Chapter 48 Neurons Synapses and Signaling Reading Guide

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Transcript of AP Biology Name Chapter 48 - Neurons, Synapses, and S ??Chapter 48 - Neurons, Synapses, and...

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AP Biology Name______________________________ Chapter 48 - Neurons, Synapses, and Signaling

Gah! I HATE Reading The Overview! The function of the neuron, stated as briefly as possible, is to ______________ ______________ ________ ____ ______________. Are neural electrical signals long-distance or short-distance? __________________ Are neural chemical signals long-distance or short-distance? __________________ Are signals that travel the length of a neuron electrical or chemical? _________________ Are signals that travel from one neuron to the next electrical or chemical? _________________

In the diagram to the left, circle the icon that represents an electrical signal. OK, now circle the icons that represent a chemical signal.

A simple cluster of neurons is called a _______________. A large group of neurons is called a _________________. In this chapter, we'll examine the structure of a _______________. Concept 48.1: Neuron Organization And Structure Reflect Function In Information Transfer What are the three stages of information processing in animals? 1. 2. 3. Integration occurs in the ________________ nervous system The nerves found outside of the CNS constitute the ________________ nervous system A bundle of neurons is called a ______________. In the diagram below, label a sensory neuron, an interneuron, and a motor neuron. Neuron Matching

_____ 1. Transmit information toward interneurons. _____ 2. The vast majority of neurons _____ 3. Detect external stimuli _____ 4. Transmit signals to muscle cells _____ 5. Analyze and interpret _____ 6. Trigger gland activity

S. Sensory Neuron I. Interneuron M. Motor Neuron
2 Neuron Structure and Function Is a neuron a specialized cell or a generalized cell? ___________________

Concept 48.2 Ion Pumps And Ion Channels Establish The Resting Potential Of A Neuron

The Resting Potential The two ions that play an important role in electric potentials in neurons are BOTH ______________ charged. They are, of course, the two elements _________________ and _________________. From what food source do YOU get most of your potassium? ________________ How about most of your sodium? _____________

Label: Dendrites Cell Body Nucleus Axon hillock Presynaptic cell Axon Signal direction Synaptic terminals Postsynaptic cell Synapse

In a single neuron: ___________________ Are there multiple dendrites or is there a single dendrite? ___________________ Are there multiple axons or is there a single axon? ___________________ Can a signal (impulse) go in both directions or in one direction only? ___________________ Which transmits signals to other cells: the axon or the dendrite? ___________________ Which is significantly longer, the axon or the dendrite? Other Questions: ___________________ What is the name of the cell junction at the end of the axon? ___________________ What are the three cell types that can receive a neural signal? ___________________ ___________________ ___________________ Is a neurotransmitter electrical or chemical? ___________________ Which cell type secretes the neurotransmitter: presynaptic or postsynaptic? ___________________ In order to transmit signals to many cells, an ___________ (axon / dendrite) must be highly branched. ___________________ The greatest number of synapses are found in _______________ (motor / inter / sensory) neurons. ___________________ Cells that "take care of" neurons are called __________ cells, or _____________. ___________________ In the vertebrate animal body, are there more glial cells or more neurons?

Do most cells maintain ion concentrations that are imbalanced or isotonic with the fluid that surrounds them? ________________ The inside of a neuron is _____________ (negatively / positively) charged. The charge differential between the outside and inside of a neuron is called the m_______________ p_____________. The membrane potential of a resting (non-conducting) neuron is between __________ and __________ mV. What are the two signals that can cause a change in this internal negative charge? 1. 2. It is only when the membrane potential CHANGES that we are able to _______________ a shark, _________________ a frisbee, and __________________ a fur coat.
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What is the overall charge of the outside of the cell? _________________ What is the overall charge of the inside of the cell? __________________ Where is sodium more highly concentrated? _______________________ Where is potassium more highly concentrated? _____________________ What is the little symbol for sodium? _______ What is the little symbol for potassium? _______ What is this? ____________________________

What is this? _________________________________ What is this? _________________________________ The Sodium-Potassium Pump In addition to the potassium being concentrated on the outside of the neuron, there are also negatively charged _____________ ions. In addition to the concentration of sodium on the inside of the neuron, there are also large _____________ (many of them protein molecules). The sodium-potassium pump transports _______ (#) ions out of the cell for every _______ (#) potassium ions that it transports in. Are ion channels selective, or do they allow the entry/exit of any form of ion? ______________________

Potassium ions are concentrated on the ______________ of the cell. Sodium ions are concentrated on the _______________ of the cell. Chloride ions are concentrated on the _______________ of the cell. Large anions are concentrated on the ______________ of the cell. The overall charge of the outside of the cell is _________________. The overall charge of the inside of the cell is __________________. According to your textbook, are gated sodium channels usually closed or open? According to your textbook, are gated potassium channels usually closed or open? The net flow of K+ out of a neuron proceeds until _________________________ _________________________________________________________. In this model, is there a chloride ion channel? ____________ (Yes / No) Why don't the anions escape to the outside of the neuron? Potassium ions will flow out of the cell until the c______________ of potassium ions inside of the cell is balanced by the repulsion of potassium by _________ ions on the outside of the cell.

What is being pumped out?

What is being pumped in?

What is the source of the energy for all of this

pumping?
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48.3 Action Potentials are the signals conducted by axons. Action Potentials The change in membrane permeability to particular ions is due to the o_______ and c___________ of gated ion channels that then alters the membrane p_____________. Ion Matching: Match the ion (in the yellow textbox) with the term or effect (in the green textbox) Graded Potential or Action Potential??????????? ________________ Involve voltage gated ion channels ________________ Depolarization must reach the threshold ________________ Shift in membrane potential that varies in magnitude ________________ Decay with distance from their source ________________ Constant magnitude and regenerate in adjacent regions

of the membrane. ________________ Effect on generation of nerve signal ________________ Increased depolarization causes more sodium gates to open ________________ All or none response

Ions K+ Na+

Terms or Effect ______ Found outside cell when at rest ______ Found inside cell when at rest ______ Cell becomes + as it moves by diffusion when gated channels open ______ Cell becomes as it moves by diffusion when gated channels open ______ Hyperpolarization ______ Depolarization

These three as well!

Membrane depolarization opens _______ types of channels but they respond i____________________ and s_________________. S_____________ channels open _________, initiating an action potential. As an action potential proceeds the sodium channels are i________________ until the membrane returns to r_______________ p_________________. P___________________ channels open more s______________ than sodium but remain __________ until the end of the action potential.

Sequence the following steps that occur during an action potential*: (reference Figure 48.11) ______ Positive feedback brings membrane potential close to ENa ______ Membrane potential brought back to EK

______ Membrane permeability to K+ higher than at rest ___1__ Stimulus depolarizes membrane

______ Threshold is crossed ______ K+ ions diffuse out of the cell

______ Most voltage gated K+ channels open ______ Voltage gated Na+ channels inactivate

______ Na+ channels open ______ Gated K+ channels close

______ Membrane potential returns to resting potential ______ Na+ ions diffuse into the cell

______ More depolarization occurs so more Na+ channels open

*This is a very difficult exercise. One misstep has the potential to affect ALL of the answers that follow.

___________ gates remain closed and therefore a second a____________ p________________ cannot be triggered during the refractory period. For most neurons the onset of an action potential and the end of the r__________________ p______________ is only 1-2 m______________________ so h_________________ can be produced per second by a single neuron. Differences in action potential f___________________ conveys information about s_______________ of the signal. Mutations in the genes that encode i________ c_____________ p_________________ can cause disorders such as m_____________ affecting skeletal muscle and e_________________ affecting the brain.
5 Conduction of Action Potentials

Evolutionary Adaptations of Axon Structure