4) Neural Tissue Anatomy

central nervous system (CNS) includes…

brain, spinal cord

CNS functions

sensory processing, motor coordination, higher functions (memory, learning, emotion)

peripheral nervous system (PNS) includes…

all neural tissue outside CNS

PNS connects CNS with…

peripheral receptors and effectors

afferent carries…

sensory info from receptors to CNS

efferent carries…

motor commands from CNS to PNS muscles and glands

how does the nervous system compare to the endocrine system?

faster, shorter responses

nerves consist of…

bundles of axons with connective tissue and blood vessels

2 functional cell types in neural tissue

neurons, neuroglia (glial cells)

neuron function

send and receive signals

neuroglia (glial cells) function

support and protect neurons

why are neurons considered integrators?

may receive input from numerous other neurons

dendrites function

increase receptive surface area for signals

soma (cell body) contains…

nucleus and organelles

soma (cell body) functions as the…

metabolic and synthetic center

axon function

conduct impulses away from cell body

axon hillock function

where impulses originate (trigger zone)

nissl bodies function

rough ER and free ribosomes important for protein synthesis

initial segment is…

part of axon closest to axon hillock

telodendria

terminal branches of axons

synaptic end bulbs function

release neurotransmitters

varicosities

release neurotransmitters to smooth muscle

myelin function

increases AP speed, makes nerves look white

cell that myelinates in CNS

oligodendrocytes

cell that myelinates in PNS

schwann cell

other than location, how do oligodendrocytes and schwann cells differ?

1 oligodendrocyte can myelinate up to 40 axons and schwann cells wrap around a single axon

internodes are…

myelinated segments of axons

nodes of ranvier are…

gaps between myelination that have Na and K channels

direction of fast axonal transport

both

how does fast axonal transport move substances?

microtubules and motor proteins

direction of fast anterograde transport

from cell body to axon terminals

materials of fast anterograde transport

nutrients, enzymes, mitochondria, neurotransmitter vesicles

direction of fast retrograde transport

from axon terminals to cell body

materials of fast retrograde transport

trophic chemicals, recycled vesicles, opportunistic pathogens (tetanus, rabies, polio)

direction of slow axonal transport

from cell body to terminals

slow axonal transport function

provide/replenish axoplasm to axons

injury to the soma of a peripheral nerve leads to…

permanent loss and degeneration of the neuron

damage to a peripheral nerve axon leads to…

degeneration of distal part of axon and proximal part of the 1st node of ranvier

regeneration of peripheral nerve axons starst at…

node of ranvier

average rate of growth after damage to a peripheral nerve axon

1cm/month

do unmyelinated fibers and dendrites regenerate in the same way as axons?

no

anaxonic neurons have…

multiple processes without a clearly distinguishable axon

anaxonic neurons location

brain, sense organs

bipolar neurons have…

2 processes separated by soma

bipolar neuron location

special sense organs

unipolar neurons have…

1 elongated process with soma off to side

unipolar neurons location

PNS sensory neurons

multipolar neurons have…

1 axon and multiple dendrites

multipolar neurons location

CNS: all skeletal (somatic) motor neurons

afferent neurons monitor…

internal environment (visceral sensory neurons) and external environment (somatic sensory neurons)

interneurons location

CNS

____% of all neurons are interneurons

99

define synaptic cleft

gap that separates presynaptic and postsynaptic membrane

what type of synapse is most common?

chemical

electrical synapses communicate through…

gap junctions (no synaptic cleft)

what kind of synapse is generally faster?

electrical

____% of cells in CNS are glial cells

90

ependymal cell function

CSF production and circulation

what kind of cells are ependymal cells

cuboidal/columnar

ependymal cells have…

microvilli, cilia, tight junctions

microglia cell function

phagocytic, remove cellular debris

what within myelin is responsible for white color?

lipid

what within grey matter is responsible for the grey color?

nissl bodies

________ are the most common glial cell in CNS

astrocytes

astrocytes form…

blood brain barrier

astrocyte function

regulate ions, nutrients, neurotransmitters, injury response

glial cells of the CNS

astrocytes, oligodendrocytes, microglia, ependymal cells

satellite cell function

regulate exchange of materials between neurons and interstitial fluid

satellite cells location

surround soma of neurons in PNS ganglia

ganglia are…

collections of cell bodies in PNS

glial cells in PNS

schwann cells, satellite cells

epineurium surrounds…

entire peripheral nerve, including fascicles and blood vessels

perineurium surrounds…

fascicles (bundle of nerve fibers)

endoneurium surrounds…

individual nerve fibers

grey matter is made of…

neuron somas

white matter is made of…

neuron fibers and dendrites

grey matter location

outer brain, inner spinal cord

white matter location

inner brain, outer spinal cord