PNB 2XB3 Midterm 1 Review Flashcards
What is the width of the synaptic cleft?
20-40nm
What is the diameter of the cell body?
10μm
What is the CNS?
The CNS is the central nervous system. All parts of the nervous system within bone: spinal cord, brainstem, thalamus, cortex, etc.
What is the PNS?
The PNS is the peripheral nervous system. All parts not within bone: peripheral nerves.
What is CSF?
CFS is the cerebrospinal fluid. The aqueous saline solution that surround the brain and neurons.
What is AHP?
AHP is after hyperpolarization. AHP is the undershoot that occurs after the rising phase and falling phase in an action potential.
What is an EPSP?
An EPSP is an excitatory postsynaptic potential. An EPSP is the moving of the post-synaptic cell toward threshold.
What is an IPSP?
An IPSP is an inhibitory postsynaptic potential. An IPSP moves the post-synaptic cell away from threshold.
What is an efferent neuron?
An efferent nerve carries impulses away from the cortex.
What is an afferent neuron?
An afferent nerve carries impulses toward the cortex.
How can the driving force equation be used to determine the direction of an ion’s flow across the membrane?
Vm-Ex tells you how far away the neuron is from the equilibrium potential for that ion, this determines how muuch flows
What is the definition of negative current?
Negative current describes the movement of positive ions into the cell, or the movement of negative ions out of the cell.
In both circumstances, the interior of the cell becomes more positive.
What is the definition of positive current?
Positive current is the movement of negative ions into the cell, or the movement of positive ions out of the cell.
In both circumstances, the cell interior becomes more negative.
What causes the absolute refractory period?
The absolute refractory period is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.
In neurons, it is caused by the closure and inactivation of the Na+ channels that originally opened to depolarize the membrane. These channels remain inactivated until the membrane repolarizes, after which they regain their ability to open in response to stimulus.
What causes the AHP?
During AHP the cell becomes more negative due to the opening of voltage gated potassium channels. K+ rushes out of the cell.
Why do we say an action potential is all-or-nothing?
An action potential is all-or-nothing because in order for an action potential to fire, the cell must reach threshold (-55mV)
Why do we say an action potential is regenerative?
The potential change induced by the opening of voltage gated channels decrements as you record further and further away from the Na+ channel. However, this graded depolarization triggers the opening of neighboring Na+ voltage-dependent channels, which results in more Na+ entering the cell, and, in effect, regenerating the action potential.
What is saltatory conduction?
Jumping movement of the action potential from node to node down an axon
Why do we say an action potential is unidirectional?
Under normal conditions, action potentials only move in one direction along the axon. The refractory wake prevents the action potential from moving backwards.
How do local anaesthetic work?
Local anaesthetics are injected topically (where you want them to act)
Example: Lidocaine is an open voltage gated potassium channel blocker. It prevents Na+ from entering the cell, thus action potentials cannot occur. Creates a numbing effect.
How does myelin work to speed up an action potential?
Myelin reduces membrane capacitance because it creates greater separation between positive and negative ions interior and exterior to the cell.
Myelin increases membrane resistance because it covers leaky channels along the membrane.
Does myelin increase or decrease membrane capacitance?
Myelin decreases membrane capacitance
Does myelin increase or decrease membrane resistance?
Myelin increases membrane resistance
Oligodendrocyte vs. Schwann cell
Oligodendrocytes are the glial cells of the CNS and Schwann cells are the glial cells of the PNS.
A single oligodendrocyte can wrap around several axons.
Schwann cells only wrap around a single axon.
What is the difference between multiple sclerosis and Guillain Barre syndrome?
MS and Guillain Barre are both autoimmune disorders of demyelination.
MS causes the demyelination of myelin cells in the CNS and is a progressive neurological disorder.
Guillain Barre causes demyelination of myelin cells in the PNS and is not progressive.
Describe the events that trigger the release of neurotransmitter
When the action potential reaches the axon terminal, it becomes depolarized. This results in the opening of voltage-gated Ca++ channels along the axon terminal membrane. Ca++ moves into the cell along its concentration gradient and entering calcium binds to a calcium sensor on the vesicle called synaptotagmin. SNARE complexes then form to pull membranes together. Ca++-bound synaptotagmin catalyzes membrane fusion. releasing neurotransmitter into the cleft.
What famous experiment did Otto Loewi perform, and what did it show?
Otto Loewi came up with an experiment to prove chemical transmission in a heartbeat.
He showed that there was a gap between neurons.
What experimental evidence supports the conclusion that synaptic transmission is quantal in nature?
Depolarization occurs in integer multiples of a certain quantity. This demonstrates that chemicals are not randomly spilling, they are released in specific integer quantities.
What causes the quantal nature of synaptic transmission?
Not every action potential will release the same number of synaptic vesicles
What is the value of the resting potential of a typical neuron?
-65mV
What is the value of the action potential threshold?
-55mV
Which of these ions has a higher inside concentration than outside concentration: Na+, K+, Ca++, Cl-
Na+: Higher concentration outside
K+: Higher concentration inside
Ca++: Higher concentration outside
Cl-: Higher concentration outside
Describe the sensory deficits that occur in Brown Sequard syndrome. Why do those specific deficits occur?
Brown-Sequard causes damage to half of the spinal cord, either the left-half or the right-half. All the axons coming from below the body are cut, theferfore you will have ipsilateral loss of touch and contralateral loss of pain and temperature.
What is referred pain, and how does it happen?
When pain in an internal organ is felt on the skin, not on the organ itself. This happens because the internal organs share the same pathway as the skin because they synapse onto the same neuron, so the brain has no way of distinguishing between the two.
What are the differences between a Nissl stain and a Golgi stain?
Nissl stain dye the endoplasmic retriculum in RNA to stain neuron cell bodies. Nissl stains show a whole bunch of neuron cell bodies within a section of the brain.
Golgi stains dye fewer cells, but show the detailed morphology of cells.
What are the differences between extracellular recording and intracellular recording?
Extracellular:
Electrode not actually inside the neuron
Intracellular:
Electrode inside the neuron
Why is the rod system more sensitive than the cone system?
- Rods are longer than cones and contain more photpigment
- Many rods converge onto the same bipolar cell
- Rods have greater amplification, closing more Na+ channels in response to the same amount of light absorbed
Why does the cone system have better spatial acuity than the rod system?
- Cones are densely packed at the fovea, which lacks overlying axons and blood vessels, reducing light scattering
- The cone system has much less convergence
What is an intra-cortical neuron?
A nerve that carries impulses within the cortex.
What is a coronal section?
Divided the brain into ventral and dorsal (belly and back)
What is a sagittal section?
Divides the brain into left and right parts (vertical cut)
What is a horizontal section?
A horizontal cut through the centre of the brain
What is ipsilateral?
Same side
What is contralateral?
Opposite side
What does it mean to decussate?
Cross midline
Rostral
Toward nose
Upward in the spinal cord or toward front in the brain
Caudal
Toward tail
Downward in spinal cord or toward back of brain
Ventral
Toward belly
Front of spinal cord or toward bottom of brain
Dorsal
Toward back
Back of spinal cord to toward top of brain
What is medial?
Near midline
What is lateral?
Far from midline
What is TTX?
TTX is tetrodotoxin. TTX is highly concentrated in the ovaries and liver of puffer fish. It binds with voltage-gated sodium channels, causing paralysis.
What is GABA?
GABA is the most common inhibitory neurotransmitter in the cerebral cortex. When GABA binds to a receptor on the post-synaptic cell, GABA receptors open and Cl- flows moves down its concentration gradient into the cell.
What is glutamate?
The most common excitatory neurotransmitter. If glutamate binds with a receptor on the post-synaptic cell, glutamate receptors open. Na+ enters the cell, K+ leaves cell, down their concentration gradients.
Why is the resting potential negative?
The K+ concentration is greater inside than outside the neuron, due to the action of the sodium/potassium pump.
Furthermore, at rest the neuron is primarily permeable to K+ because the membrane contains K+ leak ion channels.
Therefore, K+ diffuses out of the cell, making the inside negative.
What is mean by the term “electrochemical” equilibrium?
The potential at which the net flow of an ion would be zero is called electrochemical equilibrium for that ion.
What are the four lobes of the brain?
Frontal
Temporal
Parietal
Cerebellum
What is an important function of the frontal lobe?
Voluntary movement, expressive language, and managing higher level executive functions (such as logic and reasoning)
What is an important function of the temporal lobe?
Processing affect/emotions, language, memory, audition, and certain aspects of visual perception
What is an important function of the parietal lobe?
Processing somatosensory information (including touch, pain, temperature)
What is an important function of the cerebellum?
Coordination of voluntary movements
Why do chile peppers taste hot?
Chile peppers have a chemical in them called capsaicin. Capsaicin is a lipophilic molecule (can cross through the lipid bilayer membrane). There is an intracellular binding site for capsaicin on heat-gated ion channels. When capsaicin binds to this site, the heat-gated ion channel open, causing action potentials. These action potentials are interpreted as heat.
Why do mints taste cool?
Mint contains menthol which has a binding site on cold-gated ion channels. When menthol binds, cold-gated ion channels open, allowing sodium and potassium to flow in, depolarizing the cell. This results in action potentials that are interpreted as cold.
What is the function of the 2nd and 3rd cortical layers?
Sends axons to and recieves axons from other cortical areas (including the opposite hemisphere)
What is the function of the 4th cortical layer?
Recieves axons from the thalamus
What is the function of the 5th cortical layer?
Sends axons to the brainstem and spinal cord (caudally)
What is the function of the 6th cortical layer?
Sends axons to the thalamus
Why are intracellular recordings difficult?
It is difficult to get an electrode inside a neuron in vivo because every time the heart beats, the brain bounces up and down, when you inhale, your brain sinks, in systole the brain inflates when the heart pumps, in diastole the brain deflates slighlty.
What is VPL?
Ventral posterior nucleus. The somato-sensory relay nucleus in the thalamus
What is cGMP?
Cyclic guanosine monophosphate. An intracellular ligand
Aβ: axon diameter, conduction velocity
6-12μm, 35-75m/s
Aδ: axon diameter, conduction velocity
1-5μm, 5-30m/s
C: axon diameter, conduction velocity
0.2-1.5μm, 0.5-2m/s
What are the 4 neuroscience rules?
Symmetry
Localization of function
Contralaterality
Topography
Symmetry
Both sides of the brain are the same
Localization of function
Brain is separate into different lobes that are resposible for specific functions
Contralaterality
Left lobe activates rights side of body and vice versa
Topography
Each part of the body maps onto a specfic part of the brain
What are gyri?
Humps
What are sulci?
Grooves
What is the central sulcus?
Separates the pariteal lobe from the temporal lobe
What is the sylvian fissure?
Separates the temporal lobe from the frontal and parietal lobes
Describe the sequence of ion channel events that account for the rising and falling phase of the action potential
