structure

Structure and Function

Introduction

The central nervous system can be broken down structurally as follows:

Spinal Cord
Hindbrain

Medulla (myelencephalon)
Pons (metencephalon)
Cerebellum

Midbrain (mesencephalon)
Forebrain

Telencephalon

Cerebral Cortex

Frontal Lobe
Temporal Lobe
Parietal Lobe
Occipital Lobe

Subcortical Structures

Basal Ganglia
Hippocampus and Amygdala (parts of the Limbic System)

Corpus Collosum

Diencephalon

Thalamus
Hypothalamus

The brainstem refers to the midbrain and portions of the hindbrain. Specifically, the brainstem comprises:

Midbrain (mesencephalon)
Medulla (myelencephalon)
Pons (metencephalon)

Spinal Cord

The spinal cord is one of the two major components of the central nervous system:

Like the brain, it is completely encased in bone. It resides within the vertebral column
Connects directly to the medulla section of the brain
It is approximately 45 cm long in an adult
Receives sensory messages and sends them to the brain
Sends motor messages from the brain
Also acts independently from the brain: e.g., reflexes

Hindbrain

Oldest part of the brain
Located between the spinal cord and the brain hemispheres
Consists of the medulla, pons and cerebellum
Contains many nuclei, including those that produce the neurotransmitters for the whole brain
Controls many involuntary, life-sustaining processes including

Respiration
Circulation
Digestion

Medulla (myelencephalon)

Full name: Medulla Oblongata ("oblong marrow")

Connects the spinal cord to pons

Pons (metencephalon)

Full name: Pons Varolii. Originally means 'bridge'

Bridges the cerebrum and the cerebellum through cerebellar peduncles

Cerebellum

Located directly behind the brainstem
Use for coordination and balance
Handles walking and posture

Midbrain

Controls posture and walking

Handles reflexes of eye movements

Forebrain

The forebrain is divided into two main sections:

Telencephalon

Cerebral Cortex
Basal Ganglia
Limbic System (hippocampus and amygadala)

Diencephalon

Thalamus
Hypothalamus

The cerebral cortex is composed of two hemispheres comprising four lobes: the frontal, temporal, parietal, and occipital lobes. The following diagrams show both lateral and midsagittal views of the cerebral cortex.

Frontal Lobe

Most developed in humans

Largest of the four lobes

Olfactory cortex

Motor cortex

Language production

Memory and higher cognitive function

Temporal Lobe

Auditory processing

Memory

Understanding language

Basal Ganglia

Limbic System

In the above lateral and anterior views, the red golf ball shaped structure is the amygdala. The green supporting structure is the caudate nucleus.

Emotion processing

Hippocampus

In the above lateral and anterior views, the purple structure is the hippocampus. The amygdala is shown again as a red golf ball shaped structure.

Responsible for the formation of long-term memories

Damage to this area does not destroy old memories; rather, new memories can no longer be formed

Corpus Collosum

The major link between the left and right hemispheres

Bundle of axons which allow communication of neurons across both hemispheres

Diencephalon

Thalamus

Primary "gate" between sensory or motor neurons in the PNS and the cerebral hemispheres in the CNS

Hypothalamus

Interacts primarily with the Autonomic Nervous System (ANS)

Maintains homeostasis: like a thermostat, it increases or decreases metabolism in order to regulate body activity

Summary of Structures

Cerebral cortex lobes:

Cerebral Hemisphere	Primary Function (Motor/Sensory)	Secondary Function (Cognitive)
Frontal	Motor	Motor planning and execution, attention, executive functions, perhaps consciousness?
Temporal	Auditory and Olfactory	Memory, language, emotion
Parietal	Somatosensory	Spatial attention
Occipital	Visual	Map of visual world

Other structures:

Section	Function
Spinal Cord	Input-output of sensory and motor information to and from the CNS-PNS
Medulla	Autonomic function (breathing, heart rate, etc.)
Pons	Auditory and vestibular (balance), sensory and motor
Cerebellum	Motor coordination and motor learning
Midbrain	Visuomotor functions, visual reflexes, auditory relays, motor coordination
Thalamus	Part of the diencephalon within the forebrain. Projects information to specific areas of the cerebrum, and controls which information is sent to the cerebral cortex
Hypothalamus	Regulates homeostasis in conjunction with the autonomic nervous system
Basal Ganglia	Centers for motor coordination
Hippocampus	Memory formation
Amygdala	Emotion processing
Corpus Collosum	Bundle of axons which connects the two hemispheres

Quick Quiz

What structures are depicted below?


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