THE FUNCTIONS OF THE NERVOUS SYSTEM The Central Nervous System

THE CENTRAL NERVOUS SYSTEM The nervous system is divided into two subunits Central nervous system (CNS) Brain spinal cord. Peripheral nervous system Any part of nervous system outside of CNS Afferent and efferent.

THE Cells of the CENTRAL NERVOUS SYSTEM All of these systems contain neurons: Obviously single neural cells. And accompanying structure cells such as glia. We label collections of neurons in two ways: Nucleus or Nuclei: A group of cell bodies (somas) in the CNS Ganglion or Ganglia: Group of cell bodies in the peripheral nervous system.

THE Cells of the CENTRAL NERVOUS SYSTEM Contains neurons: obviously single neural cells. Nerve : is a bundle of axons running together like a multi-wire cable. Nerve is used only in the peripheral nervous system. Tracts. Bundles of neurons Inside the CNS Tracts = nerves

MAJOR Divisions of the CNS Forebrain Cerebral hemispheres Frontal lobe Parietal lobe Occipital lobe Temporal lobe Thalamus and hypothalamus Corpus callosum Ventricles Midbrain and Hindbrain Superior colliculi Thalamus Pineal gland Hindbrain Pons; Medulla; Reticular activating system Spinal Cord

Let’s start at the top! The Forebrain! Figure 3.2 View of a human brain Let’s start at the top! The Forebrain!

THE Forebrain Forebrain is composed of: Two cerebral hemispheres, The thalamus, The hypothalamus. The large, wrinkled cerebral hemispheres dominate the brain’s appearance.

Gyri and sulci The brain’s surface has many ridges and grooves that give it a very wrinkled appearance. Several geographic landmarks: Gyrus. Each ridge or high point Sulcus: The groove or space between two Fissure: large sulcus

Gyrus Sulcus Figure 3.4 Human brain viewed from above Showing cerebral hemispheres and longitudinal fissure.

THE Forebrain The longitudinal fissure Remember: that runs the length of the brain separates the two cerebral hemispheres, Two cerebral hemispheres are mirror images of each other in appearance. Remember: Left hemisphere brain controls right side of body Right brain hemisphere controls left side of body

convolutions of the cortex The outer surface is the cortex, which is made up mostly of the cell bodies of neurons. Because cell bodies are not myelinated, the cortex looks grayish in color, Thus referred to as gray matter. The cortex is only 1.5 – 4 mm thick,

convolutions of the cortex Convolutions (folds) increase the amount of cortex by tripling the surface area. Also provides axons easier access to cell bodies Axons come together at central core of each gyrus Here the brain appears white

Organization of the CENTRAL NERVOUS SYSTEM The central nervous system is arranged in a hierarchy. As you ascend from the spinal cord through the hindbrain and midbrain to the forebrain, the neural structures become more complex and so do the behaviors they control. The hemispheres are divided into four lobes – Frontal Parietal, Occipital Temporal each named after the bone of the skull above it.

Is size important? Relation of brain size to body size versus intelligence Brain size more related to body size Brains of elephants and sperm whales 5-6x larger than human brain What is important? Convolutions are the important variable! Greater number of gyri = more cortex Also; more gyri in cerebral hemispheres than lower brain parts More surface area = more connections

THE frontal lobe Frontal lobe anterior to (in front of) the central sulcus superior to (above) the lateral fissure. Precentral gyrus: extends the length of the central sulcus Contains primary motor cortex,: Controls voluntary (nonreflexive) movement. The parts of the body are “mapped onto” the motor area of each hemisphere Can be illustrated in the form of a homunculus, which means “little man.” The secondary motor areas are located just anterior to the primary area.

PreFrontal Cortex

THE motor homunculus More brain area is devoted to parts of body with greater/finer motor movement Fingers Hands Lips Legs Arms Little brain area devoted to motor movement of back, toes, etc.

broca’s area Broca’s area is located anterior to the motor area and along the lateral fissure. Broca’s area controls speech production Contributes the movements involved in speech and grammatical structure.

THE prefrontal cortex Prefrontal Cortex – The most anterior part of the frontal lobes Largest region in the human brain, Twice as large as in chimpanzees, Accounts for 29% of the total cortex. The prefrontal cortex is involved in Planning and organization, Impulse control, Adjusting behavior in response to rewards and punishments, Some forms of decision making.

THE prefrontal cortex

THE prefrontal cortex How know the effects of the Prefrontal cortex? During the 1940s/1950s surgeons performed tens of thousands of lobotomies, Surgical procedure disconnected prefrontal area from the rest of brain. Initially, surgeries performed on very disordered schizophrenics Overly enthusiastic doctors lobotomized patients with much milder problems.

THE prefrontal cortex Effects? The surgery calmed agitated patients, Benefits came at a high price in that patients often became: Emotionally blunted Distractible Childlike in behavior. Psychosurgery rarely used today to treat psychiatric problems

Right: A brain showing the gaps (arrows) produced by a lobotomy Walter Freeman inserts his instrument between the eyelid and the eyeball, drives it through the skull with a mallet, and moves it back and forth to sever the connections between the prefrontal area and the rest of the brain. . Figure 3.10 Lobotomy procedure and a lobotomized brain Left: Walter Freeman inserts his instrument between the eyelid and the eyeball, drives it through the skull with a mallet, and moves it back and forth to sever the connections between the prefrontal area and the rest of the brain. Right: A brain showing the gaps (arrows) produced by a lobotomy. Right: A brain showing the gaps (arrows) produced by a lobotomy

THE parietal lobes Parietal lobes Primary somatosensory cortex Located superior to the lateral fissure Between the central sulcus and the occipital lobe. Primary somatosensory cortex Located on the postcentral gyrus, Processes the skin senses (touch, warmth, cold, and pain), Also senses that inform us about body position and movement.

THE somatosensory homunculus The somatosensory cortex also is organized as a homunculus, size of each area depends on the sensitivity in that part of the body.

THE parietal association areas Contained in each of the lobes carry out further processing beyond what the primary area does often combine information from other senses. Parietal lobe association areas: receive input from the body senses and from vision. Help a person identify objects by touch help determine the location of the limbs Help locate objects in space.

THE parietal association areas Damage to the posterior parietal cortex may produce sensory neglect: a disorder in which the person ignores Objects, People, Activity on the side opposite the damage. Why the opposite side of the damage?

THE temporal lobe Temporal lobes Separated from the frontal and parietal lobe by the lateral fissure Three important areas: Auditory projection area, Visual-auditory association area Wernicke’s Area: Additional language area

THE auditory or temporal cortex Auditory cortex: Receives sound information from the ears Lies on the superior (uppermost) gyrus of the temporal lobe. Wernicke’s area Just posterior to the auditory cortex Interprets language input arriving from the nearby auditory and visual areas. also generates spoken language through Broca’s area and written language by the way of the motor cortex. Inferior temporal cortex Lower part of the lobe (as the name implies) Plays a major role in the visual identification of objects.

THE occipital cortex Occipital lobes Location of the visual cortex, Visual information is processed. Contains a map of visual space because adjacent receptors in the back of the eye (retina) send neurons to adjacent cells in the visual cortex.

So, What do we know so far? Brain has a cortex, or outer area 4 lobes: Is the largest part of our brain Responsible for most of our sensory and cognitive behavior 4 lobes: Frontal: planning, thinking, motor Temporal: Hearing, coordinating senses, language Parietal: movement and sensory awareness Occipital: Vision Each of these lobes has many parts, and these parts are specialized (memorize these!)