Endocrine system

Question 1

Function of the endocrine system and terminology

Answer 1

Functions to regulate and coordinate body activities
Terminology
-Tropin- to make something happen or stimulate an effect
The endocrine system is one of 2 control systems of the body – the other is the nervous system.
It is the slower of the two systems

Question 2

Endocrine glands functions

Answer 2

The endocrine system is a general term referring to the group of ductless glands which
Help to maintain homeostasis in the body.
They can also drive change e.g. growth or lactation.
They do this by releasing hormones, these are communication and control molecules
Endocrine glands synthesize, store and then secrete hormones directly into the bloodstream

Question 3

Hormones are

Answer 3

Are chemical messengers that are secreted in response to a stimulus
Have specific receptors at their target organ
The target organ is distant from the endocrine gland
The receptor will respond only to the specific hormone to which it is sensitive
Hormones are controlled by feedback loops that can be negative (usually) or positive

Question 4

Hormone secretion controlled by

Answer 4

Hormone secretion is mainly controlled by negative feedback
Sensors detect when levels of the hormone rise above optimum levels
Signal is sent to stop or decrease production
When the levels drop below optimum, a signal is sent to increase production
Secretion may also be controlled by:
Positive feedback e.g. nursing stimulates prolactin release which stimulates more milk production
Nervous stimulation e.g. the sympathetic NS causes release of adrenalin (epinephrine) during the fight or flight response
Cells that produce locally acting hormones are called paracrine glands
Important in organ and tissue development

Question 5

Characteristics of they hypothalamus

Answer 5

Part of the diencephalon of the brain
Links the cerebrum to the endocrine system i.e conscious to hormones
Regulates appetite, body temperature, and sleep-wake cycles

Question 6

Pituitary is

Answer 6

An endocrine gland attached to the base of the hypothalamus by a thin stalk of nerves and blood vessels- infundibulum
A major control gland of the endocrine system
Has anterior and posterior parts

Question 7

Relationship b/w hypothalamus and pituitary

Answer 7

Blood vessels form a portal system link between the anterior pituitary and the hypothalamus
Hypothalamus receives information from the CNS
Then secretes hormones into its portal system to regulate pituitary hormone secretion
A nervous connection between the posterior pituitary and hypothalamus allows direct transport of oxytocin and antidiuretic (ADH)
Synthesized in the hypothalamus
Stored in the pituitary
Released on stimulation by nerve impulses from the hypothalamus

Question 8

Characteristics of pituitary gland

Answer 8

Controls other endocrine glands
Size of small pea or bean
Attached to hypothalamus by a stalk (infundibulum) and seated in a pocket in the sphenoid bone of the skull
Two parts:
anterior is normal glandular tissue,
posterior is derived from nervous tissue

Question 9

Anterior pituitary does what

Answer 9

Produces 7 known hormones as directed by the hypothalamus and feedback from target organs and tissues
Release of each hormone is controlled by the appropriate releasing hormone from the hypothalamus

Question 10

Growth hormone is

Answer 10

Aka somatotropin or somatotropic hormone
Promotes body growth in young animals, especially bone and muscle.
Protein building
Makes energy available from reserves (stored fat and carbs) → promotes HYPERglycemia

Question 11

Prolactin is

Answer 11

Helps trigger and maintain lactation
Lactation and prolactin secretion continues as long as physical stimulation of nursing or milking continues
Is a positive feedback loop
Animal ‘dries up’ if stimulation stops e.g. weaning

Question 12

TSh is

Answer 12

Thyroid-Stimulating Hormone (TSH or thyrotropin)
Stimulates thyroid gland to produce thyroid hormones
Increased levels if thyroid levels drop
Regulated through the hypothalamus, which will release TSH – releasing hormone to cause TSH to be released from the pituitary
Negative feedback loop regulates

Question 13

ACTH is

Answer 13

Adrenocorticotropic Hormone (ACTH)
Stimulates the cortex of the adrenal gland
Controlled by negative feedback
During stress, the CNS can send signals through the hypothalamus
What does the hypothalamus release?
ACTH- releasing hormone- stimulates pituitary release ACTH
ACTH→ causes release of cortisol and other stress (steroid) hormones from adrenal cortex
CRH= corticotropin releasing hormone. Same as ACTH-RH

Question 14

FSH is

Answer 14

Follicle-Stimulating Hormone (FSH)
In females stimulates growth and development of ovarian follicles
Follicles develop and oocyte (egge) matures
Follicular cells to release estrogen
Promotes the physical and behavioural changes of estrus
In male animals, FSH stimulates growth and development of spermatogenesis- growth and development of sperm
(Estrogen production)

Question 15

LH is

Answer 15

Luteinizing Hormone (LH)
This is the ripening hormone for the follicle (FSH stimulates follicular development)
LH causes the final rupture and release of the egg from the follicle
Males
Called interstitial cell-stimulating hormone (ICSH)
Encourages production of testosterone
FSH and LH are also called gonadotropins because they stimulate growth and development of the glands

Question 16

MSH is

Answer 16

Melanocyte-Stimulating Hormone (MSH)
Uncertain role in most animals at normal levels
Can cause skin to darken at high levels
In reptiles, fish, and amphibians, can cause rapid changes in colour

Question 17

Posterior pituitary function

Answer 17

Does not PRODUCE any hormones
Stores and releases 2 hormones produced by the hypothalamus, as directed by the hypothalamus
Hormones get to the posterior pituitary by transport down the nerve fibers
ADH
Oxytocin

Question 18

ADH is and function

Answer 18

Antidiuretic Hormone (ADH)
AKA= vasopressin
Helps prevent diuresis
Helps conserve water
In kidneys
Increases reabsorption of water from the urine
Urine becomes concentrated, darker, and stronger smelling,
ADH secreted id animals becomes dehydrated and hypothalamus sense hemoconcentration
What is hemoconcentration
Increased RBC concentration
Affects are partially blocked by caffeine and alcohol
What would happen if ADH was absent
PU/PD

Question 19

Oxytocin is and functions

Answer 19

Causes contractions of the uterine muscles at breeding and parturition
At breeding, this helps move sperm up to the oviduct
At parturition, this helps deliver the fetus and placenta
Bonding(behavioural effects) in humans. Used to promote fostering in animals.
Causes milk let down in lactating females. Moves milk from the production and storage part of the mammary gland to the lower part for nursing
Release is stimulated by the sensory stimulation of nursing, intromission, the fetus or sometimes by association (cows)
Often given as a drug to promote delivery of fetus, placenta or milk.

Question 20

Anatomy of the thyroid gland

Answer 20

Two lobes, sometimes connected, on either side and just below larynx
The thyroid glands of several species. The inset cross section shows the ventral connection of the thyroid glands in the pig
Composed of thousands of tiny follicles
Spheres of cells around a central area containing the thyroid hormone precursor (called colloid)

Question 21

What hormones do they thyroid produce

Answer 21

Produces 2 groups of hormones
Thyroid hormone group T3, T4
Calcitonin

Question 22

Thyroid hormones are

Answer 22

Produced in two forms: T3 and T4
Named for how many iodine atoms they have per molecule of hormone.
Produced in response to TSH
T4 is also called thyroxine, main form produced by gland
Usually measured when testing for disease
T3 is the more physiologically active form,
Produced from T4 in tissues

Question 23

Calorigenic effect of thyroid hormone

Answer 23

Helps heat the body by increasing metabolic rate and what production
Production is increased with exposure to cold
Production is decreased by emotional or physical stress (can make animal susceptible to cold or disease)
Effect on Protein, Carbohydrate, and Lipid Metabolism
Increases protein anabolism in the presence of adequate nutrition
Stimulates catabolism during nutritional deficiencies or high thyroid levels
Encourages lipid catabolism
Tends to cause hyperglycemia
Cardiovascular:
Increases heart rate

Question 24

Effects of thyroid hormone on growth

Answer 24

Developmental: Effect on Young, Growing Animals
Necessary for young, growing animals
Helps maturation of CNS and growth and development of muscles and bones

Question 25

Calcitonin is

Answer 25

Produced by C-cells found between the thyroid follicles Functions to keep blood calcium levels from getting too high Stimulates storage of excess blood calcium in the bones- this drops blood calcium levels

Question 26

Parathyroid gland anatomy

Answer 26

Variable appearance and location Generally found on or near thyroid Often 2 pairs – one pair on the surface of the thyroid the other pair within the thyroid Appear as small pale nodules

Question 27

Parathyroid hormone is and functions to

Answer 27

Aka parathormone Functions to keep blood calcium levels from getting too low by increasing Renal retention Intestinal absorption Bone calcium mobilization Also promotes the formation of active form of Vitamin D in the kidneys

Question 28

Adrenal gland anatomy

Answer 28

Paired Found near the cranial end of kidneys Composed of 2 parts: Outer layer: adrenal cortex Inner part: adrenal medulla

Question 29

Adrenal cortex

Answer 29

Typical glandular tissue Makes 3 types of hormones, collectively called steroid hormones Has 3 layers: producing, from outer to inner layers

Question 30

Mineralcorticoid Hormone is also called and function

Answer 30

Aldosterone Regulates mineral salt (electrolyte) levels Increases blood sodium, decreases potassium and hydrogen ions through effects on kidneys Also assists in water retention as water follows reabsorbed sodium

Question 31

Mineralocorticoid Hormone release is stimulated by

Answer 31

renin-angiotensin system Renin is released from the kidneys in response to sympathetic stimulation and decreasing blood pressure Converts a blood precursor peptide to angiotensin II Angiotensin II causes vasoconstriction to increase BP and decrease renal perfusion and stimulates aldosterone release to retain fluid

Question 32

Glucocorticoid hormone is

Answer 32

Includes cortisone, cortisol, corticosterone Primarily associated with stress response Help maintain BP Mobilizes proteins and fats and promotes gluconeogenesis in the liver Gluconeogenesis- synthesis of “new” glucose Have anti-inflammatory effects Drugs such as prednisone, dexamethasone, triamcinolone, and hydrocortisone mimic the effects of glucocorticoids – often use to control inflammation.

Question 33

Side effects of glucocorticoid hormones producing drugs

Answer 33

PU/PD Immunosuppression Altered WBC counts Delayed wound healing Catabolism of proteins Abortion Hyperglycemia Suppression of normal adrenal cortical secretions Called iatrogenic hyperadrenocorticism

Question 34

Sex hormones produced by adrenal cortex

Answer 34

innermost layer of the Adrenal cortex produces small amounts of androgens and estrogen with minimal systemic effects

Question 35

Adrenal medulla is

Answer 35

Nervous tissue origin Hormone-secreting cells are modified neurons Produces mainly epinephrine and some norepinephrine Responds to sympathetic stimulation – ‘fight or flight’ response Fight or Flight Response

Question 36

Adrenal medulla effects on the body

Answer 36

Increased HR Increased CO Increased BP Dilated airways Decreased GI motility Increases blood glucose

Question 37

Pancreas shape

Answer 37

Long, flat organ that runs alongside the duodenum Has both exocrine and endocrine functions Exocrine part secretes digestive enzymes into duodenum Endocrine part is small, but important!!

Question 38

Pancreatic inlets are and types of hormones produced

Answer 38

Thousands of tiny clumps of cells Scattered throughout the pancreas Called Islets of Langerhans Three types of cells in the islets each of which produces its own distinct hormone Alpha cells= glucagon Beta cells= insulin Delta cells= somatostatin

Question 39

Insulin is and does what

Answer 39

Vital to life Allows cells to absorb glucose (works by increasing transport proteins on cell membrane) Increases glycogen production in liver and muscle Increases protein and fat synthesis Primary measured effect is to lower blood glucose

Question 40

Hormones produced by the pancreas

Answer 40

Insulin Glucagon Somatostatin

Question 41

Hormones produced by the adrenal cortex

Answer 41

Mineralcorticoid hormone Glucocorticoid hormone

Question 42

Glucagon hormone is

Answer 42

Not as vital as insulin because other hormones have similar effects in the body Raises blood glucose Stimulates glycogenolysis and gluconeogenesis

Question 43

Somatostatin is

Answer 43

Inhibits secretion of insulin, glucagon and growth hormone Decreases GI motility

Question 44

Gonads are

Answer 44

The reproductive organs Paired organs Testes (singular testis)- males Ovaries- female Produce the reproductive cells (spermatozoa and ova) with ½ the number of chromosomes as a human somatic cells Also produce hormones responsible for development of sex characteristics

Question 45

Testes are and functions

Answer 45

Found in the scrotum Seminiferous tubules continuously produce sperm Interstitial; cells Between tubules Produce androgens Primarily testosterone Important for development of male secondary sex characteristics (muscles, libido, accessory sex glands, growth of penis) Metabolic effect is anabolic Production stimulated by LH from anterior pituitary

Question 46

Ovaries are

Answer 46

Paired organs Found in the abdomen behind the kidneys Cyclical production of hormones and ova (eggs) Controlled by FSH and LH

Question 47

Estrogens are

Answer 47

Mainly estradiol and estrone Produced by developing follicle cells in response to FSH Cause physical and behavioral changes of estrus – in preparation for breeding and pregnancy As levels increase, they feedback to pituitary and decrease FSH and increase LH Ovulation occurs at / just after LH peak (in most animals)

Question 48

Progestins are

Answer 48

After ovulation, LH stimulates the empty follicle to develop into a corpus luteum (CL) CL produces progestins such as progesterone Very important for maintaining pregnancy

Question 49

Erythropoietin is

Answer 49

Produced by the kidneys stimulates RBC production in response to hypoxia Chronic renal failure is often accompanied by anemia due to decreased EPO production May become life – threatening and require transfusion or Epo supplementation (very expensive)

Question 50

Placenta is

Answer 50

Varies by species, but overall purpose is to help maintain pregnancy Secretes Estrogen and progesterone Chorionic gonadotropin: primarily in humans and horses. This is an LH like hormone that maintains the CL. It is used in some pregnancy tests.

Question 51

Thymus is

Answer 51

Important in developing immunity in immature animals Involved in development of T-lymphocytes important for cell-mediated immunity Hormones include thymosin and thymopoietin Shrinks to remnant in adulthood

Question 52

Pineal body produces what and affects what

Answer 52

Melatonin: affects biological clocks and sleep/wake cycles High concentration at night Some people use to for jet lag Poorly understood – linked to seasonal estrus in some species

Question 53

Excess GH can cause

Answer 53

Gigantism Excess hormone while growing Exaggerated bone growth, abnormally tall Acromegaly Excess hormone when mature Growth plates are closed, see cartilage proliferation around joints and facial changes- large nose, lips, forehead

Question 54

Deficiency of GH can cause

Answer 54

Dwarfism Alopecia Thin skin Secondary abnormalities of thyroid, adrenal and reproductive hormones

Question 55

Diagnosis of diabetes mellitus and treatment

Answer 55

Diagnosis: detection of elevated blood glucose and glucose in the urine Treatment involves the subcutaneous injection of insulin, close monitoring of food intake, blood and urine glucose levels Canned food for cats! Special diets can help with the stabilization of insulin dosages

Question 56

Diabetes insipidus is and caused by

Answer 56

Caused by a failure of the kidneys to reabsorb water. Due to either A deficiency of antidiuretic hormone Failure of the renal collecting ducts to respond to ADH

Question 57

Clinical signs and diagnosis of diabetes insipidus

Answer 57

Clinical signs include Polyuria Polydipsia Very dilute urine (decreased specific gravity) Diagnosis is made by withholding water and monitoring urine SG, or by administering a synthetic ADH and monitoring urine SG Water deprivation test- can be dangerous, only withhold water for short time

Question 58

Cushings disease is, clinical signs and diagnosis

Answer 58

Caused by excessive administration of steroids (iatrogenic) or by an overproduction of steroids by the adrenal cortex (often due to pituitary or adrenal neoplasia) Neoplasia = tumor, can be cancerous or non cancerous Clinical signs include Polyuria, polydipsia Increased appetite Abdominal distension Muscle atrophy and weakness Lethargy Thinning skin and alopecia Excessively long hair coat in horses More susceptible to infections Diagnosis is generally made by blood tests Base line blood sample, than inject wither ACTH- adrenocorticotropic hormone Dexamethasone Then, take timed blood samples to monitor the cortisol levels

Question 59

Addisons disease is and clinical signs

Answer 59

Hypoadrenocorticism Deficincy of mineralcotocoid +/- glucorticoid from the adrenal cortex, due to Immune-mediated destruction (most often) long term steroid administaration (iatrogenic) or neoplasia Low sodium, high potassium, low HR and BP, weakness Life-threatening!! Clinical signs include Polydipsia Polyuria Anorexia Vomiting and diarrhea Hypotension Bradycardia Acute collapse

Question 60

Addisions disease diagnosis and treatment

Answer 60

Diagnosis includes blood tests for electrolyte imbalances (especially the sodium and high potassium) and the ACTH stimulation test Treatment involves the administration of glucocorticoids and mineralocorticoids

Question 61

Goiter thyroid problem is

Answer 61

non cancerous thyroid gland enlargement Usually caused by iodine deficiency Iodine is a required component of T3 and T4 Body senses decreased T4 levels, so pituitary makes more TSH Thyroid gland becomes hyperplastic and enlarged, but is still deficient amounts of T3 and T4!! Hypothyroid Supplement diet with iodized salt

Question 62

Hypothyroidism is, signs, and treatment

Answer 62

Most common in adult dogs Low levels of T3 and T4 SIgns include alopecia, dry skin, lethargy, weight gain, heat seeking, and slow heart rate If occurs in young animals, can cause dwarfism- often called cretinism Stunted growth, abnormal bone formation, mental retardation, sluggishness Treat with thyroid supplements

Question 63

Hyperthyroidism is, signs and treatment

Answer 63

Most common in cats High levels of T3 and T4 Signs include nervousness, irritability, weight loss despite increased appetite, fast heart rate, vomiting (V+), diarrhea (D+), PU/PD Treat with surgical removal of gland, medication to inhibit thyroid hormone production (often for life), or radioactive iodine treatment to kill gland

Question 64

Hyperparathyroidism is and clinical signs

Answer 64

In secondary hyperparathyroidism blood calcium is low Renal secondary Renal diseases stops calcitriol (active vitamin D) formation Nutritional secondary hyperparathyroidism Inadequate calcium in diet Mostly grain or meat Clinical signs of secondary hyperparathyroidism Rubber jaw Lameness Reluctance to move Pathological fractures Limb deformities in growing animals (rickets) Due to reabsorption of calcium from bone and include (osteoporosis)