Chapter 48/49 Flashcards
Neurons
Nerve cells that transfer information within the body
Neurons have two types of signals to communicate:
- Electrical signals (long-distance)
- Chemical signals (short-distance) AKA neurotransmitters
Most of a neuron’s organelles are in the _.
Cell body
Most neurons have _, highly branched extensions that receive signals from other neurons.
Dendrites
Axon
Typically a much longer extension that transmits signals to other cells
Synapse
A junction between the axon and another cell
Information is transmitted from a _ cell (a neuron) to a _ cell (a neuron, muscle, or gland cell).
Presynaptic; postsynaptic
Most neurons are nourished or insulated by cells called _ or _ cells.
Glia; glial
_ have numerous functions to nourish, support, and regulate neurons.
Glia (or glial cells)
Astrocytes
Form tight junctions in capillaries of the CNS, resulting in a blood-brain barrier which restricts the entry of most substances into the brain
Nervous systems process information in three steps:
1) Sensory input
2) Integration
3) Motor output
Sensors detect external stimuli and internal conditions and transmit information along _ neurons (step 1).
Sensory
Sensory information is sent to the brain or ganglia (in lower eukaryotes), where _ integrate the information (step 2).
Interneurons
Motor output leaves the brain or ganglia via _ neurons, which trigger muscle or gland activity (step 3).
Motor
Many animals have a complex nervous system that consists of:
- A central nervous system (CNS)
- A peripheral nervous system (PNS)
Central nervous system (CNS)
Where integration takes place; this includes the brain and a nerve cord (spinal cord)
Peripheral nervous system (PNS)
Carries information into and out of the CNS
The neurons of the PNS, when bundles together, form _.
Nerves
Ion pumps and ion channels establish the _ of a neuron.
Resting potential
Every cell has a voltage (difference in electrical charge) across its plasma membrane called a _.
Membrane potential
The _ is the membrane potential of a neuron not sending signals.
Resting potential
Changes in membrane potential act as _, transmitting and processing information.
Signals
In a mammalian neuron at resting potential, the concentration of K+ is highest _ the cell, while the concentration of Na+ is highest _ the cell.
Inside; outside
_ pumps use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane.
Sodium-potassium
These concentration gradients represent chemical _ that gets converted to electrical potential when ion channels open.
Potential energy
When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative. This is _, an increase in magnitude of the membrane potential.
Hyperpolarization
Opening other types of ion channels triggers a _, a reduction in the magnitude of the membrane potential.
Depolarization
If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an _.
Action potential
Action potential
Signal conducted by axons
Action potentials have a _ magnitude, are all-or-none, and transmit signals over long distances.
Constant
In vertebrates, axons are insulated by a _, which causes an action potential’s speed to increase.
Myelin sheath
The speed of an action potential increases with the axon’s _.
Diameter
Myelin sheaths are made by glia (oligodendrocytes in the CNS, and _ cells in the PNS).
Schwann
Action potentials are formed only at _, gaps in the myelin sheath where voltage-gated Na+ channels are found.
Nodes of Ranvier
Action potentials in myelinated axons _ between the nodes of Ranvier.
Jump
At electrical synapses, the current flows from one neuron to another through _.
Gap junctions
At _ synapses, a chemical neurotransmitter carries information between neurons.
Chemical
Most synapses are _ synapses.
Chemical
The synaptic terminal of one axon passes information across the synapse in the form of chemical messengers called _.
Neurotransmitters
Acetylcholine (ACH)
A common neurotransmitter in animals
Acetylcholine is involved in:
- Muscle stimulation
- Memory formation
- Learning
A number of _ disrupt acetylcholine neurotransmission (this leads to neurodegenerative diseases).
Toxins
Acetylcholine is just one of more than _ known neurotransmitters.
100
Neurotransmitters (other than acetylcholine) fall into four classes:
- Amino acids
- Biogenic amines
- Neuropeptides
- Gases
The human brain contains about 100 billion neurons, organized into _ more complex than the most powerful supercomputers.
Circuits
What do powerful imaging techniques allow researchers to do?
Monitor multiple areas of the brain while the subject performs various tasks
Nervous systems consist of circuits of _ and supporting cells.
Neurons
The simplest animals with nervous systems, the cnidarians, have neurons arranged in _.
Nerve nets
Nerve net
A series of interconnected nerve cells
More complex animals have _, in which the axons of multiple neurons are bundled together.
Nerves
Nerves
Channel and organize information flow through the nervous system
Bilaterally symmetrical animals exhibit _, the clustering of sensory organs at the front end of the body (head).
Cephalization
The simplest cephalized animals, flatworms, have:
- A central nervous system (CNS), with a brain and longitudinal nerve cords, and
- A peripheral nervous system (PNS), with neurons carrying information into and out of the CNS
