Chapter 13

nervous system

coordinates and controls body activity

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three basic types of the system response are sensory, integrative, and motor

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detects and processes internal and external information and formulates appropriate responses

sensory role

detects and processes internal and external stimuli

integrative role

process sensory information

motor role

formulate appropriate responses by either causing muscle contraction or glandular secretion

central nervous system

portion of the nervous system that consists of the brain and spinal cord

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contains white and grey matter

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abbreviated CNS

peripheral nervous system

portion of the nervous system that consists of the cranial and spinal nerves, automatic nervous system, and ganglia

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abbreviated PNS

neuron

basic unit of the nervous system

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three types based on their function

sensory neurons

nerves that carry sensory impulses toward the CNS

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also called afferent or ascending tracts

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carry information toward the CNS, such as sound and light is converted into electrical impulses so that the nerves can transport it

associative neurons

nerves that carry impulses from one neuron to another

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also called connecting neurons

motor neurons

nerves that carry impulses away from the CNS and toward the muscles and glands

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also called efferent or descending tracts

cell body

soma

has a nucleus and is responsible for maintaining the life of the neuron

dendrites

rootlike structures that receive impulses and conduct them toward the cell body

dendr/o

combining form for dendrite

axon

single process that extends away from the cell body and conducts impulses away from the cell body

ax/o

combining form for axis or main stem

synapse

gap or space

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junction between two neurons or between a neuron and a receptor

terminal end fibers

branching fibers that lead the impulse away from the axon and toward the synapse

nerve fibers

another name for axons and dendrites

nerves

nerve trunks

bundles of nerve fibers bound together by specialized tissues

neurolemma

neurilemma

tubelike membrane cover of on nerve fiber

nuclei

neuron cell bodies grouped together within the CNS

ganglia

neuron cell bodies grouped together outside the CNS

synaps/o, synapt/o

combining form for space or point of contact

neurotransmitter

synapse is the junction where neural impulses cause a release of a chemical substance called this

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allows signals to move from one neuron to another

neuroglia

glial cells

supportive cells of the nervous system

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consist of astrocytes, microglia, oligodendrocytes, and Schwann cells

gli/o

combining form meaning glue

astr/o

combining form meaning star

astrocytes

star shaped

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cover the capillary surface of the brain, and help form the blood brain barrier in the CNS

blood brain barrier

separates the nervous tissue from blood and consists of capillary walls in the CNS without fenestrations (perforations) and the surrounding astrocytes

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prevents or slows the passage of drugs, chemicals, and some microbes from entering the CNS

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abbreviated BBB

myelin

myelin sheath

protective covering over some nerve cells

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including parts of the spinal cord, white matter of the brain, and most peripheral nerves

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serves as an electrical insulator

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gives nerve fibers a white color

white matter

myelinated nerves and fiber

grey matter

does not contain myelinated fibers

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darker in color

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composed of cell bodies, branching dendrites, and neuroglia

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consists of nerve cell bodies

nonmyelinated

some nerve fibers have a very thin layer of myelin and referred to as this

nerve

one or more bundles of impulse carrying fiber that connect the CNS to the other parts of the body

neur/i, neur/o

combining form for nerve or nerve tissue

tract

group of nerve fibers located in the CNS

ascending tracts

groups of nerves going up or cranial carrying nerve impulses toward the brain

descending tracts

groups of nerves going down or caudally carrying nerve impulses away from the brain

ganglion

knotlike mass of neuron cell bodies located outside the CNS

ganglia

more than one ganglion

gangli/o, ganglion/o

combining form meaning knotlike masses of nerve cell bodies located outside the CNS

innervation

supply or stimulation of a body part through the action of nerves

receptors

sensory organs that receive external stimulation and transmit that information to the sensory neurons

nociceptive receptors

pain receptors

proprioceptive receptors

spatial orientation or perception of movement receptors

stimulus

something that excites or activates

stimuli

multiple excitations or activations

impulse

wave of excitation transmitted through nervous tissue

reflex

automatic, involuntary response to change

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actions include patellar and ulnar reflexes

hyporeflexive

decreased reflexes

hyperreflexive

exaggerated reflexes

encephal/o

combining form for brain

myel/o

combining form for spinal cord and bone marrow

meninx

connective tissue that encases the brain and spinal cord

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has three layers

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more commonly known as meninges

mening/o, meningi/o

combining form for the layers of the connective tissue enclosing the CNS

dura matter

pachymeninx

thick, tough, outermost layer of the meninges

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this layer is tough and strong

dura

tough

dur/o

combining form for dura mater

pachy-

prefix meaning thick

arachnoid membrane

second layer of the meninges

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resembles a spider web

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loosely attached to the other layers of the meninges to allow space between the layers

arachn/o

combining form for spider

pia mater

third and deepest layer of the meninges

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this layer is soft with a rich supply of blood vessels

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adheres to the CNS

pia

soft or tender

leptomeninges

pia mater and arachnoid membranes collectively

lept/o

combining form for thin

epidural

located above or superficial to the dura mater

epi-

prefix meaning above or upon

subdural space

area located deep to (below) the dura mater and superficial to (above) the arachnoid membrane

sub-

prefix meaning below

subarachnoid space

area located deep to (below) the arachnoid membrane and superficial to (above) the pia mater

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contains cerebrospinal fluid

cerebrospinal fluid

clear, colorless ultrafiltrate that nourishes, cools, and cushions the CNS

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abbreviated CSF

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produced by special capillaries in the ventricles of the brain

ventricles

cavities of the brain

choroid plexus

vascular folds of the pia mater in the ventricles that secrete CSF

brain

the enlarged and highly developed portion of the CNS that lies in the skull and is the main site of nervous control

cranium

portion of the skull that encloses and protects the brain

crani/o

combining form for skull

cerebrum

largest part of the brain

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responsible for receiving and processing stimuli, initiating voluntary movement, and storing information

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divided into left and right hemispheres - hemispheres divided into lobes

cerebr/o

combining form for cerebrum

cerebral cortex

made up of grey matter and is arranged in folds

gyri

elevated portions of the cerebral cortex

convolut/o

combining form meaning coiled

gyr/o

combining form meaning folding

fissures

sulci

grooves of the cerebral cortex

cerebellum

second largest part of the brain

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coordinates muscle activity for smooth movement

cerebell/o

combining form for cerebellum

brainstem

supports basic life function

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stalklike portion of the brain that connects the cerebral hemispheres with the spinal cord

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consists of the pons, medulla oblongata, midbrain, and interbrain

interbrain

contains structures such as the pituitary gland, hypothalamus, and thalamus

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these structure responsible for endocrine activity, regulation of thirst and water balance, and regulation of body temperature

midbrain

contains structures responsible for visual and auditory reflexes, posture, and muscle control

pons

the bridge at the base of the brain that allows nerves to cross over so that one side of the brain controls the opposite side of the body

medulla oblongata

cranial continuation of the spinal cord that controls basic life functions

frontal lobe

most cranial lobe that controls motor function

parietal lobe

receives and interprets sensory nerve impulses

occipital lobe

most caudal lobe that controls vision

temporal lobe

laterally located lobe that controls hearing and smell

forebrain

prosencephalon

division: telencephalon and diencephalon

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components: cerebral cortex and olfactory brain, limbic system, optic chiasm (crossing of the vision nerves

limbic

means border thalamus, epithalamus, and hypothalamus

chiasm

means crossing

midbrain

mesencephalon

division: mesencephalon

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components: vision and hearing bodies, posture, and muscle control, limbic system

hindbrain

rhombencephalon

division: metencephalon

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components: cerebellum and pons

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division: myelencephalon

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components: medulla oblongata

spinal cord

caudal continuation of the medulla oblongata

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passes through the opening in the occipital bone

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carries all of the tracts that influence the innervation of the limbs and lower part of the body

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the pathway for impulses going to and from the brain