11 C Flashcards
How does sensory information flow?
From neuron to neuron
What are neurons functionally connected by?
Synapses
What are synapses?
Junctions that mediate information transfer (neuron to neuron or from one neuron to an effector cell)
What are the two common types of synapses?
Axodendritic and axosomatic
Where do axodendritic synapses occur?
Between axon terminals of one neuron and dendrites of others
Where do axosomatic synapses occur?
Between axon terminals of one axon and the body (soma) of another
What are the 3 less common types of synapses?
Axoaxonal
Dendrodendritic
Somatodendritic
Where does a presynaptic neuron send impulses?
Towards the synapse
Where do postsynaptic neurons send impulses?
Transmits electrical signals away from synapse (receives information)
In the PNS what are postsynaptic neurons?
Muscle cells, neurons or gland cells
What kind of synapses are more common, electrical or chemical?
chemical
What are electrical synapses?
Neurons that are electrically coupled (joined by gap junctions)
Synchronize activity
Nerve impulses remain electrical
Where are electrical synapses most abundant?
Embryonic nervous tissue
What are chemical synapses specialized for?
Release and reception of chemical neurotransmitters
What are the two parts of chemical synapses?
Axon terminal and neurotransmitter receptor region
Where is the axon terminal
Presynaptic neuron
has synaptic vesicles with neurotransmitters to be released
Where is the neurotransmitter receptor region?
On the postsynaptic neuron’s membrane
On dendrite or cell body
What are the two parts of the chemical synapse separated by?
Synaptic cleft (fluid filled space)
What is allowed because of electrical impulses changing to chemical across synapse and then back into electrical?
Nerve impulse regulation (allows for decision for propagation or termination of impulse)
More fine tune regulation
What does the synaptic cleft prevent?
Nerve impulses from directly passing from one neuron to the next (its a barrier)
What does the transmission across a synaptic cleft depend on?
Release, diffusion, and receptor bind of neurotransmitters to their receptors
What direction of communication does synaptic cleft allow for between neurons?
Unidirectional communication
Does a chemical or electrical event happen across the synaptic cleft?
Chemical event
What arrives at the axon terminal of presynaptic neuron to start transmission across chemical synapses?
Action potential
What does the action potential arrival at the presynaptic neuron cause?
Voltage-gated Ca2+ channels to open and Ca2+ then flows into the cell
What protein in the presynaptic neuron binds to calcium and what does it cause?
Synaptotagmin protein binds to calcium and promotes fusion of synaptic vesicles with the axon membrane
What is exocytosed from the presynaptic neuron after synaptic vesicles bind to the axon membrane?
Neurotransmitter is exocytosed into the synaptic cleft
higher impulse frequency causes more to be released
Where do neurotransmitters bind after they diffuse across the synapse?
Binds to receptors on the post synaptic neuron (often chemically gated ion channels0
What happens to ion channels when the neurotransmitter binds to it?
They are opened and an inhibitory or excitatory even happens (graded potential)
What are the three ways a neurotransmitter effect is terminated?
An astrocyte or axon terminal reuptakes the neurotransmitter
Enzymes degrade it
It diffuses away from synaptic cleft
What is synaptic delay?
Rate limiting step of neural transmission
time needed for neurotransmitter to be released, diffuse across synapse, and bind to receptors
How do neurotransmitter receptors cause graded potentials that vary in strength?
The amount of neurotransmitter released
The time the neurotransmitter stays in area
What are the two types of postsynaptic potentials?
EPSP- excitatory postsynaptic potentials
IPSP - inhibitory postsynaptic potentials
What happens During an excitatory synapse?
The neurotransmitter binding opens chemically gated channels that allows flow of Na+ and K in opposite directions (Na+ influx is greater than K+ efflux)
When does EPSP help trigger AP?
If EPSP is of threshold strength
Where can the EPSP spread to? What does this cause?
The axon hillock (cone shaped part of the soma)
This triggers opening of voltage gated channels and causes AP to be generated
What does IPSPS do to the neuron?
Reduces postsynaptic neuron’s ability to produce an action potential
What does IPSPS do to the membrane of a neuron?
Makes the membrane more permeable to K+ or Cl-
What is IPSP?
A local hyperpolarization of postsynaptic membrane that drives the neuron away from AP threshold (less likely to be genrated)
TF: A single EPSP can induce an action potential
False
How do EPSPs influence postsynaptic neurons?
By summation
TF: Most neurons receive both excitatory and inhibitory inputs from many other neurons
True
What are the two types of summation?
Temporal summation
Spatial summation
What happens in temporal summation?
One or more presynaptic neurons transmit impulses in rapid fire order (TIME)
What happens in spatial summation?
Postsynaptic neuron stimulated simultaneously by large numbers of terminals at the same time (Space)
What is the language of the nervous system?
Neurotransmitters
How many neurotransmitters have been identified?
50 or more
How many neurotransmitters does one neuron make?
Two or more (can exert several influences)
What are neurotransmitters classified by?
Chemical structure and function
What is the most understood neurotransmitter?
Acetylcholine (ACh)
Where is ACh released?
Neuromuscular junctions
By some ANS neurons
By some CNS neurons
What is ACh synthesized From?
Acetic acid and choline
By an enzyme called choline acetyltransferase
What is ACh degraded by?
Acetylcholinesterase (AChE)
What are the two biogenic amines?
Catecholamines
Indolamines
Where are biogenic amines broadly distributed?
The brain (behaviors and biological clock)
What do imbalances of biogenic amines lead to?
Mental illness
What are the catecholamines?
Dopamine
Norepinephrine
Epinephrine
What are the indolamines?
Serotonin
Histamine
What amino acids are associated with the chemical structure of neurotransmitters?
Glutamate
Aspartate
Glycine
GABA
What peptides are associated with the chemical structure of neurotransmitters?
Substance P
Endorphins
Gut-brain peptides
What is Substance P?
A mediator of pain signals
What do endorphins act as?
Natural opiates - reduce pain perception
What are the three neuropeptide endorphins?
Beta endorphin, dynorphin, and enkephalins
Where are gut-brain peptides made and what are the two listed?
Made in gut and sent to brain
Somatostatin
Cholecystokinin
What nervous systems do purines act in?
CNS and PNS
What do purines do as neurotransmitters?
Produce fast or slow responses
Induce calcium influx in astrocytes
What does adenosine do as a neurotransmitter?
Potent inhibitor in the brain
Caffeine blocks adenosine receptors
What is a purine that is a main neurotransmitter?
ATP
What are the common gastrotransmitters?
Nitric oxide
Carbon Monoxide
Hydrogen sulfide gas
When are gastrotransmitters synthesized?
On command
Are gastrotransmitters lipid soluble or not?
Lipid soluble
What is nitrous oxide used for in the body?
Involved in learning and formation of new memories
Smooth muscle relaxation in intestine
What does Hydrogen sulfide gas act directly on?
Ion channels to alter function
What do endocannabinoids do?
Act as same receptors as THC
Involved in learning, memory, neuronal development, controlling appetite, and suppressing nausea
Are endocannabinoids lipid soluble?
yes
When are endocannabinoids synthesized?
On command
What are neurotransmitters classified by when talking about function?
Effects (excitatory vs inhibitory)
Actions (direct vs indirect)
Where is ACh an excitatory neurotransmitter?
Neuromuscular junction in skeletal muscle
Where is ACh inhibitory as a neurotransmitter?
In cardiac muscle
What neurotransmitters are usually inhibitory?
GABA and glycine
What neurotransmitter is usually excitatory?
Glutamate
What happens in direct action?
Neurotransmitter binds to and opens an ion channel
Promotes rapid response by altering membrane potential (ACh and amino acids)
What happens in indirect action?
Neurotransmitter acts through intracellular second messengers, usually G protein pathway
They cause a more broad. and longer lasting effects
(Biogenic amines, neuropeptides, and dissolved)
What are the two types of neurotransmitter receptors?
Channel-linked receptors
G protein linked receptors
What do channel linked receptors do?
Mediate fast synaptic transmission
What do G protein linked receptors do?
Oversee slow synaptic responses
What kind of channels are channel-linked receptors?
Ligand-gated ion channels
What type of action happens with an ionotropic receptor (channel linked)?
Action is immediate and brief
What are excitatory receptors in channel linked receptors channels for?
Small cations (let in Na+)
What are inhibitory receptors of channel linked receptors channels for?
Cl- influx that causes hyperpolarization
What kind of responses happen in G protein linked (metabotropic) receptors?
Indirect
Complex
Slow
Prolonged
What kind of complexes are G protein linked receptors?
Transmembrane protein complexes
What do G protein linked receptors cause?
Widespread metabolic changes
What are two examples of G protein linked receptors?
Muscarinic ACh receptors
Receptors that bind biogeneic amines and neuropeptides
What does activation of a G protein cause when a neurotransmitter binds to the G protein linked receptor?
A control of the production of second messengers
What are some examples of second messengers?
cAMP
cGMP
DAG
Ca2+
What do second messengers do?
Open or close channels
Activate kinase enzymes
Phosphorylate channel proteins
Activate genes and induce protein synthesis
TF: Neurons functions in groups
True
What do neuron groups contribute to?
broader neural functions
What are neuronal pools?
Functional groups of neurons
What do neuronal pools do?
Integrate incoming information received from receptors or other neuronal pools
Forward processes information to other destinations
What is the structure of a single neuronal pool?
Single presynaptic fiber branches and synapses with several neurons in pool
What is the discharge zone of the neuronal pools?
Neurons most closely associating with incoming fiber
What is the facilitated zone of the neuronal pool?
Neurons farther away from incoming fiber
What are circuits?
Patters of synaptic connections in neuronal pools
What are the 4 types of circuits?
Diverging (Amplify)
Converging (Concentrate)
Reverberating (rhythm)
Parallel after discharge (involved in thinking)
What happens in serial processing?
Input travels along one pathway to a specific destination
How do systems work in serial processing?
In all or none manner to produce specific anticipated response
What is an example of serial processing?
Spinal reflexes (reflex arcs) Rapid and automatic responses to stimuli
What is parallel processing?
Input travels along several pathways
Different parts of circuitry deal simultaneously with information
TF: in Serial processing one stimulus promotes numerous responses
False
This is parallel processing
What is parallel processing important for?
Higher level mental functioning
