Nervous System Flashcards
Neuron Cell
functional unit of the nervous system
Cell body
cytoplasm, nucleus, other organelles
Dendrites
multiple processes that bring impulses to cell body
axon
single process that carries impulses away from cell body
Afferent (sensory) neurons
send impulses from receptors to CNS
Transducer
converts sensory signal to an impulse
Efferent (motor) neurons
send impulses from CNS (brain and nerve cord) to effectors (muscles, glands, etc)
Interneurons
connect afferent and efferent neurons processing
Neuroglial (glial) cells
support neurons
ex. oligodendrocyte
ex. astrocyte - store and provide nutrients and ions
lay down insulating myelin sheath around axons
store and provide nutrients and ions
Nerve structure
bundle of neurons wrapped in connective tissue
ganglia
bundles of neuron cell bodies; lie outside the CNS;
some coordination of impulse transmission
axon inside
Outside the axon (interstitial fluid)
Inside the axon (cytoplasm)
Outside the axon (interstitial fluid)
Axon Structure
a lipid bilayer membrane with imbedded proteins (like other cells)
1) receptor proteins – bind to molecules, allowing cell to respond
(Pump)
pumps – move substances against concentration gradient
channels – allow a flow with concentration gradient
(Pump)
leakage channels – allow a two-way flow; always open
voltage-gated channels – open and close in response to
change in electric charge
chemical or ligand-gated channels – open and close in
response to the binding of a molecule
4) pumps and channels make a cell’s membrane semipermeable
axon and muscle cell membranes
only have polarity or are electrostatically charged
the strength of this charge when at rest, the neuron not firing
(i.e. resting potential) is
-70 mV
Voltage
measures the amount of difference in electrical charge
current
flow of electric charges
current of a battery involves a flow of…
electrons
current of a neuron involves a pair of…
ions
3 forces act on a axon’s membrane to influence ion movement across it
passive diffusion of ions
passive electrostatic pressure on ions
active transport (energy used) or pumping of ions against their
concentration gradient
cystol
(liquid part of cytoplasm vs organelles);
outside is interstitial fluid (IF) or extracellular fluid
there is 10x more …. outside than inside
Na+
Action Potential has 2 phases
Depolarization(inside becomes less negative/more positive)
Repolarization(a restoring of the polarity of the RMP)
what triggers it?
mainly neurotransmitter, then binds to protein receptor
If depolarization reaches about -55 mV
AP is triggered
Repolarization phase
right after voltage-gated Na+ channels open at one spot along
the axon, more slowly responding voltage-gated K+ channels open
restores polarity (repolarization) of axon at this spot
K+ leaving interior
speed of action pontential
speed about 1m/sec (2.5 mph)
Node of Ranvier
unmyelinated section of axon, packed with Na+ channels
Multiple Sclerosis
myelin sheath of axons is destroyed
cause of multiple sclerosis
sodium-potassium pumps are not present where sheath
was present
action potential cannot be propagated because it will not jump
across areas without pumps when no sheath is present
many different areas of the body can be attacked; symptoms
and severity therefore vary
a gap between two neurons or between a neuron and a
muscle or organ
synapses
Components of Synapses
presynaptic neuron - carries impulses to synapse
postsynaptic neuron - carries impulses away from synapse
synapse or synaptic cleft-between the two
Functioning of Synapses
ends of presyn neurons have vesicles containing neurotransmitter molecule
AP arriving at presyn knob triggers opening of voltage-gated Ca++ channels
ACh diffuses across the synapse and binds to receptors on chemical-gated or ligand-gated ion channels of postyn knob
In case of a muscle, a muscle contraction is triggered
Vertebrates mammals
reflex arc impulse travels from sensory nerve to motor nerve via spinal cord (often interneurons) to an effector, bypassing brain
Brain
Hindbrain, Medulla(heart rate, breathing, blood vessel diameter)
Cerebellum
equilibrium, posture, movement
pons
communication within cerebellum, between it and cerebellum
midbrain
relay visual and sound stimuli to cerebrum
Forebrain
thalamus analyze and relay sensory info to cerebrum; also awareness, acquiring knowledge
Hypothalamus
homeostatic control of hunger, thirst, and body temperature; also emotions, circadian rhythm
Cerebrum
Higher mental activities
Peripheral Nervous System
Outside brain and nerve cord
Efferent Division
Commands to muscle, glands
Somatic nervous system
innervates skeletal muscles (voluntary responses)
Autonomic Nervous system
innervates smooth muscle associated with organs, blood vessels
parasympathetic system
controls resting responses
sympathetic system
controls physical activites (fight or flight)
afferent division
info from sensory receptions
Sense Organs
Chemoreceptors
Olfaction
nasal cavity epithelium, mucous covered lined with olfactory receptor neurons with cilia at the end. Combo of 1000 different olfactory receptor, producecs 20,000 odors
Mechanoreceptors
light touch(just under epidermis, and around roots of hairs)
Pain receptor temp
below 10 degrees celsius(50 F) and 48 celsius (118 F)
Human Ear
pinna (auricle), auditory canal, tympanic membrane, ossicles, oval window, cochlea, cochlear nerve
Loudness =
numbers of hair stimulated
loss of hair =
hair detioration
saccule and utricle
static balance as stony particles, stimulate hairs they rest on
semicircular canals
rotational acceleration as fluid movement as fluid movement in three canals stimulates hair as body moves
retina
light sensitive rear wall eye
rods
majority 125 million of photoreceptors, colorless vision in dim light, concentrated at retina’s periphery
Cones
fewer 1 million and provide color vision in stronger light
Blind spot
lack of receptors at optic nerve
