CH6 Homeostasis and regulation

Question 1

what is homeostasis?

Answer 1

homeostasis is when Homeostatic mechanisms produce a
relatively stable internal environment by maintaining key variables within narrow limits

Question 2

which systems control homeostasis?

Answer 2

the nervous system (by sending electrical messages through the brain, spinal chord and nerves) and the endocrine system (by sending chemical messages through the hormonal system)

Question 3

what is the nervous system?

Answer 3

• The nervous system uses neurons to send quick, immediate messages.
• The message begins in the sensory cell, travels through the neurons to the Control Center (central nervous system), which then processes and responds to the signal in a matter of seconds.
• Electrical messages

Question 4

what is the endocrine system?

Answer 4

• The endocrine system uses chemical signals instead of electrical signals to send messages.
• The messages are slower, as they rely on the bloodstream to deliver the chemicals to a specific target cell.
• The messaging chemicals are called HORMONES.
• Hormones are often produced in specialised Endocrine glands around the body.

Question 5

what are the two types of hormones?

Answer 5

Water Soluble Hormones and Lipid-soluble hormones

Question 6

what are water soluble hormones?

Answer 6

Polypeptides (which are simple proteins and hydrophilic)
Polypeptides require facilitated diffusion to enter a cell.

Their target proteins are therefore outside the cell, embedded in the cell membrane.

Question 7

what are lipid soluble hormones?

Answer 7

Steroids (which are oils or fats and are Hydrophobic)
Steroids can diffuse naturally through the cell membrane. Their target proteins can therefore be on the inside of the cell.

Question 8

what is the negative feedback system?

Answer 8

A negative feedback mechanism is taking away a stimulus.

Question 9

what is stimulus?

Answer 9

a change in internal environment

Question 10

what is a sensor?

Answer 10

a nerve or receptor that detects the change

Question 11

what is a control center?

Answer 11

an organ that processes and controls the response to the stimulus

Question 12

how does blood sugar increase

Answer 12

we eat a meal to increase blood glucose levels.

Question 13

how do we decrease blood sugar

Answer 13

• pancreas releases insulin into the blood
• insulin stimulates the liver cells to convert glucose into glycogen, stored for later use

Question 14

what is the body’s response to an increase in glucose levels?

Answer 14

• Glucose receptors in the pancreas detect the increase
• Pancreas releases insulin into the bloodstream
• Insulin stimulates the liver cells to convert glucose into glycogen
• Blood glucose levels return to normal and the pancreas stops releasing insulin

Question 15

what is the bodys response to a decrease in glucose levels?

Answer 15

• Glucose receptors on the pancreas detect the decrease
• Pancreas releases glucagon into the blood
• The glucagon stimulates the liver cells to convert glycogen into glucose
• When blood glucose levels return to normal , the pancreas stops releasing glucagon.

Question 16

how does water exit the body?

Answer 16

1. sweating
2. breathing
3. urination
4. defecation

Question 17

how does water enter the body?

Answer 17

1. eating
2. drinking
3. metabolic water ( as a waste product from cellular respiration)

Question 18

what is ADH?

Answer 18

ADH stimulates the production of aquaporins in the wall of the collecting tubule.

this allows water to move out of the collecting tubule and be reabsorbed by the surrounding blood vessels

Question 19

what are aquaporins?

Answer 19

channel proteins specific to water molecules

Question 20

how is water balance maintained?

Answer 20

• the thirst centre in the hypothalamus
• ADH - a hormone secreted by the posterior pituitary - gland locted at the base of your brain

Question 21

how does water regulation work?

Answer 21

• osmoreceptors in the hypothalamus detect the concentration of particles dissolved in your plasma (osmality)
• if there is an increase in osmality the thirst centre is activated, prompting you to drink more water, and ADH is reeased (which decreases the water lost in urine)
• these steps can also be triggered by the production of blood pressure

Question 22

regulating water balance

Answer 22

• we cannot regulate our most water lost from our body, but we can control water concentration
• reabsoption of water int he kidneys is controlled by a peptide hormone called ADH.

anti-diuretic hormone

Question 23

what is high osmality?

Answer 23

high concentration, less water in plasma

Question 24

what is low osmality?

Answer 24

low concentration, more water in plasma