BIO 210 Chapter 10 + Rest of Chapter 11 Study Guide

IPSPs range from -70 mV to ____________________ mV.

-90 mV

EPSPs range from -70 mV to ____________________ mV.

0 mV

List and describe 3 different ways neurotransmitter is removed from the synapse.

1. Reuptake: astrocytes or the presynaptic terminal absorb the neurotransmitter and store it or destroy it with enzymes 2. Degradation: enzymes in the postsynaptic membrane or synaptic cleft break down the neurotransmitter 3. Diffusion: neurotransmitter diffuses away from the synapse

List and describe 3 specific functions of the nervous system.

1. Sensory input - sensory receptors monitor changes inside and outside of the body 2. Integration - sensory input is processed and interpreted, and the nervous system decides what should be done 3. Motor output - effectors are activated to cause a response

List 4 different types of effectors.

1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle 4. Gland

List the 2 divisions of the motor nervous system and name the effector(s) of each.

1. Somatic Nervous System - skeletal muscles 2. Autonomic Nervous System - cardiac muscles, smooth muscles, and glands

Name 2 types of ligand-gated ion channels that open, producing IPSPs. Describe flow of ions when these channels open.

K+ and Cl- ligand-gated ion channels K+ flows out of the cell and/or Cl- flows into the cell when these channels open

Do all neurons in the nervous system secrete the same neurotransmitter?

No

Name the type of neuroglial cell that forms the myelin sheath in the CNS.

Oligodendrocyte

Differentiate between sensory, motor, and interneurons.

Sensory (afferent): transmit impulses from sensory receptors in the skin, skeletal muscles, or internal organs toward or into the central nervous system; cell bodies of sensory neurons are found in ganglia outside the central nervous system Motor (efferent): transmit impulses away from the central nervous system to effectors (glands or muscles); cell bodies of motor neurons are located within gray matter of the central nervous system Interneurons: also called association neurons or internuncial neurons, transmit impulses from sensory to motor neurons or to other interneurons; located within the gray matter of the central nervous system

Give the structural classification of sensory neurons, motor neurons, and interneurons.

Sensory neurons: unipolar Motor neurons: multipolar Interneurons: multipolar

Define axon hillock.

The beginning of the axon where action potentials generate

List the 2 divisions of the nervous system and list the organs of each.

1. Central Nervous System (CNS) - brain and spinal cord 2. Peripheral Nervous System (PNS) - cranial nerves and spinal nerves

List 2 groups of peptides that function as neurotransmitters. Which group is generally inhibitory? Which group is generally excitatory?

1. Endorphins 2. Tachykinins Inhibitory: endorphins Excitatory: tachykinins

List 3 amino acids that function as neurotransmitters. Which produce IPSPs (inhibitory)? Which produces EPSPs (excitatory)? Identify in general where each neurotransmitter functions.

1. GABA (gamma aminobutyric acid) 2. Glutamate 3. Glycine IPSPs: GABA and glycine EPSPs: glutamate All function in the central nervous system

List 2 types of cells that are located in the nervous system. Which conducts impulses? Which provides support? Which type of cell is more plentiful?

1. Neuron - conducts impulses 2. Neuroglial cell - supports neurons, more plentiful

List 3 neurotransmitters that are classified as biogenic amines. Biogenic amines are derived from ____________________. Which of the 3 neurotransmitters listed produces effects are opposite to those produced by acetylcholine?

1. Norepinephrine 2. Dopamine 3. Serotonin Amino acids Norepinephrine

List the 2 divisions of the peripheral nervous system. Describe direction of impulse transmission in each. Which is afferent? Which is efferent?

1. Sensory Division - afferent, impulses travel to brain and spinal cord 2. Motor Division - efferent, impulses travel away from brain and spinal cord

Define peptide.

A chain of amino acids

Define graded potential. Compare graded potentials with action potentials.

A change in membrane potential that occurs in the dendrite of a postsynaptic neuron. Both graded potentials and action potentials are short-lived, are triggered by a stimulus that causes gated ion channels to open, and the flow of current to adjacent areas of the plasma membrane changes the membrane potential there as well for both. However, graded potentials have small amplitudes and can vary in amplitude (action potentials have large amplitudes and all action potentials are identical in amplitude). They are produced when ligand-gated ion channels open instead of voltage-gated ion channels, the change in membrane potential decreases with distance from the stimulus (action potentials do not decrease in magnitude), they are produced on the dendrites instead of the axon hillock, and they act as a signal over a very short distance vs. long distance. The magnitude and duration of graded potentials vary with the strength of the stimulus while all action potentials demonstrate the same magnitude and duration. Graded potentials exhibit either depolarization or hyperpolarization while action potentials always begin with a depolarization, followed by a repolarization, followed by a hyperpolarization, they can move away from the stimulus in any/all directions, they can be summated either temporally or spatially, and summated graded potentials can cause the axon hillock to generate an action potential (action potentials never produce graded potentials).

Differentiate between A fibers, B fibers, and C fibers. In which fiber are impulses transmitted most rapidly? In which fiber are impulses transmitted most slowly?

A fibers: largest diameter, thick myelin sheaths, conducts impulses fastest (up to 150 m/s) B fibers: intermediate diameter, lightly myelinated, conducts impulses at an average rate (15 m/s) C fibers: smallest diameter, unmyelinated, conducts impulses slowest (1 m/s or less)

Define absolute refractory period. Relate absolute refractory period to direction of impulse transmission.

A period during an action potential when another action potential cannot be generated, no matter how strong the stimulus. During impulse transmission, an action potential can only move in one direction (toward the axon terminal), because if it were to try to move backwards, it would encounter the absolute refractory period.

Differentiate between amino acids, biogenic amines, and peptides.

Amino acids: building blocks of proteins - some act as excitatory or inhibitory neurotransmitters Biogenic amines: molecules derived from amino acids that act as inhibitory or excitatory neurotransmitters Peptides: same thing as proteins (long chains of amino acids) - act as neurotransmitters

Identify the neuronal structure that must reach threshold in order for an action potential to be generated in the postsynaptic neuron.

Axon hillock

Which structural class of neuron is rare?

Bipolar

Does acetylcholine produce EPSPs, IPSPs, or both?

Both

List neuroglial cells that are located in the central nervous system and give their general functions; list neuroglial cells that are located in the peripheral nervous system and give their general functions.

CNS: 1. Astrocyte - physical support 2. Microglial cell - defensive 3. Ependymal cell 4. Oligodendrocyte - forms myelin sheath PNS: 1. Satellite cell - physical support 2. Schwann cell - forms myelin sheath

Name the neuronal structure in which the nucleus is located.

Cell body

Give the name for the rough endoplasmic reticulum of a neuron.

Chromatophilic substance or Nissl body

Differentiate between dendrites and axons. Which of these 2 structures is often more plentiful?

Dendrite: a branch-like structure that functions in receiving impulses. Neurons can have many dendrites (more plentiful). Axon: a structure that functions in conducting impulses. Neurons only have one axon, but at the end of the axon, there can be more than one axon terminal. At the end of each axon terminal is a synaptic end bulb.

Define depolarization and hyperpolarization. Explain why a depolarizing graded potential MAY excite the postsynaptic neuron. Explain why a hyperpolarizing graded potential inhibits the postsynaptic neuron.

Depolarization: when membrane potential becomes less negative Hyperpolarization: when membrane potential becomes more negative than resting A depolarizing graded potential may excite the postsynaptic neuron because it is making the membrane potential less negative, and if it changes the membrane potential of the axon hillock from -70mV to -55mV, and action potential will be generated (in other words the postsynaptic neuron is excited). A hyperpolarizing graded potential inhibits the postsynaptic neuron by making the membrane potential more negative - therefore making it impossible to generate an action potential.

Is there normally a higher concentration of Cl- in ECF or ICF?

ECF

Which graded potential (EPSP or IPSP) MAY cause the axon hillock to reach threshold?

EPSP

Classify an EPSP as depolarization or hyperpolarization. Do the same for IPSP.

EPSP: depolarization IPSP: hyperpolarization

Differentiate between excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs).

Excitatory postsynaptic potentials (EPSPs): depolarizing graded potentials that occur occur at excitatory postsynaptic membranes Inhibitory postsynaptic potentials (IPSPs): hyperpolarizing graded potentials that occur at inhibitory postsynaptic membranes

Give a general function of the nervous system.

Fast communication and control

Describe the concept of graded potentials being summated. Differentiate between temporal and spatial summation.

Graded potentials can be added together for a greater effect. Spatial: the graded potentials from more than one presynaptic neuron firing at the same time are added together Temporal: the graded potentials from the same presynaptic neuron firing multiple times are added together

Which graded potential (EPSP or IPSP) NEVER causes the action hillock to reach threshold?

IPSP

Describe how a membrane potential changes if cations flow in, if cations flow out, if anions flow in, and if anions flow out.

If cations flow in: membrane potential becomes less negative If cations flow out: membrane potential becomes more negative If anions flow in: membrane potential becomes more negative If anions flow out: membrane potential becomes less negative

Define all-or-none phenomenon.

If the axon hillock reaches -55mV, an action potential WILL be generated. If not, no action potential is generated. It either is generated (all) or it isn't (none).

Describe impulse transmission along an unmyelinated axon. This type of impulse transmission is called ____________________ conduction.

Impulses transmit all the way down the axon toward the axon terminal in increments. The action potential is generated in each section, all along the axon. Continuous

Give the general function of myelin.

Insulation - keeps ions from entering or exiting the axon

Differentiate between unipolar, bipolar and multipolar neurons (neuron structure).

Multipolar: 3 or more processes (more than one dendrite, only one axon) Bipolar: 2 processes (an axon and a dendrite) that extend from opposite sides of the neuron cell body Unipolar: single short process that branches to form an axonal end and a dendritic end

Differentiate between unmyelinated and myelinated axons.

Myelinated axons have Schwann cells or oligodendrocytes. Unmyelinated axons do not have Schwann cells or oligodendrocytes.

Name the type of ligand-gated ion channel that opens, producing an EPSP. Describe flow of ions when this channel opens.

Na+ ligand-gated ion channels (opened by a neurotransmitter) Na+ flows into the cell when these channels open.

Define neuronal pool. Differentiate between diverging circuits, converging circuits, reverberating circuits, and parallel after-discharge circuits.

Neuronal pool: When an impulse is conducted through a group of neurons, the group of neurons is called a neuronal pool. Diverging circuits: one input, many outputs, amplifying, example: a single neuron in the brain can activate 100 or more motor neurons in the spinal cord and thousands of skeletal muscle fibers. Converging circuits: many inputs, one output, concentrating, example: different sensory stimuli can all elicit the same memory Reverberating circuits: signal travels through a chain of neurons, each feeding back to previous neurons, oscillating, controls rhythmic activity, example: involved in breathing, sleep-wake cycle, and repetitive motor activities such as walking Parallel after-discharge circuits: signal stimulates neurons arranged in parallel arrays that eventually converge on a single output cell, impulses reach output cell at different times, causing a burst of impulses called an after-discharge, example: may be involved in exacting mental processes such as mathematical calculations

Differentiate between presynaptic and postsynaptic neuron.

Presynaptic: the neuron that transmits the impulse toward the synapse to the next neuron Postsynaptic: the neuron that receives the impulse from the first neuron and transmits the impulse away from the synapse

Which type of impulse conduction is faster?

Saltatory conduction

Name the type of neuroglial cell that forms the myelin sheath in the PNS.

Schwann cell

Describe the formation of the myelin sheath.

Schwann cells (in PNS) or oligodendrocytes (in PNS) wrap themselves around the axon of the neuron. As they wrap around, the cytoplasm is pushed upward and the layers of plasma membrane that wrap directly around the axon become the myelin sheath.

Name the most plentiful type of neuron based on structure. Name the most plentiful type of neuron based on function.

Structure: multipolar neurons Function: interneurons

Describe impulse transmission along a myelinated axon. This type of impulse transmission is called ____________________ conduction.

The action potential is only generated at the nodes of Ranvier, hopping from one to the other, skipping over the Schwann cells or oligodendrocytes. Saltatory

Describe neuron-to-neuron impulse transmission.

The action potential propagates down the axon of the presynaptic neuron to the axon terminal and synaptic end bulb. At the synaptic end bulb, Ca2+ voltage-gated ion channels open, and the influx of Ca2+ forces vesicles carrying neurotransmitters to migrate down, fuse with the plasma membrane, and release the neurotransmitters via exocytosis. The neurotransmitters then bind to receptors on the dendrite of the postsynaptic neuron, opening ligand-gated ion channels and creating a graded potential. The graded potential then moves in all directions, becoming weaker as it spreads. When several presynaptic neurons fire impulses toward the dendrite at the same time, or the same presynaptic neuron fires multiple impulses toward the dendrite, the graded potential becomes strong enough to generate an action potential at the axon hillock.

Describe the general components of the cell body.

The cell body contains most of the neuron's cytoplasm, the nucleus, and Nissl bodies (chromatophilic substances), which is the neuron's rough endoplasmic reticulum.

Describe what happens on the dendrite after neurotransmitter binds with receptors.

The graded potential moves in all directions, becoming weaker as it spreads. When several presynaptic neurons fire impulses toward the dendrite at the same time, or the same presynaptic neuron fires multiple impulses toward the dendrite, the graded potential becomes strong enough to generate an action potential at the axon hillock.

Define origin.

The immovable structure (bone) at the end of a skeletal muscle

Describe in general how diameter of an axon affects speed of impulse transmission.

The larger the diameter, the faster the transmission of the impulse. The smaller the diameter, the slower the transmission of the impulse.

Define insertion.

The movable structure (bone) at the other end of a skeletal muscle

Describe the location of the myelin in the myelin sheath.

The myelin is the innermost part of the myelin sheath where the layer of plasma membrane is directly in contact with the axon.

Describe the location of the nodes of Ranvier.

The nodes of Ranvier are gaps in the myelin sheath. They are located between the Schwann cells or oligodendrocytes.

Define synapse.

The space between two communicating neurons

Describe the function of sensory receptors.

To detect stimuli and to change stimuli into impulses

Identify where all interneurons are located.

Within gray matter of the central nervous system