CNS Anatomy & Physiology Flashcards
What are the major “pacemakers” or generators of rhythmic electrical activity in the brain?
Cerebral cortex and thalamus
What’s involved when it comes to rhythmic electrical activity?
sleep/wake, consciousness/unconsciousness, and other functions in diseases such as epilepsy
Drugs that can alter brain rhythms
sedative-hypnotics, antiepileptics and general anesthetics
What is the cortex?
the thin outermost layer of brain, densely pack with neuron cell bodies
Highly specialized functions performed by the cerebral cortex
sensory and motor information, planning, reasoning
What percentage of the cerebral cortex is made up of excitatory neurons? What’s the name of the excitatory neurotransmitter?
80%
Glutamate
What percentage of neurons in the cerebral cortex are inhibitory? What’s the name of the inhibitory neurotransmitter?
20%
GABA
What does an EEG measure?
net electrical activity in cortex (but not in deeper regions) using electrodes placed on the scalp
The most powerful pacemaker in the brain
Thalamus
Diffuse modulatory neurotransmitters
Norepinephrine
Dopamine
Serotonin
Acetylcholine
Histamine
Differences between diffuse modulatory NTs (DMNT) and glutamatergic and GABAergic neurons
- Modulatory NTs are not very populated in the brain
- Cell bodies of DMNTs are clustered into small groups mostly in brainstem
- Axons are long and branched and synpase on cortical cells all over the brain
- DMNTs are not consistently excitatory or inhibitory but modulate cortex activity
Two major pathways regulating sleep/wake
Sleep: preoptic area (POA)
Wake: ascending reticular activating system (ARAS)
4 major functions of the hypothalamus
secretes neurohormones that alter pituitary function, and regulate body temperature, thirst, hunger, and sleep
3 major regulators of sleep (groups of sleep-regulating neurons that live in the hypothalamus)
- suprachiasmatic nucleus
- histamine neurons
- orexin neurons
Define circadian rhythms
24 hour cyclic oscillations in biological processes like hormone secretion and gene expression
Hormone involved in regulating circadian rhythms
melatonin
Major structure that regulates circadian rhythm
suprachiasmatic nucleus (SCN) of the hypothalamus
What activates the SCN and what happens when it’s activated?
Light activates SCN causing it to suppress melatonin production during the day
Which lobe plays a key role in forming and storing declarative memories?
temporal lobe
3 key memory structures that are a part of the temporal lobe
- temporal cortex
- amygdala
- hippocampus
Which part of the brain is involved in processing emotions (pleasure, fear, anger) and is active when recalling emotionally-charged memories?
amygdala
Which part of the brain is involved in declarative memories and moves them from short to long-term memory?
hippocampus
Axons of ACh neurons synapse onto what 2 structures
Hippocampus and frontal cortex
How do agonists and antagonists of muscarinic ACh receptors affect memory
-antagonism of brain
muscarinic receptors
can impair working
memory and the
formation of new
memories
-muscarinic agonists can
produce some
improvement in
memory formation
Prefrontal cortex is responsible for…
executive functioning (planning, controlling emotions and impulses, distinguishing right from wrong, motivation, drive, focus, meeting day-to-day responsibilities)
Name the term for the system of brain structures that regulate emotion (mood, fear and reward), and list 5 structures that are part of this system.
Limbic system
5 structures:
1. cerebral cortex
2. amygdala
3. hippocampus
4. hypothalamus
5. thalamus
Name 3 key brain structures that mediate evolutionarily-conserved fear responses, and the 1 structure that is necessary for experiencing fear.
- Hippocampus
- Amygdala
- Hypothalamus
Amygdala is necessary for experiencing fear
Name the most important reward pathway in the brain; explain where the cell bodies in this path are located, what neurotransmitter they release, and where they release it.
Mesolimbic dopamine pathway
-cell bodies are located in the ventral tegmental area (VTA)
-they release dopamine onto the nucleus accumbens (NAc)
When is the NAc selectively activated?
During the perception (or imagining) of pleasant, emotional scenes
Contrast between upper and lower motor neurons:
a. Which have cell bodies in spinal cord, which have cell bodies in brain?
b. What structure does each send its signals to?
a. Upper motor neurons have cell bodies located in the brain. Lower motor neurons have their cell bodies in the spinal cord
b. Upper motor neurons send signals to the spinal cord. Lower motor neurons send their signals to the muscles.
What 1 region of the cortex is responsible for planning and instructing voluntary muscle movement?
Motor cortex
What 1 brain structure is mainly responsible for sequencing and timing (coordinating) muscle movement?
Cerebellum
What group of structures selects and initiates voluntary movements, and includes structures such as striatum and substantia nigra?
basal ganglia
The caudate and putamen together make up what structure?
Striatum
Key function of the nigrostriatal pathway and what neurotransmitter they release and where they release it
Major dopamine pathway for movement; releases dopamine onto the striatum
Name the basal ganglia structure that regulates motor activity levels and state which two neurotransmitters it uses to “turn up” and “turn down” motor activity levels
-striatum regulates motor activity levels
-uses acetylcholine and dopamine
-dopamine from substantia niagra inhibits the activity of inhibitory GABAergic striatic cells (increases motor activity)
-ACh from striatum stimulates inhibitory GABA cells (decreases motor activity)
Pain
-a sensory (detection of damaged tissues) and emotional (experiencing unpleasant feelings) experience
-an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Nociception
the process by which information about a noxious stimulus is conveyed to the brain; it is necessary but not sufficient for experience of pain
Hyperalgesia
Increased pain from a noxious stimulus
Hypoalgesia
diminished pain in response to a noxious stimulus
Analgesia
absence of pain in response to a noxious stimulus
Allodynia
pain due to a non-noxious stimulus
What type of cell is specialized to detect specific types of noxious stimuli?
Nociceptors
4 stages of nociceptive pain processing
- transduction
- transmission
- perception
- modulation
Transduction
noxious stimuli trigger an action potential in nociceptors; AP travels along nociceptor axon from PNS to CNS, releases glutamate to trigger AP in neurons of the spinothalamic tract
Transmission
sending pain signal to processing area; pain signal moves up spinothalamic tract to thalamus
Perception
thalamus sends signal to processing areas (somatosensory cortex, frontal lobe and limbic system) causing awareness & experience of pain; signal continues to periaquaductal gray (PAG)
Modulation
taking action to lessen the pain; PAG neurons send signals down descending pathways, to stimulate the release of endogenous opioids (decreases production of pain signals)
Activation of PAG neurons stimulates release of what substance, and what does it do?
Stimulates the release of endogenous opioids which decreases production of pain signals
Endorphins
Endogenous ligands for opioid receptors which are released in response to pain or stress and are also involved in addiction and reward
Where do endorphins act to reduce their firing rate and incoming pain signals?
nociceptor neurons
Where do endorphins act to make you feel good?
in the brain (especially pain and emotion centers)
Does H1 histamine receptor activation promote sleep or wake?
Promotes wake, alertness and quick reaction time
What is orexin and what is the main job of orexin neurons?
-a neurohormone made by orexin neurons of the hypothalamus
-orexin neurons regulate sleep/wake cycle by alternately suppressing activity of sleep- or wake-active neurons
