1. Steriod hormones are a. hydrophilic and free in plasma b. hydrophobic and fre
ID: 32719 • Letter: 1
Question
1. Steriod hormones are
a. hydrophilic and free in plasma
b. hydrophobic and free in plasma
c. hydrophilic protein-bound in plasma
d. hydrophobic and protein-bound in plasma
2. Receptors for non-steriod hormones are
a. on cell membranes
b. in nuclei
c. a and b
Modified true/false question. If the statement is correct answer true. If the statement is not correct, change the bold word(s) to make a correct sentence.
3. The concentration of a given hormone is constant during the day.
4. Hormone release from anterior pituitary is controlled by nerve signals from hypothalamus.
5. Catecholamine is the primary glucocorticoid, leading to the mobilization of free fatty acids (FFA) and breakdown of protein into amino acids.
6. Growth hormone release is proportional to exercise intensity and notably contributes to growth of tissues, organs, and muscle.
Essay question.
7. Explain, in detail, how withdraw reflex is accomplished including involvement of IPSP (inhibitory postsynaptic potential)
Explanation / Answer
1 Steriod hormones are
b. hydrophobic and free in plasma
2. Receptors for non-steriod hormones are
a. on cell membranes
3. The concentration of a given hormone is constant during the day. FALSE
4. Hormone release from anterior pituitary is controlled by nerve signals from hypothalamus.True
5. Catecholamine is the primary glucocorticoid, leading to the mobilization of free fatty acids (FFA) and breakdown of protein into amino acids. True
6 Growth hormone (GH) is a peptide hormone produced by the anterior lobe of the pituitary gland in response to GH-releasing hormone from the hypothalamus. Release of growth hormone is inhibited bysomatostatin, which also is produced by the hypothalamus. GH enhances the metabolism of fats for energy. It also enhances amino acid uptake and protein synthesis, which help in growth of cartilage and bone. Secretion of growth hormone is increased by exercise, stress, lowered blood glucose, and by insulin
Secretion of growth hormone (GH) in the pituitary is regulated by the neurosecretory nuclei of the hypothalamus. These cells release the peptides Growth hormone-releasing hormone (GHRH or somatocrinin) and Growth hormone-inhibiting hormone (GHIH or somatostatin) into the hypophyseal portal venous blood surrounding the pituitary. GH release in the pituitary is primarily determined by the balance of these two peptides, which in turn is affected by many physiological stimulators (e.g., exercise, nutrition, sleep) and inhibitors (e.g., free fatty acids) of GH secretion.
Somatotropic cells in the anterior pituitary gland then synthesize and secrete GH in a pulsatile manner, in response to these stimuli by the hypothalamus. The largest and most predictable of these GH peaks occurs about an hour after onset of sleep with plasma levels of 13 to 72 ng/mL. Otherwise there is wide variation between days and individuals. Nearly fifty percent of GH secretion occurs during the third and fourth NREM sleep stages. Surges of secretion during the day occur at 3- to 5-hour intervals.The plasma concentration of GH during these peaks may range from 5 to even 45 ng/mL.Between the peaks, basal GH levels are low, usually less than 5 ng/mL for most of the day and night.Additional analysis of the pulsatile profile of GH described in all cases less than 1 ng/ml for basal levels while maximum peaks were situated around 10-20 ng/mL.
A number of factors are known to affect GH secretion, such as age, sex, diet, exercise, stress, and other hormones.Young adolescents secrete GH at the rate of about 700 ?g/day, while healthy adults secrete GH at the rate of about 400 ?g/day.Sleep deprivation generally suppresses GH release, particularly after early adulthood
6
The response of the motoneuron can be an hyperpolarization, beginning 3-4 msec after the stimulus, followed by a return to the resting potential, again with a decay time-constant of about four msec. This response is called the inhibitory postsynaptic potential, or IPSP
An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential.The opposite of an inhibitory postsynaptic potential is an excitatory postsynaptic potential (EPSP), which is a synaptic potential that makes a postsynaptic neuron more likely to generate an action potential. They can take place at all chemical synapses, which use the secretion of neurotransmitters to create cell to cell signalling. Inhibitory presynaptic neurons release neurotransmitters that then bind to the postsynaptic receptors; this induces a postsynaptic conductance change as ion channels open or close. An electrical current that changes the postsynaptic membrane potential to create a more negative postsynaptic potential is generated. Depolarization can also occur due to an IPSP if the reverse potential is between the resting threshold and the action potential threshold. Another way to look at inhibitory postsynaptic potentials is that they are also a chloride conductance change in the neuronal cell because it decreases the driving force.Microelectrodes can be used to measure postsynaptic potentials at either excitatory or inhibitory synapses.
In general, a postsynaptic potential is dependent on the type and combination of receptor channel, reverse potential of the postsynaptic potential, action potential threshold voltage, ionic permeability of the ion channel, as well as the concentrations of the ions in and out of the cell; this determines if it is excitatory or inhibitory. IPSPs always want to keep the membrane potential more negative than the action potential threshold and can be seen as a
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