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What are neurons?
nerve cells that transfer information within the body
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What are the two types of signals neurons use to communicate?
electrical signals (long distance) and chemical signals (short distance)
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Define central nervous systems:
the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord.
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Define the peripheral nervous system:
the nervous system outside the brain and spinal cord.
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What is ganglia?
simple clusters of neurons in which processing of information takes place
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Nervous systems process information in three stages:
sensory input, integration, and motor input
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What is a synapse?
a junction between an axon and another cell
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What does the synaptic terminal do?
it passes information across the synapse in the form of chemical messengers called neurotransmitters
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What are neurotransmitters?
chemical messengers
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What does an axon hillock do?
joins the cell body to the axon
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Information is transmitted from a _____________ to a _____________ (give examples of each)
presynaptic cell (a neuron), postsynaptic cell (a neuron, muscle cell, or gland cell)
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Most neurons are nourished or insulated by cells called:
glia (most of the cells in the brain)
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Glia cells have numerous functions:
- blood-brain barrier-protects the neurons
- cerebral spinal fluid- cushions the brain
- microglia- protects the nervous system from microorganisms
- myelin sheath- protects axon
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Tumors arise from:
uncontrolled cell division
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Tumors result in:
mass of cells which can be malignant (cancerous) or benign (non-cancerous)
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Due to their structure, neurons:
do not divide
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Most primary tumors are:
gliomas or meningiomas
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Secondary tumors can arise from:
malignant tumors originating in other regions of the body
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What maintains a resting potential of a neuron?
ion pumps and ion channels
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What is membrane potential?
a voltage across its plasma membrane
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What is the resting potential?
the membrane potential of a neuron not sending signals
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In a mammalian neuron at resting potential, the concentration of ___ is greater inside the cell, while the concentration of ___ is greater outside the cell
K+, Na+
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What do sodium potassium pumps use to maintain these K+ and Na+ gradients across the plasma membrane?
energy of ATP
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What is a resting potential?
the membrane potential of a resting neuron one that is not sending signals
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The opening of ________ in the plasma membrane converts chemical potential to electrical potential
ion channels
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A neuron at ___________ contains many open K+ channels (K+ leak channels, not voltage-gated potassium channels) and fewer open Na+ channels; K+ diffuses out of the cell
resting potential
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Neurons contain ______________ that open or close in response to stimuli
voltage gated ion channels
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Leak Potassium channels:
always open and helps set the resting potential
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Voltage gated potassium channel:
important for restoring membrane potential following depolarisation. Opens slowly causing delayed efflux of potassium
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Voltage gated sodium channels:
important for depolarising membrane (making more positive) during action potentials. Opens rapidly allowing influx of sodium
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Voltage gated calcium channels:
Opens when membrane depolarises and lets calcium flow into cell. Important for synaptic release.
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What occurs in depolarization:
- Gated Na+ channels open
- Na+ diffuses into the cell
- the membrane potential becomes less negative
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What is an action potential?
nerve impulse or signal that carries information along the axon
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When does an action potential occur?
when depolarization reaches threshold (-55mV)
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What is the resting potential?
-70 mV
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The ______ of action potentials can reflect the strength of stimulus
frequency
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The refractory period is:
a result of a temporary inactivation of the Na+ channels
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