6.3 Functional brain system Flashcards
What are functional brain systems
Networks of neurons that work together & span wide areas of brain
– Limbic system
– Reticular formation
–Direct & Indirect pathways of the basal nuclei
describe the limbic system, what are the general functions?
- Structures from medial cerebral hemispheres & diencephalon
- Cerebral structures encircle (limbus=ring) superior brainstem
- General functions are:
- Establish emotional states
- Linking conscious, intellectual functions of cerebral cortex with unconscious & autonomic functions of brain stem
- Facilitating memory storage & retrieval
what is the amygdala
structure of limbic system
- Almond-shaped nucleus, anterior to tail of caudate & deep in medial temporal lobes
– Critical for responding to perceived threats
– Required for emotional memory
What is the cingulate gyrus
- part of limbic system
– Located along medial aspects of cerebral hemispheres next to corpus callosum
– role in responding to perceived threats, expressing emotions via gestures, & resolves mental conflict when frustrated
What is the hippocampus
part of limbic system
- located in medial temporal lobe
- Connected to mammillary bodies of hypothalamus via white matter (Fornix)
– Plays a role in learning, memory & emotion
how is the limbic system involved in emotion and cognition
Limbic system interacts with prefrontal lobes:
– Can react emotionally to things we consciously understand to be happening
– Are consciously aware of emotional richness in our lives
has:
- diencephalon structures, fiber tracts (white matter) and cerebral structures
Decribe reticular formation
- 3 braod columns along length of brain stem
- has far-flung aconal connections w/ hypothalamus, thalamus, cerebral cortx, cerebellum, spinal chord
Motor function: (some)
- regulate visceral motor functions (vasomotor, cardiac and respiratory centers)
- helps control coarse limb movements
What is RAS
reticular activating system
*keeps your conscious
- sends impulses to cerebral cortex to keep conscious, alert and enhance excitabiltiy
- filters out repetitive & weak stimuli (99%)
- LSD interfers with sensory dampers, promoting and overwhelming sensory overload
- inhibited my sleep centers of hypothalamus and other neural regions
- Depressed by alcohol, sleep inducing drugs and tranquilizers
- aka cant keep cortex active
- Severe injurt results in premanent unconsciousness
Describe consciousness
- involves simultaneous activity of alrge areas of the cerebral cortex
- > conscious perception of sensation,
- > voluntary initiation and control of movement
- > capabilities associated with higher mental processing (memory, logic, judgement etc)
- defined on continum that grades behaviour in response to stimulse:
1. Alertness, 2. Drowsiness 3. Stupor (severely intoxicated) 4. Coma
What is sleep
- State of partial unconsciousness -> can be aroused by stimulation
- Alternating cycles of sleep & wakefulness reflect a natural circadian rhythm
- RAS activity is inhibited during sleep (however RAS also mediates dreaming)
*RAS not “turned off” bc still has a role
• Suprachiasmatic & preoptic nuclei of hypothalamus time sleep cycle
–> Releases peptide orexins which activate reticular formation (“wake-up” chemical)
*orexins accumulate as sleep goes on
what are the types of sleep
2 major types of sleep: nonrapid eye movement (NREM) and Rapid eye movement (REM)
- Typical sleep pattern alternates between REM & NREM sleep
Describe the importance of sleep
- Slow-wave sleep (NREM stages 3 & 4) presumed to be restorative stage
*Sleep deprived people spend more time in these stages •
People deprived of REM sleep become moody & depressed & exhibit various personality disorders
– >REM sleep may give brain the opportunity to work through emotional problems in dream imagery
- REM sleep may be a reverse learning process purge useless info
- Enhances immune system: Sleep inducing factors include Interlukin-1, interferon, serotonin & tumor necrosis factor
Describe memory
- storage and retrieval of info
- 2 stages of storage
1. Short term memory: temporary holding of info, limited to 7-8 pieces of info
2. Long term memroy: limitless capacity
How is info transfered from STM to LTM
Factors that affect transfer from STM to LTM
- Emotional state:best if alert, motivated, surprised, & aroused
- Rehearsal: repetition & practice
- Association: tying new information with old memories
- Automatic memory: subconscious information stored in LTM
Describe the molecular basis of memory
during learning:
- > alterned mRNA is synthesized and moved to axons and dendrites
- dendritic spines change shape
- extracellular protiens are deoposited at synapses involved in LTM
- number & size of presynaptic terminals may increase
- More neurotransmitter is released by presynaptic neurons
* memory goes backwards: Axons -> dendrities, strengthens circuits to make AP generation easier (like drawing over a shape over and over)
WHat are teh categories of memory
- declarative (explicit) and non declarative (implicit)
Declarative: semantic (facts), episodic (events), spatial (locations) memory
*aka I know this info
Nondeclarative (implicit): emotional, motor, proecdural (how to do things) memory
*aka more motore based, harder to put into words
What is declarative memory?
- Related to conscious thoughts & language ability
- Stored in LTM with context in which it was learned
- Hippocampus & surrounding temporal lobes function in consolidation & access to memory
- ACh from basal forebrain is necessary for memory formation & retrieval
* Info comes in (sensory input) -> association cortex medial temporal lobe (hippocampus)
then can go to thalamus (relay station) OR prefrontal cortex (how to act on info)
*Ach is what allows pathways to work properly
What is nondeclarative memory?
*remember by doing, harder to undo
- Less consciour or unconscious
- aquired through experience and repetition (best remembered by doing; hard to unlearn)
- Emotional memory: amygdala
Motor memory: cerebellum
Procedural memory: basal nuclei relay sensory & motor inputs to thalamus and premotor cortex (allows to do things in patterns)
*Dopamine from substanta niagea is necessary
*sensory & motor inputs -> associaltion corex -> Basal nuclei -> thlamus -> premotor cortex
What do the direct and indirect circuits involve
- Cortex (Glu)
- Lentiform nuclei: putamen & globus pallidus (GABA)
* Note: GPi & GPe are tonically active -> default suppression of thalam
- Thalamus (Glu)
- Subthalamic nuclei (Glu)
- Substantia Nigra: Pars compacta (Dopamine)
- both circuits have same input that take diff pathways to get to same output
- direct circui _____ SNpc dopamine input while indirect is____ by SNpc dopamine
- direct circuit excited by SNpc dopamine input while indirect is inhibited by SNpc dopamine
When an excitatroy fires a lot, the postsynaptic neuron will fire ____
When excitatroy neuron fires a little the post synpatic neuron will fire _____
When an excitatroy fires a lot, the postsynaptic neuron will fire a lot
*somebody screaming at you go go go
When excitatroy neuron fires a little the post synpatic neuron will fire a little
* somebody says quietly go
When an inhibitory neuron fires a lot, the postsynaptic neuron will fire ____
when an inhibtroy neuron fires a little, the psot synaptic neuron will fire _____
When an inhibitory neuron fires a lot, the postsynaptic neuron will fire a little
* like yelling STOP
when an inhibtroy neuron fires a little, the psot synaptic neuron will fire a lot
*comparison to when have a lot of inhibition
pathway anatomy of the direct pathway
Cortex -> caudate/ putamen -> GPi -> Motor thalamus -> motor cortex
What is Effect of direct pathway on thalamic input to cortex
INC excitatory thalamic input to cortex
(excitatroy, -> glu release)
What is Effect of direct pathway on motor activity
- turns UP motor activity
What dopamine receptor is used in direct pathway
D1 (exctatory, Glu release)
describe dopamine input from substantia nigra in the direct pathway
Excites/enhances pathway to increase thalamic output to cortex
(more motor activity)
Describe ACH input to Caudate/Putamen in direct pathway
Inhibits (turns down) pathway to decrease motor activity (GABA release)
Describe pathway anatomy of indirect pathway
Cortex -> caudate/putamen -> GPe-> substalamic N -> GPi -> Motor thalamus -> Motor cortex
Describe effect of thalamic imput on cortex in the indirect pathway
DEC excitatiory thalamic input to cortex (Glu release)
Describe effect of indierct pathway on motor activity
turns DOWN motor activity (Gaba release)
What dopamine receptor is used in indierct pathway
D2
-inhibitory (GABA release)
Effect of dopamine imput from Substantia nigra on indirect pathway
- inhibits /depresses pathway to increase thalamic output to cortex (more motor activity)
Effect of Ach input to caudate/ Putamen in indirect pathway
Excited (turns up) pathway to decrease motor activity
