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COGS17 ‐ 01‐The Nervous System 9/24/2009

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The Nervous SystemThe Nervous SystemMary ET Boyle, Ph.D.

Department of Cognitive ScienceUCSD

What’s the big deal?What’s the big deal?


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Detect Evaluate Decide Respond

Analysis of the nervous system to understand the biological basis for behavior.

Modern studiesModern studies◦ Neuroanatomists◦ Neurochemists◦ Neurophysiologists◦ Neuropsychologists

Neuroscience – term introduced in mid-1960s


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The brain must know what is happening outside in the environment.

•perceive•remember•decide•act

sensory neuronsmotor neuronsinterneurons

Peripheral Nervous System (PNS)System (PNS)

Central Nervous System (CNS)

OrganizationOrganization

Sys (C S)


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Somatic Nervous

Detects/processesenvironmental stimuli:

Somatic Nervous System

AutonomicNervous System

Regulates internal organs:

Organization of Organization of PNSPNS

Somatic Nervous System

AutonomicNervous System

Detects environmental stimuli:

Regulates internal organs:

Central nervous

Decision!

system


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Brain

Spinal Cord

Components of the CNSComponents of the CNS


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Anterior

PosteriorD lDorsal

Ventral

Left

Right

Anatomical directionsAnatomical directions

g


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Horizontal section—Shows structures viewed from above/below


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Sagittal section—Divides structures into right and left parts

Coronal section (frontal section)—Shows views from the front/back


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Review of Anatomical Directions

Anterior—toward the front (e.g., dog’s nose)Anterior toward the front (e.g., dog s nose)Posterior—toward the rear (e.g., dog’s tail)Ventral—toward the bellyDorsal—toward the backRostral—toward the headCaudal—toward the tailMedial—toward the midlineMedial toward the midlineLateral—away from the midlineSuperior—above a structureInferior—below a structure

Fundamental cellular unit Purpose of neurons:◦ receive ◦ processp◦ transfer

Information is made up of chemical or electrical signals

Unidirectional

NeuronsNeurons


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Neurobiology of Cognition COGS 17



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Four major types of synapses


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Three types of neurons

Some multipolar neurons


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Support Staff: Glia

More than just glue?

Glia, short for neuroglial cells.

Their purpose is to provide metabolic psupport, insulate, protect, reinforce, repair, and cleanup damaged areas.

Mounting evidence suggests that glial cells may be nearly as critical to thinking and learning as neurons

GliaGlia

thinking and learning as neurons are.


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are much more numerous than neurons. outnumber neurons 2:1. are found in both the CNS and PNS. Neuroglia means “nerve glue ” Neuroglia means nerve glue.

Researchers have found that the average human cerebral cortex has approximately two glial cells for every neuron (other brain regions have up to 10 times as many). That’s a glia index of 2.0. The index in comparable regions in rodents is 0.4, in worms 0.17. There is

Glia …Glia …

in comparable regions in rodents is 0.4, in worms 0.17. There is work that supports the theory that a high concentration of glia may actually boost the ability to think. So here’s something to think about: the glia index in the cerebral cortex of dolphins is 3.0.


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protoplasmic astrocytes

fibrous astrocytes

Basic classification of glial cells Basic classification of glial cells

microglial cells

oligodendrocytes

Spanish anatomist Pío del Río Hortega classified these cells. Hortegamade these drawings in 1920 with the help of a microscope’s camera lucida.


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Multiple sclerosis (MS) is a progressive central nervous system disorder.

Localized oligodendrocyte demyelination prevents affected nerve cells from functioning properly.

In some cases, the demyelinated axons completely fail to work.completely fail to work.


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Glia and neurons work togetherGlia and neurons work together


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Neurobiology of Cognition COGS 17Zlokovic & Apuzzo: Neurosurgery 43(4):877-878, 1998.


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(PNS)Peripheral

Nervous System

The Somatic Nervous System

The AutonomicNervous System Nervous SystemNervous System

The Somatic Nervous System

Enables one to interact with the

physical

SpinalCranial

Two types of nerves:

environment.

Afferentneurons bring

Efferent neurons take

fSpinalCranial g

messages from the sensory

receptors to the CNS

messages from the CNS to

skeletal muscles


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Table 2.1: Klein/Thorne: Biological Psychology© 2007 by Worth Publishers


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The AutonomicNervous System

Efferent neurons control glandular

activity and internal yorgan functioning.

Two divisions:

ParasympatheticSympathetic

S h iSympathetic

Prepares the organism to respond to challenging or

dangerous conditions.


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CNS protectionCNS protection


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Ventricular SystemVentricular System


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CNS: spinal cordCNS: spinal cord


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Three main functions:◦ Recognizing detected stimuli◦ Analyzing the information◦ Executing the appropriate response

The Central Nervous System: The Central Nervous System: The BrainThe Brain


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Myelencephalon—contains the medulla oblongata, which controls basic life functions (e.g., respiration, heart rate, vomiting, salivation

Reticular formation (reticular activating system)—begins in the medulla, extends to other areas of the brain and is involved in arousal

Metencephalon consists of two major structures:◦ Pons—a “bridge” for many fibers passing from one side

of the brain to the other. Sensory fibers, fibers from the cortex to cerebellum, and fibers that relay information on sleep, arousal and dreaming pass through it.

◦ Cerebellum—involved in the development and coordination of movement

Raphé system—plays a role in sleep and arousal

HindbrainHindbrain

Midbrain Midbrain -- mesencephalonmesencephalon


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Tectum (“roof”) relays visual and auditory information and controls simple reflexes, eye and ear orientation movements

superior colliculi (“little hills”)—relays visual informationinferior colliculi—relays auditory information

Tegmentum (“floor covering”) substantia nigra—integration of voluntary movementsred nucleus —controls basic body movementsreticular formation —controls arousal and consciousness

brain stem—midbrain + hindbrain(minus the cerebellum)


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Thalamus—major relay station for sensory informationMedial geniculate nucleus (MGN)—relays auditory informationLateral geniculate nucleus (LGN)—relays visual informationg yOther nuclei connect to areas not involved in sensation, e.g., the ventrolateral nucleus receives information from the cerebellum and relays it to the motor cortex.


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Hypothalamus—detects need states (e.g., hunger and thirst), controls the autonomic nervous system, and controls pituitary hormone production and releaseThe suprachiasmatic nucleus of the hypothalamus also is involved in the control of biological rhythms.

Pituitary gland (hypophysis)—regulates other glandular activity of the body (often called the “master gland”)

Anterior pituitary gland (adenohypophysis)—produces several hormones including somatotropin, thyrotropin, adrenocorticotropin and the gonadotropinsadrenocorticotropin, and the gonadotropins

Posterior pituitary (neurohypophysis)—releases oxytocin and antidiuretic hormone (ADH) which are produced in the hypothalamus


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Limbic SystemThe limbic system governs emotions such as anger, happiness, and fear and is involved in the storage and retrieval of memories.The limbic system is a group of structures surrounding the brain stem.The limbic system structures include the amygdala, cingulate gyrus, and hippocampus.

Basal Ganglia— have widespread connections to the cortex and forebrain and are involved in the initiation of voluntary movements, maintaining muscle tone and postureParts of the basal ganglia include:

The caudate nucleus, the putamen, and the globus pallidus

The caudate nucleus and the putamen are referred to as the corpus striatum due to their appearance.


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Somatosensory cortex —anterior portion of the parietal lobeSomatosensory cortex —anterior portion of the parietal lobe.

Motor cortex —area of the frontal lobe anterior to the central sulcus.The face and hands have a large amount of representation in these areas. This representation allows for great sensitivity and motor control for these areas of the body.


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Neurons—Perform information processing and communications functions of the nervous system◦ Consist of three major parts:

1. Soma (cell body)—contains nucleus, mitochondria, and ribosomes

2. Dendrites—portions of the neuron that transmit information toward the cell body (typically)

3. Axon—a structure on the neuron which transmits information away from the cell body

Terms reviewTerms review

sensory neuron◦ A neuron that detects changes in the external or internal environment

and sends information about these changes to the central nervous system.

◦ Sensory neurons carry information to the CNS

motor neuronA l t d ithi th t l t th t t l th ◦ A neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland.

◦ They carry information from CNS to muscles to control their functioning.

interneuron◦ A neuron located entirely within the central nervous system.◦ Interneurons connect sensory and motor neurons or communicate with

other interneurons.

central nervous system (CNS)


y ( )◦ The brain and the spinal cord.

peripheral nervous system (PNS)◦ The part of the nervous system outside the brain and spinal cord,

including the nerves attached to the brain and the spinal cord.


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Peripheral NS◦ Nerve—a collection of axons outside the CNS

Central NS◦ Tract—a collection of axons within the CNS

◦ Ganglion (plural, ganglia)—a collection of cell bodies outside the CNS

◦ Nucleus (plural, nuclei)—a collection of cell bodies within the CNS

Cells of the Nervous System: TerminologyCells of the Nervous System: Terminology

Presynaptic terminal—a swelling at the end of the axon or telodendron◦ Synaptic vesicles (contain neurotransmitter substance)◦ Synapse—point of functional contact between a neuron and its target◦ Synaptic cleft—small space which separates the presynaptic terminal from its target

Cells of the Nervous System: TerminologyCells of the Nervous System: Terminology


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Axodendritic—the axon synapses with dendrites of another neuron

Axosomatic—the axon synapses with the cell body of y p yanother neuron

Dendrodendritic synapse—occurs when the dendrites of one neuron synapses with the dendrites of another neuron

Axoaxonic synapse—the axon of one neuron synapses with the axon of another neuron

Neuromuscular junction—the axon synapses with a l

Cells of the Nervous System: Types of SynapsesCells of the Nervous System: Types of Synapses

muscle

Pituitary gland (hypophysis)—regulates other glandular activity of the body (often called the “master gland”)

Anterior pituitary gland (adenohypophysis) Anterior pituitary gland (adenohypophysis)—produces several hormones including somatotropin, thyrotropin, adrenocorticotropin, and the gonadotropins

Posterior pituitary (neurohypophysis)—releases oxytocin and antidiuretic hormone (ADH) which are produced in the hypothalamusproduced in the hypothalamus

CNSCNS——The Brain, Forebrain: The Brain, Forebrain: The DiencephalonThe Diencephalon


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CNS—The Brain, Forebrain: The Telencephalon

The telencephalon (end brain) consists of three parts:◦ Limbic system◦ Basal ganglia◦ Cerebral cortex

CNS—The Brain, Forebrain: The Telencephalon

Limbic System◦ The limbic system governs emotions such as anger, happiness, and fear and is involved in the storage and retrieval of memories.◦ The limbic system is a group of structures surrounding the brain stem.su ou d g t e b a ste◦ The limbic system structures include the amygdala, cingulate gyrus, and hippocampus.


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Basal Ganglia—have widespread connections to the cortex and forebrain and are involved in the initiation of voluntary movements, maintaining muscle tone and postureP f h b l li i l d Parts of the basal ganglia include:◦ The caudate nucleus, the putamen, and the globus

pallidus The caudate nucleus and the putamen are

referred to as the corpus striatum due to their appearance.

CNSCNS——The Brain, Forebrain: The Brain, Forebrain: The Telencephalon The Telencephalon

Cerebral Cortex—the convoluted outer layer of the forebrain that processes sensory information, controls thinking, decision making, stores and retrieves memory, and initiates motor responses

The cortex is divided into two hemispheres (connected by the corpus callosum) and each hemisphere has four lobes.

CNSCNS——The Brain, Forebrain: The Brain, Forebrain: The Telencephalon The Telencephalon


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soma◦ The cell body of a neuron, which contains the nucleus.

dendrite◦ The branched, treelike structure attached to the soma of a

neuron; receives information from the terminal buttons of neuron; receives information from the terminal buttons of other neurons.

synapse◦ A junction between the terminal button of an axon and the

membrane of another neuron.


axon◦ The long, thin, cylindrical structure that conveys information

from the soma of a neuron to its terminal buttons.

multipolar neuron◦ A neuron with one axon and many dendrites attached to

its soma.

bipolar neuron◦ A neuron with one axon and one dendrite attached to its ◦ A neuron with one axon and one dendrite attached to its

soma.

pseudounipolar neuron◦ A neuron with one process attached to its soma; the

process divides, with one branch receiving sensory information and the other sending the information into the central nervous system.


terminal button◦ The bud at the end of a branch of an axon; forms

synapses with another neuron; sends information to that neuron.


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neurotransmitter◦ A chemical that is released by a terminal button; has

excitatory or inhibitory effect on another neuron.

membrane◦ A structure consisting principally of lipid molecules that

defines the outer boundaries of a cell and also constitutes many of the cell organelles, such as he Golgi apparatus.

nucleus◦ A structure in the central region of a cell, containing the

nucleolus and chromosomes.

nucleolus


nucleolus◦ A structure within the nucleus of a cell that produces the

ribosomes.

ribosome◦ A cytoplasmic structure, made of protein, that serves as the

site of production of proteins translated from mRNA.

chromosome◦ A strand of DNA with associated proteins found in the A strand of DNA, with associated proteins, found in the

nucleus; carries genetic information.

deoxyribonucleic acid (DNA)◦ A long, complex macromolecule consisting of two

interconnected helical strands; along with associated proteins, strands of DNA constitute the chromosomes.


gene◦ The functional unit of the chromosome, which directs

synthesis of one or more proteins.


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messenger ribonucleic acid (mRNA)◦ A macromolecule that delivers genetic information

concerning the synthesis of protein from a portion of a chromosome to a ribosome.

enzymeA molecule that controls a chemical reaction combining two ◦ A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts.

non-coding RNA (ncRNA)◦ A form of RNA that does not encode for protein, but has

functions of its own.

cytoplasm


y p◦ The viscous, semiliquid substance contained in the interior of

a cell.

mitochondrion◦ An organelle that is responsible for extracting energy from

nutrients.

adenosine triphosphate (ATP)◦ A molecule of prime importance to cellular energy metabolism; its

breakdown liberates energy.

endoplasmic reticulum◦ Parallel layers of membrane found within the cytoplasm of a cell.

Rough endoplasmic reticulum contains ribosomes and is involved with production of proteins that are secreted by the cell. Smooth endoplasmic reticulum is the site of synthesis of lipids and provides channels for the segregation of molecules involved in various cellular processes.


Golgi apparatus◦ A complex of parallel membranes in the cytoplasm that wraps the

products of a secretory cell.


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exocytosis◦ The secretion of a substance by a cell through means of

vesicles; the process by which neurotransmitters are secreted.

lysosomeAn organelle surrounded by membrane; contains enzymes ◦ An organelle surrounded by membrane; contains enzymes that break down waste products.

cytoskeleton◦ Formed of microtubules and other protein fibers, linked to

each other and forming a cohesive mass that gives a cell its shape.


microtubule◦ A long strand of bundles of protein filaments arranged

around a hollow core; part of the cytoskeleton and involved in transporting substances from place to place within that cell.

Glial cells◦ One-tenth the size of neurons◦ Ten times as numerous as neurons

Types of Glial cellsyp◦ Astrocytes—provide physical support to neurons, nourishment and other functions. New evidence suggests that astrocytes also integrate neuronal messages and release neurotransmitters that affect the sensitivity of synapses.

Cells of the Nervous System: Glial cellsCells of the Nervous System: Glial cells


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Types of Glial cells (cont.)◦ Microglial cells—remove debris◦ Oligodendrocytes—produce myelin which Oligodendrocytes produce myelin which covers the axons of neurons in CNS◦ Schwann cells—produce myelin which covers the axons of neurons in PNS

Multiple sclerosis—destroys oligodendrocytes

axoplasmic transport◦ An active process by which substances are propelled along

microtubules that run the length of the axon.

anterogradeIn a direction along an axon from the cell body toward the ◦ In a direction along an axon from the cell body toward the terminal buttons.

retrograde◦ In a direction along an axon from the terminal buttons

toward the cell body.

li


glia◦ The supporting cells of the central nervous system.


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astrocyte◦ A glial cell that provides support for neurons of the central

nervous system, provides nutrients and other substances, and regulates the chemical composition of the extracellular fluid.

h phagocytosis◦ The process by which cells engulf and digest other cells or

debris caused by cellular degeneration.

oligodendrocyte◦ A type of glial cell in the central nervous system that forms

myelin sheaths.


myelin sheath◦ A sheath that surrounds axons and insulated them,

preventing messages from spreading between adjacent axons.

node of Ranvier◦ A naked portion of a myelinated axon, between adjacent

oligodendroglia or Schwann cells.

microgliac og a◦ The smallest of glial cells; act as phagocytes and protect the

brain from invading microorganisms.

Schwann cell◦ A cell in the peripheral nervous system that is wrapped

around myelinated axon, providing one segment of its myelin sheath.


sheath.


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Skull—outer bony covering that encases the brain

Vertebral Column—outer bony covering that encases the spinal cord

Meninges◦ Dura matter◦ Arachnoid matter◦ Pia mater

Ventricular system

The Protective Features of the CNSThe Protective Features of the CNS

y

blood-brain barrier◦ A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain’s capillaries.

area postrema◦ A region of the medulla where the blood-brain barrier is weak; poisons can be detected there and can initiate vomiting.


g

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