Brain Organization and Neural Functioning Flashcards
Golgi vs. Rámon y Cajal
Golgi: Neurons are continuous
Rámon y Cajal: Neurons come close to one another but are not connected
Neuron Doctrine
The brain is composed of separate cells that are distinct structurally, metabolically and functionally
Sir Charles Sherrington
Termed the synpase
Multipolar Neuron
A nerve cell that has many dendrites and a single axon
Bipolar Neuron
A nerve cell that has a single dendrite at one end and a single axon on the other end
Neural Plasticity
The ability of the nervous system to change in response to experience or the environment
Glial Cells
Glial cells support and enhance neural activity: they communicate with each other and with neurons, and they directly affect neuronal functioning by providing neurons with raw materials and chemical signals that alter neuronal structure and excitability.
Make up myelin
Myelin/Myelination
The fatty insulation around an axon formed by glial cells, that improves the speed of conduction of nerve impulses.
Less myelin = action potential
Peripheral Nervous System
All nervous system parts that are outside the bony skull and spinal column
Central Nervous System
Consists of the brain and spinal cord
Dorsal
Towards the back
Ventral
Toward the belly, front
Anterior
Head
Posterior/Caudal
Back
Parasympathetic Nervous System
Helps the body relax, recuperate, and prepare for future action (Uses Acetylcholine)
Sympathetic Nervous System
Prepares the body for action (Uses Norepinephrine)
Corpus Callosum
The main band of axons that connects the two cerebral hemispheres
White Matter
A shiny layer underneath the cortex that consists largely of axons with white myelin sheaths
The Limbic System
Critical for emotion and learning Includes: Amygdala Hippocampus Fornix
Hippocampus
A medial temporal lobe structure that is important for learning and memory
Thalamus
A complex cluster of nuclei that acts as a switch box, directing almost all incoming sensory information to the appropriate regions of the cortex for further processing.
Hypothalamus
Packed with discrete nuclei, it is involved in many functions such as hunger, thirst, temperature regulation. It also controls the pituitary gland serving as the brains main interface with the hormonal system.
The Ventricular System
A system of fluid-filled chambers inside the brain
Includes:
Lateral Ventricle- The lateral portion of the VS system within each hemisphere of the brain
Third Ventricle- The midline ventricle that conducts cerebrospinal fluid from the lateral ventricle to the fourth ventricle
Fourth Ventricle- The passageway within the pons that receives cerebrospinal fluid from the third ventricle and releases it to surround the brain and spinal cord.
All living cells are more (positive/negative) on the inside…
Negative
Ion
An electrically charged molecule
Resting Membrane Potential
An electrical-potential difference across the membrane. Usually of about -50 to -80 mV
Potassium Ion (K+)
Carries a positive charge
Concentration Gradient
Variation of the concentration of a substance within a region
Sodium Ion (Na+)
Carries a positive charge
Sodium Ion Pump
Pumps three Na+ out for every two K+ in
The Nernst Equation
Predicts the voltage needed to counterbalance the diffusion force pushing an ion across a semipermeable membrane from the side with a high concentration to the side with a low concentration
Hyperpolarization
An increase in membrane potential (i.e the neuron becomes more negative on the inside, relative to the outside) (INHIBITORY)
Depolarization
A reduction in membrane potential (i.e the interior of the neuron becomes less negative by letting in Na+) (EXCITATORY)
Local Potentials
An electrical potential that is initiated by simulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance.
Threshold
The stimulus intensity that is just adequate to trigger an action potential (about -40 mV)
Action Potential
A rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside.
Applying strong stimuli to action potentials
Larger depolarizations produce more action potentials, not larger action potentials
The size (or amplitude) of the action potential is independent of stimulus magnitude.
All-or-None Property
Either it fires at its full potential or it does not fire at all
Hodgkin and Huxley
Established that the action potential is created by the movement of sodium ions (Na+) into the cell, through channels in the membrane.
Action Potential
At its peak, the AP approaches equilibrium potential for Na+ as predicted by the Nernst Equation (about +40mV)
The concentration gradient is balanced between negative and positive ions
The membrane shifts properties, now depending on sodium, then returning to the resting state
Voltage-Gated Na+ Channels
A Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential; it mediates the action potential
Axon Hillock
A cone-shaped area from which the axon originates out of the cell body. Functionally, the integration zone of the neuron
Nodes of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed.
Neurotransmitter
A converted electrical signal, released from the presynaptic axon terminal that serves as the basis of communication between neurons
EPSP
A depolarizing potential in the postsynaptic neuron that is caused by excitatory connections. EPSPs increase the probability that the post synaptic neuron will fire an action potential
IPSP
A hyper polarizing potential in the post synaptic neuron that is caused by inhibitory connections. IPSPs decrease the probability that the postsynaptic neuron will fire an action potential
Synaptic Transmission
- Action potential arrives at the axon terminal
- This depolarization opens voltage-gated calcium channels in the membrane, allowing calcium (Ca2+) to enter
- Ca2+ causes synaptic vesicles filled with neurotransmitters to fuse with the presynaptic cell
- The NTs are released into the synaptic cleft
- Transmitter molecules cross the cleft to bind with special receptors, leading to the opening of ion channels in the postsynaptic membrane.
- This creates an EPSP or an IPSP
- EPSP and IPSPs spread and determine if there will be another action potential
Calcium Ions (Ca2+)
Activate enzymes that cause vesicles near the presynaptic membrane to fuse with the membrane and discharge their contents into the synaptic cleft.
Ligand
A substance that binds the receptor molecules, such as those at the surface of the cell.
Agonist vs Antagonist
Agonist: A molecule, usually a drug, that binds a receptor molecule and initiates a response like that of another molecule, usually a NT
Antagonist: A molecule that interferes with or prevents the action of a transmitter
Loewi
Discovered the nervous system, long known to use electrical signals, uses chemical signals as well
Discovered ACh
Ionotropic Receptor
A receptor protein that includes an ion channel that is opened when the receptor is bound by an agonist
Ligand-Gated Ion Channel
Also known as chemically gated ion channel
An ion channel that opens or closes in response to the presence of a particular chemical
Metabotropic Channel
A receptor protein that does not contain an ion channel but may, when activated, use a G protein system to alter functioning of the postsynaptic cell
Degradation
When a transmitter is broken down and thus inactivated
Reuptake
The process by which released synaptic transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity.