Lecture Exam 2 Flashcards
Central nervous system
- Brain
2. Spinal cord
Reflex
Automatic, reproducible response to a stimulus
What reflex did we focus on?
Neural reflex
How do you detect a stimulus?
By using a receptor that takes information about a stimulus and sends it to the integration center, which determines if the stimulus requires a response, if a response is needed it sends the information to an effector which responds to the stimulus
What is different about a neural reflex from a reflex?
The receptor, integration center, and effector are all connected by neurons
Pain/withdraw reflex
Moves affected parts of the body away from the stimulus
Events in a reflex arc
- Arrival of stimulus and activation of receptor
- Activation of sensory neuron
- Information processing in the CNS
- Activation of a motor neuron
- Response by effector
Sensory neuron
In epithelium; allows us to detect stimuli in the environment; this is the receptor for the pain reflex
What do receptors on the dendrites do
They are always detecting stimuli, but they don’t always do something about it
Resting membrane potential
The resting phase of a neuron; when you don’t notice any stimuli from the environment
Threshold
When a stimulus is strong enough to take it out of resting membrane potential; the point where a stimulus is so strong that it activates a sensory neuron
Action potential
How neurons communicate; when the stimulus is so strong that the neuron gets to threshold, it will create this
Synapse
Where a neuron reaches another cell
Graded potential
Describes a neuron that is analyzing information and deciding what to do about it
Motor neuron
Activates effectors; activated by CNS
What is an example of a motor neuron
When moving your hand away from a hot stove, the effector is your muscle
Ways to classify reflexes
- By development
- By effector
- By complexity
- By integration center
Reflexes classified by development
- Innate reflex
2. Learned (acquired) reflex
Innate reflex
Reflexes that you are born with; that you don’t have to learn
Learned (acquired) reflex
Learned, more complex, motor patterns that are continuously refined
Can you suppress a reflex?
Yes, you can repress some, but not all, reflexes
Reflexes classified by effector
- Somatic reflex
2. Visceral reflex
Somatic reflex
Effector is a response from skeletal muscle
Visceral reflex
Effector is a response from an organ
Reflexes classified by complexity
- Monosynaptic reflex
2. Polysynaptic reflex
Monosynaptic reflex
One synapse is being used at a time
Example of monosynaptic reflex
Pain reflex
Polysynaptic reflex
Multiple synapses being used
Pros to monosynaptic refle
They are really fast
Cons to monosynaptic reflex
They are unrefined; if you pull away from something painful you could hit your hand on something else
Pros to polysynaptic reflex
More refined and complex; if you step on a toy you press down on one foot to keep balance and pull up the other foot
Cons to polysynaptic reflex
It is slower than monosynaptic reflex
Types of integration centers
- Cranial
2. Spinal
What determines which type of integration center you use
The location
What does it mean that reflexes are not mutually exclusive?
A reflex can be many different classes (monosynaptic and innate)
Reflexes happen…
Before we perceive the stimulus; this allows us to minimize the damage
Nervous system branches
- Central nervous system
2. Peripheral nervous system
Main function of the CNS
It is the integration center
Peripheral nervous system
All the neural tissue that is not in the brain or spinal cord
Types of PNS
- Afferent nervous system
2. Efferent nervous system
Afferent nervous system
System of neurons that brings sensory information from the body into the CNS
Efferent nervous system
Carries motor command information from the CNS to the body
Types of Efferent nervous system
- Somatic nervous system
2. Autonomic nervous system
Somatic nervous system
Carries efferent/motor commands to skeletal muscle
Autonomic nervous system
Controls everything that we move unconsciously
Types of autonomic nervous system
- Sympathetic nervous system
2. Parasympathetic nervous system
Sympathetic nervous system
“Fight or flight”; increases heart and respiratory rate and shuts down the urinary system and digestive system to save energy
Parasympathetic nervous system
“Rest and digest”; stimulates the digestive and urinary systems, decreases heart and respiratory rate
Can you have both the sympathetic and parasympathetic system working at the same time?
Yes, there is always a combination of both
Cell body
Soma
Parts of cell body
- Nucleus
2. Perikaryon
Perikaryon
The space around the nucleus; peri=around karyon=nucleus
What is found in the perikaryon
All of the organelles that would be found in a normal cell
What does the perikaryon lack that other normal cells have, and what does this cause?
Centrioles, which makes neurons unable to divide
Nissl bodies
The equivalent of the rough ER in neurons; has ribosomes, which link amino acids and makes proteins, that cover the outside and makes it “rough”; causes the grey color
Axon hillock
This creates an action potential if a stimulus is strong enough for a response
What direction does the action potential move?
Away from the soma
Axolemma
The plasma membrane of the axon
Action potential
An electrical current
Synaptic terminal
The end of the telodendria; where the neuron communicates with another cell
Telodendria
The branches of the axon
Synaptic cleft/Synapse
The small gap between the synaptic terminal and the next tell
How does the neuron communicate with the next cell?
Inside of the synaptic vesicles there are neurotransmitters; the neuron uses exocytosis to dump the neurotransmitters into the synapse/synaptic cleft
What do the neurotransmitters do?
They tell the next cell what to do
Types of neurons
- Anaxonic neuron
- Bipolar neuron
- Unipolar neuron
- Multipolar neuron
Anaxonic neuron
Dendrites and axons look the same; the only neuron that is only in the CNS; they help serve as integration centers
Bipolar neuron
Afferent; cell body has two distinct extensions (one goes to dendrites, one goes to axon); carries special sensory information like sound, sight, and taste
Unipolar neuron
Afferent; cell body with one extension that splits; carries sensory information for everything besides special sensory information like somatic and visceral information
Multipolar neuron
Efferent; multiple extensions; carries motor commands from the CNS to the body
Membrane potential
An electrical charge; the charge on the inside of the membrane RELATIVE to the charge on the outside
What is the mV for resting potential?
-70 mV
What things contribute to the negative charge
- Leak channels
- Sodium-potassium pump
- Intracellular proteins
Leak channel
Allows for the facilitated diffusion of sodium and potassium ions
Where are there more sodium ion?
Outside the membrane
Where are there more potassium ions?
Inside the membrane
Sodium and potassium have ____ charges
Positive
Potassium leaks ____, sodium leaks ____
Out; in
Does sodium or potassium leak faster?
Potassium leaks out faster than sodium leaks in
Potassium leaking out faster than sodium leaking in causes what
This lowers the charge inside the cell making it more negative
Sodium-potassium pump
Active transport; moves sodium out and potassium in; uses energy because it moves things against the gradient
Does sodium or potassium move in/out more?
More sodium is moving out than potassium is moving in
Intracellular proteins
Located right on the inside of the membrane; negative charge; makes the inside more negative than the outside
What causes a membrane potential to leave resting membrane potential?
A stimulus
What does a stimulus do to the resting membrane potential?
Either:
- Makes it more positive
- Makes it more negative
Graded potential
A stimulus that acts on a neuron at rest; a deviation from the resting membrane potential (more + or more -)
Types of graded potentials
- Depolarizing graded potential
2. Hyperpolarizing graded potential
Depolarizing graded potential
A deviation that makes membrane potential more positive/more like the outside
Depolarizing graded potential is also called
Excitatory post-synaptic potential (EPSP)
Hyperpolarizing graded potential
A deviation that makes membrane potential more negative/less like the outside
Hyperpolarizing graded potential is also called
Inhibitory post-synaptic potential (IPSP)
O mV would mean
It is the same on the inside and outside
Threshold (membrane potential)
A membrane potential that is between -55 to -50 mV; A certain charge that causes a neuron to fire an action potential
EPSP gets you
Closer to threshold
IPSP moves it
Further from threshold to silence a neuron
Gated channels
At rest, are typically closed
Types of gated channels
- Chemically gated channel
2. Mechanically gated channel
Chemically gated channel
A chemical stimulus caused it to open
Mechanically gated channel
Mechanical pressure (being touched) caused it to open
What do gated channels allow?
These allow ions to move through the membrane
Gated channels can either be
- Potassium channels
2. Sodium channel
If a chemical produced a EPSP it would be
A sodium channel because sodium moves from the outside in, down its gradient
What happens in gated channels
They carry out graded potentials; chemical binds to the gated channels, moves in, then is diffused across the membrane
How can you tell what kind of gated channel it is?
Look at which way the ions are moving, if they are moving in, it is sodium; if they are moving out, it is potassium
What do the sodium-potassium pumps do?
It moves sodium back out to get back to resting membrane potential
What is the graded potential “battle”?
EPSP is trying to bring sodium in and reach threshold while the sodium-potassium pumps are trying to pump sodium out and get away from threshold and back to resting membrane potential
How do you reach threshold?
There has to be more sodium coming in than the sodium-potassium pump can push back out
1 EPSP only changes the membrane potential by
About .5 mV
Summation
Adding more than 1 graded potential together; used to get to threshold
Types of summation
- Temporal summation
2. Spatial summation
Temporal summation
When we summate graded potentials from a single synapse
Explain temporal summation
One telodendrian synapses with another neuron. An action potential is sent through the telodendrian and neurotransmitters are sent through the synapse; happens one after another faster than the sodium-potassium pump can push out
Can you summate EPSP and IPSP at the same time in temporal summation?
No, you can only summate EPSP OR IPSP, not both at the same time; Because one synapse can only send one type of graded potential (EPSP or IPSP) and they would just cancel each other out
Spatial summation
When we summate graded potentials from multiple synapses; the sodium mixes; the synapses must be close together
What does summation do for graded potentials
Graded potentials are weak by themselves, so we have to summate them to reach threshold
How do we differentiate between different action potentials?
By the way that our neurons are wired; the action potentials get sent to different places in our brain
What determines different sensations/the strength of the signal?
The number of action potentials that are being generated
Volted-gated channel
A membrane potential (mV) causes it to open or close; has two gates: activation gate on outside of cell, inactivation gate on inside of cell
What happens to a volted-gated channel once you reach threshold?
The gates open and allows sodium to rush through until the membrane potential reaches 30 mV
When does the inactivation gate close?
When the membrane potential reaches 30 and stays closed until the neuron goes back to resting membrane potential
What happens once the membrane reaches -70mV (volted-gated channel)?
The inactivation gate opens and the activation gate closes
Describe the graph and what happens when the membrane potential reaches threshold
When the membrane potential reaches threshold, action potential begins and the membrane potential goes more and more positive, then it goes back to resting membrane potential
What can we tell from this graph?
- In this graph there is an EPSP that depolarizes
2. It must be summated because one EPSP will move it only about .5 mV
What happens when the cell reaches threshold?
Volted gated sodium channels open
Once the membrane reaches 30+ what happens?
- The inactivation gate of the volted gated sodium channel closes
- Volted gated potassium channels open and potassium rushed out
What happens at about -70mV?
Volted gated potassium channels are closed
What is happening at 4 on the graph? (mV moves below -70mV briefly after the action potential comes back down and then moves back to resting membrane potential)
The potassium channels take a long time to close, so they start closing down early causing it to lose a little too much potassium and it hyperpolarizes, or becomes more negative
What protein repolarizes and gets the cell back to rest?
Sodium-potassium pump
Why do we need an IPSP?
To move things away from threshold so that another neuron can have more accurate information (mosquito example)
How does an action potential move down the axon?
One section depolarizes, reaches threshold, fires an action potential, and volted gated sodium channels open causing sodium to rush in, diffuse, and cause the next section to reach threshold
Propagation
How an action potential moves from the cell body to the synapse
Types of propagation
- Continuous propagation
2. Saltatory propagation
Continuous propagation
When every single part of the axon reaches threshold; not very fast
Saltatory propagation
Skips through the axon and doesn’t touch every part of the axon; fastest way
What makes saltatory propagation possible?
Myelin
What cell types produce myelin?
- Shwann cell
2. Oligodendrocyte
What does myelin do for an axon?
It prevents any ions from moving across the membrane so there is no movement of sodium or potassium; it wraps around the axon in layers
Node of Ranvier
The exposed axon that is not covered by myelin
Internodes
Myelinated regions between the nodes that is covered in myelin
How do action potentials move?
They are unidirectional, they only move towards the synapse and away from the cell body
Absolute refractory period
The period of time from when the volted gated sodium channels open until they close and are inactivated
Why is it impossible to fire an action potential during the absolute refractory period?
Because the volted gated sodium channels are either being used or inactivated
Relative refractory period
The period of time when the membrane is hyperpolarized and below resting membrane potential
Why can you fire an action potential during the relative refractory period?
Because the volted gated sodium channels are reset and can be used again, but the stimulus has to be stronger than normal because the membrane potential is further than usual from threshold
What happens when the sodium diffuses, going both up and down the membrane, and it goes backwards?
The membrane is in absolute refractory period and can’t fire another action potential
What is the importance of refractory periods?
They keep action potentials moving in one direction
What determines the speed of an action potential?
- If it is myelinated or not
2. The diameter of the axon/neuron
How does the diameter of the axon/neuron affect the speed of an action potential?
Local currents can move quicker and sodium diffuses faster
Fastest type of neuron
Myelinated with a large diameter
Slowest type of neuron
Unmyelinated with a small diameter
Presynaptic neuron
The neuron that is giving the neurotransmitters
Postsynaptic neuron
The neuron that is receiving the neurotransmitters
Cholinergic
Secretes Acetylcholine
Neuromuscular junction
A neuron forms a synapse onto a muscle cell
What happens when the action potential reaches the synapse?
It opens a volted gated calcium channel, which is found at the end of the synapse that opens in response to the action potential
Calcium has the same concentration gradient as what and what does that mean
Sodium; this means that calcium floods into the cell, down its gradient
What is the result of calcium flooding into the cell?
It causes the exocytosis of the neurotransmitter into the synapse
What happens after the neurotransmitters are pushed into the synapse?
Acetylcholine or other neurotransmitters binds to a receptor on the postsynaptic neuron and sodium moves in
What kind of receptor are they?
Chemically gated sodium channels
What does the sodium do to the next cell?
It makes it start an EPSP, but that doesn’t mean that it will reach threshold
Reuptake
Since neurotransmitters need to be removed from the synapse, this is the process where the presynaptic neuron sucks the neurotransmitters back up
Neuroglia
All other cells besides neurons in neural tissue
Types of neuroglia in the CNS
- Astrocyte
- Oligodendrocyte
- Microglia
Astrocyte
Has arm like structures and covers capillaries; they determine what from the blood gets in and doesn’t get in to the CNS
Oligodendrocyte
Makes myelin, but only in the CNS
Microglia
Important for immunity in the CNS
Types of neuroglia in the PNS
- Schwann cells
2. Satellite cells
Schwann cells
Make myelin in the PNS
Satellite cells
Important for immunity in the PNS
