 Where does the filtration of water and dissolved solutes occur in the kidney?  Why is water able to be diffused out of the filtrate flowing through the PCT with no addition of energy?  What are the 3 stages of urine formation? DO NOW 4/21/15

UPCOMING DATES  Tuesday, 4/7: Blood Quiz Corrections due  Thursday, 4/9: Blood, Immune/Lymphatic BIG Quiz  Monday/Tuesday (PM), 4/13-14: Big Quiz Corrections  Friday, 4/17: Digestive Quiz  Thursday, 4/23: Digestive Project due  Monday, 4/27: Urinary Quiz; Urinary Project due  Friday, 5/1: Urinary & Reproductive Test  Thursday, 5/7: Semester 2 Final Exam

HORMONAL CONTROL OF URINE

 By the end of today’s class, I will be able to …  Describe how the kidney retains a high concentration of solutes in the renal medulla  Describe how the urinary system is regulated by hormones  Describe urine storage and the process of micturition OBJECTIVE

 Renal cortex:  Renal corpuscle  Renal tubules (PCT, DCT)  Renal medulla  Parts of the nephron loop  Collecting duct THE RENAL CORTEX VS. MEDULLA

 The reabsorption we discussed occurred in the PCT and DCT  The nephron loop does not have these capabilities because it is too thin to hold sodium pumps RENAL CORTEX VS MEDULLA

 The descending limb cannot have active transport  For this reason only limited water will be diffused out of the filtrate at this point THE DESCENDING LIMB OF THE NEPHRON LOOP

 Both the ascending limb of the nephron loop and the DCT do not allow water to pass  The DCT does have sodium pumps and actively pumps sodium into the space around the DCT THE ASCENDING LIMBS If water cannot leave the ascending parts of the nephron and salt can, what will the area around the nephron loop be like in terms of salt and solute concentration?

 Because the blood and filtrate pathways travel down the renal medulla and then back up on a parallel pathway, the amount of solute in the kidney is kept very high. THE COUNTERCURRENT MECHANISM

 As the filtrate flows down the collecting duct through the renal medulla, water can again be reabsorbed.  The result is that urine is extremely concentrated when leaving the kidney. THE COLLECTING DUCT

 What is different about the structure and function of the nephron loop compared to the PCT and DCT? QUICK CHECK

 Why is it very important that the renal medulla have a very high concentration of solute? QUICK CHECK

 By the time the filtrate reaches the DCT, about 90% of sodium and chloride and 80% of water which originally entered the glomerular corpuscle have been reabsorbed.  Reabsorption that occurs in the DCT is then regulated by hormones to meet the needs of the body. HORMONES

 Aldosterone  Atrial Natriuretic Peptide  Antidiuretic Hormone 3 KEY HORMONES

 Produced in the adrenal cortex when blood sodium levels are low  Aldosterone causes the DCT to absorb more sodium and potassium  Water is also absorbed which increases the amount of water in blood  This high volume of water in the blood increases blood pressure ALDOSTERONE

 ANP is released in response to high volumes of blood  ANP inhibits sodium absorption and therefore decreases the amount of water absorbed back into the blood ATRIAL NATRIURETIC PEPTIDE

 ADH is secreted by the pituitary gland  ADH is secreted when the concentration of solutes in the blood is too high  When we are dehydrated, this concentration increases  ADH allows water to be reabsorbed at a higher rate in the collecting ducts by opening more channels for water to diffuse. ANTIDIURETIC HORMONE

 Does hormonal regulation occur in the PCT or DCT? QUICK CHECK

 If a person has low sodium levels in their blood, which hormone will be secreted? QUICK CHECK

 If the level of solutes in the blood is too high, which hormone will be secreted?

 If there is too high of a volume of blood flowing through the veins, which hormone is secreted?

URINE STORAGE AND EXCRETION

URINE PRODUCTION AND TRANSPORT  Kidneys produce urine constantly, but only release it periodically.  Ureters transport urine from the kidney to the urinary bladder for storage

THE URINARY BLADDER

 Hollow, muscular organ  Lies between the pelvic floor and the peritoneum

THE URINARY BLADDER  The wall (detrusor) is made of smooth muscle  2 openings for ureters and 1 for urethra

URETHRA  Thin tube connecting bladder to outside  2 sphincters help contain urine in the bladder:  Internal Urethral Sphincter  External Urethral Sphincter

The primary difference between male and female urethras is that the male’s contains spongy urethra

QUICK CHECK  How does urine get from the kidneys to the bladder?  What is the bladder’s purpose?  What structure transports urine to the outside of the body?  What is the wall of the bladder called?

TURN AND TALK The respiratory system and the urinary system both rid the body of waste (carbon dioxide and urine, respectively). Does the respiratory system have a structure like the bladder? Why or why not?

URINE EXCRETION

MICTURITION  The release of urine from the bladder is called micturition.  Occurs by contracting the detrusor and relaxing both sphincters (internal and external)

INTERNAL AND EXTERNAL SPHINCTERS  The internal sphincter is controlled by the autonomic nervous system and will relax subconsciously  Will the external sphincter be controlled by the same pathway?

STEPS TO MICTURITION 1.The bladder stretches as it fills and sends signals to the sacral portion of the spinal cord.

STEPS TO MICTURITION 1.The bladder stretches as it fills and sends signals to the sacral portion of the spinal cord. 2.The sacral cord neurons “tell” the detrusor to contract and the internal sphincter to relax.

STEPS TO MICTURITION 1.The bladder stretches as it fills and sends signals to the sacral portion of the spinal cord. 2.The sacral cord neurons “tell” the detrusor to contract and the internal sphincter to relax. 3.The brain receives the sensory message that the bladder is full from the spinal cord.

STEPS TO MICTURITION 1.The bladder stretches as it fills and sends signals to the sacral portion of the spinal cord. 2.The sacral cord neurons “tell” the detrusor to contract and the internal sphincter to relax. 3.The brain receives the sensory message that the bladder is full from the spinal cord. 4.If the time is optimal for urination, the brain sends a signal to the external sphincter to relax and then detrusor contracts.

QUICK CHECK: PUT THESE IN ORDER 1.The spinal cord relays the message that the bladder is full to the brain. 2.The brain tells the external sphincter to relax 3.The spinal cord tells the internal sphincter to relax 4.The external sphincter relaxes and the detrusor contracts 5.The bladder stretches and relays that signal to the spinal cord 6.The detrusor contracts and the internal sphincter relaxes

SO, THIS IS A THING…

IT’S STORY TIME!  Write a story for kids about potty training.  You can choose any format you’d like but it has to inform them about:  Kidneys, ureters, urethra, bladder, and sphincters  How urine is created in the kidneys  The process of micturition (How your body decides its time to use the restroom)