Neuroscience Exam 1

Reticular Theory

Nerves communicate through a continuous nerve net

Neuron Doctrine

The nervous system is made up of discrete, individual cells

Central Nervous System

Made up of the brain and spinal cord, protected inside bones

Peripheral Nervous System

Cranial and spinal nerves, extends beyond the bony skull and vertebral column

Dynamic Polarity

Electrical signals within a neuron flow in one direction

Dendrites

Receive input

Some

Important for integration of signal

Axon

Important for signal propagation

Axon Terminal

Site of signal output

Synaptic Vesicle

Contain, store, and release neurotransmitters

Ecto/Endosome

Deliver proteins to plasma membrane (ecto) and remove proteins from the plasma membrane (endo)

Lysosome

Breakdown waste and debris

Dendrites and Spines

Number of dendritic branches correlates with the number of inputs, spines increase the number of input locations

Axons

Propagate electrical signals between neurons, form presynaptic terminals of synapses

Myelin

Wraps axons like insulation to keep electricity from escaping

Nodes of Ranvier

Breaks in myelin with concentrated channels

Sensory Receptor Neurons

Change sensory input into electrical signals

Projection Neurons

Communicate with other neurons located in a different or distant CNS regions (between brain areas, between spinal cord and sensor/motor stuctures)

Interneurons

Communicate with other neurons located in the same or nearby CNS region

Glial Cells

Support system for neurons, more numerous than neurons

Astrocytes

Restricted to CNS, help maintain the proper extracellular chemical environment necessary for neural signaling, comprise the blood brain barrier

Oligodendrocytes

In the CNS, myelinate several parts of several axons

Schwann Cells

In the PNS, each cell myelinates one part of a single PNS axon

Microglia

Scavenger cells that remove debris from sites of injury, modulate inflammation, cell survival, and cell death, very plastic

Meninges

3 layers of tissues provide protection to the brain and spinal cord

Dura mater

Outermost meninges layer, tough and leathery

Arachnoid mater

Middle meninges layer, fairly delicate and impermeable. Separated from the dura by subdural space and from the pia by the subarachnoid space (filled with cerebrospinal fluid)

Pia mater

Innermost meninges layer, adheres to the surface of the brain, appears glossy and is so thin it is almost invisible to the naked eye

Ventricular System

Cerebrospinal fluid is derived from the choroid plexus on the walls of ventricles

CSF leaves the ventricles through foramina

CSF enters the subarachnoid space

CSF drains into the subdural sinuses then back to the general blood flow

Cerebrospinal Fluid

Needed for brain buoyancy and protection

Hydrocephalus

Results from a block of CSF drainage, can be treated through surgical implantation of a shunt to drain fluid

Concussions

Most often caused by blows to the head, result in temporary disorientation or short-term memory loss

Blood-Brain Barrier

Protects the brain from substances in the blood, formed by tight junctions between capitally endothelial cells, anything that is both small and lipid-soluble for which specific transporters exist can get through

Circumventricular Organs

Not protected by the blood-brain barrier, serve to detect presence of toxins in the blood

White Matter

Myelinated axons

Gray Matter

Mostly cell bodies and dendrites

Spinal Cord

Within the vertebral column, transfers information between the CNS and PNS, sensory information enters the dorsal portion and motor commands exit the ventral side

Cranial Nerves

12 pairs, emerge from the brain and send motor commands to and receive sensory information from the head to the neck

Medulla

Neurons that maintain normal, rhythmic breathing

Brainstem

Pons Regions

Allows cerebellum to communicate with the brainstem and the cerebral cortex

Brainstem

Midbrain

Localization of visual and auditory stimuli

Brainstem

Brainstem

Contains sensory and motor axons

Cerebellum

Motor planning and learning

Diencephalon

Thalamus relays information going to and coming from the neocortex, hypothalamus regulates autonomic nervous system and hormone release

Cerebral Cortex (Neocortex)

Processing of sensory input, initiation/planning of movement, memory, cognition, language

Occipital Lobe

Early-stage vision

Cerebral Cortex

Parietal Lobe

Somatosensory, late-stage vision

Cerebral Cortex

Temporal Cortex

Memory, hearing, language comprehension

Cerebral Cortex

Central Sulcus

Separates parietal and frontal lobes

Lateral Fissure

Separates the temporal lobe from those surrounding it

Longitudinal Fissure

Separates the two hemispheres of the brain

Postcentral Gyri

Directs caudal to the central sulcus, contains the primary somatosensory cortex

Precentral Gyri

Directly rostral to the central sulcus, contains the primary motor cortex

Neocortex Layer 4

Receives main input from thalamus

Neocortex Layer 5

Sends projections to other parts of the neocortex and to other brain regions

Limbic System

Sexual behavior, formation of memory, primary reward and punishment centers, site of action of drugs which produce euphoria

Hypothalamus

Regulates many motivates function, sleep/wake cycle, pituitary gland activity

Limbic System

Hippocampus

Memory consolidation and provide the organism’s context

Limbic System

Amygdala

Coordinates autonomic responses with emotional states

Limbic System

Cerebral Cortex

Interacts with subcortical structures to guide behaviors

Limbic System

Basal Ganglia

Controls voluntary, smooth movement

Corpus Collosum

Long-range neurons that connect two halves of the brain

Neurons

Cells that are specialized for the reception, conduction, and transmission of electrochemical signals

Membrane Potential and Current

Inside of the cell is about -70mV relative to the outside, current causes membrane potential to become more positive or negative through movement of ions across the membrane through ion channels

Hyperpolarizaition

Neural potential is (or is becoming) more negative than resting membrane potential

Depolarization

Neural potential is (or is becoming) more positive than resting membrane potential

Conditions for Resting Membrane Potential

No net flux of ions across the membrane

Ions enter and leave the neuron at the same rate

Achieved by the balance of diffusive force and electrical force

Concentration Greater Outside Cell

Na+

Cl-

Concentration Greater Inside Cell

K+

Proteins

Homogenizing Forces

Forces promoting equal distribution of ions across the membrane, concentration gradients and electrostatic pressure

Opposing Forces

Differential permeability, sodium/potassium pump

Diffusion of Ions Across Membrane

Diffusive forces drives ions down the concentration gradient through ion channels, as ions move through they stick to the membrane

Electrostatic Pressure

Force exerted by attraction of oppositely charged ions or by the repulsion of similarly charged ions, promotes even distribution of forces

Differential Permeability

K+ and Cl- pass readily through the resting membrane through leak channels that are always open, Na+ has very few leak channels and membrane is therefore very slightly permeable to it

Sodium-Potassium Pump

Maintains Na+ and K+ concentration gradients

3 Na+ out of neuron for every 2 K+ into neuron, affecting resting membrane potential by making in less negative

Voltage-Gated Ion Channels

Opened and closed by changes in membrane voltage, Na+, K+, Ca2+

Threshold

When action potential becomes all-or-none, Na+ ions enter and depolarize cell opening even more Na+ channels

Upstroke

Strong Na+ influx and weak K+ efflux at low levels of membrane depolarization, net Na+ entry causes depolarization

Downstroke

Strong K+ efflux and weak Na+ influx at high levels of membrane depolarization, net K+ efflux causes repolarization

Afterhyperpolarization

Membrane potential is more negative than at rest, K+ channels are too slow to open and close to the K+ current outlasts the action potential and hyperpolarizes the membrane

Deactivation

Passive recovery from depolarization offset (K+)

Inactivation

Voltage dependent reduction in current before offset (Na+)

Absolute Refractory Period

Occurs when voltage-gated sodium channels are inactivated, it is impossible to generate another action potential no matter how much stimulation is applied

Relative Refractory Period

Time after an action potential when enough sodium channels have recovered from inactivation to trigger an action potential, but potassium efflux is still active and the cell is hyperpolarized, therefore more stimulus is needed to reach the threshold

Saltatory Conduction

Due to high resistance in internodal regions, current jumps (saltare) from node to node

Electrical Synapses

Allow passive flow of current directly though gap junctions

Gap Junctions

Aligned pairs of channels called connexons that create pores for ions to diffuse between the two cells, allow the flow of electrical current in either direction

Chemical Synapses

Transmission through the presynaptic release and postsynaptic binding of neurotransmitters

Synaptotagmin

Vesicle protein that detects calcium and interacts with the SNARE complex to trigger release

Ionotropic Receptors

Ligand gated ion channels, NT binding directly opens/closes channel causes current flow to produce postsynaptic potentials, fast

Metabotropic Receptors

G-protein couples receptors, NT binding indirectly affects ion channels, slow

Glutamate Channels

Permeable to Na+ and sometimes Ca2+, 4 subunits with at least 2 molecularly different types

GABA Receptors

Ligand-gated chloride channel, external binding site for GABA, 5 subunits with at least 2 different types, typically conduct Cl- into cell

GABA A-Type

GABA binding required, permeable to Cl- ions, Inhibitory Postsynaptic Response, Cl- enters cell causing hyperpolarization, fast acting yet short-lived

GABA B-Type

GABA binding required, activate K+ channels through G-protein cascade, Inhibitory Postsynaptic Responses, hyperpolarizing, slow acting yet long-lasting

Spatial Summation

Adding together of inputs over space/location, multiple inputs fired simultaneously will combine efforts and be greater, bringing the neuron closer to action potential threshold

Temporal Summation

Adding together of inputs over time, three firings from same input that occur in rapid succession sum together to have a larger effect

Enzymatic Degradation of Neurotransmitters

Enzymes in the synaptic cleft bind to N molecules and metabolize them into inactive molecules

Reuptake Through Active Transport

Transport proteins on the axon terminal bind to NT molecules in the synaptic cleft and move them back into the presynaptic neuron

Astrocyte Reuptake

Astrocytes express reuptake transporters for glutamate that diffuses out of the synaptic cleft