Section 1
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Synapse (site of impulse propagation between cells)
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Section 1
(50 cards)
Synapse (site of impulse propagation between cells)
Synapse = conduction from one cell to another.
Excitatory and inhibitory nerve fibers (summation, frequency of firing)
Excitatory = stimulates an action potential to occur Excitatory synapse = receptor binding causes postsynaptic potential to be more positive (depolarization) = if it gets above threshold, action potential results. Inhibitory = inhibits an action potential from occuring. Inhibitory synapse = receptor binding causes postsynaptic potential to be more negative (hyperpolarization) = makes it more difficult to reach threshold. Summation = two or more nerves firing at the same time. Two subthreshold excitatory nerves firing at the same time can sum to reach the threshold. A threshold excitatory nerve and an inhibitory nerve firing at the same time, and the resultant signal won't reach the threshold. Frequency = Firing, then quickly firing again. If the first fire is subthreshold, fire again before the previous depolarization dies, and the new depolarization will be even higher than the first time.
Stages of an action potential
Resting: cell at rest, sodium-potassium pump maintaining resting potential (-70 mV). Lots of sodium outside, lots of potassium inside. Ion channels closed so the established ion gradient won't leak. Depolarization: sodium channels open, positive sodium rushes inside, membrane potential shoots up to +30 mV. Lots of sodium inside, lots of potassium inside. Repolarization: potassium channels open, sodium channels close, positive potassium rushes outside, membrane potential drops back down. Lots of sodium inside, lots of potassium outside (opposite of the resting state). Hyperpolarization: potassium channels doesn't close fast enough, so the membrane potential actually drops below the resting potential for a bit. Refractory period: the sodium-potassium pump works to re-establish the original resting state (more potassium inside, sodium outside). Until this is done, the neuron can't generate another action potential. Absolute refractory period = from depolarization to the cell having re-established the original resting state. Relative refractory period = After hyperpolarization till resting state re-established.
motor cortex
an area at the rear of the frontal lobes that controls voluntary movements
glial cells (glia)
cells in the nervous system that support, nourish, and protect neurons
axon hillock
Cone shaped region of an axon where it joins the cell body.
thalamus
the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
limbic system
A doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocampus, amygdala, and hypothalamus.
Oligodendrocytes
the central nervous system analogue of Schwann cells, makes myelin sheath around CNS axons
medulla
the base of the brainstem; controls heartbeat and breathing
Photoreceptors
respond to light; rods and cones
postganglionic neuron
neurons of the autonomic nervous system that form synapses directly with their target organ In the sympathetic nervous system, these neurons secrete epi and nor-epi
Internurons
neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs
information processing model
model of memory that assumes the processing of information for memory storage is similar to the way a computer processes memory in a series of three stages
somatosensory cortex
area at the front of the parietal lobes that registers and processes body touch and movement sensations
Schwann cells
makes myelin sheath in the peripheral nervous system by wrapping around the axon
threshold stimulus
When a stimulus (graded potential) depolarizes above a threshold value, an action potential will occur. Action potentials are all-or-none, meaning that if it occurs, all action potential have the same magnitude. One graded potential just barely makes the threshold value, another overshoots it a lot, but both will cause the same action potential.
K+ leakage
the resting cell membrane has channels that allow K+ to leak out, but don't allow Na+ to leak in = net negative to the inside, net positive to the outside.
cornea
The clear tissue that covers the front of the eye
Summation
increased force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes
Insulation of axon
achieved by the myelin sheath. Insulation occurs in intervals, which causes action potential to jump from one node of Ranvier to the next.
synaptic knobs
Synaptic knob is another name for axon terminal. Contains vesicles of neurotransmitters waiting to be exocytosed. Action potential reaching the synaptic knob causes an influx of calcium, which signals the vesicles to fuse with cell membrane (exocytosis) to release the neurotransmitters into the synaptic cleft.
neuron
a specialized cell transmitting nerve impulses; a nerve cell.
Na+-K+ pump
3 Na+ out, 2 K+ in = net negative to the inside, net positive to the outside.
concentration cell
a galvanic cell in which both compartments contain the same components, but at different concentrations
Myelin sheath
Covers the axon intermittently, with gaps called nodes of Ranvier. The purpose of myelin sheath is to speed up conduction by insulating the nerve in intervals. This intermittent insulation causes action potential to jump from one node of Ranvier to the next. Myelin sheath is a good insulator because it is fatty and does not contain any channels.
Resting potential (electrochemical gradient)
Na+-K+ pump = 3 Na+ out, 2 K+ in = net negative to the inside, net positive to the outside. K+ leakage = the resting cell membrane has channels that allow K+ to leak out, but don't allow Na+ to leak in = net negative to the inside, net positive to the outside. Resting potential is -70 mV because the cell is more negative on the inside, and more positive on the outside. Electrochemical gradient = combination of electrical and chemical gradient = both electrical potential and ion concentration gradient across membrane.
Axosomatic synpase
axon terminal of one neuron (presynaptic) → cell body of another neuron (postsynaptic).
Hypothalamus
A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.
grey matter
The portions of the central nervous system that are abundant in cell bodies of neurons rather than axons. Unmyelinated.
supraspinal circuits
descend from CNS- can impact sensitivity and speed of reflex
Diencephalon
thalamus and hypothalamus
Axoaxonic synapse (rare)
axon terminal of one neuron (presynaptic) → axon hillock of another (postsynaptic).
pre and post ganglionic neurons
Sympathetic = Short pre-ganglionic neurons with long post-ganglionic Parasympathetic = Long pre-ganglionic neurons with short post-ganglionic
pons
coordinates communication between the motor cortex and the cerebellum, facilitating the transfer of motor commands.
saltatory conduction
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
preganglionic neuron
in the autonomic nervous system of the PNS, a neuron that has its cell body located in the CNS and whose axon extends into the PNS to synapse with a second neuron at an autonomic ganglion (the second neuron's axon synapses with the target organ) All preganglionic neurons in the ANS and post ganglionic neurons in the parasympathetic branch use acetylcholine as their neurotransmitter
Neurotransmitter reception
diffusion of neurotransmitter across the synaptic cleft, binds to receptor, opens up ion channels that causes a change in membrane potential of the postsynaptic neuron (graded potential). If this graded potential is large enough, it will trigger a full-fledged, all-or-nothing action potential in the postsynaptic neuron Neurotransmitters are quickly eliminated (destroyed by enzymes, reuptake by presynaptic terminal, or diffuse away) so that they don't persistently stimulate the postsynaptic neuron.
Release of neurotransmitter
exocytosis of vesicles containing neurotransmitters. Triggered by calcium influx when action potential reaches axon terminal.
reflex arc
A relatively direct connection between a sensory neuron and a motor neuron that allows an extremely rapid response to a stimulus, often without conscious brain involvement.
white matter
Whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths.
Dendrites
Receptive region of the nerve = gets input. The branching helps to increase the surface area for reception.
ciliary muscle
muscle that helps focus light on the retina by controlling the curvature of the lens of the eye
Axodendritic synapse
axon terminal of one neuron (presynaptic) → dendrite of another neuron (postsynaptic).
Nociceptors
pain receptors
Nodes of Ranvier (role in propagation of nerve impulse along axon)
Action potential jumps from one node of Ranvier to the next. This jumping of action potential speeds up conduction in the axon.
Axon (structure, function)
Axon = Conducting region of the nerve. Axon terminals = secretory regions of nerve. Other names for axon terminal = synaptic knob = bouton.
cerebellum
A large structure of the hindbrain that controls fine motor skills.
lateralization of function
the notion that specific psychological or cognitive functions are processed primarily on one side of the brain
sodium-potassium pump
3 sodium out. 2 potassium in. net positive out. causes membrane to be more negative on the inside, hence negative membrane potential.
Section 2
(19 cards)