Chapter 3 Flashcards
neurons
cells in the nervous system that communicate with one another to perform information processing tasks
neurons are complex structures that are composed of three basic parts:
the cell body, the dendrites, and the axon
cell body (also called the soma)
largest component of the neuron that coordinates information-processing tasks and keeps the cell alive
functions such as protein synthesis, energy production, and metabolism occur here
the cell body has a nucleus that contains DNA, and is surrounded by a semi-permeable membrane
dendrites
receive information from other neurons and relay it to the cell body
look like tree branches at the terminal ends
axon
carries information to other neurons, muscles, or glands
axons are very long and can stretch from the top of the spine to the big toe
synapse
the junction or region between the axon of one neuron and the dendrites or cell body of another
in many neurons, the axon is covered by a
myelin sheath
myelin sheath
an insulating layer of fatty material
the myelin sheath is composed of
glial glands
glial glands
support cells found in the nervous system.
some glial cells digest parts of dead neurons, others provide physical and nutritional support for neurons, and others form myelin to help the axon carry information more efficiently.
multiple sclerosis
deteriorating of the myelin sheath
there are three types of neurons, each performing a distinct function:
sensory neurons, motor neurons, and interneurons
sensory neurons
receive information from the external world and convey this information to the brain via the spinal cord
they have specialized endings on their dendrites that receive signals for light, sound, touch, taste, and smell
motor neurons
carry signals from the spinal cord to the muscles to produce movement
have long axons that can stretch to muscles in the extremities
most of the nervous system is composed of
interneurons
interneurons
they connect sensory neurons, motor neurons, and other interneurons
Some interneurons carry information from sensory neurons into the nervous system, others carry information from the nervous system to motor neurons, and still others perform a variety of information-processing functions within the nervous system
Which of the following is NOT a function of a neuron?
a processing information
b communicating with other neurons
c nutritional provision
d sending messages to body organs and muscles
c
Signals from other neurons are received and relayed to the cell body by
a the nucleus.
b dendrites.
c axons.
d glands.
b
Signals are transmitted from one neuron to another
a across a synapse.
b through a glial cell.
c by the myelin sheath.
d in the cell body.
a
Which type of neuron receives information from the external world and conveys this information to the brain via the spinal cord?
a sensory neuron
b motor neuron
c interneuron
d axon
a
Neurons have a natural electric charge called the
resting potential
resting potential
the difference in charge between the inside and outside of a neuron’s cell membrane
The resting potential arises from the difference in concentrations of________inside and outside the neuron’s cell membrane
ions
ions can carry a ______________charge
positive or negative
conduction
information travels inside a neuron via an electrical signal that travels from the dendrite to the cell body to the axon
transmission
a signal has to be transmitted from one neuron to another, usually via chemical messengers traveling across the synapse
In the resting state, there is a high concentration of a positively charged ion_______ as well as negatively charged ________inside the neuron’s cell membrane compared to outside it. By contrast, there is a high concentration of positively charged________and negatively charged_________outside the neuron’s cell membrane.
potassium (K+), protein ions (A–),
sodium ions (Na+), chloride ions (Cl–)
Electric stimulation causes an
action potential
resting potential is________because it creates the environment for a possible electrical impulse.
potential energy
The concentration of K+ inside and outside a neuron is controlled by channels in the cell membrane that allow K+ molecules to flow in and out of the neuron. In the resting state, the channels that allow K+ molecules to flow freely across the cell membrane are open, while channels that allow the flow of Na+ and the other ions are generally closed. Because of the naturally higher concentration of K+ molecules inside the neuron, some K+ molecules move out of the neuron through the open channels, leaving the inside of the neuron with a charge of about -70 millivolts relative to the outside
.
action potential
an electrical signal that is conducted along the length of a neuron’s axon to a synapse
The action potential occurs only when the electric shock reaches a certain level, or
threshold
the action potential is
all or none: electric stimulation below the threshold fails to produce an action potential, whereas electric stimulation at or above the threshold always produces the action potential. The action potential always occurs with exactly the same characteristics and at the same magnitude regardless of whether the stimulus is at or above the threshold.
The action potential occurs when there is a change in the state of the axon’s membrane channels. Remember, during the resting potential, the channels that allow K+ to flow out are open, resulting in a net negative charge (–70 millivolts) relative to the outside. However, during an action potential, these channels briefly shut down, and channels that allow the flow of positively charged sodium ions (Na+) are opened (see FIGURE 3.3b). We’ve seen already that Na+ is typically much more concentrated outside the axon than inside. When the channels open, those positively charged ions (Na+) flow inside, increasing the positive charge inside the axon relative to the outside. This flow of Na+ into the axon pushes the action potential from negative (–70 millivolts) to positive (+40 millivolts).
.
During this period when the ions are imbalanced, the neuron cannot initiate another action potential, so it is said to be in a___________,the time following an action potential during which a new action potential cannot be initiated.
refractory period
Breaks in the myelin sheath are called__________. The electric impulse jumps from node to node, thereby speeding the conduction of information down the axon.
nodes of ranvier
When an electric current passes down the length of a myelinated axon, the charge seems to “jump” from node to node rather than traverse the entire axon (Poliak & Peles, 2003). This process is called____________,and it helps speed the flow of information down the axon.
saltatory conduction
axons usually end in
terminal buttons (knob-like structures that branch out from an axon)
A terminal button is filled with tiny vesicles, or “bags,” that contain_________
neurotransmitters
neurotransmitters
chemicals that transmit information across the synapse to a receiving neuron’s dendrites
The dendrites of the receiving neuron contain_________
receptors
receptors
parts of the cell membrane that receive neurotransmitters and either initiate or prevent a new electric signal.
The action potential travels down the length of the axon of the sending neuron, or__________to the terminal buttons, where it stimulates the release of neurotransmitters from vesicles into the synapse.
presynaptic neuron
These neurotransmitters float across the synapse and bind to receptor sites on a nearby dendrite of the receiving neuron, or______________
postsynaptic neuron
A new electric signal is initiated in that neuron, which may in turn generate an action potential in that neuron. This electrochemical action, called____________, allows neurons to communicate with one another.
synaptic transmission
reuptake
neurotransmitters can be reabsorbed by the terminal buttons of the presynaptic neuron’s axon
enzyme deactivation
neurotransmitters can be destroyed by enzymes in the synapse
autoreceptors
neurotransmitters can bind to receptor sites called autoreceptors on the presynaptic neuron
Acetylcholine (ACh)
Acetylcholine (ACh) is a neurotransmitter involved in a number of functions, including voluntary motor control. Acetylcholine is found in neurons of the brain and in the synapses where axons connect to muscles and body organs, such as the heart. Acetylcholine contributes to the regulation of attention, learning, sleeping, dreaming, and memory
Dopamine
is a neurotransmitter that regulates motor behavior, motivation, pleasure, and emotional arousal. Because of its role in associating actions with rewards, dopamine plays a role in drug addiction
Glutamate
the major excitatory neurotransmitter in the brain, meaning that it enhances the transmission of information between neurons
GABA (gamma-aminobutyric acid)
the primary inhibitory neurotransmitter in the brain, meaning that it tends to stop the firing of neurons
Norepinephrine
involved in vigilance, or a heightened awareness of dangers in the environment
Serotonin
Serotonin is involved in the regulation of sleep and wakefulness, eating, and aggressive behavior
Endorphins
chemicals that act within the pain pathways and emotion centers of the brain. Endorphins help dull the experience of pain and elevate moods
Agonists
are drugs that increase the action of a neurotransmitter
Antagonists
drugs that block the function of a neurotransmitter
The Hindbrain
The hindbrain coordinates information coming into and out of the spinal cord and controls the basic functions of life. It includes the medulla, the reticular formation, the cerebellum, and the pons.
medulla
an extension of the spinal cord into the skull that coordinates heart rate, circulation, and respiration
reticular formation
which regulates sleep, wakefulness, and levels of arousal
cerebellum
a large structure of the hindbrain that controls fine motor skills
pons
a structure that relays information from the cerebellum to the rest of the brain
midbrain
The midbrain is important for orientation and movement. It includes structures such as the tectum and tegmentum.
the midbrain would orient you toward or away from pleasurable or threatening stimuli in the environment
subcortical structures
areas of the forebrain housed under the cerebral cortex near the center of the brain
includes the thalamus, hypothalamus, pituitary gland, hippocampus, amygdala, and basal ganglia, and these structures play an important role in relaying information throughout the brain, as well as pergorming specific tasks that allow us to think, feel, and behave as humans
thalamus
relays and filters information from the senses and transmits the information to the cerebral cortex
hypothalamus
regulates body temperature, hunger, thirst, and sexual behavior
pituitary gland
the ‘master gland’ of the body’s hormone-producing system, which releases hormones that direct the functions of many other glands in the body.
hippocampus
critical for creating new memories and integrating them into a network of knowledge so that they can be stored indefinitely in other parts of the cerebral cortex
amygdala
plays a cental role in many emotional processes, particularly the formation of emotional memories
basal ganglia
a set of subcortical structures that directs intentional movements
cerebral cortex
the outermost layer of the brain, visible to the naked eye, and divided into two hemispheres
corpus callosum
connects large areas of the cerebral cortex on each side of the brain and supports communication of information across the hemispheres
occipital lobe
processes visual information
parietal lobe
processes information about touch, and includes the somatosensory cortex
motor cortex
a strip of brain tissue in the frontal lobe, represents and controls different skin and body areas on the contralateral side of the body
somatosensory cortex
the somatosensory cortex represents skin areas of particular parts on the contralateral side of the body.
temporal lobe
responsible for hearing and language. contains the primary auditory cortex
frontal lobe
specialized areas for movement, abstract thinking, planning, memory, and judgement
association areas
composed of neurons that help provide sense and meaning to information registered in the cortex
mirror neurons
active when an animal performs a behavior, such as reaching for or manipulating an object, and they are also activated when another animal observes the first animal as it performs the same behavior
plasticity
the ability to be molded or can adapt to changes in sensory inputs
the brain is platic:
functions that were assigned to certain areas of the brain may be capable of being reassigned to other areas of the brain accommodate changing input from the environment
