UNIT 1 Study Guide PDF

# Chapter 1 ## 1. Describe the structure of the blood-brain barrier (BBB) and explain why it is important. The blood-brain barrier (BBB) is a highly selective semi-permeable membrane that separates the circulating blood from the brain's extracellular fluid in the central nervous system (CNS). I...

# Chapter 1 ## 1. Describe the structure of the blood-brain barrier (BBB) and explain why it is important. The blood-brain barrier (BBB) is a highly selective semi-permeable membrane that separates the circulating blood from the brain's extracellular fluid in the central nervous system (CNS). It is formed by tight junctions between the endothelial cells that line the brain's capillaries. The function of the BBB is to protect the brain from toxins and pathogens that may be present in the bloodstream. It also helps to maintain a stable environment for the brain by regulating the passage of nutrients and waste products. ## 2. Provide a summary of the all-or-none law of action potentials. * The all-or-none law states that the amplitude of an action potential is independent of the strength of the stimulus that initiated it. * If the stimulus reaches the threshold value, an action potential will fire at full strength. * If the stimulus is below the threshold, no action potential will occur. ## 3. Describe the key aspects of the resting potential. The resting potential of a neuron is the electrical potential difference across the cell membrane when the neuron is not actively transmitting a signal. It is typically around -70 millivolts (mV), with the inside of the neuron being more negatively charged than the outside. This potential is maintained by the concentration gradients of ions (sodium, potassium, chloride) across the cell membrane and by the selective permeability of the membrane to these ions. ## 4. Explain the function and process of a neuron's refractory period. * The refractory period is a short period of time after an action potential during which a neuron is unable to fire another action potential. * This period serves to ensure the unidirectional propagation of action potentials along the axon. There are two phases of the refractory period: 1. **Absolute refractory period:** The neuron is completely unable to fire another action potential. 2. **Relative refractory period:** A stronger stimulus is required to generate an action potential. ## 5. What is the role of the myelin sheath? Describe the two types of cells that make the myelin sheath. The myelin sheath is a fatty insulating layer that surrounds the axons of some neurons. * It is made up of two types of cells: 1. **Schwann cells:** Create the myelin sheath in the peripheral nervous system (PNS). 2. **Oligodendrocytes:** Create the myelin sheath in the central nervous system (CNS). The myelin sheath speeds up the conduction of action potentials by increasing the resistance of the axon membrane. **Saltatory conduction:** The action potential jumps from one node of Ranvier (gaps in the myelin sheath) to the next. ## 6. Using motor and sensory neurons as examples, explain the difference between afferent and efferent. * **Afferent:** Neurons that transmit sensory information from the periphery to the central nervous system (CNS). Example: Sensory neurons carrying signals from the skin to the spinal cord. * **Efferent:** Neurons that transmit motor commands from the CNS to the periphery (muscles, glands). Example: Motor neurons sending signals to muscles to contract. # Chapter 2 ## 1. Describe the sequence of events that occurs in synaptic transmission. The sequence of synaptic transmission involves several key steps: 1. An action potential arrives at the axon terminal. 2. Voltage-gated calcium channels open, allowing Ca2+ ions to enter the presynaptic neuron. 3. The influx of Ca2+ triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft. 4. Neurotransmitters bind to receptors on the postsynaptic membrane. 5. This binding leads to a response in the postsynaptic neuron, which can be excitatory or inhibitory. ## 2. Briefly compare the differences between ionotropic and metabotropic receptors. Include their mechanisms of action and how they explain the difference in the effects on the postsynaptic cell. * **Ionotropic Receptors:** These are fast-acting receptors that directly open ion channels upon neurotransmitter binding, leading to immediate changes in the postsynaptic membrane potential. * **Metabotropic Receptors:** These receptors are slower and activate G-proteins, which then initiate a cascade of intracellular signaling events. This can result in longer-lasting effects on the postsynaptic cell. ## 3. Briefly describe spatial summation. Spatial summation occurs when multiple presynaptic neurons release neurotransmitters simultaneously, leading to a cumulative effect on the postsynaptic neuron. This can help the postsynaptic neuron reach the threshold for firing an action potential. ## 4. Describe the main chemical events at a synapse. The main chemical events at a synapse include: 1. Release of neurotransmitters from the presynaptic neuron. 2. Binding of neurotransmitters to postsynaptic receptors. 3. Activation of ion channels or intracellular signaling pathways. 4. Termination of the signal through reuptake or enzymatic degradation. ## 5. Describe the main properties of neuropeptides (neuromodulators). Neuropeptides are larger molecules that act as neuromodulators, influencing the effects of neurotransmitters at the synapse. They can enhance or inhibit neurotransmitter effects and are often involved in regulating complex behaviors such as pain and mood. ## 6. How are neurotransmitters removed from the synapse? Neurotransmitters are removed from the synapse through: * **Reuptake:** Transported back into the presynaptic neuron. * **Enzymatic Degradation:** Broken down by enzymes in the synaptic cleft, ensuring that neurotransmitter signaling is terminated effectively. ## 7. What is the difference between a hormone and a neurotransmitter? * **Hormones:** Chemical messengers released into the bloodstream, affecting distant target organs. * **Neurotransmitters:** Chemicals released at synapses, affecting nearby neurons or target cells directly.