Anatomy and Physiology 1 Exam Review PDF

Anatomy and Physiology 1, Exam 2 Review Section 1: General Nervous system Organization and Cell Types 1. Know the three primary functions of the nervous system (sensation, integration, and motor output). What role does each play in normal physiological activities? Everything that your nervous sys...

Anatomy and Physiology 1, Exam 2 Review Section 1: General Nervous system Organization and Cell Types 1. Know the three primary functions of the nervous system (sensation, integration, and motor output). What role does each play in normal physiological activities? Everything that your nervous system does must start with a sensory stimulus. If not, what information would your brain be making decisions based on? This means that before the CNS can integrate any information, it must get sensory input from the PNS. After receiving that sensory input, the entire goal of the CNS is to determine the appropriate motor output through the PNS (if any). The calculations that go into determine motor output is called integration. 2. Know the anatomical distinction between CNS and PNS. CNS = brain and spinal cord PNS = sensory and motor neurons outside of the CNS 3. Be able to assign any sensory stimulus or motor action to a specific division of the PNS. This is best illustrated using the flow on slide 3 of your notes. 4. Know that glia do not transmit neural (electrical) signals, but are necessary for the function of neurons, which do transmit signals. Be able to describe the general location/form/function of each type of glial cell. The glial cell types are shown/named in the notes and we described their functions throughout the section: Astrocytes use extensions of their cell membranes to form the blood-brain barrier. Oligodendrocytes form myelin segments (white matter) in the CNS. Ependymal cells line the brain’s ventricles and produce CSF. Microglia act like white blood cells (macrophages), preventing infection in the brain. Schwann Cells: form myelin sheath in PNS nerves. 5. Define anterograde and retrograde transport, and why the are needed for neurons to function. Axonal transport involves moving small vesicles filled with important cellulr nutrients or waste products up and down a neuron’s axon. This is essential to deliver nutrients to axon terminals (anterograde), and return waste to the cell body (retrograde). This is necessary because axons can be very long, but the neuron’s nucleus is only found in the cell body. 6. Label sub-cellular parts of a neuron and describe their function. The list of parts is in your lab anatomy list, and the functions are found all throughput the neural communication section. 7. What are the anatomical and functional differences between white and gray matter? Gray matter consists mostly of neuronal cell bodies. This is where integration happens. The benefit of clustering cell bodies together in gray matter is that it brings neurons closer together and allows for shorter, faster connections between them. White mater comprises mostly myelinated axons. These form tracts that connect different regions of gray matter to each other so that they can share information. 8. Describe the anatomical differences between the three structural classes of neurons. Multipolar neurons are used for integration in the brain. You must have multiple processes (dendrites) coming into the cell, otherwise there would be no information to integrate. Unipolar neurons are almost entirely sensory neurons that only take in sensory information to communicate with the CNS, and do not do much integrating. This means that they have one large process that is stimulated on one end by a sensory stimulus, and the other end extends to the CNS. We will describe these in more detail in the next section. 9. Describe the functional differences between the three functional classes of neurons. Sensory neurons are activated by sensory stimuli in the PNS (touch, light, heat, etc…) and cary that information back to the CNS to be integrated. Interneurons are found within the CNS and serve to integrate sensory information to determine an appropriate response (if needed). Motor neurons leave the CNS and project back out to the PNS where they connect to muscles or glands to stimulate a specific response. 10. You prick your finger on something sharp and pull your hand back. What nervous system pathways are being used here? Somatic sensory neurons will carry a sensory signal through the PNS to the spinal cord,and then upward toward the brain. Assuming the sensory signal makes it through the thalamus (sensory filter), it will lead to the primary somatosensory cortex in the cerebrum. From there information will be shared with the relevant part of the primary motor cortex, which will activate the necessary muscles through somatic motor neurons that run down through the spinal cord and out to muscles. 11. You eat a large meal and your pancreas secretes digestive enzymes. What nervous system pathways are being used here? Visceral sensory neurons carry information from the stomach up to the brain, which integrates that information and activates stomach secretions though autonomic (parasympathetic) motor neurons. Section 2: Neurophysiology - Graded and action potentials 1. Why do we call the graded potential in the soma an analogue signal, and the action potential in an axon a digital signal? Analogue signals are coded by intensity. This fits a graded potential, because it has to be intense enough (depolarized enough) to reach threshold voltage. Digital signals are all or nothing, and intensity doesn’t matter. This means they must be coded by frequency. This fits action potentials, in that intensity doesn’t matter – the all look the same. The only thing you can do is send them more or less often (frequency). 2. The analogue signal produced by ligand-gated ion channels in the soma is converted to a digital action potential at the axon hillock. What molecule makes this conversion possible, and how does it do it? Voltage-gated sodium channels do this by opening when threshold voltage is reached, beginning a positive feedback signal. This opening is an “all or nothing” event, making it digital. 3. Once an action potential starts, it sets off a chain reaction down the axon. Explain how this chain reaction works. Voltage-gated sodium channels open in response to reaching threshold (measured in mili-volts). This allows more sodium to enter the cell. This sodium diffuses over to the next channel, increasing the voltage surrounding it to each threshold, and the next one opens. This happens repeatedly all down the axon until a synapse is reached. 4. What is the role of voltage gated potassium channels in the sequence of events that make up an action potential. Voltage-gated K+ channels open when voltage-gated sodium channels are inactivated. Since K+ is built up inside the cell, it will flow out when the channels open. Losing this positive ion (K+), make membrane potential drop (repolarize). This is important for resetting the membrane potential to be back below threshold and allowing voltage-gated channels to close again. 5. What would happen if the number of potassium channels in the membrane were cut in half? K+ would leave the cell much more slowly, meaning repolarization would take much longer. 6. Describe the absolute and relative refractory periods. When do they occur, and what mechanism makes them possible. Absolute: Sodium Channels are inactivated very quickly after they open, and no amount of depolarization can open them. This allows the membrane potential to reset and prepare for the next action potential. Relative: Na+/ K+ ATPase is pumping sodium out of the cell, and voltage-gated K+ channels remain open. With those K+ ions continuing to move out of the cell, this leads to hyperpolarization, making reaching threshold very difficult (but still possible with a very strong stimulus). 7. What would happen if there were no absolute refractory period (if sodium channels were never inactivated)? Membrane potential could never repolarize, and the neuron would remain “on” forever. This is because the absolute refractory period is needed to end positive feedback and get membrane potential back below threshold. 8. How do length and diameter of an axon influence signaling speed? See the equation on slide 70: shorter and wider neurons send faster action potentials. This is because both of those thing decrease resistance, and resistance slows speed of transmission. This explains why longer neurons (as in peripheral motor neurons) have thicker axons. 9. How does myelination increase signal speed? Each myelin segment counts as its own length in the resistance equation since the signal “jumps” from one node to the next. This makes resistance go down, and speed go up. This means that axons that need to be fast need to have lots of myelin. 10. When is it better not to myelinate an axon. Why? When speed doesn’t matter (parasympathetic motor output is a good example). You would just be wasting resources at this point, because myelination is expensive (lots of cells, lipids, protein, etc...). 11. Define a neurotransmitter, and recognize the broad functions of the different NTs we talked about in class. See slides 27-31 Section 3: Neurophysiology - Synapses 1. What protein in the membrane of the axon terminal detects action potentials? How does it “activate” a response at the synapse? Voltage-gated calcium channels open in response to an action potential. Calcium flows into the axon terminal, causing vesicles to release their neurotransmitter into the synaptic cleft. 2. Describe the cycling of vesicles in the pre-synaptic neuron. Vesicles are reused after each neurotransmitter release. This means that they must either be packed full of recycled neurotransmitter that we taken back up through channels from the synaptic cleft, or the axon terminal must make new NT to refill them. 3. What factors determine the strength of a neurotransmitter on the post-synaptic neuron? The amount of NT released, and how long it stays in the synaptic cleft (duration). Duration can be influenced by using enzymes in the synaptic cleft to degrade the NT, and also by using active transport pumps to recycle it back into the pre-synaptic neuron. 4. What determines whether a synapse produces an excitatory or inhibitory response? Which ion channel is opened. A relative increase in sodium permeability will produce a excitatory response (depolarization). A relative increase in potassium or chloride permeability will produce an inhibitory response (repolarization or hyperpolarization). 5. Explain why it would be detrimental to the brain for electrical signal to jump from one neuron to another. Every firing of every synapse would active the next neuron, and very soon every neuron in the brain would be firing. If every neuron was on, there would be no way to integrate signals. This is why it is imprint that many synapses have to fire together to produce a strong enough graded potential that will lead to threshold. 6. Explain why the frequency (not intensity) of action potentials determines the amount of activity at a synapse. Action potentials don’t differ in intensity – they all look the same. All you can do is send them more or less often. This is frequency, and it is what determines how much neurotransmitter is released at a synapse. Section 4: Brain anatomy and physiology 1. Where (and by what cells) is CSF produced? Ependymal cells lining ventricles produce CSF. 2. Track the flow of CSF through the brain until it returns to the blood. Lateral ventricle -> interventricular foramen -> third ventricle -> cerebral aqueduct -> fourth ventricle - > out to spinal cord (central canal) or to subarachnoid space (through lateral apertures) -> back to veins in the space subdural and subarachnoid spaces. 3. What is the purpose of having gyri/sucli in the cerebral cortex? The purpose is to increase the amount of cortex without making it too thick. Gyri do this by increasing surface area, allowing for more gray matter, without thickening it. This allows more regions of cortex to be present, giving the brain more interneurons to integrate information. 4. Which region of the brain controls voluntary motor activity? The primary motor cortex in the frontal lobe of the cerebrum. Neurons from the primary motor cortex leave the brain and connect to skeletal muscles to control their contractions. 5. What brain regions would you have to move to find the insula? The frontal and temporal lobes of the cerebrum. 6. Describe the concept of brain lateralization. Each side of the brain performs slightly different tasks. This means that they have to communicate and share information if information is going to be integrated properly. The most obvious example of this is the contralateral connections between the brain and the rest of the body: the left side of the brain takes in sensory information and sends of motor information from/to the right side of the body. 7. What is a nucleus in the brain? What do we call an equivalent structure in the PNS? A nucleus is a cluster of cell bodies that are working together to perform a specific task (like the basal nuclei in the cerebrum). In the PNS, we call this a ganglion. 8. What is the benefit of the cerebral arterial circle? To redistribute blood flow across the surface of the brain if blood flow is partially blocked in one region. This ensures an even distribution of blood across the entire surface of the brain. 9. Identify each lobe of the cerebrum, and be able to describe its major functions. See slide 46. 10. What is the difference between white and gray matter? Why is white matter found in the interior of the cortex, and gray matter makes up the periphery? See section 1, question 7. It is important for white matter to be on the interior, because information is entering/leaving the brain through its center (the medulla). If white matter was on the outside, axons would have to wrap all around the outside of the brain to get to internal gray matter, wasting a lot of space. This is reversed in the spinal cord, where white matter is on the outside. This makes sense, given that information enters/leaves the spinal cord at its perimeter instead if through the middle. 11. What is a tract? Describe the three different kinds of tracts found in the brain. A tract is a bundle of axons that are connecting one region of the brain to another. See slide 45 for descriptions of each category. 12. Describe the functions of the primary motor cortex and the premotor cortex, and how they work together to coordinate movement. The premotor cortex plans movements based on sensory information. The primary motor cortex executes those commands by sending a signal to skeletal muscles out in the body through the PNS. 13. Why do we draw a picture of a person across the primary motor and somatosensory cortices? What does the size of each body part indicate? Each body part indicated the region of cortex responsible for receiving sensory information for, or sending out motor signals to that body part. The size indicates how sensitive that body part is (sensory) or how finely controlled it is (motor).