Chapter 45 Flashcards
What types of actvivties occur at the lower brain or subcortical levels?
-Subconscious actvities like:
–> aterial pressure, respiration, feeding, salivation, anger, excitement, SEXUAL RESPONSE, pain and pleasure.
What functions occur at the higher brain or cortical level?
memory storage and thought processes
What is the difference between chemical and electrical synapses?
Chemical synapses use neurotrasmitters to excite, inhibit or modify while electrical channels conduct electricy directly through gap junctions
What teo structures are present in the axon terminal?
Mitochondria and transmitter vessicles
What are the two important components of receptor proteins?
Binding component and the ionophore component.
What are the differences between the two ionophores (cation channels and anion channels)?
Cation channels- EXCITATORY and typically sodium ion channels that are lined with negative charges
Anion channels- INHIBITORY and typically chloride channels that are lined with positive charges
Are second messenger activator receptors typically long acting or short acting? What molecules are they typically associated with?
- Long acting
- cAMP and cGMP which cause the prolonged effect typically in gene transcription
What are the 4 changes that can be elicited by a postsynaptic receptor?
- opening of specific ion channels
- activation of cAMP and cGMP
- activation of intracellular enzymes
- activation of gene transcription
What is the typical action elicited by excitatory receptors?
- opening of sodium channels (pushes the membrane potential towards the more + or threshold direction)
- associated with the depressed conduction through Cl- or K+ channels
What is the typical response elicited by inhibitory receptors?
- opening of Cl- channels and increased K+ efflux
- means more negative inside of the cell which= further from threshold potential
How do small molecule and neuropeptide transmitters act diffferently?
-
-small molucules are small and FAST acting
- –>continually recycled
-
-neuropeptides are large and SLOW acting
- –>not recycled
- –>synthesized and transported at a very slow rate via AXONAL STREAMING
Are small molecule or neuropeptide transmitters more potent?
-neuropeptides are about 1000x more potent
What class of small molecule neurotransmiter is acetycholine? Where is it secreated?
- Class I
- Secreated by neurons in:
–>pyramidal cells of motor cortex
–>basal ganglia
–>skeletal muscle
–>pre-ganglionic of ANS
–> post-ganglionic of PSNS
–>some post-ganglonic of sympa. nervous system
What is the major effector function of ACh?
-mostly excitatory except at some PS nerve endings like CNX
What are the class II small molecule neurotransmitters?
-Amines
–> norepi, epiepherine, dopamine, serotonin, histamine
What two areas secrete norepinepherine? Is it excitatory or inhibitory?
- brainstem and hypothalamus (locus ceruleus in the pons) as well as the postganglionic neurons of the sympathetic ANS.
- Can be either excitatory or inhibitory
Where is dopamine secreted? What is it’s effect?
- secreted at substantia nigra and terminate at the basal ganglia
- inhibitory
Location of serotonin secretion? Effect?
- median raphe of the brain stem
- inhibitor of pain and inhibitory effects controlling sleep and mood
What are the class III neurotransmitters?
Class III: amino acids
- GABA
- Glycine
- Glutamate
Where is GABA secreted and what is the effect?
- secreted by the spinal cord, cerebellum and basal ganglion and cortex
- inhibition
Where is glycine secreted and action?
- spinal cord
- inhibition
Glutamate action and secretion location?
- Presynaptic terminal in the CNS and cerebral cortex
- Excitation
What is the main excitatory neurotransmitter?
Glutamate
What is the action of NO?
-long term behavior and memory
What is the resting membrane potential of spinal motor neurons? How is this calculated?
- 65mV
- EMF(mV)= +/-61xlog ( [inside]/[outside] )
What is the effect of the IPSP? What causes it?
- opening of Cl- or K+ channels
- moves the membrane potential away from threshold (hyperpolarize)
- Caused by nt like GABA and Glycine
What is the cause and effect of the EPSP?
-excitatory transmitters cause influx of Na+ and movement of the membrane potential closer to threshold ~20mV from -65mV to -45mV
Where does the EPSP orriginate and why?
- The axon hillock
- high concentration of Na+ channels
What is the difference between sptial and temporal summation?
Spatial summation is caused my activating multiple terminals in widely spaced areas (spatial)
Temporal summation is the effect of successive discharges from a single pre-synaptic terminal causing them to add together
Why do dendrites display decremental conduction?
-membranes contain very few Na+ channels and therefore the membrane potential change decreases as distance from the stimulus increases
What is synaptic fatigue and what are some causes?
- decrease n firing rate of the post synaptic neuron even though the pre-synaptic stimulation is rapid
- caused by exhaustion of transmitter stores, inactivation of post-synaptic receptors, and abnormal ion concentrations
How does alkylosis and acidosis affect synaptic transmission?
- Alkylosis increases neuronal excitability (Seizures)
- Acidosis depresses neuronal activity (diabetic acidosis)
What does hypoxia do to neuronal excitability?
-causes complete loss of excitability after only a few seconds
What drugs cause inreases in neuronal excitability?
Caffeine, theophylline (tea), theobromine (cocoa)
-reduce threshold
What drugs cause decreases in synaptic transmission?
Anasthetics
-increase thresholds
How does strychnine increase neuronal excitability and cause tonic muscle spasms?
-inhibits actions of inhibitory transmitters like glycine
