Sleep And Internal Regulation Flashcards
Homeostasis
maintenance at a set point
Allostasis
adaptive way body anticipates needs
Types of temperature regulation
• Poikilothermic (exothermic): Body matches environment and external sources used to regulate temp. EG huddling together
• Homeothermic (endothermic): Internal mechanisms used, eg sweating. High rates of energy
Why control body temp?
Pro: muscles benefit.
Con: high energy load
Regulation is controlled by…
Regulation controlled by hypothalamus. POA = physiological, AH = behavioural
Angiotensin II
constrict blood vessels and increase BP
Vasopressin
antidiuretic, compensates for decreased water volume
How can thirst be triggered
Osmotic and hypovolemic
Osmotic thirst
Osmotic (high conc of solute creates osmotic pressure
Hypovolemic
low fluid volume, causes a drop in BP to initiate production of vasopressin
Signal to stop hunger
Distension of stomach
Vagus nerve
conveys info about stretching to brain
Splanic nerves
convey info about nutrient contents
Duodenum
site of nutrient absorption. Releases hormone CCK which regulates hunger.
Arcuate nucleus
receives information re hunger.
Contains two neurons: NPY (increase, inhibit of paraventricular nucleus) and POMC (suppress, deliver excitation to paraventricular nucleus).
Ghrelin
hunger hormone – release from stomach into blood stream, influences hypothalamus, inhibited by leptin.
Lateral hypothalamus role
Hunger
Paraventricular nucleus
Satiety
Endrogenous biological rhythms
Circadian, infradian, circannual, ultradian
Zeitgeber
Stimulus that resets circadian rhythm. Primary is sunlight
Suprachiasmatic Nucleus (SCN)
main control centre. Located above optic chiasm, internal timekeeper and receives input from hypothalamic path
Retinohypothalamuc path
light resets the SCN via branch in optioc nerve
Mêla Papin
Special ganglion cells have their own photopigment (melanospin). These cells do not require input from photoreceptors (rods/cones)
Proteins for SCN
• Clock and BMAL1: Transcriptors for PER and CRY
• PER and CRY inhibit CLOCK and BMAL1
• PER and CRY broken down resulting in increased transcription
Melatonin
released by pineal gland, receives input from and affects activity of SCN
Wakefulness maintained by
ARAS
Wakefulness - areas involved
Pons, locus coeruleus, raphe nuclei, PAG, thalamus, hypothalamus
Transmit wakefulness by
Midbrain to cortex via thalamus, midbrain to cortex via lateral hypothalamus and basal forebrain
ARAS - information from
Receives input from sensory systems. Both paths most active while awake.
Sleep inhibition relies on
ARAS. Ventrolateral preoptic area sends inhibition.
Regulation of sleep-wake cycle
ARAS, SCN, Pineal gland and melatonin
ARAS maintains wake via
two pathways (M > C (T), M > C (Lat hyp, bas fore)
Stages of sleep
Understood VIA EEG, combines measures of heart rate, resp rate, BO levels, eye and leg movements
• Stages of sleep: NREM 1-4 sleep, REM (paradoxical sleep).
Activation-synthesis hypothesis:
Spont PGO waves activate cortex, and forebrain attempts to synthesise and interpret these waves
Clinico-Anatomical hypothesis:
Activity is high in parietal cortex (visual-spatial) and hypothalamus/amygdala (emotional/motivation). Activity is low in primary visual cortex, auditory cortex and primary motor cortex.
