Chapter 7 The Nervous System

Organization of the Nervous System Central Nervous System Referred to CNS Brain and Spinal cord Integrative control center Peripheral Nervous System Referred to PNS Nerves that extend outside the brain and spinal cord to the body’s extremities Communicates between the CNS and the rest of the body

Regions of the Brain Cerebrum Diencephalon Cerebellum Midbrain * Pons * Medulla Oblongata * * Found in Brain Stem

Cerebral Hemispheres (Cerebrum) Largest part of brain Include more than half of the brain mass Controls higher mental functions; conscious mind; MAKES US HUMAN Allows us to sense, to communicate, to remember, and to understand, and initiate voluntary movements. Outer layer of cerebrum (cerebral cortex) is made of gray matter - Folded surface increases surface area - Elevated ridges (gyri) - Shallow depressions (sulci) - Deep Grooves (fissures)

Cortex Roadmap Gyri - ridges Sulci – shallow grooves Fissures – deep groves

Lobes of the Cerebrum Surface lobes of the cerebrum Frontal lobe Parietal lobe Occipital lobe Temporal lobe

Sensory and Motor Areas of the Cerebral Cortex

Specialized Areas of the Cerebrum

Layers of the Cerebrum Gray matter Outer layer Composed mostly of neuron cell bodies Includes regions of the brain involved in muscle control, sensory perceptions, like seeing and hearing, memory, emotions and speech

Layers of the Cerebrum White matter Contains mainly long, myelinated axons Involved in the relay of sensory information from the rest of the body to the cerebral cortex Figure 7.13a

Diencephalon Sits on top of the brain stem Enclosed by the cerebral hemispheres; well-hidden brain region Made of three parts Thalamus Hypothalamus Epithalamus

Thalamus The relay station for sensory impulses (switchboard) Transfers impulses to the correct part of the cerebrum for interpretation All incoming impulses get sorted here first and identified as pleasant or non-pleasant

Hypothalamus Under the thalamus Contains brain stem and controls organs by maintaining homeostasis Important autonomic nervous system center Helps regulate body temperature Controls water balance Regulates metabolism An important part of the limbic system (emotions) The pituitary gland is attached to the hypothalamus

Hypothalamus An important part of the limbic system (emotions) The pituitary gland is attached to the hypothalamus which secretes hormones to maintain homeostasis

Epithalamus Makes the cerebrospinal fluid Helps to regulate the sleep/wake cycle by releasing hormones like melatonin Controls some parts of emotions and mood Epithalamus

Brain Stem Attaches to the spinal cord; primitive “rat brain” Controls automatic behaviors necessary for survival (breathing) Parts of the brain stem each about an inch long Midbrain Pons Medulla oblongata

Midbrain Smallest region of the brain that sort of works as a relay station for auditory and visual information. Also controls eye movements, like blinking

Pons The bulging center part of the brain stem Mostly composed of fiber tracts which relay messages to the brain Includes control of breathing

Medulla Oblongata The lowest part of the brain stem Merges into the spinal cord Includes important fiber tracts relaying messages Contains important control centers Heart rate control Blood pressure regulation Breathing Swallowing Vomiting

Cerebellum contains ~70% of all the brain's neurons; yet is only 10% of the volume of the brain! contributes to precise timing of skeletal muscle activity (i.e. walking, running or standing on your hands) controls our balance and equilibrium Doesn’t function well under influence of alcohol Works like ‘auto pilot’ – monitors body position and amount of tension in body parts

Cerebellum and other brain parts