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105 Cards in this Set
- Front
- Back
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What kind of organisms is the nervous system found in?
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multicellular organisms (jellyfish)
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The 2 Divisions of the nervous system
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central nervous system (CNS)=brain and spinal cord. peripheral nervous system (PNS)=everything else
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4 primary types of glial cells
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astrocytes, oligodendrocytes,
Schwann cells, microglia |
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general properties of glia
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a. divide in adult
b. non-conducting c. “support”/metabolic roles |
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Function of astrocytes
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a. processes surround neurons, synapses, blood vessels
b. scaffolding for neurons, especially during development c. uptake/release of chemicals including neurotransmitters d. modulate synaptic transmission |
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Function of oligodendrocytes and Schwann cells
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a. myelinate neurons in central (oligo) and peripheral (Schwann)nervous system
b. regeneration c. uptake/release of chemicals including neurotransmitters d. modulate synaptic transmission 1. CNS glia(oligodendrocytes) inhibit axonal regeneration, PNS glia (Schwann cells) promote regeneration |
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Function of microglia
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a. immune response in brain
b. uptake/release of chemicals |
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How many neurons are there?
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(~100 billion most in cerebellum), small number generated in adult=plasticity?
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Neurons- what are there Diversity of forms and functions
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allows neurons to play numerous roles in information processing, information transfer, etc.
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efferent
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transmits information or travels from a structure
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afferent
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transmits information or travels toward a structure
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Structure of neuron - Plasma membrane
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A lipid bilayer.
a. proteins embedded in layer, some go through the membrane (channels)-receptors b. allows separation of intracellular and extracellular environments |
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Structure of a neuron- cell body or soma (somata)
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a. nucleus and genetic material (DNA)- controls protein synthesis
b. cytoplasm-contains organelles for protein synthesis, ions, etc. |
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Structure of a neuron - axon, axon hillock
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only one axon for a neuron
a. axons are adapted for long-distance transfer of information=output b. the axon hillock is the site of action potential initiation c. collaterals refer to branches of axons |
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Structure of a neuron- dendrites, spines
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a. can be many dendrites, most inputs (synapses) to neuron are on dendrites
b. spines are protrusions off dendrites-also get inputs (synapses) c. dendrites integrate info. over a large area d. dendrites and spines can act as biochemical compartments |
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Structure of a neuron - axon terminals
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at the ends of axons or en passant
a. contain vesicles of neurotransmitter (synapse) b. communication between cells |
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Structure of a neuron- myelination and nodes of Ranvier
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Schwann cells and oligodendrocytes form myelin
b. myelin increases action potential conduction velocity c. nodes are breaks in the myelin sheath |
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Structure of a neuron- synapses
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a. a gap between the axon terminal and the dendrite/spine
b. chemical communication |
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groups of neurons
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a. groups of cell bodies are nuclei (usu. CNS) or ganglia (usu. PNS)
b. bundles of axons are nerves (PNS) or tracts (CNS), also known as white matter -nerves can be sensory, motor or sensorimotor |
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blood brain barrier and vasculature
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a. brain uses a lot of energy, thus needs large blood supply
b. brain is a protected environment, many substances cannot cross the blood brain barrier. Since neurons don't divide much, this is important c. endothelial cells lining capillaries of the brain have tight junctions between them=barrier to transport d. for desired molecules (e.g. glucose) there are specific transport molecules e. very important for delivery of drugs that target the brain |
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What is brain behavior?
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It’s the study of how the nervous system generates and is affected by an organism’s
behavior |
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Behavior
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includes such topics of intake and processing of information (including information concerning the organism's internal state and past history), integration of information, actions based on this processing.
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Dualism
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mind and body are different substances
a. Cartesian Dualism: mind and brain interact via pineal body 1. problems -remove pineal doesn't effect mind -animal mind -how does mind affect brain (energy and mass) |
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Monism
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rything has only one kind of existence
a. materialism-everything is material or physical, i.e. all 'mind' is explicable in physical (brain and body) terms b. mentalism-only the mind exists c. identity position-mental processes are the same thing as brain processes, but described in different terms. |
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Resting potential
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the difference in voltage between the outside of a cell and the inside; neurons are therefore polarized
1. Measurement using microelectrodes 2. Concentration/electrical gradients responsible |
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"Battery" for neurons
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important for rapidity of excitation
-allows rapid changes in membrane potential |
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Depolarization
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passive property
-membrane potential more positive |
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Hyperpolarization
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Passive property
-membrane potential more negative |
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Action Potential (AP)
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allow long-distance transmission of information, unlike passive potentials a self-regenerative event
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voltage-gated ion channels
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a. Na+ channels trigger and are active during AP rising phase
b. K+ channels slower to activate, repolarize membrane c. there are other types of voltage-gated channels not necessary for the AP |
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Characteristics of the action potential
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a. “the all-or-none law”-positive feedback
b. depolarization very large, rapid and stereotyped c. Na/K pump not directly required for each action potential |
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Threshold
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the amount of depolarization necessary to trigger an action potential
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All or none law
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once triggered, the AP characteristics are fixed
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Refractory period
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the amount of time after an AP when it is more difficult (relative refractory period) or impossible (absolute refractory period) to fire another AP
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Action potential propagation
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1. speed-faster in larger-diameter axons due to longer spread of depolarization
2. Myelination-as an insulator, it also improves spread of depolarization and thus speed of propagation 3. nodes of Ranvier and saltatory conduction |
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action potentials vs. graded potentials
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1. APs good for long-distance transfer of information, but frequency information only
2. graded potentials short range, but have amplitude information also 3. only neurons support action potentials; other cells (include glia) have graded |
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Coding by action potentials, intensity vs. quality
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1. action potentials and rate (frequency) coding-larger intensity stimulus leads to a higher action potential frequency
2. "labeled lines" and coding of quality-i.e. different populations of axons carry specific types of information. These can remain segregated through PNS and CNS |
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Drugs that affect the action potential
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1. local anesthetics (novocaine, lidocaine, etc.) block voltage gated Na channels
2. tetrodotoxin (fugu) also blocks Na channel 3. K+ channel blockers (TEA, 4-aminopyridine) prolong the action potential 4. such drugs have been very important for studying ion channels activated during an action potential |
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Multiple sclerosis
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It is a De-myelinating disease
1. characteristics a. breakdown of myelin in CNS and PNS, progressive and incurable b. causes block of APs and thus block of information transfer 2. possible causes a. immune system attacks myelin b. genetic, viral causes 3. roles of de-myelination 4. treatment-incurable-steroids and immunotherapy may help symptoms. |
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Chemical vs. electrical transmission: Loewi's "vagusstoff" experiment
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1. stimulate vagus nerve in frog=decrease heart rate
2. transfer fluid from stimulated to unstimulated heart=decrease in HR 3. showed chemical nature at synapse |
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Sherrington, reflex arcs, inferred "the synapse"
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1. behavioral experiments on leg withdrawal reflexes
2. reflex complete with only spinal cord 3. delay when impulse went through reflex arc 4. temporal and spatial summation 5. excitation and inhibition (antagonistic muscles) 6. later studied by Eccles using physiology |
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Electron microscopy
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direct visualization of synapse
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Basic types of Synapsess?
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a. axosomatic, axodendritic, axoaxonic, dendrodendritic
b. terminal vs. "en passant" |
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Size of synapse?
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(~20 nm across) and structure
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presynaptic terminal
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vesicles and specializations for NT release
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electrical synapses
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a. direct connection between cells' cytoplasm
b. through gap junctions c. only small molecules pass through d. can open and close=regulated |
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postsynaptic elements
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receptors, transporters, postsynaptic density
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release of neurotransmitter -voltage dependence
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a. action potential depolarizes axon terminal
b. voltage gated calcium channels |
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release of neurotransmitter -Ca++ dependence
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Ca binds to other proteins, triggers cascade of events that result in release
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release of neurotransmitter- vesicles and machinery
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a. 2 major classes of vesicles-small clear and larger dense-core
b. small clear-"regular" neurotransmitter dense-core-peptides, secretory |
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inactivation and uptake of neurotransmitters-how is neurotransmitter response
terminated? |
1. mostly by uptake of NT into terminals and glia
2. acetylcholine is cleaved by acetylcholinesterase and then the products are taken up 3. desensitization |
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ionotropic response
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NT causes opening of gated ion channel; ion flow through channel mediates response
i. type of response depends on which ions pass through channel-the same NT can cause different responses via different ion channels ii. rapid, short-acting responses (EPSPs, IPSPs) |
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metabotropic response
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NT binding causes activation of a G-protein which causes changes in other second messenger molecules which in turn affect other processes (ion channels, gene expression, phosphorylation, etc.)
i. generally slower, longer lasting responses (modulation) |
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excitatory postsynaptic potentials (EPSPs)
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depolarize neuron, make it more likely to fire action potentials
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inhibitory postsynaptic potentials (IPSPs)
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hyperpolarize neuron, make it less likely to fire action potentials
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presynaptic receptors
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on synaptic terminals
a. allow control of NT release=gain control at synapse b. can also affect NT synthesis=long term regulation of synapse |
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Why synapses?
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a .ability to integrate information (excitatory and inhibitory)at a single neuron effectively
b. opportunities for gain control and modulation of information c. e.g. memory storage |
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temporal and spatial summation
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a. "effectiveness" of a synapse depends crucially on location with respect to action potential initiation zone
b. single synapse activation not likely to cause spiking=need summation c. summation in time (temporal) and space (spatial) |
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integration and the “decision” to fire
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a. neurons can be viewed as "integrate and fire" elements
b. summation of all inputs at spike initiation zone c. local signals(PSPs) and long distance signals (APs) |
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agonists
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bind to receptors and activate them
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antagonists
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block receptors
a. competitive-directly compete with binding of natural agonist b. non-competitive-decrease activity of receptor, not by competition |
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ligand
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binds to a given molecule
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acetylcholine
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1. ionotropic-nicotinic (nicotine=agonist)
a. generally excitatory b. in PNS-released by motorneurons, cause muscle contraction c. in CNS-modulation? 2. metabotropic-muscarinic (muscarine=agonist) |
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amino acids
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1. glutamate-most common excitatory neurotransmitter in CNS
a. ionotropic i. AMPA -rapid excitation, "normal" transmission ii. NMDA -unusual ion channel a. gated by glutamate and depolarization=coincidence detection? b. passes calcium into neuron c. important for learning, development, toxicity b. metabotropic |
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GABA (gamma-amino butyric acid)
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dominant inhibitory NT in brain
a. ionotropic and metabotropic receptors b. prevents "runaway" excitation c. block of GABA can cause epilepsy d. sedation 3. glycine-dominant inhibitory NT in spinal cord |
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monoamines
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single amine group
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catecholamines
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Is a monamine
a. synthesized from tyrosine (amino acid)->L-Dopa->dopamine ->norepinephrie->epinephrine i. pathway important for Parkinson's disease therapy |
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dopamine
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Is a monamine
i. involved in reinforcement/addiction, voluntary movement ii. deficit in dopamine in basal ganglia leads to Parkinson's |
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norepinephrine
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Is a monamine
i. NT in CNS-arousal/modulation/learning? |
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epinephrine
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Is a monamine
i. released from adrenal gland activates sympathetic NS: "fight or flight" response |
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indoleamines
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serotonin
a. synthesized from tryptophan (amino acid) |
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peptides
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short chains of amino acids (proteins are long chains of amino acids)
1. require protein synthesis machinery a. in nucleus (maybe in nerve terminals) 2. generally modulatory (metabotropic) |
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endorphins
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a. opiates (morphine, heroin) are agonists at these receptors
b. first peptide receptor isolated |
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Dale's principal
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a neuron releases one neurotransmitter type at all of its terminals.
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other possible neurotransmitters
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1. cannabinoids (marijuana)-anandamide
2. nitric oxide and carbon monoxide a. membrane permeable gases b. synthesized and released in terminal due to depolarization c. "paracrine" role? |
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neurotransmitter receptor diversity
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NTs have multiple receptor subtypes with differing effects and agonists/antagonists
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Drugs of abuse
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Alcohol: potentiates GABA receptors
Nicotine: nicotinic acetylcholine agonist Marijuana (THC): cannabinoid receptor agonist Opiates (heroin, vicodin, percocet): opiate receptor agonists Cocaine: blocks catecholamine reuptake LSD: serotonin receptor agonist Amphetamines (methamphetamine, ecstacy): blocks catecholamine reuptake, induces catecholamine release PCP (phencyclidine): NMDA receptor antagonist, nicotinic antagonist |
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Psychiatric agents
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Antidepressants (tricyclics, SSRI’s): block catecholamine (serotonin) reuptake, some potentiate GABA
Antipsychotics: dopamine receptor (D2) antagonists Sedatives, anesthetics (valium, alcohol, ketamine): potentiate GABA receptors, some block histamine receptors Anxiolytics: various-potentiate GABA, block catecholamine reuptake |
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addiction, self medication
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1. addiction obviously is a complex behavioral/psychological phenomenon
2. chronic drug intake leads to long-term effects on the affected NT system and on other NT systems (homeostasis)\ 3. For example chronic presence of an agonist (stimulates NT receptors) often leads to decreases in the release of the NT or in the sensitivity of NT receptors. 4. withdrawal reflects these chronic changes 5. self-medication |
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Central nervous system (CNS)
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1. brain and spinal cord
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Peripheral nervous system (PNS)
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1. somatic-voluntary movement and sensation
2. autonomic-involuntary control of internal state 3. enteric-neural control of digestion |
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Forebrain
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largest division of human brain, expanded in primate evolution
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Cerebral cortex (neocortex)
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"higher-order” behaviors, esp large in humans
a. gyri (ridges) and sulci (valleys) or fissures (large sulci) increase cortical area per unit volume (packing density). b. cortical layers-six layers (or lamina) from surface of cortex i. define the basic flow of information through the cortex c. cortical columns-small area of cortex containing neurons that perform a similar function. The basic functional units across cortex. Are organized into “maps” in many places. |
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Cortical lobes
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cortex divided by two major fissures (central and lateral) into 4 lobes
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frontal lobe
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motor and “association” areas
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parietal lobe
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somatosensory, visual (higher-order), association
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temporal lobe
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auditory, visual (higher-order), language, association
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occipital
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primary visual cortex, association
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Laterality
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2 cerebral hemispheres not identical in function
a. crossings-corpus callosum b. anatomical and functional asymmetries |
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"Limbic system”-
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cortical and subcortical structures around lateral ventricle. interconnected with cortex esp temporal and frontal. Structures associated particularly with memory and emotion.
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Hippocampus
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involved in learning and memory, complex associations, “space” cognition
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amygdala
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medial temporal nucleus-associated with emotion, especially fear and anxiety
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hypothalamus and pituitary gland
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ventral part of the diencephalon (see below); very complex nuclei. Important for internal state control (hunger, thirst, etc.)
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basal ganglia
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important for voluntary movement planning and execution
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Thalamus
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contains specific nuclei associated with each sensory system (except olfaction)
i. “relay” to cortex vs. thalamo-cortical-thalamus processing loop |
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Midbrain- tectum
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1. inferior colliculus-auditory nucleus, sound localization
2. superior colliculus-impt for eye movements and gaze control |
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Midbrain- tegmentum
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1. midbrain reticular formation-arousal, general activation of cortex
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Hindbrain- pons
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“bridge” major relay for cortex to and from cerebellum
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Hindbrain - medulla oblongata
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an enlargement of the spinal cord, controls many involuntary/automatic functions including swallowing, chewing, breathing, heart rate, etc.
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Spinal Cord
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divided into cervical, thoracic, lumbar, sacral divisions
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gray matter
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contains cell bodies. Contains reflex arcs and central pattern generators.
1. dorsal horn-receives sensory input from peripheral nerves via dorsal root ganglia. 2. ventral horn-has cells bodies of motor neurons B. white matter-myelinated sensorimotor axons |
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cranial nerves
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12 pairs of sensorimotor nerves
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spinal nerves
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31 pairs
1. dorsal root ganglia-cell bodies of sensory nerves 2. ventral horn-motor |
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parasympathetic nervous system
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a. cholinergic
b. activated by descending nerves from cranial nerves and other c. tends to increase energy conservation |
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Sympathetic nervous system
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a. paired chains of ganglia adjacent to spinal cord
b. release epinephrine c. generally increases energy utilization “fight or flight” |
