THE FUNCTIONS OF THE FUNCTIONS OF THE NERVOUS THE NERVOUS

SYSTEMSYSTEM

The Central Nervous SystemThe Central Nervous System

THE CENTRAL THE CENTRAL NERVOUS SYSTEMNERVOUS 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 THE Cells of the CENTRAL NERVOUS SYSTEMNERVOUS SYSTEM

• Contains neurons: obviously single neural cells.

• Nucleus– A group of cell bodies (somas) in the CNS and a

• Ganglion– Group of cell bodies in the peripheral nervous system.

THE Cells of the CENTRAL THE Cells of the CENTRAL NERVOUS SYSTEMNERVOUS 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

Divisions of the CNSDivisions 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!

THE ForebrainTHE Forebrain

• Forebrain – two cerebral hemispheres, – the thalamus, – the hypothalamus.

• The large, wrinkled cerebral hemispheres dominate the brain’s appearance.

• The longitudinal fissure – 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

Gyri and sulciGyri and sulci

• The brain’s surface has many ridges and grooves that give it a very wrinkled appearance.

• Several geographic landmarks:– gyrus. Each ridge – a sulcus The groove or space between two– Fissure: large sulcus

Gyrus

Sulcus

convolutions of convolutions of the cortexthe 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 (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 Organization of the CENTRAL NERVOUS SYSTEMNERVOUS 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?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 lobeTHE 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, which 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.

THE motor homunculusTHE 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 areabroca’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 cortexTHE 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 cortexTHE prefrontal cortex

PrefrontalCortex

THE prefrontal cortexTHE prefrontal cortex

• How know the effects of the Prefrontal cortex?– During the 1940s and 1950s surgeons performed tens of

thousands of lobotomies, a surgical procedure that disconnected the prefrontal area from the rest of the brain.

– Initially the surgeries were performed on very disordered schizophrenics, but many overly enthusiastic doctors lobotomized patients with much milder problems.

• 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

THE parietal lobesTHE parietal lobes

• Parietal lobes – 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 homunculusTHE 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 THE parietal association areasassociation areas

• 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.

• 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 lobeTHE temporal lobe

• Temporal lobes • Separated from the

frontal and parietal lobe by the lateral fissure

• Three important areas:– Auditory projection area, – visual and auditory association

areas– Additional language area:

Wernicke’s Area.

THE auditory or THE auditory or temporal cortextemporal 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 cortexTHE 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 send neurons to adjacent cells in the visual cortex.