Lecture 4 Flashcards
What 3 things have to happen stimultaneously in order for micturition (urination) to occur ?
- Detrusor muscles must contract
- Internal urethral sphincter must open (autonomic NS)
-
External urethral sphincter must relax to open (voluntary)
- At same level of urogenital diaphragm, which helps external u.s. stay closed
What are the steps of Micturition ?
- 200 ml of urine in bladder
- Distension sensed by stretch receptors in walls
- Triggers visceral reflex arc :
- Impulses travel via affarent nerve fibers to sacral region of spinal cord & efferent to bladder via Parasympathetic pelvic nerves - Detrusor muscle contracts + pulls internal sphincter open→ Urine enters through internal sphincter into upper part of urethra
- Affarent signals to brain ; one feels urge to pee / void
- External sphincter opens under voluntary control (affarent impulses decrease somatic efferent motor nerve activity that usu keep it closed)
- External sphincter relaxes to empty bladder
- only 10 ml of urine will remain - Reflex subsides in 1 min (occurs again as urine accumulates to keep reminding you, urge to void becomes greater & greater)
- Micturition usu occurs before urine volume exceeds 400 ml
Renal is ___________________ nerves but micturition is ___________________ nerves
sympa, parasympathetic
At age 2/3, reflexive urination can be overridden by matured higher-brain centers in the pons :
Bladder fullness –> Stretch receptors –> Affarent impulses to pons & higher-brain centers
- Pontine storage center inhibits micturition (usu activated by lower bladder voolumes)
- Pontine micturition center promotes micturition reflex
PMC promotes micturition by acting on all 3 spinal efferent reflexes :
1. ↑ paralympic activity
2. ↓ sympa activity
– detrusor muscles contract to open internal urethral sphincter –
- ↓ somatic motor activity
– external urethral sphincter opens –
PMC inhibits micturition by acting on all 3 spinal efferent reflexes :
1. ↓ paralympic activity
2. ↑ sympa activity
3. ↑ somatic motor nerve activity
What is urinary incontinence ?
Inability to control micturition voluntarily
- Weakened pelvic floor muscles
- Pregnancy (↑ pressure, decreased bladder space from bigger uterus carrying baby)
- NS problems
What is stress incontinence ?
Pee your pants when you cough, sneeze or laugh
- Sudden ↑ in intra-abdominal P pushes down on bladder, causing external urethral sphincter supported by urogenital diaphragm to open if weak
What is renal failure ?
Not enough functioning nephrons –> Causing reduced / stopped filtrate formation
- Nitrogenous wastes accumulate, blood becomes acidic –> diarrhea, vomiting, edema, labored breathing, cardiac irregularities (acid-base imbalances), convulsions, coma, death
- May present with anemia due to lack of EPO
Dialysis needed once apparent symptoms + renal functioning below 25 %
Causes of Renal Failure
- repeated damaging kidney infections
- phys damage
- prolonged pressure on skel muscles (creatinine clogs up filtration membranes)
- inadequate blood flow to kidney tubules (BP too low for NFP)
Hemodyalysis
can be done @ home or clinic, several x per week for 3 - 5 hr / session
- Blood coomes out of body, filtered outside, returned w/ correct osmolarity
- Allows blood to equilibrate w/ surrounding fluid / right conc of solutes
Peritoneal Dialysis
Works by using blood vessels / cap beds of peritoneal membrane of abdominal cavity
does NOT require weekly hospital visits, can be done more frequently
- Dialysate (composed of mostly salts, sugar) infused into peritoneal cavity through catheter to encourage filtration through peritoneum
- Extra fluid + wastes drawn from blood into dialysate, which is then removed
- Blood equilibrates itself
2 types of peritoneal dialysis
-
Continuous Ambulatory Peritoneal Dialysis (CAPD) : usu 4-5x / day
- Dialysate stays in peritoneal cavity for 4-5 h before drained back into bag, thrown away -
Continuous Cycling Peritoneal Dialysis (CCPD) : usu done @ home w/ cycler machine
- Similar to CAPD, except umber of cycles / exchanges occur
- Each cycle lasts 1-2 h
- Exchanges done during the night while patient sleeps
What are the body’s fluid compartments ?
a) Intracellular Fluid Compartment (ICF) –> within cells, 60 %
b) Extracellular Fluid Compartment (ECF) –> outside cells, 40 %
- Plasma – fluid portion of blood [ all we can monitor ]
- Interstitial Fluid (IF) – fluid in-between tissue cells
- other : lymphatic fluid, cerebrospinal fluid, eye fluid, GI fluids, etc
Why do electrolytes have greater osmotic power than non-electrolytes ?
Electrolytes dissociate into their component ions when dissolved in water, so they will be contributing more solute particles into the solution & consequently have a greater effect on osmotic P / mass vs compounds that do NOT dissociate in water (eg. glucose is a non-electrolyte), since those have covalent bonds that prevent that & don’t possess e- charges to conduct a current
Chief cations & anions
ECF
Cation – Sodium, Na
Anion – Chloride, Cl
ICF
Cation – Potassium, K
Anion – Phosphate, PO
Na & K opposite, ATP-dependent Na/K pumps keep intracellular [Na+] low (pump Na out) & maintain high intracellular [K+] (allow it to come in)
Changes in ______________________________ in blood plasma will affect intracellular fluid _____________
solute concentrations, volumes
