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0214 Class Notes - Lecture

lecture notes
Course

Anatomy And Physiology II (BIOL 1300)

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Students shared 8 documents in this course
Academic year: 2019/2020
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The Adrenal Medulla

  • Adrenal medulla – inner core, 10-20% of gland
  • Has dual nature acting as an endocrine gland and a ganglion of the sympathetic nervous system. o When stimulated, release catecholamines (epinephrine/norepinephrine) and a trace of dopamine directly into the bloodstream

Know where/what the adrenal gland is

  • As hormones, catecholamines have multiple effects: o Increases alertness and prepares body for physical activity o Increases BP, HR, blood flow to muscles, pulmonary airflow, and metabolic rate o Decreases digestion and urine production
  • Effect is longer lasting than neurotransmitters o Increases alertness and prepares body for physical activity  Mobilizes high-energy fuel, lactate, fatty acids, and glucose.  Glycogenolysis and gluconeogenesis boost glucose levels  Glucose-sparing effect because it inhibits insulin secretion.  Muscles use fatty acids, saving glucose for brain.

The Adrenal Cortex

  • Mineralocorticoids – from zona glomerulosa o Stimulates hormones that regulate electrolyte balance o Aldosterone stimulates Na+ retention and K+ excretion  Water is retained with sodium by osmosis

  • Glucocorticoids o Secretes zona fasciculata and zona reticula in response to ACTH o Regulates metabolism of glucose and other fuels o Cortisol  Helps body adapt to stress and repair tissues  Stimulates fat and protein catabolism, gluconeogenesis (glucose from amino acids and fatty acids) and release of fatty acids and glucose into blood.

  • Sex steroids o Secreted by zona fasciculata and zona reticularis o Androgens: Set libido throughout life; large role in prenatal male development o Estradiol: Small quantity from adrenals, but this becomes important after menopause from sustaining adult bone mass.

Stress and Adaptation

  • Stress – situation that upsets homeostasis and threatens one’s physical or emotional well-being. o Injury, surgery, infection, intense exercise, pain, grief, depression, anger, etc.

  • Stage of resistance dominated by cortisol

  • Hypothalamus secretes corticotropin-releasing hormone (CRH)

  • Pituitary secretes ACTH o Stimulates the adrenal cortex to secrete cortisol and other glycocorticoids o Activates fight or flight o Promotes breakdown of fat and protein into glycerol, fatty acids, and amino acids, for gluconeogenesis.

  • Effects of Cortisol o Promotes breakdown of fat and protein into glycerol, fatty acids, and amino acids, for gluconeogenesis. o Inflammatory response o Affects Thyroid hormones  Cortisol inhibits TSH thereby inhibiting T4 to T  When you are stressed, your metabolism decreases, almost like putting on the breaks.

Hormones are hydrophilic and hydrophobic

Like Dissolves Like – Things that are similar are compatible and dissolve

  • Hydrophilic o Water loving o Polar (unable to slip through cell membrane)  Proteins, peptide hormones, & catecholamines  Primarily act through second messenger system  Circulate mainly dissolved in the plasma  Travels freely in the bloodstream  Receptors on the cell surface  Secondary Messenger System  Cascade of reactions  Amplified Effect  Catecholamines  Peptides

  • Hydrophobic o Water fearing o Nonpolar o Lipophilic – Lipid loving  Steroid and thyroid hormones

Hormone Receptors and Mode of Action

  • Hormones stimulate only those cells that have receptors for them
  • Receptors are proteins or glycoprotein molecules o On plasma membrane, in the cytoplasm, or in the nucleus
  • Receptors act like switches turning on metabolic pathways when hormone binds to them o Receptors for peptide hormones are found in the plasma membrane o Receptors for lipid soluble hormones are found in the cytoplasm.
  • Usually each target cell has a few thousand receptors for a given hormone
  • Receptor-hormone interactions exhibit specificity and saturation o Specific receptor for each hormone o Saturated when all receptor molecules are occupied by hormone molecules.
  • Hydrophobic hormones o Penetrate plasma membrane and enter nucleus o Act directly on the genes changing target cell physiology o Estrogen, progesterone, thyroid hormone act on nuclear receptors o Take several hours to days to show effect due to lag for protein synthesis
  • Hydrophilic hormones o Cannot penetrate target cells o Must stimulate physiology indirectly

Steroids and Thyroid Hormone - Thyroid hormone enters target cell by diffusion, mostly as T4 with little metabolic effect. - Within a target cell, T4 is converted to more potent T - T3 enters target cell nuclei and binds to receptors in chromatin - Activates genes o Makes a muscle protein (myosin), enhancing cardiac muscle response to sympathetic stimulation and strengthening heartbeat.

Hormone Receptors and Mode of Action - Peptide Hormones o Cannot penetrate target cell o Bind to surface receptors and activate intracellular processes through second messengers - Steroid Hormones o Penetrate plasma membrane and bind to internal receptors (usually in nucleus) o Influence expression of genes of target cell o Take several hours to days to show effect due to lag for protein synthesis

Hormone Interactions - Most cells sensitive to more than one hormone and exhibit interactive effects - Synergistic effects

o Multiple hormones act together for greater effect  Ex. Synergism between FSH and testosterone on sperm production

  • Permissive Effects o One hormone enhances the target organ’s response to a second later hormone  Ex. Estrogen prepares uterus for action of progesterone
  • Antagonistic Effects o One hormone opposes the action of another  Ex. Insulin lower blood glucose and glucagon raises is.

Hormone Clearance

Hormone signals must be turned off when they have served their purpose - Most hormones are taken up and degraded by liver and kidney o Excreted in bile or urine - Metabolic clearance rate (MCR) o Rate of hormone removal from the blood o Half-life: time required to clear 50% of hormone from the blood (Lipophilic has longer half-life) o The faster the MCR, the shorter the half-life.

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0214 Class Notes - Lecture

Course: Anatomy And Physiology II (BIOL 1300)

8 Documents
Students shared 8 documents in this course

University: Fitchburg State University

Was this document helpful?
The Adrenal Medulla
- Adrenal medulla – inner core, 10-20% of gland
-Has dual nature acting as an endocrine gland and a ganglion of the sympathetic nervous
system.
oWhen stimulated, release catecholamines (epinephrine/norepinephrine) and a
trace of dopamine directly into the bloodstream
Know where/what the adrenal gland is
- As hormones, catecholamines have multiple effects:
oIncreases alertness and prepares body for physical activity
oIncreases BP, HR, blood flow to muscles, pulmonary airflow, and metabolic rate
oDecreases digestion and urine production
-Effect is longer lasting than neurotransmitters
oIncreases alertness and prepares body for physical activity
Mobilizes high-energy fuel, lactate, fatty acids, and glucose.
Glycogenolysis and gluconeogenesis boost glucose levels
Glucose-sparing effect because it inhibits insulin secretion.
Muscles use fatty acids, saving glucose for brain.
The Adrenal Cortex
- Mineralocorticoids – from zona glomerulosa
oStimulates hormones that regulate electrolyte balance
oAldosterone stimulates Na+ retention and K+ excretion
Water is retained with sodium by osmosis
- Glucocorticoids
oSecretes zona fasciculata and zona reticula in response to ACTH
oRegulates metabolism of glucose and other fuels
oCortisol
Helps body adapt to stress and repair tissues
Stimulates fat and protein catabolism, gluconeogenesis (glucose from
amino acids and fatty acids) and release of fatty acids and glucose into
blood.
- Sex steroids
oSecreted by zona fasciculata and zona reticularis
oAndrogens: Set libido throughout life; large role in prenatal male development
oEstradiol: Small quantity from adrenals, but this becomes important after
menopause from sustaining adult bone mass.

Students also viewed

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