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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.