Week 5 Flashcards
What is a neuron?
Neurons are the basic cellular units of the nervous system and are basically electrochemical information storage and transmission devices.
What are the types of neurons?
Unipolar, bipolar and multipolar
Unipolar- Relay information forward; 1 axon and no dendrites
Bipolar- Sensory perceptions; 1 axon and 1 dendrite
Multipolar-
Communicate with other neurons; 1 axon and many dendrites
What is the function of the glial cells?
Glial cells help with the ‘menial’ tasks of cleaning up waste products, providing nutrients and physical support, and guiding developing neurons to their proper places.
What are the parts of neurons?
Dendrites (receive information), cell body or soma (process information and contains the nucleus) and the axon/terminal button (sends information)
Describe the process of dendrites
Dendrites maximize branching out to receive input: chemical signals enter the dendrites spines, then travel down to the cell body where they are averaged to one of two simple conclusions- fire an action potential or don’t fire an action potential.
What happens when the signal of dendrites is fire?
If the signal is fired, then that signal runs down the axon- all or nothing signal.
Dendrites
receivers
Axon terminals
transmitters
Schwann’s cells
type of glial cell (they make the myelin)
Axon
The conducting fiber
Myelin sheath
insulating fatty layer that speeds transmission
Sensory neuron
activated by information inputted from the environment
Motor neuron
transmit impulses from the spinal cord to the skeletal and smooth muscles
Interneuron
allows for sensory neurons and motor neurons to communicate with the CNS (central nervous system)
Neurotransmitter
is triggered at the end of the axon that travels across the synapses.
What are the principles that help drive the action potential?
Electrical gradient (difference in charge) and a concentration gradient (difference in concentration)
Anions
negatively charged ions
Cations
positively charged ions
Electrostatic pressure
The repelling force of 2 ions or attractive force
Diffusion
movement of molecules from high concentration to low concentration
What are the 3 important molecules?
Sodium, chlorine and potassium
What drives the action potential?
1.At rest, there is a greater concentration of Na outside the neuron and a greater concentration of K inside the neuron; however, there is relatively more Na out than K in.
- This leads to a difference in concentration and in electrical potential across the impermeable membrane; this leads to a difference called the resting potential.
3.Na gates are voltage-sensitive, that is they require a sufficient resting voltage to be opened. If and only if, a sufficient increase in voltage is inputted from the dendrites, depolarization will occur: Na channels open and Na rushes into the neuron, making the neuron much more positive (depolarization phase).
4.Slightly later, K gates open and allow K to leave the neuron.
5.At the peak of the action potential, the flow of Na in is equal to the flow of K out.
6.The flow of Na slows down, while K out continues, repolarizing and making the neuron less positive- meaning it is hyperpolarized, refractory period and nerve cannot fire again right away.
7.A Na/K pump then removes Na and imports K to restore the resting potential. This pump uses ATP (molecular energy), and in total accounts for about 20% of human metabolism.
What drives the action potential plainly said:
1.At rest, Potassium (+) is happy, but sodium (-) wants in. The balance of positives means that the inside is negative to the outside.
2.If an outside event causes that inside to be more positive, then, and only then, will sodium gates open and let sodium rush in.
3.Sodium rushing in means lots of positives in, which means the inside becomes positive= depolarization.
4.This in turn drives out the potassium as positives repel each other, making the cell negative again= repolarization (hyperpolarized)
5.The system is then reset by the Sodium-Potassium pump.
What is synaptic cleft?
The sending cell does not directly connect with the receiving cell- the gap between the two cells.
What is the presynaptic neuron?
The cell releasing information (before the gap between the two cells)
What is the postsynaptic neuron?
The cell receiving the information (after the gap between the two cells)
What is the gap known as?
The gap describes is called the synapse
What are vesicles?
Vesicles contain neurotransmitters, which are chemical messengers
How does the process of sending signals work?
When the signal arrives in the presynaptic axon terminal, the action potential causes vesicles to be free. After this the vesicles fuse with the membrane of the presynaptic cell and release the neurotransmitter into the synaptic cleft. The neurotransmitter then diffuses across the cleft over to the postsynaptic neuron’s membrane. However, membranes are impermeable to the external environment, so it finds neurotransmitter receptors (lock and key method). The cycle starts again and keeps going from neuron to neuron.
During this process what makes an action potential more likely?
Gates that allow sodium to enter depolarize the postsynaptic neuron (an excitatory input)
During this process what makes an action potential less likely?
Chlorine or potassium repolarize or hyperpolarize the postsynaptic neuron (an inhibitory input)
When does reuptake happen and what is it?
Once the neurotransmitter has docked with the postsynaptic cell for some time, it is released back into the synapse, where it is taken back into/ recycled by the presynaptic cell. In simple terms, it is when the neurotransmitter is absorbed back into the neuron that released them.
Why are potassium and sodium both positively charged but have different effects?
This is because sodium has a greater concentration outside the neuron compared to inside meaning there is an influx of positive charge that depolarizes the neuron, whereas potassium ions have a higher concentration inside the neuron compared to outside meaning there is an efflux of positive charge ions that hyperpolarizes the cell
Hyperpolarize
makes the cell more negative
Depolarize
makes the cell more positive
How do drugs work on the brain?
Stimulating the release of more neurotransmitter (or mimicking the effects of a neurotransmitter)
Inhibiting the release of more neurotransmitter (or by blocking the post-synaptic gates)
Blocking the reuptake process, thereby prolonging the action of the body’s natural neurotransmitters (I.e. antidepressants)
What are agonists?
Drugs that can enhance the action of a neurotransmitter- turns on the receptor.
What are antagonists?
Drugs that hinder the activity of a neurotransmitter- blocks the receptor.
What is the purpose of psychotropic/ psychoactive drugs?
Psychotropic/ psychoactive drugs can alter perception, mood, consciousness, cognition or behavior.
What is Pharmacokinetics?
Pharmacokinetics is a branch of pharmacology that describes how the body absorbs and metabolizes substances.
What does being a poor metabolizer entail?
Break down the drug slowly- leads to side effects.
What does being an ultrarapid metabolizer entail?
Break down rapidly- leads to lack of symptom relief
What is glutamate?
Glutamate is the major excitatory neurotransmitter in the brain and is often targeted by drugs that seek to reduce brain activity.
What is the antonym of glutamate?
The opposite of glutamate in the brain is GABA, which is the major inhibitory neurotransmitter in the brain.
What is acetylcholine?
Acetylcholine is the primary neurotransmitter used to activate motor neurons.
Dopamine’s function:
Dopamine is involved with excitement, movement, attention and learning.
Norepinephrine’s function:
Norepinephrine is involved with attention, vigilance and sleep.
Serotonin’s function:
Serotonin regulates mood, sleep, pain, sensory perception, and down regulates risk taking (unlike dopamine which increases it).
How many of these neurotransmitters (dopamine, norepinephrine and serotonin) function at the same time?
Usually, all neurotransmitters operate at the same time, allowing for our highly flexible brains to function at such a high level.
What is the endocrine system?
Hormones released by glands into the blood that target distant organs.
What hormones are involved in the endocrine system and what are they involved in?
Steroid hormones: testosterone, estradiol, progesterone, cortisol
Peptide hormones: oxytocin, vasopressin, prolactin, leptin
How does the endocrine system work?
Hormones are more slowly acting, they travel through the blood
