Nervous System Flashcards
What is the function of the nervous system
A communication system that coordinates body function using electrical and chemical signals
What is the organization of the nervous system
Central nervous system (brain and spinal cord, interneurons), peripheral nervous system (sensory neurons and motor neurons), and enteric nervous system (digestive)
What types of neurons flow into the CNS vs out
Sensory (afferent) in, motor (efferent) out
What kinds of motor neurons are there
Somatic (skeletal muscles) and autonomic (smooth muscle, cardiac muscle, endocrine and exocrine glands, and adipose tissue)
What two cells primarily make up the nervous system
Neurons and glial cells (support cells)
What is the function of the myelin sheath
To speed up communication between neurons by insulating
What is the makeup of a neuron
Dendrite (input where signals are received), cell body/soma (nucleus), trigger zone (integration and spike initiation), axon (long distance conduction), and presynaptic axon terminal (signal output)
What are the nodes of Ranvier
The space between Schwann cells in the myelin sheath where the AP must be regenerated
What two glial cells can form a myelin sheath
Oligodendrocytes (in CNS, can wrap up to 15 axons), and Schwann cells (in PNS, wrap 1 axon)
Define presynaptic and postsynaptic cells
Presynaptic delivers the signal at a synapse and postsynaptic receives that signal
What are the two kinds of electrical signals in neurons
Graded potentials (local, from input region to trigger zone), and action potentials (long distance, from trigger zone to presynaptic axon terminal)
At the trigger zone what kind of electrical signals are present
Both graded potentials and action potentials
What are the 4 characteristics of graded potentials
Originate in input region because of opening of gated channels, decrease in amplitude with distance, amplitude and duration matches that of the stimulus, can be excitatory or inhibitory
What does it mean for graded potentials to be excitatory or inhibitory
Depending on ion flow, they can depolarize the cell and make it easier to produce AP (excitatory), or hyper polarize the cell and make it harder to produce AP (inhibitory)
What are the two kinds of graded potentials
Receptor potential (starts in sensory neuron, ligand/mechanical/voltage gated) and synaptic potential (EPSP or IPSP in interneurons and motor neurons, ligand gated)
What is a subtype of synaptic graded potentials
End-plate potential in skeletal muscle (can only excite, ligand gated)
How does a graded potential trigger an action potential
The summation of different graded potentials depolarize the cell, via opening of gated channels, past a certain threshold
What happens depending on where a graded threshold adds up to in relation to the threshold
Subthreshold = no AP, suprathreshold = AP, at threshold = 50/50 chance of AP
Which electrical signal is faster
Action potentials
What are the characteristics of action potentials
Don’t decrease in amplitude as the propagate, all-or-none (don’t summate, must reset)
How does action potential relate to the stimulus
Amplitude of the stimulus relates to AP frequency, stimulus duration is proportional to the amount of time that the AP is being produced
What types of channels are used in action potential in neurons and skeletal muscle
Voltage-gated channels (H-H Na+ and H-H K+)
What are the characteristics of the H-H Na+ channel
2 gates, closed when resting or depolarized, opens to let Na+ into the cell (depolarizes cell), time dependent inactivation, positive feedback loop
What are the characteristics of the H-H K+ channel
1 gate, closed when resting or repolarized, opens to allow K+ to flow out (hyperpolarizes), delayed compared to sodium