Nervous system pt 2

How does Increase in concentration of K+ in extracellular fluid affect impulse conduction

Reduces gradient for K+ to leave cell; threshold potential reached with stimulus of lower intensity; leads to excitable neurons, perhaps convulsions

How does Decrease in concentration of K+ in extracellular fluid affect impulse conduction

Neurons can become hyperpolarized; action potentials are not generated; lack of impulses leads to muscle paralysis

How does Decrease in permeability to K+ ion affect impulse conduction

Can be caused by some anesthetic drugs; stops impulses from passing through tissue fluid around axon; impulses do not reach brain, and there is no perception of touch and pain

Synapse

A site at which a neuron transmits a nerve impulse to another neuron

Synaptic Transmission

One-way process, using neurotransmitters, by which presynaptic neuron send impulse to postsynaptic neuron

Excitatory neurotransmitters

increase permeability to Na+ ions, bring membrane closer to threshold; increase likelihood of generating impulses

Inhibitory neurotransmitters

move membrane farther from threshold, decrease likelihood of generating impulses

Excitatory postsynaptic potential EPSP

Membrane change in which neurotransmitter opens Na+ Channels; Depolarizes membrane of postsynaptic neuron, as Na+ enters axon; Action potential in postsynaptic neuron becomes more likely

Inhibitory postsynaptic potential IPSP

Membrane change in which neurotransmitter opens K+ channels (or Cl- channels). Hyperpolarizes membrane of postsynaptic neuron, as K+ leaves axon. Action potential of postsynaptic neuron becomes less likely

Summation

the process by which multiple signals are integrated to determine whether a neuron will fire an action potential

Neurons don’t just receive one signal at a time, they receive thousands which the neuron must ____ to decide if ____________

combine; an action potential is fired

Neurotransmitters

monoamines, amino acids, and peptide produced in the rough ER or cytoplasm, that are released by exocytosis when an impulse reaches the synaptic knob of an axon

Vesicle trafficking

the process of membrane recycling. Synaptic vesicle becomes part of cell membrane as it releases neurotransmitter. Endocytosis returns membrane to cytoplasm; forms new vesicles

Acetylcholine in CNS

A neurotransmitter that controls skeletal muscle actions

Acetylcholine in PNS

A neurotransmitter Stimulates skeletal muscle contraction at neuromuscular junctions; may excite or inhibit at autonomic nervous system synapses

Norepinephrine in CNS

Creates a sense of well-being; low levels may lead to depression

Norepinephrine in PNS

May excite or inhibit autonomic nervous system actions, depending on receptors

Dopamine in CNS

Creates a sense of well-being; deficiency in some brain areas associated with Parkinson disease

Dopamine in PNS

Limited actions in autonomic nervous system; may excite or inhibit, depending on receptors

Serotonin in CNS

Primarily inhibitory; leads to sleepiness; action is blocked by LSD, enhanced by selective serotonin reuptake inhibitor antidepressant drugs

Histamine in CNS

Release in hypothalamus promotes alertness

GABA and glycine in CNS

An Amino acid found in CNS that is generally inhibitory

Glutamate

An Amino acid that is the most abundant excitatory neurotransmitter in the CNS

Enkephalins and Endorphins

A neuropeptides in the CNS that is generally inhibitory; reduce pain by inhibiting substance P release

Substance P

A neuropeptides in the PNS that is excitatory; pain perception

Nitric oxide in CNS

A gas that may play a role in memory

Nitric oxide in PNS

responsible for vasodilation

Clinical depression

Condition that causes debilitating, inexplicable sadness due to deficient norepinephrine and/or serotonin

Epilepsy

Condition that causes seizures, loss of consciousness due to an excess GABA leads to excess norepinephrine and dopamine

Huntington disease

Condition that causes cognitive and behavioral changes, loss of coordination, uncontrollable dancelike movements, death due to deficient GABA

Hypersomnia

Condition that causes excessive sleeping due to excess serotonin

Insomnia

Condition that causes inability to sleep due to deficient serotonin

Mania

Condition that causes elation, irritability, overtalkativeness, increased movements due to excess norepinephrine

Parkinson disease

Condition that causes tremors of hands, slowed movements, muscle rigidity due to deficient dopamine

Schizophrenia

Condition that causes inappropriate emotional responses, hallucinations due to deficient GABA leads to excess dopamine

Tardive dyskinesia

Condition that causes uncontrollable movements of facial muscles due to deficient dopamine

Neuropeptides

small chains of amino acids that act as chemical messengers in the nervous system and other tissues synthesized by neurons

Neuromodulators

substances which alter a neuron’s response to a neurotransmitter or block the release of a neurotransmitter

Neuronal Pools

Groups of interneurons that make synaptic connections with each other, and are located completely within the CNS

Facilitation

Repeated impulses on an excitatory presynaptic neuron may cause that neuron to release more neurotransmitter in response to a single impulse

Convergence

One neuron receives input from several neurons. Incoming impulses often represent information from different types of sensory receptors. Allows nervous system to collect, process, and respond to information. Makes it possible for a neuron to sum impulses from different source.

Divergence

One neuron sends impulses to several neurons, via branching of its axon. This can amplify an impulse. Impulse from a single neuron in CNS may activate several motor units in a skeletal muscle. Impulse from a sensory receptor may reach different regions of the CNS for processing.

Unmyelinated axons conduct impulses over _____ ____, making them send impulses ______

entire length; slower

Myelin acts as a(n) ______ _____ because it is …

Electrical insulator; rich in lipids, and prevents water and water-soluble substances (such as ions) from crossing membrane

Myelinated axons transmit impulses through ____ _____, in which action potentials “jump” from node to node down the axon

saltatory conduction

Impulse Conduction

the process by which electrical signals are transmitted along neurons or other conductive tissues, which involves the propagation of nerve impulses due to changes in membrane potential, allowing for rapid communication within the nervous system

______ ____ increase permeability to +Na ions, bring membrane closer to threshold; increase likelihood of generating impulses

Excitatory neurotransmitters

______ _______ move membrane farther from threshold, decrease likelihood of generating impulse

Inhibitory neurotransmitters

Excitatory postsynaptic potential (E P S P)

Membrane change in which neurotransmitter opens +Na Channels; Depolarizes membrane of postsynaptic neuron, as +Na enters axon; Action potential in postsynaptic neuron becomes more likely

Inhibitory postsynaptic potential (I P S P)

Membrane change in which neurotransmitter opens +K channels(or Cl+ channels); Hyperpolarizes membrane of postsynaptic neuron, as +K leaves axon; Action potential of postsynaptic neuron becomes less likely

Summation

process in which EPSP and IPSP are added together with all inputs usually occurring at the trigger zone. Net excitatory effect leads to great probability of an action

potential while net inhibitory effect does not generate action potentials.

A neuron can receive thousands of signals at a time and must combine these signals to decide if a(n) _____ _____ is fired.

Action potential

Vesicle trafficking

Process of membrane recycling. Synaptic vesicle becomes part of cell membrane as it releases neurotransmitter. Endocytosis returns membrane to cytoplasm; forms new vesicles