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Nervous System Flashcards

9.1 INTRO TO NERVOUS SYSTEM 9.2 ELECTRICAL IMPULSE 9.4 AUTONOMIC NERVOUS SYSTEM (62 cards)

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1
Q

NERVOUS SYSTEM

A

An elaborate communication system that contains more than 100 million nerve cells in the brain alone

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2
Q

Responses to changes in internal and external environments are made possible by

A

electrochemical messages relaid to and from the brain

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3
Q

There are 2 types of cells in the nervous system:

A

Glial Cells - non conducting cells important for structural support and metabolism of the nerve cells
Neurons - nerve cells that conduct nerve impulses; the functional units of the nervous system

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4
Q

Glial Cells -

A

non conducting cells important for structural support and metabolism of the nerve cells

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5
Q

Neurons -

A

nerve cells that conduct nerve impulses; the functional units of the nervous system

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6
Q

Sensory neurons

A

Aka afferent neurons
Sense and relay info from the environment to the CNS
Located in clusters called ganglia located outside the spinal cord

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7
Q

Interneurons

A

Link neurons within the body
Found mainly throughout brain & spinal cord
Integrate the sensory information and connect neurons to outgoing motor neurons

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8
Q

Motor neurons

A

Aka efferent neurons

Relay info to the effectors like muscles, organs, and glands

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9
Q

Dendrite

A

Receive information from other nerve cells

Conduct nerve impulses toward the cell body

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10
Q

Node of Ranvier

A

The areas b/w the sections of myelin sheath

Allows nerve impulse to jump from node to node, speeding up transmission

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11
Q

Axon

A

Projects nerve impulses away from the cell body

It carries the nerve impulse toward other neurons

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12
Q

Myelin Sheath

A

Formed by special cells called Schwann cells
It insulates by preventing the loss of charged ions from the nerve cell
Speeds the rate of nerve impulse transmission

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13
Q

Speed of nerve impulse is affected by

A

Diameter of the axon (small = faster)

Whether the axon is myelinated or not (if there is then its faster)

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14
Q

The Reflex Arc

A

Reflexes like reaching to touch a hot stove do not require information to travel to your brain and get processed

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15
Q

Reflex Arc -

5 essential components

A

simple connection of neurons that result in a reflex action in response to a stimulus
Involuntary and often unconscious

The receptor 
The sensory neuron 
The interneuron 
The motor neuron 
Effector
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16
Q

ELECTRICAL CURRENT

Current is the movement of electrons along a wire

A

NERVE IMPULSE

Is an electrochemical message created by the movement of ions through the nerve cell membrane

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17
Q

ELECTRICAL CURRENT

Electrical current diminishes as it moves through the wire

A

NERVE IMPULSE

Nerve impulses remain as strong at the end of a nerve as they were at the beginning

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18
Q

ELECTRICAL CURRENT

Electricity relies on external energy source to push electrons

A

NERVE IMPULSE

Nerves use cellular energy to generate current

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19
Q

ELECTRICAL CURRENT

Electricity moves faster

A

NERVE IMPULSE

Nerve impulse is slower than electrical current

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20
Q

The Giant Axon of the Squid

A

When a tiny electrode was placed inside the large nerve cell of the squid, the inside of the neuron is negative relative to the outside (at rest) … why?
Negatively charged protein molecules inside the cell are too large to leave the cell
Sodium-potassium pump located in the cell membrane actively pump out 3 Na+ out for every 2 K+ in
Nerve cell membrane is super permeable to K+ so K+ tends to leak out

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21
Q

Resting Potential

A

→ -70mV

→ polarized

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22
Q

Graded Potential

A

→ +ve

→ below threshold

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23
Q

Action Potential

A

→ +50mV
→ @threshold and over
→ depolarized

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24
Q

Resting Potential

A

When the difference in voltage b/w the inside and the outside of the neuron (at rest) is measured, it is charged and is called polarized membrane .

RESTING POTENTIAL = -70 mV
This separation of electrical charges by a membrane has the potential to work

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25
Upon Excitation
Some stimulus cause the resting potential to move towards 0mV Na+ channels open up, allowing Na+ to rush in If enough Na+ rushes in causing the membrane potential to go from -70mV to -55mV The voltage-gated Na+ gates open causing a rapid influx of Na+ Voltage-gated Na+ channels always closed until Na+ reaches threshold This causes a charge reversal (aka depolarization)
26
Action Potential
The reversal of potential A rapid change in the electrical potential difference across the membrane was detected every time the nerve became excited Resting potential went from -70mV to +40mV when it was excited
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Repolarization
Once the voltage inside the nerve cell becomes positive The voltage-gated Na+ gates close (Na+ no longer enters) K+ channels open (K+ leaves)
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Repolarization Results in
an overall loss of positive charge from the neuron, making the charge move back towards the resting potential
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K+ channels repolarization
stay open longer than needed, and allow more K+ to exit | Makes the cell more negative than resting potential (hyperpolarization)
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repolarization pump
The Na+/K+ pump works to restore the potential back to -70mV known as
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Refractory Period -
recovery time required before a neuron can produce another action potential
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Movement of Action Potential
Similar to the wave | The action potential moves along the nerve cell membrane, creating a wave of depolarization and repolarization
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Threshold Levels - All-or-None Response
A potential stimulus must be above the critical value to produce a response
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Threshold level
min level of a stimulus required to produce a response
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All-or-none response
a nerve or muscle fibre responds completely or not at all to a stimulus ↑ in intensity of the stimulus above threshold ≠ increased response Neurons either fire maximally or not at all
36
When the depolarization reaches about -55mV
a neuron will fire an action potential. (this is the threshold)
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If the neuron does not reach this critical threshold level
then no action potential will fire
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If the threshold level is reached,
an action potential of a fixed size will always fire (for any given neuron), the size of the action potential is always the same ∴ the neuron either does not reach the threshold or a full action potential is fired “ALL OR NONE” principle
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The more intense the stimulus
the greater the frequency of impulses
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Every neuron may have a different threshold level
Ex. a glass rod at 40 oC may cause a single neuron to reach threshold level, but the same glass rod at 50 oC will cause 2 or more neurons to fire (more neurons firing = more neurons telling the brain info = ↑ frequency = ↑ stimulus
41
Synapses
the junction b/w 2 neurons or b/w a neurons and an effector (muscle or gland) (the action potential that travels through synaptic cleft)
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Neurotransmitters
chemicals released from vesicles into synapses Once the nerve impulse reaches the end of the axon, small vesicles containing neurotransmitter fuse with the presynaptic membrane and release the neurotransmitter into the synaptic cleft These neurotransmitters diffuse across the synaptic cleft and bind to receptors in the post-synaptic membrane
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depolarization
This triggers opening of the sodium channels causing influx of sodium into the post-synaptic neuron causing depolarization With the sodium channels open, the postsynaptic neuron would remain in a constant state of depolarization
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How can the nerve respond to the next impulse if it never recovers?
Reuptake of neurotransmitter from the presynaptic neuron and neighboring glial cells Degradation by enzymes (ex. Cholinesterase)
45
The greater the number of synapses
the slower the speed of transmission
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Neurotransmitters can be
EXCITATORY: causing depolarization of post-synaptic neuron INHIBITORY: causing hyperpolarization of post-synaptic neuron
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EXCITATORY:
causing depolarization of post-synaptic neuron
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INHIBITORY:
causing hyperpolarization of post-synaptic neuron
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Summation
Effect produced by the accumulation of neurotransmitters from 2 or more neurons A and B does not create action potential, no charge reversal But when fired at the same time, it can cause depolarization of the post-synaptic membrane D becomes more negatively charged when C is activated Neuron C is inhibitory and causes hyperpolarization (influx of potassium channels, release more negative ions)
50
Inhibitory & Excitatory Neurotransmitters | Throwing a ball
``` Contracting triceps (excitatory) Relaxing biceps (inhibitory) ```
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Inhibitory & Excitatory Neurotransmitters | Prioritization (ex. Biology class)
Listening to teacher voice (excitatory) Looking at diagram on blackboard (excitatory) Hearing background noise (inhibitory) Sensing a draft in the classroom (inhibitory)
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Inhibitory & Excitatory Neurotransmitters
Pain senses shut off in intense situation to help survival (inhibitory)
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Acetylcholine
a neurotransmitter found in the end plates of many nerve cells
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Acetylcholine Can act as
``` an excitatory (inhibitory in some other synapses) neurotransmitter on many postsynaptic neurons by opening the sodium ion channels Sodium rushes in and reverses the charge in the post-synaptic neuron (depolarization) Then degraded by an enzyme (cholinesterase) after the nerve impulse has been transmitted ```
55
What happens if you block cholinesterase?
When cholinesterase is inhibited, acetylcholine is released and not destroyed Nerve cannot respond to the next impulse
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Neurotransmitters and Depression
There is a link b/w neurotransmitters and depression Dopamine Norepinephrine Serotonin This has given a rise to a class of drugs that targets synaptic transmission
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Ex. SSRI’s (selective serotonin reuptake inhibitors)
They work to block the reuptake of neurotransmitters after the nerve impulse has been transmitted This serves to prolong the effect of the neurotransmitter SSRI works if the person has serotonin imbalance It allows the synapses to reach threshold → fires one does not work for everybody because some people don’t have serotonin imbalance or receptors for serotonin if you didn’t have a problem before, you will after you take this drug because your body maintains homeostasis. If they repress reuptake of serotonin, homeostasis is maintained if there is less release of serotonin. If you get off this drug, your body is not releasing enough serotonin.
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AUTONOMIC NERVOUS SYSTEM
It is part of the PNS It works with the endocrine system in adjusting the body to changes in the external and internal environment All autonomic nerves are motor nerves that regulate the organs of the body without conscious control
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Autonomic Nerves
made up of the sympathetic nervous system and the parasympathetic nervous system
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Autonomic Nerves Sympathetic:
Prepares the body for stress The neurotransmitters released: Acetylcholine Norepinephrine
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Autonomic Nerves Parasympathetic
Restores the body’s normal balance | Only releases acetylcholine
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Sympathetic & Parasympathetic
These 2 (often opposing) systems have to balance each other constantly for a person to stay healthy

Biology 12U (8 decks)

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