Chapter 1 - Quiz 1 Flashcards
1.1: Neurons and glia
What are the two kind of cells that make up the nervous system?
-neurons and glia
1.1: Neurons and glia
What are neurons/what do they do?
-cells that receive information and transmit it to other cells
1.1 - 1a Neurons and glia: Santiago Ramon y Cajal, a Pioneer of Neurosci
Who are the pioneers/main founders of neuroscience?
-Charles Sherrington & Santiago Ramon y Cajal
-Santiago demonstrated (via stained slides) that neurons are seperate
1.1 -1b Neurons and Glia: The structures of an animal cell
What is the surface of a cell called? Define it. (2)
-membrane
-separates inside of the cell from outside
1.1 -1b Neurons and Glia: The structures of an animal cell
What does the nucleus contain? What cells do not have a nucleus? (2)
-chromosomes
-mammalian red blood cells
1.1 -1b Neurons and Glia: The structures of an animal cell
Define mitochondrion. What does it do? (1)
-performs metabolic activities, providing the energy that the cell uses for all activites
-mitochondria have genes seperate from those in the nucleus of a cell and mitochondria differ from one another genetically
1.1 -1b Neurons and Glia: The structures of an animal cell
What do ribosomes do?
-synthesizes new protein molecules
-some ribosomes float freely in the cell, others are attached to the endoplasmic reticulum
1.1 -1b Neurons and Glia: The structures of an animal cell
What is the endoplasmic reticulum?
-network of thin tubes that transport newly synthesized proteins
1.1 -1c Neurons and Glia: The structures of a neuron
What do all neurons have? What do most have? (2)
-soma (cell body)
-most have dendrites, axon, and presynaptic terminals
1.1 -1c Neurons and Glia: The structures of a neuron
Where is a motor neuron and where does it recieve and send an excitation? (3)
-soma in the spinal cord
-receives excitation through its dendrites
-conducts impulses along its axon to a muscle
1.1 -1c Neurons and Glia: The structures of a neuron
Where is a sensory neuron and what type of stimulation does it respond to? Where is the soma? (3)
-neurons in skin, tongue, ear, smell
-specialized to be highly sensitive to a particular type of stimulation on one end
-soma is in the middle of two axons
1.1 -1c Neurons and Glia: The structures of a neuron
What are dendrites?
-branching fibers that get narrower near their ends
-dendrites surface is lined with specialized synaptic receptors at which the dendrite recieves information from other neurons. The greater the surface area of a dendrite, the more information it can receive.
1.1 -1c Neurons and Glia: The structures of a neuron
What do many dendrites contain? Define them. (2)
-dendritic spines
-short outgrowths that increase the surface area available for synapses
1.1 -1c Neurons and Glia: The structures of a neuron
What does a cell body contain?
-nucleus, ribosomes and mitochondria
-most of a neuron’s metabolic work occurs here
-in many neurons, the cell body is like the dendrites, covered with synapses on its surface
1.1 -1c Neurons and Glia: The structures of a neuron
What is the axon? Where does it convey impulses to? (2)
-the thin fiber of constant diameter
-to other neurons, an organ, or a muscle
-axons can be more than a meter in length
-neurons can only have one axon
-the largest animals will have the largest axons
1.1 -1c: Neurons and Glia: The structures of a neuron
What are many vertebrate axons covered with?
-myelin sheath with nodes of Ranvier
1.1 -1c: Neurons and Glia: The structures of a neuron
What is the presynaptic terminal (end bulb)?
-it is at the end of each branch of axon and is the swelling
1.1 -1c: Neurons and Glia: The structures of a neuron
What is an afferent axon?
-brings info towards something
-a for admit
1.1 -1c: Neurons and Glia: The structures of a neuron
What is an efferent axon?
-carries info away from something
-e for exit
1.1 -1c: Neurons and Glia: The structures of a neuron
What is an interneuron cell/intrinsic neuron?
-a cell whose dendrites and axons are entirely contained within a single structure
1.1 -1e: Neurons and Glia: Glia
Where do glia outnumber neurons and vice versa? (3)
-glia outnumber them in the cerebral cortex
-neurons outnumber glia in several other areas of the brain, especially the cerebellum
-in total, the numbers are about equal
1.1 -1e: Neurons and Glia: Glia
What are the different types of glia cells?
-astrocytes
-oligodendrocytes
-microglia
-Schwann cells
-radial glia
1.1 -1e: Neurons and Glia: Glia
What are astrocytes? Where do they go? What do they allow to happen? (3)
-star shaped glia that synchronize the activity of the axons
-wrap around the synapses of functionally related axons
-helps synchronize neurons, enabling their axons to send messages in waves
-important for generating rhythms like breathing
1.1 -1e: Neurons and Glia: Glia
What is the tripartite synapse?
-tip of axon releases chemicals that cause the neighboring astrocytes to release chemicals of their own, magnifying the next message to the next neuron
-possible contributor to learning or memory
1.1 -1e: Neurons and Glia: Glia
Define microglia? What are two other functions they perform?
-cells that remove waste material and other microorganisms from the nervous system
-they proliferate after brain damage, removing dead or damaged neurons
-they contribute to learning by removing the weakest synapse
1.1 -1e: Neurons and Glia: Glia
Which cells build the myelin sheaths that surround and insulate certain vertebrae axons? And supply an axon with nutrients necessary for proper functioning?
-oligodendrocytes in the brain and spinal cord
-Schwann cells in the periphery of the body
1.1 -1e: Neurons and Glia: Glia
What do radial glia do?
-guide the migration of neurons and their axons and dendrites during embryonic development
-once embryological development finishes, most radial glia differentiate into neurons and sometimes astrocytes and oligodendrocytes
1.1 - 2 The Blood Brain Barrier
What is the blood-brain barrier?
-the mechanism that excludes most chemicals from the vertebrate brain
1.1 - 2a Blood Brain Barrier: Why we need a blood-brain barrier
Why do we need a blood-brain barrier? What is the blood-brain barrier? (2)
-to minimize the risk or irreparable brain damage
-the brain’s blood vessel are lined with tightly packed endothelial cells that keep out most viruses, bacteria and harmful chemicals
1.1 - 2a Blood Brain Barrier: Why we need a blood-brain barrier
What are examples of a virus that does cross the blood-brain barrier?
-rabies, herpes, chicken pox
1.1 - 2b Blood Brain Barrier: How the blood-brain barrier works
What is the con of the blood-brain behavior? (2)
-it keeps out both good and bad chemicals
-including keeping out fuels and amino acids, which the brain needs special mechanisms to help cross
1.1 - 2b Blood Brain Barrier: How the blood-brain barrier works
Which molecules cross the blood-brain barrier easily? (2)
-small uncharged molecules (oxygen, carbon dioxide)
-molecules that dissolve in the fats of the membrane (vit A and D, psychiatric drugs)
-the speed a drug takes effect depends largely on how readily it dissolves in fats and therefore crosses the blood-brain barrier
1.1 - 2b Blood Brain Barrier: How the blood-brain barrier works
How does water cross the blood-brain barrier?
-through special protein channels in the wall of the endothelial cells
-considered passive transport
1.1 - 2b Blood Brain Barrier: How the blood-brain barrier works
What is active transport? Which chemicals have to be actively transported into the brain? (2)
-a protein-mediated process that expends energy to pump chemicals from the blood into the brain
-glucose, amino acids, purines, choline, a few vitamins and iron
-glucose is the brains main fuel
-insulin and probably certain other hormones also cross the blood-brain barrier
1.1 - 3 Nourishment of Vertebrate Neurons
Why do neurons need a steady supply of oxygen?
-because metabolizing glucose requires oxygen and vertebrate neurons depend almost entirely on glucose
1.1 - 3 Nourishment of Vertebrate Neurons
Why do neurons depend so much on glucose?
-because its the only nutrient that crosses the blood-brain barrier in large amounts
1.1 - 3 Nourishment of Vertebrate Neurons
What does vitamin B1 (thiamine) sufficiency result in?
-to use glucose, the body needs B1, so a lack of this leads to death of neurons and a condition called Korsakoff’s syndrome
1.2 The Nerve Impulse
How do two flashes on the retina in different spots avoid being received at different times?
-axons from more distant parts of your retina transmit impulses slightly fasters than those closer to the brain
1.2 - 1 The resting potential of the neuron
What is the membrane of a neuron composed of?
-two layers of phospholipid molecules with cylindrical protein molecules through which chemicals can pass through
1.2 - 1 The resting potential of the neuron
What is an electrical gradient or polarization?
-a difference in electrical charge between the inside and outside of the cell
1.2 - 1 The resting potential of the neuron
Define resting potential
-condition of a neuron’s membrane when it has not been stimulated or inhibited
1.2 - 1 The resting potential of the neuron
How do you measure the resting potential of a neuron?
-inserting a very thin microelectrode into the cell body and connecting this to a voltmeter
1.2 - 1a Forces Acting on Sodium and Potassium Ions
How is a neuron able to stay at its resting potential? At rest, what ions pass through the selective membrane? (2)
-the selective permeability ensure chemicals stay where they are supposed to be
-at rest, almost no sodium ions cross the membrane except by the sodium-potassium pump but some potassium ions slowly leak out
-the leakage of the potassium ions increases the electrical gradient
1.2 - 1a Forces Acting on Sodium and Potassium Ions
What is a sodium-potassium pump? How many sodium ions leave the cell per potassium ions entering from the sodium-potassium pump? (3)
-mechanism that actively transports sodium ions out of the cell and potassium ions in
-3 sodium ions out of the cell
-2 potassium ions in the cell
-as a result of the sodium-potassium pump, sodium ions are more than 10 times more concentrated otuside the membrane than inside, and potassium ions are more concetrated inside than outside
1.2 - 1a Forces Acting on Sodium and Potassium Ions
What is the concentration gradient?
-the difference in distribution of ions across the membrane
-sodium is more concentrated outside than inside, so just by the laws or probability, sodium is more likely to enter the cell than leave it
1.2 - 1a Forces Acting on Sodium and Potassium Ions
Why at rest does no sodium enter into the cell?
-because the sodium channels are closed when the membrane is at rest
-if they weren’t closed, sodium would enter rapidly because of the electrical and concentraion gradient
1.2 - 1a Forces Acting on Sodium and Potassium Ions
What two processes work to move sodium ions into the cell? (2)
-the electrical gradient (the negative charge inside attracts the positive sodium)
-the concentration gradient (sodium is more concentrated outside than inside, so just because of probability sodium is more likely to enter the cell than to leave it)
1.2 - 1a Forces Acting on Sodium and Potassium Ions
How is potassium subject to competing forces?
-the electrical gradient tends to pull it in
-the concentration gradient tends to drive it out
1.2 - 1a Forces Acting on Sodium and Potassium Ions
Does the inside of a neuron have negatively charged ions too? How about outside the cell, which ions are those? (2)
-yes, they sustain the membranes polarization
-outside the cell there are chloride ions
1.2 - 1b Why a resting potential?
Why is a resting potential necessary or useful?
-it prepares the neurons to respond rapidly
-because the membrane did its work in advance by maintaining the concentration gradient for sidum, the cell is prepared to respond vigorously to a stimulus
1.2 - 2 The Action Potential
Define action potential. Define hyperpolarization. Define depolarize. (3)
Action potential: all or none messages sent by axons
Hyperpolarization: increased polarization across a membrane
Depolarize: to make the polarization go towards zero, make it less negative
Define threshold. What happens when the potential rechaes the threshold? Can the intensity of a stimulus cause the neuron to produce a bigger or smaller action potential? (3)
-minimum amount of membrane depolarization necessary to trigger an action potential
-the membrane opens its sodium channels and lets sodium ions into the cell
-no, the action potential will always be the same intensity and velocity if it passes the threshold
-it is all or none, and any stimlation beyond the threshold, regardless of how far beyond, produces the same response
1.2 - 2a The Action Potential: The all or none law
Define the all-or-none law
-the amplitude and velocity of an action potential is independent of the intensity of the stimulus that initiated it, provided that the stimulus reaches the threshold
-thicker axons convey action potentials at greater velocities and can convey more action potentials per second
1.2 - 2a The Action Potential: The all or none law
How does an action potential signal the difference between a weak and strong stimulus?
-it changes the timing and can use almost a morse code rhythm
1.2 - 2b The Action Potential: The molecular basis of the action potenti
The axon channels regulating sodium and potassium are what? Define this word. (2)
-voltage gated channels
-membrane channel whose permeability to the ion depends on the voltage difference across the membrane
1.2 - 2b The Action Potential: The molecular basis of the action potenti
State the steps of an action potential and what happens to the ions during each step from resting potential to the end. (6)
Resting potential:sodium channels are fully closed, potassium channels are almost closed, allowing a little flow of potassium
Depolarization: Both sodium and potassium channels open, but potassium doesn’t really move yet. Sodium ions are driven into the cell.
Threshold: Once depolarization reaches the threshold, the sodium channels completely open and sodium enters rapidly.
Peak of action potential: Sodium gates close. Potassium is driven out of the cell know.
Hyperpolarization: The potassium leaving eventually creates a hyperpolarization of the membrane.
After action potential: The membrane has returned to its resting potential but there are more sodium ions inside the cell and slightly fewer potassium ions than before. The sodium-potassium pump restores the original distribution.
1.2 - 2b The Action Potential: The molecular basis of the action potenti
How do local anesthetics work? (2)
-they attach to the sodium channels of the membrane and prevent sodium ions from entering
-when a dentist administers Novocain before drilling into a tooth, your receptors are screaming pain but the axons cannot transmit the message to your brain so you don’t feel it
1.2 - 3 Propogation of the action potential
What does the propagation of the action potential describe? How does it work? (2)
-the transmission of an action potential down an axon
-as an action potential occurs at one point on the axon, enough sodium enters to depolarize the next point to its threshold, producing an action potential at that point. In this manner the action potential flows along the axon remaining at equal strength throughout. Behind each area of sodium entry, potassium ions exit, restoring the resting potential
1.2 - 3 Propogation of the action potential
What is back-propogating?
-when the action potential starts, it back-propagates into the cell body and dendrites
-an action potential always starts in an axon and propagates without loss from start to finish
1.2 - 3 Propogation of the action potential
Why is back-propagation important?
-when an action potential back-propagates into a dendrite the dendrite becomes more susceptible to the structural changes responsible for learning
1.2 - 4 The Myelin Sheath and Saltatory Conduction
What is a myelin sheath and what purpose does it serve? What analogy describes it? (3)
-an insulating material composed of fats and proteins
-it increases the speed of an action potential
-analogy of throwing a ball over a long distance
1.2 - 4 The Myelin Sheath and Saltatory Conduction
What are myelinated axons?
-the axons covered by a sheath with small breaks called nodes of Ranvier
-node of ranvier is like the exposed axon.
1.2 -3 The Myelin Sheath and Saltatory Conduction
Why does saltatory conduction happen? What is saltatory conduction? What are the pros of saltatory conduction? (4)
-a myelinated axon with an action potential can’t propagate along the myelinated regions.
-Instead, the action potential “jumps” from one node of Ranvier to the next.
-This jumping process is much faster than if the action potential had to propagate along the entire length of the axon.
-as well, it expends less energy
1.2 - 4a The myelin sheath and saltatory conduction: the refractory peri
Define a refactory period. When does it happen? (2)
-time when the cell resists the production of further action potentials
-After an action potential, neuron enters refractory period.
-Voltage-gated sodium channels inactive, cannot open.
-Prevents immediate firing of another action potential.
-Ensures one-directional signal transmission.
-Then what prevents an action potential near the center of an axon from reinvading the areas that it has just passed? The answer is that the areas it just passed are still in their refractory period.
1.2 - 4a The myelin sheath and saltatory conduction: the refractory peri
What can a refractory period be broken down into?
-the absolute refractory period (stage 1)
-the relative refractory period
1.2 - 4a The myelin sheath and saltatory conduction: the refractory peri
What is the absolute refractory period?
-this means the membrane cannot produce another action potential, regardless of the stimulation
-about 1 ms long
1.2 - 4a The myelin sheath and saltatory conduction: the refractory peri
What is the relative refractory period?
-a stronger than usual stimulus is needed to initiate an action potential
-about 2-4 ms
1.2 - 4a The myelin sheath and saltatory conduction: the refractory peri
What two facts does the refractory period depend on?
-to stay in a refractory period
-the sodium channels are closed
-potassium is flowing out of the cell at a faster than usual rate
1.2 -5 Local Neurons
How do small neurons exchange information without an axon and what are they subsequently called? What do they not follow subsequently because they do not have an axon? (3)
-since they have no axons, they can only exchange info with their neighbors
-they are called local neurons
-they do not follow the all-or-none law
-local neurons are neurons without an axon
1.2 -5 Local Neurons
What is a graded potential?
-a membrane potential that varies in magnitude in proportion to the intensity of the stimulus
-local neurons have this
