Lecture 5: Consciousness

What can pass the Blood Brain Barrier?

• Transporter proteins → shuttle specific molecules across membranes

• Dissolving through the blood vessel cell walls → Hydrophobic (lipophilic) molecules can pass through the hydrophobic lipid bilayer (oxygen, drugs)

What is substance use disorder?

compulsive pattern of drug use despite negative consequences (involves physical and psychological dependence)

Physiological dependence

involves changes in normal bodily functions and withdrawal upon cessation of use

Psychological dependence

emotional need for the drug

Tolerance

occurs when a person requires more and more of a drug to achieve effects previous experienced at lower doses; linked to physiological dependence

Withdrawal

negative symptoms experienced when a drug use is discontinued

GABA (Gamma-aminobutyric acid)

The major inhibitory neurotransmitter in the brain and spinal cord

What does GABA do?

Blocks the signals of excitatory neurotransmitters

What happens as a result of low levels of GABA?

Low levels may be responsible for anxiety and panic

Glutamate

The primary excitatory neurotransmitter in the mammalian brain

What does glutamate do?

Important for longer term processes and learning and memory

Other neurotransmitters are:

Acetylcholine, endorphins, dopamine, norepinephrine, and serotonin

Acetylcholine

muscle action and memory

Endorphins

pain and pleasure

Dopamine

mood, sleep, and learning

Norepinephrine

heart, intestines, alertness

Serotonin

mood and sleep

Effects of Depressants

suppress central nervous system activity

Examples of depressants

alcohol, barbiturates, benzodiazepines

What do depressants do to GABA receptors?

• GABA agonists have a quieting effect on the brain

• Work by binding to GABA receptors, which makes the neuron less likely to fire.

What are the effects of alcohol?

• Decreases reaction time and visual acuity

• Lowers levels of alertness

• Reduces behavioral control

• Can result in complete loss of consciousness

Effects of Stimulants

increase overall levels of neural activity

Examples of stimulants

cocaine, amphetamine, cathinones (bath salts), MDMA

What do stimulants do to dopamine receptors?

• Usually dopamine agonists, which work by preventing the reuptake of dopamine.

• Dopamine activity is associated with reward and craving, therefore these drugs can be highly addictive.

• Dopamine agonists such as cocaine and amphetamines block the reuptake of dopamine from the synapse into the presynaptic cell

  • Results in a larger amount of dopamine in the synapse 

Effects of caffeine

• Involves antagonizing adenosine activity

• Increases levels of alertness and arousal

Effects of nicotine

• Interacts with acetylcholine receptors

• Highly addictive 

• Plays a role in arousal and reward mechanisms

Effects of opioids

serve as analgesics (decrease pain) through their effects on the endogenous opioid neurotransmitter system and are highly addictive.

Examples of opioids

heroine, morphine, methadone, codeine, fentanyl

Effects of Hallucinogens

Causes changes in sensory and perceptual experiences. It can involve vivid hallucinations.

• Variable with regards to the specific neurotransmitter systems they affect.

What do Mescaline and LSD do?

They are serotonin agonists

What do PCP and ketamine do?

They are NMDA glutamate receptor antagonists

Circadian rhythm

a biological rhythm that occurs over approximately 24 hours.

What is the circadian rhythm generated by?

It is generated by the suprachiasmatic nucleus (SCN)

What is the hypothalamus responsible for?

maintaining homeostasis

Homeostasis

Tendency to maintain a balance, or optimal level, within a biological system

Suprachiasmatic Nucleus (SCN)

• In the hypothalamus

• Serves as the brain's clock mechanism

• Clock sets itself with the light information received through projections from the retina, allowing it to synchronize with the outside world.

What does Melatonin do?

• regulates our sleep wake cycle

• is stimulated by darkness, making us sleepy and inhibited by daylight

Pineal Gland

The gland that releases melatonin

Adaptive function (evolutionary hypothesis)

• Sleep is essential to restore resources that are expended during the day  

• Sleep is an adaptive response to predatory risks, which increase in the darkness

• There is little evidence to support these explanations (they are hypotheses)

Cognitive Function:

 focuses on sleep’s importance for cognitive function and memory formation

What does sleep deprivation result in?

results in disruptions in cognition and memory deficits, which become more severe as it increases

What is slow wave sleep essential for?

effective memory formation

Jet Lag

 symptoms resulting from mismatches between our internal circadian cycles and the environment

Symptoms of jet lag

Fatigue, sluggishness, irritability, insomnia

Light Exposure

Bright light can be used to realign our biological clocks with the external environment

What does light exposure do?

• Helps people maintain a regular circadian cycle

• Helpful for people working night shifts or those affected by seasonal variations in light

Sleep debt

result of insufficient sleep on a chronic basis

Sleep rebound

a sleep deprived individual will tend to take a shorter time to fall asleep during subsequent opportunities for sleep

What are the five types of brain waves?

Gamma, Beta, Alpha, Theta, Delta

Gamma Waves

insight, peak experiences, synchronization

Beta Waves

alertness, concentration, thinking

Alpha Waves

meditation, creativity, relaxation

Theta Waves

visualization, trances, dreaming

Delta Waves

deep sleep, transcendence, restoration

What are the sleep stages?

Stages 1 and 2, stages 3 and 4, REM sleep

Stage 1 (Alpha Waves)

• Transitional phase between wakefulness and sleep 

• Rates of respiration and heartbeat slow down

• Overall muscle tension and core body temperature decrease

Stage 2 (Theta Waves)

• Body goes into deep relaxation

• Characterized by appearance of sleep spindles and K-complexes

  • Sleep spindles → rapid burst of high frequency brainwaves

  • K-complexes → very high amplitude pattern of brain activity

Stages 3 and 4 – Deep Sleep (Delta Waves)

• Known as slow-wave sleep

• Respiration and heart rate slow down further

Rapid Eye Movement (REM) Sleep

paralysis of voluntary muscles; dreams; brain waves are similar to those seen during wakefulness.

Insomnia

difficulty falling or staying asleep for at least 3 nights a week for at least one month’s time

• Most common sleep disorder and may be associated with symptoms of depression

What are contributing factors to insomnia?

age, drug use, exercise, mental status, bedtime routines

What are some treatment options for insomnia?

• Stress management techniques

• Changes in problematic behaviors that could contribute to insomnia

• CBT, which focuses on cognitive processes and problem behaviors.