Flashcards in Nervous Tissue Deck (45):
Identify the 3 basic functions of the nervous system in maintaining homeostasis
sensory, integrates (interprets info), motor (responds to info)
Name the 3 main parts of a neuron and describe their functions.
-cell body (location of the organelles)
nuclei (of the CNS)
Ganglia (of the PNS)
-Dendrite- receptive end- may have many
-Axon- conducting end- sending messages away from cell body
Nuclei- nerve cell body location
groups of cell bodies in the central nervous system
Ganglia- nerve cell body location
Groups of cell bodies in the Peripheral nervous system
Contrast white and gray matter
Myelinated neurons are white, unmyelinated are gray.
Distinguish between the structure of a myelinated and an unmyelinated axon, and describe how a myelin sheath is formed.
-Mylen is fat that is wrapped in layers around an axon.
Made by Schwann cells in the PNS
- Made by oligodendrocytes in the CNS.
-Myelinated neurons send nerve impulses MUCH faster than unmyelinated.
Describe how a peripheral nerve is regenerated if cut, and explain why an axon of the CNS cannot regenerate as well.
-Schwann cells can regenerate axons after time by providing structural scaffolding. Slow process
-Oligodendrocytes cannot make bridge between severed axons
Explain the nature of the blood-brain barrier.
- The Astrocytes are founded between brain cell and blood vessels, they act as filters for what gets into the brain. Poisions go to astrocytes not brain. Alc can cross.
-can undergo mytosis
Define neuroglia and give an example of a neuroglial cell
-supporting and protecting tissue
-Schwann cells, oligodendrocytes and astrocytes
Define nerve. Where are nerves located?
-A nerve is groups of axons, found only in the PNS
Classify neurons according to structure.
-Bipolar- one dendrite one axon (nervous layer of retina)
-Multipolar- (most Common) one axon to numerous dendrites (motor)
-Unipolar- t shaped extension that branches into dendrite and axon (sensory)
-Cation is positively charged ion such as Na+ and K+
-responsible for message
- Anions are negatively charged ions such as Cl-
-Responsible for message
Define membrane potentional
-Change difference inside and outside of the cell
(more negative inside the cell)
Explain how the Na+/K+ pump contributes to the resting membrane potential.
-The pump is not equal in charges - it pumps 3 positive sodiums out for every 2 positive potassiums in, contributing to the negativity in the cell.
What is the approximate voltage of a neuron's resting membrane potential?
- -70mV, meaning this much more negative inside of the cell.
Describe the factors that contribute to establishing the resting membrane potential.
-Na/K pump, fixed anions that are a part of the interior of the cell
- K can diffuse relatively easily across the cell membrane and as it diffuses out due to a concentration gradient
-the negative fixed anions draw K back into the cell creating an equilibrium.
-The sodium is found primarily on the outside of the cell and wants to diffuse in, and is attracted in by the fixed anions
-but CANNOT enter the cell because the membrane is not permeable to sodium.
Describe depolarization and repolarization.
-depolarization= becomes more + in the cell due to sodium
-Repolarization= k gates (return to homeostasis) potassium diffusing out of the cell
-this is an action potential
Define local potential
-Spring loaded hinge on gate
-open sodium gate, but then the gates close and the potential is over
-i.e. it does not become a run away cycle.
Which cells have action potentials? Describe the events of an action potential.
Muscle and Nervous cells.
-depolarization( Na gates open)
- voltage regulates gates (sodium gates close)
- A stimulus causes sodium gates to open and sodium comes rushing into the cell. In fact so much sodium comes in that you reach a level called threshold in which it becomes a positive feedback cycle
-so that more and more sodium gates open until it actually becomes positive inside of the cell.
-The sodium gates are only open for a brief period of time
-potassium gates are open for a long time.
-Now that the sodium gates close, the potassium wants to leave the cell for concentration reasons and now that it is positive in the cell
- it also wants to leave since like charges are repelled by each other.
-This is the repolarization portion of the action potential.
Explain how the sodium and potassium concentrations return to the levels of an unstimulated neuron, following an action potential.
-sodium/potassium pump then follows the action potential in which sodium exits the cell and potassium enters the cell.
-3/2 ration and active transport so that ATP is required.
Describe the events of a nerve impulse in myelinated and unmyelinated neurons.
-Series of action potentials
-Myelinated axon-leaping from action potential from node of ranvier to node of ranvier @ 225mph
(called Saltatory conduction)
-unmyelinated neuron- the current flows all the way along the axon. A series of action potentials travel along the neuron @ 2 mph.
Discuss the factors that determine the speed of impulse conduction.
-fat is an insulator against current flow, less surface area to cover thus speeds up
-The more myelin, the faster.
-increased temperature increases impulse conduction.
Define the all-or-none principle of nerve impulse transmission.
-Either an action potential reaches threshold or it doesn't.
Explain why normal nerve impulses tend to be unidirectional.
-Begins at dendrite (sensory) and sends message up, the only way it can go...
Define synapse, presynaptic neuron, postsynaptic neuron
-synapse is the junction between adjacent neurons involving the neuron entering the synapse called
-the presynaptic neuron and the one exiting is the
-postsynaptic neuron is the receiving end.
-The physical space between the 2 is the cleft.
Define synaptic cleft
-The physical space between the presynaptic neuron and the postsynaptic neuron is the cleft.
Define synaptic vesicle
-The vesicle is the bubble filled with neurotransmitter in the presynaptic neuron.
-The neurotransmitter is the chemical released that bridges the synapse.
Describe the action of neurotransmitters. Give an example of a neurotransmitter.
-Neurotransmitters are released at the synapse and diffuse across the synapse.
-There are receptors for the neurotransmitter at the postsynaptic neuron.
-The combination of the neurotransmitter in the receptor leads to depolarization in the postsynaptic neuron because their sodium gates at this location are chemical (neurotransmitter) regulated rather than the voltage regulated gates on the rest of the neuron.
-Acetylcholine, norepinephrine and dopamine ephinephrine, serotonin
Contrast excitatory postsynaptic potentials (EPSP) and inhibitory postsynaptic potentials (IPSP)
-If the neurotransmitter causes depolarization in the postsynaptic neuron it is an EPSP, (excitatory)
Temporal summation -sending multiple
Spatial summation- lots of neurons sending message)
-if it causes hyperpolarization (more negative) in the postsynaptic neuron it is an IPSP. (inhibiting)
-These are graded changes - i.e. not all or none.
Name the enzyme that breaks down acetylcholine.
-a group of neurotransmitters synthesized from tyrosine
-norepinephrine (arousal dreams)
-Epinephrine (emotion behaviors)
-Dopamine (euphoria, emotional responses)
Define neuromodulator and give an example.
-enhance or inhibit
-influence the synthesis
like Enkephalins (runners high) or endorphins (pain killers)
Contrast convergence and divergence as it relates to neural integration.
-come together or seperate (like rivers)
-One presynaptic neuron synapsing with several postsynaptic neurons is divergence;
-many presynaptic neurons synapsing with one postsynaptic neuron is convergence.
Describe temporal and spatial summation.
- Time= sending more neurotransmitters making sure message makes it to threshold (graded reaction)
-Spatial= 3 neurons all converging to send the message to postsynaptic to increase chance of threshold
Define receptor and describe how a stimulus leads to a nerve impulse and how we can distinguish a weak from a strong stimulus.
-The dendrite is the receiving end of the neuron. Its job is to take the stimulus and turn it into depolarization which is what the neuron understands.
-The more dendrites stimulated, the stronger the stimulus. Also, a strong stimulus will send a high frequency of impulses to the brain.
Describe adaptation. Which sensation does not adapt?
-Adaption is with an unchanging stimulus, receptors stop responding
Pain is not adaptable
Define effector and end-plate potential.
-The stopping point for the neuron - such as a muscle or a gland. The depolarization in the effector is the end-plate potential.
Classify the organs of the nervous system into central and peripheral divisions.
CNS= brain spinal cord PNS= Everything traveling towards or away from
-sensory (towards the CNS)
-Motor (away form the CNS)
Surface of body (touching the table)
-impulses going to skeletal muscles are somatic efferent
internal (when your stomach hurts)
-impulses going to smooth muscle, cardiac, glands are visceral efferent= ANS