, and lipase break down carbohydrates, proteins, and fats, respectively
• Villi and microvilli in the small intestine increase the surface area for absorption
• The rectum stores feces until elimination