Unit A Flashcards
The nervous system has two types of cells:
neurons and neuroglia
what do neurons do
transmit nerve impulses
what does neuroglia do
support and nourish neurons
what are the 3 types of neurons?
Sensory neurons, interneurons, and motor neurons
what do sensory neurons do?
take messages from sensory receptors to the central nervous system
what do interneurons do?
- they’re found entirely within the CNS
- they receive input from the sensory neurons
- communicate with motor neurons
- sum up information from other neurons
what do motor neurons do?
carry messages from the CNS to an effector (a muscle or gland)
in a neuron, the _________ are the extensions that receive signals from other neurons whereas the _______ conduct nerve impulses away from the cell body.
dendrites, axons
in the peripheral nervous system, the myelin sheath that wraps axons is made by a neuroglial cell called a
Schwann cell
in the central nervous system, the myelin sheath that wraps axons is made by a neuroglial cell called a
oligodendrocyte
the central nervous system contains grey and white matter. the _______ matter is composed of myelinated axons, whereas the ____ matter is composed of cell bodies and nonmyelinated axons
white, grey
where is white matter located?
deep in brain, surface of spinal cord
where is grey matter located?
surface of brain, deep in spinal cord
Myelinated axons have faster action potentials than nonmyelinated axons because they can jump between __________, which is called ___________
nodes of ranvier, saltatory conduction
the __________ is the region between an axon terminal and another neuron or an effector
synapse
communication between two neurons is carried out by chemicals called
neurotransmitters
two common examples of neurotransmitters are
Ach and NE
in what two ways are neurotransmitters removed from the synaptic cleft?
inactivation by enzymes or reuptake by the presynaptic neuron
in what four ways can drugs interfere with neurotransmitters?
- enhance release
- block release
- mimic their action
- interfere with their removal
think SSRI or SNRI
what is action potential?
the rapid change in electrical charge during a nerve impulse
- all or nothing phenomenon
- occurs if a stimulus reaches the threshold
- a strong stimulus does not change the strength of an action potential it just changes the frequency of firing
action potential step 1:
sodium (Na+) gates open
- sodium moves into the axon
- the charge changes from -70Mv to 35Mv
- this is called depolarization because the inside of the axon changes from negative to positive
action potential step 2:
potassium (K+) gates open
- K+ moves out of the axon
- the charge returns to -70Mv
- this is called repolarization because the inside of the axon returns to its original negative charge
refractory period
when an action potential has moved on, the previous section undergoes a refractory period.
during this time the sodium gates cannot reopen
potassium continues to diffuse out causing hyperpolarization. prevents the action potential from moving backwards
the central nervous system is composed of the _____ and _____
spinal cord, brain
