Neuron Structure and Function

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Questions and Answers

What is the primary function of dendrites in a neuron?

To provide insulation for the axon

To transmit electrical signals to the body

To receive messages from other neurons (correct)

To secrete neurotransmitters

Which part of the neuron is responsible for the life support functions?

Myelin sheath

Soma (correct)

Terminal buttons

Axon

What occurs when an action potential reaches the terminal buttons?

The neuron stops firing altogether

Dendrites receive neurotransmitters

Neurotransmitters are released into the synapse (correct)

The axon regenerates

What is meant by the 'all or nothing' phenomenon in neuronal firing?

When stimulated, a neuron either fires completely or not at all Signup and view all the answers

What role do agonists play concerning neurotransmitters?

They mimic the action of neurotransmitters Signup and view all the answers

What is the role of the iris in the eye?

It helps control the size of the pupil. Signup and view all the answers

Which condition is characterized by nearby objects appearing blurry?

Hyperopia Signup and view all the answers

What change occurs in the lens of the eye to focus on nearby objects?

The lens thickens. Signup and view all the answers

Which type of photoreceptor is primarily responsible for color vision?

Cones Signup and view all the answers

What is the function of the optic nerve?

To connect the eye to the brain. Signup and view all the answers

What is the term for the smallest difference between two stimuli that a person can notice half of the time?

Difference threshold Signup and view all the answers

Which phenomenon describes the failure to notice unexpected events while focused on a specific task?

Inattentional blindness Signup and view all the answers

Which of the following explains why larger differences between stimuli need to be perceived as more significant for them to be noticed?

Weber's Law Signup and view all the answers

What role does the pupil play in the visual system?

Adjusts to control light intake Signup and view all the answers

What describes the use of previous experiences and expectations to interpret sensory information?

Top-down processing Signup and view all the answers

What is the primary function of glia cells in the nervous system?

Support, nourish, and protect neurons Signup and view all the answers

Which component of the nervous system is responsible for controlling voluntary movements?

Somatic Nervous System Signup and view all the answers

During which sleep stage is the body paralyzed while the brain is highly active?

REM sleep Signup and view all the answers

What typically happens to the duration of deep sleep and REM sleep as the night progresses?

Less time in deep sleep, more time in REM Signup and view all the answers

What is a characteristic feature of dreaming during REM sleep?

Dreams are more vivid, emotional, and memorable Signup and view all the answers

Which part of the nervous system is involved in managing the body's resources during emergencies?

Sympathetic Nervous System Signup and view all the answers

How do daily experiences and culture influence dreams?

They affect the content and themes of dreams Signup and view all the answers

What distinguishes the afferent nerve fibers in the nervous system?

They carry sensory information to the CNS from the body Signup and view all the answers

What does Freud's concept of latent content in dreams refer to?

The hidden meaning of the dream. Signup and view all the answers

Which theory suggests that dreams are a result of random neural activity during REM sleep?

Activation-Synthesis Theory Signup and view all the answers

What is a common effect of classic hallucinogens like LSD?

Distortion of time and sensory perceptions Signup and view all the answers

Which of the following is a potential medical use of MDMA?

Treatment of PTSD Signup and view all the answers

What is a common misconception about marijuana?

It leads to amotivational syndrome. Signup and view all the answers

What distinguishes MDMA from other stimulants?

It has empathogenic properties. Signup and view all the answers

What are the effects of high doses of marijuana?

Paranoia and panic Signup and view all the answers

Which phenomenon is associated with both sleep paralysis and hypnogogic experiences?

Hallucinations Signup and view all the answers

Which of the following statements is true regarding the use of classic hallucinogens?

They can cause a mystical or dream-like state. Signup and view all the answers

What characteristic is associated with the activation-synthesis theory of dreaming?

Dream content is synthesized from random brain activity. Signup and view all the answers

Study Notes

Neuron

A neuron is a cell that receives, integrates, and transmits information within the nervous system.

Parts of a neuron

Dendrites receive messages from other neurons.
The soma is the cell body and contains the cell nucleus, which acts as the life support of the neuron.
The axon is a long, thin fiber that transmits signals away from the soma.
The myelin sheath is an insulating material that coats the axon and speeds up the transmission of information.
Terminal buttons, small knobs at the end of the axon, secrete neurotransmitters to transmit the neuron's message.
The synapse is a tiny gap between neurons where information is transmitted.

How a neuron transmits information

An action potential, a brief electrical charge, travels down the axon to the terminal buttons.
When it reaches the terminal buttons, they release neurotransmitters into the synapse.
Neurotransmitters are chemical messengers that travel across the synapse to receptors on the dendrites of other neurons.
When enough neurotransmitters bind to receptor sites on the next neuron's dendrites, it causes the neuron to fire.
This is an "all or nothing" phenomenon, meaning the neuron either fires completely or not at all.

Neurotransmitters

There are several types of neurotransmitters, each with specific functions.
Receptors on dendrites are specialized, meaning only certain neurotransmitters can bind to them.
Reuptake is the process of reabsorbing unused neurotransmitters.
Agonists are chemicals that mimic the action of neurotransmitters, causing similar effects. They can also stop reuptake.
Antagonists are chemicals that oppose the action of neurotransmitters by blocking the receptor sites.

Other cells in the brain

Glia cells support, nourish, and protect neurons.
They supply nourishment, get rid of waste (dead neurons and extra sodium ions), and provide insulation.

The Nervous System

The nervous system is an electro-chemical communication system.
It has two major branches: the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS includes the brain and spinal cord.
The PNS includes all nerves outside of the brain and spinal cord.

Somatic Nervous System

The somatic nervous system connects to voluntary skeletal muscles and sensory receptors. It controls all voluntary movement of the body.
Afferent nerve fibers carry information to the CNS from the body.
Efferent nerve fibers carry information to the body from the CNS.

Autonomic Nervous System

The autonomic nervous system consists of nerves that connect to the heart, blood vessels, organs, and glands.
The sympathetic nervous system mobilizes the body's resources for emergencies.
The parasympathetic nervous system calms the body and conserves resources when there isn't an immediate threat.

Stages of Sleep: REM

REM sleep is characterized by rapid eye movements (REM), active brain waves similar to beta waves, high levels of physiological arousal, and body paralysis.
It is also known as paradoxical sleep because the body is still and peaceful while highly aroused.
Frequent dreaming occurs in REM sleep and the majority of dreams happen during REM.

Stages of Sleep

Every night, we cycle through sleep stages multiple times: 1 - 2 - 3 - 2.
Instead of re-entering stage 1, we enter REM.
The cycle repeats throughout the sleep period: 1 - 2 - 3 - 2 - REM - 2 - 3 - 2 - REM.
Each cycle takes about 90 minutes.
As the night progresses, we spend less time in deep sleep and more time in REM.

Dreaming

Everyone with a healthy brain dreams.
During REM sleep, dreams are more frequent, bizarre, emotional, vivid, and memorable.
NREM dreams are less frequent and tend to be mundane and boring.
Dreams usually include familiar people and places.
They are affected by our daily experiences and culture.
The majority of dreams have negative content, which may be because they are more memorable.

Dreams: What Do They Mean?

Freud's psychoanalytic theory suggests dreams represent unconscious desires and conflicts.
- Manifest content is the actual content of the dream.
- Latent content is the hidden meaning of the dream.
There is no evidence to support this view and it is considered subjective.
The activation-synthesis theory proposes that dreams are a byproduct of neural activity. Random activation of the brain triggers sensory systems, and the brain makes sense of this by synthesizing it with memories.
The threat simulation theory suggests dreams allow us to rehearse survival strategies.
The social simulation theory suggests dreams allow us to rehearse social and behavioral strategies.

Sleep Problems and Disorders

Sleep paralysis involves waking up feeling paralyzed. It usually occurs when waking up or falling asleep.
Cause: The brain wakes up before deep muscle relaxation of REM sleep stops.
Hypnogogic sleep paralysis is a type of sleep paralysis that also includes hallucinations.
Stress, sleep deprivation, and alcohol increase the likelihood of experiencing sleep paralysis.

Psychoactive Drugs: Hallucinogens

Hallucinogens distort perceptions and evoke sensory images in the absence of sensory stimulation.
Classic hallucinogens (LSD, DMT, Psilocybin) affect the serotonin system.
They have dramatic effects on senses: sensations are intensified, hallucinations occur, and time distortion is experienced.
Synesthesia is a blending or crossing of sensory perceptions, such as tasting green while eating lettuce.
Hallucinogens also affect mood and thoughts: they can cause intense emotions, mystical or dream-like states, and "bad trips."
There is a possibility for medical uses: treatment of alcohol, nicotine, and cocaine dependence; treatment of anxiety, depression, and fear of death in terminally ill patients; and treatment of "treatment-resistant" depression.
There is a very low chance of dependency, and no withdrawal effects, but tolerance (and cross-tolerance) develops quickly.

MDMA

MDMA is difficult to classify, possessing properties of both stimulants and hallucinogens.
It is a serotonin agonist (increases serotonin, the "feel good hormone"), and also increases dopamine levels.
MDMA has energizing effects and creates feelings of euphoria. It has aphrodisiac properties, which can lead to riskier sexual practices.
MDMA is also an "empathogen," enhancing social intimacy, empathy, trust, and feelings of safety.
Possible medical uses: treatment of PTSD.
Concerns and risks: dehydration, long-term heavy users have an increased risk of depression, anxiety, sleep disorders, and memory and cognitive deficits due to damage to the serotonin system. These effects may not be permanent, but it's impossible to know how strong or pure the drug is.
Tolerance builds quickly, mild withdrawal symptoms are possible, but dependency rates are low.

Marijuana

Marijuana is the most widely used illegal drug in the US.
It is difficult to classify, exhibiting properties of stimulants, depressants, and hallucinogens.
It acts on the brain's natural endocannabinoid system, affecting many areas of the brain to produce a variety of effects.
Effects include relaxation, euphoria, time distortion, increased appetite, enhancement of sensation and feelings, and memory impairment.
Medical uses: pain relief, appetite stimulation, control of nausea, reduction of tremors and seizures.
Correcting common misconceptions: marijuana does not cause "amotivational syndrome" and it is not a "gateway drug."
Harmful effects: lung damage from smoke; high doses can cause paranoia, panic, fast heart rate, nausea, and vomiting; reaction times slow down, judgment and thinking are impaired (no driving); memory problems.
People can become addicted (dependent) on marijuana. Heavy users may experience mild withdrawal symptoms, and psychological dependency can occur. It's estimated that about 5% of users develop dependency.

Sensation and Perception

Sensation is the stimulation of the sense organs.
Perception is the process of organizing and interpreting sensory information.
The absolute threshold is the lowest intensity at which a participant notices a stimulus half the time.

Sensation

The difference threshold (also known as the just noticeable difference) is the smallest difference between two stimuli that is needed for a person to notice half the time.
Weber's Law states that differences between larger or more intense stimuli need to be larger to be noticed.
Selective attention is the ability to focus on a specific stimulus while ignoring others.
- Inattentional blindness is the failure to notice unexpected events when working on a task.
- Sensory adaptation is a change in the responsiveness of the sensory system based on the average level of surrounding sensation.
Bottom-up processing uses individual sensory pieces to build and perceive whole sensory events.
Top-down processing uses context, expectations, etc. to perceive whole sensory events.

Visual System

Vision is the dominant sense for most humans.
The McGurk Effect demonstrates that what we see can change what we hear.
The pupil is the black hole in the eye that light enters. It changes size to control the amount of light that enters the eye.
The iris is the colored part of the eye and helps control the size of the pupil.
The cornea covers the outside of the eye.
The lens is a transparent structure behind the pupil that changes shape to focus light on the back of the eye.
- Accommodation is when the lens adjusts to focus an image.
- The image is inverted when it hits the back of the eye, but the brain processes it and flips it right side up.
Nearsightedness (myopia) is when faraway objects are blurry. The eye is too long.
Farsightedness (hyperopia) is when nearby objects are blurry. The eye is too short or the lens does not thicken enough.
Presbyopia is "old vision." Nearby objects are blurry. The lens becomes less elastic with age.
Glasses change the focus of the image.
The retina is the inner surface of the eye, made up of photoreceptors, which are light-sensitive neurons.
Types of photoreceptors:
- Cones are short, stubby cells located in the center of the retina. The fovea, the center of the retina, contains only cones. Cones are responsible for vision in bright light, color vision, and fine detail.
- Rods are elongated cells concentrated on the sides of the retina. They are more sensitive to light, responsible for night vision, vision in low light, and peripheral vision. They are not sensitive to color.
The optic nerve is formed by the axons of all neurons in the retina gathering together and leaving the eye through the optic disc.
The blind spot is a hole in the retina where light cannot be processed.

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Description

Explore the intricate structure and functions of neurons in the nervous system. This quiz covers key components such as dendrites, axons, myelin sheath, and neurotransmitter transmission. Test your knowledge on how neurons transmit information effectively.