Nerve Cells and Neuron Potentials 1 Flashcards
What is considered afferent sensory information?
- somatic senses
- special senses
- visceral senses
Afferent sensory information (input/output) to/from the brain and spinal cord.
input
Efferent sensory information (input/output) to/from the brain and spinal cord.
output
What are the 2 categories of efferent sensory information?
- somatic
- autonomic
Somatic output goes to _____ ______.
skeletal muscles
What are the 2 categories of autonomic output?
- sympathetic
- parasympathetic
Sympathetic output goes to …
- cardiac muscle
- smooth muscle
- glands
Parasympathetic output goes to …
enteric nervous system
Enteric nervous system goes to …
gastrointestinal tract
Name and describe the 2 cells of the nervous system.
- neurons: excitable cells
- glial cells: support cells
What is the synapse?
site of communication between 2 neurons or between a neuron and an effector organ
What is the soma?
- cell body
- contains nucleus and most organelles
What do the dendrites do?
reception of incoming information
What does the axon do?
transmits electrical impulses called action potentials
What is the axon hillock?
where the axon originates and action potentials are initiated
What happens at the axon terminal?
releases neurotransmitter
What is anterograde transport?
from soma to axon terminal
What is retrograde transport?
- from axon to soma
- microtubules and neurofilaments
What is considered slow retrograde transport?
0.5-40 mm/day
What is considered fast retrograde transport?
100-400 mm/day
Describe leak ion channels.
- always open
- throughout the neuron
- resting membrane potential
Describe gated ion channels.
- open or close in response to binding
- dendrites and cell body
- synaptic potentials
Describe voltage-gated ion channels. Give examples.
- open or close in response to changes in membrane potential
- ex. sodium and potassium channels
- ex. calcium channels
Where are sodium and potassium channels located? What goes through them?
- throughout, more in the axon (hillock)
- action potentials
Where are the calcium channels? What are they responsible for?
- axon terminal
- neurotransmitter release
Afferent neurons (input/output).
input
Efferent neurons (input/output).
output
______ make up 90% of all cells in the nervous system.
glial cells
What are the 4 types of glial cells in the CNS?
- astrocytes
- microglia
- oligodendrocytes
- ependymal cells
What are the 2 types of glial cells in the PNS?
- satellite cells
- Schwann cells (neurolemmocytes)
What are the 2 myelin forming cells?
- oligodendrocytes
- Schwann cells
One oligodendrocyte:
- forms several myelin sheaths
- myelinates sections of several axons
One Schwann cell:
- forms 1 myelin sheath
- myelinated one section of an axon
Describe the resting membrane potential. What is the resting membrane potential for neurons?
- more negative charges inside and positive charges outside the cell
- ~-70 mV
Name 2 critical factors for resting membrane potential.
- ion concentration gradients (sodium and potassium ions)
- membrane permeability to these ions
How is membrane permeability changed?
- ion channels
- chemical and electrical forces
- concentration and electrical charge
What is the permeability for the resting membrane potential of neurons?
25x more permeable to K+ vs Na+
Describe ion distribution for the resting membrane potential of neurons.
- outside cell: sodium and chloride
- inside cell: potassium and organic anions
What do chemical driving forces do to K+ and Na+?
- K+ out
- Na + in
What happens when the cell becomes more permeable to K+?
- more K+ leaves the cell than Na+ enters
- inside of the cell = negative
What happens when electrical forces develop?
- Na+ into cell
- K+ into cell
- K+ outflow slows
- Na+ inflow speeds
What happens to Na+ and K+ when a steady state develops?
- Na+ and K+ in/outflow is balanced
- -70 mV
A small Na+ leak at rest would be …
- high force
- low permeability
A small K+ leak at rest would be …
- low force
- high permeability
What maintains the resting potential?
sodium pump
If the membrane potential is not at equilibrium for an ion:
- the electrochemical force is not 0
- force acts to move ions across the membrane in the direction favouring the equilibrium
- farther from equilibrium = greater force for movement
Describe the forces acting on ions at -70 mV.
- membrane is further away from Na+ equilibrium
- a stronger force to move Na+ to equilibrium is present
Each ion has it’s own _____.
force
The resting membrane potential is closer to the _________ equilibrium potential.
- potassium (-94 mV)
- Na equilibrium potential is (+60 mV)
