Hypothalamus Physio

Question 1

Control System for core temperature

Answer 1

1. Controlled variable (core temp) measured by
2. Sensor (Thermoreceptor)
3. Controller (Hypothalamus)
4. Effector (Heat loss/production) which changes
5. Controlled variable

Question 2

Difference between feedback and feedforward systems?

Answer 2

Feedback systems respond to changes already occuring while feedforward systems make adjustments prior to changes occurring.

Question 3

Where are thermoreceptors found?

Answer 3

Brain, viscera and skin

Question 4

What two questions do thermoreceptors ask?

Answer 4

• What is my current body temperature?

- What is the temperature around me?

Question 5

Characteristics of cutaneous thermoreceptors?

Answer 5

• Often bimodal (temperature and touch sensitive)
• Warm/cold sensitive
• Give info about environmental conditions

Question 6

What type of thermoreceptors predominate in skin?

Answer 6

Cold sensitive

Question 7

Purpose of thermoreceptors in viscera?

Answer 7

They sense more than core temperature, they give hypothalamus info about potential threats w/ ingested food

Question 8

Where are thermoreceptors found in the hypothalamus?

Answer 8

Pre-optic and supraoptic regions

Question 9

What type of thermoreceptors predominate in the hypothalamus?

Answer 9

Warm sensitive

Question 10

What can hypothalamus control via its connections?

Answer 10

Hormonal, autonomic, and behavioral changes (all part of thermoregulation)

Question 11

What roles does the hypothalamus play as body temp. controller?

Answer 11

• Determines the set point
• Receives info about current temps
• Decides what to do

Question 12

What happens to set point with sleep? with exercise?

Answer 12

• Decreases with sleep/increases with exercise

Question 13

What part of the hypothalamus is responsible for generating responses to heat?

Answer 13

Anterior portion

Question 14

What part of the hypothalamus is responsible for generating responses to cold?

Answer 14

Posterior portion

Question 15

Mechanisms of heat production?

Answer 15

• Autonomics
• Endocrine
• Muscular activity
• Non-shivering thermogenesis

Question 16

What do muscles do to increase heat production?

Answer 16

• Shivering, which increases motoneuron excitation

- Increase voluntary activity

Question 17

What part of the brain is responsible for shivering?

Answer 17

Dorsomedial posterior hypothalamus

Question 18

What part of the brain is responsible for voluntary activity?

Answer 18

Cortex

Question 19

What aspects make up non-shivering thermogenesis?

Answer 19

• Strong hormonal influence
• Increase food intake - increases metabolic rate
• Brown adipose tissue

Question 20

Effect of cold body temp on thyroxine?

Answer 20

• Increases thyroxin - increases metabolic rate

Question 21

How does brown adipose tissue affect heat production?

Answer 21

• Low efficiency ATP hydrolysis leads to more heat production
• Brown fat is innervated by sympathetics
• Critical in infants

Question 22

Convection

Answer 22

Transfer of heat between body and air

Question 23

Conduction

Answer 23

Transfer of heat between body and another object (chair you sit on)

Question 24

Radiation

Answer 24

Transfer of heat between body and walls

Question 25

How does blood flow affect body temp?

Answer 25

Increasing blood sent to skin - heat loss - flushing

Question 26

What is sweating controlled by?

Answer 26

Ach binding a muscarinic R (via sympathetic cholinergics)

Question 27

Describe general process of sweating?

Answer 27

1. Filtration of serum, including ions | 2. As fluid travels up to skin surface, water and Na+ are reabsorbed in the duct of gland back to blood

Question 28

Low sweat flow rate?

Answer 28

- Sweat is concentrated - Little water (mostly reabsorbed) - High sodium (couldn't follow water that was reabsorbed)

Question 29

High sweat flow rate?

Answer 29

- Sweat is dilute - Lots of water (couldn't be reabsorbed in time) - Little sodium (effect of Aldosterone)

Question 30

What is fever defined as?

Answer 30

Controlled increase in body temperature d/t set point being increased (orders from the hypothalamus)

Question 31

Pathway of fever

Answer 31

- Secretion of endotoxins - stimulation of PGE 2 - increases hypothalamic set point for temp

Question 32

Why does shivering occur in fever?

Answer 32

Body is trying to generate heat