Adrenal Glands

Question 1

what are the 2 main functions of the adrenal glands? how are these functions accomplished? (7)

Answer 1

homeostasis and response to stress/disease via

1. maintenance of blood pressure
2. lipid, protein, and carbohydrate metabolism
3. electrolyte and fluid balance
4. sexual development and function
5. immune function
6. regulation of inflammatory response
7. fight or flight response

Question 2

contrast the adrenal cortex to the medulla

Answer 2

cortex: typical endocrine gland; secretes a variety or HORMONES (steroids, corticosteroids) into systemic circulation
medulla: modified sympathetic ganglion, secretes NEUROTRANSMITTERS (catecholamines) into systemic circulation

Question 3

list and describe the 3 layers of the adrenal cortex

Answer 3

zona glomerulosa: 15% of cortex, secretes mineralocorticoids
zona fasciculitis: 80% of cortex, secretes glucocorticoids! (the most functionally important hormones, so makes up the bulk of the cortex)
zona reticularis: 5% of cortex, secretes second steroids and glucocorticoids

Question 4

describe synthesis of steroid hormones

Answer 4

1. all synthesized from cholesterol so all have the same steroidal backbone with side chain variations
2. steroid hormones are NOT STORED! they are secreted immediately after synthesis

Question 5

describe the transport of steroid hormones

Answer 5

1. hydrophobic, so transported on plasma proteins, meaning that these hormones are predominantly bound (90% of cortisol is bound to cortisol binding globulin (CBG/transcortin) or albumin and 60% of aldosterone is bound)
2. the free portion is the only biologically active portion that can bind to intracellular (cytosolic) receptors that will result in intranuclear action

Question 6

describe how cortisol production is regulated

Answer 6

via the HPA (hypothalamic-pituitary-adrenal) axis; secretion is regulated elimination of the original stressor and also by negative feedback of cortisol on the hypothalamus

Question 7

describe the 2 cortisol secretion rhythyms

Answer 7

1. circadian: a 24 hour rhythm; diurnal animals have peak secretion in the morning, nocturnal animals have peak secretion in the evening, but this is not present in dogs and cats because dogs are always excited and cats sleep all the time
2. ultradian rhythm: a less then 24 hour rhythm with peaks every three hours; this is responsible for the pulsatile secretion of cortisol and is present in all species

Question 8

describe the effects of cortisol in the body, main overview

Answer 8

effects are tissue specific in 4 main categories:
1. metabolic
2. immune/inflammatory
3. cardiovascular
4. other (CNS, stomach, endocrine, fetal lung)

Question 9

describe the overall metabolic effects of cortisol

Answer 9

increase blood glucose via catabolic mechanisms; is why glucocorticoids got their name! includes carbohydrates, lipids, and proteins

Question 10

describe the effects of cortisol on carbohydrates and lipids

Answer 10

overall goal: increase glucose release/production and decrease glucose storage with specific effects that vary by tissue

1. skeletal muscle: decrease glucose uptake, increase glycogenolysis (release glucose from storage into bloodstream)
2. adipose tissue: decrease glucose uptake (decrease lipogenesis) and liberate stored energy via hormone sensitive lipase inducing lipolysis to increase FFA release to increase circulating lipids
3. pancreas: antagonize insulin secretion
4. liver: increase hepatic gluconeogenesis and increase glycogen synthesis (if have too much cortisol can deposit too much glycogen in liver = bad)

Question 11

describe the effects of cortisol on proteins (3)

Answer 11

1. increase protein catabolism, especially in muscle: to increase circulating amino acids and provide gluconeogenic amino acids for gluconeogenesis
2. decrease protein synthesis (can inhibit surgical site healing if patient on steroids)
3. can increase hepatic protein synthesis of lipoproteins and other proteins

Question 12

describe the immune/inflammatory effects of cortisol (5)

Answer 12

1. inhibits activation of pro-inflammatory pathways by inhibiting phospholipase-A2 and cyclooxygenase-2 (inhibit arachidonic acid pathway that results in production or proinflammatory prostaglandins; some of these prostaglandins actually protect the stomach though so if too much cortisol can equal ulcers)
2. alters gene transcription of inflammatory cytokines by decreasing pro-inflammatory and increasing anti-inflammatory cytokine production
3. decreases neutrophil migration into tissues by decreasing adhesion molecule expression and decreasing capillary permeability
4. suppresses lymphocyte proliferation and function, can even be lymphotoxic
5. stabilizes lysosomal membranes, which impairs pathogen killing by making it harder for cells like neutrophils and eosinophils to release their antimicrobial enzymes

Question 13

describe the cardiovascular effects of cortisol (general and then 2 mechanism)

Answer 13

overall role in control of blood pressure (a necessary but not sufficient control on its own) via

1. improving cardiac contractility by increasing synthesis of catecholamines and increasing tissue sensitivity to catecholamines
2. maintains vascular tone by decreasing nitric oxide (vasodilator) synthesis to ensure the vessels don’t dilate TOO much

Question 13

what is and what is observed in the stress luekogram? (4)

Answer 13

if an animal is stressed or sick, the effects of cortisol can cause this pattern which mimics an infection that is not really present
1. neutrophilia
2. lymphopenia
3. +/- monocytosis
4. +/- eosinopenia

Question 14

describe what you would expect if the body produced too much or too little cortisol

Answer 14

too much: muscle loss, pot-bellied, alopecia, PU/PD, hyperglycemia, polyphagia, hypertension, enlarged liver and signs of liver damage, chronic infections, stress leukogram

Question 15

describe the effects (2) of aldosterone in the body, include mechanism and target tissues (3)

Answer 15

overall effects (2):
1. increase blood volume by increase Na+ and water reabsorption in renal tubules
2. key regulator of plasma K+ concentration

mechanism: activating Na+/K+ pump to increase K+ excretion and increase Na+ and water reabsorption

target tissues: renal tubules, sweat and salivary glands, and GI epithelial cells

Question 16

describe what you would expect if the body produced too much or too little aldosterone

Answer 16

too much: low potassium, high Na+, increased blood volume and blood pressure

too little: high potassium (death); low sodium, low blood volume and blood pressure

Question 17

how is the adrenal medulla regulated?

Answer 17

the adrenal medulla is a modified sympathetic post-ganglion, meaning that it receives neural input from the periphery (pre-ganglionic), but it releases its neurotransmitters directly into the bloodstream instead of to a post-ganglionic fiber; it is regulated by alpha and beta receptor activation leading to second messenger system activation to release the stored catecholamines from its granules when stimulated

Question 18

compare and contrast the effects of catecholamines (epi and norepi) to the effects of direct sympathetic stimulation

Answer 18

the effects are the same (increase cardiac contractility and HR, decrease GI activity, increased blood glucose, dilated pupils, and peripheral vasoconstriction to shunt blood to the heart and brain) BUT are more widespread and last MUCH longer; sympathetic stimulation lasts milliseconds but catecholamine effects last 5-10 minutes

Question 19

compare and contrast the effects of epinephrine and norepinephrine

Answer 19

they have the same effects generally but

epinephrine:
1. is better at beta receptor stimulation, meaning it is better able to increase cardiac stimulation and therefore increase cardiac output by beta 1 adrenergic receptor stimulation and also better increase bronchodilation/relaxation via beta 2 adrenergic receptors
2. also HELLA increases tissue metabolism by raising the entire metabolic rate by 100%, meaning that there are consequences to using epi or producing too much, as the tissues won’t be able to keep up and will result in tissue damage and is why catecholamines have such a short half life (minutes); want degraded quickly to avoid nasty side effects of lingering

norepinephrine:
is better as vascular smooth muscle vasoconstriction by stimulating alpha adrenergic receptors, meaning norepi is better at increasing total peripheral resistance

Question 20

describe what you would expect if the adrenal medulla was producing too much or too little hormones

Answer 20

too much: tissue damage, increased heart rate?

too little: dead?