exam 1 Flashcards
What does it mean for a neuron to be inhibitory or excitatory?
Excitatory neurons increase the likelihood of an action potential in the postsynaptic neuron. Inhibitory neurons decrease the likelihood of an action potential.
What neurotransmitter is the main excitatory NT in the CNS?
Glutamate.
What neurotransmitters are associated with inhibitory neurons?
GABA and glycine.
What is the role of neural balance between excitation and inhibition?
Prevents excessive activity (e.g., epilepsy).
What comprises the CNS?
CNS (Central Nervous System): Brain (Cerebrum, cerebellum, brainstem) and spinal cord.
What comprises the PNS?
PNS (Peripheral Nervous System): Cranial nerves & spinal nerves.
What are the divisions of the PNS?
Sensory division (afferent) sends info to CNS; Motor division (efferent) carries commands from CNS.
What is the somatic nervous system responsible for?
Voluntary control (skeletal muscles).
What is the autonomic nervous system responsible for?
Involuntary control (sympathetic & parasympathetic).
What structure relays information between the brain and periphery?
The spinal cord serves as the primary relay center.
What types of processing occur in the parietal and occipital lobes?
Somatosensory processing occurs in the parietal lobe; Visual processing occurs in the occipital lobe.
How does motor information travel from the brain to peripheral structures?
Descending motor pathways carry signals from CNS to muscles.
What is the corticospinal tract?
A major pathway for voluntary movement that exits via ventral roots of spinal nerves.
What is the difference between white matter and gray matter?
White matter consists of myelinated axons that transmit signals quickly; Gray matter consists of cell bodies, dendrites, and unmyelinated axons responsible for processing.
What is the cerebrum?
The largest and most rostral (front-most) brain structure responsible for higher functions: thought, perception, voluntary movement.
What types of cells make myelin sheaths?
CNS: Oligodendrocytes; PNS: Schwann cells.
What do astrocytes do?
Maintain blood-brain barrier, regulate neurotransmitters & synaptic activity, provide metabolic support & respond to injury.
What structure do myelin sheaths wrap around?
Axons (to speed up conduction).
Do glial cells generate action potentials?
No, only neurons generate action potentials.
What are dendritic spines?
Small protrusions on dendrites that receive synaptic input and are postsynaptic sites for excitatory neurotransmission.
What is synaptogenesis?
Formation of new synapses.
What is gliogenesis?
Formation of glial cells.
What is neurogenesis?
Formation of new neurons.
What is synaptic pruning?
Elimination of weak synapses.
What happens when a glial scar forms in the CNS?
Forms after CNS injury to limit damage, made of reactive astrocytes, microglia, and oligodendrocytes.
How does information travel in a neuron?
Dendrites → Soma (cell body) → Axon → Axon terminals.
What is the resting potential of a neuron?
Around -70mV, maintained by Na+/K+ pump and ion channel permeability.
How do ions move across the plasma membrane?
Passive diffusion (ion channels) and active transport (ion pumps).
What determines the equilibrium potential of an ion?
Calculated using Nernst equation, achieved when electrical & chemical forces are balanced.
What are the phases of an action potential?
Depolarization (Na+ influx), Repolarization (K+ efflux), Hyperpolarization (Excess K+ outflow).
What is saltatory conduction?
AP jumps between Nodes of Ranvier, speeding up conduction.
What are Nodes of Ranvier?
Unmyelinated gaps in myelin sheath; sites of ion exchange.
What limits the maximal firing rate of neurons?
Absolute & relative refractory periods.
Absolute refractory period: Na+ channels inactivated, no AP possible.
Relative refractory period: AP possible but requires stronger stimulus.
Where do action potentials typically start?
At the axon hillock (high concentration of voltage-gated Na+ channels).
How many neurons and glial cells are in the brain?
~86 billion neurons, equal or more glial cells.
What determines the size of an action potential?
All-or-nothing principle: AP size is constant, but frequency varies.
What is the role of Na+/K+ ATPase?
Maintains resting potential by pumping 3 Na+ out, 2 K+ in.
Why is K+ equilibrium potential (EK+) close to resting potential?
Membrane is highly permeable to K+ at rest, making EK+ a major determinant of resting potential.
