central nervous system
brain and spinal cord
peripheral nervous system
nerves
sensory nerves (afferent)
impulses are sent to the CNS; detect changes inside and outside of the body
integration
within CNS; processing incoming sensory input decision making
motor
impulse sent from CNS to effectors to cause response
neurons
nerve cells; conduct impulses
neuroglia
surrounds nerve cells; do not conduct impulses
parts of a neuron
cell body, dendrites, axon
cell body
cytoplasm, mitochondria, lysosomes, microtubules, golgi apparatus, nucleus
nissl bodies
chromatophilic substance that consists mainly of rough er
dendrites
receive input; highly branched. provide many receptors; can be 1 or more
axon
transmits input; carries the input away from the cell body; usually one long fiber
impulses travel
dendrite-> cell body-> axon
multipolar
1 axon and MANY dendrites
bipolar
1 axon and 1 dendrite
unipolar
1 process which splits into 2 branches, the peripheral and central processs
sensory neurons (afferent)
carry impulses from peripheral body parts to CNS
interneurons
lie within the CNS and form links with other neurons
motor neurons (efferent)
carry impulses from CNS to peripheral body parts
neuroglial cells in PNS
schwann and satellite
neuroglial cells in CNS
astrocytes; oligodendrocytes; microglia; ependyma
schwann cell
produce myelin on myelinated neurons
how do schwann cells wrap around
tightly wrap around fibers, forming a myelin sheath; just neurilemma with no myelin sheath
satellite cell
clusters of neuron cell bodies called ganglia
myelinated fiber
fiber that has a myelin sheath; impulse travels faster
unmyelinated fiber
fiber that does not have a myelin sheath; impulse travels slower
gray matter
nervous tissue containing lots of cell bodies and unmyelinated fibers
white matter
nervous tissue containing lots of myelinated fibers
astrocyte
large star shaped cells between neurons and blood vessels; structural support, communication, and transportation between blood vessels and neurons
oligodendrocytes
shaped like astrocytes with fewer processes, occur in rows along axons; form myelin sheath in the CNS ( NO neurilemma)
microglia
small cells with few processes found throughout CNS; structural support and phagocytosis
ependyma
cuboidal and columnar cells in the brain and spinal cord that line the cavities; help with diffusion
regeneration in CNS
no regeneration; no endoneurial tube and no neurilemma
regeneration in PNS
might occur; bc the endoneurium's presence may prevent scar tissue from coming in before the process can regrow
synapse
junction between axon of one neuron and dendrite or cell body of another neuron
presynaptic fiber
neuron which sends impulse to synapse; releases neurotransmitters into synaptic cleft
postsynaptic fiber
neuron which has receptors for the neurotransmitters
first step in synaptic transmission
Presynaptic knob of axon contains vesicles filled with neurotransmitters.
second step in synaptic transmission
When impulse reaches knob, Ca++ diffuses into cytoplasm.
third step in synaptic transmission
Vesicles move to membrane and release neurotransmitters into cleft.
fourth step in synaptic transmission
Neurotransmitters cross cleft and bind to receptors on postsynaptic membrane of neuron (either dendrite or cell body)
fifth step in synaptic transmission
If enough neurotransmitters are present, an action potential will occur.
sixth step in synaptic transmission
Neurotransmitters are either decomposed or they move back into presynaptic knob.
neuron potential
the concentration of ions on either side of the membrane affects its charge distribution
changes in potentials
when a stimulus encounters a neuron, it responds by changing its permeability to various ions, which affects the potentional
hyperpolarized
the resting membrane becomes more negative
depolarized
the resting membrane becomes more positive
nerve impulse
if stimulus is strong enough it cause Na gates to open Na flows into cell, depolarizing membrane action potential is reached at +30 mV K+gates open K+ moves out, repolarizing membrane hyperpolarizes for brief moment active transport pumps Na out and K in
resting potential
The charge distribution when a nerve is at rest. No impulse being conducted, so membrane is not very permeable to POTASSIUM (K+) and even less permeable to SODIUM (Na+). Active transport has to be used to pump K+ in and Na+ out. More negatively charged ions on the inside of the cell so more positive particles are going to move in (attraction): More Na+ on outside, K+ on inside Membrane is positive on the outside, negative on the inside Membrane is said to be polarized -70mV- is the difference in charges (resting potential)
action potential
the rapid sequence of Na and K movements
nerve impulse
chain reaction of action potentials
all-or-none response
if a neuron responds at all, it responds COMPLETELY or conducts COMPLETELY or not at all
refractory period
a short time period after a nerve impulse where a stimulus will not conduct the neuron
saltatory conduction
type of impulse conduction along myelinated fibers
nerve impulse speed
thick faster than thin myelinated faster than unmyelinated
excitatory postsynaptic potential
neurotransmitter triggers Na+ gates to open and membrane is depolarized (more likely reach action potential)
inhibitory postsynaptic potential
neurotransmitter triggers K+ gates to open and membrane is hyperpolarized (less likely to reach action potential)
facilitation
if a neuron receives a net excitatory stimulation, but is subthreshold it is more susceptible to an action potential the next time
monoamines
modifications of amino acids
epinephrine
boost of energy
dopamine
feel good hormone
serotonin
mood stabilizer
amino acids
unmodified amino acids
glycine
inhibitory neurons in brain and spinal cord
gamma-aminobutyric acid (GABA)
inhibitory neurons in brain and spinal cord
peptides
short chains of amino acids
substance P
pain perception
endorphins
reduces pain
convergence
when a neuron receives impulses from 2 or more other neurons allows the brain to receive info from different regions of the body and respond in a special way
divergence
when 1 neuron sends impulses to 2 or more other neurons-results in an amplified response
sensory fibers
contains only sensory fibers (afferent)
motor fibers
contains only motor fibers (efferent)
mixed fibers
contains both sensory and motor fibers
general somatic efferent fibers
carry impulses from CNS to skeletal muscles
general visceral efferent fibers
carry impulses from CNS to smooth muscles and glands
general somatic afferent fibers
carry impulses from skeletal muscles and skin to CNS
general visceral afferent fibers
carry impulses from smooth muscles and glands to CNS
reflex arc
simple impulse pathway during a reflex
receptor
specialized nerve endings stimulated by change
effector
smooth muscle or gland that responds
meninges
found beneath the bone and soft tissues of nervous system; brain and skull, spinal cord and vertebral column protect the brain and spinal cord
3 layers outer to inner
dura mater arachnoid mater pia mater
meningitis
inflammation of the meninges
spinal cord
31 segments ends between 1 and 2 lumbar relays impulses and info between body and CNS