Nervous System Flashcards
What is the main function of the nervous system?
generates action potentials that aid in cell communication
What makes up the CNS?
The brain and the spinal cord
What makes up the PNS?
All nervous tissues/nerves outside of CNS
What is the difference between sensory and motor neurons?
Sensory - impulses from stimulus to CNS
Motor - impulses from CNS to target tissues
What neurons are afferent?
Sensory
What neurons are efferent?
Motor
Is the somatic nervous system voluntary or involuntary?
Voluntary
What occurs in the sympathetic division of the autonomic nervous system?
fight/flight
exercise and emergency action
What occurs in the parasympathetic division of the autonomic nervous system?
rest/digest activities
What does neuroglia do?
support/nourish/protect neurons
What is the role of a dendrite?
input portions of a neuron, housing numerous receptor sites for other cells to bind to
What is the role of an axon?
creates nerve impulses towards another neuron, muscle fibre or gland cell
What is the role of a myelin sheath?
insulates the axon, “swchan” cell inside
What is another name for the cell body?
Soma
a nucleus surrounded by cytoplasm that includes typical cellular organelles (lysosomes, mitochondria, and a Golgi complex)
Where is the Node of Ranvier?
exposed areas of the axon, increased number of protein channels
What are graded potentials?
small, localized electrical signals that occur along the dendrites and cell bodies of neurons, triggered by a stimulus
What type of potential influences voltage-gated channels?
Action potentials
What type of potential influences ligand-gated channels
Graded potentials
What type of potential influences leak channels?
Resting membrane potentials
What is the value of threshold?
-55mV
What is RMP?
-70mV
What does summation mean?
GP added together to cause an AP
Graded potentials must be summated (added together) to depolarize the membrane to threshold (-55mV) and generate an action potential
What is the difference between hyperpolarisation and depolarisation?
Hyperpolarisation - cell becomes more positive
Depolarisation - cell becomes more postitive
What is an action potential?
the electrical signal that neurons send along the length of the axon, cell needs to be DEPOLARIZED, do not vary in size (all or nothing)
Are AP all or nothing events?
Yes
What state are voltage-gated sodium channels in when they are inactive?
Ball and chain
Closed when gate shuts
Explain the events of an AP
Cell membrane is at resting state (-70mV)
Graded potentials summate to depolarizes axon hillock to threshold (-55mV)
Depolarization: At threshold, voltage-gated Na + channels open and sodium floods into cell (cell becomes less negative)
Repolarization: inactivation Na+ channels shut (ball and chain) and Na+ stops coming in, voltage-gated channels K+ channels open slowly (cell becomes more negative)
Hyperpolarization: K+ continues to leave cell (more negative)
Cell membrane returns to resting state (leak channels and pumps only –70mV)
What are the 2 types of refractory periods?
Absolute and relative
Where do AP occur along the neuron?
Axon hillock
Where do graded potentials summate?
Dendrites, cell body and axon
Do Shwann cells produce myelin?
Yes
Are myelinated axons generally faster for AP to move?
Yes, AP able to leap from myelin to myelin, therefore a faster process
What is the difference between saltatory conduction and continuous conduction?
saltatory - AP leaping with myelinated axons
continuous - leaky Na+ channels so need to be close together to conduct AP
How do you measure the intensity of an AP if it is an all or nothing event?
Stimulus intensity is coded by the frequency of action potentials;
Weak stimulus – lower frequency of AP
Strongest stimulus – higher frequency of AP
Where are synapses located?
Axon terminal
What molecule is involved in synaptic transmission?
Calcium (triggers vesicles to move)
What are EPSP’s and IPSP’s?
Excitatory post-synaptic potential - depolarisation (brings membrane closer to potential)
Inhibitory post-synaptic potential - hyper polarisation (brings membrane further away from potential)
What are the two types of summation?
Temporal - repeated from one
Spatial - various from different directions
Where are myelinated axons found why?
skeletal cells
where speed is crucial
What is the approx value that repolarisation occurs?
+30mV
Can a relative refractory period produce a 2nd AP?
Yes (if strong enough)
