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Chapter 8 the nervous system (8.3 (characteristics of a nerve impulse (All…
Chapter 8 the nervous system
8.1 Anatomical & Functional Divisions
Anatomical
Central Nervous System
(CNS) Brain & Spinal Cord
Peripheral Nervous System
(PNS) Sensory & Motor neurons
Functional
Afferent Division
Receptors send info from PNS to CNS
Efferent Division
Send messages to PNS motor neurons from CNS
Somatic Nervous system
skeletal muscle
Autonomic nervous system
Parasynthetic
decrease HR
Sympathetic
increase HR
8.2 Neurons & Neuroglia
Structural classification
Multipolar neuron
two or more dendrities and axon
Unipolar neuron
one dendrite & axon cell body off to side
Bipolar neuron
one dendrite & one axon cell body between them
Functional Classification
Sensory neurons
somatic sensory neurons
Pns
afferent neurons
input information to cns
location of receptors
carry sensory impulses from sensory receptors to cns
visceral sensory neuron
motor neurons
pns
efferent neurons
carry motor impulses away from cns and to effectors
output information from cns
effectors= muscles & glands
somatic motor neurons
visceral motor neurons
sympathetic (adrenergic)
parasympathtic (cholinergic)
interneurons
cns
link other neurons together
General structures of neurons
dendrites
axon (white matter)
cell body (grey matter)
synaptic terminal
8.3
the rmp of -70 mvp can be sirupted or changed in one of twp directions
more negative= hyperpolarization
less negative= depolarization
the cell membrane of a neuron must be depolarized in order for a certain ion channels to open and therefore start a nerve impulse
resting nerve cells
DEF: potential difference= the differance in electrical charge betweeen 2 points
the resting membrane potential of aneuron is results from the distribution of ions across the cell membrane
K+ high inside
Na+ high outside
Cl- high outside
negatively charged proteins or anions high inside
recall that these ion concentrations are maintained by active transport mechanisms
the rmp of a nerve cell is measured to be -70mv
as long as the rmp is anerve cell is undistributed it remains polarized. In order for a nerve impulse to be started or propagated in a nerve cekk this resulting potental must be distributed
a resting neurons cell membrane is said to be polarized= electrically charged
consequently a potential difference exists across this resting cell membrane
Action potential
when threshold potential is reached the rapid of NA+ channels result in rapid depolarization
this event is called the action potential
the action potential represents the star of the nerve impulse on a neuron
when the resting membrane potential of a neuron is depolarized to -55 mv, thresshold poential is reached
the threshold potential for a neuron is -55 mv
a threshold stimulus= +15 mv
nerve impulse transmission
DEF: nerve impulses= the propagation of action potentials along a nerve fiber
An NI is simillar to a row of dominos falling
Anerve impulse begins on a dendrite runs towards the cell body through the cell body then down the axon
the NI is an electrical impulse
characteristics of a nerve impulse
All or nothing response= if a nerve cell responds at all it responds completely
Summation= many subthreshold stimuli recieved one after another may allow threshold potential to be rreached
refractory period= the period following a NI when a threshold stimulus cannot produce another NI
Conduction= the manner in which the NI runs down the neuron fiber
8.5
meninges
brain
arachnoid
middle klayer
thin net like membrane
beneath the arachnoid mater lies a wide space called the sub arachnoid space
this space is fillled with cerebrospinal fluid
pia mater
inner layer that clings to brain surface
very thin delicate ct
many nerves & blood vessels= nourishment
dips into grooves & contours
Dura mater
contains many blood vessels and nerves
Note: DM splits into two layers where it encloses the dural sinuses
tough white fibrous ct
outermost membrane that is attached to the inner periosteum of the skull
Spinal cord:
the space betweeen the dura mater and the bone is called the epidural space and is filled with loose ct and fat
CSF fills the subarachnoid space and central canal
the dura mater is not attached to the bone of the vertebrae in the brain where it is attached to the skull
8.6
gross structure of spinal cord
note cervical and lumbar eth
cauda equina in which the lower lumbar and sacral nerves travel downward
contains 31 segments
filum terminale that represents distal portion of the tail
length= about 17 inches
start= foramen magnum
end= tapers to point and terminates near the intervertebral disc
cross sectional anatomy of spinal cord
a cross section of the spinal cord resembles a butterfly with its wings outspread surrounded by white matter
gray matter or butterfly= bundkes of cell bodies
lateral horns
anterial horns
posterior horns
note location of:
gray commisure
anterior median fissure
central canal
posterior median sulcusk
kahoots
synaptic knobs occur at the ends of
dentrities
neurotransmitters are released from the
synaptic terminals/knobs
which type of synapse dominates the nervous system
chemical
the ion needed to initiate the release of acetylcholine into the synaptic cleft is
calcium
adrengic synapes release the neurotransmitter
norepinephrine
which of the following lists the parts of a reflex arc in the correct order
receptor sensory neuron interneuron motor neuron effector
the following is a series of events that occur at a typical cholinergic synapse. Place the events in the correct
arriving action potential depolarizes, calcium ions, ach diffuses, sodium channels on post, a ch release, depolarization ends as, the synaptic knob
the specialized membranes that protect the spinal cord are termed
spinal meninges
blood vessles servicing the spinal cord are found in the
pia mater
the dural sinuses are located
dura mater
What are the two components of the efferent motor pathway?
Somatic /and autonomic
the cytoplasmic extensions that together with the cell body, provide the main receptive surfaces for neurons are the
dendrites
the largest and most numerous of the glial cells in the central nervous system
astrocytes
the white matter of the spinal cord contains
bundles of axons that share common origins
Masses of myelinated nerve fibers appear
white
most neurons in the brain are
multipolar
What makes up the cns
brain and spinal cord
What makes up the pns
afferent and efferent
two divisions of the automonic nervous system
parasympathetic and sympathetic
aggregations of ribbosomes in neurons are reffered to as
nissel bodies
neurons that have one axon and one dendrite with the soma between them are called
bipolar
the poster horns of the spinal cord
sensory nuclei
the myelin sheaths that surround of the axons of some of the neurons in the cns are formed by
oligodendrocytes
general structure if neuron
dendrites
axon
cell body grey matter
synaptic terminal
axons crossing from one side of the spinal cord to the other within the gray matter are found in the
gray commisure
the projections of gray matter toward the outer surface of the spinal cord are called
horns
the part of the peripheral nervous system that brings info to the central nervous system
afferent division
which type of synapse dominates the nervous systemic issue
chemical
neurotransmitters are released from
synaptic terminals/ knobs
two types of synapse
electrical: fastest
chemical: most abundment