Chapter 49

• The simplest animals with nervous systems, the cnidarians, have interconnected neurons arranged in nerve nets
• More complex animals have nerves, in which axons of multiple neurons are bundled together
• Bilaterally symmetrical animals: cephalization
• central nervous system (CNS): brain and longitudinal nerve cords
• peripheral nervous system (PNS): neurons carrying information into and out of the CNS
• In vertebrates, the CNS is composed of the brain and spinal cord
• In vertebrates, the PNS is composed of nerves and ganglia
• Region specialization is a hallmark of both the CNS and PNS
• The CNS develops from the hollow dorsal nerve cord
• The canal of the spinal cord and ventricles of the brain fill with cerebral spinal fluid
• The brain and spinal cord contain gray matter and white matter
• Gray matter consists mostly of neuron cell bodies
• White matter consists of bundled axons
• A reflex is the body's automatic response to a stimulus
• The PNS transmits information to and from the CNS and regulates movement and the internal environment
• In the PNS, afferent neurons transmit information to the CNS, and efferent neurons transmit information away from the CNS
• The sympathetic division regulates arousal and energy generation (“fight-or-flight” response)
• The parasympathetic division has antagonistic effects on target organs and promotes calming and a return to “rest-and-digest” functions
• Glial cells, or glia, have numerous functions to nourish, support, and regulate neurons
• Specific brain structures are particularly specialized for diverse functions
• The vertebrate brain has three major regions: the forebrain, midbrain, and hindbrain
• The forebrain has activities including processing of olfactory input, regulation of sleep, learning, and any complex processing
• The midbrain coordinates routing of sensory input
• The hindbrain controls involuntary activities and coordinates motor activities
• The brainstem and cerebrum control arousal and sleep
• Sleep is an active state for the brain and is essential for survival.
• Cycles of sleep and wakefulness are examples of circadian rhythms, daily cycles of biological activity
• In mammals, circadian rhythms are coordinated by a clustered neurons in the hypothalamus called the suprachiasmatic nucleus (SCN)
• ▪ Generation and experience of emotions involve many brain structures, including the amygdala, hippocampus, and parts of the thalamus
• the amygdala, hippocampus, and parts of the thalamus are grouped as the limbic system
• Storage and recall of emotional memory are dependent on the amygdala
• Positron-emission tomography (PET) enables a display of metabolic activity through injection of radioactive glucose
• Today, many studies rely on functional magnetic resonance imaging (fMRI), in which brain activity is detected through changes in local oxygen concentration
• The cerebrum, the largest structure in the human brain, is essential for language, cognition, memory, consciousness, and awareness of our surroundings
• Four regions, or lobes (frontal, temporal, occipital, and parietal), are landmarks for particular functions
• The cortex consists of sensory areas, association areas, and motor areas
• Studies of brain activity have mapped areas responsible for language and speech
• Patients with damage in Broca’s area in the frontal lobe can understand language but cannot speak
• Damage to Wernicke’s area causes patients to be unable to understand language, though they can still speak
• Frontal lobe damage may impair decision making and emotional responses but leave intellect and memory intact