the nervous system Flashcards
What is the purpose of the nervous system?
To maintain homeostasis/equilbrium
Is a nervous system slow or fast? Explain
It is very fast, and can move up to 500 km/hour. This is necessary in order for reactions to happen quickly when necessary. ie: touching heat
Why is homeostasis in the body important?
This is necessary in order for things that take place within the body have the right environment to do so, as well as to maintain the relative constancy of the internal environment in the living organism.
What are the two main divisions of the nervous system?
The central nervous system (CNS), and the peripheral nervous system (PNS)
What makes up the CNS and what does it do?
The CNS is made up of the brain and the spinal cord
It is the coordinating center and regulator of incoming AND outgoing info. It moves back and forth
What makes up the PNS and what does it do?
The PNS consists of nerves between the body (organs, tissue, etc) and the CNS
It brings info to and away from CNS
ex: If something is hot, the message is sent through PNS to CNS, which will direct something to be done
What are the two classes of nerves in the peripheral nervous system?
- Somatic nerves
2. Autonomic nerves
What is a somatic nerve?
This is a voluntary nerve, meaning that you control it
It is controlled by the frontal lobe and cerebellum in the brain
This mointers external environment to body ie: sight, feel, pain, etc…
What are the two typed of neurons within the somatic nerve?
The somatic nervous system consists of Sensory neurons and motor neurons
What does the sensory neuron do?
Sensory somatic nerves brings info from external environment to CNS, connected to regulators (which let the neuron know what is happening outside of body ie: touching something )- picks up sensory stimuli
What does the motor neuron do?
Motor somatic nerves bring info from CNS to effectors (sends directions from brain to muscles and glands)
BASICALLY
The peripheral neuron system consists of somatic nerves and autonomic nerves. The neurons in the somatic nervous system allows it to do its job, which is to moniter external environment. The two types of neurons are the sensory neurons, which detect external environments with regulators, and the sensory neuron sends that message to the CNS. From the CNS, it recognizes a prblem (something is too hot) and the second neuron, the motot neuron, carries that information from the CNS to the effectors, which allows somwthing to b done (ie: hand moved away from heat)
What is the autonomic nerve?
Autonomic nerves are involuntary. They are controlled by the medula oblongata and the hypothalamus in the brain.
This moniters the internal environment of the body ex: heart beat, breathing, pupils, etc…
What are the two divisions in the autonomic nervous system?
The two divisions of the system are the sympathetic and the parasympathetics.
What does the sympathetic division regulate?
Sympathetic autonomic division regulates the fight or flight responses. Also preforms tasks such as relaxing the bladder, upping heart rate, and dilating pupils
What does the parasympathetic division regulate?
Parasympathetic autonomic division Regulates the rest and digest response.
What does the somatic nervous system control in terms of parts of body?
skeletal muscle, bones, and skin
What is a neuron?
A nerve cell that responds to stimuli and transmits signals (they are a small part of your nervous tissue)
What surrounds and protects the neuron?
Glial cells
What is another name for a glial cell?
Neurological cell
What is a glial cell? Give an example
a nonconducting cell important for structural support and nourishing neurons. No signals are sent through this. ex: shwann cell
What is the body’s autonomic response to stress?
Sympathetic
What is the bodys autonomic respponse for relaxing and returning to normal?
Parasympathetic
In reference to pupils, what are the sympathetic and parasympathetic reactions and why?
Parasympathetic- pupis constrict and go back to normal
Sympathetic- pupils dilate, allowing more light in and to see more
What are the two types of cells in the nervous system?
Glial cells, and neurons
What is a neuron?
There are 3 types of neurons, which is a conducting cell that transmits signals throuhgout the body.
What are the parts of the neuron and what do they do?
Nucleus
Dendrite - projection of cytopasm, receives info/ impulses from receptors or other neurons
Axon- (everything after teh cell body), projection of cytoplasm, carries signals to effector or another neuron
Cell body- contains organelles+nucleus
Node of ranvier- (gap in between shwann cells)- increase rate of transmission by jumping in between nodes
Myelin sheath- (cap of glial cell), insulates neuron, increases rate of signal transmission
Axon terminal- end of the axon, start of the synaps
shwann cell- type of glial cell, secretes myelin sheath, covers axon
What are the 3 types of neurons and what do they do?
- Sensory neurons- connected to receptors to gather info about environment
- Interneurons- found in CNS, integrate/interpret info from sensory neurons+transmits to motor neruons THESE ARE NON MYELINATED (no myelin sheath)
- motor neurons- connected to effectors to ¨o something´
Basically the two somatic nerves and the middle space in the peripheral nervous system
What does it mean when a brain scan shows white?
this means there are nevres within the brain that has a myelin sheath, but no neurilemma.
What does it mean when a brain shows grey?
This means there are nerves within the brain and spinal cord where there is no myelin sheath or neurilemma.
What is a neurilemma?
Myelinated neurons found in the PNS have thin outer membranes called neurilemma. They are formed by schwann cells, and promote axon regenration.
Explain why neurons in the brain are more likely to be permanently damaged?
Because a majority of the nervous cells in the brain have no neurilemma, meaning that axons are not able to regenerate well.
Why is the interneuron more likely to be permanently damaged?
Because the interneurons in the brain do not have myelin sheaths, and are unprotected.
Which neurons do have myelin sheaths?
Sensory and motor neurons
Where does the myelin sheath come from?
It is secreted by the schwann cell
Where does the nerve impulse go for a reflex arc?
Goes to spinal cord only
Where does the nerve impulse go for a general nerve signal?
To both the brain and the spinal cord
What is necessary for a signal to be sent through the neuron?
An action potential is required, which is the charge across a memebrane
What are the 3 stages of an action potential?
- Polarization/ resting membrane (before action potential is triggered)
- Depolarization (Once action potential is triggered)
- Repolarization (Returning to resting membrane)
What happens during the polarization stage?
This is before action potential is triggered
Na+ channels are closed, K+ channels are open, and influx of sodium ions are accumulated outside of membrane
This creates outside to be POSITIVELY charged
while the inside of the membrane is NEGATIVELY CHARGED
What occurs during the depolarization stage?
This is when the potential action is triggered, (bried caused by change of currents)
Threshold is reached
Once the threshold is reached, Na+ channels open and they pour into the inner membrane
K+ channels close
Outside becomes NEGATIVELY charged, inside becomes POSITIVELY charged.
What occurs during the repolarization stage?
Membrane potential (microvolts) go back below threshold. The Na+ channels close, K+ channels open (+ K leaves because it has been accumulating) Outside becomes POSITIVE, inside becomes NEGATIVE once more
What is hyperpolarization?
When too much K+ leaves the inner membrane, causing it to be too negative, also making it more difficult to reach threshold once more
Na/K pump restores to resting membrane state
Is it possible to have some reaction when microvolts come in?
Sometimes there is a slight change when membrane potential rises, in which some channels open, but not enough to reach the threshold and invoke change (remember all or nothing rule)
Is it the stimulus, impulse, or action potential which causes the gated channels to open?
Action potential
Once the gated channels are open and positive ions begin to enter the neuron, we have the start of a(n) __________.
Impulse
Do the sodium gates open all at once or in succession once there is enough stimuli (potential passes threshold)
In succession. Remember the domino effect.
What is the refractory period?
recovery time before another action potential
can be produced; makes sure that impulses travel in one direction only
What is responsible for the intensity of a signal?
- the number of neurons invoved
- The number of impulses sent (Many impulses=greater reaction ex: more impulses sent when touching somethin salding hot than warm)
What is responsible for the rate of an impulse?
- Myelinated neurons will move faster than non-myelinated
2. Diameter of the axon (Bigger sends faster)
What is a synaptic transmission?
This is how the signal is sent between the axon terminal of the pre-synaptic neuron tp the dendrite of the post synaptic neruon
What are the two kinds of transmissions?
Chemical and electrical
Is synaptic transmission faster or slower and why?
It is slower because it is a chemical transmission, wheras action potential is electrical
What are the steps to a synaptic transmission?
- Action potential reaches axon terminal- this triggers an increase of Ca+ into the axon terminal, and vesicles with neurotransmitters move to the membrane
- Vesicles fuse to membrane- they release the neurotransmitters into the synapse
- NT diffuses across synapse- binds to receptors on the next dendrite (post-synaptic neuron) this stimulates the psn
- Enzymes are released from the presynaptic neuron, which break down the neurotransmitters and stop the signal. The neurotransmitters are then recycled.
What are the two potential outcomes when an NT binds to receptors?
If it is an excitatory neurotransmitter, this will cause Na+ (sodium) channels to open up on the dendrite. This then causes the Na+ to move into the dendrite, which triggers action potential, which will create a depolarized environment
If it is an inhibitory neurotransmitter, the K+ channels will open, and the K+ will move out. this will create a hyperpolarized membrane, meaning the threshold for action potential is not reached. This stops pain signals.
