MCAT Biology Ch13: The Nervous System Flashcards
cell body
specialized name - soma
nucleus, ER, and ribosomes
neurons
each carry out its own function
variety of diff. types
most mamm. insulated by myelin => prevent signal loss
not phys. connect, slight space between
dendrities
majority of neuron
receive information
transmit info to cell body => integrated at axon hillock
axon hillock
info integrated from cell body
enlargement at the begin of the axon
provides a connection between cell body and axon
axon
nerve fiber specialized to carry electrical message
oligodendrocytes
myelin produced by this in CNS
myelin
produced by Schwann cells in periphery and oligodendrocytes
nodes of Ranvier
small breaks in myelin sheath of axon membrane
critical to proper signal conduction
nerve terminal (synaptic bouton)
end of axon
enlarged and flattened to max. neurotransmission to next neuron
ensure proper production of neurotransmitter
synaptic cleft (synapse)
neurotransmitter released from axon terminal traverses the synaptic cleft and bind to receptors on second neuron
many common drugs modify this
Ways to remove neurotransmitters from synaptic cleft
depends on type of neurotransmitter involved
- broken down by enzymatic rxns
- use reuptake carriers to be recycled into presynaptic neuron
- diffuse out of the area
diff between electrical and chemical transmission
w/in - electricity
between - chem
afferent neuron
neurons that carry info from periphery to brain or spinal cord
sensory neurons
efferent neuron
motor neurons
interneuron
only involved in local circuits
nerves
many axons together
types of nerves
sensory, motor, or mixed
possible for disease to affect only motor and sensory neurons
refers to type of info they carry
mixed nerves
carry both sensory and motor info
two components of CNS
brain and spinal cord
brain
protected by protective skull
responsible for integration of sensory info, coordination of motor movement, and cognition
myelination presence distinguish between gray and white matter
division of brain
forebrain, midbrain, hindbrain
forebrain
broken down into telencephalon and diencephalon
telencephalon
part of forebrain
large portion if cerebral cortex
consists of left and right hemisphere
each hemisphere is indie, however comm. through corpus collosum
cerebral cortex
large portion of telencephalon
highly convoluted gray matter on surface of brain
responsible for highest-level functioning in nervous system, including creative thought and future planning
integrate sensory info and controls movement
inc. folds (gyri) in here => higher-level cognitive functions carried out
corpus collosum
hemis of telencephalon comm. through this
diencephalon
below and inside telencephalon
consists of thalamus and hypothalamus
thalamus
gateway to brain
all ascending sensory info passed through thalamus before begin relayed to cortex.
midbrain
relay point between more peripheral structures and forebrain
passes sensory and visual info to forebrain, while receiving motor instructions from forebrain and passing them to hindbrain
hindbrain
involuntary functions
made up of cerebellum, pons, and medulla
cerebellum
checks that motor signal sent from cortex is in agreement w/ sensory info coming from body
helps cerebellum to adjust to new situation
alcohol affect on cerebellum => people stagger
medulla
most highly conserved part of brain
responsible for modulating ventilation and heart rate and GI tone
spinal cord
hindbrain also connected to this
all structures below neck receive sensory and motor innervation here
sensory info enters here on dorsal side, whereas motor signals leave from ventral surface
hemispheres of telencephalon
each section sectioned in lobes:
- frontal
- parietal
- occipital
- temporal
each lobes has diff. function
4 sections of spinal cord
cervical, thoracic, lumbar, sacral
frotebra.
m base of skull to coccyx
runs through column w/ nerves entering and exiting at teach vertebra
integrating and distributing nerve signals for brain
can participate in simple reflex areas of their own
both gray and white matter (contains axons) in cross section
there are axons of motor and sensory neurons
vertebral column
protect spinal cord
series of bone (vertebrae) that form a hollow column
sensory neurons of spinal cord
bring info in from periphery and enter on dorsal (back) side of spinal cord
cell bodies found in dorsal root ganglia
dorsal root ganglia
cell bodies of sensory neurons of spinal cord found here.
motor neurons of spinal cord
exit the spinal cord ventrally
brain stem
most primitive part of brain
conserved from simple organisms
drive basic functions from breathing to heart beating
ex: resp. system driven by chemoreceptors in brain that are sensitive to CO2 levels.
PNS
12 pairs of cranial nerves and 31 pairs of spinal nerves
peripheral innervation divided into
somatic (SNS) and automatic (ANS) nervous system
SNS
voluntary movement
interface between neuron and muscle (w/o synapse) as neuromuscular junction
responsible for providing us w/ reflexes
don’t require input or integration from brain to function
two types of reflex arcs of SNS
monosynaptic and polysynaptic
usually serves as protective purpose
monosynaptic reflex of SNS
single synapse between sensory neuron that received the info and the motor neurons that responds
knee jerk (monosynaptic reflex of SNS)
patellar tendon stretched => info travels up sensory neuon => spinal cord => interface w/ motor neuro => contract quadriceps muscle => straightening
response is contraction
polysynaptic reflex of SNS
at least one interneuron between sensory and motor neuron
withdrawal reflex (polysynaptic reflex of SNS) ex: stepping on tack
jerk up => monosynaptic => maintain balance => incoming sensory info on leg jerked up => interneuron in spinal cord => motor neuron for supporting leg
ANS
involuntary nervous system
exerts great control over BP, ventilation dynamics, urination, digestion
can regulate each organ individually
can also have coordinated effects
primary diff. between SNS and ANS
ANS - two-neuron system
two neurons in ANS
preganglionic andc neuron
two work in series to transmit msgs
preganglionic neuron
first neuron of ANS
soma in CNS, whereas its axon travels to ganglion in PNS => synapses on cell body of postganglionic neurons => affects target tissue
preganglionic neuron
second neuron
soma in CNS, whereas its axon travels to ganglion in PNS => synapses on cell body of postganglionic neurons => affects target tissue
division of ANS
sympathetic and parasympathetic
sympathetic nervous system
fight or flight
increase blood flow to heart and skeletal muscle
dec. blood flow to GI tract and kidney
inc breathing and heart rate => supply oxygen meet demands of contracting skeletal muscles
pupils dilate
pregang neuron use acetylcholine; can also cause release of epinephrine
postgang neuron use norepinephrine
parasympathetic nervous system
inc. blood flow to organs of digestion and excretion w/ concomitant dec. in flow to skeletal muscle and heart
heart and ventilation rate would dec.
vagus nerve
one of 12 cranial nerves
responsible for many of parasympathetic effects in thoracic and abdominal cavities.
use acetylcholine as neurontransmitter at both pre/postgang.
3 varieties of sensory neurons
interoceptors, proprioceptors, and exteroceptors
interoceptors
sensory neurons monitor internal environment
proprioceptors
sensory neurons monitor for our position sense
exteroceptors
sensory neurons monitor external environment
nociceptors
sense pain and relay info to brain
eye
specialized organ that detects light (in form of photons)
most exposed of eye is covered by sclera
sclera
most exposed of eye is covered by a thick layer
not cont. around the eye
choroid
eye is supplied w/ nutrients and O2 by this
directly under sclera
retina
innermost layer of eye
contains photoreptors that transduce the light into electricla info the brain can process
light passage through eye
light rays through cornea => pupil => iris => lens => cillary muscles => photoreceptors of retina => turned into electrical signal => signal to bipolar cells => retinal ganglion cells => optic nerve =>
cornea
transparent structure that bends and focuses it
iris
muscular, pigmented
adjust amount of light entering eye by altering the diameter of pupil (more light available => greater degree of constriction)
lens
does fine focusing in eye
cillary muscles
can adjust thickness of lens, which focuses the image on retina
two types of photoreceptors
rods and cones
rods
transmission of black and white images
respond to low intensity illumination => night vision
only one pigment (rhodopsin)
cones
come in 3 varieties and manage color images
each type contains a pigment that absorbs a diff. wavelength of light => red, green, blue
rhodopsin
rods only have this one pigment (explains only respond to black and white)
color blindness
lacking of 1, 2, or 3 of sets of cones
total = commonly due to complete lack of cones
bipolar cell
relay info to retina ganglion cells
optic nerve
axons of ganglion cells bundle to form this
exits the back of the eye
blind spot
since optic nerve takes up space on back of eye => displaces photoreceptors => there this is at site of exodus
since we have two eyes => rarely problem since each eye compensate for blind spot of other
aqueous humor
eye filled w/ this fluid to simplify the transmission of light to the retina
secreted near iris at base of the eye => anterior chamber => exits => venuous blood
glaucoma
can’t adequately drain aq. humor
=>if pressure builds in anterior chamber => vitreous humor => inc. pressure on optic nerve => can permanelty damage optic nerve => blindness
Ear
transduces sound waves (mech disturbances of pressure) => electric signals => brains
houses certain nerves that help coordinate balance
Sound to Ear pathway
speaker generates long. waves => outer ear => tympanic membrane => oval window => depolarize hair cells of cochlea => electrical signal the nervous system can interpret => AP from hair cells => auditory nerve to brain
outer ear
consists of auricle and auditory canal
collects waves and channels them to tympanic membrane
tympanic membrane
beginning of middle ear, which also includes ossicles (malleus, incus, and stapes) => 3 bones transmit information
vibrates due to sound waves pushing on it => ossicles move back and forth
three ones
middle ear
includes ossicles (malleus, incus, stapes)
oval window
made up of cochlea and semicircular canals
semilunar canal (ear)
important for balance
three per ear
brain can integrate signal from each canal and maintain balance as well as interpret sudden acceleration and deceleration
endolymph
canals are filled w/ this fluid
movement through canals puts pressure on hair cells inside
two chem senses
taste and smell
they take chem moleculse from environment and turn into electrical signals
olfaction
for smell
gustation
for taste
location of taste receptors/buds
tongue, soft palate, and epiglottis
composed of approx. 40 epithelial cells
outer surface contains a taste pore , from which microvilli, or taste hairs, protrude.
receptor surface are on taste hairs
interwoven around is a network of nerve fibers that they stimulate
neurons transmit gustatory info to brainstem via three cranial nerves
4 kinds of taste sensations
sour, salty, sweet, bitter
respond preferentially
olfactory receptors
found in olfactory membrane, in upper part of nostril, about 5 cm^2
specialized neurons from which olfactory hairs, or cilia, project; cilia form dense mat in upper nasal mucosa.
strong smell hardly noticeable after a while since these are overpowered, and after constant stimulation, will desensitize to a given stimulus.
odor path in nose
odor => nasal cavity => receptors in cilia => depolarizing olfactory receptors => olfactory nerves (axons from olfactory receptors join to form this) => olfactory bulbs in base of brain
