quizzy poo Flashcards
Know that the hypothalamus controls hormonal secretions by the anterior and posterior pituitary.
-Hypothalamus is link between endocrine system and nervous system
-Understand that the hypothalamus controls hormone secretion by the
anterior and posterior lobes
of the pituitary gland, and that
hormones secreted by the
pituitary gland control growth,
developmental changes,
reproduction, and homeostasis.
TSH
- TSH (thryoid-stimulating hormone): Targets cells of the thyroid to make and secrete thyroxine
HGH
- Growth hormone: Targets cells throughout the body; stimulates mitosis
-acts directly on adipose tissue (reduces adipose cells)
-acts indirectly on muscles/ bones (increases mass/ growth) - does this by activating IGF (insulin growth factor) in liver; IGF increases bone growth and muscle mass
-short half life, small, naturally occuring
Oxytocin
- Oxytocin: Produced in neurosecretory cells in hypothalamus but stored in/ secreted from posterior pituitary; Targets cells of the uterine muscles and mammary glands, causing contractions (for birth) and milk secretion (note that nursing then causes oxytocin to be released to allow milk to be secreted too)
FSH
- FSH (follice-stimulating hormone): Targets cells of the gonads in males and females. In males causes meiotic divisions to produce spermatocytes. In females it causes maturation of an oocyte.
Prolactin
- Prolactin: Targets cells of the mammary glands causing them to grow and produce milk
LH
- LH (luteinizing hormone): Targets cells of the gonads in males and females. In males it causes Leydig cells to make and secrete testosterone (for sperm production). In females, it causes ovulation of an oocyte.
Compare and contrast hormonal and nervous communication (in the body). (CONTRAST)
Hormones
- Chemical (messenger)
Messenger (hormones) transported in blood
Slower
Carried throughout body
Wide range of organs/ tissues affected
Long-term/ persistent response (usually)
Nerves
Electrical (nerve impulse)
Signal transported by neurons
Faster
Carried to single/ specific cell/ muscle fibre
Only muscles/ glands receive signals
Short-term/ short-lived response
Explain the role of melatonin in circadian rhythms.
-Melatonin: produced in pineal gland of brain in response to changes in light.
-Function – Controls/regulates 24-hr circadian rhythm/ biological clock (the body’s physiological responses to the 24-hour day-night cycle of activity).
Melatonin affects sleep-wake cycles and
seasonal reproduction
-Promotes sleep in diurnal animals (like us)
-Promotes activity in nocturnal animals
-As we age, melatonin levels naturally decrease
-Production/ amount of melatonin secreted is controlled by amount of light detected by the retina.
Compare and contrast steroid and peptide hormones (with regard to structure, mode of action, and effect). (compare)
Both
Act on target cells/ organs
Travel through the bloodstream
Effective at very low concentrations
Effects last longer than neurotransmitters
Compare and contrast steroid and peptide hormones (with regard to structure, mode of action, and effect). (pep)
Peptide
- Amino acids (proteins/ water soluble/ polar)
-Do not enter target cells because they cannot pass through plasma membrane, so they bind to receptors on plasma membrane
-Binding of hormones to receptors activates a chain of reactions, carried out by secondary messengers in cytoplasm (such as cAMP), which activates or inhibits enzymes/changes cell’s physiology such as protein kinase in cell.
-ATP is needed
Explain the role of thyroxin and the causes and consequences of thyroxin deficiency.
-thyroxin contains iodine
-prolonged deficiency to iodine causes lack of thyroxin in body
- iodine deficiency causes the thyroid gland to become enlarged (trying to compensate for iodine deficiency), resulting in a disease known as goitre
not enough thyroxin
= hypothyrodism:
Some of the symptoms are weight gain, loss of energy, feeling cold all the time, forgetfulness and depression, stunted growth, stunted mental development
too much thyroxin
= hyperthyrodism:
Some of the symptoms include excessive sweating/ hunger, hyperactivity, mood swings, rapid heart rate, difficulty sleeping, weight loss, muscle weakness/ tremors
ADH
- ADH (Antidiuretic hormone): Targets cells of the kidney, increasing the amount of water that is reabsorbed into the blood
Compare and contrast steroid and peptide hormones (with regard to structure, mode of action, and effect). (STEROID)
Steroid
- Cholesterol (lipid soluble/ nonpolar)
-Pass through plasma membrane of target cells (steroids are small and hydrophobic.
- Hormones bind to receptor proteins and form a receptor-hormone complex - these receptor proteins are often gene regulatory proteins
-Receptor hormone complex moves into nucleus, and regulates gene expression/acts directly on dna/ binds to it which promotes or inhibits transcription of specific genes, drastically altering biochemistry of cell
-Does not require use of ATP
Explain the roles of the hypothalamus thermoregulation.
body temp too low
-hypothermia (<32C)
-Hypothalamus releases chemical signals that trigger:
Vasoconstriction (arterioles get smaller, blood is diverted to deep tissues/ organs, less heat loss)
Shivering of skeletal muscle (generates heat)
“Goosebumps” – raises hair follicles on skin (traps heat/ insulates against heat loss)
body temp too high
-Hyperthermia (>40C)
-Hypothalamus releases chemical signals that trigger:
-Vasodilation (arterioles get bigger, fill with blood, transfer heat to skin and out of body)
Increased sweat gland activity (evaporative cooling)
Explain the roles of the thyroid gland thermoregulation.
more heat, hypothalamus inhibits release from thyroid: less thyroxin
-decreases metabolic rate so body temp drops
vs
less heat, more thyroxine released from thyroid as hypothalamus stimulates it to increase reactions inside of body: Causes increased oxygen consumption and the hydrolysis of ATP; thereby causing an increase in the body’s temperature
-increases metabolic rate so body temp rises
Explain the causes and treatments of jet-lag.
causes:
caused by the body’s inability to rapidly adjust to a new time zone (following extended air travel through multiple time zones)
The pineal gland continues to secrete melatonin according to the “old” time zone schedule
treatments:
Taking melatonin supplements (artificially increasing melatonin levels in the body) around the sleep time of the new time zone can help to alleviate symptoms of jet lag and help the body adjust to the new time zone faster
Contrast how neurosecretory cells are linked to the anterior and posterior pituitary and cause the anterior and posterior pituitary to release hormones into the blood.
Posterior Lobe
-The POSTERIOR LOBE
(neurohypophysis) is
controlled by
neurosecretory cells of the
hypothalamus
-Cell bodies and dendrites
of neurosecretory cells are
located in the hypothalamus.
Their axons extend down into
the posterior pituitary.
-Cell bodies (of posterior pituitary neurosecretory cells) produce hormones (ADH, oxytocin) which travel down the axons of these cells into the posterior pituitary to be released directly into the bloodstream when needed.
Anterior
-The ANTERIOR PITUITARY
(adenohypophysis) is
controlled by
neurosecretory cells in the
hypothalamus that are
linked to it through portal
systems of blood vessels
-Capillaries in the
hypothalamus carry
“releasing” and “release-
inhibiting” hormones from
the hypothalamus through
a portal vein which branches
into another network of capillaries in the anterior pituitary.
-The anterior pituitary releases its hormones into the bloodstream when “releasing” hormones are received from the hypothalamus and stops releasing its hormones when “release-inhibiting” hormones are received
Compare and contrast hormonal and nervous communication (in the body). (COMPARE)
Similarities (between hormone/ the endocrine system and nerves/ the nervous system)
Both use chemicals that bind to receptors (hormones/ neurotransmitters are both chemicals)
Both used for COMMUNICATION between cells/ tissues/ organs in the body
Both cause a response or change in target cells
Both can stimulate or inhibit processes in target cells
Both can work/ cause changes over long distances (between widely separated parts of body)
Both use feedback mechanisms to maintain homeostasis
Both under (overall) control of brain/ CNS
