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76 Cards in this Set

  • Front
  • Back
Define "neuron"
nervous system excitable cells that transmit electrical signals. (nerve cells)
Neurons composed of what 3 things
axon, body, dendrites
Neurons are amitotic meaning
once achieve there roles in the system they loose the ability to divide
Neurons metabolic rate is
high, they require high supply of oxygen and glucose
Neurons plasma membrane function in
Electrical signaling and
Cell-to-cell signaling during development
Axon Structure

Main structure
Slender processes of uniform diameter arising from the hillock.
Axon Structure

Long axons are called
nerve fibers.

Rare branches if present are called
Axon collaterals
Axon Structure

Define axon Hillock
Connects the cell body to the axon and site of action potential generation.
Axon Structure:

Most axons end with multiple branches to
increase influence over a postsynaptic cell
Axon Structure:

End branches are called
Axon Structure:

Axonal terminal is a
branched terminus of an axon
Axon Functions:

1. Generate and transmit
2. Secrete neurotransmitters from the
3. Movement along axons occurs in 2 ways
1. action potentials- away from cell
2. axonal terminals
3. Anterograde, Retrograde
Axon Functions:

Anterograde is
toward axonal terminal (mitochondria, cytoskeletal elements, membrane components for membrane renewal, enzymes)
Axon Functions:

Retrograde is
away from axonal terminal (usually organelles returning to cell body
Soma is the
nerve cell body

1. Is the major
2. Is the focal point for the
3. Has well developed
1. biosynthetic center.
2. outgrowth of neuronal processes
3. Nissl bodies.(rough ER- site of protein synthesis)

1. Most cell bodies are in the
2. Some are in the
1. CNS in clusters called nuclei
2. PNS in clusters called ganglia

1. Has no
2. Contains an
1. centrioles
2. axon hillock – cone-shaped area from which axons arise

1. Transmits impulse towards
2. They are receptive,input, regions of
3. Supply big surface for
4. Electrical signals conveyed as
1. soma
2. the neuron
3. receiving signals
4. graded potentials

1. junction mediates neuro transfer from one neuron to
2. presynaptic neuron
3. postsynaptic neuron
1. another neuron/effector cell
2. conducts impulses toward the synapse
3. transmits impulses away from the synapse
Synapses types:

1. Axodendritic - synapses between the axon of one
2. Axosomatic – synapses between the axon of one
3. Axoaxonic -
4. Dendrodendritic
5. Dendrosomatic
1. neuron and the dendrite of another
2. neuron and the soma of another
3. axon to axon
4. dendrite to dendrite
5. dendrites to soma
Synapses: Electrical

1. Are less common than
2. Correspond to
3. Contain protein channels that connect the cells and allow
4. Neurons that are joined together with electrical synapse are called
5. Transmission is
6. Ability to synchronize
1. chemical synapses
2. gap junctions found in other cell types
3. ions and small molecules to flow from one cell to the other
4. electrically coupled
5. fast
6. several neurons together
Synapses: Electrical
Important in CNS in

1. Arousal from
2. Mental
3. Emotions and
4. Ions and
1. sleep
2. attention
3. memory
4. water homeostasis
Synapses: Electrical

1. More abundant in ____ than _________
2. Some electrical synapse in the embryo are replaced with
embryo. adult.
2. chemical ones in the adult
Synapses: Chemical

1. Specialized for the
2. Mediated by
3. Excitatory neurotransmitters cause
4. Inhibitory neurotransmitters cause
1. release and reception of neurotransmitters (NT)
2. neurotransmitters
3. depolarization and promote action potential generation
4. hyperpolarization and suppress action potentials
Synapses: Chemical
Composed of 2 parts
1. Axonal terminal of the
2. Receptor region on the
1. presynaptic neuron, which contains synaptic vesicles (containing the NT)
2. dendrite(s) or soma of the postsynaptic neuron
Synapses: Synaptic Cleft

1. Fluid-filled space separating the
2. Prevents nerve impulses from
3. Transmission across the synaptic cleft is a
4. Transmission across the synaptic cleft ensures
1. presynaptic and postsynaptic neurons (30-50 nm wide)
2. directly passing from one neuron to the next
3. chemical event (as opposed to an electrical one)
4. unidirectional communication between neurons
Synapses: Synaptic cleft info transfer

1. Nerve impulses reach the axonal terminal of the
2. Ca2+ enters the axonal terminal from
3. The Ca2+ acts as intracellular messenger and promote
4. Neurotransmitter is released into the
5. Ca2+ is either take by the mitochondria or
6. Neurotransmitter crosses the synaptic cleft and binds
7. Postsynaptic membrane permeability
1. presynaptic neuron and open voltage-gated Ca2+ channels
2. the interstitial fluid
3. the fusion of the vesicles with the axon membrane
4. synaptic cleft via exocytosis in response to synaptotagmin
5. ejected by active Ca2+ pump (the trigger to this is unknown)
6. to receptors on the postsynaptic neuron
7. changes (channels are open – chemically-gated channels), causing an excitatory or inhibitory effect
Synapses: Info transfer Termination

1. Neurotransmitter bound to a
2. Produces a continuous
3. Blocks reception of
4. Must be removed from
1. postsynaptic neuron
2. postsynaptic effect
3. additional “messages”
4. its receptor
Synapses: Removal of Neurotransmitters occurs when

1. Are degraded by
2. Are reabsorbed by
3. Diffuse from the
1. enzymes
2. astrocytes or the presynaptic terminals
3. synaptic cleft

1. Includes the
2. Integration and
1. brain/spinal cord
2. command center

1. Includes the
2. Carries messages to and from the
3. Afferent division brings
4. Efferent division carries
5. Somatic nervous system controls
6. Autonomic nervous system controls
1. spinal and cranial nerves
2. spinal cord and brain
3. sensory information from receptors
4. motor commands to effectors
5. skeletal muscles
6. smooth muscle, cardiac muscle, glands
PNS: 2 divisons
Sensory (afferent) division

1. Sensory afferent fibers – carry
2. Visceral afferent fibers – transmit
Motor (efferent) division
3. Transmits impulses
1. impulses from skin, skeletal muscles, and joints to the brain
2. impulses from visceral organs to the brain
3. from the CNS to effector organs

1. CNS type
2. PNS type
1. oligodendrocyte
2. schwan cells
Functions of

1. CNS
2. PNS
1. Integrative and control centers
2. communication lines b/w CNS and rest of body
Sensory afferent division:

1. Structure
2. Function
1. somatic and visceral sensory nerve fibers
2. conducts impulses from receptors to the CNS
Motor efferent division

1. Structure
2. Function
1. motor nerve fibers
2. Conducts impulses from CNS to effectors (muscles and glands)
Autonamic nervous system

1. Structure
2. Function
1. visceral motor (involuntary)
2. conducts impulses from CNS to cardiac muscles, glands, smooth muscles
Somatic nervous system

1. Structure
2. Function
1. Somatic motor (voluntary)
2. conducts impulses from CNS to skeletal muscles
Autonomic divisions:

1. Sympathetic division -
2. Parasympathetic division -
1. mobilizes body systems during activity
2. conserves energy and promotes housekeeping functions durin rest
Neurons" Motor

1. Carry impulses
2. Carry activating impulses from
3. They are _____polar and cell bodies are in ______
4. Stimulate peripheral
5. Axons to
1. away from CNS
2. CNS and to the viscera, body muscles and glands;
3. multi. CNS.
4. effectors
5. PNS
Neurons: Sensory

1. Transmit impulses
2. Most are ______ polar with bodies in ______________>
3. Location – sensory receptors in the
4. Deliver information from
5. Axons to
6. They sense changes in the
1. toward CNS
2. Uni. ganglia in PNS.
3. internal organs, skin, skeletal muscles and joints.
4. exteroceptors, interoceptors, or proprioceptors
5. CNS
6. immediate environment
Neurons: Interneurons

1. shuttle signals through
2. Link other
3. They are _______ polar with bodies in _______.
4. Distribute sensory input and coordinate
1. CNS pathways
2. neurons together (i.e. sensory neuron to interneuron to motor neuron).
3. multi. CNS.
4. motor output

1. Provide a
2. Segregate and
3. Guide young neurons to
4. Promote
1. supportive scaffolding for neurons
2. insulate neurons
3. the proper connections
4. health and growth
Neuroglia Cell Functions

1. Ependyma -
2. Astrocytes -
3. Oligodendrocytes
4. Microglia
5. Schwann cells
1. produce and circulate cerebrospinal fluid
2. structural support and blood/brain barrier
3. myelinate CNS axons
4. Phagocytize and remove debris
5. myelinate PNS axons
Myelin Cells

1. Oligodendrocytes -
2. Schwann Cells
1. branched cells that wrap CNS nerve fibers
2. surround fibers of the PNS

1. myeling is a
2. Layers of plasma membrane
3. Schwann cells myelinate
4. Schwanna cells Also surround and organize
5. Oligodendrocytes myelinate/connect
6. Outer layer contains
1. not a secretion or a product
2. coiled around an axon
3. single PNS axons
4. unmyelinated PNS axons
5. multiple CNS axons = “White Matter”
6. cytoplasm of myelinating cell = “Neurilemma”

1. Thick layer of lipid
2. Charged particles don’t
3. No need for
4. Reduces resistance to
5. Speeds up
1. outside axon
2. penetrate
3. channels, pumps, receptors
4. flow of current
5. transmission of impulses

1. White matter
2. Gray matter
1. dense collections of myelinated fibers
2. mostly soma and unmyelinated fibers
Neuoron "Resting Potential"

1. Generate by diff concentrations of
2. Ionic differences are the consequence of
3. The cell cytoplasm contains a lower concentration of
4. The negative interior of the cell is due to a
5. The reason there is no equilibrium in the ion concentration is because of
1. Na+, K+, Cl, and protein anions (A)
2. Differential permeability of the neurilemma to Na+ and K+
Operation of the sodium-potassium pump
3. Na+ and higher concentration of K+
4. greater diffusion (along concentration gradient) of K+ out of the cell than of Na+ diffusion into the cell
5. ATP-driven Na+ - K+ pump that ejects 3 Na+ out of the cell and 2 K+ into the cell

1. threshold -
2. Established by the total amount of
3. Weak (subthreshold) stimuli are
4. Strong (threshold) stimuli are
5. The stronger the stimuli the
1. membrane is depolarized by 15 to 20 mV
2. current flowing through the membrane (of sodium and potassium)
3. relayed into action potentials
4. relayed into action potentials
5. quicker the membrane arrives to threshold
Neuoron "Resting Potential"

1. The potential difference (–70 mV) across the membrane of a resting neuron – membrane is
2. RMP exists only across the
1. polarized
2. membrane – the bulk solutions in the cell are neutral

1. define
1. action potentials either happen completely, or not at all
Nerve impulse

1. Nerve impulse -
1. series of action potentials occurring down the length of an axon.
Absolute Refractory Period

1. Time from the opening of the
2. When the sodium channels are open, the neuron can not
3. Prevents the neuron from
4. Ensures that each action potential is
5. Enforces
1. Na+ activation gates until the closing of inactivation gates
2. respond to another stimulus, no matter how strong it is
3. generating an action potential
4. separate
5. one-way transmission of nerve impulses
Relative Refractory Period

1. During this period the axon threshold is
2. The interval following the
3. Sodium gates are
4. Potassium gates are
5. _______ is occuring
1. elevated
2. absolute refractory period
3. closed
4. open
5. Repolarization
Saltatory Conduction

1. Current passes through a
2. Voltage-gated Na+ channels are
3. Action potentials are
4. Much faster than conduction along
1. myelinated axon only at the nodes of Ranvier
2. concentrated at these nodes
3. triggered only at the nodes and jump from one node to the next
4. unmyelinated axons

1. Examples
2. Excitatory neurotransmitters cause
3. Inhibitory neurotransmitters cause
1. Acetylcholine (ACh)
Biogenic amines Amino acids Peptides Novel messengers: ATP and dissolved gases NO and CO
2. depolarization and promote action potential generation
3. hyperpolarization and suppress action potentials
Neurotransmitters Criteria

1. When a neuron is stimulated (depolarized
2. When a chemical is released, it must act on a
3. After a chemical is released, it must be
4. If the chemical is applied on the post-synaptic membrane, it
1. a neuron must release the chemical
2. post-synaptic receptor and cause a biological effect.
3. inactivated
4. should have the same effect as when it is released by a neuron.
Neurotransmitters: Acetylcholine

1. First neurotransmitter identified, and
2. Released by: All neurons that stimulate
3. Released by: Some neurons in the
4. Synthesized and enclosed in
5. Acetylcholine is synthesized enzyme
6. The effect of ACh is
1. best understood
2. skeletal muscle (neuromuscular junction)
3. autonomic nervous system and in the CNS
4. synaptic vesicles
5. choline acetyltransferase from the compounds choline and acetyle CoA
6. short-lived
Neurotransmitters: Biogenic Amines

1. A biogenic substance is a substance produced by
2. Catecholamines –
3. Indolamines –
4. Broadly distributed in
5. Play roles in
1. life processess. It may be either constituents, or secretions, of plants or animals
2. dopamine, norepinephrine (NE), and epinephrine
3. serotonin and histamine
4. the brain
5. emotional behaviors and our biological clock
Neurotransmitters: Amino Acids

1. Include:
2. Found only in
1. GABA – Gamma ()-aminobutyric acid Glycine
Aspartate Glutamate
2. the CNS
Neurotransmitters: Peptides

1. Include:
2. Act as natural
3. Bind to the same
4. Gut-brain peptides –
1. Substance P – mediator of pain signals Beta endorphin, dynorphin, and enkephalins
2. opiates; reduce pain perception
3. receptors as opiates and morphine
4. somatostatin, and cholecystokinin
Neurotransmitter Receptor Mechanisms

1. Direct-
2. Indirect-
1. neurotransmitters that open ion channels
2. neurotransmitters that act through second messengers
Neurotransmitter: Direct

1. Promote
2. Examples:
1. rapid responses
2. ACh and amino acids
Neurotransmitter: Indirect

1. Promote
2. Examples:
1. long-lasting effects
2. biogenic amines, peptides, and dissolved gases

1. EPSP are
2. Use a single type of chemically-gated ion channels that allows
3. Electrochemical gradient for sodium is much
4. Sodium influx is greater than
5. That will result in increased
6. If enough NT are bound to the postsynaptic receptors,
7. Postsynaptic membranes do not generate action potentials but its role is to
8. EPSP often travel
1. graded potentials that can initiate an action potential in an axon
2. Na+ and K+ flow in opposite directions at the same time
3. steeper than that for potassium
4. potassium efflux
5. sodium concentration inside and depolarization
6. depolarization can reach 0 mV which is beyond axon threshold (-50mV)
7. EPSP that will trigger AP distally at the axon hillock.
8. all the way to the axon hillock (although decline with distance)
Inhibitory Synapses and IPSPs

1. Are
2. Causes the membrane to become more
3. Leaves the charge on the inner surface
4. Reduces the postsynaptic neuron’s ability to
1. Neurotransmitter binding to a receptor at inhibitory synapses:
2. permeable to potassium and chloride ions (causing hyperpolarization)
3. negative
4. produce an action potential

1. A single EPSP can not
2. Most important determinants of neural activity are
3. EPSP and IPSP add together to produce
4. Two forms of Summation
1. induce an action potential
2. EPSP / IPSP interactions
3. permeability changes and affect formation of action potentials
4. Temporal and Spatial
Summation: Temporal

1. =
2. presynaptic neurons transmit
3. first impulse produce
4. second arrives
1. Frequency based
2. impulses in rapid-fire order
3. small epsp
4. before the first disappears
SUmmation: spatial

1. happen at sites of
2. postsynaptic neuron is stimulated by a
3. It can be from the
1. multiple synapses
2. large number of terminals at the same time
3. same neuron or from different neurons (more common)
Neuronal Pools

1. Neurons rarely exhibit
2. Multiple neurons synapsing with
3. functional groups that4.
1. one-on-one interactions
2. multiple neurons is more common
3. Integrate incoming information, Forward the processed information
Neuronal Pool: Simple
consist of
Postsynaptic fibers and

1. One incoming (Input) fiber –
2. Discharge zone
3. Facilitated zone
1. presynaptic fiber branches as it enters the pool and synapse with several neiurons in the pool
2. neurons most closely associated with the incoming fiber – most likely to generate impulses
3. – neurons farther away from incoming fiber
Neural Proccessing: Serial

1. Input travels along
2. Works in an
3. Example:
1. one pathway to a specific destination
2. all-or-none manner
3. spinal reflexes
Neural Processing: Parallel

1. Input travels along
2. Pathways are integrated in
3. One stimulus promotes
4. Example
1. several pathways
2. different CNS systems
3. numerous responses
4. a smell may remind one of the odor and associated experiences