Baumagarner 11

neuropeptides

are a group of neurotransmitters that have a wide variety of functions within the nervous system, such as substance P, opioids, and neuropeptide Y.

Iontopic receptors

are found as components of a ligand-gated ion channels. These receptors directly control the movement of ions into or of the neuron when they bind to neurotransmitter

metabotropic receptors

are found within the plasma membrane associated with a separate ion channel. These receptors are directly connected to metabolic processes that are initiated when neurotransmitter binds G-proteins, intracellular enzymes associated with many metabotropic receptors, activate a cascade of reactions that ultimately form second messengers such as cAMP (cyclic adenosine monophosphate).

Dentrites

are short, branched processes that receive input from other neurons which they transmit to toward the cell body in the form of electrical impulses. Each neuron may have multiple

electrochemical gradient

diffusion of an ion across the plasma membrane is determined by both its concentration and electrical gradients

anon

each neuron only has one. nerve fiber that can generate and conduct action potentials. may have these distinct regions, axon hillock , telodendria, axon terminals or synaptic bulbs and axolemma

Principals of electrophysiology

electrical changes across neuron plasma membranes rely on ion channels and resting membrane potential

pseudounipolar neurons

eventually have only one fused axon that extends from the cell body that divides into two processes. These are sensory neurons that carry information related to pain, touch, and pressure.

Local and Action Potentials Compared

graded local potentials produce variable changes in membrane potentials while actions potentials cause a maximum depolarization to +30 mV.

neuronal pools

groups of interneurons within the CNS

multipolar neurons

have single axon and multiple dendrites

voltage gated sodium channels

have two gates an activation gate and an inactivation gate, with the three states, resting, activated and inactivated

effectors

organs that carry out the effects of the nervous system

what charge does the typical neuron have as a resting membrane potential

-70mV

What are the two forms of electrical changes that occur in neurons

1. local potentials that travel short distances 2. action potentials that travel the enitre length of an axon

Introduction to electrophysiology of neurons

1.All neurons are excitable or responsive in the presence of various stimuli: chemical signals, local electrical signals, and mechanical deformation. 2.Stimuli generate electrical changes across the neuron plasma membrane that is rapidly conducted (conductivity) along the entire length of the membrane.

are the events at the chemical synapse

1.An action potential in the presynaptic neuron triggers calcium ion channels in the axon terminal to open. 2.Influx of calcium ions causes synaptic vesicles to release neurotransmitter into the synaptic cleft. 3.Neurotransmitters bind to receptors on the postsynaptic neuron. 4.Ion channels open, leading to a local potential and possibly an action potential if threshold is reached.

generation of the resting membrane potential relies on the following factors that work together

1.Ion concentration gradients favor the diffusion of potassium ions out of the cell through leak channels and sodium ions into the cell. 2.The cytosol loses more positive charges than it gains and the membrane potential becomes more negative until it reaches the resting membrane potential.

events if propagation of an action

1.The axolemma depolarizes to threshold due to local potentials. 2.As sodium ion channels activate, an action potential is triggered and spreads positive charges down the axon. 3.The next section of axolemma depolarizes to threshold and fires an action potential as the previous section goes into repolarizes. 4.The current continues to move down the axon as the process repeats itself until the signal reaches the axon terminals.

Events are possible depending on which channels are opened

1.The membrane potential of the postsynaptic neuron moves closer to threshold caused by a small local depolarization (sodium or calcium ion channels open) called an excitatory postsynaptic potential (EPSP) 2.The membrane potential of the postsynaptic neuron moves further away from threshold caused by a small local hyperpolarization (potassium or chloride ion channels open) called an inhibitory postsynaptic potential (IPSP).

how many pairs of cranial nerves travle back to or from the brain

12

how many pairs of spinal nerves travel back to or from the spinal cord

31

action potential 3 steps

A local potential must be able to depolarize the axon strongly enough to reach a level called threshold usually -55mV. Once threshold is reached, voltage-gated sodium channels activate and sodium ions are able to flow into the axon causing it to depolarize. Sodium ion channels inactivate and voltage-gated potassium ion channels activate: sodium ions stop flowing into the axon and potassium begins exiting the axon as repolarization begins. The axolemma may hyperpolarize before potassium ion channels return to the resting state; after this the axolemma returns to its resting membrane potentia

Propagation action potentials

An action potential must be conducted or propagated along the entire length of the axon to serve as a long distance signaling service

central nervous system

CNS includes brain, protected by skull spinal cord which begins at foramen magnum and continues through the vertebral formina of the first cervical to the first or second lumbar vertebra

what happens to the membrane potential during the repolarization phase

Membrane potential returns to a negative value.

what effect does myelin have on the speed of action potential conduction

Mylin increases the of action potential conduction

Events at a Chemical Synapse.

Neuronal synapses are more complicated than the neuromuscular junction. There are multiple neurons secreting many different types of excitatory or inhibitory neurotransmitters.

what are the gaps in the myelin sheath called

Nodes of Ranvier

peripheral nervous system

PNS consits of all the nerves which are bundles of axons, blood vessels and connevctive tissues. In the body outside the protection of the skull and vertebral column

major neurotransmitters

Regardless of the receptor-type that it binds, neurotransmitters lead to either an EPSP and have excitatory effects or an IPSP and have inhibitory effects. Most can have both effects depending on which postsynaptic neuron receptors they bind

Biogenic amines ( monoamines)

are a class of five neurotransmitters synthesized from amino acids. They are used throughout the CNS and PNS for functions such as regulation of homeostasis and cognition.

Describe the all-or-none principle.

The all-or-none principle refers to an event, an action potential, which either happens completely or does not occur at all.

what happens to the membrane potential during the depolarization phase

The membrane potential rises toward zero and becomes positive briefly.

amino acid neurotransmitters

The three main amino acid neurotransmitters are: glutamate, -aminobutyric acid or GABA, and glycine.

what is the diffrence between white matter and gray matter

White matter in the brain and spinal cord is composed of myelinated axons that appear white. Gray matter in the brain and spinal cord is composed of neuron cell bodies, unmyelinated dendrites and axons that appear gray.

states of voltage gated channels

allow ions to move and change the membrane potential of the neuron. The movement of potassium ions are responsible for repolarization

opening a gated channel in the plasma membrane

alters the membrane potential as it changes the ions ability to move across the plasma membrane

integrative functions

analyze and interperet incoming sensory info and determine and appropriate response

motor functions

are the actions performed in responce to integration. is performed by the motor or efferent divisions of the PNS which can be further subdivided into somatic and autonomic divisions, based on the organs that the neurons contact

Neurons

are the excitable cells responsible for sending and receiving signals in the form of action potentials. 3 parts cell body ( soma ), dendrites, axon

Postynaptic potentials

are the local potentials found in the membranes of the postsynaptic neuron which can move the membrane closer to or further away from threshol

How is depolarization accomplished?

by opening sodium ion channels which allows postively charged ions to flow into the cell. the cell becomes more positive

neuronal synapses

can occur between the axon of one neuron and another part of another neuron

Motor or efferent neurons

carry information away from cell body in CNS to muscles and glands

Myelin sheath

composed of repeating layers of the plasma membrane of the Schwann cell (PNS) or Oligodendrocytes (CNS)

somatic sensory division

consists of neurons that cary signals from skeletal muscles bones joints and skin. also transmits signals form the organs of vision, hearing taste smell balance so is sometimes called special sensory divison

visceral sensory division

consits of neurons that transmit signals from viscera (organs) such as heart, lungs, stomach, kidneys, urinary bladder

nervous system

controls our perception and experience directs voluntary movement, seat of our consciouness, personality, learning, memmory. relgulates many aspects of homeostasis, along with endocrine system, respiratory rate, blood ph and pressure, body temp and sleep wake cycle

an action potential will only be generated

if threshold is reached which means that the sum of the EPSPs must be enough to overcome the sum of the IPSPs

sensory or afferent neurons

in the PNS carry information from sensory receptors towards the central nervous system

sensory functions

involve gathering info about the internal and external enviroments of the body. input is gathered by the sensory or afferent division of the PNS which is further divided into somatic and visceral sensory divisions input from both divisons is carried from sensory receptors to the spinal cord and/or brain by spinal and crianal nerves

spatial summation

involves the simultaneous release of neurotransmitter from the axon terminals of presynaptic neurons present

Ion channels and gradients

ions must rely on specific protein channels such as leak channels, gated channels, ligand-gated channels, voltage-gated channels, and mechanically-gated channels.

Acetylcholine (ACh)

is a neurotransmitter widely used by the nervous system. It is largely excitatory but does exhibit some inhibitory effects in the PNS. ACh is quickly degraded by acetylcholinesterase (AChE), an enzyme in the synaptic cleft.

neural integration

is a process where the postsynaptic neuron integrates all the incoming info both inhibitory and excitatory into a single effect

action potential

is a uniform, rapid depolarization and repolarization of the membrane potential of a cell. are only generated in trigger zones that include the axolemma, axon hillock and the initial segment of the axon (

temporal summation

is created by repeated neurotransmitter release from a single presynaptic neuron

how is resting membrane potential generated

is generated by the unequal distribution of ions and their differing abilities for crossing the plasma membrane.

membrane potential

is the electrical potential across the cell membrane that is a source of potential energy for the cell

cell body ( soma)

is the most metabolically active region of the neuron. It manufactures all the proteins needed for the neuron and houses many organelles.

resting membrane potential

is the negatively charge voltage that is present when a cell is at rest

what is the function of the presynaptic neuron

is the neruon sending the message from its axon terminals

what is the function of the postsynaptic neuron

is the neuron receiving the message from the presynaptic neuron at its cell body, axon, or dendrites; it has neurotransmitter receptors.

how does myelination occur

is the process that forms the myelin sheath from the plasma membranes of the neuroglial cell that surrounds the axon

Conduction speed

is the rate of propagation that is influenced by both axon diameter an the presence or absence of myelination

where is the synaptic cleft located

is the small ECF filled space that separates the presynaptic and postsynaptic neurons

synaptic transmission

is the transfer of chemical or electrical signals between neurons at a synapse

repolarzation

is where the cell returns to the resting membrane potential

What is voltage and how is it established

it is an electrical gradient established by the separation of charges between two locations. In this case across the plasma membrane

Chemical synapses

make up the majority of synapses in the nervous system. Convert electrical signals into chemical signals so no signal strength is lost at the case at electrical snyapses

Hyperpolarization phase

membrane potential temporarily becomes more negative than resting membrane potential

catecholamine subgroup

mostly excitatory. norepinephine epinephrine and doapmine

electrical synapses

occurs between cells that are electrically coupled via gap junctions

How is repolarization accomplished?

occurs by opening potassuim ion channels that allows positively charged ions to flow out of the cell. The cell becomes more negative

Describe saltatory conduction

occurs in myelinated axons where the insulating properties of the myelin sheath increase the efficiency and speed of signal conduction. Action potentials only depolarize the nodes of Ranvier and jump over the internodes

Describe continuous conduction.

occurs in unmyelinated axons where every section of axolemma from the trigger zone to the axon terminal must propagate the action potential. This slows conduction speed as each successive section of axon must depolarize continuously.

How is hyperpolarization accomplished

occurs when the cell becomes more negative than its normal resting membrane potential due to loss of potassium ions ( cations) plus loss of anions such as chloride

neural circuits

patterns of synaptic connection between neuronal pools

refractory period

period of time after a neuron has a neuron already generated an action potential, when the neuron cannot be stimulated to generate another action potental

Summation

phenomenon whereby all input from several postsynaptic potentials are added ( EPSPs+ IPSPs) together to affect the membrane potential at the trigger zone

Neuroglia or neuroglical cells

provide structural support and protection for neurons but also maintain their enviroment. Astrocytes oligodendrocytes microglia and ependymal cells reside within the CNs while the Schwann cells and satellite cells reside in the PNS

3 main functional regions of neuron

receptive, conduction and secretory

Interneurons or association neurons

relay info within the CNS between sensory and motor neurons and make up most of the neurons in the body

Regeneration of Nervous tissue

replacement of damaged tissue is nearly non existent in the CNS and limited in the PNS. neural tissue can regenerate only if the cell body remains intact

voltage gated potassium channels

resting (closed) activated ( open)

local potentials are

reversible, when the stimulus ends the neuron returns to resting membrane potential action potentials are irreversible once threshold is reached all-or-none

an action potential is

self propagating and travles in one direction

Tasks of the nervous system

sensory integrative motor

involved in brain functions

serotonin and histamine

Depolarization

the membrane potential becomes more postive due to the influx of postive charges across the plasma membrane

if the sum of the IPSPs is greater than EPSPs then

threshold will not be reached. an action potental will not be generated

neurotransmitter receptors

type of receptor a neurotransmitter binds to on the postsynaptic membrane determines the response

when is a cell polarized

when the voltage difference across the plasma membrane does not equal 0mV

synapse

where the neuron meets its target cell. can be either electrical or chemical

bipolar neurons

with one axon and one dendrite with a cell body between them, are found in the eye and the olfactory epithelium in the nasal cavity.