Chapter 3 study guide psych 36.docx

**1. What is an ion, and what are positive versus negative ions called?** An **ion** is an atom or molecule that has gained or lost one or more electrons, resulting in a net electric charge. **Positive ions** (cations) have lost electrons, so they carry a positive charge. **Negative ions** (anion...

**1. What is an ion, and what are positive versus negative ions called?** An **ion** is an atom or molecule that has gained or lost one or more electrons, resulting in a net electric charge. **Positive ions** (cations) have lost electrons, so they carry a positive charge. **Negative ions** (anions) have gained electrons, giving them a negative charge. **2. List the most critical ions in neuron communication, include whether they are anions or cations.** **Sodium (Na⁺)** -- Cation (positive charge) **Potassium (K⁺)** -- Cation (positive charge) **Chloride (Cl⁻)** -- Anion (negative charge) **Calcium (Ca²⁺)** -- Cation (positive charge) **3. Describe the makeup of the neuron membrane.** The neuron membrane is a lipid bilayer composed of two layers of phospholipids. Each phospholipid has: A hydrophilic (water-attracting) head, facing outward toward the watery environment inside and outside the neuron. A hydrophobic (water-repelling) tail, facing inward, creating a barrier to most water-soluble substances. Embedded within this lipid bilayer are proteins that serve various functions: Ion channels that allow specific ions to pass through. Receptors for neurotransmitter binding. Pumps like the sodium-potassium pump that actively move ions across the membrane to maintain resting potential. **4. Describe the resting potential, including how it is maintained.** **Resting potential** is the electrical charge difference across a neuron\'s membrane when it is not actively sending a signal. The inside of the neuron is more negative relative to the outside, with a typical resting potential around **-70 millivolts (mV)**. How is maintaned 1. **Sodium-Potassium Pump (Na⁺/K⁺ pump)**: - Actively pumps **3 sodium ions (Na⁺)** out of the neuron and **2 potassium ions (K⁺)** into the neuron, using ATP. This creates a higher concentration of Na⁺ outside and K⁺ inside the cell. 2. **Selective permeability**: - The membrane is more permeable to **K⁺** than **Na⁺**, so K⁺ ions tend to leak out of the neuron through **leak channels**, while Na⁺ mostly stays outside. This contributes to the negative charge inside. 3. **Anions trapped inside**: - Large negatively charged molecules (like proteins) are inside the neuron and cannot pass through the membrane, further contributing to the negative resting potential. **5. What is the typical mV range of a neuron at rest?** **-70 mV** being the most common value. **6. In the axon of a resting neuron, how is the composition of the intracellular fluid different from the extracellular fluid with regard to the relative concentrations of sodium, potassium, chloride, and the large negatively charged proteins?** **Intracellular fluid** has high concentrations of **potassium (K⁺)** and **large negatively charged proteins**. **Extracellular fluid** has high concentrations of **sodium (Na⁺)** and **chloride (Cl⁻)**. **7. What is the significance of the sodium-potassium pump? (There\'s more about this in section 3.2.** Uses energy to pump 3 Na+ out and 2 K+ in from intracellular environment **8. What are ion channels (also called leak channels)?** are **protein structures** embedded in the neuron\'s membrane that allow specific ions to passively flow in or out of the cell, following their concentration gradients. These channels are: **Selective**: Each channel is usually specific to one type of ion (e.g., potassium, sodium, or chloride).**Always open**: Unlike gated channels, leak channels are typically open, allowing continuous movement of ions. **9. What are diffusion and electrostatic pressure?** Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Electrostatic pressure refers to the force exerted by the electrical charge difference across the membrane. **10. What\'s the difference between voltage-gated and chemically-gated ion channels? (Note: These are sometimes referred to as voltage-dependent and ligand-dependent respectively.** **Voltage-gated channels** respond to electrical changes, while **chemically-gated channels** respond to chemical signals. Both types are essential for neuron communication and function. **11. What is the ionic basis of the resting potential, and how is it achieved?** determined by the distribution and movement of key ions, particularly sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), and large negatively charged proteins inside the neuron. These processes result in a stable resting membrane potential of about **-70 mV**, allowing the neuron to be ready for action potential generation when stimulated. **Section 3.2** **1. Describe the relationship between depolarization and threshold.** Depolarization must reach the threshold level for the neuron to fire an action potential. If the depolarization does not reach the threshold, the neuron will not fire. Thus, the relationship is that **sufficient depolarization is necessary to reach the threshold, initiating the all-or-nothing response of an action potential**. **2. What is the significance of the axon hillock and axon initial segment (AIS)?** - **Action Potential Generation**: Both structures are essential for determining whether a neuron will fire an action potential based on the integration of synaptic inputs. - **Signal Propagation**: The AIS facilitates the fast conduction of action potentials along the axon, contributing to the efficient transmission of neural signals. **3. Describe the changes in polarity across the axon during the action potential as it relates to the actions of the voltage-gated sodium and voltage-gated potassium channels. (In other words, describe the spike.)** The action potential involves a rapid depolarization due to Na⁺ influx, followed by repolarization due to K⁺ efflux, and a brief hyperpolarization before returning to the resting state. This sequence of events allows for the propagation of the action potential along the axon. **4. What causes the axon membrane to be briefly hyperpolarized at the end of the spike?** The brief hyperpolarization at the end of the spike is caused by the prolonged opening of voltage-gated K⁺ channels, which allows an excess of K⁺ ions to exit the neuron, making the inside of the cell more negative than usual. **5. What is the all-or-none property of the action potential?** The all-or-none property ensures reliable communication between neurons, allowing for consistent signaling in the nervous system. It allows neurons to transmit signals over long distances without losing strength or fidelity. **6. What is the relationship between myelin and the nodes of Ranvier** Myelin insulates the axon and facilitates rapid signal transmission, while the nodes of Ranvier serve as points for action potential regeneration, allowing for efficient and fast communication along the neuron. **7. Distinguish between passive conduction and saltatory conduction of an action** **Passive conduction** is slower and occurs in unmyelinated axons, with diminishing signal strength over distance. In contrast, **saltatory conduction** is faster, occurs in myelinated axons, and allows action potentials to propagate efficiently by jumping between nodes of Ranvier. **8. What is the difference between the absolute and relative refractory periods?** The **absolute refractory period** prevents any new action potentials from occurring, while the **relative refractory period** allows for the possibility of firing again, but only with a stronger stimulus. Together, these periods help regulate neuronal firing and ensure proper signal transmission. **9. What is the significance of the sodium-potassium pump? Note: I typically discuss this within the context of resting potential. Why is that?)** Discussing the sodium-potassium pump in the context of resting potential emphasizes its critical role in establishing and maintaining the ion gradients necessary for neuronal excitability and proper function. It ensures that neurons are primed to respond to stimuli and maintain their electrical stability. **Section 3.3 -** **1. Differentiate axodendritic, axosomatic, and axoaxonic synapses.** Axodendritic synapses connect axons to dendrites, primarily facilitating excitatory/inhibitory transmission. Axosomatic synapses connect axons to cell bodies, often exerting strong control over the neuron\'s firing. Axoaxonic synapses connect axons to other axons, modulating neurotransmitter release. Each type of synapse plays a unique role in the overall functioning of neural networks. **2. Differentiation electrical and chemical synapses?** **Electrical synapses** allow for rapid, bidirectional signal transmission via direct cell-to-cell connections (gap junctions), while **chemical synapses** transmit signals more slowly through the release of neurotransmitters across a synaptic cleft, allowing for more complex signaling and modulation. **3. Contrast \"presynaptic\" from \"postsynaptic\".** The **presynaptic neuron** is responsible for sending the signal and releasing neurotransmitters, while the **postsynaptic neuron** is responsible for receiving the signal and responding to the neurotransmitters through its receptors. This distinction is essential for understanding the flow of information in neural communication. **4. Describe the process of exocytosis.** Exocytosis is a vital process for cell communication and secretion, involving vesicle formation, transport, docking, fusion with the plasma membrane, and the release of contents into the extracellular space. In the context of neurons, it is essential for the release of neurotransmitters, facilitating communication between nerve cells. **5. Explain why the action of neurotransmitters is often likened to a key opening a lock.** The key-and-lock analogy effectively captures the specificity and functionality of neurotransmitter-receptor interactions, emphasizing that only the correct neurotransmitter can bind to its corresponding receptor to trigger a biological response. This analogy helps convey the precision and selectivity involved in neuronal communication. **6. Differentiate ionotropic receptors from metabotropic receptors.** **ionotropic receptors** mediate rapid changes in ion flow and have immediate effects on membrane potential, while **metabotropic receptors** initiate slower, more prolonged signaling cascades that can influence various cellular functions. Both types of receptors are crucial for neuronal communication and play different roles in synaptic transmission. **7. In general, what causes an EPSP, and what causes an IPSP?** **EPSPs** result from the influx of positive ions (like Na⁺), leading to depolarization and an increased likelihood of action potential firing. In contrast, **IPSPs** result from the influx of negative ions (like Cl⁻) or the efflux of positive ions (like K⁺), leading to hyperpolarization and a decreased likelihood of action potential firing. Both types of potentials play critical roles in the modulation of neuronal activity and the overall excitability of the nervous system. **8. What is the impact of IPSPs in a postsynaptic neuron? (Be sure to use and describe the term hyperpolarization in your response.)** IPSPs lead to hyperpolarization of the postsynaptic neuron, making it less likely to reach the threshold for firing an action potential. By decreasing neuronal excitability and influencing the balance between excitatory and inhibitory signals, IPSPs play a crucial role in regulating neural activity and maintaining proper function within the nervous system. **9. What is the impact of EPSPs in a postsynaptic neuron? (Be sure to use and describe the term depolarization in your response.)** EPSPs lead to depolarization of the postsynaptic neuron, making it more likely to reach the threshold for firing an action potential. By enhancing excitability and facilitating neuronal communication, EPSPs play a vital role in the functioning of neural circuits and the overall activity of the nervous system. **Section 3.4 -** **1. Distinguish between an agonist substance and an antagonist substance. Be able to recognize examples of the various ways that a substance might act as an agonist or an antagonist.** Agonists activate receptors, mimicking the effects of natural ligands, while antagonists block or inhibit receptor activity, preventing the effects of agonists or natural ligands. **Agonists**: **Morphine**: Opioid receptor agonist. **Antagonists**: **Naloxone**: Opioid receptor antagonist used to counteract opioid overdose. **2. Fully explain the effects (EPSP or IPSP) on the postsynaptic membrane for the following:** ** An agonist drug interacting with an inhibitory receptor** An agonist drug enhances the effect of a NT. If the NT has an inhibitory effect at that receptor, then an agonist would increase that effect. This means that there would be even more inhibition than normal ** An agonist drug interacting with an excitatory receptor** An agonist drug enhances the effect of a NT. If the NT has an excitatory effect at that receptor, then an agonist would increase that effect. This means that there would be even more excitation than normal. More excitation may lead to an action potential, ** An antagonist drug interacting with an inhibitory receptor** An antagonist drug interferes with the action of a NT. If the NT has an inhibitory effect at that receptor, then an antagonist drug would interfere with the inhibition. Interfering with inhibition means incoming excitation is intensified, which may lead to an action potential. ** An antagonist drug interacting with an excitatory receptor** An antagonist drug interferes with the action of a NT. If the NT has an excitatory effect at that receptor, then an antagonist drug would interfere with the excitation. Interfering with excitation means incoming inhibitory potentials are intensified, making the cell less likely to reach threshold for an action potential. **3. What makes a neurotransmitter excitatory or inhibitory?** A neurotransmitter is considered **excitatory** if it leads to depolarization of the postsynaptic neuron, increasing the likelihood of firing an action potential, typically through the influx of positive ions. Conversely, it is considered **inhibitory** if it leads to hyperpolarization, decreasing the likelihood of firing, often through the influx of negative ions or the efflux of positive ions. **4. What does it mean to say that neurotransmitters are \"denatured\" by enzymes?** When neurotransmitters are said to be **\"denatured\"** by enzymes, it means that enzymes chemically modify or break down these molecules, effectively inactivating them and terminating their signaling action. This process is crucial for maintaining proper synaptic function, regulating neurotransmitter levels, and preventing excessive neuronal stimulation. **5. What is reuptake?** Reuptake is a crucial process in neurotransmitter signaling, involving the reabsorption of neurotransmitters from the synaptic cleft back into the presynaptic neuron. This mechanism regulates neurotransmitter levels, prevents prolonged stimulation of the postsynaptic neuron, and contributes to the efficient recycling of neurotransmitters for future signaling.