Anatomy test 3 (Chapter 12)

which letter represent the outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath, is found only around axons in the PNS and aids in regeneration.

A the neurolemma

What letter represents cell body?

C

The various branched of the Nervous System/ how it is divided

Central Nervous System and Peripheal Nervous System

Function of the various branched of the Nervous System

Central Nervous System: Spinal Cord and Brain Peripheral Nervous System: Divison

What letter is C?

Cytoplasm

Unipolar

Dendrites and one axon that are fused together to form a contentious process that emerges from the cell body: The dendrites of most of these function as sensory receptors

What is represented by C?

Is the Axon

Repolarizing phase

the membrane potential is restored to the resting state of −70 mV.

Depolarizing phase

the negative membrane potential becomes less negative, reaches zero, and then becomes positive

Continous Conduction

· involves step-by-step depolarization and repolarization of each adjacent segment of the plasma membrane. · In continuous conduction, ions flow through their voltage-gated channels in each adjacent segment of the membrane. · Note that the action potential propagates only a relatively short distance in a few milliseconds. Continuous conduction occurs in unmyelinated axons and in muscle fibers.

Reverberating circuit

· the incoming impulse stimulates the first neuron, which stimulates the second, which stimulates the third, and so on. · Branches from later neurons synapse with earlier ones. · This arrangement sends impulses back through the circuit again and again. The output signal may last from a few seconds to many hours, depending on the number of synapses and the arrangement of neurons in the circuit.

Diverging circuit

· the nerve impulse from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit · For example, a small number of neurons in the brain that govern a particular body movement stimulate a much larger number of neurons in the spinal cord. · Sensory signals are also arranged in diverging circuits, allowing a sensory impulse to be relayed to several regions of the brain. This arrangement amplifies the signal.

Converging circuit

· the postsynaptic neuron receives nerve impulses from several different sources. · For example, a single motor neuron that synapses with skeletal muscle fibers at neuromuscular junctions receives input from several pathways that originate in different brain regions.

What is parasympathetic nervous system?

"Rest and digest" Blood pressure/heart rate decrease, digestive increases.

Voltage-gated Channels

-Description: Gated channels that open in response to voltage stimulus (change in membrane potential) -Location: Axons of all types of neurons

Leak Channels

-Description: Gated channels that randomly open and close -Location: Found in nearly all cells, include dendrites, cell bodies, and axons of all types of neurons

Know about the different types of neutral circuits

-Diverging circuit -Converging circuit -Reverberating circuit -Parallel after-discharge circuit

Know the different types of synapse

-Electrical synapse -Chemical synapse

Know about post synaptic potential, the difference between IPSP and EPSP

-Excitatory postsynaptic potentials (EPSP) -Inhibitory postsynaptic potentials (IPSP)

Understand summation of post synaptic potentials

-A single postsynaptic neuron receives input from many presynaptic neurons, some of which release excitatory neurotransmitters and some of which release inhibitory neurotransmitters. -The sum of all the excitatory and inhibitory effects at any given time determines the effect on the postsynaptic neuron, which may respond in the following ways: 1. EPSP. If the total excitatory effects are greater than the total inhibitory effects but less than the threshold level of stimulation, the result is an EPSP that does not reach threshold. • Following an EPSP, subsequent stimuli can more easily generate a nerve impulse through summation because the neuron is partially depolarized. Nerve impulse(s). If the total excitatory effects are greater than the total inhibitory effects and threshold is reached, one or more nerve impulses (action potentials) will be triggered. • Impulses continue to be generated as long as the EPSP is at or above the threshold level. IPSP. If the total inhibitory effects are greater than the excitatory effects, the membrane hyperpolarizes (IPSP). • The result is inhibition of the postsynaptic neuron and an inability to generate a nerve impulse.

Mechanically-gated Channels

-Description: Gated channels that open in response to a mechanical stimulus (such as touch, pressure, vibration, or tissue stretching) -Location: Dendrites of some sensory neurons such as touch receptors, pressure receptors, and some pain receptors

Ligand-gated Channels

-Description: Gated channels that open in response to binding of ligand (chemical) stimulus -Location: Dendrites of some sensory neurons such as pain receptors and dendrites and cell bodies of interneurons and motor neurons

Know the different types of ion channels in neurons

-Leak channels -Ligand-gated channels -Mechanically-gated channels -Voltage-gated channels

Spatial Summation

-Summation of postsynaptic potentials in response to stimuli that occur at different locations in the membrane of a postsynaptic cell at the same time. -For example, spatial summation results from the buildup of neurotransmitter released simultaneously by several presynaptic end bulbs

Temporal Summation

-Summation of postsynaptic potentials in response to stimuli that occur at the same location in the membrane of the postsynaptic cell but at different times. -For example, temporal summation results from buildup of neurotransmitter released by a single presynaptic end bulb two or more times in rapid succession

Understand summation and the two different types

-Summation: several presynaptic end bulbs release their neurotransmitter at about the same time; the combined effect may generate a nerve impulse due to summation · Summation may be spatial or temporal

After-hyperpolarizing phase

-the membrane potential temporarily becomes more negative than the resting level -occurs when the voltage-gated K+ channels remain open after the repolarizing phase ends

Know how neurotransmitters are removed from the synapse

1. Diffusion 2. Enzymatic degradation 3. Uptake into cells

What letter represents the dendrite?

A

Which letter represents the Schwann cell formed around the axon being the outermost layer?

A on Left

What is the letter A?

Axon

What letter represents the axon?

E

Which letter represents the myelin sheath consisting of up to 100 layers of Schwann sheath?

E

What letter represents the inner most portion of up to 100 layers of Schwann cell membrane?

G, Myelin sheath

What is B?

Node of Ranvier

What letter is B?

Nucleus

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin. Schwann cells begin to form myelin sheaths around axons during fetal development

What is represented by D?

The formation of Nucleus and Cytoplasm forming in the Schwann cell process and wrapping around the axon

Ganglion

a collection of neuron cell bodies outside the CNS

What is the peripheral nervous system?

all nervous tissue not in the CNS

What is Action Potentials(AP)?

allow communication over short and long distances

What is Graded Potential(GP)?

allow communication over short distances only

What is Membrane Potential?

an electrical potential difference (voltage) across the membrane. In excitable cells this voltage is called resting membrane potential

Axon

conducts nerve impulses from the neuron to the dendrites or cell body of another neuron or to an effector organ of the body (usually only one of these)

Cell body

contains a nucleus, lysosomes, mitochondria, a Golgi complex, cytoplasmic inclusions such as lipofuscin, chromatophilic substances, and neurofibrils

what does the motor division do?

conveys output from the CNS to the effectors (muscles and glands)

What does the somatic nervous system do of the PNS?

conveys output from the CNS to the skeletal system(voluntary)

What does the autonomic nervous system do?

conveys output of from the CNS of the smooth muscle, cardiac muscle and glands(involuntary)

What is your sensory division of the PNS?

coveys input into the CNS from sensory receptors in the body; somatic sense and special sense

which term means the graded potentials die out as they spread along the membrane?

decremental conduction

What is the sympathetic nervous system(of PNS)?

fight or flight

What is the Enteric nervous system(of PNS)?

helps regulate the activity of smooth muscle and glands of the GI tract

Know about graded potentials and what it is?

is a small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative) A graded potential is a small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative)

What are considered somatic senses?

tactile, thermal, pain, sensations of the skeletal muscle

Bipolar

one dendrite and one axon; Found in the retina of the eye, the inner ear, and olfactory area of the brain

what two systems are motor output of the PNS and regulate the smooth muscle, cardiac muscle, and glands?

parasympathetic and sympathetic nervous system

What are the two divisions in the PNS?

sensory (afferent) and motor (efferent)

Dendrites

receiving/input portions of the neurons (there are many of these)

Multipolar

several dendrites and one axon; Most neurons in the brain and spinal cord and all motor neurons

What are considered special senses?

smell, taste, vision, hearing, equilibrium

What are the two nervous systems of the PNS under the motor division?

somatic and autonomic

What are the parts of the autonomic nervous system of the PNS?

sympathetic nervous system, parasympathetic nervous system, and Enteric nervous system

What is depolarizing grading potential?

when the response makes the membrane less polarized (inside less negative)

What is a hyperpolarizing graded potential?

when the response makes the membrane more polarized (inside more negative)

Know the factors that can contribute to the resting membrane potential

~The membrane of a non-conducting neuron is positive outside and negative inside. This is determined by: ~Unequal distribution of ions across the plasma membrane and the selective permeability of the neuron's membrane to N a+ and K+ ~Most anions cannot leave the cell · Most anions inside the cell cannot leave freely (unlike K+) because they are attached to non-diffusible molecules such as ATP and large proteins ~N a+/K+ pumps (Na+/K+ ATPase) · Na+/K+ ATPase expels 3 Na+ for every 2 K+ imported. Since this pump removes more positive charges from the cell than it can bring in the pump is electrogenic- contributes to the negative resting membrane potential

Excitatory postsynaptic potentials (EPSP)

· A depolarizing postsynaptic potential · Opening of Na+ channels

Inhibitory postsynaptic potentials (IPSP)

· A hyperpolarizing postsynaptic potential · Opening of Cl- or K+ channels

Damage and Repair to the PNC

· About 24 to 48 hours after injury the Nissl bodies break up into fine granular masses. This alteration is called chromatolysis. · By the third to fifth day, the part of the axon distal to the damaged region becomes slightly swollen and then breaks up into fragments; the myelin sheath also deteriorates but the neurolemma remains. Degeneration of the distal portion of the axon and myelin sheath is called Wallerian degeneration. · Macrophages phagocytize the debris. Synthesis of RNA and protein accelerates, which favors rebuilding or regeneration of the axon. · The Schwann cells on either side of the injured site multiply by mitosis, grow toward each other, and may form a regeneration tube across the injured area. The tube guides growth of a new axon from the proximal area across the injured area into the distal area previously occupied by the original axon. · New axons cannot grow if the gap at the site of injury is too large or if the gap becomes filled with collagen fibers.

Know about regeneration and repair of nervous tissue and the steps involved

· Although the nervous system exhibits plasticity, neurons have a limited ability to regenerate themselves · In the CNS, there is little or no repair due to: ~Inhibitory influences from neuroglia, particularly oligodendrocytes ~Absence of growth-stimulating cues that were present during fetal development ~Rapid formation of scar tissue · In the PNS repair is possible if the cell body is intact, Schwann cells are functional, and scar tissue formation does not occur too rapidly · Steps involved in the repair process are: ~Chromatolysis ~Wallerian degeneration ~Formation of a regeneration tube

Know about action potentials, and their various phases

· An action potential (AP) or impulse is a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state. · Phases: -Depolarizing phase -Repolarizing phase -After-hyperpolarizing phase

Know the parts of the neuron

· Cell body ·Dendrites · Axon · Ganglion

Know the different types of electrical signals in neurons and how they differ

· Excitable cells communicate with each other via action potentials or graded potentials · Production of an AP or a GP depends upon the existence of a resting membrane potential and the existence of certain ion channels

Know about the inhibitory neurotransmitter GABA

· Gamma-aminobutyric acid (GABA) is an important inhibitory neurotransmitter. At many synapses, the binding of GABA to ionotropic receptors opens Cl− channels. · GABA is found only in the CNS, where it is the most common inhibitory neurotransmitter. · Antianxiety drugs such as diazepam (Valium®) enhance the action of GABA

Electrical synapse

· Gap junctions connect cells and allow the transfer of information to synchronize the activity of a group of cells

CNS

· In the CNS, an oligodendrocyte myelinates parts of several axons. · Each oligodendrocyte puts forth about 15 broad, flat processes that spiral around CNS axons, forming a myelin sheath. · A neurolemma is not present, because the oligodendrocyte cell body and nucleus do not envelop the axon. · Nodes of Ranvier are present, but they are fewer in number. · Axons in the CNS display little regrowth after injury. This is thought to be due, in part, to the absence of a neurolemma, and in part to an inhibitory influence exerted by the oligodendrocytes on axon regrowth.

Know the structural classification of neurons

· Multipolar · Bipolar · Unipolar

Know the structures of the neurotransmitter receptors and how they different

· Neurotransmitters at chemical synapses cause either an excitatory or inhibitory graded potential · Neurotransmitter receptors have two structures -Ionotropic receptors- receptor that contains a neurotransmitter binding site and an ion channel -Metabotropic receptors- receptor that contains a neurotransmitter binding site but No ion channel

Chemical synapse

· One-way transfer of information from a presynaptic neuron to a postsynaptic neuron

PNS function, general characteristics, and types

· Schwann cells begin to form myelin sheaths around axons during fetal development. · Each Schwann cell wraps about 1 mm of a single axon's length by spiraling many times around the axon. · Eventually, multiple layers of glial plasma membrane surround the axon, with the Schwann cell's cytoplasm and nucleus forming the outermost layer. · The inner portion, consisting of up to 100 layers of Schwann cell membrane, is the myelin sheath. · The outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath, is the neurolemma which is found only around axons in the PNS. · When an axon is injured, the neurolemma aids regeneration by forming a regeneration tube that guides and stimulates regrowth of the axon.

General functions of the Nervous System

· Sensory (input): Sense changes in the internal and external environment through sensory receptors; Sensory Neurons · Integrative (processing): Analyze incoming sensory information, store some aspects, and make decisions regarding appropriate behaviors; Integration (inter/association neurons) · Motor (output): Respond to stimuli by initiating action by activating effectors through the cranial and spinal nerves; Motor Neurons

Understand the refractory period and what causes it

· The period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus · The relative refractory period is the period of time during which a second action potential can be initiated, but only by a larger-than-normal stimulus. · It coincides with the period when the voltage-gated K+ channels are still open after inactivated Na+ channels have returned to their resting state · In contrast to action potentials, graded potentials do not exhibit a refractory period

Know what causes the resting membrane potential and what voltage it is usually at

· The resting membrane potential exists because of a small buildup of negative ions in the cytosol along the inside of the membrane, and an equal buildup of positive ions in the extracellular fluid (ECF) along the outside surface of the membrane · Such a separation of positive and negative electrical charges is a form of potential energy, which is measured in volts or millivolts · In neurons, the resting membrane potential ranges from −40 to −90 mV. A typical value is −70 mV. · A cell that exhibits a membrane potential is said to be polarized.

Know about stimulus strength

· They are larger or smaller depending on how many ligand-gated or mechanically-gated channels have opened or closed and how long each remains open. · Because they die out within a few millimeters of their point of origin, graded potentials are useful for short-distance communication only

Parallel after-discharge circuit

· a single presynaptic cell stimulates a group of neurons, each of which synapses with a common postsynaptic cell. · A differing number of synapses between the first and last neurons imposes varying synaptic delays, so that the last neuron exhibits multiple EPSPs or IPSPs. · If the input is excitatory, the postsynaptic neuron then can send out a stream of impulses in quick succession. Parallel after-discharge circuits may be involved in precise activities such as mathematical calculations.

Saltatory Conduction

· the special mode of action potential propagation that occurs along myelinated axons, occurs because of the uneven distribution of voltage-gated channels. · When an action potential propagates along a myelinated axon, an electric current (carried by ions) flows through the extracellular fluid surrounding the myelin sheath and through the cytosol from one node to the next. · The action potential at the first node generates ionic currents in the cytosol and extracellular fluid that depolarize the membrane to threshold, opening voltage-gated Na+ channels at the second node. · The resulting ionic flow through the opened channels constitutes an action potential at the second node. · Then, the action potential at the second node generates an ionic current that opens voltage-gated Na+ channels at the third node, and so on. Each node repolarizes after it depolarizes.

2 types of cells that make up nervous system

•Neurons- provide most of the unique functions of the nervous system •Neuroglia- support, nourish, and protect neurons