chapter3cv_53226

BIOPSYCHOLOGY 8e John P.J. Pinel

Copyright © Pearson Education 2011

A communication

network consisting of

nerve cells, both inside and

outside of the brain and spinal

cord

e r v o u s! s y s t e m!


General Layout of the Nervous System

The major divisions of the nervous system. “A system of twos.”



Central Nervous System (CNS)

•  Brain (in the skull) •  Spinal Cord (in the spine)

Peripheral Nervous System (PNS)

•  Located outside of the skull and spine

•  Serves to bring information into the CNS and carry signals out of the CNS



Peripheral Nervous System •  Somatic Nervous System

  Afferent nerves (sensory)   Efferent nerves (motor)

•  Autonomic Nervous System   Regulates internal

environment   Afferent nerves (sensory

signals from internal organs)

  Two types of efferent nerves (motor nerves from to internal organs)   Sympathetic and

parasympathetic efferents  


Autonomic Nervous System

Two types of efferent nerves:

Sympathetic and parasympathetic nerves generally have opposite effects

Each autonomic target gets opposing sym and parasym input

Two-stage neural paths, neuron exiting the CNS synapses on a second-stage neuron before the target organ


SYMPATHETIC EFFERENTS PARASYMPATHETIC EFFERENTS

Cranial and sacral

“Rest and digest”

Second stage neurons are near the target organ


Thoracic and lumbar

“Fight or flight”

Second stage neurons are far from the target organ


Meninges, Ventricles, and Cerebrospinal Fluid (CSF)

CNS encased in bone and covered by three meninges

•  Dura mater – tough outer membrane

•  Arachnoid membrane – web-like

•  Pia mater – adheres to CNS surface

Cerebrospinal fluid (CSF) •  Fluid serves as cushion –  Fills ventricles, subarachnoid

space and central canal


Protecting the Brain


The Cerebral Ventricles


Protecting the Brain

Chemical protection

•  The blood-brain barrier – tightly-packed cells of blood vessel walls prevent entry of many molecules

Physical protection

• Skull • Meninges • Cerebrospinal fluid

(CSF)


The human brain Neurons

Neurons and the Human Brain

An amazingly intricate network of neurons

Cells that receive and transmit electrochemical signals


Neurons

Specialized cells for the reception, conduction, and transmission of electrochemical signals

Many sizes and shapes

Cells of the Nervous System: Anatomy of Neurons


The major external features of a typical neuron


The major internal features of a typical neuron


The cell membrane is a lipid bilayer with signal proteins and channel proteins embedded in it



A unipolar neuron, a bipolar neuron, a multipolar neuron, and an interneuron



Glial cells • Support neurons • Outnumber neurons

10:1 (apparently) •  Recent evidence for

glial communication and modulatory effects of glia on neuronal communication

• Much ongoing research in this area

Glial Cells: The Forgotten Cells


1

2

3

4

Oligodendrocytes – extensions rich in myelin create myelin sheaths in CNS

Schwann cells – similar to function of oligodendrocytes but in PNS, can guide axonal regeneration (clinical applications) Astrocytes – largest glia, star-shaped, many functions such as support and protection (and signalling)

Microglia – involved in response to injury or disease

Four Classes of Glial Cells


The myelination of CNS axons by an oligodendrocyte and the myelination of PNS axons by Schwann cells



Terminology

CNS PNS

Myelin-providing glia

Oligodendrocytes Schwann cells

Clusters of cell bodies (activity)

Nuclei (singular nucleus)

Ganglia (singular ganglion)

Bundles of axons (pathways)

Tracts Nerves



Figure 3.14

Directions in the Vertebrate Nervous System

Anatomical directions in a representative vertebrate (cat).


Figure 3.15


Anatomical directions in a human


Anatomical directions ignore the fact that humans walk upright. Therefore, top of the head is both “dorsal” (back) and “superior” (top)

Other directions: •  Medial – toward the middle •  Lateral – toward the side •  Proximal – close •  Distal – far



Sections of the Brain

• Horizontal – a slice parallel to the ground

• Frontal (coronal) – slicing bread or salami

• Sagittal – a midsagittal section separates the left and right halves


Spinal Cord

Dorsal – afferent, sensory

Gray matter – inner component, primarily cell bodies

White matter – outer area, mainly myelinated axons

Ventral – efferent, motor


Five Major Divisions of the Brain


Major Structures of the Brain

Myelencephalon = medulla •  Composed largely of tracts •  Origin of the reticular

formation •  Arousal, sleep, attention,

muscle tone, vital reflexes

Metencephalon •  Many tracts •  Pons – ventral surface

•  Functions similar to medulla

•  Cerebellum – coordination


Structures of the human myelencephalon (medulla) and metencephalon



Mesencephalon = midbrain •  tectum has inferior (auditory) and superior

colliculi (visual) •  on dorsal surface

•  tegmentum has •  periaqueductal gray (pain), •  substantia nigra, and red nucleus

(sensorimotor •  medial and ventral

Diencephalon •  Thalamus (sensory relay to cortex •  Hypothalamus (controls ANS, endocrine

systems


The human mesencephalon (midbrain)



The human diencephalon



Telencephalon – Cerebral Cortex

Convolutions serve to increase surface area Outer covering unmyelinated grey matter Layer beneath myelinated axons – white matter

Longitudinal fissure – a groove that separates right and left hemispheres

Corpus callosum – largest hemisphere-connecting tract


e r e b r a l c o r t e x!

Outermost part of forebrain, responsible for analyzing sensory processing and higher brain functions


The major fissures of the human cerebral cortex

The lobes of the cerebral hemisphere


Telencephalon – Subcortical Structures

Limbic system – regulation of motivated behaviors •  Mammillary bodies,

hippocampus, amygdala, fornix, cingulate, septum

Basal ganglia motor system •  Amygdala, striatum (caudate

nucleus + putamen), globus pallidus


The major structures of the limbic system: amygdala, hippocampus, cingulate cortex, fornix, septum, and mammillary body

Regulation of motivated behaviours, emotion and memory

The Limbic System


Structures in the forebrain that help to control movement •  Damage to the basal ganglia contributes to Parkinson’s disease.

•  The basal ganglia also allow us to perform voluntary movements to obtain rewards.

• Many implications: • http://www.youtube.com/watch?v=crh_LGBNwSA

The Basal Ganglia


The basal ganglia: amygdala, striatum (caudate plus putamen) and globus pallidus

The Basal Ganglia


Summary of major brain structures

chapter3cv_53226

Documents

system of twos

human brain neurons

stage neurons

neurons specialized

parasympathetic nerves

autonomic target

cerebrospinal fluid

unipolar neuron