The Nervous System Flashcards
Neurons
Specialized cells capable of transmitting electrical impulses and translating them into chemical signals
Anatomy of Neuron: Cell Body/Soma
where nucleus is located
location of endoplasmic reticulum and ribosomes
Anatomy of Neuron: Dendrites
appendages coming off of the soma that receive signals
Anatomy of Neuron: Axon Hillock
info from dendrites passes through cell body and is integrated here
Action Potentials
transmission of electrical impulses down the axon
Signals arriving from the dendrites can be ____ or _____ , the axon hillock sums these signals and if it reaches _____ , to initiate an action potential.
excitatory
inhibitory
threshold
Anatomy of Neuron: Axon
long appendage that terminates in close proximity to target (muscle, gland or neuron)
Anatomy of Neuron: Myelin Sheath
insulation across nerve to prevent loss/crossing of signals and increases speed of conduction
Oligodendrocytes
CNS cells that produce myelin
Schwann Cells
PNS cells that produce myelin
Anatomy of Neuron: Nodes of Ranvier
breaks in myelin sheath on axon for rapid signal conduction
Anatomy of Neuron: Nerve Terminal/Synaptic Bouton
enlarged and flattened terminal area to maximize neurotransmission and ensure proper release of neurotransmitters
Anatomy of Neuron: Synaptic Cleft
space between neurons where axons release neurotransmitters to dendrites of next neuron
Anatomy of Neuron: Synapse
Nerve Terminal, Synaptic Cleft, Postsynaptic Membrane
Nerve
multiple neurons may be bundled together in the peripheral nervous system
can be sensory, motor or mixed
Cell bodies of neurons of the same type are clustered together into _____
ganglia
In the CNS, axons may be bundled together to form _____ , which cary only one type of information.
tracts
The cell bodies of neurons in the same tract are grouped into _____
nuclei
Glial Cells/Neuroglia
other cells that support neurons
Astrocytes
form blood/brain barrier, nourish neurons by controlling solute transport between nervous tissue and blood
Ependymal Cell
line ventricles of brain and produce cerebrospinal fluid to support brain as a shock absorber
Microglia
phagocytic cells that ingest and breakdown waste products in CNS
Resting Membrane Potential
all neurons have this, the electrical potential difference between the inside and outside of the neuron
usually -70mV
inside of neuron is negative to the outside
Na+ /K+ ATPase
channel that maintains the membrane potential of the neuron
moves 3Na+ out of cell for every 2K+ into the cell
Inside the neuron ____ is high and ____ is low. Outside the neuron, ____ is high and ___ is low.
[K+} , [Na+]
[Na+], [K+]
Negative resting potential is generated by both ________ within the cell and relatively greater permeability of K+ than Na+ ions into the cell allowing for passive transport out the cell.
negative proteins
ATP in transport required because_____, this is an example of ____. Each time the pump is used, it results in the inside of the cell becoming more _____
Na+ and K+ are moved against their gradients,
primary active transport
more negative
Depolarization
excitatory inputs to neuron raising the membrane potential, making it more likely to release an action potential
Hyperpolarization
inhibitory inputs to the neuron lowering the membrane potential to make neurons less likely to fire action potential
Summation
additive effect of multiple excitatory and inhibitory signals
Temporal Summation
multiple signals integrated during a short period of time
Spatial Summation
additive effects are based on the number and location of the incoming signals
aka large number of inhibitory at action hillock effects more than small number of excitatory firing at dendrites
1) Action Potential:When neuron is brought to threshold….
voltage gated sodium channels pen up leading to depolarization and let Na+ enter cell due to a strong electrochemical gradient (negative and low Na+ inside)
2) Action Potential: When Vm reaches 35mV….
sodium channels are inactivated and must be brought to resting potential to deinactivate
voltage gated potassium channels open to let K+ leave the cell causing repolarization
Three states of Sodium Channels
Closed (before cell reaches threshold and after inactivation is reversed)
Open ( from threshhold to 35mV)
Inactive (35mV to resting potential
3) Action Potential: K+ ions leaving below threshold
hyperpolarization occurs as voltage is lower than threshold making neuron refractory(resistant) to further action potentials
Absolute Refractory Period
no amount of stimulation can cause another action potential
Relative Refractory Period
there must be greater than normal stimulation to cause action potential because the membrane is starting from a potential that is more negative than resting value
4) Action Potential: Na+/K+ ATPase
after hyperpolarization, the Na+/K+ ATPase restores the resting potential and the gradients of each ion
Impulse propagation
action potential traveling down the axon and initiating neurotransmitter release
as Na+ rushes into one segment of axon, it will depolarize subsequent segments of the axon to open Na+ channels and allow each segment to propagate action potentials to the terminal
After actin potential is fired from one segment of axon, the segment is momentarily refractory causing ONE WAY FLOW of information
The speed at which action potentials move is dependent on ____ and _____ of an axon.
Increased _____ of axon leads to higher resistance and slower conduction.
Greater ______ allows for faster propagation due to decreased resistance
length , cross sectional area
length
cross sectional area
Saltatory conduction
signal hoping from one node to another as membrane is only permeable at the nodes of Ranvier
All action potentials within the same type of neuron have the same ______ during depolarization. Increased intensity of a stimulus causes an _____ of firing not _____ of the action potential.
potential difference
increased frequency
increased potential difference
Presynaptic Neuron
neuron preceding the synaptic cleft
Postsynaptic Neuron
neuron after synaptic cleft
If a neuron signals to a gland or muscle rather than a neuron, the postsynaptic cell is termed an ______
effector
When action potential reaches the nerve terminal, voltage gated _____ open allowing ____ to flow into the cell. This triggers fusion of _______ with the cell membrane at the synapse causing ___ of the neurotransmitter into synaptic cleft.
Once released into synapse, neurotransmitters ____ across the cleft and bind to ____ on post synaptic membrane.
calcium channels
calcium
membrane bound vesicles
exocytosis
diffuse
receptors
Neurotransmitter receptors can be….
ligand gated ion channels or g protien coupled receptors
Ligand Gated Ion Channel
postsynaptic cell will either be depolarized or hyperpolarized
G Protein Coupled Receptors
cause changes in levels of cAMP or influx of calcium
Breaking Down Neurotransmitter: Enzymatic
break down of ACh by acetylcholinesterase AChE
Breaking Down Neurotransmitter: Reuptake carriers
neurotransmitters are brought back to the presynaptic carriers
ex 5-HT (serotonin), DA (dopamine) and NE (norepinephrine)
Breaking Down Neurotransmitter: Diffuse out of Synaptic Cleft
nitric oxide, a gas signaling molecule
Sensory/Afferent Neurons
transmit sensory information from receptors to the spinal cord/brain
Motor/Efferent Neurons
transmit motor information from the brain and spinal cord to muscles/glands
Interneurons
found in between other neurons and are the most occurring
located predominantly in the brain and spinal cord, reflexive behavior
Processing of stimuli and response generation may happen at the _____ or ______/______
spinal cord
brainstem/cerebral cortex
Reflexes only require processing at the level of the _____
spinal cord
Supraspinal circuits
input from brain/brainstem
Central Nervous System (CNS)
brain and spinal cord
Brain consists of white and ____ matter.
White matter consists of _______
Grey matter consists of ______
grey
myelin sheath encased axons
cell bodies and dendrites
Spinal cord can be divided into 4 sections:
cervical, thoracic, lumbar and sacral
Vertebral Column
protects spinal cord and transmits nerves within space between adjacent vertebrae
Spinal cord white matter is on the _____ while the grey matter is _____.
Axons of the spinal cord are _____
outside
deep within
within the spinal cord
Pathway of Sensory Neurons
1) Sensory neuron brings info from periphery and enter the dorsal side of spinal cord
2) Cell bodies of the sensory neurons are in the dorsal root ganglia
3) motor neurons exit the spinal cord ventrally (closest to front of body)
Peripheral Nervous System
made up of nerve tissue and fibers outside the brain and spinal cord including spinal nerves and 10 of the cranial nerves
connects rest of the body t the CNS
The two pairs of cranial nerves that are part of the CNS are:
olfactory and optic nerves
Somatic Nervous System
sensory and motor neurons throughout skin, joints muscles
Sensory: through afferent fibers
Motor: travel along efferent fibers
Autonomic Nervous System (ANS)
regulates heartbeat, respiration, digestion and glandular secretion (the involuntary muscles with organs/glands) as well as temperature
automatic functions, not requiring conciousness
One primary difference between the somatic and autonomic nervous system is that the peripheral component of ANS contains ____ neurons.
A motor neuron in the somatic nervous system goes directly from the spinal cord to the muscle without _____
In the ANS, two neurons work in series to transmit messages from the spinal cord.
The _______ is in the CNS and its axon travels to a ganglion in the PNS. Here it synapses with the cell body of the _______ which affects the target tissue.
two
synapsing
preganglionic neuron
postganglionic neuron
The ANS is divided into 2 subsections. The sympathetic nervous system and the parasympathetic nervous system are _____
antagonistic
Parasympathetic Nervous System
concerves energy
resting, sleeping, reduce heart rate, manage digestion
main neruotransmitter is actylcholine released by both the pre/postganglionic neurons
Vagus nerve(X) is responsible for parasympathetic innervation of thoracic and abdominal cavity
Sympathetic Nervous System
activated by stress/ fight or flight
increase heart rate, blood to muscles, decrease digestion, relax bronchi, dialate eyes for light intake, release epinephrine
Pre releases acetylcholine
Post releases norepinephrine
Reflex Arcs
neural circuits that control reflexive behavior
Monosynaptic Reflex Arc
single synapse between sensory neuron that receives the stimulus and the motor neuron that responds to it.
Knee Jerk Reflex
Monosynaptic Reflex Arc
When stretched…
1) info travels sensory (afferent, presynaptic) neuron to spinal cord to interface with the motor (efferent, postsynaptic) neuron to contract quadricep
Polysynaptic Reflex Arc
Atleast one interneuron between the sensory and motor neuron
ex: withdrawal reflex
