Unit 7: Hormonal control in plants and animals

local regulators

chemical signaling molecule that acts on nearby cells through diffusion, such as cytokines and neurotransmitters

hormones

secreted molecule that circulates throughout the body and stimulates specific cells.

exocrine gland

a gland that secretes substances into a body cavity or onto the body surface.

• sweat and digestive juices

endocrine gland

a gland that secreates subtances that control growth and metabolism into the blood stream to be transported to other parts of the body

what are most hormones derived from

amino acids, polypeptides, or steroids.

steroid hormones need what to travel through blood

need to bind to transport proteins (also known as carrier proteins or binding globulins) to travel through the bloodstream. 

polypeptide based hormones need what to go through blood

can travel through blood freely

what are the hormones secreted by the adrenal cortex and gonads compared to everyother endocrine gland

steroids,

all others secrete hormones derived from proteins or amino acids

How do steriod and thyroid hormones act 

they are lipid soluble and hydrophobic so they can enter target cells and bind with intracellular receptors that elicit a response

how do polypeptide hormones act

they are water soluble and hydrophilic bind to specific receptors on the outside of the cell membrane to initiate a signal transduction pathway

What feature of a hormone determines whether it will initiate a signal transduction pathway or regulate gene expression

whether it is a steroid or polypeptide-based hormone.

• Steroid-based hormones are hydrophobic, which allows them to enter the cell and regulate gene expression

• Polypeptide-based hormones are hydrophilic and must interact with a cell-surface receptor protein, which creates a signal transduction pathway 

how does the signal transduction model work

• A water-soluble hormone binds to an extracellular protein receptor

• signal travels to adeline cyclase to create cAMP with ATP

• The cAMP is used as a secondary messenger and activates an inactive protein

• activated protein conducts a cellular response

Explain the general mechanism by which lipid-soluble (hydrophobic) steroid hormones affect target cells

• A steroid hormone goes through the cell membrane

• binds to a steroid hormone receptor located in the cytosol, creating a hormone receptor complex

• Complex moves into the nucleus, where it interacts with DNA

• This then activates certain transcription and gene expression

cell's response to stimulation by a polypeptide hormone

Is it rapid or slow, short-lived or long-lived?

rapid and short-lived

• Rapid: effects begin within seconds to minutes because existing proteins or enzymes are modified (no need to make new ones).

• Short-lived: once the hormone is degraded or signaling stops and effect fades.

cell's response to stimulation by a steroid hormone

Is it rapid or slow, short-lived or long-lived?

slow and longlived

• Slow: it takes time (minutes to hours) for transcription and translation of new proteins to occur.

• Long-lived: newly synthesized proteins remain active even after the hormone is gone, so effects can last hours to days.

The particular proteins that a cell possesses determine what

the signal molecules it responds to and the nature of the response

target specificity of hormones in terms of receptors

hormone’s target specificity is determined by the presence of specific receptors on target cells that only hormones can bind to

Why does epinephrine in a liver cell cause that cell to hydrolyze glycogen to glucose, whereas epinephrine in skeletal muscle causes it to dilate?

though epinephrine is the same hormone, it will create a different effect with different target cells

this is due to the cells haveing different transduction pathways and different receptors

how is the endocrine system regulated

negative feedback loops 

direct negative feedback loop

a regulatory pathway where the final product in a single chain directly inhibits its own production

indirect negative feedback loop

Involves multiple hormone levels in a regulatory chain. The final hormone in the pathway feeds back to inhibit the earlier glands (often the hypothalamus and/or pituitary).

positive feedback

When the final product in a chain increases, the production of the product

What are tropic hormones

hormones that stimulate other endocrine glands to produce and release their hormones

The hypothalamus produces TRH so that the anterior pituitary can produce TSH

why is it good to have a pair of hormones that have opposite effects

they work together to fine tune a response

What type of cell in the pancreas synthesizes insulin

Beta cells: the majority of cells within the islets of Langerhans

insulin

Lowers blood glucose level

• peptide hormone

What type of cell in the pancreas synthesizes glucagon

Alpha cells: found in the islets of Langerhans

Glucagon 

Raises blood glucose level

• peptide hormone

Where is the pancreas located in relation to the stomach and small intestine?

the pancreas is posterior to the stomach and supperior to the small intestins

• connects via the duodenum 

How does insulin affect the uptake of glucose into muscle and adipose tissue? 

Insulin increases glucose uptake in muscle and adipose tissue

how does insulin affect the synthesis (stimulate or inhibit) and degradation (stimulate or inhibit) of fats

fat synthesis (lipogensis): stimluated

fat degradation (lipolysis): inhibited

insulin is responsible for the uptake and storage of glucose 

How does insulin affect the synthesis (stimulate or inhibit) and degradation (stimulate or inhibit) of protein

Protein synthesis: stimulated

Protein degradation: inhibited

insulin promotes the building of muscles

How does insulin affect the synthesis (stimulate or inhibit) and degradation (stimulate or inhibit) of glycogen

glycogen synthesis: stimulated

glycogen degradation: inhibited

insulin wants to increase storage of sugar

How is the blood sugar level regulated and maintained after a meal high in carbohydrates is eaten

After a meal high in carbs, the blood glucose levels are going to be high

• Insulin is released to reduce blood sugar levels by

  • stimulating glucose uptake 

  • glycogen formation

  • muscle growth

  • inhibit alpha cells

  • stimulate beta cells

How is the blood sugar level regulated and maintained several hours after a meal high in carbohydrates is eaten

Between meals, glucose levels decrease 

• Glucagon is released to increase blood sugar levels

• works mainly in the liver 

  • stimulate glycogenolysis

  • stimulates gluconeogenesis

  • inhibit beta cells

  • stimulate alpha cells

Diabetes mellitus has been described as "starvation in the midst of plenty." Explain the meaning of this statement

It describes how, despite high levels of sugar (glucose) in the blood, the body's cells are unable to use it for energy

juvenile-onset or insulin dependent Type 1 diabetes 

autoimmune disorder in which the immune system destroys the beta cells of the pancreas and thus no insulin is produced 

Adult-onset or non-insulin-dependent diabetes

Type 2 diabetes

When the target cells are unable to take up glucose despite insulin being produced. The receptors get desensitized to the amount of insulin and stop working 

one major symptom of Type 1 diabetes and how it relates to the function of insulin

one major symptom is sweet and excessive urine. This is due to the fact that since no glucose is being taken up the kidneys need to filter out all of the excess sugar in the blood, which pulls water with it. 

In a normal individual, what happens to insulin secretion when the blood glucose level is high? ...low?

High: insulin secreation increases 

low: insulin secreation decreases 

parts of the pituitary gland

• Anterior Pituitary

• Posterior Pituitary 

Completely seperate systems 

anterior pituitary

endocrine gland that synthesizes and secretes hormones in response to hormones from the hypothalamus

posterior pituitary

stores and secretes hormones synthesized in the hypothalamus.

extension of the hypothalamus 

What is the function of the hormones of the anterior pituitary and hypothalamus

They have master regulating roles,

orchestrate the action of several glands through complex negative feedback loops.

Describe the structural and functional relationships between the hypothalamus and the pituitary

The hypothalamus acts as the command center which regulates how much master hormones are produced from the pituitary

Describe the relative location of the hypothalamus and pituitary gland within the skull

The hypothalamus is superior to the pituitary 

where is oxytocin and ADH are synthesized and where they are stored.

They are synthesized from neurosecretory cells of the hypothalamus

stored in the posterior pituitary gland

Neurosecretory cells of the hypothalamus

produce neurohormonse and are alink between the nervous and endocrine system 

Oxytocin 

has functions related to reproduction.

• controls milk secretion by the mammary glands

• regulates uterine contractions during birthing

• maternal care

• pair bonding

• sexual activity

peptide hormone

ADH

vasopressin

• regulates kidney function

  • ADH increases water retention in the kidneys, helping maintain normal blood osmolarity

• has a role in social behavior

peptide hormone

What is the effect of ADH on urine volume

decreases, ADH promotes water retention in the kidneys

Describe the role of releasing hormones produced in the hypothalamus for hormones produced by the anterior pituitary.

Hormones from the hypothalamus control the amount of release of hormones produced in the anterior pituitary

Describe the special arrangement of blood vessels in the hypothalamus and anterior pituitary (portal system)

a specialized blood vessel network connecting the hypothalamus and the anterior pituitary gland

• ensures that inhibiting hormones secreted by the hypothalamus reach the anterior pituitary quickly and in high concentration

• 2 capillary beds

Thyroid-stimulating hormone

(TSH) 

• site of synthesis 

• major role

site of synthesis 

• anterior pituitary gland

major role

• stimulate the thyroid gland to produce and release thyroid hormones (T3 and T4)

Gonadotropic hormones (FSH and

LH)

• site of synthesis 

• major role

site of synthesis 

• anterior pituitary gland

major role

• regulate gametogenesis (the formation of sperm and eggs)

• steroidogenesis (production of sex hormones: estrogen and testosterone)

Adrenocorticotropic hormone (ACTH)

• site of synthesis 

• major role

site of synthesis

• anterior pituitary gland

major role

• stimulate the adrenal cortex to produce and release cortisol

Prolactin (PRL)

• site of synthesis 

• major role

site of synthesis

• anterior piruitary gland

major function

• stimulate milk production in the mammary glands after childbirth

Growth hormone (GH)

• site of synthesis 

• major role

site of synthesis

• anterior pituitary gland

major role

• Promoting linear growth in children and adolescents

Gonadotropic-releasing hormone

(GnRH)

• site of synthesis 

• major role

site of synthesis

• hypothalamus

major function

• regulate the reproductive system by controlling the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland

why is the pituitary gland called the master gland

why is the pituitary gland called the master gland

does the pituitary gland control all endocrine glands 

no, it controls most 

describe the negative feedback control of thyroid hormone secretion. Is this a direct or indirect negative feedback loop?

1. thyroid hormone levels drop below the normal range 

2. detected by sensory neurons, which send a signal to neurosecretory cells in

   the hypothalamus.

3. Neurosecretory cells secrete thyrotropin-releasing hormone (TRH ) into the portal system to the anterior pituitary gland 

4. TRH causes the anterior pituitary to secrete thyroid-stimulating hormone (TSH, also known as thyrotropin) into the circulatory system.

5. TSH stimulates endocrine cells to release T3 and T4 into the blood

6. Thyroid hormone levels return to normal, and excess thyroid hormones block TRH release in the hypothalamus

is the thyroid hormones (T3 and T4) hydrophilic or hydrophobic

hydrophobic

how does T3 and T4 initiate the response pathway

acting on target cells through nuclear receptors to alter gene expression

The thyroid hormones are derived from what molecule?

the amino acid tyrosene 

What effect do T3 and T4 have upon growth and development?

promotes normal growth in the body, particularly in the brain and skeleton

What happens to individuals with a congenital (from birth) deficiency of T3 and T4? And what is it called

hypothyrodism

weight gain, lethargy, and intolerance to cold in adults

What happens to individuals with a congenital (from birth) overproduction of T3 and T4? And what is it called

hyperthyroidism

high body temperature, profuse sweating, weight loss, irritability, and high blood pressure

State the effect of T3 and T4 upon homeostasis, particularly the rate of cellular metabolism

• T3 and T4 increase the basal metabolic rate (BMR) by stimulating cells to produce more ATP.

• They increase the number and activity of mitochondria

  • leads to higher oxygen use and energy output.

• This raises body temperature

  • helping maintain thermal homeostasis.

More T₃/T₄ → Faster metabolism → More ATP and heat production

Less T₃/T₄ → Slower metabolism → Less ATP and heat production

Describe how parathyroid hormone (PTH) regulates blood calcium ion levels.

1. blood calcium levels fall below average 

2. Parathyroid glands release PTH in response 

3. PTH goes to the bone and stimulates Ca2+ release 

3. In the kidney, PTH stimulates

   Ca2+ reabsorption from

   filtrate and promotes

   activation of vitamin D

4. The activated vitamin D causes the small intestines to reabsorb more Ca2+ from food

5. Ca levels in blood rise 

place where Ca2+ is highest in a cell. By what process is Ca2+ accumulated in these structures?

endoplasmic reticulum of the cell

• active transport via Ca2+ pump

What is the direction Ca2+ ions move when the channel is open

from the ERs to the cytoplasm 

the importance of Ca2+ in cell function

Calcium ions act as a universal intracellular signal

• a kind of “on switch” for many biological processes.

adreanal gland parts 

cortex and medulla

• these parts are seperate 

which organ is the adrenal gland associated too

Kidneys

what are catecholamines

a collection of hormones and neurotransmitters that are involved in regulating the body’s fight or flight response 

• epinephrine

• norepinephrine

• dopamine

where are catecholamines produced 

adrenal medulla and the inner part of the adrenal glands

How do catecholamines function in maintaining homeostasis with respect to blood sugar?

They increase glucose availability to meet immediate energy demands,

• stimulate the liver to produce and release glucose through glycogenolysis and gluconeogenesis

How do catecholamines compare to insulin? 

they have opposite effects 

how does epinephrine effect blood pressure

Increases BP

Epinephrine causes vasoconstriction (narrowing) of some blood vessels, increasing overall blood pressure.

• allowing for more rapid oxygen and nutrient delivery to vital organs

how does epinephrine effect heartbeat

Increases

Stimulates the SA node and heart muscle, increasing both rate and strength of contractions.

• This raises cardiac output, sending more blood (and oxygen) to active tissues.

how does epiephrine effect the rate of conversion of glycogen to glucose

Increases

Stimulates glycogenolysis in the liver and muscles

• provides quick energy source (ATP) for muscles and the brain.

how does epinephrine effect the rate of oxygen consumption by cells

Increases

• to meet the sudden energy demand the cells will need oxygen

how does epinephrine effect the rate of blood supply to skeletal and heart muscle

Increases (vasodilation)

• Blood vessels in skeletal and cardiac muscles dilate, ensuring more oxygen and glucose are delivered where energy demand is highest.

how does epinephrine effect the rate of blood supply to skin, digestive tract, and kidneys

Decreases (vasoconstriction)

Blood is redirected away from non-essential organs during emergencies to conserve energy and supply vital organs (muscles, heart, brain).

• This is why skin may appear pale and digestion slows under stress.

how does epiephrine effect peristalsis of the intestine

Decreases (inhibited)

Smooth muscle contractions in the digestive tract slow down or stop, conserving energy for critical systems like the heart and muscles.

What are the two primary types of corticosteroids?

• glucocorticoids

• mineralocorticoids

What is the primary effect of glucocorticoids, such as cortisol?

increase blood glucose levels and mobilize energy reserves to help the body cope with long-term stress.

how do the effects of glucocorticoids  compare to that of insulin

they have opposite effects 

What is the primary effect of mineralocorticoids like aldosterone?

they increase Na⁺ reabsorption and K⁺ secretion in kidneys

• Results in an increase in water retention, blood volume, and blood pressure

Name the three glands that produce steroid hormones.

• Adrenal cortex

• Gonads

• Placenta

Hormones of the adrenal cortex

Glucocorticoids 

• Cortisol

Mineralocorticoids 

• Aldosterone

Androgens

• DHEA

• Androstenedione

Compare and contrast the functions of the hormones FSH and LH in the human male

FSH Males

• stimulate Sertoli cells, located within the seminiferous tubules, to nourish developing sperm

LH Males

• Stimulates Leydig cells to produce testosterone, which supports sperm production and secondary sexual characteristics.

Compare and contrast the functions of the hormones FSH and LH in the human female

FSH females

• Stimulates growth and maturation of ovarian follicles

• Promotes estrogen secretion from the growing follicle

LH females 

• Triggers ovulation (release of the egg from the mature follicle).

• Stimulates formation of the corpus luteum, which secretes progesterone and estrogen to maintain the uterine lining.

How are testosterone levels regulated in the human male.

through negative feedback

What would be the effect on the hormonal system if a male takes anabolic steroids, which are testosterone analogs?

Taking anabolic steroids shuts down the body’s own testosterone production through negative feedback on the hypothalamus and pituitary, leading to reproductive and hormonal imbalances.

Ovarian cycle in females

• Follicular phase

• Ovulation

• Luteal phase 

Follicular phase

• Days

• Main Hormones (increase or decrease)

• Ovarian Events

• Uterine Effects

• 1–14 days

• hypothalamus: secreates GnRH → stimulates the anterior pituitary to release FSH and LH

  • from this estradiol production is stimulated 

• FSH promotes the growth and maturation of several ovarian follicles.

  The granulosa cells of these follicles secrete estriol as they grow.

• Estriol stimulates endometrial thickening (proliferative phase of the uterine cycle).

Ovulation phase

• Days

• Main Hormones (increase or decrease)

• Ovarian Events

• Uterine Effects

• ~14

• LH surge, estriol creates a positive feedback loop with the hypothalamus

• The LH surge triggers the mature follicle to rupture, releasing the egg (ovum) from the ovary into the fallopian tube. (ovulation)

• The endometrium continues to thicken in case of implantation

Luteal phase

• Days

• Main Hormones (increase or decrease)

• Ovarian Events

• Uterine Effects

• 15–28

• ↑ Progesterone, ↑ Estrodiol

• The corpus luteum forms and secretes high levels of progesterone and some estradiol

  • progesterone maintains and further develops the endometrial membrane 

  • Exerts negative feedback on the hypothalamus and anterior pituitary, suppressing GnRH, LH, and FSH secretion.

• Endometrium maintained; if no fertilization → menstruation