The Nervous System Divisions of the Nervous System Central versus Peripheral Central Brain and spinal cord Peripheral Everything else Somatic versus Autonomic Somatic Nerves serving conscious sensations and skeletal muscles Autonomic Nerves serving vegetative functions, smooth muscles. Branches of the Autonomic Nervous System Sympathetic Branch prepares the body for emergency action Parasympathetic Branch serves the more vegetative existence. But this division is over-simplified; sometimes the two branches cooperate. 1
Functions of the Spinal Cord Convey sensory inputs to other levels of the spinal cord and to the brain. Convey motor commands from the brain and spinal cord to motor neurons. Provide local command and control for coordinated movement (mediate the spinal reflexes). The Brain The picture to right shows the human brain bisected along the midline. Major Parts of the Brain The brainstem looks like the stem of a head of cabbage. The midbrain The forebrain divided into the two cerebral hemispheres 2
Major Parts of the Brainstem The Medulla The Pons The Cerebellum (not shown) The Reticular Formation [Note: Picture shows some higher levels of the brain as well] The Medulla Lowest part of the brain Includes sensory and motor tracts connecting brain and spinal cord. Basic physiological functions Heart rate Blood pressure Respiration The Pons About 90% of sensory- and motor-tract fibers cross to the opposite side of the brain here. Centers involved in sleep/waking. Connections to cerebellum. 3
The Cerebellum Large structure hanging off back of pons. Balance, smooth motor coordination. Certain types of motor learning involve this structure. The Reticular Formation Located along the central core of the brainstem and midbrain. Serves to regulate arousal. The Midbrain Structures here are involved in visual and auditory reflexes, the modulation of pain, and other functions. 4
The Forebrain or Diencephalon Here the brain divides into two distinct halves. Some important structures include Hypothalamus Thalamus Basal Ganglia Limbic System Cerebral Hemispheres The Hypothalamus Basic drives hunger, thirst, sex drive Body temperature regulation Upper end of the autonomic nervous system. Controls the output of the pituitary gland (the so-called master endocrine gland). The Thalamus Major relay station between the lower brain and the cerebral cortex. Located just above the hypothalamus. Crucial for conscious experience. 5
The Basal Ganglia Involved in motor control and coordinated movement. Damage here can produce strange behavior, e.g., hemiballism. Loss of certain inputs from the brainstem produces Parkinson s Disease. The Limbic System This is a major component of the emotion circuitry of the brain. Structures include the septum, amygdala, hippocampus, and hypothalamus, with connections to the frontal lobes of the cortex. The Cerebral Cortex Divided into two hemispheres Each has four lobes: Frontal lobe Parietal lobe Occipital lobe Temporal lobe 6
Frontal Lobe Planning Movement (motor strip at rear) Speech production (Broca s area) Social inhibitions Integration of reasoning and emotion Parietal Lobe Touch (somato-sensory strop at front) Sense that body belongs to self Recognition Spatial orientation -- wayfinding Occipital Lobe Located in the back of the cortex. Mainly devoted to vision. 7
Temporal Lobe Hearing Language comprehension (Wernicke s area) Storing of long-term memories (hippocampus) The Corpus Callosum Large bundle of nerve fibers (about 2 million) connecting the two cerebral hemispheres. Integrates the information being processed in the two hemispheres. Severing creates two separately conscious minds (!) 8