Chapter 10

Explain the difference between the central nervous system (CNS) and the peripheral nervous system (PNS).

CNS = brain and spinal cord, signals are integrated, create sensations, add to memory, help produce thoughts; PNS = somatic nervous system communicated voluntary (conscious) --> contraction; autonomic nervous system controls viscera (heart and glands)

Diffusion of which of the following ions into the synaptic knob triggers the release of neurotransmitter?

Ca-2

Explain how malfunctioning neuroglia can harm health.

Neuroglia that produce toxins may lie behind some neurodegenerative disorders.

Explain what determines the output of a neuronal pool in terms of input neurons, excitation, and inhibition.

Neuronal pools receive input from neurons, and each pool generates output. Neuronal pools may have excitatory or inhibitory effects on other pools or on peripheral effectors.

Distinguish between neurons and neuroglia.

Neurons - react to physical and chemical changes in their surroundings; contains dendrites and axons Neuroglia - outnumber neurons, fill space and support neurons

Explain how information is passed from a presynaptic neuron to a postsynaptic cell.

Synaptic transmission is carried out by neurotransmitters. Impulse travels along axon of presynaptic neuron to axon terminal. When an impulse reaches a synaptic knob, voltage-sensitive calcium channels open and calcium diffuses inward. Increased calcium initiates events that fuse synaptic vesicles --> release of neurotransmitter-->binds to receptor of postsynaptic cell

Explain why the "trigger zone" of a neuron is named as such.

The initial segment of the axon in a multipolar neuron is called this because it contains many voltage-gated sodium channels. When threshold is reached, they open for instant, increasing permeability (sodium ions diffuse) --> changes from resting potential to positive (depolarization)

Explain how enzymes within synaptic clefts and reuptake of neurotransmitter prevents continuous stimulation of the postsynaptic cell.

To keep signal duration short, enzymes in synaptic clefts and on postsynaptic membranes rapidly decompose some neurotransmitters.

Distinguish between excitatory and inhibitory postsynaptic potentials.

excitatory = neurotransmitter binds to postsynaptic receptor and opens sodium ion channels, ions diffuse inwardly, depolarizing membrane, possibly triggering action potential inhibitory = different neurotransmitter binds to other receptors and increases membrane permeability to potassium ions, these ions diffuse outward, hyper polarizing member, action potential is less likely

Explain how Schwann cells encase large axons, including the formation of myelin, the neurilemma, and the nodes of Ranvier.

formation of myelin - several types of lipids and proteins neurilemma - surrounds myelin sheath node of Ranvier - narrow gaps in the myelin sheath between Schwann cells

Distinguish between polarized, hyperpolarized, and depolarized.

hyperpolarized = membrane potential is more negative than the resting potential depolarized = membrane potential becomes less negative than resting potential

Distinguish between convergence and divergence.

convergence = axons from different parts of N.S. lead to same neuron,allows nervous system to collect, process, and respond to information divergence = impulses from one neuron branch to several other neurons

Explain how an injured neuron may regenerate.

damaged peripheral neuron may regenerate, proximal end of injured axon develops sprouts shortly after injury, neuroglia produces growth factors, Schwann cells regenerate myelin sheath

List in correct order the changes that occur during an action potential.

initial segment --> reaches threshold and opens sodiums channels --> sodium ions diffuse and increase membrane potential to positive --> sodium channels close and potassium channels open--> increase potassium --> membrane is negatively charged-->repolarized-->potassium channels close

Distinguish a sensory receptor from an effector.

sensory receptor = found in PNS at the end of neurons and provide sensory function of the nervous system effector = CNS, responsive structures, carry out motor functions of the nervous system

Distinguish between the types of activities that the somatic and autonomic nervous systems control.

somatic nervous system - voluntary, conscious instructions originating in the CNS to skeletal muscles, causing contraction autonomic nervous system - communicates instructions from the CNS that control viscera (heart and various glands) = involuntary

Define resting potential.

stored electrical energy due to the difference in electrical charge between the inside and outside of an undisturbed nerve cell membrane.

Define facilitation.

subthreshold stimulation of a neuron that increases responsiveness to further stimulation.

Describe the neuroglia of the PNS.

1) Schwann cells produce the myelin on peripheral myelinated neurons 2) Satellite cells support clusters of neuron cell bodies called ganglia, in PNS

What do Schwann cells and oligodendrocytes have in common, and how do they differ?

Both Schwann cells and oligodendrocytes create myelin . However, oligodendrocytes are produced in the CNS while Schwann cells are produced in the PNS.

27. Define refractory period.

Brief period during the passage of an impulse where the axon becomes unresponsive to normal threshold stimulus

Explain the relationship between an action potential and impulse conduction down an axon.

An action potential at the trigger zone causes an electric current to flow a short distance down the axon, which stimulated the adjacent membrane to reach its threshold level, triggering another action potential--> electrical current

Describe the neuroglia of the CNS.

1) astrocytes - star-shaped cells, between neurons and blood vessels, provide support and hold structures together with abundant cellular processes 2) oligodendrocytes - smaller than astrocytes, fewer processes, send out number of processes, myelinated axons 3) microglia - small cells, few processes, help support neurons and phagocytize bacterial cells and cellular debris 4) ependyma - cuboidal or columnar, inner lining of central canal

Name and describe the part of a neuron.

1) dendrites = highly branched, multiple processes that may have spines 2) chromatophilic substance = rough ER 3) axon = conducts impulses 4) cell body = part of neuron from which axon and dendrites extend 5) neurofibrils = find threads in an axon

Describe the three types of neurons classified on the basis of structure.

1) multipolar neuron = one axon, rest of dendrites; mostly in brain and spinal cord 2) bipolar neuron = two processes ( 1 axon and 1 dendrite), specialized parts (eyes, nose, ears) 3) unipolar neuron = single process, two branches

13. Describe the three types of neurons classified on the basis of function.

1) sensory = afferent, conduct impulses from peripheral body parts into brain or spinal cord 2) interneurons = lie within spinal cord/brain, relay information from one part of the brain or spinal cord to another 3) motor = efferent, multipolar, conduct impulses out of the brain or spinal cord to effector

List six functions of neuroglia.

1. Structural support 2. Transport of substances 3. Communication between neurons 4. Induce synapse formation 5. Speed neurotransmission 6. Phagocytosis

5. List three general functions of the nervous system.

1.) receiving information 2.) deciding what to do 3.) acting on those decisions sensory, integrative, and motor

Describe the structure of a neuron.

Neurons have four regions: -cell body: containing the nucleus -dendrites: treelike features that extend from the cell body and contain receptors -axon: long slender extension of the cell body responsible for conducting the action potential to the axon terminals -axon terminals: bulbous structures at the end of the axon where neurotransmitters are stored in vesicles

Describe how the nervous system detects change associated with the body and reacts to that change to maintain homeostasis.

Neurons react to physical and chemical changes in their surroundings. Dendrites receive input --> axon carries information through impulses

Explain the importance of the nodes of Ranvier and conduction in myelinated fibers as opposed to conduction in unmyelinated fibers.

Nodes of Ranvier interrupt the sheath - here, axon membrane has channels for sodium and potassium ions that open during threshold depolarization --> action potential and impulse skip from node to node action potentials only occur in nodes (saltatory conduction)

Distinguish between myelinated and unmyelinated axons.

myelinated (gray) = have myelin sheaths, appear white, masses of myelinated = white matter in brain and spinal cord unmyelinated (white) = do not have myelin sheaths, appear gray (gray matter)

The ______ ________ brings the impulse to the synapse, whereas the ______ ________ on the other side of the synapse is stimulated of inhibited as a result of the synaptic transmission.

presynaptic neuron postsynaptic neuron