Nervous System (Part 1) Flashcards
What are the parts of a neuron?
- cell body
- axon
- dendrites
What is the function of axon?
transmits information away from the cell body
What is the function of dendrites?
transmits information to the cell body
What is nervous tissue low in?
cellularity
What is the function of glial cells?
support neurons and remove metabolic waste
What is the central nervous system made of?
brain and spinal cord
What are the two types of nervous systems?
central and peripheral
What pathways make up the peripheral nervous system?
sensory and motor
What are the two stimuli that sensory neurons register?
internal and external
What are examples of internal stimuli?
changes in blood pH, levels of hydration, temperature, pressure, volume
What are examples of external stimuli?
pain, vision, pressure touching ground
What is the function of the peripheral nervous system?
carry sensory information to brain and spinal cord to see if they need to do anything
What makes up the motor pathways?
somatic nervous system and autonomic nervous system
What is the somatic nervous system?
voluntary movement
What is the autonomic nervous system?
involuntary processes
What makes up the autonomic nervous system?
sympathetic nervous system and parasympathetic nervous system
What is the sympathetic nervous system?
“fight or flight,” you have to take action immediately to survive
What is the parasympathetic nervous system?
“rest and repose,” things you need to survive but not in a life or death situation
What is breathing mostly controlled by?
autonomic nervous system
What is the function of sensory receptors?
detect stimulus
What is the function of motor effectors?
respond to stimulus
What are components of the nervous system?
- receptors
- sensory neurons
- neurons inside the brain/spinal cord
- motor neurons
What kind of receptors are there?
internal and external
What do sensory neurons connect to?
connect to receptors
What do motor neurons do?
send info to effector organs
What are interneurons?
neurons between the sensory neurons and motor neurons
How is action stimulated? (steps)
- sensory neurons axon send info to dendrites of interneuron
- axon of interneuron sends signal to dendrites of motor neurons and stimulate action
What 3 types of neurons do vertebrates have?
- intra
- sensory
- motor
What do sensory neurons do?
send signals to interneurons
What do interneurons do?
take info and integrate it
What do motor neurons do?
take info from central nervous system and send to motor receptors/effector organs and do something about it
Where are motor neurons?
PNS
Where are sensory neurons?
PNS
where are interneurons?
CNS
What are myelin sheaths?
lipid based material that coats axon
What is the function of myelin sheaths?
to protect the signal so electrical signal doesn’t change because of location
Are all axon myelinated?
no
What are myelin sheaths like in the central nervous system?
- myelinated axons form white matter
- dendrites/cell bodies form gray matter (and unmyelinated axons)
What are myelin sheaths like in the peripheral nervous system?
-myelinated axons bundled to form nerves
What exists across every cell’s plasma membrane?
a potential difference
What is electricity?
a potential difference exists across every cell’s plasma membrane
Where is the negative pole for the potential difference across cell’s plasma membrane?
cytoplasmic side, inside
Where is the positive pole for the potential difference across cell’s plasma membrane?
extracellular side, outside
What is the potential difference across every cell’s plasma membrane created by?
movement of ions across membrane (through diffusion or protein channels)
What are ions?
charged molecule (positive or negative)
What is electricity caused by?
the flow of electrons from one pole to the other
Why is the inside of the cell more negatively charged than the outside?
- sodium-potassium pump
- Ion leakage channels
What does the sodium-potassium pump do?
brings 2 K+ into cell for every 3 Na+ it pumps out
What do the Ion leakage channels do?
allow more K+ to diffuse out than Na+ to diffuse in
What do non-stimulated neurons do?
maintains a resting potential
What is resting potential? (number)
average about -70 mV
What does the sodium-potassium pump have?
binding sites specific for K and Na
What does the sodium-potassium pump require?
energy, it is active transport
What are the steps of Sodium-Potassium pump?
- carrier in membrane binds intracellular sodium
- ATP phosphorylates protein with bound sodium
- Phosphorylation causes conformational change in protein, reducing affinity for NA+. The Na+ diffuses out
- this conformation has higher affinity for K+. Extracellular potassium binds to exposed sites
- binding of potassium causes dephosphorylation of protein
- dephosphorylation of protein triggers change back to original conformation, with low affinity for K+. K+ diffuses into the cell and cycle repeats
What are the steps of Sodium-Potassium pump?
- carrier in membrane binds intracellular sodium
- ATP phosphorylates protein with bound sodium
- Phosphorylation causes conformational change in protein, reducing affinity for NA+. The Na+ diffuses out
- this conformation has higher affinity for K+. Extracellular potassium binds to exposed sites
- binding of potassium causes dephosphorylation of protein
- dephosphorylation of protein triggers change back to original conformation, with low affinity for K+. K+ diffuses into the cell and cycle repeats
What brings K+ ions back into the cell?
attractive force
What leads to the resting potential?
balance between diffusional and electrical forces
Describe nerve impulse transmission? (slide 12)
when the cell is being stimulated, the -10 mV becomes more positive (when measuring it). Changes in membrane permeability contributes to this.
What changes when the neuron is excited?
the potential across the axon membrane
What is depolarization?
moves away from resting potential
What is repolarization?
moves back toward resting potential
What does the amount of voltage charge depend on?
if transmitting info
What do action potentials result from?
when depolarization reaches a threshold potential
What are action potentials produced by?
voltage gated ion channels
What is threshold potential?
target number of voltage
What is action potential?
change in voltage but depolarization (?) must meet a threshold in order for information to get transmitted
What channels are used for voltage-gates ion channels?
Voltage-gates Na+ and Voltage-gates K+ channels
Are voltage-gated ion channels the same as sodium-potassium pump?
no
What happens when the threshold voltage is reached?
sodium channels open rapidly
What does an influx of Na+ cause?
the membrane to depolarize
What happens after the sodium channels open?
potassium channel opens slowly
What does the efflux of K+ do?
repolarize the membrane
label diagram
LOOK AT NOTES
Describe nerve impulse transmission as in the diagram (what are the 4 phases?)
- resting phase
- rising phase
- top of curve
- falling phase
What happens during the resting phase of nerve impulse transmission?
equilibrium between diffusion of K+ out of cell and voltage pulling K+ into cell
What happens during the rising phase of nerve impulse transmission?
stimulus causes above threshold voltage
-sodium channel activation gate opens
What happens during top of curse of nerve impulse transmission?
maximum voltage reaches
- Na+ channel inactivation gate closes
- Potassium gate opens
What happens during falling phase of nerve impulse transmission?
undershoot occurs as excess potassium diffuses out before potassium channel closes
- Na+ channel inactivation gate closed
- Potassium gate opens
What happens after the falling phase of nerve impulse transmission?
equilibrium restored
-sodium channel activation gate closes and inactivation gate opens
What are the three phases of action potential?
rising, falling, undershoot
Action potentials are always _______ events with _______ amplitude.
all-or-nothing; same
What is intensity of a stimulus by?
the frequency, not the amplitude
What is nerve impulse transmission considered?
positive feedback loop
How far does action potential travel?
the length of the axon
What does the influx of Na+ do for action potential? (slide 19)
depolarizes the adjacent region to threshold, the next region produces its own action potential and the previous region repolarizes back to resting potential
What are synapses?
intercellular junctions
What does the presynaptic cell do?
transmits action potential
What does the postsynaptic cell do?
receives the action potential
What are the two types of synapses?
electrical and chemical
What do electrical synapses involve?
direct cytoplasmic connections between the two cells formed by gap junctions
Are electrical synapses common?
rare in vertebrates
What do chemical synapses have?
a synaptic cleft between the two cells
What does the end of presynaptic cell contain (for chemical?)?
synaptic vesicles
What do synaptic vesicles contain?
neurotransmitters
What is a synaptic cleft?
a physical space
What does action potential trigger an influx of?
Ca^2+
What happens to synaptic vesicles after an influx of Ca^2+?
fuse with cell membrane
What happens to neurotransmitter after an influx of Ca^2+?
released by exocytosis
What happens after neurotransmitter released by exocytosis?
diffuses to other side of cleft and binds to chemical- or ligand-gated receptor proteins
What is the neurotransmitter action terminated by?
enzymatic cleavage or cellular uptake
Why are receptors degraded by enzymes or reuptaked?
cuz can’t remain attached entire time
What is one of the most common neurotransmitters?
Acetylcholine (ACh)
What is the neuromuscular junction?
the synapse between a nerve and muscle
What does Acetylcholine bind to?
ligand-gated receptor in the postsynaptic membrane
What does Acetylcholind produce?
a depolarization called an excitatory postsynaptic potential (EPSP)
What does an excitatory postsynaptic potential (EPSP) stimulate?
muscle contractions
What does Acetylcholinesterase (AChE) do?
degrade acetylcholine
What does the degradation of acetylcholine cause?
muscle relaxation
What is acetylcholinesterase common in?
vertebrates and invertebrates
What does acetylcholinesterase do in vertebrates?
stop muscle contractions (muscle relaxation)
What does acetylcholinesterase do in insects?
causes insects muscle to contract (this is put in insecticide)
What are other neurotransmitters?
- amino acids
- biogenic amines
- neuropeptides
What is the only major phylum without nerves?
sponges
What has the simplest nervous system?
Cnidarians
What is the nervous system like in Cnidarians?
neurons linked to each other in a nerve net, no associative activity
What are the simplest animals with associative activity?
free-living flatworms (phylum Platyhelminthes)
What phyla do not exhibit cephalization outside of ones already mentioned?
echinoderms
