Rochet CNS Lecture 1 Flashcards
Key structures of the brain
-Hindbrain
-Midbrain
-Forebrain
Key structures of the hindbrain
-Medulla
-Pons, cerebellum
Key structures of the midbrain
-Substantia nigra
Key structures of the forebrain
-Cerebral cortex
-Basal ganglia: striatum (caudate and putamen), globus pallidus, subthalamic nucleus
-Limbic system: hippocampus, amygdala
-Diencephalon: thalamus, hypothalamus
Functions of the medulla
-Autonomic functions
-Includes centers for controlling respiration, cardiac function, vasomotor responses, reflexes
Functions of the pons
-Bridge
-Relays signals from the forebrain to the cerebellum
Functions of the cerebellum
-Little brain
-Governs motor coordination for producing smooth movements
-Undergoes neurodegeneration in spinocerebellar ataxias
Functions of the substantia nigra pars compacta
-Provides input to the basal ganglia, supplies dopamine to the striatum
-Involved in voluntary motor control (movement with intention) and some cognitive functions (e.g. spatial learning)
-Undergoes neurodegeneration in PD
Functions of the substantia nigra pars reticula
Has an output function, relays signals from the basal ganglia to the thalamus
Functions of the cortex (cerebrum)
Involved in processing and interpreting information
Functions of the basal ganglia
Voluntary motor control, some cognitive functions
Functions of the limbic system
Emotions (amygdala), memory (hippocampus)
Structures of the diencephalon
-Thalamus
-Hypothalamus
Functions of the thalamus
Relay station to and from the cortex
Functions of the hypothalamus
-Regulates internal homeostasis, emotions
-Hormonal control (through the pituitary gland) and direct neural regulation
Functions of the cortex
-The cortex is involved in decision making, higher level functions
-Our senses receive information about the environment, which is passed through the thalamus, to the cortex and back
-Decisions are made in these cortico-thalamic loops about how to interpret and act on the incoming sensory information
-Damage to the cortex can affect movement, speech, personality
-Schizophrenia is considered a disease of the frontal cortex
Role of astrocytes
-Provides neurons with growth factors, antioxidants
-Remove excess glutamate (excitotoxic neurotransmitter)
-Support the blood brain barrier
Role of oligodendrocytes
Produces myelin sheath that insulates axons
Role of microglia
-Provide growth factors
-Clear debris (e.g. myelin debris) by phagocytosis
-Role in neuroinflammation
What is neurotransmission?
-Neurotransmission involves a release of synaptic vesicles from boutons into the synaptic gap (cleft)
-Neurotransmission is triggered by electrical depolarization of the neuron (influx of Na+ ions that changes the charge polarity of the membrane)
How long do action potentials last?
0.2 - 0.5 msec
What is a refractory period?
Period after action potential (hyperpolarized phase) during which a neuron will not fire again
What is an EPSP?
-Excitatory postsynaptic potential (subthreshold depolarization peak)
-Induced by excitatory neurotransmitters
-Excitatory neurotransmitter acts on ionotropic receptor, allowing Na+ ions to cross the membrane
-An increase in the strength of the stimulus will increase the magnitude of the depolarization, so that the threshold depolarization to trigger an action potential is achieved
What is an IPSP?
-Inhibitory postsynaptic potential
-Induced by inhibitory neurotransmitters
-Inhibitory neurotransmitter induces hyperpolarization by allowing Cl- ions to cross the membrane
-An IPSP can decrease the magnitude of a subsequent EPSP
Common amino acid neurotransmitters
-GABA (gamma aminobutyric acid)
-Glycine
-Glutamate
What is the GABA amino acid?
-Major inhibitory neurotransmitter in the brain
-Depresses neuronal excitability by increasing the flux of Cl- ions into the neuron
-There are GABA-A and GABA-B receptors
-Drugs that interact with GABA pathways are generally CNS depressants
What is the glycine amino acid?
Similar to GABA, but acts in the spinal cord
What is the glutamate amino acid?
-Major excitatory aa neurotransmitter in the brain
-Excess glutamate can cause neuronal damage by allowing excessive Ca2+ influx into the neuron
-Glutamate receptors are metabrotropic (GPCRs) or ionotropic (NMDA and AMPA)
Common non-amino acid neurotransmitters
-Acetylcholine
-Dopamine
-Norepinephrine
-Serotonin; 5-hydroxytryptamine (5-HT)
What is acetylcholine?
-Both muscarinic (M1-M5) and nicotinic receptors (as in the periphery)
-Examples of drugs targeting this form of neurotransmission are cholinesterase inhibitors (e.g. Aricept, used to treat Alzheimer’s disease)
What is dopamine?
-Drug targets include the D1-D5 receptors (GPCRs) and the dopamine transporters (DAT)
-DA neurons arise from the ventral tegmental area (VTA) and the SN
-Drugs that block DAT and thus increase extracellular DA can produce euphoria leading to addiction
-Excessive dopaminergic signaling may be involved in schizophrenia
-Loss of DA neurons in the SN is responsible for PD
What is norepinephrine?
-Drug targets include alpha and beta-adrenergic receptors and the norepinephrine transporter
-NE axons arise form the locus coeruleus in the pons region
-NET inhibitors are used to treat depression
What is serotonin
