17-1 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.

Central Nervous System 17-2

17-3 The human brain

Fig Speech Occipital lobe Vision Temporal lobe Frontal lobe Parietal lobe Somatosensory association area Frontal association area Visual association area Reading Taste Hearing Auditory association area Speech Smell Motor cortex Somatosensory cortex

17-5 The Cerebral Cortex The cerebral cortex is a thin, highly convoluted outer layer of gray matter covering both hemispheres.

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

17-7 Cerebral hemispheres

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

17-11 The lobes of a cerebral hemisphere

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, and fear, & emotional memories

Older Brain Structures The Limbic System: The Hypothalamus Hypothalamus –Influence on the pituitary gland

17-19 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

17-20 Spinal cord

17-21

17-22 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.

Reflex Arc 17-23

17-24 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.

17-25 Cranial nerves

17-26 Spinal nerves

17-27 Somatic System The somatic system means nerves to the skin and skeletal muscles

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 Stimulates glucose release from liver; inhibits gallbladder Dilates pupil of eye Parasympathetic division Sympathetic division Action on target organs: Inhibits salivary gland secretion Accelerates heart Relaxes bronchi in lungs Inhibits activity of stomach and intestines Inhibits activity of pancreas Stimulates adrenal medulla Inhibits emptying of bladder Promotes ejaculation and vaginal contractions Constricts pupil of eye Stimulates salivary gland secretion Constricts bronchi in lungs Slows heart Stimulates activity of stomach and intestines Stimulates activity of pancreas Stimulates gallbladder Promotes emptying of bladder Promotes erection of genitals Action on target organs: Cervical Sympathetic ganglia Thoracic Lumbar Synapse Sacral