CNS Structure And Function Flashcards
Acetylcholine
Secreted by: -pyrimidal cells in the cerebral cortex -some in the basal nuclei -alpha motor neurons -preganglionic neurons of ANS Postganglionic neurons of PNS -some sympathetic system post-gang neurons
Excitatory
Norepinephrine
Secreted by many neurons in the brain stem and hypothalamus, some in the pons and most sympathetic neurons
Either excitatoy or inhibitory
Dopamine
Secreted by neurons in the substantia nigra
Usually inhibitory
Glycine
Secreted by synapses in the spinal cord
Always inhibitory
GABA
Screted by many areas of the spinal cord and cerebral cortex
Always inhibitory
Glutamate
Secreted by many sensory pathways entering the CNS
Many areas of the cerebral cortex
Always excitatory
What is characteriistic of potentials created on the membranes of dendrites? Why is this so?
Decremental conduction
-a gradual loss of the potential as the depolariztion spreads from the site of initiation and becomes weaker.
The membranes are thin and are partially permeable to potassium and chloride ions and results in the loss of potential
Few voltage gated channels and high thresholds
What is electronic conduction?
On dendrites, a direct spread of electrical current by ion conduction in dendritic fluids without generating an action potential
Happens because of dendrite characteristics: little voltage-gated sodium channel and high thresholds
What is the excitatory state?
The summated degree of excitatory drive to the neuron
More excitation than inhibition
Or
More inhibition that excitation
What is the firing rate of a neuron? What factors does it depend on?
The neuron will fire repeatedly if it remains above the threshold of excitation
Rate depends on normal excitatory rate and the changes in the exciitory rate due to more or less signals
What is synaptic delay? What is the miminal synaptic delay? What does synaptic delay depend on?
Refers to the time it takes to transmit a signal from presynaptic neuron to a post synaptic neuron
Miminal time is 0.5 msec
- time it takes to release neurotransmitter from the presynaptic neuron
- time it takes for the neurotransmitter to diffuse across the synaptic cleft
- how the neurotrmitter acts on the postsynaptic mem
- time it take for the recieving receptor to increase mem permeability
- time for inward diffusion of Na+
What are the compenents oof the telencephalon?
Cerebral hemispheres -gyri and sulci -left and right, 5 (6?) lobes -80% of brain mass Olfactory bulb
Basal nuclei
-corpus striatum (in cerebrum)
What are the functions of the occipital lobe?
Integration of eye focusing movements
Correlates visual images with visial memory
Conscious perception of. Vision
Seperated from the parietal lobe by the parietoccipital sulcus
Parietal lobe
Somatesthetic interpretation
-postentral gyrus
Understanding speech
- wernickes area
- auditory association cortex
Formulation words to express thoughts and emotions
Central sulcus is the landmark
Frontal lobe
Voluntary motor control: precentral gyrus
Motivation Aggression Mood Personality Cognitive processess Verbal communication - Broca's area
Temporal lobe
Receives/interprets olfactory and audition sensation
Responsible for storage of memory related to auditory and visual experiences
Insula
Involed with memory
Psychic cortex with highest level of brain function
- abstract thought
- judgement
Corpus Striatum
Component of the telecephalon, cerebrum.
Functions:
Subconscious movements of skeletal muscles - caudate nucleus, putamen
Globus pallidus - regulation of meuscle tone
What are the components of the Diencephalon?
Epithalamus with Habenular nuclei and Pineal Body
What are the two sources of blood to the brain?
Internal Carotids and vertebral arteries
Compare and conrast the functions of the magnocelluar and parvocellular zones of the RAS and the raphi nuclei
.parvocellular: lateral reticular formation- small cells
Noradreneric pathway from this zone going to the hypothalamus and other limbic structures
Regulat blood flow in the brain
Components of the circle of willis
Posterior cerebral arteries
Posterior communicating arteries
Internal carotids
Anterior cerebral arteries
Anterior communicating artery (unpaired)
Functions of the Reticular Activating System (RAS)
Modulates sensation of pain
Modulates some postural reflexes and muscle tone
Helps control heartbeat and breathing
Regulates level of brain arousal and consciousness
Two zones: magnocellular and parvocellular
What effects do caffeine, theophyllin, theobromine, strychnine and anesthetics on synaptic transmission?
Caffiene, theophylin and theobromine all increase excitability of neurons by decreasing the thershold for excitation
Strychnine also increases excitabliity but by inhibiting inhibitory neurotransmitters
Anesthetics decrease synaptic transmission by increases the threshold for excitation
