W3 notes

Question 1

Synesthesia

Answer 1

Synesthesia is a condition where individuals experience a mingling of the senses

E.g. grapheme-colour synesthesia is when the perception of numerals and letters is associated with the experience of colours

Question 2

patient george case

Answer 2

A man known as patient George is one of 2 people known to have acquired synesthesia after suffering damage to the thalamus (stroke in the left thalamus)
He reported experiencing an intense sensory-emotional experience as a result of hearing the brass theme from James Bond
Hearing the music led to greater neural activation in widespread areas of the brain including the auditory cortex, somatosensory cortex, motor cortex, thalamus, hippocampus, and particular regions of the insula, cerebellum, and prefrontal cortex

Question 3

neurons

Answer 3

Neurons→nerve cells which are the building blocks of the nervous system

Question 4

glia

Answer 4

the supporting cells in neurons

Question 5

neural communication process

Answer 5

First step takes place within a single neuron and involves the generation of an electric signal

Second step takes place between 2 neurons and involves the release of a chemical messenger from 1 neuron that affects the activity of the second
-This is why the nervous system is often referred to as the body’s electrochemical communication system

Question 6

cell body

Answer 6

Like other cells, a neuron has a large central mass or cell body, and within the cell body, it has a nucleus

Question 7

structure of neuron outer membrane

Answer 7

Like other cells, neurons feature an outer membrane, which surrounds the neuron and forms a barrier between the fluid outside the cell (extracellular fluid) and the fluid inside the cell (intracellular fluid)

Question 8

neural membrane

Answer 8

Neural membrane is composed of fatty materials that do not dissolve in water, so even though it is only 2 molecules thick, it’s able to hold apart the water-based fluids on either side
Pores within the membrane act as channels that allow chemicals to move into or out of the cell

Question 9

axons vs dendrites

Answer 9

Neurons have 2 types of branches that extend from the cell body to allow the neuron to perform its information-processing and communication functions

The branches known as axons are responsible for carrying info to other neurons, while the branches known as dendrites receive input from other neurons
Each neuron has only one axon

Question 10

terminal

Answer 10

At its farthest point from the cell body, an axon bulges to form a terminal

Inside an axon terminal, you can see hollow spheres known as synaptic vesicles, which contain molecules of chemical messengers

Question 11

glia

Answer 11

Glia make it possible for neurons to do their job effectively and provide a structural matrix for neurons, ensuring that the neurons stay in place

Other glia are mobile, allowing them to move to a location where neurons have been damaged to clean up debris

Glia form tight connections with the blood vessels serving the nervous system
-This forms a blood-brain barrier that prevents many toxins circulating in the blood from exiting into brain tissue where neurons could be harmed

Question 12

psychoactive drugs

Answer 12

Psychoactive drugs, are substances capable of penetrating the blood-brain barrier with ease

Question 13

blood brain barrier

Answer 13

Gilia form tight connections with the blood vessels in the nervous system, preventing many toxins from entering the brain
Glia also help hold neurons in place and form the myelin on some axons
Sometimes offers too much protection to the brain and chemotherapy agents can’t get past it to treat tumours

Question 14

myelin

Answer 14

In vertebrates, glia wrap around some axons, forming an important layer of insulation called myelin
Myelin makes neural signalling fast and energy efficient
By speeding up the transmission of neural signals and contributing to quicker recovery between signals, myelin increases the amount of info a neuron can transmit per second by a factor of 3000

Question 15

function of different types of glia

Answer 15

One type of glia forms the myelin in the brain and the spinal cord, and a 2nd type forms the myelin in the remainder of the nervous system
-They behave differently from each other when damaged
–Glia in the brain and the spinal cord form scar tissue, inhibiting repair to the damaged nerves
—Because of this feature, we consider damage in the CNS to be permanent

Damaged glia in the PNS do not form scar tissue and instead help the damaged axons regrow
-As a result, nerve damage in these areas can heal

Question 16

The last area of the nervous system to be myelinated is the…

Answer 16

prefrontal cortex, which is involved with judgement and morality
Until myelin in this area is mature, these neurons don’t work efficiently, which’s why adults and teens make different decisions

Question 17

neuron

Answer 17

A neuron is a sophisticated communication and information-processing system that receives input, evaluates it, and decides whether to transmit info to neurons downstream

Question 18

1st step of neuron communication

Answer 18

In the 1st step of neuron communication, it takes place in the signalling neuron’s axon, the neuron generates an electrical signal known as action potential
This signal travels the length of the axon from its junction with the cell body to its terminal

Question 19

2nd step in neural signalling

Answer 19

In the 2nd step, which takes places between 2 neurons, the arrival of an action potential at the axon terminal of the first neuron signals at the release of chemical messengers, which float across the extracellular fluid separating the 2 neurons

These chemicals influence the likelihood that the second neuron will respond with its own action potential, sending the message along

Question 20

electrical signaling

Answer 20

When a neuron is not processing information we say that it’s at rest
When a cell is at rest, the difference between the readings from the interior of the axon and the external fluid is known as the resting potential

Question 21

Neurons can respond to incoming chemical signals by becoming either …

Answer 21

depolarized or hyperpolarized
\
The word polarized means “far apart” and being depolarized means we have moved closer together, being hyperpolarized means we have moved farther apart than before

Question 22

depolarization

Answer 22

In the case of neurons, depolarization means that the difference between the electrical charges of the extracellular and the intracellular recordings is decreasing

Question 23

hyperpolarization

Answer 23

Hyperpolarization means that the difference is increasing

Question 24

what happens when a neuron is depolarized?

Answer 24

When a neuron is depolarized by sufficient input, it reaches a threshold for producing an action potential

Question 25

threshold

Answer 25

A threshold is the point at which an effect (the action potential), is initiated Once this threshold is reached, the generation of an action potential is inevitable This involves the opening and the closing of pores or channels in the neural membrane, which in turn allow certain chemicals to move into and out of the cell These chemicals are in the form of ions or electrically charged particles dissolved in water

Question 26

when the threshold is reached and channels open, what happens?

Answer 26

When threshold is reached, channels open, allowing only one type of ion, sodium, to rush into neuron (bc of positive electrical charge) Near the peak of the action potential, channels open that allow another type of ion, (positively charged) potassium, to move across the membrane

Question 27

resting state

Answer 27

after the production of the action potential, the neuron requires a time-out or refractory period, during which it returns to its resting state During this period, the cell is unable or unlikely to respond to further input by producing another action potential

Question 28

action potentials

Answer 28

Action potentials do NOT affect the entire axon all at once The process just described takes place first in a small segment of the axon where the axon connects to the cell body

Question 29

propagation

Answer 29

The next step is propagation, or the duplication of the electrical signal down the length of the axon to the axon terminal, where it initiates the release of chemical messengers Propagation takes place differently in myelinated and unmyelinated axons

Question 30

action potential in an unmyelinated axon

Answer 30

In an unmyelinated axon, action potentials occur step by step, from one small section of the axon to the next adjacent section, down the entire length of the axon

Question 31

action potential in a myelinated axon

Answer 31

In contrast, action potentials in myelinated axons are formed only at the sections of the axon membrane between adjacent segments of myelin, known as nodes of Ranvier

Question 32

propagation in myelinated axons can “_____” the sections covered by myelin

Answer 32

skip

Question 33

Propagation in myelinated axons

Answer 33

After an initial action potential is generated near the cell body, the current flows beneath a segment of myelin until it reaches a node of Ranvier, where another action potential occurs By covering the same distance with fewer action potentials, the myelinated axon uses less energy returning to the resting potential than an unmyelinated axon would need -Once the action potential reaches the axon terminal, the neural communication system switches from an electrical signaling system to a chemical signaling one

Question 34

synapse

Answer 34

The point of communication between 2 neurons is known as a synapse At the synapse, neurons do not touch one another physically They are separated by tiny gaps filled with extracellular fluid

Question 35

neurotransmitters

Answer 35

Because electrical signals are unable to jump this gap, neurons send chemical messengers instead These chemical messengers are called neurotransmitters After interacting with receptors, neurotransmitter molecules are often recaptured by the neuron that released them to be recycled and used again later

Question 36

receptors

Answer 36

The neurotransmitters released across the synaptic gap come into contact with special channels on the receiving neuron, known as receptors Receptors work with the neurotransmitters like locks and keys Only a neurotransmitter with the right shape (the key) can attach itself or bind to a particular receptor (the lock)

Question 37

reuptake

Answer 37

Once neurotransmitters pop out of the receptor binding site, they drift away from the gap, are broken down by enzymes or return to the axon terminal from which they were released in a process called reuptake Reuptake is when special channels in the axon terminal membrane known as transporters allow the neurotransmitters to move back into the releasing neuron where they are repackaged for later use

Question 38

The interaction between neurotransmitters and their receptors can have one of 2 effects on the receiving neuron:

Answer 38

excitation or inhibition

Question 39

When a neurotransmitter has an excitatory effect...

Answer 39

it slightly depolarizes the receiving neuron, increasing the likelihood that the neuron will reach threshold and initiate an action potential Recall that depolarization reduces the difference between the electrical environments inside and outside the neuron.

Question 40

When a neurotransmitter has an inhibitory effect...

Answer 40

it slightly hyperpolarizes the receiving neuron, moving the cell farther from threshold and reducing the likelihood that it will initiate an action potential Recall that hyperpolarization increases the difference between the electrical environments inside and outside the neuron

Question 41

agonists

Answer 41

Agonists are drugs that enhance the actions of neurotransmitters An agonist might enhance the actions of a particular neurotransmitter by increasing its release, blocking its reuptake, or by mimicking the neurotransmitter and activating its postsynaptic receptor For example, cocaine prevents the dopamine transporter protein from being able to perform its normal reuptake function, resulting in an accumulation of dopamine in the synaptic cleft Increased activation of postsynaptic dopamine receptors leads to the reinforcing effects of cocaine

Question 42

antagonists

Answer 42

drugs that inhibit the actions of neurotransmitters An antagonist might inhibit the actions of a particular neurotransmitter by blocking its release, destroying the neurotransmitter in the synapse, or by mimicking the neurotransmitter and binding to a postsynaptic receptor in a way that prevents neurotransmitter binding For example, beta blockers, a class of drugs commonly prescribed to individuals who have suffered a heart attack, are antagonists that block certain receptor sites for epinephrine and norepinephrine, weakening the effects of the sympathetic stress response

Question 43

where do synapses occur

Answer 43

Synapses usually occur in many locations on the dendrites or cell body of the receiving neuron, and the depolarizing or hyperpolarizing current that results from neurotransmitter activity at these synapses drifts to the junction of the cell body and axon

Question 44

how do you know when a neuron will generate an action potential

Answer 44

If there is sufficient depolarization to reach threshold at this junction, the neuron generates an action potential If not, it remains at rest

Question 45

summation

Answer 45

The neuron’s “decision” to generate an action potential or not is called summation; the neuron is adding up all incoming messages and making a decision based on that information

Question 46

Acetylcholine

Answer 46

Acetylcholine (ACh) is a neurotransmitter found in many systems important to behaviour ACh is found at the neuromuscular junction, the synapse at which the nervous system commands muscles Interference with the action of ACh at the muscles can result in paralysis and death, making drugs that act on ACh popular for use as pesticides and as bioweapons ACh also serves as a key neurotransmitter in the autonomic nervous system, which carries commands from the brain to the glands and organs ACh is also intimately involved in the brain circuits related to learning and memory

Question 47

dopamine

Answer 47

Dopamine is involved with systems that govern movement, planning, and reward Parkinson’s disease, which makes normal movement difficult, results when dopamine-releasing neurons in the brain’s movement circuits begin to die In addition, dopamine participates in the brain’s reward and pleasure circuits by becoming active whenever we engage in behaviours that promote survival and successful reproduction, such as eating a great meal or having sex Most drugs that produce addiction, including cocaine and methamphetamine, stimulate increased activity in dopamine circuits

Question 48

serotonin

Answer 48

Serotonin is involved with systems regulating sleep, appetite, mood, and aggression Consequently, these behaviours are tightly linked

Question 49

endorphins

Answer 49

Endorphins, short for endogenous morphine or morphine produced by the body, modify our natural response to pain In evolutionary terms, it makes sense to have a system that reduces your chances of being disabled by pain during an emergency All too frequently, however, we underestimate the extent of our injuries until we wake up the next morning feeling sore “Runner’s high,” in which people who regularly engage in endurance sports experience a sense of well-being and reduced sensation of pain, results from the release of endorphins initiated by high levels of activity Opioid drugs such as morphine, heroin, and oxycodone (OxyContin) produce their pain-relieving effects by mimicking the action of endorphins at the synapse

Question 50

neurogenesis

Answer 50

Neurogenesis is the creation of new neurons

Question 51

neuroplasticity

Answer 51

refers to the ability of neurons to change in structure and function in response to change in structure and function in response to alterations in their environment

Question 52

cerebrospinal fluid

Answer 52

The brain and the spinal cord are further protected by a clear, plasma-like fluid known as cerebrospinal fluid (CSF)

Question 53

ventricles

Answer 53

CSF seeps out of the lining of hollow spaces in the brain known as the ventricles

Question 54

what happens when cerebrospinal fluid circulation gets blocked

Answer 54

CSF is constantly produced, so blockages in its circulation cause the fluid to build up The result is hydrocephalus, which means “water on the brain”

Question 55

when you get a blow to the head, what protects it

Answer 55

The cushioning provided by the CSF limits the damage produced by a blow to the head As a result, single minor concussions are unlikely to produce long-term problems, but medical experts are becoming increasingly concerned about the effects of multiple concussions

Question 56

spinal cord function

Answer 56

The spinal cord serves as a major conduit for information flowing to and from the brain along large bundles of nerve fibres, carrying sensory info from the body and delivering commands to muscles

Question 57

sensory neurons

Answer 57

Sensory neurons carry info from the external environment or from the body back to the CNS

Question 58

motor neurons

Answer 58

Motor neurons carry commands from the CNS back to the muscles and glands of the body

Question 59

interneurons

Answer 59

Neurons that have neither sensory nor motor functions are called interneurons

Question 60

cranial nerves

Answer 60

Directly branching from the brainstem are the cranial nerves, which perform the same functions for the head and neck areas that the spinal nerves manage for the remainder of the body

Question 61

cerebellum

Answer 61

Cerebellum helps us maintain balance and muscle coordination

Question 62

brainstem

Answer 62

Brainstem contains structures responsible for reflexive behaviours, heart rate, breathing, sleep, balance and movement

Question 63

medulla

Answer 63

The spinal cord merges with our first brain stem structure, the medulla Contains large bundles of nerve fibers to and from higher levels of the brain Manages many functions essential to life, such as heart rate, breathing and blood pressure

Question 64

pons

Answer 64

Above the medulla is the pons, which serves as a bridge between the higher and lower portions of the brain and connects the cerebellum to the rest of the brain