Chapter 13- Neuroscience Flashcards
The two major divisions of the nervous system are:
Central nervous system (CNS)
Peripheral nervous system (PNS)
In general, what does the nervous system do?
It enables organisms to receive and respond to stimuli from their external and internal environments.
Neurons
The functional units of the nervous system.
Converts stimuli into electrochemical signals that are conducted through the nervous system.
Which responds to stimuli quicker, the nervous system or the endocrine system?
The nervous system.
What is a neuron?
An elongated cell consisting of several dendrites, a cell body and a single axon.
Soma
Also called the cell body. Contains the nucleus and controls the metabolic activity of the neuron.
Axon
A long cellular process that transmits impulses away from the cell body.
Myelin
Sheath that insulates axons, makes conduction faster.
Oligodendrocytes
Produce myelin in the central nervous system.
Schwann cells
Produce myelin in the peripheral nervous system.
Nodes of ranvier
Gaps between segments of myelin.
Axons end:
Swellings known as axon terminals or synaptic buttons or knobs.
Neurotransmitters
Released from axon terminals into the synapse, which is the gap between the axon terminal of one cell and the dendrites of the next cell.
4 types of cells in the CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
2 types of cells in the PNS
Satellite
Schwann
Astrocytes
Maintain the integrity of the blood brain barrier, regulate nutrient and dissolved gas concentrations, and absorb and recycle neurotransmitters.
Oligodendrocytes
Myelinate CNS axons as well as provide structural framework for the CNS.
Microglia
Remove cellular debris and pathogens.
Ependymal cells
Line the brain ventricles and aid in the production, circulation, and monitoring of cerebral spinal fluid.
Satellite cells
Surround the neuron cell bodies in the ganglia.
Schwann cells
Enclose the axons in the PNS and aid in the myelination of some peripheral axons.
Two neurotransmitters often found in the nervous system:
Norepinephrine and acetylcholine
Precursor of norepinephrine
Dopamine
Where does synthesis of norepinephrine begin? Where does it end?
Begins: axoplasm of the terminal nerve endings of adrenergic fibers
Ends: Inside the vesicles of the fibers
Outline the basic steps in the synthesis of norepinephrine:
Tyrosine is converted to DOPA through the process of hydroxylation
DOPA undergoes decarboxylation to become dopamine
dopamine is transported into vesicles of adrenergic fibers, where it undergoes hydroxylation to become norepinephrine
Where is , norepinephrine is transformed into epinephrine?
In adrenal medulla– through methylation
How is acetylcholine made?
Choline + acetyl-CoA
What are neurons specialized for?
To receive signals from sensory receptors or from other neurons in the body and transfer this information along the length of the axon
Action potentials
Impulses that travel the length of the axon and invade the never terminal, causing the release of neurotransmitter into the synapse.
Resting potential
The potential difference between the extracellular space and the intracellular space when a neuron is at rest.
True or false: at rest, a neuron is polarized
True
Why is there a potential difference at rest?
A result of an unequal distribution of ions between the inside and outside of the cell.
What is a typical resting membrane potential?
-70 millivots (inside is more negative than the outside)
What is the resting membrane potential caused by?
-ly charged compounds are trapped on the side.
Also, inside is selectively permeable to K+, leaving it to travel down its concentration gradient to outside and to leave a net - charge on the inside.
Neurons are impermeable to Na+, leaving cells permeable
Which side of the membrane in more concentrated by each ion?
The concentration of K+ is higher inside than outside. Na+ is higher on the outside than inside.
How is gradient restored after action potential?
The pump uses energy to transport 3 Na+ out and 2 K+ in.
Outside cell:
Na+»_space; K+
net positive charged
Inside cell
K+» Na+
net negative charge
Active transport of K+ is
Two K+ inside
Active transport of Na+ is
3 Na+ outside
Passive transport of K+ is
K+ outside
Passive transport of Na+ is
Na+ inside
Depolarization
Inside of the cell= less negative
Action potential is generated by
If the cell becomes depolarized (excited)
Minimum threshold membrane potential
The level at which an action potential is initiated (-50 mV)
Which phases do depolarization, repolarization and hyperpolarization occur?
Depolarization: Phase 1
Repolarization: Phase 2
Hyperpolarization: Phase 3
When does an action potential begin?
When voltage-gated channels open in response to depolarization, which allows Na+ to rush down its electrochemical gradient into the cell, causing inside to be a lot more positive than outside.
Repolarization
The voltage-gated Na+ channels close, K+ channels open, K+ goes outside of cell down its electrochemical gradient
Hyperpolarization
When neuron shoots past its resting potential and becomes even more negative on the inside than normal
Refractory period
Immediately after an action potential, a period when it is difficult or impossible to initiate another action potential.
All or none response
Action potential with a consistent size and duration is produced when the threshold membrane potential is reached
Nerves fire maximally or not at all
Stimulus intensity is coded by:
the frequency of action potentials
What direction is information transferred?
From dendrite to to synaptic terminal
Impulses are faster when:
Axons have large diameter and are heavily myelinated.
Synapse
Gap between the axon terminal of one neuron (presynaptic neuron) and the dendrites of another neuron (postsynaptic neuron).
Effector cells
cells in muscles or glands that neurons might communicate with.
Neurotransmitters are in
In the membrane bound vesicles of nerve terminals
How is neurotransmitter released?
When an action potential arrives at the nerve terminal and depolarizes it, the synaptic vesicles fuse with the presynaptic membrane and and release neurotransmitters into the synapse.
What happens after neurotransmitters are released into the synapse?
Neurotransmitters diffuse across the synapse and act on receptor proteins on postsynaptic membrane. It will lead to depolarization of postsynaptic cell and cause an action potential.
How is a neurotransmitter removed from the synapse?
Taken back up into the nerve terminal
May also be degraded by enzymes located in the synapse
it way also diffuse out of the synapse
Curare
Blocks postsynaptic acetylcholine receptors so that acetylcholine cannot interact with receptor. Leads to paralysis by blocking nerve impulses to muscles.
Botulism toxin
Prevents the release of acetylcholine from the presynaptic membrane. Leads to paralysis.
