Fundamentals Of Physiology & Pharmacology Flashcards
Types of homeostatic control mechanisms (3)
Negative feedback (reflex arc) - change in variable causes response that moves the variable back to set-point (normalisation)
Feed-forward:
- anticipation of a change brings about the response to that change before it is detected by negative feedback sensors
- eg. Pavlovs dogs / fight or flight
Positive feedback:
- change in variable triggers a response that causes further change in that variable (amplification)
What neurotransmitter is released from the nerves in the sympathetic and parasympathetic nervous systems?
Sympathetic:
Noradrenaline
Parasympathetic:
Acetylcholine
Hormones of the hypothalamus
Releasing hormones:
GHRH, CRH, TRH, GnRH
Inhibitory hormones:
Somatostatin, dopamine
Hormones of the pituitary gland
Anterior pituitary: GH Prolactin FSH LH TSH ACTH
Posterior pituitary:
Oxytocin
ADH
Types of hormones
& examples from hypothalamus & pituitary
Peptides:
ADH
oxytocin
Polypeptides:
Growth hormone
(Insulin from pancreas)
Glycoproteins:
Everything else
What hormones does Tyrosine make?
Adrenaline
Thyroxine (T3&T4)
What hormones does cholesterol make?
Via the precursor hormone pregnisolone
All steroid hormones
(Eg. Sex hormones, adrenal cortex hormones)
In ovaries:
- progesterone
- estrogens
In testes:
- androgens (eg. Testosterone)
Adrenal cortex:
- glucocorticoids (eg. Cortisol)
- mineralocortocoids (eg. Aldosterone)
Hormone receptors
Peptides/proteins/glycoprotein:
- receptor located on plasma membrane
- second messengers to change enzymic activity
- rapid & transient response
Steroids/thyroid hormones:
- receptor located intracellularly (cytoplasm or nucleus)
- alter gene expression
- slow & prolonged response
Example of positive feedback
Parturition
When pregnant estrogen/progesterone balance is altered
Increases excitability of uterus
Uterine contractions
Fetus presses on cervix
Signals to hypothalamus
Oxytocin secretion
^^^back up to inc excitability of uterus
Cycle repeats until baby born
Total body water
(% of body weight)
(60% is water)
Intracellular space (40%)
Interstitial space (15%)
Plasma space (5%)
Osmolarity vs Osmolality
Osmolarity:
1 osmole per litre
Osmolality:
1 osmole per kg
Osmole = 1 mole
(6.022x10^23 entities)
Osmotic pressure
Cystalloid:
Due to small diffusible ions
(Eg. Na+, Cl- and K+ in body fluids)
Oncotic pressure:
Little protein in interstitial fluid (but there is in plasma) so exert an oncotic pressure
Ionic composition
mmol/l
Plasma: [Na+] = 140 [K+] = 4 [Ca2+] = 2 Anions include = Cl- (110) & Bicarbonate (24)
Intracellular: [Na+] = 10 [K+] = 120 [Ca2+] = 0.0001 Anions include = AA’s, Cl-, proteins
Plasma proteins
Albumin (48g/litre)
- plasma oncotic pressure
- transport, buffering of pH
Alpha, beta, gamma globulins (0.7-13g/litre each)
- haemostatis, transport, immune system
Fibrinogen (3g/litre)
- haemostasis
Haematopoetic stem cells
Erythrocytes
Leukocytes:
- Granulocytes (-> neutrophils, eosinophils, basophils)
- monocytes (macrophages)
- lymphocytes
Thrombocytes
Erythrocytes
120 day life
RBC = male 5.5, female 4.8
(x 10^12 / litre)
Contain haemoglobin
Male 160g, female 140g / litre blood
(Conc)
Leucocytes
WBC = 4-11 x 10^9 / litre
Lymphocytes (20-40%)
- immune systems
Monocytes (2-8%)
- migrate to tissues and form macrophages
Granulocytes
- neutrophils (50-70%) = chemotactic, phag
- eosinophils (1-4%) = phagocytosis
- basophils (0.5%) = release histamine
Platelets
Fragments of megakaryocytes
150-400 x 10^9 / litre
Central role in haemostasis
Electrical charge in a quiescent state of cell
Inner membrane is negatively charged with respect to the outside
Voltage at the membrane
Voltage is a measure of the work done in separating charges across the membrane
Conc gradient:
[C] out / [C] in (For +ve ions, opposite for -ve)
If know conc grad, membrane voltage due to an ion can be found from the Nernst equation:
E = 58 (mV) x log [C] out / [C] in
(For +ve)
Membrane potential
Resting:
-70mV
E(K) = -90mV
E(Na) = +50mV
(Needs to be this to stop K+ leaving and Na+ entering)
Membrane more permeable to K than Na
Driving force on ion = Vm - Eeq (at rest)
At rest:
+20mV of K+ out
-120mV of Na+ in
Permeability of membrane to K+ is 50 times greater than Na+
(Can use Goldman Hodgkin Katz eqn)
Anisotropic conduction
Electrical impulses travel easier along fibres than across them
Cholinergic receptor in ANS
Nicotinic receptors:
(Non-selective cation channel)
- muscle receptor N1
- ganglionic receptor N2
Muscarinic receptors: (G-protein coupled) (5 sub-types) - M2 = cardiac, lowers cAMP - M3 = smooth muscle/glandular, inc IP3 & DAG
Adrenergic receptors in ANS
Alpha:
2 subtypes, each has 3 sub-sub types
- a1 = activates Gq to stimulate IP3/Ca2+ and DAG, raises cellular Ca2+ (causes contraction)
- a2 = activate Gi to inhibit adenylate cyclase and lower cellular cAMP, located pre-synaptically, lowers release of noradrenaline (autoreceptor) (inhibits NA release)
Beta:
3 subtypes, all activate Gs to activate adenylate cyclase and inc cAMP
- b1 = main cardiac subtype (inc rate of contraction)
- b2 = main vascular and airways subtype (smooth muscle relaxation)
- b3 = found in adipose, important in bladder
