Nervous System (ch. 7)

functions of the nervous system

sensory input

integration

motor output

sensory input

gathering information

sensory receptors monitor changes (stimuli) occurring inside and outside the body

integration

nervous system processes and interprets sensory input and decides whether action is needed

motor output

a response (effect) activates muscles or glands

nervous system classifications are based on

structures (structural classification)

activities (functional classification)

structural classification

central nervous system (CNS)

peripheral nervous system (PNS)

CNS organs

brain and spinal cord

CNS functions

integration; command center

interprets incoming sensory information

issues outgoing instructions

PNS nerves

nerves that extend from the brain and spine

spinal nerves

carry impulses to and from the spinal cord

cranial nerves

carry impulses to and from the bran

PNS functions

serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles

functional classifications

sensory (afferent) division

motor (efferent) division

sensory (afferent) division

nerve fibers carry information TO the CNS

somatic sensory and visceral sensory nerve fibers

somatic sensory (afferent) nerve fibers

carry information from the skin, skeletal muscles, and joints

visceral sensory (afferent) nerve fibers

carry information from visceral organs (internal organs)

motor (efferent) division

nerve fibers that carry impulses away from the CNS organs to effector organs (muscles and glands)

somatic nervous system

voluntary

\
consciously controls skeletal muscles

autonomic nervous system

involuntary

\
automatically controls smooth and cardiac muscles and glands

supporting cells of nervous tissue are called

neuroglia

functions of supporting cells

support, insulate, and protect neurons

astrocytes

CNS

\
abundant

\
star-shaped cells

\
brace and anchor neurons to blood capillaries

\
determine permeability and exchanges between blood capillaries and neurons

\
protect neurons from harmful substances in blood

\
control the chemical environment of the brain

microglia

CNS

\
spider-like cells

\
monitor health of nearby neurons

\
dispose of debris

\
connect neurons

ependymal cells

CNS

\
line cavities of the brain and spinal cord

\
cilia assist with circulation of CSF

oligodendrocytes

CNS

\
wrap around nerve fibers in the CNS

\
produce myelin sheaths

schwann cells

PNS

\
form myelin sheath around nerve fibers in the PNS

satellite cells

PNS

\
protect and cushion neuron cell bodies

neurons

nerve cells

cell body

nucleus and metabolic center of the cell

processes

fibers that extend from the cell body

nissl bodies

rough endoplasmic reticulum

neurofibrils

intermediate filaments that maintain cell shape

dendrites

conduct impulses toward the cell body

axons

conduct impulses away from the cell body

neurons only have ______ axon arising from the cell body at the axon hillock

one

axon terminals

contain vesicles with neurotransmitters

synaptic cleft

gap between axon terminals and the next neuron

synapse

functional junction between nerves where a nerve impulse is transmitted

myelin

white, fatty material covering axons

\
protects and insulates fibers

\
speeds nerve impulse transmission

myelin sheaths

schwann cells- wrap axons in jelly-roll like fashion to form myelin sheath

\--neurilemma

\---nodes of Ranvier

\
oligodendrocytes- produce myelin sheaths around axons

\--lacks neurilemma

neurilemma

part of schwann cell external to the myelin sheath

nodes of ranvier

gaps in myelin sheath along the axon

nuclei

clusters of cell bodies in the CNS

ganglia

collections of cell bodies outside the CNS in the PNS

tracts

bundles of nerve fibers in the CNS

nerves

bundles of nerve fibers in the PNS

white matter

collection of myelinated tracts/fibers

gray matter

mostly unmyelinated fibers and cell bodies

sensory receptors

cutaneous sense organs in skin

\
proprioceptors in muscles and tendons

interneurons

association neurons

\
cell bodies located in the CNS

\
connect sensory and motor neurons

multipolar neurons

many extensions from the cell body

\
all motor and interneurons are multipolar

\
most common structural type

bipolar neurons

one axon and one dendrite

\
located in special sense organs, such as nose and eye

\
rare in adults

unipolar neurons

have a short single process leaving the cell body

\
sensory neurons found in PNS ganglia

\
conduct impulses both toward and away from the cell body

irritability

ability to respond to a stimulus and convert it to a nerve impulse

conductivity

ability to transmit the impulse to other neurons, muscles, or glands

transmission DOWN the neuron is

electrical

transmission to NEXT neuron is

chemical

reflexes

rapid, predictable, and involuntary responses to stimuli

reflex arc

neural pathways reflexes occur over

2 types of reflexes

somatic

autonomic

somatic reflexes

involuntary, skeletal muscles

\
ex. pulling hand away from hot object

autonomic reflexes

involuntary, smooth muscles

\
ex. regulation of smooth muscles, heart, BP, glands, digestive system

5 elements of a reflex arc

sensory receptor

\
sensory neuron

\
integration center

\
motor neuron

\
effector organ

sensory receptor

reacts to a stimulus

sensory neuron

carries message to integration center

integration center

CNS

\
processes information and directs motor output

motor neuron

carries message to an effector

effector organ

the muscle or gland to be stimulated

two-neuron reflex arc

simplest type

\
no interneuron present

\
ex. patellar (knee-jerk) reflex

three-neuron reflex arc

consists of 5 elements

\
interneuron is present

\
ex. flexor (withdrawal) reflex

brain regions

cerebral hemispheres

diencephalon

brain stem

cerebellum

gyri

ridges

grooves

sulci

fissures

deeper grooves

3 main regions of cerebral hemisphere

cortex

white matter

basal nuclei

cerebral cortex

primary somatic sensory area

primary motor area

broca’s area

primary somatic sensory area

located in parietal lobe posterior to central sulcus

\
receives impulses from body’s sensory receptors

sensory homunculus

a spatial map

left side of brain controls

right side of body

right side of brain controls

left side of body

primary motor area

located anterior to the central sulcus in the frontal lobe

\
allows us to consciously move skeletal muscles

\
motor neurons form pyramidal tract (descend to spinal cord)

motor homunculus

a spatial map

broca’s area

motor speech area

\
involved in out ability to speak

\
usually in left hemisphere

anterior association area

frontal lobe

posterior association area

posterior cortex

speech area

for sounding out words

cerebral white matter

composed of fiber tracts deep to the gray matter

corpus callosum

connects cerebral hemispheres

tracts

known as commissures

association fiber tracts connect

areas within a hemisphere

projection fiber tracts connect

the cerebrum with lower CNS centers

basal nuclei

“islands” of gray matter buried deep within the white matter of the cerebrum

\
regulate voluntary motor activities by modifying instructions sent to skeletal muscles by the primary motor cortex

diencephalon

sits on top of the brain stem

\
enclosed by the cerebral hemispheres

\
made of 3 structures

\-thalamus

\-hypothalamus

\-epithalamus

thalamus

encloses the 3rd ventricle

\
relay station for sensory impulses passing upward to the cerebral cortex

\
transfers impulses to the correct part of the cortex for localization and interpretation

hypothalamus

makes up the floor of the diencephalon

\
important autonomic NS center

* regulates: body temp, water balance, metabolism

\
houses limbic center for emotions

\
regulates pituitary gland

\
houses mammillary bodies for olfaction

epithalamus

forms roof of 3rd ventricle

\
houses pineal body

\
includes choroid plexus

choroid plexus

forms CSF

brain stem

attaches to the spinal cord

\
part of the brain stem:

* midbrain
* pons
* medulla oblongata

midbrain

extends from mamillary bodies to the pons inferiorly

\
cerebral aqueduct connects the 3rd and 4th ventricles

\
two bulging fiber tracts (cerebral peduncles) convey ascending and descending impulses

\
four rounded protrusions (corpora quadrigemina) are visual and auditory reflex centers

pons

rounded structure protruding just below the midbrain

\
mostly composed of fiber tracts

\
includes nuclei involved in the control of breathing