Flashcards in March 11, 2015 --> 106-120 Deck (43):
What is relaxin?
A hormone produced by the ovary and the placenta with important effects in the female reproductive system and during pregnancy. In preparation for childbirth, it relaxes the ligaments in the pelvis and softens and widens the cervix
Action of Testosterone
Promotes the development of male reproductive system and male secondary sexual characteristics
Action of Estrogen
Promotes the development of female reproductive system, female breasts and female secondary sexual characteristics
Action of Progesterone
Stimulates secretion of "uterine milk" by the uterine endometrial glands and promotes development of secretory apparatus of breasts
Action of Human chorionic gonadotropin (hCG)
Promotes growth of corpus lute and secretion of estrogens and progesterone by corpus luteum
What is the source of hCG?
Chorion (Fetal tissue component of the placenta)
Source of progesterone
Somatostatin does what?
- Inhibits secretion of growth hormone from the pituitary gland
- Acts locally within the islets of Langerhans themselves to depress the secretion of insulin and glucagon
- Inhibits the secretion of many of the other GI hormones including gastrin, cholecystokinin, secretin and vasoactive intestinal peptide.
Prolactin is secreted by what cells in what structure?
By lactotropes in the anterior pituitary
Describe the regulation of Prolactin
Under normal conditions, large amounts of dopamine (prolactin inhibitory factor) are continually transmitted to the anterior pituitary gland so that the normal rate of prolactin secretion is light.
**This is why prolactin is said to be under predominant inhibitory control
Factors that increase prolactin secretion
Stress, thyrotropin-releasing hormone
Factors that decrease prolactin secretion
Bromocriptine (dopamine agonist), TSH and GH
5 classes of steroid hormones
What three hormones regulate the distribution of [Ca2+] between bone and extracellular fluid (ECF) and thereby regulate plasma calcium
Calcitriol is stimulated by what?
Calcitonin is secreted in response to what?
Calcitriol: hypocalcemia and hypophosphatemia
Is calcitonin required in adult humans?
No, although it is important during bone development, the major regulator of plasma calcium levels in the adult is parathyroid hormone
List the hormones of the thyroid and parathyroid glands
1. Triiodothyronine (T3)
2. Tetraiodothyronine or Thyroxine (T4) [usually converted to T3]
4. Parathyroid hormone
Thyroid-stimulating hormone is produced and secreted from what gland?
Antidiuretic hormone is also called what? and is secreted from where?
Also known as vasopressin
- Secreted from posterior pituitary
Hormone is produced and packaged in secretory vesicles within hypothalamic neurons to be released upon hormone secretion.
Single most important effect of antidiuretic hormone
To conserve body water by reducing the loss of water in urine
How does antidiuretic hormone stimulate water reabsorption?
By stimulating insertion of "water channels," or aquaporins, into the membranes of kidney tubules
The most important variable regulating antidiuretic hormone secretion is?
Plasma osmolarity, or the concentration of solutes in blood. The osmolarity is sensed in the hypothalamus by neurons known as an osmoreceptor
What are the three general classes of hormones
1. Proteins and polypeptides
3. Derivatives of the AA tyrosine
Protein and polypeptide class of hormones might be found be released from what place in the body?
Includes hormones secreted by anterior and posterior pituitary, pancreas, the parathyroid gland and many others
Steroid class of hormones are found being released from where in the body?
Secreted by adrenal cortex (cortisol & aldosterone), ovaries (estrogen & progesterone), the testis (testosterone) and the placenta (estrogen and progesterone)
Derivatives of the AA tyrosine are found being secreted by what place in the body?
Secreted by the thyroid (T4,T3) and the adrenal medullae (epinephrine and norepinephrine)
Most of the hormones in the body are of what class?
Polypeptides and proteins
T or F, All cells have a resting potential
Depolarization of a membrane occurs when what channels are open?
Sodium channels, allowing sodium to move to an area of lower concentration inside the cell which reverse the polarity to an inside-positive state.
During what part of the stroke of the action potential does it depolarize or become less negative?
During the upstroke
T or F, nerve fibers of the CNS are enclosed by a neurilemma
False, they are not. This is why regeneration of severed axons is more difficult in the CNS (brain and spinal cord)
T or F, not all axons of the PNS have a sheath of Schwann cells around them
False, All axons of PNS do have a sheath
T or F, Right-sided lesions of the spinal cord result in loss of motor activity on the opposite or contralateral side and pain and temperature sensations on the same or ipsilateral side
False, Same side = loss of motor activity
Opposite side = pain and temperature sensations
Function of Lateral spinothalamic tract
Pain, temperature and crude touch; opposite side
Function of Anterior spinothalamic tract
Crude touch and pressure
Function of Fasciculi gracilis and cuneatus tract
Discriminating touch and pressure sensations
Function of Anterior and posterior spinocerebellar tract
Termination of the four ascending tracts of the spinal cord (4)
Lateral spinothalamic = Thalamus
Anterior spinothalamic = Thalamus
Fasciculi gracilis and cognates = Medulla
Anterior and posterior spinocerebellar = Cerebellum
What are the two forms of summation by which an excitatory postsynaptic potential may combine to reach threshold and initiate an action potential
1. Spatial summation (2 excitatory inputs arrive simultaneously)
2. Temporal summation (2 excitatory inputs arrive in rapid succession)
Saltatory conduction is of value for what 2 reasons?
1. Increases velocity of nerve transmission in myelinated fibers
2. Conserves energy for the axon because only the node depolarizes. Thus, it takes less energy for the sodium/potassium ATPase to re-establish resting ion gradients
Conduction velocity depends on what 2 things?
1.Diameter of the nerve fiber - Larger = faster
2. Presence of myelin sheet = faster
Which important small-molecule transmitters are involved in an excitatory effect on nerves?
4. Nitric oxide