Download K - Shelton State

Peripheral nervous system (PNS)
Central nervous system (CNS)
Cranial nerves and spinal nerves
Communication lines between the
CNS and the rest of the body
Brain and spinal cord
Integrative and control centers
Sensory (afferent) division
Somatic and visceral sensory
nerve fibers
Conducts impulses from
receptors to the CNS
Somatic sensory
fiber
Motor (efferent) division
Motor nerve fibers
Conducts impulses from the CNS
to effectors (muscles and glands)
Somatic nervous
system
Somatic motor
(voluntary)
Conducts impulses
from the CNS to
skeletal muscles
Skin
Visceral sensory fiber
Stomach
Autonomic nervous
system (ANS)
Visceral motor
(involuntary)
Conducts impulses
from the CNS to
cardiac muscles,
smooth muscles,
and glands
Skeletal
muscle
Motor fiber of somatic nervous system
Sympathetic division
Mobilizes body
systems during activity
Sympathetic motor fiber of ANS
Structure
Function
Sensory (afferent)
division of PNS
Motor (efferent)
division of PNS
Parasympathetic motor fiber of ANS
Parasympathetic
division
Conserves energy
Promotes housekeeping functions
during rest
Heart
Bladder
Capillary
Neuron
Astrocyte
Myelin sheath
Process of
oligodendrocyte
Nerve
fibers
Neuron
Microglial
cell
Fluid-filled cavity
Ependymal
cells
Brain or
spinal cord
tissue
Satellite
cells
Cell body of neuron
Schwann cells
(forming myelin sheath)
Nerve fiber
Dendrites
(receptive
regions)
Cell body
(biosynthetic center
and receptive region)
Neuron cell body
Nucleolus
Nucleus
Nissl bodies
Axon
(a)
(impulse
Impulse
generating
and conducting direction
region)
Axon hillock
Neurilemma
Dendritic
spine
Node of Ranvier
Schwann cell
(one internode)
Terminal
branches
Axon terminals
(secretory
region)
Schwann cell
plasma membrane
Schwann cell
cytoplasm
Axon
1
A Schwann cell
envelopes an axon.
Schwann cell
nucleus
2
The Schwann cell then
rotates around the axon,
wrapping its plasma
membrane loosely around
it in successive layers.
Neurilemma
Myelin sheath
(a) Myelination of a nerve
fiber (axon)
3
The Schwann cell
cytoplasm is forced from
between the membranes.
The tight membrane
wrappings surrounding
the axon form the myelin
sheath.
Receptor
Neurotransmitter chemical
attached to receptor
Na+
Na+
Chemical
binds
K+
Closed
K+
Open
(a) Chemically (ligand) gated ion channels open when the
appropriate neurotransmitter binds to the receptor,
allowing (in this case) simultaneous movement of
Na+ and K+.
Na+
Na+
Membrane
voltage
changes
Closed
Open
(b) Voltage-gated ion channels open and close in response
to changes in membrane voltage.
Voltmeter
Plasma
membrane
Ground electrode
outside cell
Microelectrode
inside cell
Axon
Neuron
The concentrations of Na+ and K+ on each side of the membrane are different.
Outside cell
The Na+ concentration
is higher outside the
cell.
K+
(5 mM )
Na+
(140 mM )
The K+ concentration
is higher inside the
cell.
K+
(140 mM )
Na+
(15 mM )
Inside cell
The permeabilities of Na+ and K+ across the
membrane are different.
Suppose a cell has only K+ channels...
K+ loss through abundant leakage
channels establishes a negative
membrane potential.
K+ leakage channels
K+
K+
K+
K+
K+
K+
Na+
K
K+
Na+
K+
K+
Na+
K+
K+
Na+
Na+-K+ ATPases (pumps)
maintain the concentration
gradients of Na+ and K+
across the membrane.
Cell interior
–90 mV
Now, let’s add some Na+ channels to our cell...
Na+ entry through leakage channels reduces
the negative membrane potential slightly.
Cell interior
–70 mV
Na+-K+ pump
Cell interior
–70 mV
Finally, let’s add a pump to compensate
for leaking ions.
Na+-K+ ATPases (pumps) maintain the
concentration gradients, resulting in the
resting membrane potential.
The concentrations of Na+ and K+ on each side
of the membrane are different.
The Na+
concentration
is higher
outside the
cell.
The K+
concentration
is higher
inside the
cell.
Outside cell
(5 mM )
Na+
(140 mM )
K+
(140 mM )
Na+
(15 mM )
K+
Inside cell
Na+-K+ ATPases (pumps) maintain
the concentration gradients of Na+
and K+ across the membrane.
The permeabilities of Na+ and K+ across the
membrane are different.
Suppose a cell has only K+ channels...
K+
K+
K+
K+
K+
leakage channels
Cell interior
–90 mV
K+ loss through
abundant leakage
channels establishes
a negative membrane
potential.
Stimulus
Depolarized region
Plasma
membrane
(a) Depolarization: A small patch of the
membrane (red area) has become depolarized.
Spread of depolarization: The local currents
(black arrows) that are created depolarize
adjacent membrane areas and allow the wave of
depolarization to spread.
SHINGLES