Neurophysiology Flashcards
What is neurophysiology?
studying the functioning of the nervous system
In which area of the brain does thermoregulation happen?
Hypothalamus (Preoptic area POA)
WHat are endotherms?
regulate body temp with internal mechanisms (warm-blooded)
What are ectotherms?
no internal mechanisms, regulate body temp with external means (cold-blooded)
How does thermoregulation work?
through negative feedback mechanisms: a stimulus causes a system to react by causing the opposite output
What are cold and heat defense? What is the goal of this?
systems activated when the hypothalamus feels a drop/increase in temp via thermoreceptors
• Cold defense: decrease heat loss (constriction of blood vessels, shivering)
• Heat defense: increase heat loss (vasodilation, sweating)
Name the 2 pathways of thermal infromation to the brain, their destination and their function
• Spinothalamocortical pathway (STC): destination is the somatosensory cortex via the thalamus
○ Info leading to perception of temperature
• Lateral parabrachial nucleus (LPB): destination is POA (also called LPB-POA pathway)
○ Info leading to thermoregulation
Is the Spinothalamocortical pathway (STC) necessary to produce temperature-regulation behaviours?
No
WHat is energy homeostasis?
Process that maintains cellular metabolism (depends on a supply of calories and oxygen)
Energy demands of the body are met by: (3)
• The release of glycogen by the liver (transformed back into glucose)
• Release of triglycerides from fat cells, which are transformed into fatty acids and ketones
OR by food (macronutrients such as carbs, proteins and fats)
What is the prandial state?
immediately after eating, when your energy stores are replenished (being “fed”) and nutrients flow into the bloodstream
What is the postabsorptive state?
nutrients no longer enter the bloodstream, and body relies on energy stores in the liver as glucose and from fat cells (a while after eating)
What are hormones?
chemical messengers that can have effects on cells distant from the cells that released them
What is hunger?
drive generated when energy stores are not sufficient to sustain energy balance
What is satiety?
state of being fed to the feeling of satisfaction that follows a meal
Define ghrelin and its main role in the body
Ghrelin: hormone found mainly in the stomach
• It’s orexigenic: it promotes eating
• High levels 20-30 mins before a meal, when there is no food in stomach
Define leptin and its main role in the body
Leptin: hormone produced/released from stomach, and suppresses hunger (anorexigenic)
• Secreted in response to high levels of insulin and glucose (will be more secreted after a large meal for a few days)
What is insuline? (role, effect)
- Also anorexigenic
- Relesaed by cells of pancreas
- Related to glucose levels
- Inhibits AgRP and NPY in the arcuate nucleus and has excitatory effect on POMC and CART neurons
What is cholecytokinin (CKK)? (role, effect)
- Released from small intestine when stomach is full
- Binds on receptors of vagus nerve and carries inhibitory messages to hypothalamus
- Suppresses appetite
What is peptide tyrosine tyrosine (PYY)? (role, effect)
- Released from large intestine after meals
- Suppresses appetite by inhibiting ArGP and NPY
- Has no effect on POMC and CART neurons
What does orexigenic means?
Promotes eating
What does anorexigenic means?
Suppresses hunger
What is the difference between homeostatic and non-homeostatic eating?
Homeostatic: to satisfy hunger and bring body back to homeostasis
Non-hom.: for pleasure and reward, not hunger
What can generate a non-homeostatic drive?
Environmental cues + memory of food
What is polysomnography?
measures the brain’s electrical activity, eye movements, and muscle contraction when sleeping
What is an Electrooculography (EOG)?
records the eye movements through changes in the electrical activity of eye muscles
What is an Electroencephalography (EEG)?
records the brain’s electrical activity
WHat is an Electromyography (EMG)?
recording of movements of the body through measuring changes in the electrical activity of the muscles
What are brain waves? Name the 4 different types
result of the electrical activity of the brain, and like sound waves, they vary in frequency and amplitude
• Different sorts of brain waves are identified as alpha, beta, theta, and delta
Name the events and waves associated with the stage 1 of sleep
Transitional sleep - transitional state between asleep and awake (happens only once)
• Theta waves
Name the events associated with the stage 2 of sleep
Sleep spindles (high-frequency spikes of activity lasting from 0,5 to 1 second) and K-complexes (slightly negative deflections in a wave following by a positive deflection) • Light form of sleep - person easily awakened (may not know they were sleeping)
Name the events and waves associated with the stage 3 and 4 of sleep
Deep sleep (high amplitude and low-frequency wavelengths - delta waves)
• Person difficult to wake up (not happy to be woken up)
• Also known as slow-wave sleep (SWS)
What is REM sleep? What waves are associated with it?
brain activity that resembles wakefulness (beta waves)
• AKA paradoxical sleep
• Muscle paralysis - to avoid acting out dreams
How much of our sleep do we spend in REM?
25%
Just name the 3 main factors influencing the sleep-wake switch
Homeostatis influences
Circadian influences
Zeitgebers
What is the humoral theory of sleep regulation? Why is it not good?
the degree of wakefulness is related to the accumulation of somnogens that lead to the homeostatic drive for sleep (can’t fully explain the sleep cycles since our alertness varies through the day)
• Somnogens: chemicals that build up in the system
What are homeostatic influences on sleep?
Homeostatic influences: chemical buildup in the physiological system that induces sleep
What are circadian rhythms?
physiological, behavioural or psychological events that occur over a 24-hour cycle
What are the 2 types of circadian rhythms?
- Entrained circadian rhythm: regulated by external cues
* Free-running rhythm: self-regulated
What is the second wind effect?
Second wind effect: periods of alertness interspersed with periods of sleepiness after being sleep deprived
What is the master clock controlling the circadian rhythm? How does it work?
the suprachiasmatic nucleus (SCN) in the hypothalamus
• Influenced by light-dark cycles captured by melanopsin, a photopigment in the photoreceptors of the retina.
○ Called retinohypothalamic projections
○ Leads to the release of melatonin from the pineal gland
What are the neurotransmitters promoting wake up?
- Norepinephrine
- Serotonin
- Histamine
- Glutamate
- Acetylcholine
- Hypocretin (neuropeptide) (AKA orexin) maintains wakefulness
What are the neurochemicals promoting sleep?
• GABA • Glutamate • Adenosine • Melatonin/melanin (hormones) These also suppress the activity of excitatory neurotransmitters that promote waking
What is the principle of the wake-sleep switch?
No transition stage between awake and asleep
What is the system promoting wakefulness? What does it do?
The Ascending arousal system (AAS) excites the cortex to promote wakefulness
The AAS is a bundle of structures within the brainstem:
• Pendunculopontine/laterodorsal tegemental nuclei (PPT/LDT)
• Locus coeruleus (LC)
• Raphe nucleus (RN)
• Tuberomammillary nucleus (TMN)
What are the 2 projections that the AAS does to the cortex to excite it?
Direct and indirect pathways
How is activity in the AAS induced?
When orexinergic neurons in the Lateral Hypothalamus are excited
How is sleep induced?
When the AAS is inhibited
Describe the hormonal route of gherlin
Travels to the hypothalamus (arcuate nucleus) and binds to neuropeptide-Y (NPY) and agouti-gene-related peptide (AgRP)
• Causes these peptide neurotransmitters to be released into the paraventricular nucleus (PVN) (region of hypothalamus), where they will bind to receptors on melanin-concentrating hormone (MCH) and corticotropin-releasing factor (CRF) and will generate hunger signals
Describe the neuronal route of gherlin
When released into the stomach, ghrelin will bind to receptors on the vagus nerve and carry excitatory messages to the hypothalamus though the nucleus of the solitary tract (NST)
Describe the hormonal route of leptin
Inhibits the release of AgRP and NPY from neurons
• Also excites neurons containing neuropeptides prooppiomelanocortin (POMC) and cocaine-amphetamine-relatedtranscript (CART) - those will be released in the PVN and will inhibit the function of MCH and CRF (will NOT generate hunger signals)
Describe the neuronal route of leptin
Also binds to receptors on the vagus nerve which sends inhibitory messages to the hypothalamus through the NST
