The Central Nervous System The central nervous system (CNS) consists of the spinal cord and brain. The CNS receives and sends sensory input and coordinates motor output. 17-1 Central Nervous System 17-2 The human brain 17-3 Fig. 49-15 Frontal lobe Parietal lobe Speech Frontal association area Somatosensory association area Taste Reading Speech Hearing Smell Auditory association area Visual association area Vision Temporal lobe Occipital lobe The Cerebral Cortex The cerebral cortex is a thin, highly convoluted outer layer of gray matter covering both hemispheres. 17-5 Parts of the Brain Cerebrum is the forebrain • Contains two hemispheres for coordinating sensory and motor information • Speech, reasoning, memory, personality, may be located on one side only Cerebral hemispheres 17-7 Cerebrum (Forebrain) Continued - The two hemispheres are connected by the corpus callosum allowing info to be shared between the hemispheres The cerebrum can be subdivided into 4 lobes 1. Frontal (walking, speech, intellect, judgment, personality), 2. Temporal (hearing, smell, memory, interpretation), 3. Parietal (interpreting sensory info receptors, spatial understanding) and 4. Occipital (vision) lobes Cerebrum Parts and Functions 17-9 Speech Centers in Cerebrum -Broca’s area - part of the left hemisphere where speech center is located -part of the frontal lobe -Wernicke’s area – understanding speech; located in the temporal lobe 17-10 The lobes of a cerebral hemisphere 17-11 Other Parts of the Brain • Brainstem: thalamus, pons, medulla Pons and medulla control heart rate and respiratory rate • Cerebellum- balance and coordination • Limbic System: memory, emotions, and emotional memory Older Brain Structures The Brainstem Older Brain Structures The Thalamus • Thalamus –All the senses EXCEPT smell Older Brain Structures The Cerebellum • Cerebellum –“Little brain” -Controls balance, agility, and voluntary movement with the pons Older Brain Structures The Limbic System • Limbic System –Hippocampus is involved with memory Older Brain Structures The Limbic System: The Amygdala • Amygdala –Aggression, fear, & emotional memories and Older Brain Structures The Limbic System: The Hypothalamus • Hypothalamus –Influence on the pituitary gland The Spinal Cord The spinal cord extends from the base of the brain through the vertebral canal. A central canal holds cerebrospinal fluid. Gray matter of the spinal cord forms an “H” and contains neurons White matter consists of nerve fibers called “tracts” to and from the brain 17-19 Spinal cord 17-20 17-21 Functions of the Spinal Cord -The spinal cord is the center for many reflex arcs. -It sends sensory information to the brain and receives motor output from the brain to the peripheral nerves for both control of voluntary skeletal muscles and involuntary internal organs. -Severing the spinal cord produces paralysis. 17-22 Reflex Arc 17-23 The Peripheral Nervous System The peripheral nervous system (PNS) contains nerves to the whole body -Sensory nerves carry information to the CNS, motor nerves carry information away -Humans have 12 pairs of cranial nerves and 31 pairs of spinal nerves. 17-24 Cranial nerves 17-25 Spinal nerves 17-26 Somatic System The somatic system means nerves to the skin and skeletal muscles 17-27 Autonomic Nervous System • All autonomic nerves are motor nerves that regulate the organs of the body without conscious control; involuntary • Control exists in the medulla • They work on smooth muscle (digestive system), cardiac muscle (heart) and glands (exocrine & endocrine) • Responsible for maintaining homeostasis during times of rest and during emergencies Consists of two parts: Sympathetic – prepares the body for stress, including “fight or flight” response Parasympathetic – restores normal balance; times of relaxation – Functions are opposite those of the sympathetic nervous system Fig. 49-8 Sympathetic division Parasympathetic division Action on target organs: Action on target organs: Constricts pupil of eye Dilates pupil of eye Stimulates salivary gland secretion Inhibits salivary gland secretion Constricts bronchi in lungs Cervical Sympathetic ganglia Relaxes bronchi in lungs Slows heart Accelerates heart Stimulates activity of stomach and intestines Inhibits activity of stomach and intestines Thoracic Stimulates activity of pancreas Inhibits activity of pancreas Stimulates gallbladder Stimulates glucose release from liver; inhibits gallbladder Lumbar Stimulates adrenal medulla Promotes emptying of bladder Promotes erection of genitals Inhibits emptying of bladder Sacral Synapse Promotes ejaculation and vaginal contractions