APPP Quiz – Neuro Flashcards
What are the major cell types of the CNS? (3)
- neurons
- glial cells
- cells of the blood-brain barrier (BBB)
What does myelination result in? (2)
- increase in speed of nerve conduction (due to insulation)
- accumulation of voltage-gated Na+ channels at nodes of Ranvier (gaps on axon in between myelin sheaths)
What is multiple sclerosis (MS)?
- Symptoms
- Treatment
immune-mediated destruction of myelin that results in interrupted electrical nerve signals
- most common demyelinating disease of CNS
- symptoms: numbness, weakness, cognitive difficulties
- treatment: aim to slow disease progression and improve quality of life / high-dose corticosteroids are used to dampen inflammation
How do metabotropic receptors act?
- respond to neurotransmitters
- indirectly opens ion channels
Describe the membrane potential at resting state and the channels and transporters at work.
- RMP = -70 mV
- all voltage-gated Na+ channels and most voltage-gated K+ channels closed
- Na+/K+ transporter actively pumps K+ ions into cell and Na+ ions out to maintain resting levels
Describe voltage-gated Na+ channels.
- open at -55 mV
- inactivated at +40 mV
- Na+ flows in when open
- cause depolarization
Describe voltage-gated K+ channels.
- slow to open
- K+ flows out when open
- cause hyperpolarization
How does synaptic transmission occur?
generation of AP
- ligands bind receptors on post-synaptic neuron (ligand-gated ion channel or metabotropic receptor)
- ion channels open, which changes ion concentration and therefore membrane potential (from resting -70 mV)
- when net charge increases to -55 mV, voltage-gated Na+ channels open
- concentration of Na+ channels at axon hillock initiates AP
- depolarization spreads down axon, and repolarization follows
- depolarization of pre-synaptic terminal opens Ca2+ channels
- Ca2+ binds to SNARE proteins, which triggers the complete fusion of the vesicle with the target membrane
- neurotransmitters in vesicles at the terminal bouton are released into the synaptic cleft, which causes activation or inhibition
How does vesicle loading occur?
- carrier vesicles containing membrane transporter proteins are moved along microtubules
- small molecules (ie. acetylcholine) produced in the cell are taken into vesicles
- loaded vesicles are stored at pre-synaptic membrane
- depolarization leads to docking of vesicles and exocytosis into synapse
What are the neurotransmitters in the CNS? (9)
- dopamine
- norepinephrine
- serotonin
- acetylcholine
- GABA
- glutamate
- glycine
- histamine
- orexin
Dopamine
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory or excitatory
- monoamine
Norepinephrine
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory or excitatory
- monoamine
Serotonin
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory or excitatory
- monoamine
Acetylcholine
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory or excitatory
- amino acid
GABA
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory
- amino acid
Glutamate
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- excitatory
- amino acid
Glycine
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory
- amino acid
Histamine
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- inhibitory or excitatory
- monoamine
Orexin
- Mechanism (Inhibitory or Excitatory)
- Type (Monoamine, Amino Acid, or Neuropeptide)
- excitatory
- neuropeptide
What forms the bulk of the brain?
cerebrum
What is the cerebral cortex made of?
grey matter
What are the 4 lobes of the cerebrum and their functions?
frontal:
- contains motor areas
- controls intellectual activities – ability to organize
- personality, behaviour, and emotional control
parietal:
- contains somatosensory areas
- controls ability to read, write, and understand spatial relationships
temporal:
- contains auditory areas
- controls memory, speech, and comprehension
occipital:
- contains visual areas
- controls sight
What are the functions of the cerebrum? (5)
- perception
- higher motor functions
- cognition
- memory
- emotion
What is the corpus callosum?
thick bundle of axons (nerve fibres) that ensures both sides of the brain (left and right cerebral hemispheres) can communicate and send signals to each other
What is the function of the limbic system and what are its 3 components?
involved in behavioural and emotional responses
- hippocampus
- amygdala
- thalamas – and portion of hypothalamus (mammillary body)
What is the amygdala and what is its function?
region of the brain comprised of a group of nuclei (or cluster of neurons) that is primarily associated with emotional processes
- involved in fear and other emotions related to aversive (unpleasant) stimuli, and fight or flight
- now known to be involved in positive emotions elicited by appetitive (rewarding) stimuli
What is are the functions of the hippocampus?
- processing of long-term memory, spatial navigation, regulation of hypothalamic function, and emotional responses
- memory of the location of objects or people
What are the functions of the thalamus?
acts as a relay between a variety of subcortical areas and cerebral cortex
- processing sensory and motor signals to relay to cerebral cortex
- regulating consciousness, sleep, and alertness
- every system (except olfactory) has a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area
What is the function of the hypothalamus?
coordinates hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, and homeostatic mechanisms
Where is the brainstem?
connects the brain to the spinal cord and the rest of the body
What are the 3 parts of the brainstem and what are their functinos?
midbrain:
- auditory and visual signals
- arousal and human consciousness
pons:
- carries signals that control basic functions (ie. sleep)
medulla:
- controls involuntary functions (ie. breathing, heart rate)
How does the amygdala form associations (ie. good vs. bad)?
uses interconnections with limbic and sensory cortex – then triggers appropriate responses
What are the two different key nuclei of the amygdala and what are their functions?
- lateral nucleus (LA): sensory interface of the amygdala – key site of plasticity
- central nucleus (CE): viewed as the output region
What is the normal physiological state of the amygdala and how is it regulated?
- balance between glutamate and GABA maintains emotional responses at the level appropriate to external stimuli
- regulated by activation of either glutamatergic neurons or GABAergic neurons
What pathways associated with the amygdala can lead to fear memory formation?
auditory thalamic and prefrontal input pathways on the lateral nucleus (LA)
What can happen with amygdala dysfunction? (3)
- anxiety disorders – generalized anxiety disorder, phobias, panic attacks, PTSD, etc.
- seizures
- pain conditions – ie. neuropathic pain
What are the treatments for amygdala dysfunction? (3)
- benzodiazepines / anti-anxiety drugs (valium): enhances GABA-mediated synaptic inhibition, and increases inhibitory signals to balance activation
- serotonin levels are low in patients with emotional disorders – enhanced glutamatergic activity in lateral nucleus (LA) of amygdala and potentiated fear behaviours
- SSRIs: decreases amygdala response to fear and other aversive stimuli
What is the entorhinal cortex (EC) and what are the different parts?
the major input and output structure of the hippocampal formation
- spatial information (WHERE) relays through medial entorhinal complex (MEC) – to parietal cortex
- non-spatial information (WHAT) relays through lateral entorhinal cortex (LEC) – to temporal cortex
What type of neurons does the medial entorhinal complex (MEC) and lateral entorhinal cortex (LEC) contain?
cholinergic neurons (acetylcholine)
What neurotransmitter do hippocampal neurons mainly release?
glutamate or GABA
What are the 4 sections/sub-structures of the hippocampus?
- MEC and LEC project into the hippocampus dentate gyrus (DG) region
- project into CA3 region (cornu ammonis)
- CA3 projects to CA2 and CA1
- CA1 projects back to entorhinal cortex
What is Alzheimer’s disease?
progressive neurodegenerative disease most often associated with memory deficits and cognitive decline
- damage and progressive loss of cholinergic neurons
- LEC and MEC (hippocampus) contain cholinergic neurons
- progressive memory impairment and cognitive dysfunction
What causes the damage to cholinergic neurons in Alzheimer’s disease?
- Aβ plaques (generated from amyloid precursor protein cleavage)
- Tau protein aggregates
What is the treatment for Alzheimer’s disease?
cholinesterase inhibitors – agents that block the breakdown of acetylcholine
Which 2 structures of the brain play an essential role in sleep-wake regulation and arousal?
thalamus and brainstem
The hypothalamus is important for communicating with what gland?
pituitary gland
- one of the most important functions of the hypothalamus is linking the nervous system to the endocrine system via the pituitary gland
What can hypothalamus dysfunction cause?
appetite, temperature, and sleep disorders
- hypothalamic obesity – can develop from major hypothalamic injury/damage affecting the centres of appetite regulation and energy balance
How does the reflex arc occur?
- incoming sensory signals from the body (afferent sensory nerve fibres) synapse at posterior/dorsal horn with interneurons found in the intermediate grey
- interneurons signal to efferent motor nerve fibres in anterior horn to stimulate muscle movement
Branches that Feed Into the brain
- AP travels through dorsal root ganglion (DRG) nerve fibre
- synapse at posterior/dorsal horn (PH)
- action on afferent nerves leading to actions at specific sites in the brain
Relay Signals from the Brain
efferent nerves from the cortex signal to anterior horn to stimulate motor movements
What system does the spinal cord link to?
autonomic system
- intermediate grey matter contains autonomic neurons with axons that leave through ventral roots
How many bones does the skull have and what are the major ones?
- 22 bones
- cranial bones enclose and protect the brain – frontal, temporal, occipital, parietal, sphenoid, ethmoid
What is the function of the meninges?
- form a major part of the mechanical suspension
- necessary to keep CNS from self-destructing
What is the dura mater and what is its function?
thick connective tissue (abundant collagen) membrane
- provides mechanical strength
- connects skull to arachnoid cell layer
What is the arachnoid and what is its function?
thinner collagenous membrane
- connects to pia mater cell layer by delicate strands of connective tissue (arachnoid trabeculae)
- suspends CNS in its bath of CSF
What is the pia mater?
thinner collagenous membrane
What stabilizes the CNS during head movement?
partial flotation of CNS in subarachnoid CSF, in combination with mechanical suspension
How is CSF formed? Where does it enter circulation?
- formed by filtration of blood
- enters venous circulation through arachnoid villi
What are arachnoid villi and what are their function?
outpouchings that poke through holes in the walls of the venous system
- act like valves
- when CSF pressure is greater than venous pressure, CSF moves into venous system
- when CSF pressure is less than venous pressure, villi snap shut and venous fluid does not enter subarachnoid space
- imbalance can lead to intracranial pressure
What is an epidural hematoma?
bleeding between dura mater and skull
- result of epidural bleeding due to skull fracture causing a blood vessel rupture
- can lead to increased pressure on, and damage to, brain tissues
- presents as severe headache, nausea and vomiting, slurred speech
What is a stroke?
lack of blood flow to the brain
- result of subarachnoid bleeding due to spontaneous rupture of blood vessel
- build-up of blood can cause pressure on the brain
- symptoms are similar to epidural hematoma
What is the blood brain barrier (BBB) and what are its functions?
protective functional separation of the circulating blood from the CNS
- limits the penetration of substances – keeps toxins and pathogens (and drugs) out, and facilitates select transport of molecules
What are the 4 layers of the BBB?
- endothelial cell layer
- pericyte layer
- protecting basement membrane
- glial barrier formed by astrocyte endfeet
What is the pericyte layer of the BBB and what is its function?
lines 80% of the capillary layer
- stabilizes endothelial layer
- regulates BBB permeability
What is the glial barrier of the BBB and what is its function?
formed by astrocyte endfeet
- astrocytes interact with blood vessels with their endfeet and regulate dilation and constriction of microvessels to control blood flow
What do both the pericyte cell layer and glial barrier of the BBB contribute to?
maintenance and regulation of endothelial cell tight junctions (length, wide, and complexity)
What are the transport systems to cross the BBB? (3)
endothelial cell layer has specific transport systems that permit the supply of nutrients, ions, and bioactive molecules
- diffusion of CO2 and O2 and lipid-soluble (small nonpolar) molecules (transcellular) or small water soluble (paracellular)
- active transport – ie. glucose
- receptor-mediated (ie. insulin) and adsorptive transcytosis (albumin)