A/P Chapter 11
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What organs make up the central nerve system?
Peripheral Nerve system?
- 1. Brain and Spinal Cord
- 2. All the nerves outside the Central Nervous system.
What is the number of pairs of cranial nerves and spinal nerves in the PNS?
- 12 pairs of cranial nerves
- 31 pairs of spinal nerves
Differentiate between the sensory and motor divisions of the PNS (peripheral nervous system)
- Sensory- (afferent) Carries impulses towards the CNS (think about putting hand towards head-sensing)
- Motor- (efferent) Carries impulses away from the CNS (a car driving away)
Differentiate between the somatic and the autonomic parts of the motor division (which is in the PNS).
- 1. Somatic parts controls the skeletal muscles. (voluntary action)
- 2. Autonamic part controls the cardiac muscle, smooth muscles and glands. (involuntary action). (heart beats automatically)
Differentiate between the sympathetic and parasympathetic divisions of the autonomic part (which is in the motor division, which is in the PNS).
- 1. The sympathetic division is composed of "Fight or Flight" responses. (increased heart beat)
- 2. The Parasympathetic Divison is associated with "Vegetative" responses. (digestion and urination)
What is the enteric nerve system?
Is related to the autonomic (automatic) control of digestive organs. (stomach movement, etc.) parasympathetic action.
Define sensory receptors, nerves, ganglia, and plexi.
- 1. Sensory receptors- detect stimuli like sound, light, and heat and change the energy form into a nerve impulse.
- 2. Nerves- Connect the CNS to sensory receptors and to effectors like muscles and glands.
- 3. Glanglion- is a collection of nerve cell bodies in the PNS.
- 4. Plexus- is an extensive network of axons or nerve cell bodies in the PNS.
Describe the location of and the functions of these parts of a neuron: Cell body, Nissl bodies, Dendrites, and the axon.
- Cell body (soma)-Designed for the sythesis of proteins (neurotransmitters).
- Nissl body- Are collections of rough endoplasmic reticulum (RER), primary sie of protein sythesis in neurons, and is located in the cell body and dedrites.
- Dendrites- Are short structures attached to the cell body that help to increase the surace area for sensory input.
- Axons- Is a long structure that conducts the nerve impulse away from the cell body towards another neuron, to a receptor or to an effector.
What are presynaptic terminals? What do they connect to? What is stored there?
- 1. They form the end of an axon.
- 2. They connect to dendrites of other neurons, as well as muscles or glands.
- 3. They store synaptic vesicles that contain neurotransmitters.
What are collateral axons? What is an example of their use?
- 1. Collateral axons are branches off of the main axon that allow action potentials to be carried AWAY FROM the cell body by different routes.
- 2. An example is after you remove your hand from a hot object, you realize that the object was hot because a collateral axon carried the information to the brain for interpretation.
- (The main axon caused the hand to be moved and the collateral axon carried the information that the object was hot.)
Name and describe 3 materials that are transported down the axon. (made in the cell body and carried down to the end of the axon by interaxonic transport).
- 1. Cytoskeletal proteins- neurofibrils used to support the axon (think of the skeleton-it supports the muscles)2. Mitochondria- involved in the release of energy from food. (They make ATP)3. Neurohormone vesicles- contain neurotransmitter in an inactive form.
Name and describe 3 materials that are transported up the axon. (From the end of the axon back to the cell body)
- 1. Damaged organelles- Ruptured vesicles, mitochondria, ect.
- 2. Recycled plasma membrane- Membrane around a synaptic vesicle breaks to release neurotransmitter.
- 3. Endocytosis substances- Recycled epinephrine or norepinephrine.
Differentiate these neurons by function: Sensory, Motor, and Interneuron.
- 1. Sensory- Carry impulses TO THE CNS from receptors. (like pain impulses)
- 2. Motor Neurons- Carry impulses FROM THE CNS to effectors like muscles or glands.
- 3. Interneurons- Connect sensory and motor neurons together.
Differentiate these neurons by structure and location: Multipolar, Bipolar, and Unipolar.
- 1. Multipolar neurons- Many dendrites, 1 cell body and 1 axon. (Motor Neurons)
- 2. Bipolar neurons- 1 dendrite, 1 cell body, and 1 axon. (eye retina and the nasal cavity)
- 3. Unipolar neurons- 1 process extending from the cell body which divides into a peripheral process and a central process. (pain receptors).
List the three functions of neuroglia.
- 1. Support
- 2. Nourish
- 3. Protect
Discribe the functions of astrocytes, ependymal cells, microglial cells, and oligodendrocytes. (They are Neuroglia of the CNS)
- 1. Astrocytes- support neurons (structure, transport, communication, nutrition) and form the blood-brain barrier.
- 2. Ependymal cells-Make cerebrospinal fluid and have cilia for cerebrospinal fluid movement.
- 3. Microglial cells- Phagocytic cells that defend the neurons from infection.
- 4. Oligodendrocytes- Manufacture myelin sheaths for the neurons in the CNS. (those in the brain and spinal cord).
Describe the functions of these PNS neuroglial cells: Schwann cells and Satellite cells:
- 1. Schwann cells- form the myelin sheaths of nerves in the PNS (peripheral Nerve System)
- 2. Satellite cells- support the neurons of the PNS. (absorb poisons such as lead and heavy metal).
What is the function of myelin? Define salutatory conduction.
- 1. Myelin- protects and electrically insulates axons.
- 2. Salutatory Conduction-Action potentials travel faster in myelinated axons by "leaping" from node to node.
Describe the structural difference between a Node of Ranvier and an internode.
- 1. Node of Ranvier- is a GAP and occurs where the myelin is interrupted.
- 2. Internode- is a segment of myelinated axon. (section of axon between the Node of Ranvier)
Define white matter. Define gray matter.
- 1. White Matter- is bundles of parallel axons covered with myelin. It is white because of the presence of myelin(which is made of lipids)
- 2. Gray Matter- performs integrative functions and is a relay area between sensory and motor neurons.
Define a nerve tract.
Nerve Tract- is axons of that carry action potentials from one area to another. Tracts are mostly found in the spinal cord (CNS).
What are nuclei and where are they located.
Nuclei-They are collections of gray matter found scattered within the white matter of the brain.
Define action potential. What ions are involved in creation of an action potential?
- 1. Action Potential- is an electrical signal produced by a cell. This is a nerve impulse.
- 2. The ions involved are the sodium (Na+) ion and the potassium (K+) ion.
What are the charge characteristics of a resting membrane?
Has a positive (+) charge on the outside and a negative (-) charge on the inside.
Why is a resting membrane like a set mouse trap?
If a membrane is not carrying an impulse, it is resting and ready to carry an impulse. (like a set mouse trap).
Where does the energy come from that is stored in a resting membrane?
Positive and negative ions
What occurs to cause a resting membrane to release it's energy? In what form is this energy?
- 1. When the ions move back to where they started.
- 2. Cellular electricity.
What is the job of the sodium-potassium pump? What is the ratio of ions moved by the pump? Why is there a difference?
- 1. It maintains the sodium (Na+) and potassium(K+) ion differences across the cell membrane which keeps the membrane ready to carry an impulse.
- 2. 2 K+ ions are transported in for every 3 Na+ ions that are transported out. (for every ATP used.)
- 3. For ATP used.
Why is there a continual presence of negative charges inside the cell? What is the only way that the inside of the cell could become positively charged?
- 1. Negative charged proteins inside the cell are too large to pass through the cell membrance and is is the presence of these proteins that creates the negative charge on the inside of the cell.
- 2. Any change of charge in the cell comes only from the movement of (+) charged ions into or out of the cell.
What is the overall effect of leaking negative charged ions to the inside?
The movement of (-) charged ions (like chloride) into the cell could delay charge changes and make the cell less sensitive.
Describe nongated ion channels. Why is the membrane more permeable to potassium than to sodium ions?
- 1. They are always open. They are primarily responsible for the permeability of the plasma membrane to ion movement when the cell is at rest.
- 2. Because there are more poatssium nongated channels then there are sodium channels.
What two factors will cause gated channels to open or close?
- 1. Response to stimuli like ligands
- 2. voltage change
What is a ligand? What is the relationship of a ligand to a receptor? What are common locations of ligand-gated channels?
- 1. ligand- is a molecule that binds (combines with) a receptor.
- 2. They open or close when a ligand binds to a receptor.
- 3. In membranes of nerve and muscle tissue, as well as glandular tissue.
Explain how acetylocholine works with a ligand-gated channel.
Acetylocholine is a ligand that binds to a receptor site.
How do voltage-gated channels work? What are common locations of Na+ and K+ voltage-gated channels? What are common locations of Ca+2 voltage-gated channels?
- 1. They open and close in response to small voltage changes across the cell membrane.
- 2. They are found in electrically-excitable tissue such as nerves.
- 3. They are found in smooth muscle cells and in cardiac muscle cells.
What are two locations of other gated ion channels?
TOUCH receptors and TEMPERATURE receptors.
Define the resting potential. What is the common value of the RMP (resting membrane potential)?
- 1. The electrical charge difference across a plasma membrane.
- 2. The value of the RMP is -70millivolts (mV)
The RMP is created by having____ ions on the ouside of the membrane and ___ ions on the inside of the membrane. If the positive-charged potassium ions are on the inside of the membrane, why isn't the inside positive when the RMP is established?
- 1. Sodium
- 2. Potassium
- 3. The negatively-charged proteins remain on the inside and out-number the potassium ions.
Interpret the meaning of a RMP value like -70 mV.
The value of -70 mV indicates that the inside of the cell membrane is negative (-) abd tge vakye if 70 indicates how negative the inside of the membrane is.
When potassium ion channels open, potassium ions move from the inside of the cell to the outside. What are 2 forces that cause the movement out?
Diffusion and repulsion forces
Potassium ions will continue moving to the outside until reverse forces cause an equilibrium to be set up. What would these reverse forces be?
Ions will try to reenter the cell due to the attraction of + for _
If the normal RMP value is -70mV., then a RMP value like -40mV. would indicate that there are fewer potassium ions moved to the outside creating a lower value than -70. What would be the value of the RMP if more potassium ions were moved out than normal?
What changes are seen in membrane sensitivity with changes in the value of the RMP?
- Hypopolarization (RMP is more postitive- K+ moving out)
- Hyperpolarization (RMP is more negative Less K+moving out)
What is the overall effect of having more potassium ions than normal outside the membrane when the potassium channels open? This would lead to what RMP value? What effect would this have on membrane sensitivity? Why is this called hypopolarization?
- 1. Hypopolarization
- 2. Smaller RMP change
- 3. The membrane potential tends to become more positive.
- 4. It causes the membrane to have a lower threshold making the neuron more excitable.
What would be the overall effect of having less potassium than normal on the ousdie of the membrane when the potassium channels open? This would lead to what RMP value? What effect would this have on membrane sensitivity? Why is this called hyperpolarization.
- 1. Hyperpolarization
- 2. Larger RMP change
- 3. The charge difference now becomes more negative
- 4. It leads to the membrane having a higher threshold making the membrane less excitable.
What would be the effect on the RMP if the number of potassium channels that are opened would be increased? Why would this condition be called hyperpolarization?
- 1. to become hyperpolarized and therefore less sensitive.
- 2. There would be a decrease in potassium ions
What would be the effect of opening additional sodium channels? Why is this called a hypopolarization?
- 1. It would become hypopolarized and more sensitive.
- 2. There would be more sodium on the inside making the neuron more excitable.
What is the effect of the presence of calcium ions on the ability sodium channels to open effectively?
It makes Na+ channels open with difficulty, so it takes more work to get the sodium into the cell and the membrane becomes hyperpolarized and therefore less sensitive.
Why would the presence of excess calcium ions on the outside of a membrane cause a hyperpolarized condition? Why would a deficiency of calcium ions outside the membrane cause hypopolarized condition.
- 1. Because the inside is still less negative.
- 2. Because the calcium is what is making the outside less negative.
Define a local potential. Define a graded potential.
- 1. Local potential- Is a stimulus that is applied at a specific location on the cell membrane causes a change in the RMP at the location on the membrane.
- 2. Graded Potential- Is a change in the membrane potential that is localized to one area of the plasma membrane.
- (THEY ARE THE SAME)
What is the relationship between stimulus strength and sodium channel openings?
- A stimulus strength determines the number of Na+ channels that open.
- A weak stimulus will open a small number of sodium channels while a strong stimulus will open a large number of sodium channels.
Summation- occurs when a stimulus causes a local potential and then a second stimulus adds to it causing a larger depolarization.
Threshold- If a local potential causes depolarization to reach threshold, the membrane will depolarize completely.
Describe the all or none principle.
- If a stiumulus produces a depolarizing graded potential that is large enough to reach threshold, all the permeability changes responsible for an action potential proceed without stopping and are conctant in magnitude. (The "all" part)
- If a stimulus is so weak that the depolarizing graded potential does not reach threshold, few of the permeability changes occur. The membrane potential returns to its resting level after a brief period without producing an action potential (the "none" part).
- Example" The camera shutter.
Describe the process of depolarization. What channels open? What happens to the charge inside the membrane?
- 1. The change in charge across the plasma membrane causes some voltage-gated Na+ channels to open. If threshold is reached, huge number of Na+ channels are opened.
- 2. Na+ channels.
- 3. It becomes positive.
Describe the process of repolarization. What channels open? What happens to the charge inside the membrane?
- 1. Potential difference changes cause the sodium (Na+) inactivation channels to close, which keeps the sodium ions from entering the cell.
- 2. Potassium
- 3. It becomes negative.
Define afterpotential. Why does the resting membrane potential return to normal after the afterpotential has occurred?
- 1. Afterpotential-it occurs because the potassium (K+) channels remain open slightly longer than the time required to bring the membrane back to tis original potential.
- 2. Because potassium ions naturally leak back into the inside of the membrane. (reducing the negativity by the addition of + charged back to the inside.)
Define absolute refactory period. How does the relative refactory period differ?
- 1. Absolute Refactory Period- that the membrane has a complete insensititvity to any stimuli.
- 2. Relative Refactory Period- that a stronger than threshold stimulus can inititate another action potential.
What events signals the end of the relative refactory period.
When the potassium (K+) channels close.
Define action potential frequency. What is the ADF directly proportial to?
- 1. Action Potential Frequency (ADF)-as a number of action potentials produced per unit of time.
- 2. to stimulus strenght and to the size of the action potential.
Contrast a subthreshold to a threshold stimulus.
- 1. Subthreshold Stimulus- is not strong enough to produce a local potential.
- 2. Threshold Stimulus- is strong enough to cause the plasma membrane to reach threshold.
Contrast a maximal stimulus to a submaximal and a supramaximal stimulus.
- 1. Maximal Stimulus- can produce the maximim frequency of action potentials.
- 2. Submaximal Stimulus- are stimuli between the threshold stimulus and the maximal stimulus.
- 3. Supramaximal Stimulus- is stronger than a amaximal stimulus. Cannot produce a greater frequency of action potentials than a maximal stimulus can because there is a limit to the number of aciton potentials that can be produced/second.
What is the reason that a supramaximal stimulus cannot produce a greater frequency of action potentials that a maximal stimulus?
Because there is a limit to the number of action potentials that can be produced/second.
What is the relationship between frequency and the severity of pain or the working of a gland?
- 1. A low frequency means week muscle contractions as well as low secretion from a gland. (mild pain)
- 2. A high frequency would mean sterong muscle contraction or high secretion from a gland. (severe pain)
Why can action potential progagation be compared to a falling line of dominos.
Go in only one direction.
Explain why propagation can only be in one direction.
Because the absolute refractory period prevents 2-way propagation.
The speed of conduction in a nerve fiber depends on what two factors?
- 1. The amount of myelination of a nerve fiber.
- 2. The diameter of the nerve fiber, the thicker the fiber, the faster the conduction.
Explain the speed of conduction and location of: Type A fibers, Type B fibers, and Type C fibers.
- 1. Type A fiber-Have a large diameter and abundant myelin. They are found in motor and sensory neurons, which provide a rapid respone to stimuli in the external environment.
- 2. Type B fiber-Have medium diameter and light myelination. slower than A. (internal organ function)
- 3. Type C Fibers- have a small diameter, and are unmyelinated. They are the slowest condcution rate. In autonomic nerve systerm (internal organ function)
Define synapse. How can a synapse be compared to a switch?
- 1. Synapse-is a junction where action potentials from one cell can produce action potentials in another cell.
- 2. They control mechanisms.
What is the correct sequence of structures in a synapse?
- 1. presynaptic Terminal
- 2. Synapse (synaptic cleft)
- 3. Postsynaptic membrane
What are the two types of synapses?
- 1. Electrical
- 2. Chemical
Explain electrical synapses and the association of connexons. Where are electrical synapses found and why are they found there?
- 1. They occur at gap junctions where connectors called connexons allow for movement of ions from cell to cell.
- 2. in Cardiac muscles and in many types of smooth muscle where coordianated movement is required.
In chemical synapse, how are the following structures defined: Presynaptic terminal, Synaptic cleft, Postsynaptic membrane.
- 1. Presynaptic Terminal- which is the end of an axon.
- 2. Synaptic Cleft- Which is a gap between the presynaptic terminal and the postsynaptic membrane.
- 3. Postsynaptic Membrane- which may be found on the dendrite of another neuron, on the outer membrane of a muscle cell, or on the outer membrane of a gland cell. They have receptors needed for neurotransmitter binding.
What are the 5 steps involved in the mechanics of a chemical synapse?
- 1. Action potential occurs.
- 2. Calcium channels open.
- 3. Calcium binds with synaptic vesicles.
- 4. Synaptic vesicles release a neurotransmitter into synaptic cleft.
- 5. Neurotransmitter binds with a receptor and opens sodium channels.
What are 2 consequences of the failure to destroy a neurotransmitter immediately?
- 1. Continual muscle contraction (tetany)
- 2. Continual gland secretion.
What happens to acetylcholine with it is brokend down?
- It turns to:
- 1. Choline- goes back into the rpesynaptic terminal and is used to make new acetylcholine.
- 2. Acetic acid- is used as a source of energy.
What happens to norepinephrine when it is destroyed?
Most of it is recycled
What is the relationship of amphetamine abuse and norepinephrine destruction?
It blocks the re-uptake and inhibit MAO. It causes increased alertness and wakefulness.
A specific neurotransmitter can stimulate some cells and inhibit others. What does this role-reveral depend on?
Depends on the receptor.
Excitatory Postsynaptic Potential-the neurotransmitter will allow for the opening of more sodium channels which causes an increased permeability to Na+. This would lead to depolarization, which would be excitatory.
Inhibitory Postsynaptic Potential-the neurotransmitter would cause hyperpolarization, either through increased K+ or Cl- membrane permeability. This leads to inhibition.
What is the purpose of neuromodulator?
can alter the amount of neurotranmitter released from the presynaptic terminal. (this is when an action potential reaches the presynaptic terminal.)
How do enkaphalins and endophins decrease the awareness of pain?
They block the Ca+2 channels, reduce the amount of neurotransmitter released and therefore decrease the awareness of pain.
Contrast spatial summation with temporal summation.
- 1. Spatial Summation-Occurs when two actin potentials arrive simultaneously from two different presynaptic terminals that synapse with the same postsynaptic membrane.
- 2. Temporal Summation-(temporal means time), occurs when two or more action potentials within the same nerve fiber arrive one behind the other at a presynaptic terminal and cross through the synapse to the postsynaptic membrane.
Contrast Convergent pathways with Divergent pathways.
- 1. Convergent Pathways-occurs when many neurons converge (combine) and synapse with a small number of neurons. (information comes to one point). The simplest convergent pathway is two presynaptic neurons synapsing with a single postsynaptic neuron.
- 2. Divergent Pathways-occurs when a small number of presynaptic neurons synapse with a large number of postsynaptic neurons. Divergent pathways allow infomration to diverge (spread out).
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