Homeostasis

What is homeostasis?

The maintenence of a stable internal environment despite internal or external changes

Why is homeostasis important?

• Ensures optimum condition fro enzyme activity

• Maintains metabolic reactions

• Prevents cell damage

What four variables are controlled by homeostasis?

• Blood glucose concentration

• Blood water potential

• Blood pH

• Body temperature

Describe negative feedback.

A mechanism that reverses any change away from the normal level, returning conditions back to normal

What are the 3 components of negative feedback?

1. Receptor

2. Coordination centre

3. Effector

Why must body temperature be controlled in humans?

Enzymes work best at 37°C.

What happens if body temperature becomes too high?

If the body temp is too high the active site of the enzyme denature leading to metabolic reactions to either slow down or stop completely.

What happens if body temperature becomes too low?

If the body temp is too low the enzymes won't have enough energy to work causing the metabolic reactions to either slow down.

Which part of the brain controls body temperature?

The hypothalamus

What acts as receptors for temperature?

Thermoreceptors in the skin and hypothalamus

What apps to the skin arterioles when you're too hot?

Vasodilation

What is vasodilation?

Smooth muscles relax causing arterioles to widen so there is more blood flow near the skin surface increasing heat loss by radiation.

What happens to sweat glands when you're too hot?

They secrete more sweat

How does sweating cool the body?

Sweat evaporates, taking latent heat from the skin

What happens to hair when you're hot?

The hair erector muscles relax causing hair to lie flat reducing the insulation air layer

What happens to skin arterioles when you're cold?

Vasoconstriction

What is vasoconstriction?

Smooth muscles(sphinter muscles) contract, narrowing arterioles and causing less blood to flow to the skin surface so less heat is loss through radiation.

Wha happens to the sweat glands when you're cold?

Sweating stops

What happens to hairs when you're cold?

The hair erector muscles contract casuing hair to stand upright and trap an insulating layer of air

What is shivering?

Involuntary muscle contractions that generate heat through respiration.

Name four functions of the liver.

1. Deamination

2. Detoxification

3. Glycogenesis/glycogenolysis

4. Producing bile

What is deamination?

Removal of excess amino group from excess amino acids

Why can't amino acids be stored?

The body has no storage form for animal acids

What are products of deamination?

• Ammonia

• Keto acid

Why is ammonia dangerous?

It is highly toxic

What happens to the keto acid after deamination?

It is used in respiration where it is then converted into glycogen and fat.

What happens to ammonia in the liver?

It is converted into urea

What I the name of the process that converts ammonia into urea?

The ornithine cycle (urea cycle)

Why is urea safer than ammonia?

It is much less toxic

What is detoxification?

Breakdown of harmful substances into les harmful compounds.

Where is urea transported?

In the blood to the kidneys

Give examples of substances detoxified by the liver.

• Alcohol

• Drugs

• Hydrogen Peroxide

Which enzyme breaks down hydrogen peroxide?

Catalase

Why must hydrogen peroxide be broken down?

It is toxic and damages cells

What are the main functions of the kidneys?

• Removes urea

• Regulate water potential

• Regulate ion concentrations

Parts of the nephron

• Bowman’s capsule

• Proximal Convoluted Tubule (PCT)

• Loop of Henle

• Distal Convoluted Tubule (DCT)

• Collecting Duct

Name the blood vessels associated with the nephron

• Afferent arteriole

• Glomerulus

• Efferent arteriole

• Peritubular capillaries

• Vasa recta

Gross structure of the mammalian kidney

• Cortex

• Medulla

• Renal pelvis

• Ureter

• Renal artery

• Renal vein

What is the function of the afferent arteriole?

Carriers blood into the glomerulus

What is the function of the efferent arteriole

Carries blood away from the glomerulus and forms the capillary network around the nephron

Where does the ultrafiltration occur?

At the glomerulus and Bowman’s capsule

What causes ultrafiltration?

High Hydrostatic Pressure in glomerulus forces small molecules out of the blood and into Bowman’s capsule

Why is Hydrostatic Pressure high in the glomerulus?

The afferent arteriole has a larger diameter than the efferent arteriole, creating high pressure in the glomerulus

What are the three layers of the filtration barrier?

• Fenestrated endothelium of the capillary

• Basement membrane

• Padocytes with filtration slits