Phys I LP 7&8
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What makes up neurons/neural tissue?
- Specialized cells
- React to changes in their environment/surroundings
- Schwann cells
- Cell body
Part of the nervous system that receives input and transmits nerve impulse to nerve cell body
- usually there are many of these
- highly branched
Part of the nervous system that conducts nerve impulse away from the cell body
- only one per neuron
- snyapitic nob
Found in the peripheral nervous system, forms myelin sheath around axons, has a neurilemma (outside covering), and the Nodes of Ranvier (gaps), helps speed up the message being sent. (think corn dog)
Found in the central nervous system (CNS) forms myelin sheaths around axons, does not have a neurilemma, no regeneration of the axon
Small space between b/t neurons
- presynaptic neuron (situated before the ynapse is crossed)
- postsynaptic neuron (after the synapse is crossed)
Nerve impulse, how neurons transmit info to other neurons or cells (dendrites-soma-axon)
White colored cells
Grey colored cells
- Nerve impulses from/out of CNS conducted to effectors (muscles or glands) via motor nerves (PNS)
Part of the PNS that controls voluntary activities (skeltal muscle)
Part of the PNS that controls involuntary actions, viscera, breathing, heart, glands
Sensory Neurons (afferent)
Conduct impulase from PNS to CNS
located in the CNS, form links b/t other neurons, like connector points
What is a one-cell thick epithsial lining that lines ventricles and the central canal?
Too much myolin
Inflammed myelin coating due to immune response
What happens if there is injury to the SOMA?
Neuron is killed
What happens if the axon in the PNS is injured?
- The distal portion degenerates
- Proximal portion may regenerate slowly
What happens if there is injury to the axon in the CNS?
Regeneration is unlikely as the oligodendrocytes don't proliferate & there is a lack of neurilemma
Cell membranes (coverings) are usually eletrically charged (polarized). What polarization occures at the inside of the cell?
Cell membranes (coverings) are usually eletrically charged (polarized). What polarization occures at the outside of the cell?
What makes the inside of the cell more negative
There is a high concentration of potassium ions (K+) bananas
What makes the outside of the cell more negative?
There is a high concentration of sodium ions (Na+) salt
How is the balance of sodium and potassium maintained in the cell? (Active transport)
The Na/K pump
What is it called when a nerve cell is not sending a nerve impulse? When the neuron is at rest, ready to fire when needed?
Which ions diffuse across the cell membrane easily?
Which ions have mroe difficulty diffusing across cell membranes?
Na+ ions (sodium)
Which ions have the hardest time diffusing across cell membranes?
Which ions are trapped inside the cell b/c of their size?
Phosphate, sulfate, and proteins (negative charge)
Which ions diffuse into/out of the cell faster?
More positive charge ions leave the cell than enter the due to diffusion
Stimuli cause changes in membrane potential, the more excitable membranes are known as?
When the impulse is being sent.
Depolarized (more +)
Stimuli cause changes in membrane potential, the less excitable are know as?
After the impulse has passed.
Hyperpolarized (more -)
When the stimulus is strong enough (summation or the gathering of several subthreshold stimuli) the neuron reaches this...
- When the cell reaches its threshold potential, the action potential moves down the axon toward the synoptic cleft
- The membrane becomes more permeable to Na+ ions and they rush into the cell making the inside more positivly charged.
- K+ ions leave the cell, making the inside a negative charge again, then it resets really fast (1/1000 of a second fast!)
The time after a nerve impulse is generated in which the nerve (neuron or muscle fiber) cannot/WILL NOT be stimulated.
All or none response
- If a neuron responds at all, it will respond completely
- A greater intensity of stimulus creates more impulses per second not a strong impulse
Why do myleinated fibers have a speedier impulse than unmyleinated fibers? What is this process called?
Saltatory conduction, the impulse jumps from node of ranvier to node at the speed of 100 per second
Increased for of a contraction by skeletal muscle fiber when twitches occure before the previous twitch reflexes
When an action potential passes along the membrane of the synaptic knob, it increases the membrane's permeability to calcium ions. Calium ions diffuse inward and in response, the synaptic vesicles release their contents into the synaptic cleft (the more calcium that entere the more NT released)
How neuro transmitters get released
How does NT cross the snyaptic gap?
What happens when a postsynaptic neuron is stimulated?
An action potential is produced, Na+ ion channels open, depolarizing the membrane
What happens when a postsynaptic neuron is inhibited?
K+ ions diffuse outward, hypermobilizing the membrane and an action potential is unlikely
What are the of neuropeptides?
- They act as nuerotransmitters or neuromodulartors (substances that alter a neuron's response to a neurotransmitter)
- Enkephalins present in the brain and spinal cord. Synthesis of these increases during periods of pain in order to relieve pain
- Beta endorphins offer longer lasting more potent pain relief
- Substance P is widely distributed, functions as a neurotransmitter in the neurons that transmitt pain
- Enkephalins and Beta endorphins may relieve pain by inhibiting the release of Substance P
A neurotransmitter that groups together to perform a common function, receive input - generate output
A neurotransmitter where axons from different part of the NS lead to the same neuron, facilitation = subthreshold stimulation of a neuron
Axon impulses leaving a neuron of a neuronal pool may reach several other neurons
Subthreshold stimulation of a neuron that makes it more responsive to further stimulation
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