Chapter 14 Flashcards
What is homeostasis
Maintenance of constant internal environment
What does homeostasis do
Keep set-point stable within narrow limits in body, irrespective of changes in external environment
What are some examples of factors that should be maintained by homeostasis
- temperature
- water potential
- glucose concentration
Why should factors be maintained by homeostasis
So that internal environment can be stable and function optimally
How do controls systems often work
By using “negative feedback mechanism”
What are the components of “negative feedback mechanism”
- stimulus
- receptor
- control centre
- effector
- response
To restore norm or set point
What is the meaning of stimulus
Refers to internal or external change in factor away from norm/set-point
What is the meaning of receptor
Cells / tissue / organs which detect the stimulus
What is the meaning of coordinating centre / control centre
- Consists of tissue which receives and processes messages, (in the form of hormones or nerve impulses), from the receptors, and determines the appropriate response
- only sends a message to an effector if stimulus is strong enough
What is the meaning of effector
Tissues / organs which receive messages from coordinating centre and carry out a corrective reaction
What is the meaning of response
- the reaction carried out by the effectors
- in negative feedback the response counteracts the stimulus to return to set-point/norm
What does negative feedback mechanism do
- it continuously monitors the factor affecting internal environment
- which results in many “corrective actions”
- factor thus fluctuates around the norm/set point
What is excretion
The removal of unwanted products of metabolism (toxic, poisonous products that will cause damage to tissues)
What are the main excretory products and where are they excreted from
- carbon dioxide —> excreted via bloodstream and lungs
- urea (nitrogenous waste) —> excreted via kidneys
- creatinine (nitrogenous waste) —> excreted via kidneys
- Uric acid (nitrogenous waste) —> excreted via kidneys
What is urea and where is it formed
- main nitrogenous excretory product
- formed from excess amino acids in liver cells
How is urea formed
- Deamination
- amine group and H atom is removed from amino acid
- this produces ammonia, NH3 (which is toxic if allowed to accumulate)
- Urea cycle
- NH3 + CO2 —> urea —> (excreted via kidneys)
- Keto acid remains, can be respired or converted to glucose/glycogen/fat
What are the blood vessels in the kidney
- renal artery
- renal vein
What are the excretory tubes in the kidney
- ureter (urine out from kidney into urinary bladder)
- urethra (urine out from urinary bladder)
What are the layers of the kidney
- capsule (tough, protective layer)
- cortex
- medulla
- pelvis
What is present in the cortex and medulla
nephrons —> tiny tubes in the kidney in cortex and medulla
What is the structure of a nephron
- Bowman’s capsule (cortex)
- Proximal convoluted tubule (cortex)
- Loop of Henle (medulla)
- descending limb
- ascending limb
- Distal convoluted tubule (cortex)
- Collecting duct (medulla)
- connected to ureter at pelvis
How does the renal artery branch out in the nephron
- Afferent arteriole
- Glomerulus (tangle of capillaries in the ‘cup’ of bowman’s capsule)
- Efferent arteriole
