nervous system Flashcards
Hydras
nerve net- neurons in contact with one another
echinoderms
have nerves- bundles of neurons
planarians
ladder-like nervous systems
cephalization- concentration of ganglia and sensory receptors in the head
both have central and peripheral nervous systems
nervous system of insects
brain, ventral nerve cord, ganglia(cluster of neurons)
nervous system of mollusks
complex brains- millions of neurons organized into specialized lobes
true nervous system
nervous system of vertebrates
CNS- brain and spinal cord
PNS- cranial nerves and spinal nerves
what is the human nervous system divided into
central nervous system(CNS) –>the integration center
the peripheral nervous system(PNS)–.gathers info from sensors and conduct decisions to effectors
what are the three specific functions of the nervous system
receiving sensory input
performing integration
generating motor output
nervous tissue of neurons
cell body, dendrites and axons
cell body
(soma)
contains nucleus
dendrites
receive signals from sensory receptors
axon
conducts nerve impulses and directs information
myelin sheath
protects the neuron and speeds up transmissions
long axon
nerve fiber
types of neurons
sensory
interneurons
motor neurons
sensory neurons
accept impulses from sensory receptors and transmit them to the CNS
interneurons
convey nerve impulses between various parts of the CNS
motor neurons
accept nerve impulses from the CNS and transmit them to muscles or glands
what are the four main types of neurons according to number and placement of axons and dendrites
unipolar, multipolar, bipolar and pseudounipolar
unipolar neuron
insects; singular axon function
multipolar neuron
CNS(mostly) one long process
bipolar neuron
retina
same length
pseudounipolar neuron
sensory neurons
does not go through the cell body
what does the axon connect to and what is the whole thing called
dendrite; synapse
glial cells
support, protect, nourish neurons
outnumber neurons 10 to 1 in the brain
fulfill many vital function
what causes brain tumors
mutation in glia
list glial cells in CNS
oligodendrocytes, astrocytes, ependymal cells, microglia
oligodendrocytes
form myelin sheath around axons
astrocytes
provide nutrients and structural support
ependymal cells
produce cerebrospinal fluid that cushions the neurons
microglia
scavenge pathogens and dead cells
list glial cells in PNS
Schwann cells and satellite cells
Schwann cells
form the myelin sheath
Satellite cells
provide nutrients and structural support to neurons
membrane potential
a voltage difference between the inside and the outside
changes in response to neurotransmitters from other neurons and environmental stimuli
why is the inside of the membrane negative
potassium ion movement out
large negatively charged proteins inside
70millivolt more negative inside that outside
action potential
a stimulus depolarizes the axon to the threshold
Na+ channels in the axon hillock open, Na+ enters, Axon depolarizes to +30mV,
action potentials are considered and all or nothing even
once the threshold is reached, the neuron always completely depolarizes, and K+ exits during repolarization and hyperpolarization
action potential propagation
in response to a signal, the soma end of the axon becomes depolarized. the depolarization spreads down the axon. Meanwhile, the first part of the membrane repolarizes. because Na+ channels are inactivated and additional K+ channels have opened, the membrane cannot depolarize again. the action potential continues to travel down the axon
electrical synapse
depolarization moves directly to postsynaptic neuron through gap junction
no synaptic delay = faster
bi-directional
coordinate groups of neurons
rare
- good for embryonic nervous system
adult- thalamus
slow-wave sleep
chemical synapse
depolarization causes synaptic vesicles containing neurotransmitter molecules to be released into the synaptic cleft.
neurotransmitter binding to postsynaptic receptors open ion channels
ion movement creates a postsynaptic potential
what are the two types of postsynaptic potentials
Excitatory (EPSP)
inhibitory(IPSP
EPSP
sum together to bring an axon to threshold
IPSP
drive membrane potential away from threshold
spinal cord and brain are wrapped in three protective membranes called what
meninges
what are spaces between the meninges filled with
cerebrospinal fluid
fluid is continuous with that of central canal of spinal cord and the what of the brain
ventricles
what is the largest portion of the brain in humans
cerebrum
cerebrum
communicates with, and coordinates that activities of, the other parts of the brain
longitudinal fissure
divides into left and right cerebral hemispheres
corpus callosum
connects right and left hemisphere of the brain
sulci(sulcus) and Gyri(gyrus)
increase surface area
cerebral cortex
thin highly convoluted outer layer of gray matter
surface area increases throughout evolutionary tree
contains motor areas and sensory areas as well as association areas
diencephalon
region encircling the third ventricle
hypothalamus
forms the floor of the third ventricle, controls the endocrine system via pituitary
thermostat
thalamus
two masses of gray matter located in the sides and roof of the third ventricle
gateway to and from the cortex
brain area that relays sensory information to the cortex
pineal gland
secretes melatonin
cerebellum
receives sensory input from the eyes, ears, joints, and muscles
sends motor impulses out the brain stem to the skeletal muscles
balance and coordination
parts of the brain stem
midbrain, pons, medulla oblongata
midbrain
acts as a relay station for tracts passing between cerebrum and spinal cord/cerebellum
pons
helps regulate breathing and head movements
medulla oblongata
has reflx centers for vomiting, coughing, sneezing, hiccupping, and swallowing
somatic system
cranial nerves and spinal nerves
gather info from sensors and conduct decisions to effectors
controls the skeletal muscles
conscious activity
autonomic system
controls the smooth muscles, cardiac muscles, and glands
unconscious control
- divided into two divisions
- sympathetic division and parasympathetic division
cranial nerves
12 pairs
sensory
motor
both
spinal nerves
31 pairs
enter/exit between vertebrae
both sensory and motor
function of the spinal cord
center for many reflex actions
means of communication between the brain and spinal nerves
gray matter
cell bodies and short unmyelinated fibers
white matter
myelinated long fibers of interneurons running in tracts
autonomic system
regulates activity of cardiac and smooth muscle and glands.
function automatically and usually in an involuntary manner
innervate all internal organs
utilize two neurons and one ganglion for each impulse
sympathetic division
flight or flight responses
accelerates heartbeat and dilates bronchi
parasympathetic division
promotes all internal responses associated with a relaxed state
promotes digestion and retards heartbeat
action potential definition
self-propagating momentary change in the electrical potential of a neuron or muscle membrane
astrocyte
glial cell in the central nervous system that provides nutrients, extracellular buffering, and structural support for neurons; also makes up the blood-brain barrier
autonomic nervous system
part of the peripheral nervous system that controls bodily functions
axon hillock
electrically sensitive structure on the cell body of a neuron that integrates signal from multiple neuronal connections
aaxon terminal
structure on the end of an axon that can form a synapse with another neuron
brainstem
a portion of the brain that connects with the spinal cord; controls basic nervous system functions like breathing, heart rate and swallowing
cerebral cortex
outermost sheet of brain tissue; involved in many higher-order functions
cerebrospinal fluid
clear liquid that surrounds the brain and spinal cord and fills the ventricles and central canal; acts as a shock absorber and circulates material throughout the brain and spinal cord
corpus callosum
thick fiber bundle that connects the cerebral hemispheres
cranial nerve
sensory and or motor nerve that emanates from the brain
dendrite
structure that extends away from the cell body to receive messages from other neurons
depolarization
change in the membrane potential to a less negative value
dura mater
tough outermost layer that covers the central nervous system
ependymal
cell that lines fluid-filled ventricles of the brain and the central canal of the spinal cord; involved in production of cerebrospinal fluid
frontal lobe
part of the cerebral cortex that contains the motor cortex and areas involved in planning, attention, and language
gyrus
ridged protusions in the cortex
hippocampus
brain structure in the temporal love involved in processing memories
hyperpolization
change in the membrane potential to a more negative value
hypothalamus
brain structure that controls hormone release and body homeostasis
membrane potential
difference in electrical potential between the inside and outside of a cell
meninge
membrane that covers and protect the central nervous system
modes of ranvier
gaps in the myelin sheath where the signal is recharged
occipital lobe
part of the cerebral cortex that contains visual cortex nd processes visual stimuli
parietal lobe
part of the cerebral cortex involved in processing touch and the sense of the body in space
radial gila
gila that serve as scaffolds for developing neurons as they migrate to their final destination
saltatory conduction
“jumping” of an action potential along an axon from one node of ranvier to tehe next
satellite gila
glial cell that provides nutrients and structural support for neurons in the peripheral nervous system
somatosensation
sense of touch
sulcus
indents in the spinal cord
summation
process of multiple presynaptic inputs creating EPSPs around the ame time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential
synapse
junction between two neurons where neuronal signals are communicated
synaptic cleft
space between the presynaptic and postsynaptic membranes
synaptic vesicle
spherical structure that contains a neurotransmitter
temporal lobe
part of the cerebral cortex that processes auditory input; parts of the temporal lobe are involved in speech, memory, and emotion processing
ventricle
cavity within brian that contains cerebrospinal fluid
