For 1QQsLast name, First name

Question #

a b c d e

Announcements

• Turn in Personal Information (place on Piano.)

• Reading and Chapter Questions– Will finish Thermoregulation Today and– Glucose Homeostasis on Monday– By Monday,complete all Glucose

Homeostasis Questions

1QQ Sample QuestionsName on top edge, back side of paperAnswer on blank side of paper.Answer one of the following:

1.The San people of Botswana were clothing made of tanned animal skins. A) What would be the preferred type of clothing for their hot desert environment, b) why would it be preferred (think heat exchange mechanisms) and c) why do you suppose they don’t wear what would be preferred?

2.What is the difference between a reflex and a negative feedback loop?

1QQ # 2 for 8:30Name on top edge, back side of paperAnswer on blank side of paper.

1. For the negative feedback loop for thermoregulationa) The hypothalmus is an afferent pathwayb) Somatic nerves are the efferent pathway to sweat

glandsc) Skeletal muscle tone would be increased as a

response to a drop in core body temperatured) Peripheral nerves are the afferent pathway that

convey skin temperature informatione) Cutaneous arterioles would dilate in response to a

drop in core body temperature.

1QQ # 2 for 9:30Name on top edge, back side of paperAnswer on blank side of paper.

1. For the negative feedback loop for thermoregulationa) The hypothalmus is an efferent pathwayb) Somatic nerves are the efferent pathway to

skeletal musclesc) Skeletal muscle tone would be decreased as a

response to a drop in core body temperatured) Peripheral nerves are the afferent pathway that

convey skin temperature informatione) Sympathetic nerves would lead to constriction of

cutaneous arterioles in response to a drop in core body temperature.

Add coversor clothingor enter sleeping bag

Skin tempAnd Core body temp

Detected by thermoreceptors in skin

Activity in sensory nerves

Hypothalamus

Sympathetic nerves

Relax smooth muscle in cutaneous arterioles

Blood flow to skin

Heat loss by conduction & radiation

Somatic nerves

Muscle tone

Heat productionSweat Glands

Sweat production

Evaporative heat loss

Core temp.

Voluntary behaviorsRemove coversTurn on fan, etc via

Heat loss

Cerebral cortex

Conductive heat loss

Radiative heat lossConvective heat loss Central

thermoreceptors

Skeletal Muscles

Somatic nerves

~37o

CBe able to explain the physiology in each of these situationswith a detailed diagram of negative feedback responses andthe modes of heat exchange involved.

Which roofers are most appropriately dressed for the job?

Red shirts No shirts

• 1st day on the job– Increase body temp….. Delayed sweating via negative feedback

• 10th day on the job– Sweating precedes changes in core body temperature

– and sweating is increased

– And salt loss in sweat is minimized

Responses begin even before core temperature increases! Not just negative feedback, this is Feedforward (requires experience). FF is evidence of Acclimitization.

Advantage of feedforward: anticipates disruption and minimizes fluctuation from the set point.

Acclimatization & Feedforward

• Deviations from set point are minimized

• Learned (by experience)

• Anticipates changes of a physiological parameter

• Response begins before there is a change in the physiological variable

• Minimizes fluctuations

Increasecell

metabolism

Increase Body Temp.

Failure of 1. Brain function &

2. Heat loss mechanisms

Sympathetic outflow

Blood Pressure

Blood Flow to brain

Disrupted functionof neurons

Cutaneous vasodilation

Heat Stroke

Sweating

Blood volume

Excessive SweatingMassive Cutaneous Vasodilation

Treating Heat Stroke

Positive feedback

• Inherently unstable• Examples of Positive Feedback in Physiology

– Heat stroke– formation of blood clot– menstrual cycling of female sex hormone

concentrations at ovulation– generation of action potentials in nerve fibers– uterine contractions during childbirth

• Each of these examples terminate naturally (self limiting)

Homeostasis is achieved by negative feedback loops: the integrator detects deviations from set point and orchestrates responses produced by effectors that return the parameter toward the set point.

• Explain “chills” at onset of a fever

• Explain “sweat” when a fever “breaks”

• How does Tylenol reduce a fever?

To reach new,Higher set point

If setpoint is suddenly reset to a higher temperature, then actual temperature is LESS THAN the new set point, so one feels “cold” and adds clothing, curls up, and shivers. These are “Chills.”If setpoint is reset to a lower temperature or back to normal, then actual temperature is GREATER THAN the new lower set point, so one feels “hot” and removes clothing, fans, and sweats. These are “the sweats” when a fever breaks.

Central &PeripheralThermoreceptorsTylenol and other

non-steroidal anti-inflammatory drugs (NSAIDS) suppress the production of eicosanoids (IL-1, IL-6, etc) so effect of these on the set point in hypothalamus is minimized.

p. 579 Fig 16-18

Plasma Glucose Homeostasis

• Glucose metabolism

• Hormonal Control

• Disruptions of glucose homeostasis

• A Case Study

Homeostasis of Plasma Glucose Concentration

• Normal physiological range: 65-100 mg/dl• What is the set point?• Why is too much plasma glucose harmful?• Plasma glucose concentration = glucose entering the

plasma – glucose leaving the plasma• What are the mechanisms that regulate plasma

glucose concentration?• What are the components of the negative feedback

loop:– Glucose receptors?– Afferent pathway?– Integrator?– Efferent pathway(s)?– Effector organ(s)?

Phases:absorptive, post-absorptive, and fasting

Graph your daily caloric intake over a 48 hour period

6am 6am6pm 6pmNoon NoonMN MN

Cal

orie

sco

nsum

ed

6am Noon

PlasmaGlucose

?

?

Overlay absorptive and post-absorptive phases on the graph

Fig. 16.01

=sink

Abs

orpt

ive

Pha

se

Hepatic Portal System

Lipoprotein Lipase

Once inside, glucose is converted to something else, thereby maintaining a concentration gradientfor facilitated diffusion ofglucose into cells.