Endocrine system

Question 1

Negative Feedback

Answer 1

Output shuts off the original effect of the stimulus or reduces its intensity.

Cause variable to change in direction opposite to that of the initial change.

Eg regulation of body temperature and controlling blood sugar levels.

Question 2

Positive Feedback

Answer 2

Result or response enhanced the original stimulus so that the response is accelerated.

Usually control infrequent events that do not require continuous adjustments.

Eg labour contractions and blood clotting

Question 3

Hormones:

Answer 3

chemical messengers secreted by cells into extra cellular fluids. Regulate metabolic function of other cells in the body

Major processes controlled:
Reproduction
Growth and development
Maintenance of electrolyte
Regulation of cellular metabolism
Mobilisation of body defences

Question 4

Two types of glands

Answer 4

Exocrine: produce non hormonal substances eg sweat and saliva and have ducts that carry these substances to membrane surface

Endocrine: produce hormones and lack ducts. Hormones are released into surrounding tissue fluid that have typically rich vascular and lymphatic drainage

Question 5

Main types of hormones

Answer 5

Water Soluble: amino acid based and vary greatly in size.
They act on receptors in the plasma membrane as they can not enter the cell

Lipid Soluble: steroids are synthesised from cholesterol
Act on receptors inside the cells which directly activate genes as they can pass through the cell membrane.

Question 6

Hormones Action

Answer 6

May affect all the cells of the body or only particular groups of cells (target cells) or particular organs

Hormones circulate to almost all tissues but only affect those which have receptors for the particular hormone.

Typical changes brought about:
Alters membrane permeability
Stimulates synthesis of enzymes and other proteins
Activated or deactivates enzymes
Induces secretory activity
Stimulates mitosis

Question 7

Hormones: Anterior Pituitary

Answer 7

Follicle Stimulating Hormone (FSH) - growth of follicles or production of sperm

Lutenising Hormone - ovulation and maintenance of corpus luteum/secretion of testosterone

Growth Hormone- growth and protein synthesis

Thyroid Stimulating Hormone (TSH) - stimulates the secretion if hormones from thyroid

Adrenocorticotropic Hormone (ACTH) - secretion of hormones from adrenal cortex

Prolactin- milk production

Question 8

Hormones: posterior pituitary gland

Answer 8

Antidiuretic Hormone (ADH) - reabsorption of water

Oxytocin- contraction of uterus during childbirth

Question 9

Hormones: thyroid

Answer 9

Thyroxine - increases metabolic rate therefore Oxygen consumption and heat production

Calcitonin - decreases blood calcium levels by inhibiting the breaking down of bone and filtration of calcium

Question 10

Hormones: parathyroids

Answer 10

Parathyroid hormone - increases the levels of calcium in the blood, increases rate at which bone is broken down.

Question 11

Hormones: thymus

Answer 11

Thymosins- stimulates development of T lymphocytes

Question 12

Hormones:Adrenal Cortex

Answer 12

Aldosterone - increases reabsorption Of Sodium and excretion of K+

Cortisol - promoted normal metabolism and repair and helps body deal with stress

Question 13

Hormones: adrenal medulla

Answer 13

Adrenaline and Noradrenaline - fight or flight response, reinforces the effects of sympathetic nervous system

Question 14

Hormones: pancreas

Answer 14

Insulin - stimulates uptake of glucose

Glucagon - stimulates the breakdown of glycogen and fat therefore increases blood glucose levels.

Question 15

Hormones: Testes

Answer 15

Androgens - stimulate sperm production, growth of skeleton and muscle as well as male sexual characteristics

Question 16

Hormones:Ovaries

Answer 16

Oestrogens - stimulate development of female sexual characteristics m; regulate menstrual cycle.

Progesterone - regulates menstrual cycle and pregnancy; prepares mammary glands for milk secretion

Question 17

Hypothalamus:

Answer 17

Located at base of the brain

Regulates basic functions including body temp. Water balance. Heart rate. Connected to the pituitary gland but the infundibulum.

Question 18

Pituitary Gland anterior lobe

Answer 18

anterior (front) lobe: has no nerves connecting it to hypothalamus. Instead by network of blood capillaries
Manufactures and releases its own hormones under control of inhibiting and releasing factors (Neurohormones) secreted by hypothalamus.

Question 19

Pituitary Gland posterior lobe

Answer 19

Posterior lobe: receives ready made hormones from hypothalamus through extensions of nerve cells.

It is a hormone storage area and not a true endocrine gland that manufactures hormones.

Question 20

Regulation of Blood Sugar: low blood sugar

Answer 20

Stimulus: ⬇️ blood sugar
Receptor: Pancreas
Modulator: Alpha cells in islet of langerhans

Release Glucagon

Effector: Liver, skeletal muscle, cells
Response: ⬆️ glycogenolysis and glyconeogenesis

Question 21

Regulation of Blood Sugar levels: high blood sugar

Answer 21

Stimulus: ⬆️blood sugar
Receptor: Pancreas
Modulator: beta cells in islet of langerhans

Release insulin

Effector: Liver
Response: ⬆️ glycogenesis

Question 22

Glycogenesis

Answer 22

Formation of glycogen from glucose

Question 23

Glycogenolysis

Answer 23

Break down of glycogen Into glucose in the liver

Question 24

Glyconeogenesis

Answer 24

Conversion of fats or proteins into glucose.

Question 25

Adrenal Glands can also influence blood sugar levels

Answer 25

adrenal medulla Stress stimulates hypothalamus which stimulates medulla by nervous system to Release adrenaline causing liver to increase rate of Glyconeogenesis and Glycogenolysis increasing blood sugar Adrenal Cortex stress stimulates hypothalamus to release cortisone releasing hormones Tells anterior pituitary to release ACH Tells adrenal cortex to release cortisol Causing liver to increase Glycogenolysis and Glyconeogenesis

Question 26

Effect of ADH (Antidiuretic Hormone)

Answer 26

ADH inhibits urine output, makes cells of distal convoluted tubule and collecting duct more permeable to water by creating aquaporins (water channels) in their membranes influencing amount of water reabsorbed there

Question 27

ADH feedback loop

Answer 27

Stimulus: decreased blood volume Reduced blood pressure Increases osmotic pressure =dehydration receptor: osmoreceptors in hypothalamus activate thirst reflex Modulator: nerves signal the posterior pituitary to release ADH Effector: DCT and collecting duct creates more aquaporins Response: increased permeability allowing for more water to be reabsorbed Osmotic pressure maintained or reduced

Question 28

The Effect of Aldosterone

Answer 28

Bonds to cells in DCT and loop of Henle . Promotes increase in blood volume and pressure by conserving sodium and chloride ions. aldosterone stimulates sodium pumps in DCT and loop of Henle increasing amount of sodium reabsorbed. Creating osmotic gradient in which water will move out into the surrounding fluid and be reabsorbed

Question 29

The effect of aldosterone feedback loop

Answer 29

Stimulus: ⬇️ blood volume and pressure Receptor: baroreceptors in renal artery Modulator: adrenal Cortex Releases aldosterone Effector: sodium pumps in DCT and Loop of Henle Response: sodium reabsorbed Effect: creates osmotic gradient meaning water is reabsorbed

Question 30

Homeostasis

Answer 30

Dynamic state of equilibrium in which internal conditions may vary but always within relatively narrow limits.