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respond to stimulus
carry impulses from sensory receptors to the central nervous system
carry impulses from the CNS to effectors
help provide more complex reflexes and higher associative learning
sensory and motor neurons constitute the ______
Peripheral nervous system
2 divisions of autonomic nervous system
- 1. sympathetic- fight or flight
- 2. Parasympathetic-resting and relaxing
- these two counter balance each other
the ______consists of the brain and spinal cord
central nervous system
the ______ consists of sensory and motor neurons
peripheral nervous system
stimulates skeletal muscles
stimulates smooth and cardiac muscles, as well as glands.
structure of a neuron
- cell body- enlarged part containing nucleus
- dendrites- short, cytoplasmic extensions that receive stimuli
- axon- Single long extension that conducts impulses away from cell body
Neurons are supported both structurally and functionally by cells called _________
produce myelin sheaths in peripheral nervous system
produce myelin sheaths in the central nervous system
In the CNS, myelinated axons form ______ matter
In the CNS, dendrites/ cell bodies form _____ matter
the inside of the cell is more negative/ positive that the outside because of what 2 things
- 1. sodium-potassium pump= brings two K+ into cell for every 3 Na+ pumped out
- 2. Ion channels= Allow more K+ to diffuse out than Na+ to diffuse inward.
the cytoplasmic side of a cell is _______ with respect to the outside. so it is a _________ pole
the extracellular fluid side of a cell is ________ with respect to the cytoplasm, so it is a ______ pole
When a neuron is not being stimulated, it maintains a ______
what is the normal range of resting potentials?
- -40 to -90 millivolts
- average about -70 mV
balance between diffusional and electrical forces leads to the ___ _____
What are the two types of potentials?
- graded potentials
- action potentials
small transient changes in membrane potential due to activation of gated ion channels
chemically-gated or ligand-gated channels
ligands are hormones or neurotransmitters that bind to receptors and cause channels to open, thus causing changes in cell membrane permeability
makes the membrane potential more positive
makes it more negative
is the ability of graded potentials to combine
result when depolarization reaches the threshold potential
the action potential is caused by ___-____ ___ ____
voltage-gated ion channels
two types of voltage gated channels
- voltage gated Na+ channels- depolarization
- voltage-gated K+ channels- hyperpolarization
When the threshold voltage is reached, ___-___ ___ ____ open rapidly
voltage-gated sodium channels
When the threshold voltage is reached which type of channel opens slowly?
voltage-gated potassium (K+) channel
three phases of action potential
- 1. rising
- 2. falling
- 3. undershoot
____ ____ are always separate, all-or-none events with the same amplitude
the intensity of a stimulus is coded by the ________ of action potentials
Each action potential, in its rising phase, reflects a reversal in membrane ______
meanwhile, during the _______ phase, the previous region repolarizes back to the resting membrane potential.
Two ways to increase velocity of conduction
- 1. axon has a large diameter-less resistance to flow. found primarily in invertebrates
- 2. axon is myelinated-action potential is only produces at the nodes of Ranvier. Impulse jumps from node to node- saltatory conduction.
transmits action potential
receives action potential
what are the two types of Synapses?
- Electrical synapses
- Chemical synapses
____ _____ involve direct cytoplasmic connections between the two cells formed by gap junctions
- Electrical Synapses
- spliced together
- relatively rare in vertebrates
____ ____ have a synaptic cleft between the two cells
End of presynaptic cell contains synaptic vesicles packed with _______
neurotransmitters. these travel between communicating cells
Types of neurotransmitters
- Amino acids
- Biogenic amines
- several others
- control skeletal muscle. crosses the synapse between a motor neuron and a muscle fiber.
- Binds to a ligand gated receptor in the post synaptic membrane.
synapse between a motor neuron and a muscle fiber
when Acetylcholine binds to a ligand-gated receptor, this produces a depolarization called an ___ ___ ___
excitatory postsynaptic potential
Acetylcholinesterase degrades ______ and causes muscle ______
Acetylcholine ; relaxation
- amino acid
- major excitatory neurotransmitter in the vertebrate CNS
Glycine and GABA are ______ neurotransmitters
When Glycine and or GABA open ligand-gated channes for Cl- the produce a ________ called an ____ ____ ____
hyperpolarization ; inhibitory postsynaptic potential
3 Biogenic amines and their effects
- Epinephrine (adrenaline) and Norepinephrine are responsible for the "fight or flight" response
- Dopamine is used in some areas of the brain that control body movements.
- Serotonin is involved in the regulation of sleep
is released from sensory neurons activated by painful stimuli
Intensity of pain perception depends on ______ and _____
enkephalins ; endorphins
_____ ____ ,a gas, causes smooth muscle ______
Nitric oxide ; relaxation
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