BIO Ch. 4 Nervous System Flashcards
What is the role of a neuron?
transmit electrical impulses to chemical signals
What is contained in the soma?
the nucleus, ribosomes, and the ER
What is the role of the dendrites?
receives incoming messages from other cells
What is the role of the axon hillock?
integrate incoming signals, and initiate an action potential if the signal is excitatory
What is the diff between a bundle of nerves in the PNS vs. the CNS?
neurons bundle together in the PNS to form a nerve which may be sensory, motor, or mixed, whereas in the CNS, nerves bundle together to form tracts that only carry one type of information
What is the function of astrocytes?
nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue
What is the function of ependymal cells?
they line the ventricles of the brain and produce cerebrospinal fluid which physically supports the brain and serves as a shock absorber
What is the function of Oligodendrocytes?
produce myelin around axons in the CNS
What is the function of microglia?
phagocytic cells that ingest and break down water products and Pathogens in the CNLS
What is the function of Schwann cells?
produce myelin around axons in the PNS
WHAT IS THE RESISTING MEMBRANE potential?
-70 mV
What is the role of K+ leak channels?
a transmembrane channel that slowly leaks potassium facilitating the outward movement of potassium out of the cell
What is the role of Na+ leak channels?
a transmembrane channel that slowly leaks sodium facilitating the outward movement of sodium out of the cell
What is the role of Na+/K+ ATPase?
it pumps 2 potassium ions into the cell and 3 sodium ions out of the cells to maintain their respective gradients, maintaining the resting membrane potential
What does an excitatory input cause?
it causes the cell to depolarize to the threshold voltage and voltage-gated sodium channels open. This raises the membrane potential from its resting potential thus making the neuron more likely to fire an action potential
What does an inhibitory input cause?
it causes hyperpolarization, lowering the membrane potential from its resting potential and thus makes the neurons less likely to fire an action potential
What is the diff b/w temporal and spatial summation?
temporal summation refers to the addition of multiple signals near each other in time, while spatial summation refers to the addition of multiple signals near each other in space
What drives sodium into the cell and potassium out of the cell?
the strong electrochemical gradient
What is the diff b/w the 2 refractory periods (hyperpolarized)?
During the absolute refractory period, no amount of stimulation can cause another action potential to occur. During the relative refractory period, there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value
Describe action potential in a neuron.
a neuron starts at resting potential, around - 70 mV. At the resting potential, potassium is high inside the cell, while sodium is high outside the cell. Once the cell reaches the threshold, sodium channels open, and sodium floods inside the cell, depolarizing the cell. Then sodium channels are inactivated and the potassium channels open, causing potassium to flow out of the cell, ringing the potential to the negative range, repolarizing the cell, and overshooting the resting potential (hyperpolarization). The Na+/k+ ATPase then wors to restore the resting potential
What determines the speed of the action potential?
it depends on the length and the cross-sectional area. An increased length of the axon results in higher resistance and slower conduction. greater cross-sectional areas allow for faster propagation due to decreased resistance
What is the diff b/w chemical and electrical transmission?
within neurons, electricity is used to pass signals down the length of the axon. between neurons, chemicals/neurotransmitters are used to pass signals to subsequent neurons, or glands and muscles
What are the 3 mechanisms by which neurotransmitters are removed from the synaptic cleft?
- acetylcholine is broken down by acetylcholinesterase
- neurotransmitters are brought back into the presynaptic neurons using reuptake carriers such as serotonin, dopamine, and norepinephrine
- they can be diffused out of the synaptic cleft such as nitric oxide signaling molecule
Describe action potential in neurotransmitters
neurotransmitters are stored in membrane-bound vesicles. when an action potential reaches the nerve terminal, voltage-gated calcium channels open, allowing calcium to flow into the cell. This increases the intracellular concentration of calcium, triggering the fusion of the membrane-bound vesicles with the cell membrane at the synapse, causing exocytosis of the neurotransmitters into the synaptic cleft. once released into the synapse, the neurotransmitter molecules diffuse across the cleft and bind to receptors (ligand-gated ion channels of G protein-coupled receptors) on the post-synaptic membrane, allowing the message to be passed from one neuron to the next
What is the diff b/w afferent and efferent neurons?
afferent neurons transmit sensory information from receptors to the spinal cord and brain. efferent neurons transmit moto information from the brain in the spinal cord to the muscles and glands
What is the diff b/w gray and white matter?
white matter consists of axons encased in a myelin sheath. gray matter consists of unmyelinated cell bodies and dendrites
What is the diff in the placement of gray and white matter b/w the brain and the spinal cord?
in the brain, white matter lies deeper than gray matter, while in the spinal cord, white matter lies on the outside of the cord, and gray matter is deep within it.
Where are the sensory neurons found in the spinal cord?
the sensory neurons bring information from the periphery and enter through cell bodies in the dorsal root ganglia
Where are the motor neurons found in the spinal cord?
motor neurons exit the spinal cord ventrally into the ventral root ganglia
What are the nerves of the PNS?
31 spinal nerves, and 10 cranial nerves excluding the optic and olfactory nerves
What is the role of the ANS?
Automatic functions such as regulating heartbeat, respiration, digestion, temperature, and glandular secretion
What is the role of the PNS?
It is associated with resting and sleeping states, and acts to reduce heart rate and constrict the bronchi, increases parastalsis and exocrine secretion
What is the neurotransmitter responsible for the PNS response?
acetylcholine is released in the pre and postganglionic neurons
Which nerve is responsible for the parasympathetic innervation of the thoracic and abdominal cavities?
vagus nerve/cranial nere X
What is the neurotransmitter responsible for the SNS response?
In the preganglionic neurons, acetylcholine is released, while the postganglionic neurons release norepinephrine
What are the 2 types of reflex arcs?
mono and polysynaptic
What is an example of a monosynaptic reflex arc?
the knee-jerk reflex
What is an example of a polysynaptic reflex arc?
withdrawal reflex
What is the diff b/w electrical and chemical communication?
Electric communication occurs via ION exchange and the generation of membrane potential down the length of the axon. Chemical communication occurs via NEUROTRANSMITTERS released from the presynaptic cells and the binding of these neurotransmitters to the postsynaptic cell
Where are neurotransmitters released?
in the nerve terminal/synaptic bouton
What are the differences b/w the cell bodies of neurons in the PNS and CNS?
Cell bodies of neurons of the same type within a nerve cluster in the ganglia in the PNS. cell bodies of neurons within a tract cluster in nuclei in the CNS
What is the diff b/w mono and polysynaptic reflect arcs?
mono - a sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron. in polysynaptic reflex, a sensory neuron may fire directly onto motorneurons, or through interneurons which then directly into the motor neuron
What is saltatory conduction?
when action potential jumps from node to node
What causes hyperpolarization?
it is caused by the excess potassium exiting the neuron
How does anticonvulsant drugs work to treat seizures??
By increasing the threshold for action potential generation, making it more difficult for neurons to reach the level of depolarization required to initiate an action potential. By raising the threshold, these drugs can prevent excessive abnormal neuronal firing that leads to seizures
