Physiology Quiz

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Sleep – Lecture 28

Active process: body rests, hormones get secreted to shut down, cardiovascular system shuts down during REM sleep. Theories on purpose of sleep:

Lets body rest

Lets brain recover and regenerate

Enhances memory

Enhances learning

Sleep supports immune system function and hormonal function. 25% pain tolerance after two consecutive sleepless nights.

Sleep-Wake Cycles

Ascending reticular activating system (ARAS)

Awakens the cortex

Projections to thalamus, hypothalamus and the forebrain

Forebrain: induces slow-wave sleep (SWS)

Hypothalamus regulates circadian rhythms

Adenosine builds up until you fall asleep and then it drops and then it starts to build again when you wake up

Reduce temperature to sleep

Study of Sleep

Electroencephalography (EEG) measures electrical activity of the brain

SWS, REM sleep

‘Cephalo’ = head

Stage 2 = beginning to fall asleep – K complexes trying to shut down systems (spindles are energizing short term memory from hippocampus to forebrain)

Stages 3 & 4, deep sleep (35 minutes) waves are getting bigger and slower, brain is shutting down and is pulsing to wash out the brain

REM sleep is same as awake stage. It is really important to build long-term memory.

Sleep Statistics/Guidelines

Youth (14-17): 8-10 hours/night

Adults (18-64): 7-9 hours/night

Older (64-79): 7-8 hours/night

20% of Canadian children and 30% of youth do not meet guidelines

35% adult men, 30% adult women and 28% of older adults do NOT meet recommended sleep duration.

In the past 40 years, we’ve lost 2 hours of sleep per night, the second hour was lost in the past 9 years (smartphones)

A poor night sleep is equivalent to being drunk. Eat 385 extra calories the next day.

Average sleep among university students is ~6-7.5 hours/night.

42% of youth, 43% men, 55% women report trouble going to sleep or staying asleep.

The use of anti-depressant medication has increased 400% in the last 30 years

30-75% of university students report stress and/or anxiety

Sleep Structure

Stages 1, 2, 3&4

REM sleep

Repair, renew

Contributors: drive, rhythm, structure

This is why coffee and alcohol also impair learning and memory – because they alter the deep sleep cycle. When you drink alcohol, it is both a depressant and a stimulant, so it shortens the deep sleep cycle by ~half. Caffeine activates your brain (reticular activating system) so that it takes longer to fall asleep, pulling your body out of circadian phase.

Circadian Timekeeping in Health

Physiological and behavioural drivers of body cycles:

Sunlight

Physical activity

Sleep

Diet

Patterned behaviours

40% of what we do in a day is patterned

Sunlight and physical activity = positive drive

Sleep = negative drive

Diet = drives metabolism

Hypothalamus and Pituitary Gland

Hypothalamus gets energy from everything that sets the rhythm. Pineal gland secretes melatonin that pushes us into sleep.

Hormonal Control by a Circadian Rhythm

Neural control of circadian rhythm à suprachiasmatic nucleus of the hypothalamus

Hormonal control of circadian rhythm à melatonin secreted by the pineal gland

Resets daily cycle based on light stimulus à also physical activity, sleep, diet

Pineal gland: glandular tissue in the brain. Secretes melatonin, involved in circadian rhythm important in timing of seasonal processes in mammals.

More Stats

Young adults spend 4-6 hours per day on a device

Average university student: ~6-7.5 hrs sleep/night

Stress = expectations have increased

Alcohol does not fuel your brain à it KILLS BRAIN CELLS

Things that Disrupt Sleep

Caffeine, nicotine

Alcohol

Artificial light (LED)

Presence of a device

Stress à work, family, money

Sleep cont. Lecture 29

How to improve sleep

Set a pattern of sleep: regular bedtime, have a wind-down period before bed (1-2 hours) and get up at the same time each day

Set a foundation for a good sleep: regular exercise, regular healthy meals, no electronics beside your bed

Sleep recovery: if you have a hard time falling asleep, get up and do something

Naps

Will reduce adenosine buildup – no longer than 20-25 minutes. After 25 minutes you enter stage 3 (deep sleep)

Emotions and Behaviour – Lecture 29

Motivation = drive

Physiological

Emotions (fear, anxiety, etc.)

Pleasure: is a strong motivating emotion: contextual memory

Strong motivating emotion

Pleasure centers contain dopamine

Pleasure can be addictive

We are driven to seek out pleasure and avoid pain

Structures in Emotions and Motivation

Emotions: amygdala à fear, anxiety; hypothalamus à anger, aggression

Midbrain

Limbic system

Modern Context of Motivation

Contextual memory served us as hunter-gatherers, motivated us to seek out food (high PA, reward = food)

Now we are battling strong genetic programming to be healthy in today’s society

Why sleep, healthy eating and PA are important

Low PA/sleep promotes unhealthy eating and vice versa

Hedonic eating = low dopamine; exercise = dopamine release and synthesis

Low sleep reduces will power to resist/motivation to move

Low PA also diminishes the drive to move

Learning & Memory: How the Brain Works (Lecture 29)

Learning: acquisition of new information

Memory: retention of information, skills, or thoughts

Plasticity

You remember everything, but forget due to:

Not registering information (LEARNING)

Inability to access information (MEMORY)

Retain 50% of information directly after class or reading

Associative Learning

Cognitive

Associate two stimuli

Non-associative Learning

Senso-motor

Habituation

Sensitization

Memory Processes

Declarative memory = explicit

Learned facts, events, and experiences

Requires conscious effort for recall

Hippocampus involved

Procedural memory = implicit

Automatic response not requiring conscious effort

Learned motor skills and behaviours

Cerebellum involved

Short-Term and Long-Term Memory

Information is first stored as short-term memory (amygdala + hippocampus)

Lasts seconds to hours (temporary, limited storage à 20% after 24h)

Lost unless consolidated

Consolidation from short-term memory

Synaptic consolidation: the synapse gets energized based on the number of action potentials go through that synapse

Systems consolidation: procedural memory component – whole system that has to be upregulated (REM memory cycles during sleep is both synaptic and systems consolidation).

Reconsolidation

Long-term memory

Last years to lifetime

Involvement of Limbic System means both are semantic and episodic component to long-term memory

Anatomy of a Synapse

Sustained electrical potentials change proteins = memories

Stronger potentials = stronger memories

Long-term potentiation enhances neural networks

A stronger release of action potentials creates stronger memories

Anabolic effort requires energy – if you keep enhancing it, you get long-term potentiation

Plasticity in the Nervous System

Learning and memory involve plasticity

Development of new synapses

Long-term memory modulation of existing synapses

Recently shown new neurons develop

“You are what you repeatedly do”

The Neuroscience of Mindfulness

“I hear and I forget. I see and I remember. I do and I understand.”

Confucius

Mindfulness: it means paying attention to anything in our experience and that means things that are happening through our sense doors…we can be mindful of listening, seeing, and felling. We can also be mindful of what is happening in our inner world, and that is basically our thoughts and emotions. Bringing awareness to our thoughts and emotions means that we’re starting to pay attention to the mechanics or the way our inner world operates. **give analogy of musicians and orchestra**.

How to Study Smarter

Be present

Important information only

Condense your notes into mental maps

Sleep the night before an exam

Life Hacks for Success in the Modern World

Mindfulness matters

Protect your sleep

Fuel your brain

Movement is medicine

Human Connection

Sensory Systems – Lecture 30

General Principles of Sensory Physiology

Perception: conscious interpretation of the world based on sensory systems, memory, and other neural processes. All sensory input is based on past experiences and what things mean.

Sensory Nervous System

Information from periphery to CNS

External environment:

Somatosensory system

Somatic

Proprioception (limb and body sensation)

Special Senses

Vision, hearing, taste, touch, smell

Equilibrium

Internal Environment

Visceral afferent (thermo, chemo, baroreceptors)

Baroreceptors = measuring blood pressure

Receptor Physiology

Sensory receptors: a single afferent neuron and all the receptors associated with it

Detect specific type à law of specific energies: light, sound, pressure, temperature, chemicals à generates receptor potential

Adequate stimulus à threshold – generates action potential

Sensory Pathways

Coding for stimulus type

Receptor type activated

Specific pathway

Labeled line theory specific neural pathway for each sense

Thalamus detects your attention

Sensory Coding

Coding for stimulus intensity

Frequency of action potentials

Number of receptors activated

Stronger stimulus activates more receptors (recruitment)

More pressure on pressure receptor, fire more action potentials, higher stimulus and results in higher frequency of action potentials

Stimulus Location

Perception of where sensation is coming from

Cody for quality and intensity

Also rely on behavioral actions

In some sensory systems (sound), localization is unrelated to coding by receptive fields

Somatosensory System

Body sensations by body position, pressure, temperature, pain

Proprioceptors: body position

Mechanoreceptors: pressure, force, vibration

Thermoreceptors: temperature

Nociceptors: harmful stimulation

Control of a Skeletal Muscle for Coordinated Activity across a joint

Receptors

Muscle spindle: senses change in length à velocity

Golgi tendon organ: senses change in tension à force

Activates muscles to contract, not to push*

Muscle Spindle

Intrafusal fibers, connective tissue, and sensory nerve endings

Detect muscle length

Typically, reflex excitation

Sensitivity adjusted by intrafusal fibers

Extrafusal fibers = skeletal muscle contraction that is innervated by alpha motor neurons

Stretch Reflex

Ensures proper neural excitation

Muscle Spindle Response

Muscle spindle feedback in relaxed muscle

No feedback when muscle is contracted

Lots of feedback when muscle is stretched

Golgi Tendon Organs

GTO

Sensory capsules within tendons

High force tendon stretch activates GTO

Reflex inhibition of muscle via type lb afferent neurons

Protection against damage of muscle

Senses high force and shuts off the muscle

The Pain Response

Sensation produced by tissue-damaging stimulus or stimulus that can potentially cause tissue damage

Pain elicits sensation, autonomic responses, and emotional responses

Pain perception depends on past experiences