Endocrine System: Hypothalamus, Pituitary, and Hormonal Regulation

what are the 3 functional anatomy of the hypothalamus to pituitary?

Hypothalamus -> Master regulator

AP -> makes and releases own hormones

PP -> releases hormones hypothalamus makes

2 hormones of the posterior pituitary

ADH and oxytocin. ADH -> increases water retention, Oxytocin -> uterine contraction and milk ejection

6 major hormones of anterior pituitary

GH, TSH, ACTH, LH, FSH, Prolactin

thyroid hormone function

increase metabolic rate, increase oxygen consumption, increase heat production

TSH effects

stimulate thyroid growth, increase t3/t4 production

How to target cell responsiveness?

increase # of receptors, increase receptor sensitivity, increase hormone concentration

Signal Transduction pathways in endocrine?

Membrane receptors (fast) -> peptide hormones

Intracellular (slower, longer lasting) -> steroid/thyroid

Hypophyseal Portal System

Links hypothalamus to anterior pituitary. It allows for fast, direct, and concentrated hormone delivery

Circadian Rhythm

Controlled by SCN, syncs body to light and dark cycles

Melatonin

Released by pineal gland, helps regulate the sleep cycle, makes the body sleepy, released more when its dark

Adrenal Gland Anatomy

Cortex (outside) - steroids

Medulla (inner) epinephrine

3 Zones of Adrenal Cortex

Zona Glomerulosa -> aldosterone

Zona Fasciculata -> Cortisol

Zona Reticularis -> Androgens

Adrenal cortex function

manages long term stress, regulate metabolism, controls blood pressure

Adrenal medulla function

secretes epinephrine and norepinephrine (fight or flight response)

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

Cortisol

Stress hormone: increases blood glucose, increase protein breakdown, anti inflammatory

Adrenal Cortex Products

Aldosterone, Cortisol, Androgens

Negative Feedback

end hormone shuts off hypothalamus + pituitary. Prevents overproduction

epinephrine synthesis

tyrosine --> dopa --> dopamine --> norepinephrine --> epinephrine

epinephrine secretion

triggered by sympathetic nervous system, released into blood rapidly

Catecholamine Receptors

Alpha -> vasoconstriction

Beta -> increase heart rate, and bronchodilation

Stress responses (fast vs slow)

Fast -> SNS -> Epinephrine

Slow -> HPA Axis -> Cortisol

Fuel Storages

Glucose - glycogen

Fat - triglycerides (adipose)

Protein - muscle

Fasting (short vs long)

Short - glycogen breakdown

Long - gluconeogenesis + fat breakdown

Absorptive vs Postabsorptive

Absorptive (fed) - insulin dominates

Postabsorptive (fasting) - glucagon dominates

Endocrine Pancreas

alpha cells - glucagon

Beta cells - insulin

insulin effects

decreases blood glucose. increase glycogen, fat, protein synthesis

insulin secretion factors

increase glucose, amino acids, and parasympathetic stimulation

Beta Cell mechanism

Glucose → ATP ↑ → K⁺ channels close

Depolarization → Ca²⁺ influx → insulin release

Diabetes Mellitus

Type I → no insulin (autoimmune)

Type II → insulin resistance

Glucagon Effects

↑ blood glucose

↑ glycogen breakdown

↑ gluconeogenesis

Insulin vs Glucagon

Opposite actions

Maintain glucose balance

High-Protein Meal

↑ insulin AND glucagon

Prevents hypoglycemia

Sex determination

XX (female), XY(male)

SRY Gene (Y chromosome)

testes develop = testosterone + AMH

MALE reproductive tract anatomy

Testes → sperm production

Epididymis → maturation

Vas deferens → transport

Accessory glands → semen

Female reproductive tract anatomy

Ovaries → oocytes + hormones

Fallopian tubes → fertilization

Uterus → implantation

Vagina → delivery

3 key processes of spermatogenesis

Mitosis → spermatogonia

Meiosis → haploid spermatids

Spermiogenesis → mature sperm

Sperm maturation

occurs in epididymis. Sperm gains motility and fertilization ability

oogenesis process

Oocytes arrested in prophase I (before birth), resumes at puberty.

Follicle Stages

primordial → primary → secondary → Graafian

Capacitation

change that sperm go through to be able to fertilize the egg (removes inhibitory proteins)

Fertilization and Early development

Occurs in fallopian tube. Sperm + oocyte = zygote

implantation

Blastocyst embeds in endometrium

Requires progesterone

Placenta

organ that nourishes the fetus (nutrient/gas exchange + hormone production - progesterone, estrogen)

Maternal Recognition of Pregnancy

hCG from embryo

Maintains corpus luteum → progesterone continues

triggers for parturition (labor)

increase estrogen, decrease progesterone effects

Menstrual Cycle

Cycle during which an egg develops and is released from an ovary and the uterus is prepared to receive a fertilized egg.

ovarian cycle

The 28 days of the menstrual cycle as they apply to events in the ovary. The ovarian cycle has three subphases: the follicular phase, ovulation, and the luteal phase.

Uterine Cycle

The cycle that prepares the uterus for the growth of an embryo.

Two Cell theory

Theca cells → androgens

Granulosa cells → convert to estrogen

Hormone Effects

Testosterone → male traits

Estrogen → female traits, endometrium growth

Progesterone → maintains uterus

Inhibin → ↓ FSH

Prostaglandins → contractions

Sertoli Cells

Support and nourish developing sperm cells.

LH and FSH effects in males

LH → Leydig → testosterone

FSH → Sertoli → sperm production

LH and FSH effects in females

LH → ovulation + progesterone

FSH → follicle growth

Dominate follicle secretion

Highest FSH sensitivity

Produces most estrogen → suppresses others

Follicular vs Luteal Phase

follicular (before ovulation + estrogen dominant) and luteal (after ovulation + progesterone)

LH Surge

Triggered by high estrogen

Gamete Transport

Sperm: motility + uterine contractions

Egg: cilia + peristalsis

Block to Polyspermy

process that prevents more than one sperm cell from fertilizing an ovum

Lactation Hormones

Prolactin (milk production) and oxytocin (milk ejection).

Mouth

mechanical breakdown + amylase (starts carb digestion)

Esophagus

peristalsis only

peristalysis

wave-like contraction that pushes the food down from the esophagus to the stomach

stomach

protein digestion (pepsin), mixing -> chyme

Duodenum (first part of small intestine)

most chemical digestion (pancreas + bile)

Jejunum (second part of small intestine

major absorption

Ileum (last of small intestine)

bile salts + B12 absorption

Colon

Water + electrolyte absorption

segmentation mixing movement

back and fourth mixing which increases absorption efficiency

4 layers of GI Wall

Mucosa, Submucosa, muscularis externa, serosa

mucosa (inner most GI wall)

epithelial cells (absorption/secretion)

Submucosa

glands + blood vessels + Meissner plexus

muscularis externa

smooth muscle, inner circular layer, outer longitudinal layer

Serosa

outer connective tissue

BER (slow waves)

sets frequency of contractions and generated by interstitial cells of Cajal. Contraction only occurs if threshold is reached (spike potentials Ca2+ influx).

BER for digestive track

Stomach - 3/min

Duodenum 12/min

Ileum - 8/min

enteric nervous system

The nervous system of the gastrointestinal tract. It controls secretion and motility within the Gi tract, and is linked to the central nervous system.

Movement of the small intestine

Mixes food back and fourth and slowly progresses forward in segmentations

Movement in colon

very slow, but done in bulk. High volume for poop and water retrival

movement in Esophagus

no mixing. Rapid transport of bolus via gravity and pressure

movement in stomach

grinding with powerful peristaltic waves to create liquid chyme

2 Plexuses of ENS

Myenteric - motility

Submucosal - secretion

Stomach Motor functions

storage, mixing, and emptying

pancreatic secretions

Amylase, lipase, proteases, bicarbonate

CCK

stimulates gall bladder to secrete bile to emulsify fats in the small intestine (enzyme releases)

Secretin

Digestive hormone that stimulates the pancreas to release bicarbonate to neutralize acid in duodenum.

carbohydrate absorption

Glucose & galactose → Na⁺ cotransport (SGLT)

Fructose → facilitated diffusion (GLUT)

Protein Absorption

Amino acids → Na⁺ cotransport

Small peptides → H⁺ cotransport → broken down inside cell

Lipid Absorption

Bile salts → micelles

Diffuse into enterocytes

Reassembled → triglycerides

Packaged → chylomicrons

Enter lymph (not blood initially)

Bile Salts

cholesterol derivatives that function in fat emulsification and absorption. Made in liver then stored in gallbladder.

Short-chain FA → directly into blood

Long-chain FA → chylomicrons → lymph → blood

Pepsinogen → Pepsin

Activated by HCl

Begins protein digestion

Cholesterol

A type of fat made by the body from saturated fat; a minor part of fat in foods (precursor to steroid hormones)

Phospholipids

A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.

Water & Ion Absorption

Na⁺ actively transported

Water follows via osmosis

Cl⁻ follows electrochemical gradient

mechanoreceptors

Stretches muscular wall, signals peristaltic reflex, regulates gastric emptying

Chemoreceptors

Nutrient sensing, and ph monitoring

Osmoreceptors

the osmolarity of the blood (water homeostasis)

Gastric Motility Regulation

Increased by gastrin and parasympathetic input. Decreased by fat and acid inn duodenum