BIOL:1412 Exam 3

What happens in the anterior pituitary gland?

Neurons connect with neuroendocrine cells and releases hormones

Does the anterior pituitary gland have a neural connection with the hypothalamus?

No

Does the posterior pituitary gland have a neural connection with the hypothalamus?

Yes

How does the anterior pituitary gland interact with the hypothalamus?

Through capillaries (hypophyseal portal system)

Releasing hormones (RH)

Anterior pituitary stimulates cells to release hormones

Inhibiting hormones (IHs)

Stops signaling at pituitary gland, there is not continuous pathway

What are tropins?

They control other endocrine glands

What is ACTH?

Adrenocorticotropic hormone

What is TSH?

Thyroid stimulating hormone

What are the tropins released by the anterior pituitary gland?

• ACTH

• TSH

• FSH

• LH

What is FSH?

Follicle stimulating hormone

What is LH?

Luteinizing hormone

What does ACTH target?

Adrenal cortex

What does TSH target?

Thyroid

What does FSH target?

Gonads

What does LH target?

Gonads

What tropins have no effect on endocrine glands?

GH and RRL

What is GH?

Growth hormone

What is RRL?

Prolactin

What does GH do?

Promotes things like mitosis and cell division for growth (most common)

What does RRL do?

Produces breast milk (exocrine)

Where do TRH, GnRH, CRH, and GHRH come from?

Hypothalamus

What is TRH?

Thyrotropin-releasing hormone

What is TRH used for?

controls your metabolism and energy

What is GnRH?

gonadotropin-releasing hormone

What does GnRH do?

controls reproduction

What is CRH?

corticotropin-releasing hormone

What does CRH do?

a leading global provider of building materials and construction solution

What is GHRH?

Growth Hormone-Releasing Hormone

What does GHRH do?

tells the pituitary gland to release growth hormone into the blood

Why isn’t the posterior pituitary gland an actual gland?

it does not synthesize or produce its own hormones; it only stores and releases hormones manufactured by the hypothalamus

How are signals sent to the posterior pituitary gland?

through axons through a neural connection

ADH (antidiuretic hormone)

prevents kidneys from losing too much water

Oxytocin

targets uterus (contractions), social hormone (promotes social bonding), plays a role in releasing breast milk

Why wouldn’t you want positive feedback in terms of hormones?

it would release something, then amplify it

How does negative feedback work?

an upstream is sent back to the pituitary gland and hypothalamus

What are endocrine axes?

a sequence of interacting hormone-producing glands that link the brain to peripheral organs to regulate major bodily functions like stress, growth, and metabolism

Pineal gland

a tiny, pinecone-shaped endocrine gland located deep in the center of the brain, responsible for melatonin production

Thyroid

a butterfly-shaped endocrine gland in the front of the neck that regulates metabolism

Thymus

thymus is an immune organ located in the upper chest (behind the sternum) that trains white blood cells during childhood

Adrenal cortex

sits atop kidneys and produces vital steroid hormones that control metabolism, blood pressure, salt and water balance, and stress responses

Medulla

the lowest part of the brainstem that connects the brain to the spinal cord—is responsible for the secretion of norepinephrine and epinephrine

Pancreas

responsible for insulin and glucagon production

The thyroid gland is __ unlike the pancreas or liver

purely endocrine

Follicular cells

• secretes TH

• regulates BMR

• TH increases BMR

BMR

the minimum number of calories your body needs to perform basic, life-sustaining functions while at complete rest

Colloid

gelatinous protein-based material that is a polymer of TH

Why are there a lot of capillaries in the thyroid gland?

because iodine needs to be delivered through the blood to colloid space to become TH

Parafollicular cells

• secretes calcitonin

• ligher in color

Hyperthyroidism

• high BMR

• weight loss

• hyper active

Extreme hypothyroidism can result in a __

goiter

If there’s no dietary iodine, there’s no __

TH made

If there’s no TH, there’s __

nothing to stop the production of TSH

If there’s more TSH, there’s __

more thyroglobin (Tg)

If there’s more Tg, __

larger follicles, which results in thyroid swelling

Gonads are mostly composed of __ hormones

steroid

For testes, GnRH is very __

minimal until puberty

PTTH (Prothoracicicotropic hormone)

• target: prothoracic glands (similar to the hypothalamus)

• controls secretion of ecdysone

Ecdysone

• converted to molting hormone

• activates molting

  • targets epidermis → loosens connection with exoskeleton

JH (Juvenile hormone)

affects developmental stage

Budding

a parent grows bud, then breaks—outgrowth grows into an adult

Fission

parent splits itself and breaks into two → both function as individuals

Pros of asexual reproduction

Favorable genetic combinations remain together and faster mechanisms

Cons of asexual reproduction

prevents breaking up combinations, doesn’t create diversity—no selection

Parthenogenisis

offspring develop from unfertilized egg

• usually haploid (goes through duplication)

Regeneration

a piece has been severed off of the parent—piece can develop into its own individual

Cons of sexual reproduction

• a lot of energy

• locating a mate

• mating ritual, competition

  • competition can result in death

• successful copulation

• breaks up favorable group cominations

Pros of sexual reproduction

• a lot of genetic diversity (adaptation)

• breaks up deleterious combinations

Gametogenisis

process that produces gametes (spermatogenesis and oogenesis)

Germ cells

diploid cells that can use meiosis to make gametes

Polar bodies

small cells produced by unequal division—female meiois

Sertoli cells (nurse cells)

somatic cells that assist sperm production

Inerstitial cells (Leydig cells)

somatic cells that secrete testosterone (endocrine cells)

Spermatozoon head contains:

• nucleus

• acrosome

• lysosome

• enzymes

• basal body of the flagellum

Spermatozoon tail contains:

• mid piece

  • large mitochondria—to power the flagellum

• principal piece

• end piece

Ovarian folicle

developing ovum and support cells (mature egg cell surrounded by support cells)

• multiple grow together until one dominant follicle is released

Fertilization challenges

• sperm and egg need to be brought together

• estrus/heat → time of ovulation

• polyspermy

Steps of fertilization

1. acrosomal process formed (Ca²+)

2. release of digesting enzymes

3. nucleus of sperm cell enters ovum

4. sperm organelles degraded

Fast block

a rapid, temporary electrical change in the egg's plasma membrane that prevents additional sperm from fusing with the egg immediately after the first sperm binds

Slow block

• Ca²+ is released (promotes exocytosis)

• Cortical granules release contents

• Forms fertilization envelope

Hermaphrodites

sex change as an adult

• produces both sperm and ova

• Some sequential

• E.g. clownfish

Sperm pathway

1. testes

2. epididymis → where most of the sperm is developing

3. vas deferens → tubes

4. ejaculatory duct

5. uretra

Seminal vescilces

fluid and energy sources for semen

prostate gland

alkaline buffer, sperm activation for semen

bulbouretral gland

mucus/lubricant for semen

Spontaneous ovulation

• ovulation controlled by hormones

• timed cycles

• large element of chance

Induced ovulation

• triggered by copulation

• neurons send signals to hypothalamus

• GnRH release → FSH and LH

What does the blastocyst do if there is a pregnancy?

burrows into the uterine wall and releases CG hormone that stimulates the corpus luteum

What does the corpus luteum do?

produces progesterone, which supports the early stages of pregnancy

Linked steps for reproduction

mating → fertilization → embryonic development → birth

• conditions not coordinated with the environment

Decouple reproduction

Time between steps is flexible, and it allows more environmental coordination

What is a component of decoupling reproduction?

sperm storage

Embryonic diapause

state of arrested/slowed embryonic development

• adjustment of fertilization and completion of embryonic development

Semelparous

reproduces only once, usually found in animals that produce thousands of offspring at a time (some organisms die afterwards)

Why is semelparity rare in mammals?

mammals don’t reproduce as many offspring at a time (very limiting)

Iteroparous

capable of 2+ periods of reproduction during their lifetime

• must survive after reproduction

Bet-hedging

Instead of putting all their "eggs in one basket" to chase the highest average reward, they trade some short-term performance for long-term survival

Photoperiod

amount of daylight can influence cellular processes

Long-day breeders

animals in this category become reproductively active when day length lengthens (spring and summer), ensuring their young are born when food and warmth are plentiful