Parts and functions Brain Cerebrum: The largest part of the brain, responsible for higher brain functions such as thought, memory, sensation, voluntary movement, and reasoning. Cerebellum: Located under the cerebrum, it coordinates muscle movements and maintains posture, balance, and equilibrium. Brainstem: Connects the brain to the spinal cord and controls vital functions like heart rate, breathing, and blood pressure. It includes: Midbrain: Controls vision, hearing, motor control, sleep/wake cycles, and arousal. Pons: Relays signals between the cerebrum and cerebellum; involved in sleep and breathing. Medulla Oblongata: Controls autonomic functions like heartbeat, breathing, and digestion. Thalamus: Relays sensory and motor signals to the cerebral cortex; involved in consciousness, sleep, and alertness. Hypothalamus: Regulates body temperature, hunger, thirst, and the autonomic nervous system; controls the pituitary gland. Spinal Cord: A long, thin bundle of nerve fibers that extends from the brainstem down the spine, transmitting information between the brain and the rest of the body. Peripheral Nervous System Somatic Nervous System: Cranial Nerves: 12 pairs of nerves that originate from the brain and control functions in the head and neck, such as sensory input and motor control. Spinal Nerves: 31 pairs of nerves that originate from the spinal cord and control sensory and motor functions in the body. Autonomic Nervous System (ANS): Sympathetic Nervous System: Prepares the body for stressful or emergency situations (fight or flight response); increases heart rate, dilates pupils, inhibits digestion. Parasympathetic Nervous System : Promotes rest and digestion; decreases heart rate, constricts pupils, stimulates digestion. Enteric Nervous System: Sometimes considered part of the ANS, it controls the gastrointestinal system, regulating digestion, nutrient absorption, and waste elimination.