Biology slides 6
Endocrine System
Regulates homeostasis and other physiological processes through slow, long-lasting effects.
Hormones
Chemical signals released by the endocrine system from glands into the blood that travel throughout the body and act on specific target cells by binding to specific receptors.
Signaling mechanism of the Endocrine System
Chemical.
Primary chemical signal of the Endocrine System
Hormones.
Distance traveled by Endocrine signals
Long or short.
Response time of the Endocrine system
Fast or slow.
Environment targeted by the Endocrine System
Internal.
Signaling mechanism of the Nervous System
Chemical/electrical.
Primary chemical signal of the Nervous System
Neurotransmitters.
Hormone
A chemical messenger that influences cellular behaviours and can alter protein levels.
Hormone diversity
The existence of many different hormones, including lipids, proteins, and others, each have distinct properties and targets.
Endocrine gland
A gland that releases hormones into the bloodstream to regulate various bodily functions.
Growth Hormone (GH)
A protein hormone from the anterior pituitary that promotes growth of body tissues.
Prolactin (PRL)
A peptide hormone from the anterior pituitary that promotes milk production.
Thyroid-Stimulating Hormone (TSH)
A glycoprotein hormone from the anterior pituitary that stimulates thyroid hormone release.
Adrenocorticotropic Hormone (ACTH)
A peptide hormone from the anterior pituitary that stimulates hormone release by the adrenal cortex.
Follicle-Stimulating Hormone (FSH)
A glycoprotein hormone from the anterior pituitary that stimulates gamete production.
Luteinizing Hormone (LH)
A glycoprotein hormone from the anterior pituitary that stimulates androgen production by gonads.
Antidiuretic Hormone (ADH)
A peptide hormone from the posterior pituitary that stimulates water reabsorption by kidneys.
Oxytocin
A peptide hormone from the posterior pituitary that stimulates uterine contractions during childbirth.
Thyroxine (T4) and Triiodothyronine (T3)
Amine hormones from the thyroid that stimulate basal metabolic rate.
Calcitonin
A peptide hormone from the thyroid that reduces blood Ca2+ levels.
Parathyroid Hormone (PTH)
A peptide hormone from the parathyroid that increases blood Ca2+ levels.
Aldosterone
A steroid hormone from the adrenal cortex that increases blood Na+ levels.
Cortisol, corticosterone, cortisone
Steroid hormones from the adrenal cortex that increase blood glucose levels.
Epinephrine and norepinephrine
Amine hormones from the adrenal medulla that stimulate the fight-or-flight response.
Melatonin
An amine hormone from the pineal gland that regulates sleep cycles.
Insulin
A protein hormone from the pancreas that reduces blood glucose levels.
Glucagon
A protein hormone from the pancreas that increases blood glucose levels.
Testosterone
A steroid hormone from the testes that stimulates development of male secondary sex characteristics and sperm production.
Estrogen and progesterone
Steroid horomones from the ovaries that stimulate development of female secondary sex characteristics and prepare the body for childbirth.
Homeostasis
The body's process of maintaing ideal physiological values for various factors, monitored through set points.
Dynamic Equilibrium
Maintaining optimal internal conditions as a fluctuating process.
Stressor
An external factor or stimulus that disrupts homeostasis.
Receptor
A component that perceives the stressor.
Afferent Conductor
Sends information from the receptor to a control center.
Control Center
Processes information received from the afferent conductor and decides on a response.
Efferent Conductor
Sends a signal from the control center to an effector.
Effector
Where the appropriate response to the stressor takes place.
Negative Feedback
Homeostatic mechanisms that counter the stressor's effect to return a variable to its set point.
Positive Feedback
A mechanism that accelerates a response to overcome a stressor, amplifying a change to push a process to completion.
Example of Negative Feedback
If stimulus causes an increase and response is a decrease.
Example of Positive Feedback
If stimulus causes an increase and response is also an increase.
Homeostatic Systems
The Nervous System and the Endocrine System as principal conductors.
Effectors
Various systems used to respond to stressors in homeostasis.
Childbirth
An example of a dangerous process sped up by positive feedback.
Endocrine Glands
Glands that secrete hormones.
Thyroxine (T4), triiodothyronine (T3)
Stimulate basal metabolic rate.
Epinephrine, norepinephrine
Stimulate fight-or-flight response.
Hypothalamus
Links the Nervous System and the Endocrine System, regulates the release of other hormones from the Pituitary and Adrenal glands.
ADH (antidiuretic hormone)
Stimulates fluid reabsorption by kidneys, inhibited by alcohol and caffeine.
Oxytocin (cuddle hormone)
Promotes empathy, nurturing/bonding, and childbirth.
Pituitary
Releases 9 different hormones to influence most of the other endocrine organs.
ADH
Antidiuretic hormone released from the posterior pituitary.
TSH
Thyroid-stimulating hormone released from the anterior pituitary.
FSH
Follicle-stimulating hormone released from the anterior pituitary.
LH
Luteinizing hormone released from the anterior pituitary.
Pancreas
An endocrine and exocrine organ that produces hormones and digestive enzymes.
Exocrine
Secrete hormones into ducts to be transported elsewhere, ex: sweat, salivary, mammary glands.
Diabetes Mellitus Type 1
Deficiency in pancreatic cells so they do not produce sufficient insulin.
Diabetes Mellitus Type 2
Often related to lifestyle diet, where the liver becomes desensitized to insulin.
Thyroid Gland
Located in the neck and secretes hormones that influence metabolism, growth, and development.
Thyroid hormone
A mix of T3 and T4, hormones that influence various bodily functions.
T3
One of the thyroid hormones that influences metabolism and development.
T4
Another thyroid hormone that influences metabolism and development.
Negative Feedback loop
A mechanism where T3 and T4 inhibit the hypothalamus and pituitary from secreting hormones that signal for the thyroid gland to produce more T3 and T4.
Gonads
Ovaries and testes are gonads.
Hormones from Gonads.
Both secrete hormones important for the reproductive system.
Pituitary Influence
They are under the influence of hormones secreted from the pituitary.
Follicle Stimulating Hormone (FSH)
FSH stimulates formation of egg or sperm.
Gonadotropin Release Hormone (GnRH)
Hypothalamus directs pituitary with gonadotropin release hormone (GnRH).
Male Hormonal Regulation
FSH causes Sertoli cells in Seminiferious tubules to increase sperm production and produce the inhibin hormone.
Inhibin
Inhibin performs negative feedback on the pituitary.
Leydig Cells
LH causes Leydig cells (which surround sperm-producing seminiferious tubules) to produce testosterone.
Male Characteristics
Testosterone also develops and maintains certain male characteristics (ex: penis growth, development of testes, bone mass and muscle distribution, hair development).
Female Hormonal Regulation
FSH causes Follicle cells to stimulate egg (oocyte) development, and produce the inhibin and estrogen hormones.
Ovulation
LH triggers release of oocyte (ovulation), and causes the follicle to become a corpus luteum which produces progesterone.
Hormone Levels Cycle
Hormone Levels CYCLE!!!
Estrogen
Estrogen develops and maintains certain female characteristics (ex: development of external genitalia, bone mass and muscle distribution, hair development, breast development).
Menopause
With age, ovaries become less responsive to LH and FSH, until they stop responding (menopause).
Andropause
Men experience andropause, which is due to a decrease in sex hormone production, affecting some traits (loss of muscle/bone, reduced sex-drive, fertility).
Follicular Phase
Follicular phase (~14 days) is when FSH causes follicles to mature, and estrogen prepares the uterus and promotes LH release.
Ovulation Phase
Ovulation (~day 14) occurs when LH peaks, and follicle then becomes corpus luteum.
Luteal Phase
Lutel phase (~days 15-28) is when corpus luteum secretes progesterone to continue to prepare uterus' endometrial lining.
Menstruation
Corpus luteum stops producing hormones after a few weeks, causing endometrial lining to be discarded and cycle restarts (menstruation)... UNLESS fertilization happens (causing various other hormones to be released).