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Questions and Answers
What type of ion channels are always open?
What type of ion channels are always open?
Sodium leak channels are slower to open and close compared to potassium leak channels.
Sodium leak channels are slower to open and close compared to potassium leak channels.
False
What is the charge distribution inside and outside of a resting cell?
What is the charge distribution inside and outside of a resting cell?
Inside is negatively charged, outside is positively charged.
The sodium-potassium pump pumps ______ sodium ions out for every ______ potassium ions in.
The sodium-potassium pump pumps ______ sodium ions out for every ______ potassium ions in.
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What initiates an action potential at the axon hillocks?
What initiates an action potential at the axon hillocks?
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Match the following ion channels with their characteristics:
Match the following ion channels with their characteristics:
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Which of the following statements about potassium and sodium inside a cell is true?
Which of the following statements about potassium and sodium inside a cell is true?
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What is the primary role of graded potentials?
What is the primary role of graded potentials?
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Which neurotransmitter is considered the 'reward neurotransmitter'?
Which neurotransmitter is considered the 'reward neurotransmitter'?
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Norepinephrine is an inhibitory neurotransmitter.
Norepinephrine is an inhibitory neurotransmitter.
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What role do astrocytes play in relation to glutamate?
What role do astrocytes play in relation to glutamate?
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The preganglionic neurons that go to the adrenal gland extend all the way to the gland without a ______.
The preganglionic neurons that go to the adrenal gland extend all the way to the gland without a ______.
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Match the following hormones with their respective glands:
Match the following hormones with their respective glands:
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Which of the following receptors is excitatory and found on skeletal muscle?
Which of the following receptors is excitatory and found on skeletal muscle?
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Serotonin is primarily involved in regulating metabolic functions.
Serotonin is primarily involved in regulating metabolic functions.
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What is the primary function of tropic hormones?
What is the primary function of tropic hormones?
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The sympathetic nervous system is also called ______ because all ganglions are interconnected.
The sympathetic nervous system is also called ______ because all ganglions are interconnected.
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Which type of hormone is typically slow-acting and binds to intracellular receptors?
Which type of hormone is typically slow-acting and binds to intracellular receptors?
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The synapse in the autonomic nervous system is always inhibitory.
The synapse in the autonomic nervous system is always inhibitory.
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Name one effect of cocaine on neurotransmitter activity.
Name one effect of cocaine on neurotransmitter activity.
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The ______ division of the autonomic nervous system arises from the cranial and sacral regions.
The ______ division of the autonomic nervous system arises from the cranial and sacral regions.
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Match the following neurotransmitters with their primary functions:
Match the following neurotransmitters with their primary functions:
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What is the primary reason for repolarization in a neuron?
What is the primary reason for repolarization in a neuron?
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Hyperpolarization makes it easier for a neuron to reach action potential.
Hyperpolarization makes it easier for a neuron to reach action potential.
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What is the threshold membrane potential that triggers an action potential?
What is the threshold membrane potential that triggers an action potential?
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The ________ period is when a neuron cannot produce another action potential.
The ________ period is when a neuron cannot produce another action potential.
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Which neurotransmitter is primarily inhibitory in the central nervous system?
Which neurotransmitter is primarily inhibitory in the central nervous system?
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Action potentials can be summated.
Action potentials can be summated.
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What is the effect of graded potentials on the membrane potential?
What is the effect of graded potentials on the membrane potential?
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The events during an action potential include the opening of voltage gated Na+ channels followed by the opening of voltage gated ________ channels.
The events during an action potential include the opening of voltage gated Na+ channels followed by the opening of voltage gated ________ channels.
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Match the following neurotransmitters with their associated neurons:
Match the following neurotransmitters with their associated neurons:
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Which of the following events occurs first in the action potential sequence?
Which of the following events occurs first in the action potential sequence?
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Temporal summation occurs when multiple action potentials arrive at different times, leading to a graded potential surpassing the threshold.
Temporal summation occurs when multiple action potentials arrive at different times, leading to a graded potential surpassing the threshold.
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What is meant by rate coding in action potentials?
What is meant by rate coding in action potentials?
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Inhibitory Post Synaptic Potentials (IPSPs) lead to the cell becoming ________.
Inhibitory Post Synaptic Potentials (IPSPs) lead to the cell becoming ________.
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What chemical is released at the axon terminus to communicate with the next neuron?
What chemical is released at the axon terminus to communicate with the next neuron?
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Both graded potentials and action potentials can trigger neurotransmitter release.
Both graded potentials and action potentials can trigger neurotransmitter release.
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Study Notes
Resting Membrane Potential
- Cells maintain a difference in electrical charge across their membrane, with the outside positive and the inside negative.
- Negatively charged proteins inside the cell can't leave.
- Potassium ions (K+) inside the cell balance out the negative charge.
- Potassium leak channels allow K+ to leak out slowly.
- Voltage-gated potassium channels have one gate, causing slower opening/closing.
- High intracellular K+ concentration and low extracellular K+ concentration.
- Sodium leak channels are present, but sodium (Na+) is more concentrated outside the cell and leaks in faster.
- Voltage-gated sodium channels have two gates, allowing quicker opening/closing.
- More potassium leak channels than sodium leak channels.
- The electrical gradient attracts potassium back into the cell, but passive leakage also plays a factor.
- Cells are more permeable to potassium (25 times more permeable) than sodium.
- Electrochemical gradient: considers both charge and concentration of ions.
- Concentration gradient: considers only the concentration difference of ions across the membrane.
- The Sodium-Potassium pump maintains ion gradients (3 Na+ out for 2 K+ in).
Ion Channels
- Leakage (non-gated) channels: Always open.
- Voltage-gated channels: Part of the protein changes shape to open/close in response to changes in membrane potential.
- Ligand-gated (chemically-gated) channels: Part of the protein changes shape to open when a ligand or substrate binds.
Membrane Potential Changes
- Used as communication signals within cells.
- Cause two types of signals:
- Graded potentials: Incoming signals operating over short distances, starting at dendrites; can be excitatory or inhibitory.
- Action potentials: Long-distance signals along axons, starting at the axon hillock.
Graded Potentials
- Can be hyperpolarizing or depolarizing.
- Are decremental (decrease in amplitude as they travel).
- Vary in magnitude, depending on the strength of the stimulus.
- Short-distance communication.
- Can be summated (added together).
- Can trigger an action potential.
Action Potentials
- Generated by graded potentials that reach threshold (approximately -55 mV).
- Always depolarizing; no summation.
- All-or-none phenomenon: either happens completely or not at all.
- Always excitatory.
- Not decremental: maintain amplitude as they travel.
- Strength coded by frequency (rate coding), not amplitude.
Refractory Periods
- Periods where another action potential is harder to produce.
- Absolute refractory period: the neuron cannot produce another action potential, activation gates are still open.
- Relative refractory period: the neuron can fire another action potential, but it needs a larger stimulus, inactivation gates have closed, but voltage is further from threshold.
Action Potential Propagation
- The movement of an action potential along an axon.
- Positive feedback involving voltage-gated channels is vital for propagation.
- At the axon terminal, voltage-gated calcium channels open, triggering neurotransmitter release.
- Hyperpolarization can make it harder to generate an action potential.
Events of an Action Potential
- Voltage-gated Na+ channels open, increasing Na+ permeability. Depolarization occurs.
- Voltage-gated K+ channels open, increasing K+ permeability.
- Hyperpolarization occurs.
Events of Action Potential at a Synapse
- Neurotransmitter (e.g., ACh) released at axon terminal, binds receptors on dendrites.
- Receptor opening causes Na+ influx, generating graded potentials.
- Magnitude of graded potential depends on neurotransmitter binding.
- Sufficient graded potential triggers action potential at axon hillock.
- Axon potential propagation occurs.
- At the axon terminal, voltage-gated Ca2+ channels open, stimulating neurotransmitter release.
Postsynaptic Potentials
- Synonymous with graded potentials.
- Excitatory postsynaptic potential (EPSP): Depolarizing graded potential.
- Inhibitory postsynaptic potential (IPSP): Hyperpolarizing graded potential.
Synaptic Summation
- Spatial summation: Multiple graded potentials from different locations are added together at the trigger zone.
- Temporal summation: Multiple graded potentials from the same location arrive in rapid succession.
Synapses
- Different neurons store different neurotransmitters.
- Cholinergic neurons: Contain acetylcholine (ACh).
- Adrenergic neurons: Store norepinephrine (NE) and epinephrine.
- GABA: Main inhibitory neurotransmitter in the CNS; involved in memory, learning, and anxiety; opens Cl- channels.
- Glutamate: Main excitatory neurotransmitter in the CNS; involved in learning, memory, and cognition.
- Dopamine: Important in motor control, reward and motivation.
- Norepinephrine: Excitatory neurotransmitter, plays a role in learning and behavior control.
- Serotonin: Regulates mood, sleep, appetite, and body weight.
Autonomic Nervous System
- Controls involuntary functions (organs, glands, smooth muscle).
- Sympathetic: Pre-ganglionic (cholinergic, short), post-ganglionic (adrenergic, NE). Generally, excitatory.
- Parasympathetic: Pre-ganglionic (cholinergic, long), post-ganglionic (cholinergic, muscarinic receptors). Generally, inhibitory.
- Ganglia are connected to autonomic nervous system pathways..
Endocrine System
- Controls growth, development, metabolism, and reproduction through hormones.
- Hormones: Chemical messengers transported through the blood.
- Endocrine glands: Secrete hormones.
- Exocrine glands: Have ducts.
Hormone Classes
- Peptide hormones: Made of amino acids; fast-acting; bind to receptors on cell surface..
- Steroid hormones: Made of cholesterol; slow-acting; bind to intracellular receptors.
Target Cell Specificity
- Hormones act only on cells with specific receptors.
Hormone Release Control
- Stimulated by:
- Tropic hormones: Hormones that stimulate the release of other hormones.
- Humoral factors: Substances in the blood (e.g., glucose, calcium).
- Nervous system: E.g., the sympathetic nervous system releasing epinephrine.
Pituitary Gland
- Connected to the hypothalamus.
- Posterior pituitary: Neural tissue; secretes antidiuretic hormone (ADH) and oxytocin.
- Anterior pituitary: Glandular tissue; secretes tropic hormones (e.g., growth hormone).
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Description
Explore the intricacies of the resting membrane potential in cells. This quiz delves into the roles of potassium and sodium ions, the function of various channels, and the importance of electrical gradients. Test your understanding of how these factors contribute to cellular charge differences.
