Week 06 Flashcards
The body clock is located in the…?
Suprachiasmatic nuclei (SCN)
________ retinal ganglion cells detect dawn/dusk cycle and project to SCN
Photosensitive
Suprachiasmatic nuclei
(SCN) controls secretion of _____
melatonin
Melatonin is secreted from _______ gland
pineal
When is body temperature the lowest?
During sleep
Body temperature starts to increase prior to ______ and gradually increases to peak at ____
waking, the evening (few hours before sleep)
Body temperature peaks when?
In the evening
Three ways to measure body temperature?
- Gut temp - swallowing a pill
- Rectal - inserting probe in rectum
- Axilla - armpit thermometer
Without cues (time-givers) the body clocks runs for how long?
Just over 24 hrs
Body clock is adjusted by ________
zeitgebers (time-givers)
What are examples of zeitgebers (time-givers)???
light, dark, mealtime, physical activity, social interaction
When you travel to different time zones, how does this affect the adjustment of your body clock?
Body clock adjusts quicker when travelling west (time is behind, it is easier to delay your body clock because it naturally runs about 24 hrs than to advance your body clock)
Complex aspects of performance (e.g. cognitive tasks - arthmetic, short term memory, concentration): peak at what time?
early morning
Fine motor skills peak at what time?
morning
Simple reaction time is fastest in the….
morning, but inverse relationship between speed and accuracy (not good for tennis serve for example, which needs speed AND accuracy)
- Accuracy better in morning
- Velocity better in afternoon
Flexibility peaks at what time?
Early evening
Strength peaks at what time?
Early evening, but not as clear in females (muscle mass? central command?)
Anaerobic power/short burst activities peaks at what time?
Early evening
Prolonged exercise peaks at what time?
Early evening (depending on outdoor temperature)
Self paced work (e.g. cycling time trials) peak at what time?
Early evening
_________- is best time of day to beat an athletic world record
early evening
There is a nocturnal ____ followed by a morning surge in blood pressure
dip
____% of variation in blood pressure due to endogenous rhythm
10-15%
Mean arterial pressure =
CO x total peripheral resistance
The _____ adjusts cardiac output and peripheral vascular tone to regulate blood pressure
baroreflex
The baroreflex adjusts cardiac output and peripheral vascular tone to regulate blood pressure by causing changes in ____________ output to heart and ____________ to heart and systemic vasculature
vagal parasympathetic, sympathetic output
Baroreceptors are __________ afferent nerve terminals in carotid sinuses and aortic arch
Mechanosensitive
Baroreceptors are mechanosensitive afferent nerve terminals in _____ and _____
carotid sinuses, aortic arch
Baroreceptors detect….?
vessel stretch caused by changes in blood pressure
Baroreceptors are innervated by nerves that synapse in the nucleus …..?
tractus solitarius
R wave is the…?
Peak of heart beat
RR interval is the…?
distance between R waves
RR interval being small means that…
Heart rate must be high (fast)
RR interval being large means that….
Heart rate must be low (slow)
Changes in sympathetic nerve activity in blood vessels helps to control blood pressure by causing _________
vasoconstriction
Cardiac baroreflex sensitivity: when blood pressure is higher the baroreflexes responded by _______ RR intervals
increasing (to slow)
- the opposite occurs if BP is low
Sympathetic baroreflex sensitivity: We measure ____ blood pressure and nerve activity
diastolic
Cardiac baroreflex sensitivity: We measure ______ blood pressure for every beat and RR interval
systolic
Sympathetic baroreflex sensitivity: As diastolic blood pressure rises, nerve activity goes ______
Down
- vessels dilate to bring BP down again
- Opposite occurs to bring fallen BP back up
A strong cardiac baroreflex does/doesn’t guarantee a strong sympathetic baroreflex
Does NOT (best to measure both if possible)
Cardiac baroreflex sensitivity was ______ in the morning as hypothesised, stretch response of carotid artery may different in time of day
worse
Increase in BP = carotid stretched _____ in morning
Less (explains poor baroreflex in morning, not activated as much)
Was there a difference in sympathetic baroreflex sensitivity in morning and afternoon?
No
Increased mental stress in young years linked to greater risk of _______ later in life
Hypertension
No difference in BP and HR response in mental stress and cold pressor test (hand in ice cold water) between morning and afternoon.
- HOWEVER, found that evening times were more reactive to stress in the morning, and those with morning tendencies were more reactive to stress in the evening—> What does this show?????
SUGGESTS our chronotype might have a role to play in our stress response at different times in the day
Study of swimmers and their chronotype suggested that _____ difference between morning and evening performance when the swimmers were considered as a single group
No, contrary to statement that performance is best in evenings
Does our chronotype stay the same as we age?
Teenagers - tend to be more night owls
Adults - tend to be more morning larks
Melatonin secretion may _____ with age
decline
With age, sleep…
tends to have earlier onset and wakening (greater sleep with age)
There is ______ phase shifting with age
impaired
Possible underlying mechanism of age related changes in circadian rhythm?
Yellowing and thickening on lens in eye may lead to reduced light sensitivity, which is the strongest time giver
|
This may lead to decreased signalling in SCN, leading to decrease in overall amplitude in its firing
|
Inputing other time givers may help entrain ageing circadian system
_________ in old age helps maintain good circadian rhythm
Physical activity
Exercise performance tends to peak in the _____, coinciding with the peak in body temp (except tasks involving cognition and or fine motor skills which tend to peak in the ______)
early evening, morning
The incidence of cardiovascular events tend to peak in the _______ and may be explained, in part, by diminished blood pressure control
morning,
Ageing is associated with a dampening in ______________, phase shifts and a greater tendency towards ‘morningness’. These are reflected in exercise performance
circadian rhythms
Athletic performance typically peaks in the afternoon/ early evening, coinciding with what??
peak in core body temperature
Ageing can influence the body clock. Melatonin increases/decreases with age?
decreases
At what time of day is there a peak in the incidence of cardiovascular events, coinciding with a rise in blood pressure?
During the morning
At a given work rate, children generate ____ heat per kg of body mass than adults
more
Children have a relatively ____ body surface area for dissipating heat
smaller
Sweating rate is significantly ____ in children than adults
smaller
Lower thermoregulatory in older adults -> Older adults under cold stress have:
- less shivering
- Less peripheral vasoconstriction
- Lower resting heat production
- sarcopenia
Lower thermoregulatory in older adults -> Older adults under heat stress have:
- lower cutaneous perfusion/inability for peripheral vasodilation
- Smaller increase in CO / SV
- Less redistribution of BF from renal and splanchnic regions
