ANS and Endorinology Flashcards
what is the Organization of the sympathetic and parasympathetic systems?
- Sympathetic Nervous System (SNS):
Origin: The sympathetic nervous system originates from the thoracic and lumbar regions of the spinal cord. It is often referred to as the “thoracolumbar division” of the ANS.
Neurotransmitter: The primary neurotransmitter used by the sympathetic nervous system is norepinephrine (also known as noradrenaline).
Ganglia: Sympathetic ganglia are typically located close to the spinal cord and form a chain called the sympathetic chain ganglia (or sympathetic trunk). Pre-ganglionic neurons are short, while post-ganglionic neurons are long.
Response: The SNS is responsible for the “fight or flight” response. It prepares the body for stressful situations by increasing heart rate, dilating airways, shunting blood to muscles, and inhibiting non-essential functions like digestion.
2. Parasympathetic Nervous System (PNS):
Origin: The parasympathetic nervous system originates from the cranial nerves (such as the vagus nerve, CN X) and the sacral region of the spinal cord. It is often referred to as the “craniosacral division” of the ANS.
Neurotransmitter: The primary neurotransmitter used by the parasympathetic nervous system is acetylcholine.
Ganglia: Parasympathetic ganglia are located close to or within target organs. Pre-ganglionic neurons are long, while post-ganglionic neurons are short.
Response: The PNS is responsible for the “rest and digest” response. It promotes relaxation, conservation of energy, and activities such as digestion, salivation, and slowing of the heart rate.
Pre- and postganglionic neuron and their transmitter substances?
preganglionic always have achetylcholin as a neurotransmiter ( Nicotin receptors) ( N1 for sceletal N2 for the others)
post ganglionic neurons of the sympathetic
have norepinephrin ( A, B ANDRNERGIC RECEPTORS)
Preganglionic neurons contact upto 200
postganglionic
Originate from Th1 to L3
post ganglionic neurons of parasympathetic have acetylcholin ( MUSCARINIC RECEPTORS)
Para- and prevertebral sympathetic ganglions?
Paravertebral Ganglia:
In the sympathetic chain ganglia, the pre-ganglionic neurons are relatively short, and the post-ganglionic neurons are relatively long.
Prevertebral Ganglia:
In prevertebral ganglia, the pre-ganglionic neurons are relatively long, and the post-ganglionic neurons are relatively short.
Digestion etc.
Explain adrenal medulla hormones synthesis
Synthesis of Adrenal Medulla Hormones:
Tyrosine Uptake: The synthesis of adrenal medulla hormones begins with the uptake of the amino acid tyrosine from the bloodstream into the adrenal medullary cells.
Conversion to Dopamine: Inside the adrenal medullary cells, tyrosine is converted into dopamine by the enzyme tyrosine hydroxylase.
Conversion to Norepinephrine: Dopamine is then converted into norepinephrine by the enzyme dopamine beta-hydroxylase.
Conversion to Adrenaline: Some of the norepinephrine is further converted into adrenaline (epinephrine) by the enzyme phenylethanolamine-N-methyltransferase (PNMT).
Explain the most common disease with overproduction of catecholamines.
Pheochromocytom: Catecholamine
producing tumor in the adrenal medulla →
hypertension, tachycardia and sweating →
attacks
what are the Cell types that are innervated by autonomic nerves?
many target organs and tissues
Effects of the autonomic nervous system on different organs?
depends on if the autonomic activity is sympathetic or parasympathetic
Know how autonomic nerve activity can be measured?
§ MSNA = muscle sympathetic nerve
activity
§ HRV = Heart rate variability
§ Plasma catecholamine’s and
metabolites
MSNA is quantified by counting the neural bursts identified
in a mean voltage neurogram and expressing them as:
1) bursts / minute (Burst Frequency [BF])
2) bursts / 100 heart beats (Burst Incidence [BI])
Describe important steps in the steroidogenesis
- About 80% of the cholesterol required for steroid hormone formation
comes from LDL (low-density lipoprotein). - LDL ➔taken up via receptor-mediated endocytosis
- The remaining cholesterol is formed In the cell ➔de novo acetyl
coenzyme A (Acetyl CoA)
3β-hydroxysteroid dehydrogenase (3β-HSD)
- Pregnenolon → progesteron
- Dehydroepiandrosteneion (DHEA) → androstenedione
* 17β-hydroxysteroid dehydrogenase (17β-HSD) (oxidation or reduction)
- Estron → Estradiol (or other way around)
- Androstenedion → Testosteron (or other way around)
* 5𝝰-reductase
- Testosteron → dihydrotestosteron (DHT)
* Aromatase
- Androstenedion → Estrone
- Testosteron → Estradiol
* Lack of specific enzymes can lead to over and under production of steroid
hormones
Describe concepts of endocrine, paracrine, autocrine and neurocrine effects.
§ Autocrine signalling → endocrine cell regulates itself
§ Paracrine signalling → endocrine cell regulates cells
nearby
§ Endocrine signalling → all circulating hormones
§ Neurocrine signalling → nervcells produce hormones →
released into blood e.g. nerve cells in hypothalamus
produce oxytocin → released into blood stream
§ Neuroendocrine signalling → Nerves activate hormone
producing cells → released into blood stream
§ E.g. Sympathetic nerves → chromaffin cells in adrenal medulla →
epinephrine released into blood stream
Describe primary endocrine organs and tissues, the hormones they produce and secrete
IGF-1
production by liver and multiple somatic cells
Thyroid follicular cells produce
T3/T4
Ovarian granulosa cells ➔
Estrogens and progestins / Sertoli cells ➔
Spermatogenesis and inhibin
Ovarian theca cells
➔testosterone /Leydig cells ➔ testosterone
Mammary glands,
initates and maintain milk production
Hypothalamic and Posterior
Pituitary Hormones : Arginine vasopressin (AVP) antidiuretic
hormone (ADH) ➔ Acts on the collecting duct
of the kidney to increase water reabsorption
* Oxytocin ➔ Stimulation of smooth-muscle
contraction by the uterus during parturition and
mammary gland during suckling
Define and explain the concepts: Pulsatility, biorhythm and feed-back regulation
Biorythm
§ Circadian rythm (cortisol)
§ Monthly rythm (female sex hormones)
§ Life rythm (growth hormone)
Principles for Feed-back
§ Negative / Positive feedback
§ Long feedback loop
§ Active hormone regulates the hypothalamus
§ Short feedback loop
§ Active hormone regulates pituitary
Explain the hypothalamus-pituitary axis, feedback regulation and differences between adeno-, and neuro pituitary
Hypothalamus: The hypothalamus is a region of the brain that serves as a control center for the autonomic nervous system and plays a vital role in maintaining homeostasis. It produces various neurohormones, such as releasing hormones (e.g., gonadotropin-releasing hormone or GnRH) and inhibiting hormones, which regulate the release of hormones from the anterior pituitary.
Anterior Pituitary (Adenohypophysis): The anterior pituitary is a gland located at the base of the brain, just below the hypothalamus. It is often referred to as the “master gland” because it secretes several important hormones in response to signals from the hypothalamus. These hormones include thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH), and prolactin (PRL).
Posterior Pituitary (Neurohypophysis): The posterior pituitary is not a true gland but rather an extension of the hypothalamus. It stores and releases two hormones produced by the hypothalamus: oxytocin and vasopressin (antidiuretic hormone, ADH). These hormones are transported down nerve fibers from the hypothalamus to the posterior pituitary, where they are released into the bloodstream.
Feedback Regulation:
The hypothalamus-pituitary axis operates through a feedback system to maintain hormonal balance in the body. This feedback regulation helps to ensure that hormone levels stay within a narrow range.
Negative Feedback: In most cases, hormone release in the hypothalamus-pituitary axis is controlled by negative feedback. When the target endocrine gland releases a hormone that affects a specific physiological process, and the hormone levels reach an optimal range, it sends signals back to the hypothalamus and pituitary to inhibit further hormone production. For example, when thyroid hormone levels are sufficient, they signal the hypothalamus and pituitary to reduce the release of TSH.
Positive Feedback: In some instances, positive feedback is involved. This means that the hormone release stimulates further hormone production. A classic example is the release of oxytocin during childbirth. Oxytocin stimulates uterine contractions, which, in turn, stimulate more oxytocin release, creating a positive feedback loop that helps facilitate labor.
Describe mechanisms for hormone transport and bioavailability
§ Mainly regulated by feed-back loops
§ Low circulating levels pituitary
secretion
§ High circulating levels ¯ pituitary secretion
§ Protein binding free vs bound
§ Only free hormones has an effect and can
exert feed back regulation
§ Local enzymes in the tissue
§ Converts to a more potent form or inactivate
§ Receptor – number and affinity
§ Hormone sensitivity and responsiveness
§ Synergism e.g. estrogen – progesterone –
prolactin – synergism in milk secretion
§ Antagonism e.g. insulin decrease and glucagon
increase glucose
§ Permissiveness e.g. TH on catecholamine’s
Explain differences and similarities between the nervous system and the endocrine system in the regulation of function of target tissues/cells
Autonomic Nervous System (ANS)
- Rapid: seconds
-Specific: innervation to cells / organ
Endocrine System
- Slower: seconds – days
- General / selectiv: via blood / circulation,
receptors in target organ
Autonomic Nervous System (ANS)
- Nerv release hormone (e.g. neuropituitary)
- Nerv stimulates gland to release a hormone
(e.g SA-axis)
Predict the consequences of decreased or increased hormone synthesis example ( decreased ADH)
Homeostatic Imbalance
* Alcohol inhibits ADH release → ↑ urine
output
* ADH deficiency—diabetes insipidus;
↑↑ urine output and intense thirst
* ADH hypersecretion e.g. after
neurosurgery, trauma, or secreted by
cancer cells
* Syndrome of inappropriate ADH
secretion (SIADH)
Explain adrenal cortex hormones synthesis, biological effects and how the production and secretion is regulated
Adrenal cortex – 3 layers
Zona glomerulosa
Zona fasciculate
Zona reticularis
Adrenal cortex produce and
secrete 4 groups of steroid
hormones
Zona glomerulosa
Mineralkortikoider - aldosteron
Zona fasciculata
Glukokortikoider - kortisol
Zona reticularis
Androgener - DHEA och androstenedione
Medulla
Katekolaminer – Adrenalin (noradrenalin)
Explain the most common diseases with over- and underproduction of adrenal cortex hormones and principles for treatment
Regulation of aldosterone
§ Aldosteronism—
hypersecretion due to
adrenal tumors
-Hypertension and edema due to
excessive Na+
- Excretion of K+ leading to abnormal
function of neurons and muscle
Explain the HPA-axis response to stress, the link between the adrenal cortex and adrenal medulla
The glomerulosa zone is
controlled by the reninangiotensin
system and [K+].
The zona fasciculata and zona
reticularis are regulated by the
hypothalamus (CRH)-pituitary
(ACTH).
Despopoulos & Silbernagl,
”Color atlas of physiology”,ed
5, Thieme, 2003
Summary – regulation of
HPA and AS-axes
Adrenal medulla – adrenalin 80% and
noradrenalin 20%
adrena medula regulated by the sympathetic system (SA axis) and not from the HPA axis
Sympathetic activation
§ Stimulation of heart and blood vessels →↑ blood pressure,
cardiac output and peripheral resistance
§ Redistribution of blood → ↑ to muscle and heart
§ Dilatation of brochiolar tree
§ Reduced salivary secretion
§ Demands on metabolic substrates (glucose and fatty acids)
→ sympathetic nerves and epinephrine → liver and adipose
tissue
§ Glucogenolyses (stored glycogen is mobilized)
§ Lipolysis (fat cells converts stored TG to FFA)
§ Maintain body temperature → adjust skin blood flow
how the production and secretion of adrenal medulla hormones is regulated.
The production and secretion of adrenal medulla hormones are tightly regulated by the sympathetic nervous system, which responds to stress and various physiological signals. Here’s how it works:
Sympathetic Nervous System Activation: Stressful situations or stimuli, such as a perceived threat or physical stress, activate the sympathetic nervous system.
Release of Neurotransmitters: The sympathetic nervous system releases neurotransmitters, particularly acetylcholine, at synapses onto the cells of the adrenal medulla. This stimulation triggers the release of adrenaline and noradrenaline.
Hormone Secretion: Upon stimulation by acetylcholine, the adrenal medullary cells release stored adrenaline and noradrenaline directly into the bloodstream.
Feedback Mechanisms: Once the stressor is resolved, negative feedback mechanisms, involving hormones like cortisol and the parasympathetic nervous system, help return the body to a state of homeostasis by reducing the release of adrenaline and noradrenaline.
Chromaffin cells what do they do ?
§ Chromaffin cells secrete epinephrine (80%)
and norepinephrine (20%)
§ Epinephrine stimulates metabolic
activities, bronchial dilation, and blood flow
to skeletal muscles and the heart
§ Norepinephrine: Peripheral
vasoconstriction and blood pressure
§ Pheochromocytom: Catecholamine
producing tumor in the adrenal medulla →
hypertension, tachycardia and sweating →
attacks
β-adrenergic
receptor (AR) what are they and what do they do ?
- β-adrenergic receptor (AR) → adrenalin (noradrenalin)
- Three β-AR subtypes:
- β1-AR – in heart muscle
- β2 -AR – in lung, GI, liver, uterus, smooth muscle, vasculature
- β3-AR – in fat cells and brown fat
α-adrenergic
receptor (AR) types what are they and what do they do ?
- α-adrenergic receptors (AR) → higher affinity for
noradrenalin - Two α –AR subtypes:
- α1-AR – in smooth muscle, heart and liver
- α2 -AR – in thrombocyte, vessels, nerv terminals,
pancreatic islands