Exam 1 Flashcards
Brain Lobes
Lobes:
Names of folds on brain
- gyri
- sulci
- fissures
Bell and Magendie
Dorsal and ventral roots carry information in opposite directions
Galen
- Cerebrum = sensation
- cerebellum = motor
- ventricles = ‘communicating fluids’
Hippocrates
Believed the brain was the seat of intelligence and involved in sensation.
–Charles Bell
- Cerebellum: Origin of the motor fibers
- Cerebrum: Destination of sensory fibers
–Marie-Jean-Pierre Flourens
•Experimental ablation method
–Paul Broca
•Discrete region of the human cerebrum for speech
–Franz Joseph Gall
•Phrenology: Bumps on the surface of skull reflect brain surface and related personality traits
SUPER WRONG
Goal of neuroscience
•To learn how the nervous system functions
–Brain’s activity reflected in behavior
–Computer-assisted imaging techniques
–New treatments for nervous system disorders
–Non-invasive methods
– Experiments in live tissue
–Levels of analysis
- Molecular
- Cellular
- Systems
- Behavioral
- Cognitive
Glia
Insulates, supports, and nourishes neurons
–Neurons
- Process information
- Sense environmental changes
- Communicate changes to other neurons
- Command body response
–The Nissl Stain
•Facilitates the study of cytoarchitecture in the CNS
•Golgi-stain (Developed by Camillo Golgi) shows two parts of neurons:
–Soma and perikaryon
–Neurites: Axons and dendrites
•Differences between the cytoplasm of axon terminal and axon
- No microtubules in terminal
- Presence of synaptic vesicles
- Abundance of membrane proteins
- Large number of mitochondria
•Classification Based on Dendritic and Somatic Morphologies
–Stellate cells (star-shaped) and pyramidal cells (pyramid-shaped)
–Spiny or aspinous
Classification based on –Based on axonal length
- Golgi Type I (projection neurons)
- Golgi Type II (local interneurons)
•Astrocytes
–Most numerous glia in the brain
–Fill spaces between neurons
–Influence neurite growth
–Regulate chemical content of extracellular space
•Myelinating Glia
–Oligodendroglia (in CNS)
–Schwann cells (in PNS)
–Insulate axons
4 Important points Equilibrium Potentials
- Large changes in Vm
- Miniscule changes in ionic concentrations(Q=CV)
- Net difference in electrical charge
- Inside and outside membrane surface
- Rate of movement of ions across membrane
- Proportional Vm – Eion
- Concentration difference known: Equilibrium potential can be calculated
–Inside positively charged relative to outside
The Nernst Equation
E =61.5 mV log ([Ion]o /[Ion]i)
• The Distribution of Ions Across The Membrane
–K+ more concentrated on inside, Na+ and Ca2+ more concentrated outside
Na-K Pump
Ca2+ pump actively pumps calcium out of cell
Membrane @ Rest
–Selective permeability of potassium channels - key determinant in resting membrane potential
–Resting membrane potential is close to EK because it is mostly permeable to K+
–Membrane potential sensitive to extracellular K+
–Increased extracellular K+ depolarizes membrane
–Oscilloscope to visualize an AP
image
The Action Potential, In Theory
- Depolarization (influx of Na+) and repolarization (efflux of K+)
- Membrane Currents and Conductances
–Current
•The net movement of K+ across membrane
–Potassium channel number
•Proportional to electrical conductances
–Membrane potassium current
•Flow and driving force
–Hodgkin and Huxley
- Voltage Clamp: “Clamp” membrane potential at any chosen value
- Rising phase à transient increase in gNa, influx of Na+ ions
- Falling phase à increase in gK, efflux of K+ ions
Existence of sodium
–Functional Properties of the Sodium Channel
- Open with little delay
- Stay open for about 1 msec
- Inactivation: Cannot be opened again by depolarization
–Potassium vs. sodium gates
- Both open in response to depolarization
- Potassium gates open later than sodium gates
–Delayed rectifier
•Potassium conductance serves to rectify or reset membrane potential
–Structure: Four separate polypeptide subunits join to form a pore
•Factors Influencing Conduction Velocity
–Spread of action potential along membrane
•Dependent upon axon structure
–Path of the positive charge
- Inside of the axon (faster)
- Across the axonal membrane (slower)
–Axonal excitability
- Axonal diameter (bigger = faster)
- Number of voltage-gated channels
–Myelin: Layers of myelin sheath facilitate current flow
- Myelinating cells
- Schwann cells in the PNS
- Oligodendroglia in CNS
CNS Synapses
–Axodendritic: Axon to dendrite
–Axosomatic: Axon to cell body
–Axoaxonic: Axon to axon
–Dendrodendritic: Dendrite to dendrite
–Gray’s Type I: Asymmetrical, excitatory
–Gray’s Type II: Symmetrical, inhibitory
Principles of Chemical Synaptic Transmission
–Neurotransmitter synthesis
–Load neurotransmitter into synaptic vesicles
–Depolarization à Vesicles fuse to presynaptic terminal
–Neurotransmitter spills into synaptic cleft
–Binds to postsynaptic receptors
–Biochemical/Electrical response elicited in postsynaptic cell
–Removal of neurotransmitter from synaptic cleft
Neurotransmitters
–Amino acids: Small organic molecules
•e.g., Glutamate, Glycine, GABA
–Amines: Small organic molecules
•e.g., Dopamine, Acetylcholine, Histamine
–Peptides: Short amino acid chains (i.e. proteins) stored in and released from secretory granules
•e.g., Dynorphin, Enkephalins
•Neurotransmitter Synthesis and Storage
image
•Neurotransmitter Release ()
–Mechanisms
- Process of exocytosis stimulated by release of intracellular calcium, [Ca2+]i
- Proteins alter conformation - activated
- Vesicle membrane incorporated into presynaptic membrane
- Neurotransmitter released
- Vesicle membrane recovered by endocytosis
•Neurotransmitter receptors:
–Ionotropic: Transmitter-gated ion channels
Metabotropic: G-protein-coupled receptor
•Excitatory and Inhibitory Postsynaptic Potentials:
- EPSP:Transient postsynaptic membrane depolarization by presynaptic release of neurotransmitter
- IPSP: Transient hyperpolarization of postsynaptic membrane caused by presynaptic release of neurotransmitter
•Neurotransmitter Recovery and Degradation
–Diffusion: Away from the synapse
–Reuptake: Neurotransmitter re-enters presynaptic axon terminal
–Enzymatic destruction inside terminal cytosol or synaptic cleft
–Desensitization: e.g., AChE cleaves Ach to inactive state (to prevent desensitization)
Neuropharmacology
–Effect of drugs on nervous system tissue
–Receptor antagonists: Inhibitors of neurotransmitter receptors
•Curare
–Receptor agonists: Mimic actions of naturally occurring neurotransmitters
•Nicotine
–Defective neurotransmission: Root cause of neurological and psychiatric disorders
•EPSP Summation
–Allows for neurons to perform sophisticated computations
–Integration: EPSPs added together to produce significant postsynaptic depolarization
–Spatial: EPSP generated simultaneously in different spaces
–Temporal: EPSP generated at same synapse in rapid succession
•IPSPs and Shunting Inhibition
–Excitatory vs. inhibitory synapses: Bind different neurotransmitters, allow different ions to pass through channels
–Membrane potential more negative than -65mV = hyperpolarizing IPSP
•Shunting Inhibition: Inhibiting current flow from soma to axon hillock
•The Spinal Cord
–Conduit of information (brain body)
- Skin, joints, muscles
- Spinal nerves
- Dorsal root
- Ventral root
•Catecholaminergic Neurons
–Involved in movement, mood, attention, and visceral function
–Tyrosine:
– Precursor for three amine neurotransmitters that contain catechol group
- Dopamine (DA)
- Norepinephrine (NE)
- Epinephrine (E, adrenaline)
•Serotonergic (5-HT) Neurons
–Amine neurotransmitter
•Derived from tryptophan
–Regulates mood, emotional behavior, sleep
•Selective serotonin reuptake inhibitors (SSRIs) - Antidepressants
–Synthesis of serotonin
•The Basic Structure of Transmitter-Gated Channels
–Pentamer: Five protein subunits
(except glutamate receptors- tetramer)
Glutamate-Gated Channels
–Glutamate-Gated Channels
•AMPA, NMDA, kainite
–Voltage dependent NMDA channels
–GABA-Gated and Glycine-Gated Channels
- GABA mediates inhibitory transmission
- Glycine mediates non-GABA inhibitory transmission
- Bind ethanol, benzodiazepines, barbiturates
–Five steps in G-protein operation
- Inactive: Three subunits - a, b, and g - “float” in membrane (a bound to GDP)
- Active: Bumps into activated receptor and exchanges GDP for GTP
- Ga-GTP and Gbg - Influence effector proteins
- Ga inactivates by slowly converting GTP to GDP
- Gbg recombine with Ga-GDP
•Tastes Receptor Cells
–Apical endsà Microvillià Taste pore
–Receptor potential: Voltage shift
•Mechanisms of Taste Transduction
–Saltiness
- Salt-sensitive taste cells
- Special Na+ selective channel
- Blocked by the drug amiloride
- Serotonin released (new)
•Mechanisms of Taste Transduction
–Sourness
- Sourness- acidity – low pH
- Protons causative agents of acidity and sourness
- Depolarize by Blocking K channels, pass through amiloride-sens Na channels
•Mechanisms of Taste Transduction
–Bitterness
- Families of taste receptor genes – T1R and T2R
- Block K channels (e.g., quinine), Bind to G-protein coupled receptors (T2R class).
- ATP = Transmitter (new)
•Mechanisms of Taste Transduction
–Umami
- Umami receptors:
- Detect amino acids
- T1R1+T1R3
- Ionotropic & metabotropic
•Central Taste Pathways
–Localized lesions
•Ageusia- the loss of taste perception
–Gustation
- Important to the control of feeding and digestion
- Hypothalamus
- Basal telencephalon
–Olfactory epithelium
• Olfactory receptor cells, supporting cells, and basal cells
–Olfactory Transduction
decreased response despite continued stimulus.
•Central Olfactory Pathways (Cont’d)
–Axons of the olfactory tract: Branch and enter the forebrain (pyriform cortex)
–Neocortex: Reached by a pathway that synapses in the medial dorsal nucleus
•Gross Anatomy of the Eye
–Pupil: Opening where light enters the eye
–Sclera: White of the eye
–Iris: Gives color to eyes
–Cornea: Glassy transparent external surface of the eye
–Optic nerve: Bundle of axons from the retina
•Cross-Sectional Anatomy of the Eye
•Direct (vertical) pathway:
–Ganglion cells
–Bipolar cells
–Photoreceptors
•Retinal processing also influenced lateral connections:
–Horizontal cells
•Receive input from photoreceptors and project to other photoreceptors and bipolar cells
–Amacrine cells
•Receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells
•Photoreceptor Structure
–Converts electromagnetic radiation to neural signals
–Four main regions
- Outer segment
- Inner segment
- Cell body
- Synaptic terminal
–Types of photoreceptors
• Rods and cones
•On-center Bipolar Cell
–Light on (less glutamate); Light off -> more glutamate
•M-type (Magno) and P-type (Parvo)ganglion cells in monkey and human retina
•The Optic Nerve, Optic Chiasm, and Optic Tract
•Right and Left Visual Hemifields
field errors
The Lateral Geniculate Nucleus (LGN)
•Inputs Segregated by Eye and Ganglion Cell Type
Anatomy of the Striate Cortex
•Lamination of the Striate Cortex
–Layers I - VI
–Spiny stellate cells: Spine-covered dendrites; layer IVC
–Pyramidal cells: Spines; thick apical dendrite;
layers III, IVb, V, VI
–Inhibitory neurons: Lack spines; All cortical layers; Form local connections
•Inputs to the Striate Cortex binocular
–First binocular neurons found in striate cortex - most layer III neurons are binocular (but not layer IV)
•Outputs of the Striate Cortex:
–Layers II, III, and IVB: Project to other cortical areas
–Layer V: Projects to the superior colliculus and pons
–Layer VI: Projects back to the LGN
Orientation Selectivity
Parallel Pathways: Magnocellular; Koniocellular; Parvocellular
