Unit 2 Flashcards
phrenology
A pseudoscience that claimed the study of bumps on the skull could reveal a person’s underlying brain size and associated mental abilities and personality traits.
neuron
A neuron is a nerve cell that is the basic building block of the nervous system. Neurons are similar to other cells in the human body in a number of ways, but there is one key difference - neurons are specialized to transmit information throughout the body.
cell body (soma)
The part of the neuron that contains the nucleus - the life support centre of the cell.
dendrites
The bushy branching extensions of a neuron that receive and integrate messages and then conduct impulses toward the cell body.
axon
The neuron extension that conducts neural impulses to other neurons or muscle or gland cells.
terminal branches (buttons)
The terminal branches (buttons) are located at the end of the neuron and are responsible for sending the signal on to other neurons (or muscles or glands). At the end of the terminal button is a gap known as a synapse.
myelin sheath
The insulating layer around many axons that increases the speed of conduction of nerve impulses. The myelin sheath is interrupted by small gaps, called nodes of Ranvier, which are spaced about every millimeter along the axon.
nodes of Ranvier
Regularly spaced gaps in the myelin sheath surrounding an axon. The gaps permit the exchange of ions across the plasma membrane at those points, allowing the nerve impulse to leap from one node to the next in so-called saltatory conduction along the axon.
glial cell (neuroglia)
Non-neuronal tissue in the nervous system that provides structural, nutritional, and other kinds of support to neurons.
oligodendroglia
Oligodendrocytes are a type of glial cells that form myelin sheath on neurons in the central nervous system and Schwann cells in the peripheral nervous system.
Schwann cells
Schwann cells are a type of glial cells that form myelin sheath on neurons in the peripheral nervous system.
astrocytes
Astrocytes are star-shaped glial cells and form the matrix in which neural cells are embedded. They also absorb dead neural cells
action potential
The change in electric potential along the axon of a neuron during the transmission of a nerve impulse It is marked by a rapid depolarization of the cell’s plasma membrane, from a resting potential of about –70 mV (inside negative) to about +40 mV (inside positive), and back again, after a slight hyperpolarization, to the resting potential. Each action potential takes just a few milliseconds.
resting membrane potential
The electric potential across the plasma membrane of a neuron when it is in the nonexcited, or resting, state. It is usually in the range of -70mV representing an excess of negatively charged ions on the inside of the membrane.
sodium-potassium pump
This pump is embedded in the membrane and maintains the resting membrane potential. This means that it keeps pumping more sodium ions (Na+) out of the neuron and fewer potassium ions (K+) into the neuron This keeps the inside of the neuron more negative which keeps the resting potential of -70mV.
selective permeability
The membrane of the axon is selectively permeable, which means that it has channels or “gates” that only allow certain ions to cross the membrane and only at certain times.
all-or-none response
The all-or-none law is a principle that states that the strength of a response of a nerve cell is not dependent upon the strength of the stimulus. Essentially, there will either be a full response or there will be no response at all for an individual neuron.
depolarization
A reduction in the electric potential across the membrane of neurons, such that the inner surface of the membrane becomes less negative in relation to the outer surface. Depolarization occurs when the membrane is stimulated and sodium ions (Na+) flow into the cell. If the stimulus intensity exceeds the excitatory threshold of the neuron, an action potential is created and a nerve impulse is propagated.
threshold
Threshold is the minimum stimulus intensity that triggers an action potential in a neuron. It is usually -55mV.
repolarization
The change in membrane potential returns it to a negative value just after the depolarization phase of an action potential.
hyperpolarization
Repolarization always leads first to hyperpolarization, a state in which the membrane potential is more negative than the default membrane potential.For example, it might go to -100mV before returning to -70mV.
refractory period
This is the period after an action potential has been generated but before the next one can be generated. The next action potential in a neuron cannot be generated until the membrane has returned to normal. This refractory period is to ensure that the signal only travels in one direction.
synapse
The specialized junction through which neural signals are transmitted from one neuron (the presynaptic neuron) to another (the postsynaptic neuron). In most synapses, the terminal button of the axon of a presynaptic neuron faces the dendrite or cell body of the postsynaptic neuron across a narrow gap, the synaptic cleft.
synaptic gap (cleft)
The gap within a synapse between the terminal button ending of the axon of one neuron and the dendrite or cell body of a neighboring neuron. The synaptic cleft is typically 20 to 30 nm wide. Also called synaptic gap.
synaptic vesicles
Numerous small spherical sacs in the terminal button ending of the axon of a presynaptic neuron that contain molecules of neurotransmitter. The transmitter is released into the synaptic cleft when a nerve impulse arrives at the terminal button.
reuptake
The process by which neurotransmitter molecules released at a synapse are reabsorbed by the presynaptic neuron that released them.
excitation
The binding of a neurotransmitter to a receptor site produces a chemical reaction that depolarizes (excites) the cell membrane. If threshold is reached, an action potential is created and an impulse is sent down the neuron.
inhibition
The binding of a neurotransmitter to a receptor site produces a chemical reaction that will hyperpolarize the membrane. This makes it more difficult for the neuron to be excited and reach threshold and therefore inhibits its function.
neurotransmitters
Chemicals are released by neurons to mediate the transmission of nerve signals across the synapses between neurons. When triggered by a nerve impulse, the neurotransmitter is released from the terminal button, travels across the synaptic cleft, and binds to and reacts with receptor molecules in the postsynaptic membrane.
acetylcholine (ACh)
Neurotransmitter that enables muscle contraction, learning and memory.
dopamine
Neurotransmitter that influences learning movement, attention, and emotion.
serotonin
Neurotransmitter that affects mood, hunger, sleep, and arousal.
endorphins
Neurotransmitters that influence the perception of pain and pleasure.
agonist
A drug or chemical that increases the activity of a neurotransmitter
antagonist
A drug or chemical that inhibits or decreases the activity of a neurotransmitter.
reuptake inhibitor
A drug or chemical that stops the reuptake of a neurotransmitter in the presynaptic axon terminal. This leaves more of the neurotransmitter in the synapse, creating an enhanced effect of that neurotransmitter.
nervous system
The body’s speedy , electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems.
central nervous system
The part of the nervous system that contains the brain and spinal cord. All the nerves housed within bone (skull and vertebrae).
peripheral nervous system
The sensory and motor neurons that branch out from the central nervous system and reach the extremities of the body.
brain
Part of the central nervous system. It interprets and stores information and sends orders to muscles, glands, and organs.
spinal cord
Pathway connecting the brain and the peripheral nervous system.
reflex
a simple, automatic response to a sensory stimulus.
afferent (sensory) neurons
Neurons that carry incoming information from the body’s tissues and sensory receptors to the brain and spinal cord.
efferent (motor)
Neurons that carry outgoing information from the brain and spinal cord to muscles and glands.
neurons interneurons
neurons within the brain and spinal cord that communicate internally and process information from the sensory inputs and motor outputs.
somatic nervous system
The division of the peripheral nervous system that consists of the sensory neurons that are specialized to transmit messages from sensory receptors, and the motor neurons that send messages from the brain and spinal cord to the muscles that control our voluntary movements.
autonomic nervous system
The division of the peripheral nervous system that is responsible for the regulation of the body’s internal environment. This means that it controls the glands and the smooth (involuntary) muscles of the heart, blood vessels, stomach and intestines. In other words, the autonomic nervous system is largely concerned with involuntary functions such as respiration, circulation, and digestion.
sympathetic nervous system
The division of the autonomic nervous system that arouses the body, mobilizing its energy.
parasympathetic nervous system
The division of the autonomic nervous system that calms the body, conserving its energy.
homeostasis
An organism’s ability to regulate various physiological processes to keep internal states steady and balanced. These processes take place mostly without our conscious awareness.
endocrine system
The body’s “slow” chemical communication system that includes a set of glands that secrete hormones into the bloodstream.
hormones
chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.
glands
Glands are organs in the body that secrete chemicals. Some glands, like sweat glands and salivary glands, secrete chemicals onto the surface of the body through ducts. These are not endocrine glands. Endocrine glands secrete chemicals - hormones - directly into the bloodstream that carries them to their target organs.
pituitary gland
The endocrine system’s most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
growth hormone
Released by the pituitary gland, it controls and regulates the increase in size as children grow from infants to adulthood.
oxytocin
Released by the pituitary gland, it enables contractions during childbirth, influences milk flow during nursing (milk letdown reflex), promotes pair bonding, group cohesion, and social trust.
vasopressin
Released by the pituitary gland, it regulates the level of water in the body.
adrenal glands
A pair of endocrine glands that sit just above the kidneys and secrete a number of hormones.
adrenal medulla
Releases epinephrine and norepinephrine (also known as adrenaline and noradrenaline) when stress triggers the sympathetic nervous system.
adrenal cortex
Releases over 30 different hormones including many steroids. These hormones have many functions including controlling stress reactions (the hormone cortisol) and regulating salt intake. The adrenal cortex
also releases sex hormones in addition to those released by the gonads (testes and ovaries).
HPA Axis (hypothalamic - pituitary - adrenal axis)
A stressful event will trigger the hypothalamus to instruct the pituitary gland to release a hormone that triggers the adrenal glands to flood the body with cortisol - a stress hormone that causes the body to increase blood sugar. The high levels of cortisol will then trigger the hypothalamus to shut off the stress response. This is known as negative feedback.
pineal gland
Located in the brain, it is important in biological rhythms. It releases a hormone called melatonin which regulates the sleep-wake cycle. In other animals it influences seasonal behaviours such as breeding.
thyroid gland
Located in the neck, it secretes hormones that regulate growth and metabolism. One hormone, thyroxine, regulates metabolism which is how fast the body burns available energy.
parathyroid glands
Four small glands located behind the thyroid gland that produce a hormone called parathyroid hormone which controls calcium levels in the bloodstream.
pancreas
Regulates blood sugar level in the body by the release of insulin and glucagon. If the pancreas releases too little insulin, the result is diabetes. If it releases too much insulin, it results in hypoglycemia which is low blood sugar.
gonads - testes and ovaries
They secrete hormones that regulate sexual behaviour and reproduction. It is important to note that these hormones do not control all sexual behaviour.
brain
The brain is the organ located within the skull that is responsible for cognition, mental processes, and control of the body and its functions. It is the location of perception, ideas, thoughts, conscious movement, and unconscious body functions like heart rate and digestion.
lesion studies
Lesioning is the removal or destruction of part of the brain. In animals, that can mean deliberately damaging part of the brain and then studying its effect on an animal’s abilities. In this kind of experiment, an electrode is surgically inserted into a specific area of the brain. A current of electricity is passed through the electrode which heats the tip and destroys the intended brain tissue.
deep brain stimulation (DBS)
A specific type of ESB called deep brain stimulation (DBS) has been shown to be very helpful in various disorders. Neurosurgeons place electrodes in specific deep brain areas and connect these electrodes to a pacemaker-like device called an impulse generator that is implanted under the collarbone.
Noninvasive brain stimulation (NIBS)
This refers to a set of technologies and techniques to modulate the excitability of the brain via transcranial stimulation.
transcranial magnetic
stimulation (TMS)
A type of NIBS where magnetic pulses are applied to the outer portions of the brain and the resulting magnetic fields stimulate neurons in specific areas. If the pulses are applied in a repetitive fashion, it is referred to as repetitive TMS (rTMS).
transcranial direct current stimulation (tDCS)
A type of NIBS where scalp electrodes pass direct current to the brain to stimulate neurons directly below the electrodes.
electroencephalogram (EEG)
Electrodes placed on the scalp are used to measure electrical activity in neurons.
magnetoencephalography (MEG)
A head coil records magnetic fields from the brain’s natural electrical currents.
computed tomography (CT)
X-rays of the head generate images that may locate brain damage.
positron emission
tomography (PET)
A process that tracks where a temporarily radioactive form of glucose goes while the brain of the person given it performs a given task.
magnetic resonance imaging (MRI)
People sit or lie down in a chamber that uses magnetic fields and radio waves to provide a map of brain structure.
functional magnetic
resonance imaging (fMRI)
Measures blood flow to brain regions by comparing continuous MRI scans.
“old brain”
The structures at the brain’s core - the oldest part of the brain - govern our basic physiological functions, such as breathing, heart rate, resting, and feeding, that keep us alive. In primitive animals, such as sharks, only these brain structures exist.
“new brain”
On top of the brain core are newer systems that involve progressively more complex functions - sensing, emotions, wanting, thinking, and reasoning. These structures exist to a greater or lesser degree in all mammals.
forebrain
By far the largest region of your brain which contains the entire cerebrum and the limbic system.
midbrain
The midbrain is the topmost part of the brainstem, the connection central between the brain and the spinal cord.
hindbrain
Located at the lower back part of the brain, it includes most of the brainstem and the cerebellum.
brainstem
The brainstem is one of the most important parts of the entire central nervous system, because it connects the brain to the spinal cord and coordinates many vital functions, such as breathing and heartbeat. It includes the midbrain, the pons, and the medulla.
