CHAPTER 3 Flashcards
Define the nervous system
The interpreter of your experiences, the stimuli around you and the inner workings of your body. Creates behaviours. It can be subdivided into the central and peripheral nervous systems.
What makes up the central nervous system?
The brain and spinal cord
What is the function of the CNS
To process and relay information
What is the nervous system composed of?
Neurons and glial cells which can be arranged in different configurations to perform specific tasks.
Why do we differ as individuals?
Neural networks are varied and change based on an individual’s experiences.
What is the main nervous cell and what provides support?
Neurons are the main cell, while glial cells provide support
What are dendrites?
The branches of a neuron that receive messages through neurotransmitters binding to receptors in its membrane
What are neurotransmitters? Explain them and their connection to excitation and inhibition.
Neurotransmitters are chemical messengers that allow cells to communicate with each electrochemically. They trigger changes in the membrane potential, structure of neurons and their production of proteins as well as chemicals.
Excitation is the process of activating the neuron to send a message.
Inhibition is the process of preventing a neuron from sending a message/firing.
What happens to dendrites over the course of our lives?
Dendrites spread and branch, forming new connections with more neurons (the more connections, the better)
How do neurotransmitters function?
Neurons dispel their chemicals from the terminal buttons into the synaptic cleft, these neurotransmitters bind to the dendritic receptors and change the behaviour in the cell. This change will either be exciting the neuron to carry on a message or cease it
How does electricity come into play when considering action potentials and neuronal message transmission?
When neurotransmitters bind to the receptors of a neuron, it changes the action potential, either exciting it or inhibiting it. If exciting, the neuron will send an electrical pulse down its axon to release neurotransmitters in the synaptic cleft with another neuron, continuing transmission. If inhibiting, it will cease all such activity.
Where does the electricity in our bodies come from?
Ions, the opening and closing of sodium, potassium and chloride-gated channels along the membrane of an axon move an electrical charge to the end of a neuron
What is the initial charge of a neuron? What would you call this state of charge?
- 70mV, polarized
When would a cell be classified as depolarized?
When moving away from a charge of -70 (increasing), once it meets threshold, it will trigger the release of neurotransmitters into another neuron’s dendritic receptors
How do ions get into the cell?
Through various types of channels
What are the main 2 types of channels?
Chemically-gated channels only allow specific types of ionic chemicals through/require a specific type of neurotransmitter to be activated
Voltage-gated channels are only activated when threshold is met
What allows threshold to be reached?
When there are enough + charged ions present (usually Na+) outside the cell, voltage-gated sodium channels open attempting to balance charges. The sudden influx rapidly depolarizes the cell and fires it
Define propagation
The movement of an electric charge down an axon through the successive opening of sodium gated channels
What is repolarization?
When there is too much of a positive charge within the cell, voltage-gated K+ channels open, allowing for its efflux and resetting the membrane potential.
T/F: Neurons receive inhibitory OR excitatory neurotransmitters
False
Where are neurotransmitters released from?
Vesicles of a presynaptic neuron
How do inhibitory and excitatory neurotransmitters work?
Inhibitory: hyperpolarize the cell and change the membrane potential as a result
Excitatory: depolarize the cell and increase the likelihood of the neuron firing
What does GABA do and what channel does it bind with? What is its associated drug?
GABA binds with chloride channel receptors to inhibit an action potential. It makes the cell negative and more likely to remain inactive. It has to do with learning and anxiety regulation through inhibiting neurons. As a result, it has to do with valium for treating anxiety and flumazenil
What is the function of acetylcholine (Ach)? What is its associated drug?
It’s usually an excitatory neurotransmitter because it usually binds to Na+ channels, allowing for depolarization and making the cell more positive. Has to do with learning and muscle action, botox inhibits the release of Ach, thus preventing wrinkles and movement.
What influences the result of neurotransmitters? Think of behaviours, feelings, thoughts.
- Which receptor they bind with
- Where they’re released
- Timing
- Other neuronal activity
How do drugs work?
They either entirely block or act in place of a neurotransmitter, mimicking effects.
What is an agonist and what does it mimic> Include definitions.
Agonists are external substances that mimic the internal neurotransmitters of the body. They are sometimes more effective than endogenous (native to the body) neurotransmitters.
What are antagonists and what is their function?
They act as an inhibitor, preventing endogenous neurotransmitters (those that originate in the body from acting).
What are the two ways agonists and antagonists can act?
- Directly - targetting the neurotransmitter and sometimes even on the same receptor as said neurotransmitter
- Indirect - being non-competitive, they bind to different sites but still impact the receptor’s function from it
What are partial agonists/antagonists?
They are similar to agonists and antagonists, but they bind to and activate a receptor to a lesser extent than the endogenous neurotransmitter
What is the function of glutamate? What is its associated drug?
- excitatory
- learning and movement
- pcp for hallucinations
- ketamine as an anesthetic
What is the function of dopamine? What is its associated drug?
- Excitatory and inhibitory
- Learning, pleasure and rewards
- Cocaine as an antagonist, blocking receptors so dopamine cannot be re-uptaken and euphoric feelings last longer
What is the function of serotonin? What is its associated drug?
- excitatory and inhibitory
- elevation and depression of moods
- prozac as an antagonist, prevents the reuptake of serotonin and treats depression
What is the function of norepinephrine? What is its associated drug?
- excitatory and inhibitory
- elevation and depression of mood
- doxepin to treat anxiety and depression
What is the function of enkaphalins or endorphins? What is their associated drug?
- excitatory and inhibitory
- regulation pain responses
- opiates like morphine and heroin are used to prevent pain
What is a neural network?
A complex connection between denrites and axons of many neurons. There are billions of connections between the brains 80-90 million neurons.
Define a nerve
Bundle of neuronal axons
What is the difference between efferent and afferent nerves/axons?
Efferent: carry electrical impulses away from the CNS to trigger neurotransmitter and hormone release within a muscle or organ
Afferent: Carry impulses back to theCNS from organs and muscles
Define neuroplasticity
The brain and nervous system’s ability to change neurons and their networks/ the brain’s way of changing itself
What is the function of the neocortex? Where is it?
Concious thought and decision-making. The outer layer of the brain.
What is the function of the medulla?
Basic living functions
Where does most fight-or-flight symptom-triggering action originate?
In the lower brain centers ike the medulla/spinal cord
Identify what is part of the peripheral nervous system.
All nerves and ganglia that stem from the spinal cord into the limbs
Where does the PNS get its messaging?
From the spinal cord
What is the difference between white and grey matter?
White matter: myelinated axons. helps with communciation and allows for the fast transmission of information
Grey matter: neurons and ganglia (cell bodies). helps with processing
What are the subdivisions of the PNS?
Somatic and Autonomic
What identifies the Somatic Nervous system?
Function: it produces voluntary actions
Cell distinctions: has heavily myelinated axons
Neurotransmitter: ACh
Effects: Skeletal muscle and is stimulatory
What identifies the Autonomic Nervous system
Function: it produces automatic actions
Cell distinctions: has lightly myelinated preganglionic axons and unmyelinated postganglionic axons OR lightly myelinated directly to organs
Neurotransmitters: Ach preganglionic for sympathetic division and NE for post OR Ach in both for the parasympathetic division
Effects: organs and is either stimulatory or inhibitatory
What is the difference between the 2 divisions of the autonomic nervous system?
- Sympathetic: fight or flight
- Parasympathetic: rest and digest
Where do the neurons of the parasympathetic nervous system originate?
In the lower brain and sacral spinal cord
What division(s) does sex activate? Why?
Sex activates both because the excitement activates the sympathetic but the parasympathetic increases blood flow and directs it
What are the implications of stress on the nervous system?
Stress activates our autonomic nervous system, specifically the sympathetic because there is an element of fear in losing necessities that is often tied with stress (losing job = losing money = no food = death)
What is the reticular activating system (RAS) and where is it located?
A network of neurons in the center of the medulla and the pons, it bridges function of the body and brain through connections with the spinal cord and thalamus
What are the functions of the RAS?
Regulation of:
- arousal
- focus of attention on people, places, things and tasks
It will do things like tuning out irregular or unimportant stimuli
Define the limbic system
The limbic system includes circuits in the cortex and the midbrain. It’s function is to regulate our endocrine systems, emotions and emotional memory
What parts of the brain compose the limbic system?
The prefrontal cortex, the olfactory cortex, the amygdala, the hippocampus, the cingulate gyrus and the hypothalamus
What is the function of the amygdala?
located in the forebrain, it increases electrical activity when under threat. it controls our overall sense of fear and general aggression to threats or romantic love. helps form emotional memories and releases norepinephrine during fight or flight. receives all sensory input
What would happen in the case of malfunction of the amygdala?
if destructed:
- android like behaviour (no emotions)
- a lack of fear and phobias
if overactive:
- severe phobias and anxiety
Define the hippocampus and its functions
- in the forebrain
- helps form memories (catalogue them)
- circular in shape
Describe the cingulate gyrus and its functions
- in the forebrain
- set of neurons that helps us experience physical pain and pain from social exclusion/isolation
What is the hypothalamus and what does it do?
- in the back of the forebrain
- has functions in the endocrine and autonomic systems
- responsible for the regulation. of hunger, sexual behaviour, temperature and aggression
What is the function of the frontal lobes?
Function:
- Decision making
- Movement
- Control personality
Works with:
Other parts of the CNS and frontal lobes
- The frontal lobes tend to be inhibitory
Where in the frontal lobes is the motor cortex? What is it’s function?
At the back, towards the centre of the brain overall.
Function: helps produce voluntary movement
Difference between corticospinal and corticobulbar tracts?
Corticospinal: controls muscles in the body connected to the spinal cord
Corticobulbar: controls muscles in the head
What is a homunculus?
A visual representation of the amount of neurons adopted to control complex movement of each part of the body. Size represents quantity of neurons
What is the function and significance of the prefrontal cortex?
It acts as a series of on and off switches to support complex decision making and is connected with the negative symptoms of schizphrenia when malfunctioning
Distinctions of the dorsolateral PFC vs the ventromedial PFC?
Dorsolateral: helps maintain working memory and how we do things depending on what task we are trying to complete
Ventromedial: assists in behaviour modulation based on fear
Why are adolescents more impulsive?
The myelin in their prefrontal cortex is one of the last to get myelinated making messages in said area slower
What is the function of the temporal lobe?
Forming memories and processing auditory stimuli
What is anterograde amnesia?
The loss of the ability to form new memories due to damage in the temporal lobes
Where is the primary auditory cortex located?
In the temporal lobes
What happes when there is damage to the primary auditory cortex?
A person can lose all ability to perceive and decipher sounds, without any damage to the ear or cochlear nerve. Words and sounds can be heard but that information can not be used
How do we hear?
The circuits in the temporal lobes code information received through frequencies of action potentials originating in the axons of the cochlear nerve
Where is Wernicke’s area and why is it important?
The left temporal lobes, helps process language. Damage usually means that there is difficulty hearing or understanding speech
What sense area is housed in the temporal lobes other than hearing?
Olfactory and taste synapse sites. Olfactory doesn’t even go to the thalamic synapses, rather directly to the temporal.
What is EEG, how does it work and what are its limitations?
EEG is used to record changes in electrical potential during tasks. electrodes are placed in areas of the scalp that correspond with particular areas.
Limitation: doesn’t show deeper brain structures like basal ganlia
What is an fMRI, how does it work and what are its limitations?
fMRIs measure the oxygen level changes as related to blood flow. Used to access deeper brain structures. It isn’t a direct measurement of activity, but close.
What is a PET scan, what are its functions and limitations?
Indwelling electrodes are inserted into the brain during surgery to measure clusters of neurons. PET scans help figure out which neurotransmitters are being released through the injection of a radioactively tagged molecule that competes with the target neurotransmitter for the bonding site
How can we identify which neurons specifically are responsible for a specific task?
We individually turn off neurons (reversibly through drugs or irreversible by killing the neuron) and once the animal stops performing the behaviour, we know that neuron is responsible
When are CT scans used and what do they do?
Use xrays to pass through the body and generate sliced images of it
When are MRIs used and why?
They use magnetic fields to image alignments of hydrogen ions since different tissues have different waters
What are DTIs and when are they used?
Diffusion tensor imaging, used to create track and image the movement of water along a natural neural path and measures density of neural tracts. helps study white matter and degeneration diseases
