biopsychology study guide

In the experiments conducted by Hodgkin and Huxley, the early current disappeared if the membrane was clamped at _______ mV.

+52

Describe the mechanisms of action of Digoxin in cardiac failure

-Digoxin blocks the sodium potassium pump -the cell is more positive and there is an increased amount of action potentials generated. -This increases the chance that the cell will fire. Digoxin is used to increase the excitability of the heart muscles.

List the steps involved in neurotransmission

1) Action potential arrives at presynaptic terminal 2) Voltage-gated calcium channels in terminal membrane open and calcium ions enter 3) Calcium ions cause synaptic vesicles filled with neurotransmitter fuse with presynaptic membrane and rupture, releasing transmitter into synaptic cleft Ca caused vesicles to fuse with presynaptic membrane and rupture, releasing neurotransmitters into the synapse 4) Transmitters bind to postsynaptic receptors, causing opening of ion channels and leading to an EPSP or IPSP 5) EPSPs/IPSPs spread toward postsynaptic axon hillock -- if the threshold is reached, action potential will occur 6) Synaptic transmission rapidly stopped -- action is brief and accurately reflects state of presynaptic cell; transmitters may activate presynaptic receptors, decreasing transmitter release

Which observation was not observed in Hodgkin and colleagues' voltage-clamp study of squid action potentials?

A sustained outward current as a result of hyperpolarization

The action potential consists of three phases

A. an initial rapid depolarization that peaks; B. a rapid hyperpolarization that moves several mV beyond resting potential; C. a gradual return to resting potential.

Absolute Refractory Period

Absolute Refractory Period

Work done by _______ elucidated changes in membrane permeability that underlie an action potential

Alan Hodgkin and Andrew Huxley

Cognitive neuroscience is concerned with

All of the above

Which statement best describes the action potential?

An action potential occurs when the cell's membrane potential reaches threshold.

Compare/Contrast between electrical and chemical synapses

Electrical: Cytoplasmic continuity Gap-junction channels Ion current Absent delay Bidirectional Chemical: voltage gate No cytoplasmic continuity Presynaptic vesicles and active zones Chemical transmitter Significant delay Unidirectional

Which technique first produced unequivocal support for the neuron doctrine of the nervous system (as opposed to the reticular theory)?

Electron microscopy of nervous tissue

List the steps involved in the endocytic and exocytotic process

Exocytotic: - Restraint and mobilization (vesicles are held until they are required) -Targeting to docking sites (directed into particular place) -Docking and priming (involves calcium, binding) -Fusion and exocytosis (fusions vesicle docks and exocytosis) Endocytotic -Disassembly of SNARE complex (the proteins involved in tying vesicle to membrane, need to remove those to have vesicles move) -Coating (with protein clathrin which encapsulates it) -Pinching off of vesicle (enzyme GTPase) -Endocytosis (removal of clathrin coat) Recycling

Which statement best describes the electrical properties of nerve cells?

In comparison to copper wires, they are relatively poor conductors of electricity.

Which statement about the ionic permeability of cell membranes is true?

In resting nerve cells, the membrane is quite permeable to potassium.

Which statement about a center-surround receptive field is false?

It is found only in primary sensory cortex.

Which statement about multiple sclerosis (MS) is false?

It was recently proven that all cases of MS are due to persistent infection by a tropical parasite.

how would the membrane potential change if all K+ ions were replaced by Ca2+ ions?

It would be reduced by half.

Compare and contrast resting channels and the Na+/K+ pump and their role in determining the resting membrane potential of the cell.

Resting channels: stay open all the time and only allow specific ions to cross the membrane Not affected by extrinsic factors (e.g. Voltage across membranes) Important in maintaining Resting membrane potential Na+/K+ Pump: ATPase pumps acquire energy from ATP hydrolysis Create & maintain ionic gradients Form complex with ions that are being translocated Slower process & involve consumption of energy The resting membrane potential of a squid giant axon is determined by the K+ concentration gradient across the membrane. Changes in sodium will impact the amplitude of action potential.

Which state of the plasma membrane does not occur during an action potential?

Resting phase

Which motor response would you expect?

Right leg remains motionless

During which phase of an action potential does membrane permeability to Na+ exceed membrane permeability to K+?

Rising and overshoot phases

Which cell produces myelin in the nerves of the peripheral nervous system?

Schwann cell

Which statement about ionic distributions in nerve cells is true?

Sodium is higher outside cells than inside cells.

Compare and Contrast Sympathetic and Parasympathetic

Sympathetic nervous system: -has axons that innervate the sympathetic ganglia, small clusters of neurons outside the CNS -prepares the body for action / the "fight-or-flight" response -Preganglionic fibers use Ach -Primary neurotransmitter/s in postganglionic terminals: epinephrine, norepinephrine -Short preganglionic axons and long postganglionic fibers Parasympathetic Nervous System: -Parasympathetic neurons run from the CNS to the parasympathetic ganglia -helps the body to relax, recuperate, and prepare for future action; buildup metabolic reserves -Preganglionic fibers use ACh -Postganglionic terminals use ACh. -Long preganglionic axons and short postganglionic fibers

What would happen if the membrane became permeable to the Y+ ions?

The Y+ ions would move into the top chamber, down their concentration gradient.

Which statement describes one of the features of Hodgkin and Huxley's mathematical model?

The action potential can be reconstructed based entirely on the time course and amplitudes of the ionic conductances.

Which statement correctly differentiates between the passive and active current in a myelinated axon?

The active current flows only in the nodes of Ranvier, unlike the passive current.

A neuron has received enough stimulation to fire an action potential; it also has been treated with TEA, a K+ channel blocker. Which outcome is possible?

The cell will initially depolarize, but repolarization will take much longer because it relies only on ion pumps.

Which statement on the rising or overshoot phase of the action potential is true?

The degree of depolarization is limited in part by the inactivation time course for the sodium current.

Which of the following is the key event at the membrane potential of 65 mV?

The early and late currents flow outward

What change will occur in the recording?

The frequency of action potentials will increase.

Which of the following is the key event at a membrane potential of -26 mV?

The late outward current increases in magnitude

How will expression of the androgen receptor protein be altered in the transgenic mouse?

The mouse will not express androgen receptor in muscle fibers.

What is responsible for the repolarization?

The quick closing of NA+ channels and opening of K+ channels

Which statement regarding refractory periods is true?

The refractory period ends when the sodium channels are no longer inactivated.

Describe what contributes to the afterhyperpolarization that contributes to the refractory period.

The slow closing of the K+ channels

Which process(es) underlie(s) the refractory period?

The slow time course of turning off K+ conductance activation and the persistence of Na+ conductance inactivation

Which statement best describes most neurons?

They are polarized.

Which statement about active ion transporters is true?

They move certain ions against the concentration gradient

Which statement about astrocytes is true?

They play a role in the formation of the blood-brain barrier.

How would K+ ions flow across the membrane?

They would flow from the outside compartment to the inside compartment.

Therapeutic hypothermia is a proven part of cardio-cerebral resuscitation after cardiac arrest as it improves neurologic outcomes after hypoxic brain injury." (Froehler & Geocadin, 2007). The treatment is sometimes combined with a hyperkalemia (high extracellular potassium). Propose how hyperkalemic hypothermia could be neuroprotective.

Together, these two mechanisms reduce the energy requirements of the cell. In doing so, they reduce the chance of lasting brain damage.

Which current corresponds to a flow of Na+ in response to a depolarizing stimulus in a giant axon of a squid?

Transient inward current

Under which circumstances is the Goldman equation equivalent to the Nernst equation?

When a membrane is permeable to only one ion

Why is the white matter lighter than the gray matter?

White matter is richer in myelin, which reflects more light than gray matter.

Which of the following is not an established role for glial cells?

a. Integrating information to assist neural computation

From which part of the nervous system do cells that innervate neuromuscular junctions originate?

a. central nervous system (CNS)

The amplitude of the action potential of a given neuron is:

always the same.

Relative Refractory Period

an unusually strong stimulus can induce an action potential

In the mature central nervous system, glial stem cells with the properties of astrocytes can give rise to

astrocytes, oligodendrocytes, and neurons

Which of Camillo Golgi's contributions enabled Santiago Ramón y Cajal to make observations that suggested that nerve cells are discrete entities?

c. Development of a staining method based on impregnation with silver salts

Which function is a characteristic primarily of neurons only, and not glia?

c. transmits action potentials

When current is injected into an axon,

d. the current will decay exponentially with increasing distance from the injection site (if no action potential is present

An action potential occurs if current injected into a neuron _______ the neuron to reach _______ potential.

depolarizes; threshold

Nodes of Ranvier represent

gaps in myelin wrapping

Neuroethology is the field devoted to studying complex behavior

in the native environment

brain

internal capsule caudate globus pallidus amygdala Putamen and Insular gyri

The voltage clamp method controls the _______ at any desired level.

membrane potential

In a two-compartment model of a cell with a K+-permeable membrane, at K+ equilibrium potential, there is _______ flux of K+ ions.

no net

The _______ most directly affects the rate of information processing within the central nervous system.

propagation speed of action potentia

The part of a synapse to which the contents of synaptic vesicles bind is called the

receptor

The technique that first revealed the tremendous diversity of neuronal cell types, by revealing different cell bodies along with their processes, is

the Golgi technique (stain)

The technique that first revealed the tremendous diversity of neuronal cell types, by revealing different cell bodies along with their processes, is:

the Golgi technique (stain).

The squid giant axon is useful in neuronal studies because

the cytoplasm in the axon can be extruded, thus allowing studies of its composition.

Parkinson's disease is characterized by a significant reduction in dopamine levels in the brain. Treatment includes the administration of L-DOPA in addition to Benserazide, which is a dopa decarboxylase inhibitor (Note: dopa decarboxylase is also known as Aromatic Amino Acid decarboxylase). Describe the logic and potential mechanism of this combination in relieving Parkinsonian symptoms.

L-DOPA on its own can work, but won't be very effective because while it does cross blood brain barrier only little of it crosses through because of the enzymes that synthesize it and turn it into dopamine before it crosses Benserazide inhibits the conversion of L-DOPA to dopamine which means more of it can cross the BBB and get to the other side of the brain where it is then converted. Benserazide doesn't cross the BBB, so it doesn't have any side effects.

Which stimulus is most likely to evoke an action potential?

Large depolarizing current pulse

Which experimental model did Hodgkin and Katz use in their studies of the resting membrane potential?

Living squid neuron

Which statement accurately describes the expression of genes in the nervous system?

Most of the genes in the human genome are expressed in the CNS.

Which statement about myelination is false?

Myelin serves to sharply increase the time constant of the axon.

Which cell type forms the structure labeled C?

Oligodendrocytes in the central nervous system

What is responsible for the initial depolarization?

Opening of Na+ channels

How does membrane permeability to K+ (PK) and Na+ (PNa) change during an action potential?

PK exceeds PNa at rest; PNa temporarily increases during the action potential.

Which type(s) of electrical signals occur(s) within the neural circuit for a spinal reflex?

Receptor potential, synaptic potential, and action potential

Which treatment was shown to eliminate the early inward current in squid giant axons?

Removal of external sodium

Compare/Contrast resting channels, gated channels, and pumps.

Resting channel: generally open when cell is at rest (unstimulated), not affected by extrinsic factors (pain, heat, etc.), important in maintaining resting membrane potential Gated channel: open and close in response to signals Pump: bigger, needs energy, moves ions against concentration gradient, selectively permeable Channel vs pumps: - Channels are smaller, use no energy, passive movement of ions from high concentration to low, selectively permeable - Pumps create and maintain ionic gradients, more complex, slower process