THE FUNCTIONS OF THE NERVOUS SYSTEM The Central Nervous System.
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Transcript of THE FUNCTIONS OF THE NERVOUS SYSTEM The Central Nervous System.
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.