human antomy Flashcards
Sensory input—gathering information
To monitor changes occurring inside and
outside the body
-Changes = stimuli
Integration
To process and interpret sensory input and
decide if action is needed
Motor output
A response to integrated stimuli
- The response activates muscles or glands
Peripheral nervous system (PNS)
Nerves outside the brain and spinal cord
- Spinal nerves
- Cranial nerves
Central nervous system (CNS)
Brain
- Spinal cord
Sensory (afferent) division
Nerve fibers that carry information to the
central nervous system
Motor (efferent) division
Nerve fibers that carry impulses away from the
central nervous system
Motor (efferent) division (continued)
Two subdivisions
- Somatic nervous system = voluntary
- Autonomic nervous system = involuntary
Astrocytes
Abundant, star-shaped cells
- Brace neurons
- Form barrier between capillaries and neurons
- Control the chemical environment of
the brain
Support cells in the CNS are grouped together as
“neuroglia”
Function: to support, insulate, and protect
neurons
Microglia
Spiderlike phagocytes
- Dispose of debris
Ependymal cells
Line cavities of the brain and spinal cord
- Circulate cerebrospinal fluid
Nissl substance
Specialized rough endoplasmic reticulum
Cell body
Nucleus
- Large nucleolus
Schwann cells
Form myelin sheath in the peripheral nervous
system
Satellite cells
Protect neuron cell bodies
Oligodendrocytes
Wrap around nerve fibers in the central
nervous system
- Produce myelin sheaths
Myelin sheath
whitish, fatty material covering
axons
Neurons = nerve cells
Cells specialized to transmit messages
Major regions of neurons
Cell body—nucleus and metabolic center
of the cell
- Processes—fibers that extend from the
cell body
Axons end in axonal terminals
Axonal terminals contain vesicles with
neurotransmitters
Neurofibrils
Intermediate cytoskeleton
Maintains cell shape
Nodes of Ranvier
gaps in myelin sheath along
the axon
Processes outside the cell body
Dendrites—conduct impulses toward the cell
body
- Axons—conduct impulses away from the cell
body
Schwann cells
produce myelin sheaths in jelly
roll–like fashion
Axonal terminals are separated from the next
neuron by a gap
Synaptic cleft—gap between adjacent neurons
- Synapse—junction between nerves
Most neuron cell bodies are found in the central
nervous system
Gray matter—cell bodies and unmyelinated
fibers
- Nuclei—clusters of cell bodies within the
white matter of the central nervous system
Sensory (afferent) neurons
Carry impulses from the sensory receptors to
the CNS
Cutaneous sense organs
Proprioceptors—detect stretch or tension
Ganglia
collections of cell bodies outside the
central nervous system
Motor (efferent) neurons
Carry impulses from the central nervous
system to viscera, muscles, or glands
Interneurons (association neurons)
Found in neural pathways in the central
nervous system
Connect sensory and motor neurons
Multipolar neurons
many extensions from the
cell body
Bipolar neurons
one axon and one dendrite
Unipolar neurons
have a short single process
leaving the cell body
Irritability
Ability to respond to stimuli
what does the exchange of ions do
The exchange of ions initiates an action potential
in the neuron
Conductivity
Ability to transmit an impulse
Repolarization
Potassium ions rush out of the neuron after
sodium ions rush in, which repolarizes the
membrane
The sodium-potassium pump, using ATP,
restores the original configuration
Action potential
If the action potential (nerve impulse) starts, it
is propagated over the entire axon
Impulses travel faster when fibers have a
myelin sheath
Resting neuron
The plasma membrane at rest is polarized
Fewer positive ions are inside the cell than
outside the cell
Depolarization
A stimulus depolarizes the neuron’s
membrane
A depolarized membrane allows sodium (Na+)
to flow inside the membrane
Impulses are able to cross the synapse to another
nerve
Neurotransmitter is released from a nerve’s
axon terminal
The dendrite of the next neuron has receptors
that are stimulated by the neurotransmitter
An action potential is started in the dendrite
