Chapter 2 The Biological Foundations of Behavior chapter preview Our nervous system plays a vital role in how we think, feel, and act. Neurons , the basic building blocks of the body's circuitry, receive signals through their branching dendrites and cell bodies and transmit electrical impulses down their axons. Chemical messengers called neurotransmitters cross the tiny synaptic gap between neurons and pass on excitatory or inhibitory messages. The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of the skeletal nervous system, which controls the voluntary movements of our skeletal muscles, and the autonomic nervous system, which controls the glands and the muscles of our internal organs.
Hormones released by endocrine glands affect other tissues, including the brain.
Evolution has elaborated new brain systems on top of old. Within the brainstem are the oldest regions, the medulla and the reticular formation. The thalamus sits atop the brainstem and the cerebellum extends from the rear. The limbic system includes the amygdala, the hippocampus, and the hypothalamus. The cerebral cortex, representing the highest level of brain development, is responsible for our most complex functions.