Nervous System Flashcards
Synapse type
Chemical
Synapse type
Electrical
Type of autonomic nervous system
sympathetic
Type of autonomic nervous system
parasympathetic
Action potential
Membrane potential of -70 mV. At rest K+ ions are concentrated inside of the cell and Na+ ions are outside, due to greater membrane permeability for K+.
The concentration gradients are maintained by Na+-K+ pump which moves 3 Na+ from inside to outside and 2 K+ from outside to inside per unit of ATP.
Resting membrane potential
Action potential
Upon reaching threshold potential, Na+ ions move inside of the cell through voltage-gated Na+ channels.
Peaks at +30 mV.
Depolarization
Action potential
Occurs as K+ ions move outside of the cell.
Returns membrane potential in direction of resting potential.
Repolarization
Action potential
Cell “overshoots” its resting membrane potential because of delayed closing of K+ channels.
While returning to resting state, cell is in a refractory period and cannot fire.
Hyperpolarization
Support cells which surround neurons. Can replicate (unlike neurons).
Glial cells
Glial cells.
Help form the blood-brain barrier. Regulate solute and ion balance.
Astrocytes
Glial cells.
Form lining between cerebrospinal fluid (CSF) and interstitial fluid.
Ependymal cells
Glial cells.
Immune cell. Functions to break down waste and repair damage.
Microglia
Schwann cells versus oligodendrocytes
Both coat axons with myelin
Oligodendrocytes: myelinate many cells in the central nervous system (CNS)
Schwann cells: myelinate the axon of one cell in the peripheral nervous system (PNS)
Mnemonic: COPS drive fast like myelin. CNS Oligodendrocytes PNS Schwann cells.
Neuron structure and pathway
Signals are conducted through the axon, causing neurotransmitter release in the synapse.
The neurotransmitter binds to receptors on the dendrites of another neuron, altering the electric potential of the cell body of that neuron.
White vs grey matter
White matter is myelinated and consists of axons.
Grey matter is unmyelinated and consists of cell bodies and dendrites.
Transmission of action potentials in myelinated neurons is called saltatory conduction and runs through Nodes of Ranvier.
Myelinated transmission
Prevents passage of toxins into brain. At the cellular level is made of astrocytes and held together by tight junctions.
Small, hydrophobic molecules can pass through it.
blood brain barrier
Action potentials are “all-or-nothing.” They can be triggered by temporal or spatial summation of neurotransmitters.
temporal vs spatial summation
Temporal summation
Multiple excitatory signals from a single neuron sum together to trigger a threshold action potential.
Spatial summation
Excitatory signals from many neurons sum together to trigger a threshold action potential.
Neurotransmitter at neuromuscular junction
Primary neurotransmitter at NMJ is acetylcholine.
Inhibitory neurotransmitters
Primary inhibitory neurotransmitter in brain is GABA.
Primary inhibitory neurotransmitter in spinal cord is glycine.
Excitatory neurotransmitters
Primary excitatory neurotransmitter in the central nervous system is glutamate.
Synaptic release of neurotransmitters
Calcium influx triggers neurotransmitter release into the synaptic cleft.
Neurotransmitters are often released in vesicle form through exocytosis.
Afferent vs efferent neurons
Mnemonic: Afferent and efferent sound the SAME. Sensory Afferent Motor Efferent.
Afferent
Carries sensory information from receptors to the spinal cord and up to the brain.
Efferent
Carries motor signals from CNS to muscles.
Think efferent = effect.
Transmit signals between other neurons, important part of the reflex arc.
Interneurons
Reflex arc pathway
Sensory neuron → interneuron (in spine) → motor neuron.
Simultaneously can transmit info to brain or be modulated by signals from brain.
