Neurons Week 5 Flashcards
Santiago Ramón y Cajal. Ramón y Cajal (1911) discovery
concluded that discrete individual neurons are the structural and functional units of the nervous system.
Camillo Golgi.
Golgi stained tissue
- characteristic of a Golgi stain is that it only stains approximately 1–2% of neurons permitting the observer to distinguish one cell from another.
Resting Membrane Potential
what occurs in a neuron at rest, when it is theoretically not receiving or sending signals.
number of neurons in human brain
100 billion neurons
3 components of neurons
dendrites,
the soma,
the axon
Define dendrites
Part of a neuron that extends away from the cell body and is the main input to the neuron.
Define soma
Cell body of a neuron that contains the nucleus and genetic information, and directs protein synthesis.
Define nucleus
Collection of nerve cells found in the brain which typically serve a specific function.
Define axon
main output of the neuron.
Part of the neuron that extends off the soma, splitting several times to connect with other neurons
Define synapse
Junction between the presynaptic terminal button of one neuron and the dendrite, axon, or soma of another postsynaptic neuron.
What is the terminal button?
The part of the end of the axon that form synapses with postsynaptic dendrite, axon, or soma.
What are spines?
Protrusions on the dendrite of a neuron that form synapses with terminal buttons of the presynaptic axon.
what is synaptic gap?
Also known as the synaptic cleft; the small space between the presynaptic terminal button and the postsynaptic dendritic spine, axon, or soma.
5 nanometers
What are synaptic vesicles
Groups of neurotransmitters packaged together and located within the terminal button.
What are neurotransmietters
Chemical substance released by the presynaptic terminal button that acts on the postsynaptic cell.
Not all neurons are equal,
what are three main categories of neurons:
- Unipolar - ideal for relaying information forward, so they have one neurite (axon) and no dendrites.
- Bipolar - involved in sensory perception, have one axon and one dendrite which help acquire and pass sensory information to various centers in the brain.
- multipolar - communicate sensory and motor information in the brain. one axon and many dendrites which allows them to communicate with other neurons.
glia cell - oligodendroglia
forms the myelin sheaths
GLIA DO NOT PARTICIPATE IN COMMUNICATION BETWEEN CELLS
glia cells, such as microglia and astrocytes
digest debris of dead neurons, carry nutritional support from blood vessels to the neurons, and help to regulate the ionic composition of the extracellular fluid.
GLIA DO NOT PARTICIPATE IN COMMUNICATION BETWEEN CELLS
two stages of electrochemical action in neurons.
- electrical conduction of dendritic input to the initiation of an action potential within a neuron.
- chemical transmission across the synaptic gap between the presynaptic neuron and the postsynaptic neuron of the synapse.
Cations
Positively charged ions
anions
negatively charged ions
composition of intracellular and extracellular fluid (4)
sodium (Na+)
potassium (K+)
chloride (Cl–)
anions (A–)
Define cell membrane
A bi-lipid layer of molecules that separates the cell from the surrounding extracellular fluid.
What are ion channels
Proteins that span the cell membrane, forming channels that specific ions can flow through between the intracellular and extracellular space.
What is diffusion?
The force on molecules to move from areas of high concentration to areas of low concentration.
What is electrostatic pressure?
The force on two ions with similar charge to repel each other; the force of two ions with opposite charge to attract to one another.
equilibrium potential
voltage at which no ions flow
resting membrane potential
The voltage inside the cell relative to the voltage outside the cell while the cell is a rest (approximately -70 mV).
Anions (A-):
Anions are highly concentrated inside the cell and contribute to the negative charge of the resting membrane potential. Diffusion and electrostatic pressure are not forces that determine A– concentration because A– is impermeable to the cell membrane. There are no ion channels that allow for A– to move between the intracellular and extracellular fluid.
Potassium (K+):
The cell membrane is very permeable to potassium at rest, but potassium remains in high concentrations inside the cell. Diffusion pushes K+ outside the cell because it is in high concentration inside the cell. However, electrostatic pressure pushes K+ inside the cell because the positive charge of K+ is attracted to the negative charge inside the cell. In combination, these forces oppose one another with respect to K+.
Chloride (Cl-):
The cell membrane is also very permeable to chloride at rest, but chloride remains in high concentration outside the cell. Diffusion pushes Cl– inside the cell because it is in high concentration outside the cell. However, electrostatic pressure pushes Cl– outside the cell because the negative charge of Cl– is attracted to the positive charge outside the cell. Similar to K+, these forces oppose one another with respect to Cl–.
Sodium (Na+):
The cell membrane is not very permeable to sodium at rest. Diffusion pushes Na+ inside the cell because it is in high concentration outside the cell. Electrostatic pressure also pushes Na+ inside the cell because the positive charge of Na+ is attracted to the negative charge inside the cell. Both of these forces push Na+ inside the cell; however, Na+ cannot permeate the cell membrane and remains in high concentration outside the cell. The small amounts of Na+ inside the cell are removed by a sodium-potassium pump, which uses the neuron’s energy (adenosine triphosphate, ATP) to pump 3 Na+ ions out of the cell in exchange for bringing 2 K+ ions inside the cell.
Sodium potassium pump
An ion channel that uses the neuron’s energy (adenosine triphosphate, ATP) to pump three Na+ ions outside the cell in exchange for bringing two K+ ions inside the cell.
Hodgkin and Huxley action potential
A transient all-or-nothing electrical current that is conducted down the axon when the membrane potential reaches the threshold of excitation. -70 mV
threshold of excitation
Specific membrane potential that the neuron must reach to initiate an action potential. around -50 mV.
types of fluctuations in the neuron’s membrane potentials (2)
- excitatory postsynaptic potentials
- inhibitory postsynaptic potentials
excitatory postsynaptic potentials
A depolarizing postsynaptic current that causes the membrane potential to become more positive and move towards the threshold of excitation.
inhibitory postsynaptic potentials
A hyperpolarizing postsynaptic current that causes the membrane potential to become more negative and move away from the threshold of excitation.
What are ionic recpetors
Ion channel that opens to allow ions to permeate the cell membrane under specific conditions, such as the presence of a neurotransmitter or a specific membrane potential.
What part of the neuron carries the action potential and is the main source of output?
axon
What insulating substance allows for an electrical signal to travel much faster down an axon?
myelin sheath
What type of neuron receives environmental stimuli and helps people perceive?
sensory neuron
Communication within a neuron is electrical, and between neurons is ______.
chemical
The electrostatic charge within a neuron must reach the ______before the neuron will fire.
threshold of excitation
What current causes depolarization, increasing the likelihood that the neuron will fire?
excitatory postsynaptic potential
Differentiate the functional roles between the two main cell classes in the brain, neurons and glia.
Describe how the forces of diffusion and electrostatic pressure work collectively to facilitate electrochemical communication.
Define resting membrane potential, excitatory postsynaptic potentials, inhibitory postsynaptic potentials, and action potentials.
Explain features of axonal and synaptic communication in neurons.
Define hormones
An organic chemical messenger released from endocrine cells that travels through the blood to interact with target cells at some distance to cause a biological response.
what is the endocrine glands
A ductless gland from which hormones are released into the blood system in response to specific biological signals.
neurotransmitters
Chemical substance released by the presynaptic terminal button that acts on the postsynaptic cell.
testosterone
The primary androgen secreted by the testes of most vertebrate animals, including men.
progestin
A class of C21 steroid hormones named for their progestational (pregnancy-supporting) effects. Progesterone is a common progestin.
oxytocin
A peptide hormone secreted by the pituitary gland to trigger lactation, as well as social bonding.
prolactin
A protein hormone that is highly conserved throughout the animal kingdom. It has many biological functions associated with reproduction and synergistic actions with steroid hormones.
cortisol (steroid hormone)
increase carb metabolism; stress response
estradiol (steroid hormone)
uterine and other female tissue development; sexual motivation and performance
testosterone (steroid hormone)
sperm production, secondary male charactersitics, promotes sexual motivation and performance usually converted to estradiol
oxytocin (peptides & protein hormones)
stimulates milk letdown & uterine contractions during birth; promotes social bonding
prolactin (peptides & protein hormones)
actions relating to reproction, water balance, parental care behaviour
thyroxine (peptides & protein hormones)
increases oxidation rates in tissue and affects on neural development
vasopressin (peptides & protein hormones)
increases water reabsorption in the kidney and effects learning and memory
target cells
A cell that has receptors for a specific chemical messenger (hormone or neurotransmitter).
three interacting components of hormones effect baheviour
(1) input systems (sensory systems)
(2) integrators (the central nervous system)
(3) output systems, or effectors (e.g., muscles).
sexual differentiation
The process by which individuals develop the characteristics associated with being male or female. Differential exposure to gonadal steroids during early development causes sexual differentiation of several structures including the brain.
sex determinatiton
The point at which an individual begins to develop as either a male or a female. In animals that have sex chromosomes, this occurs at fertilization. Females are XX and males are XY. All eggs bear X chromosomes, whereas sperm can either bear X or Y chromosomes. Thus, it is the males that determine the sex of the offspring.
chromosomal sex
The sex of an individual as determined by the sex chromosomes (typically XX or XY) received at the time of fertilization.
gonadal sex
The sex of an individual as determined by the possession of either ovaries or testes. Females have ovaries, whereas males have testes.
5α-reductase
An enzyme required to convert testosterone to 5α-dihydrotestosterone.
aromatase
An enzyme that converts androgens into estrogens.
aggressive behaviour
A form of social interaction that includes threat, attack, and fighting.
parental behaviour
Behaviors performed in relation to one’s offspring that contributes directly to the survival of those offspring
paternal behaviour
Parental behavior performed by the father or other male.
progesterone
A primary progestin that is involved in pregnancy and mating behaviors.
Alison Fleming
maternal study
Responses such as patting, cuddling, or kissing the baby were called affectionate behaviors; talking, singing, or cooing to the baby
Why does the analogy of a car (for hormonal transmission) and a train (for neural transmission) help explain their differences?
Hormones can go many places, whereas neurons have to follow a specific path.
What is the study of how the nervous system and the endocrine system are interrelated called?
Neuroendocrinology
When hormones activate a target cell, proteins ______ other genes.
activate or deactivate
If human behavior can be conceptualized as three systems- input, integrator, and output- then which do hormones influence?
all three sytems
When looking at cognitive differences between the sexes, which of the following would be the best conclusion?
While there are differences, the differences are slight.
Define the basic terminology and basic principles of hormone–behavior interactions.
Explain the role of hormones in behavioral sex differentiation.
Explain the role of hormones in aggressive behavior.
Explain the role of hormones in parental behavior.
Provide examples of some common hormone–behavior interactions.
psychoactive drugs
A drug that changes mood or the way someone feels.
Psychoactive drugs can either increase activity at the synapse (these are called agonists) or reduce activity at the synapse (antagonists).
agonist
A drug that increases or enhances a neurotransmitter’s effect.
antagonist
A drug that blocks a neurotransmitter’s effect.
Neurotransmitter: acetylene ACh
learning and memory; Alzheimers; muscle movement in peripheral nervous system
Neurotransmitter: Dopamine DA
Reward circuits; motor circuits (Parkinson’s); Schitzphrenia
Neurotransmitter: Norepinephrine NE
Arousal; depression
Neurotransmitter: Serotonin 5HT
Depression; aggression, Schitzphrenia
Neurotransmitter: Glutamate GLU
learning; major excitatory neurotransmitter in brain
Neurotransmitter: GABA
Anxiety disorders; epilepsy, major inhibitory neurotransmitter in the brain
Neurotransmitter: Endogenous opioids (endorphins & enkaphilins)
pain, analgesia, reward
psychotropic drug
A drug that changes mood or emotion, usually used when talking about drugs prescribed for various mental conditions (depression, anxiety, schizophrenia, etc.).
pharmacokinetics
The action of a drug through the body, including absorption, distribution, metabolism, and excretion.
how the body handles a drug that we take.
metabolism
Breakdown of substances.
enzymes
A protein produced by a living organism that allows or helps a chemical reaction to occur.
enzyme induction
Process through which a drug can enhance the production of an enzyme.
Grapefruit juice danger with drugs?
Grapefruit juice suppresses cytochrome P450 enzymes in the liver, and these liver enzymes normally break down a large variety of drugs
4 types of metabolizers
1) ultra-extensive metabolizers break down certain drugs (like some of the current antidepressants) very, very quickly
2) extensive metabolizers are also able to break down drugs fairly quickly
3) intermediate metabolizers break down drugs more slowly than either of the two above groups
4) poor metabolizers break down drugs much more slowly than all of the other groups
How do the majority of psychoactive drugs work in the brain?
How does the route of administration affect how rewarding a drug might be?
Why is grapefruit dangerous to consume with many psychotropic medications?
Why might individualized drug doses based on genetic screening be helpful for treating conditions like depression?
Why is there controversy regarding pharmacotherapy for children, adolescents, and the elderly?
______refers to the use of multiple drugs , which is a particularly problematic issue for the elderly population of the United States.
polypharmacy
The most common route by which a drug is ingested into the body is oral administration, while one of the most rapid ways of getting the effects of a drug is ______.
inhalation
soma
Cell body of a neuron that contains the nucleus and genetic information, and directs protein synthesis.
nucleus
Contains genetic information, directs protein synthesis, and supplies the energy and the resources the neuron needs to function
dendrites
Part of a neuron that extends away from the cell body and is the main input to the neuron
spines
Protrusions on the dendrite of a neuron that form synapses with terminal buttons of the presynaptic
axon.
axon
Part of the neuron that extends off the soma, splitting several times to connect with other neurons; main output of the neuron.
action potential
A transient all-or-nothing electrical current that is conducted down the axon when the membrane potential reaches the threshold of excitation.
synapse
Junction between the presynaptic terminal button of one neuron and the dendrite, axon, or soma of another postsynaptic neuron.
myeline sheeth
Substance around the axon of a neuron that serves as insulation to allow the action potential to conduct rapidly toward the terminal buttons.
nodes of ranvier
Gaps in the myelin sheath
cell membrane separates:
extracellular and intracellular fluid
Ion channel
Proteins that span the cell membrane, forming channels that specific ions can flow through between the intracellular and extracellular space.
Anions
Negatively charged ions in high concentration within cells.
Electrostatic pressure
The force on two ions with similar
charge to repel each other; the
force of two ions with opposite
charge to attract to one another.
diffusion
The force on molecules to move from areas of high concentration to areas of low concentration.
Potassium k+
In high concentration inside cells. Cell
membrane highly permeable to K+
Chloride Cl-
In high concentration outside cells. Cell membrane highly permeable to Cl-
Sodium Na+
In high concentration outside cells
Sodium-potassium pump
An ion channel that uses the
neuron’s energy (adenosine triphosphate, ATP) to pump three
Na+ ions outside the cell in exchange for bringing two K+ ions inside the cell.
+ 3 Na+ Sodium
- 2 k+ potassium
Action potential
A transient all-or-nothing electrical current that is conducted down the axon when the membrane potential reaches the threshold of excitation.
-70 mV (Inside relative to outside)
Excitatory post-synaptic potential
(EPSPs): a depolarizing current that causes the membrane potential to become more positive
and closer to the threshold of excitation
Inhibitory post-synaptic potential
(IPSPs): a hyperpolarizing current that causes the membrane potential to become more negative and further from the threshold of excitation
What happens when threshold met?
Voltage-dependent sodium (Na+) channels are opened
ACTION POTENTIAL TRIGGERED
Na+ rushes in, making the cell highly depolarized/positive
TOWARD MEMBRANE POTENTIAL
K+ channels open
K+ rushes out
REFRACTORY PERIOD
NA+ channels close, K+
gradually close
RETURN TO MEMBRANE POTENTIAL
The terminal button
The part of the end of the axon that form synapses with postsynaptic dendrite, axon, or soma.
Synaptic gap / synaptic cleft
the small space between the presynaptic terminal button and the postsynaptic dendritic spine, axon, or soma.
vesciles
Groups of neurotransmitters packaged together and located within the terminal button.
neurotransmitters
Chemical substances released by the presynaptic terminal button that acts on the postsynaptic cell.
