Ruminant Nutrition Exam 2

Hypothalamus

Structure responsible for coordinating the activity of both the anterior and posterior pituitary.

Distinction between Anterior and Posterior Pituitary

The anterior pituitary produces its own hormones, while the posterior pituitary stores and releases hormones produced by the hypothalamus.

ACTH

A hormone released by the anterior pituitary that acts on the adrenal gland.

HPA-axis pathway

The sequence is Hypothalamus → CRH → anterior pituitary → ACTH → adrenal cortex.

Stress

A major physiological stimulus that activates the HPA axis.

Circadian clock influence on HPA axis

Provides timing-related input into the stress-response system.

CRH

A hormone produced by the hypothalamus in response to stress that stimulates the anterior pituitary.

Glucocorticoids

Hormones ultimately produced by the adrenal gland in response to ACTH.

Adrenal medulla location

The center of the adrenal gland.

Catecholamines

Hormones primarily produced by the adrenal medulla.

Zona fasciculata

The adrenal cortical zone that produces glucocorticoids.

Androgens

The primary product of the zona reticularis.

Mineralocorticoid

A category of hormones that includes aldosterone.

Zona reticularis

The adrenal zone that primarily produces androgens.

Sympathetic activity during stress

Increased sympathetic activity and increased epinephrine are expected responses.

Vasopressin

Hormone that promotes water retention and is also known as ADH.

Vasopressin production

Produced by the hypothalamus and stored/released by the posterior pituitary.

Water retention

The primary function of vasopressin.

Vasopressin's role in fluid balance

Regulates the relationship between water and dissolved substances such as salts.

Vasopressin receptor action

Promotes insertion of AQP2 aquaporin channels in the nephron.

Increased blood volume effect

Increased water reabsorption can lead to increased blood volume and blood pressure.

AQP2 and AQP3 comparison

AQP2 is regulated by vasopressin, while AQP3 is not.

Insulin response to food intake

Generally secreted in response to food intake, particularly carbohydrate availability.

Glucagon

Hormone that access glucose reserves when blood glucose is low.

Insulin and glucagon functions

Complementary regulators that act in opposing directions to help regulate blood glucose.

Epinephrine

Associated with the sympathetic fight-or-flight response and mobilization of fuel reserves.

High-carbohydrate meal response

Blood glucose rises, insulin rises, and glucagon decreases.

Amino acids rise after protein meal

Leads to insulin increase without a major rise in blood glucose.

Neuronal relationship

Determined by the behavior of the presynaptic neuron and the relationship between the neurons.

Rigor mortis cause

Occurs primarily because ATP is unavailable for myosin detachment.

Concentric contraction

A contraction in which the muscle produces force while shortening.

Neuromuscular junction

Connection between a motor neuron and a muscle fiber.

Motor end plate

Specialized region of the muscle cell membrane at the neuromuscular junction.