Anatomy of the Nervous SystemStructure and Function

January 17, 2002

Gross Anatomy

Five major divisions of the brain encephalon = “inside the head” Forebrain

• Telencephalon• Diencephalon

Midbrain• Mesencephalon

Hindbrain• Metencephalon• Myelencephalon (“medulla”)

Brains stem

Diencephalon Mesencephalon Metencephalon Myelencephalon

Diencephalon

Thalamus• top of the brain stem• receives sensory signals and sends them on to

sensory cortex

Hypothalamus• located just below anterior thalamus• regulation of motivated behaviors

Mesencephalon

Tectum (“roof”)• dorsal surface of the brain stem• auditory and visual functions

Tegmentum• in front of tectum• processing pain and sensorimotor functions

Metencephalon

Pons (buldge) of the brainstem Attachment of some cranial nerves

Myelencephalon

Also called medulla Most posterior portion of the brain Large tracts running from brain to body Reticular formation (“little net”)

• sleep, attention, movement, muscle tone• reflexes - cardiac, circulatory, respiratory

Telencephalon

Greatest growth in higher vertebrates Hemispheres - right and left Four lobes in cerebrum

• frontal• temporal• parietal• occipital

Function of Telencephalon

Mediates complex functions• initiates voluntary movement• interprets sensory input• cognitive processes

• learning

• speech & language

• problem solving

Cerebral Cortex

Layer of tissue covering cerebrum Convolutions

• fissures = furrows• central and lateral fissures divide lobes

• gyri = ridges Longitudinal fissure-separates hemispheres Cerebral commissures-connect hemispheres

• largest = corpus callosum

Major Gyri

Precentral gyrus - primary motor area Postcentral gyrus - body sensations Superior temporal gyrus - auditory cortex Cingulate gyrus – emotional, somatic and

autonomic fxs

Hippocampus (“sea horse”)

Shared by cerebral cortex and limbic system

Located in the medial temporal lobe Role in learning and memory

Function of the Limbic System

Circuit of structures around the thalamus Regulate motivated behaviors

• “the four Fs”• fleeing

• feeding

• fighting

• sexual behavior

Structures of the Limbic System

Amygdala (“almond”) Hippocampus (“sea horse”) Fornix (“arc”) Cingulate cortex (“encircling”) Septum Mammillary bodies

Function of the Basal Ganglia

Voluntary motor response Example of dysfunction = Parkinson’s

• rigidity• tremors• poor movement initiation

Structures of the Basal Ganglia

Amygdala Striatum (“striped structure”)

• Caudate (“tail-like”)• Putamen

Globus pallidus (“pale globe”)

Brain Areas Relevant to Language Lichtheim-Geschwind Model

• Broca’s area• Wernicke’s area• Arcuate fasciculus• Angular gyrus

Broca’s area

Posterior portion of lower left frontal lobe Speech and language production

Wernicke’s area

Posterior portion of left temporal area Auditory comprehension

Arcuate fasciculus

Pathway that relays nerve impulses between Broca’s and Wernicke’s areas

Connections between sound patterns and production area

Angular gyrus

Parietal lobe Sensory properties of objects are associated

with words