Human Physiology Exam 4

gastrin - secretion

hormone secreted by G cells in the stomach or duodenum (small intestine) in response to presence of proteins

gastrin - function

hormone

stimulates gastric acid secretions and pepsin

promotes gastric motility

helps prepare for/helps process food in digestive system - “turns on” the stomach

gastrin - aid

hormone

helps prepare for/helps process food in digestive system - “turns on” the stomach

cholecytokinin (CCK) - secretion

hormone secreted by I cells in the duodenum or jejunum (small intestine) stimulated by amino acids and fat

cholecytokinin (CCK) - function

hormone

• slows gastric emptying

• promotes satiety

• stimulates bile release

• stimulates exocrine pancreatic enzyme secretion

cholecytokinin (CCK) - aid

hormone

helps digest fats and proteins in small intestine

secretin - secretion

hormone secreted by S cells in duodenum (small intestine) stimulated by acid

secretin - function

hormone

stimulates bicarbonate secretion

increases bile production in liver 

inhibits gastric acid secretion

inhibits gastric motility

glucose-dependent insulinotropic peptide (GIP) - secretion

hormone secreted by K cells in duodenum or jejunum (small intestine)

glucose-dependent insulinotropic peptide (GIP) - function

hormone

stimulates insulin release from pancreas in response to nutrient digestion

glucose-dependent insulinotropic peptide (GIP) - aid

hormone that helps tell the pancrease to release insulin during digestion (especially glucose and fat)

motilin - secretion

hormone secreted by M cells in small intestine

motilin - function

hormone

promotes motility during fasting

initiates migrating motor complexes (MMC) during fasting

clears stomach and small intestine using peristalsis

motilin - aid

helps clear the gut

“housekeeping” hormone

trypsinogen/trypsin -secretion

hormone secreted by pancreas (pancreatic acinar cells) into the duodenum (small intestine)

activated by enterokinase

trypsinogen/trypsin - function

hormone

breaks peptide bonds in proteins into short peptides and amino acids for absorption

“master activator” for other pancreatic enzymes

trypsinogen/trypsin - aid

helps digest proteins

enterokinase

enzyme that activates typsinogen into trypsin

bound to membrane of luminal surface of duodenal cells

pepsinogen/pepsin - secretion

enzyme secreted by chief cells in stomach gastric glands

activated by very acidic pH (pH 1-2) or HCL from parietal cells

pepsinogen/pepsin - function

enzyme that begins protein digestion in stomach

amylase - secretion

enzyme secreted by salivary glands or pancreatic acinar cells

amylase - function

enzyme that digests carbohydrates, specifically starches (long chains of glucose) into smaller sugars

proteases

enzymes that helps digest proteins into smaller peptides and amino acids

secreted by pancreatic acinar cells

lipase and colipases

enzymes that help digestion of fats

secreted by pancreatic acinar cells

brush border enzymes

enzymes located on microvilli of small intestine (mainly duodenum and jejunum)

complete final steps of digestion, producing molecules small enough to be absorbed

produced by enterocytes

“finishers” of digestion

hydrochloric acid (HCL) - secretion

acid secreted by parietal cells in stomach linings

hydrochloric acid (HCL) - function

creates acidic environment - this helps activate pepsinogen

denatures proteins so digestive enzymes can access peptide bonds easier

assists in mechanical and chemical digestion

stimulates hormone release - somatostatin (inhibits digestion when acid is too high) and secretin in duodenum

Stimulus: Stretch

Effect on GI Smooth Muscle: Contraction

• activates myogenic reflect via mechanoreceptors

Stimulus: Acetylcholine (ACh)

Effect on GI Smooth Muscle: Contraction

• activates muscarinic receptors = increased Ca2+ sensitivity

Stimulus: Epinephrine

Effect on GI Smooth Muscle: Relaxation

• activates beta2-andregenic receptors = decreased Ca2+ sensitivity

Stimulus: Atropine

Effect on GI Smooth Muscle: Relaxation

• blocks muscarinic receptors = inhibits ACh-mediated contraction

Stimulus: Elevated Extracellular K+

Effect on GI Smooth Muscle: Depolarization leading to Contraction or Tentany

• alters membrane potential

Stimulus: BaCl

Effect on GI Smooth Muscle: Affects Membrane Potential = Contraction

• blocks K+ channels = depolarizes smooth muscle = opens voltage-gated Ca2+ channels

Parietal Cells

release HCl and intrinsic factor

intrinsic factor

vitamin B12 absorption

chief cells

secrete pepsinogen

mucous cells

secrete mucus and bicarbonate (HCO3) which protect the mucosa

somatostatin - secretion

hormone secreted by D cells in the stomach, duodenum, pancreas, and brain (hypothalamus)

Stimulated by acidic pH in stomach, sympathetic stimulation, presence of nutrients in the small intestine, and other hormones

somatostatin - function

hormone

Inhibitory peptide hormone that slows down digistive processes

• inhibits gastric secretions

• inhibits pancreatic secretions

• inhibits GI motility

• inhibits blood flow to GI tract

somatostatin - aid

hormone

helps protect the stomach by preventing excessive digestion

Anti-Diuretic Hormone (ADH) - source

hormone released from the hypothalamus and stored in the posterior pituitary

release controlled primarily by plasma osmolarity and blood volume/pressure

Anti-Diuretic Hormone (ADH) - function

hormone

• increases water reabsorption in renal collecting ducts

• increases number of aquaporin-2 channels

Anti-Diuretic Hormone (ADH) - aid

hormone

helps maintain body water balance, stabilize blood pressure, and prevents excessive water loss

hydration and blood pressure

Andrenocorticotropic Hormone (ACTH) - source

tropic hormone in the anterior pituitary

Andrenocorticotropic Hormone (ACTH) - function

tropic hormone

stimulates zona fasciculata of the andrenal cortex to secrete cortisol

control secretion of another endocrine gland

Andrenocorticotropic Hormone (ACTH) - aid

tropic hormone

helps with long-term stress responses, maintaining glucose availability, permissive effects for catecholamines (blood pressure maintenance)

stress response

Corticotropin-Releasing Hormone (CRH) - source

hormone from the hypothalamus

Corticotropin-Releasing Hormone (CRH) - function

hormone

stimulates the anterior pituitary to release Andrenocorticotropic Hormone (ACTH)

Corticotropin-Releasing Hormone (CRH) - aid

hormone

helps initiate the entire HPA axis response, integrates emotional and physical stress signals

activating HPA axis

Growth Hormone (GH) - source

hormone form the anterior pituitary

Growth Hormone (GH) - function

hormone

Direct-action: anti-insulin effects, increased lipolysis, increased blood glucose

Indirect-action: done through IGF-1, mediates growth of bone, cartilage, and soft tissues

Growth Hormone (GH) - aid

hormone helps with linear bone growth in childhood, maintenance of muscle mass, energy mobilization during fasting

bone and muscle growth

Growth Hormone-Releasing Hormone (GHRH) - source

hormone from the hypothalamus

Growth Hormone-Releasing Hormone (GHRH) - function

hormone

stimulates growth hormone secretion from the anterior pituitary

Growth Hormone-Releasing Hormone (GHRH) - aid

hormone

helps promote growth and maintaining growth hormone pulses (circadian rhythm)

growth regulation

Insulin-Like Growth Factor 1 (IGF-1) - source

hormone mostly from the liver but also skeletal muscle

stimulated by growth hormone

Insulin-Like Growth Factor 1 (IGF-1) - function

hormone

mediates most of growth hormone’s gorwth-promoting actions

• cell division

• bone elongation

• protein synthesis

provides negative feedback to inhibit GH and GHRH

Insulin-Like Growth Factor 1 (IGF-1) - aid

hormone that helps with growth during childhood, tissue maintenance and repair

long-term growth

Somatostatin (SS) - source

hormone from the hypothalamus but also the pancreas and GI tract

Somatostatin (SS) - function

hormone

Inhibits:

• thyroid-stimulating hormone (TSH)

• glucagon

• many GI hormones secreted from peripheral tissues

Somatostatin (SS) - aid

hormone that helps hormone balance

• prevent excessive hormone secretion

• acts as a general “brake” in metabolic and digestive systems

Thyrotropin-Releasing Hormone (TRH) - source

hormone from the hypothalamus

Thyrotropin-Releasing Hormone (TRH) - function

hormone

• stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH)

Thyrotropin-Releasing Hormone (TRH) - aid

hormone that helps control the thyroid axis and maintaining metabolic homeostasis

thyroid control

Thyroid-Stimulating Hormone (TSH) - source

tropic hormone from the anterior pituitary

Axis: TRH → TSH → Thyroid → T3/T4

Thyroid-Stimulating Hormone (TSH) - function

tropic hormone

• increases iodide uptake

• increases thyroid hormone sythesis

• increases thyroid gland growth (tropic effect)

Thyroid-Stimulating Hormone (TSH) - aid

tropic hormone that helps regulate energy expenditure and maintaining normal metabolic rate

setting metabolic rate

Thyroid Hormone (T3 and T4) - source

hormone from thyroid follicular cells

Thyroid Hormone (T3 and T4) - function

hormone that increases:

• basal metabolic rate

• heat production

• heart rate and cardiac output

• protein synthesis

• nervous system development (critical for children)

has permissive effects on catecholamines

Thyroid Hormone (T3 and T4) - aid

hormone that helps overall metabolic homeostasis, growth and CNS developement, and thermoregulation

growth and temperature control

Gonadotropin-Releasing Hormone (GnRH) - source

hormone from the hypothalamus

released in a pulsating manner into the hypophyseal portal system

Gonadotropin-Releasing Hormone (GnRH) - function

hormone

• stimulates the anterior pituitary to release gonadotropins (FSH and LH)

Gonadotropin-Releasing Hormone (GnRH) - aid

hormone that helps maintain puberty and reproductive hormone regulation

• initaite and control sexual development at puberty

• regulate the menstrual cycle in females and spermatogenesis in males

• maintains normal reproductive hormone production

Follicle-Stimulating Hormone (FSH) - source

hormone from the anterior pituitary

Follicle-Stimulating Hormone (FSH) - function

hormone

In Females:

• stimulates growth and maturation of ovarian follicles

• promotes estrogen production by granulosa cells

In Males:

• stimulates sertoli cells in the testes

• supports sperm production (spermatogenesis)

Follicle-Stimulating Hormone (FSH) - aid

hormone that helps regulate fertility and works together with LH to coordinate normal reproductive function

fertility, estrogen production, and spermatogenesis

Luteinizing Hormone (LH) - source

hormone from the anterior pituitary gland

Luteinizing Hormone (LH) - function

hormone

In Females:

• causes ovulation

• stimulates formation of the corpus luteum which secretes progesterone

• supports estrogen production along with FSH

In Males:

• stimulates leydig cells to produce testosterone

Luteinizing Hormone (LH) - aid

hormone that helps fertility, menstrual cycle regulation, male sex hormone production

In Females: maintain ovulation, fertility, and early pregnancy (via progesterone)

In Males: support normal testosterone levels, along with being essential for sperm development, libido and secondary sex characteristics

Inhibin - source

hormone that comes from the ovaries’ granulosa cells in females and testes’ sertoli cells in males

Inhibin - function

hormone

provides negative feedback to the anterior pituitary to inhibit FSH secretion

does not significantly affect LH

Inhibin - aid

hormone that helps maintain hormonal balance in the reproductive system and regulate gamete production

In Females: regulate follicle developement and menstrual cycle dynamics

In Males: maintain stable sperm production by preventing over-stimulation of sertoli cells

Human Chorionic Gonadotropin (hCG) - source

hormone from synctiotrophoblast cells of the early placenta

appears very early in pregnancy

what pregnancy tests use to give a positive reading

Human Chorionic Gonadotropin (hCG) - function

hormone

• maintains corpus luteum in early pregnancy

• stimulates continued secretion of progesterone by acting on LH receptors in ovary

• supports placental growth and early uterine blood supply

• helps maternal immune tolerance of the embryo

Human Chorionic Gonadotropin (hCG) - aid

hormone that helps in the early stages of pregnancy - implantation, prevention of menstruation, maintenance of pregnancy until placenta takes over hormone production

Progesterone - source

hormone from:

• corpus luteum during early pregnancy and luteal phase of ovarian cycle

• placenta after 10-12 weeks of pregnancy

Progesterone - function

hormone

• maintains + stabilizes endometrium

• prevents uterine contractions by relaxing smooth muscle

• thickens cervical mucus to block bacteria and sperm entry

• supports breast development for future milk production

• raises basal body temperature after ovulation

• modulates maternal immunity to protect fetus

Progesterone - aid

hormone that helps:

• maintenance and protection during pregnancy

• creates a protective environment in cervical and uterus