Neurons - Hu - Exam 1 Flashcards
1) __ ___ __: This layer forms the blood-retinal barrier between the choroid and the retina. Nutrients, oxygen, and other metabolites must pass through the RPE to reach the photoreceptors. As a result, the retina must remain attached to the RPE to remain healthy. Retinal detachment can lead to death of photoreceptors and loss of vision in the affected area. Pigment (melanin granules) in the RPE absorbs stray light and helps to sharpen images.
2) __ ___ ___ ___: The photosensitive cells of the retina are rods and cones. Rods are specialized for dim-light vision, while cones are specialized for vision in bright light. The two cell types are distinguished by the organization of their photosensitive organelle, or outer segment, which is a stack of photosensitive membranes. Rods have a long rod-shaped outer segment, while cones have a shorter cone-shaped outer segment.
3) ___ ____ ____: The synthetic machinery of the photoreceptors is situated in their inner segments, lying just below the outer segments, and connected to them by a ciliary connecting piece.
4) ___ ___ ___: This layer consists of the cell bodies of the photoreceptor cells.
5) __ __ __ is a layer of synapses between photoreceptors and intraretinal relay neurons, the horizontal cells and the bipolar cells. Horizontal cells ramify in the OPL and provide communication between adjacent portions of the retina. Bipolar cells provide communication between the outer and inner retina.
6) ___ ___ __ contains the nuclei of horizontal, bipolar and amacrine cells, all of which are neurons. In addition, the nuclei of Muller cells are located here.
7) __ ___ ___ consists of synapses of bipolar cells on amacrine and ganglion cells. Amacrine cells provide lateral and feedback communication within the retina. Ganglion cells are the output neurons of the retina.
8) ___ ___ ___ contains the cell bodies of the ganglion cells.
9) __ ___ ___ contains the axons of the ganglion cells, which come together at the optic nerve head to exit the eye as the optic nerve (CN II).
1) Retinal pigment epithelium: The RPE forms the blood-retinal barrier between the choroid and the retina. Nutrients, oxygen, and other metabolites must pass through the RPE to reach the photoreceptors. As a result, the retina must remain attached to the RPE to remain healthy. Retinal detachment can lead to death of photoreceptors and loss of vision in the affected area. Pigment (melanin granules) in the RPE absorbs stray light and helps to sharpen images.
2) Photoreceptor outer segment layer: The photosensitive cells of the retina are rods and cones. Rods are specialized for dim-light vision, while cones are specialized for vision in bright light. The two cell types are distinguished by the organization of their photosensitive organelle, or outer segment, which is a stack of photosensitive membranes. Rods have a long rod-shaped outer segment, while cones have a shorter cone-shaped outer segment.
3) Photoreceptor inner segment layer: The synthetic machinery of the photoreceptors is situated in their inner segments, lying just below the outer segments, and connected to them by a ciliary connecting piece.
4) The outer nuclear layer. The ONL consists of the cell bodies of the photoreceptor cells.
5) The outer plexiform layer. The OPL is a layer of synapses between photoreceptors and intraretinal relay neurons, the horizontal cells and the bipolar cells. Horizontal cells ramify in the OPL and provide communication between adjacent portions of the retina. Bipolar cells provide communication between the outer and inner retina.
6) The inner nuclear layer. The INL contains the nuclei of horizontal, bipolar and amacrine cells, all of which are neurons. In addition, the nuclei of Muller cells are located here.
7) The inner plexiform layer. The IPL consists of synapses of bipolar cells on amacrine and ganglion cells. Amacrine cells provide lateral and feedback communication within the retina. Ganglion cells are the output neurons of the retina.
8) Ganglion cell layer. The GCL contains the cell bodies of the ganglion cells.
9) Nerve fiber layer. The NFL contains the axons of the ganglion cells, which come together at the optic nerve head to exit the eye as the optic nerve (CN II).
There is regional variation in the distribution of cells within the retina. As a result there is regional variation in the quality of vision. Photoreceptors and ganglion cells are least dense in the equatorial regions of the retina (peripheral vision) and most dense at the posterior pole (central vision). The central few degrees of vision is served by a special region known as the fovea (diameter 1.5 mm).
The fovea itself has a number of specializations that permit vision of the greatest acuity.
- the highest density of photoreceptors and ganglion cells
- ___ only (no ___) in the foveola (central 350 micrometers).
- foveal pit - ganglion cells and other fibers deviated to the side to provide ____ light path to foveal cones.
- no ____ supply on inner retina so that blood vessels do not obstruct light path.
There is regional variation in the distribution of cells within the retina. As a result there is regional variation in the quality of vision. Photoreceptors and ganglion cells are least dense in the equatorial regions of the retina (peripheral vision) and most dense at the posterior pole (central vision). The central few degrees of vision is served by a special region known as the fovea (diameter 1.5 mm).
The fovea itself has a number of specializations that permit vision of the greatest acuity.
- the highest density of photoreceptors and ganglion cells
- Cones only (no rods) in the foveola (central 350 micrometers).
- Foveal pit - ganglion cells and other fibers deviated to the side to provide unobstructed light path to foveal cones.
- No vascular supply on inner retina so that blood vessels do not obstruct light path.
Synapse:
•Area where a neuron (cell) communicates with another neuron (or a cell)
There are two kinds of synapses:
___synapse and ___ synapse
Synapse:
•Area where a neuron (cell) communicates with another neuron (or a cell)
There are two kinds of synapses:
chemical synapse and electrical synapse
Electrical Synapse:
- Less common than __ synapses
- Neurons are ___ coupled
oJoined by __ ___ that connect cytoplasm of adjacent neurons
oCommunication is very rapid and may be unidirectional or bidirectional
oHelps ____ the activities of large groups of interconnected neurons
oThey are found in unimotor ___ and ____muscle cells
If you think about the heart, what two groups of heart cells would use this? __ and ___ cells.
Electrical Synapse:
- Less common than chemical synapses
- Neurons are electrically coupled
oJoined by gap junctions that connect cytoplasm of adjacent neurons
oCommunication is very rapid and may be unidirectional or bidirectional
oHelps coordinate the activities of large groups of interconnected neurons
oThey are found in unimotor smooth and cardiac muscle cells
If you think about the heart, what two groups of heart cells would use this? conducting and contractile cells
Chemical Synapse:
•_____ cell: Neurotransmitter production and release
oNeuron that sends message
•_____ cell: Neurotransmitter receptor
oCell that receives message
•The synaptic cleft is also important because in the cleft, you can have enzymes that can degrade the neurotransmitter (NT is like the house guest…they need to leave at some point).
oThe small gap that separates the presynaptic membrane and the postsynaptic membrane
- __directional
- Towards a specific goal
- Could co-exist with electrical synapses
Chemical Synapse:
•Pre-synaptic cell: Neurotransmitter production and release
oNeuron that sends message
•Post synaptic cell: Neurotransmitter receptor
oCell that receives message
•The synaptic cleft is also important because in the cleft, you can have enzymes that can degrade the neurotransmitter (NT is like the house guest…they need to leave at some point).
oThe small gap that separates the presynaptic membrane and the postsynaptic membrane
- Unidirectional
- Towards a specific goal
- Could co-exist with electrical synapses
Pre-synaptic terminal:
First, you have the arrival of the __ ___.
Next, __-___ calcium channel opens. The influx of calcium is very important because it binds to the ____-____complex (Soluble N-ethylmaleimide-sensitive factor activating protein receptor), which are located at the ___ “releasing sites.” Upon binding, they initiate a cascade of events.
•Vesicles then fuse with the presynaptic terminal membrane to release ___ into synaptic cleft
In order for an AP to happen, you must have ___ influx.
What is required for you to have calcium influx? You must have set up a ___!
Pre-synaptic terminal:
First, you have the arrival of the action potential.
Next, voltage-gated calcium channels open. The influx of calcium is very important because it binds to the SNARE-protein complex (Soluble N-ethylmaleimide-sensitive factor activating protein receptor), which is located at the presynaptic “releasing sites.” Upon binding, they initiate a cascade of events.
•Vesicles then fuse with the presynaptic terminal membrane to release neurotransmitters into synaptic cleft.
In order for an AP to happen, you must have calcium influx. What is required for you to have calcium influx? You must have a gradient!
•Can you recall one condition learned in CAP course last year that could potentially affect AP?
•Can you recall one condition learned in CAP course last year that could potentially affect AP?
Hypoparathyroidism decreases existing blood calcium concentration.
Fluid, electrolytes, acid-base balance
is essential in neural activities.
___ receptors have a channel
___ receptors are transmembrane molecules that can “open” or “close” a channel that would allow smaller particles to travel in and out of the cell. As the name implies, IONotropic receptors allow different kinds of ions to travel in and out of the cell.
Ionotropic receptors have a “channel” that opens or closes
Metabotropic receptors are transmembrane molecules that can “open” or “close” a channel that would allow smaller particles to travel in and out of the cell. As the name implies, IONotropic receptors allow different kinds of ions to travel in and out of the cell.
Excitatory Synapses
- Neurotransmitter binding opens ____ gated channels
- Cation channels are lined with __ charges, thus attract positively charged __+ , and sometimes _+ and __++ to pass. The local net graded potential towards depolarization is called __ ___ ___ ___ (__).
These could trigger __ __ if it reaches the threshold.
Excitatory Synapses
- Neurotransmitter binding opens chemically gated channels
- Cation channels are lined with negative charges, thus attract positively charged Na+ , and sometimes K+ and Ca++ to pass. The local net graded potential towards depolarization is called excitatory postsynaptic potential (EPSP)
•EPSPs could trigger action potential (AP) if it reaches the threshold.
Inhibitory Synapses:
•Neurotransmitter binding to receptors that are anion channels allows Cl- to influx, results in _____, inhibitory postsynaptic potential (IPSP)
oThis makes the postsynaptic membrane more permeable to ___
•Cl– is a main anion in ___
oThis reduces the___ neuron’s ability to produce an action potential
•Moves neuron farther away from ___ (makes it more negative)
Inhibitory Synapses:
•Neurotransmitter binding to receptors that are anion channels allows Cl- to influx, results in hyperpolarization, inhibitory postsynaptic potential (IPSP)
oMakes postsynaptic membrane more permeable to Cl–
•Cl– is a main anion in extracellular fluid
oReduces postsynaptic neuron’s ability to produce an action potential
•Moves neuron farther away from threshold (makes it more negative)
Integration and Modification of Synaptic Events:
•Summation by the __ neuron
oA ____ EPSP cannot induce an AP, but a ___of EPSPs can summate to influence postsynaptic neuron
•IPSPs can also summate
oMost neurons receive both excitatory and inhibitory inputs from thousands of other neurons
•Only if ___ predominate and bring to threshold will an action potential be generated
oTwo types of summations: __ and __
_____ summation
oOne or more presynaptic neurons transmit impulses in rapid-fire order
•First impulse produces EPSP, and before it can dissipate another EPSP is triggered, adding on top of first impulse
____ summation
oPostsynaptic neuron is stimulated by large number of terminals simultaneously
•Many receptors are activated, each producing EPSPs, which can then add together
•Summation by the postsynaptic neuron
oA single EPSP cannot induce an AP, but a group EPSPs can summate to influence postsynaptic neuron
•IPSPs can also summate
oMost neurons receive both excitatory and inhibitory inputs from thousands of other neurons
•Only if EPSPs predominate and bring to threshold will an action potential be generated
oTwo types of summations: temporal and spatial
•Temporal summation
oOne or more presynaptic neurons transmit impulses in rapid-fire order
•First impulse produces EPSP, and before it can dissipate another EPSP is triggered, adding on top of first impulse
•Spatial summation
oPostsynaptic neuron is stimulated by large number of terminals simultaneously
•Many receptors are activated, each producing EPSPs, which can then add together
Fatigue of Synaptic Transmission:
- An important characteristic of synaptic function
- Development of fatigue is a protective mechanism against excess ___ activity
- Mechanism is due to ___ or partial __ of the stored neurotransmitter substance in the presynaptic terminals.
Fatigue of Synaptic Transmission:
- An important characteristic of synaptic function
- Development of fatigue is a protective mechanism against excess neuronal activity
- Mechanism is due to exhaustion or partial exhaustion of the stored neurotransmitter substance in the presynaptic terminals.
General Classes of Receptors:
_______ ion channel receptors (ionotropic)
oExample: __ ___
oMechanism: Open an __ channel
____ (metabotropic)
oExample: Adrenergic and ACh muscarinic
oMechanism: Activate second messengers, e.g. ___
General Classes of Receptors:
•Oligomeric ion channel receptors (ionotropic)
oExample: ACh nicotinic
oMechanism: Open an ion channel
G protein-coupled receptors (metabotropic)
oExample: Adrenergic and ACh muscarinic
oMechanism: Activate second messengers, e.g. cyclic AMP
NO is a ___acting ____ neurotransmitter
- Simple diffusion from pre- to post-synaptic terminal
- Vascular __ relaxation
- A principal neurotransmitter in the ___ nervous system in GI: Coordination of peristalsis and sphincteric action.
- Physiological amounts of this gas are ____, whereas higher concentrations are clearly ___
NO is a short acting inhibitory neurotransmitter
- Simple diffusion from pre- to post-synaptic terminal
- Vascular SMC relaxation
- A principal neurotransmitter in the enteric nervous system in GI: Coordination of peristalsis and sphincteric action.
- Physiological amounts of this gas are neuroprotective, whereas higher concentrations are clearly neurotoxic
->
In the heart, what type of cells would have mostly chemical synapse?
SA nodes and AV nodes on conducting cells have more chemical synapse.
G Protein- Coupled Receptor:
- Responses are indirect, complex, slow, and often prolonged.
- Involves ____ protein complexes
- Cause widespread metabolic changes
- Examples:
oMuscarinic ACh receptors
oReceptors that bind biogenic amines
oReceptors that bind neuropeptides
Choline esters - ACh
Biogenic Amines - SHEND
Amino Acids - Three G’s
Neuropeptides - ACT
ACh:
- First identified and best understood
- Released at neuromuscular junctions
oAlso used by many ANS neurons and some CNS neurons
- Synthesized from ___ acid and ___ by enzyme __ ___
- Degraded by enzyme ___
- Reuptake by a ___ transporter. What is this mechanism?
- First identified and best understood
- Released at neuromuscular junctions
oAlso used by many ANS neurons and some CNS neurons
- Synthesized from acetic acid and choline by enzyme choline acetyltransferase
- Degraded by enzyme acetylcholinesterase (AChE)
- Reuptake by a Na+-choline transporter. What is this mechanism?
Dopamine, Epinephrine, and Norepinephrine can be degraded by:
MAO:
- Monoamine oxidase
- Located in ___ nerve terminals
COMT:
- Catechol-O-methyl-transferase
- Widely distributed in __, but not in nerve end
All three NT’s can be degraded either in the presynaptic nerve terminals or systemically and eliminated via kidneys
MAO:
- Monoamine oxidase
- Located in presynaptic nerve terminals
COMT:
- Catechol-O-methyl-transferase
- Widely distributed in tissues, but not in nerve end
All three can be degraded either in the presynaptic nerve terminals or systemically and eliminated via kidneys.
Serotonin:
- Produced in the serotonergic neurons in the ___ and in the GI tract.
- Returned intact to the nerve terminal
- Degraded in ___ terminal
- Precursor to ___
Serotonin:
- Produced in the serotonergic neurons in the brain and in the ___ tract.
- Returned intact to the nerve terminal
- Degraded in presynaptic terminal
- Precursor to melatonin
