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Flashcards in Endocrine System Deck (34):

What body responses are triggered by the parasympathetic nervous system?

Eyes - constricts pupils
Salivary Glands - stimulates salvation
Heart - slows heartbeat
Lungs - constricts bronchi
Stomach - stimulates digestion
Liver - stimulates bile release
Intestines - stimulates peristalsis and secretion
Bladder - contracts
Genitals - erections


What body responses are triggered by the sympathetic nervous system?

Eyes - dilates pupils
Salivary Glands - inhibits salvation
Heart - increases heartbeat
Lungs - dilates bronchi
Stomach - inhibits digestion
Liver - stimulates glucose release
Kidneys - stimulates adrenaline/noradrenaline release
Intestines - inhibits peristalsis and secretion
Bladder - relaxes
Genitals - ejaculation and vaginal contraction


Do sympathetic nerve fibres innervate all vessels?

Yes, except capillaries and pre-capillary sphincters (local control)


Which blood vessels are prioritised by the sympathetic NS?

- Sympathetic division prioritizes blood vessels to brain, skeletal muscles and heart in times of emergency


What is the difference between the nervous and endocrine system?

Uses neurones to send and deliver short messages that are fast-acting, localised and short-lived, while your endocrine system sends slower-moving, hormones through the blood that target broad areas and have a more lasting effect.


Give an example of neurocrine communication

Anterior pituitary, posterior pituitary and adrenal medulla


What are the major endocrine glands/organs?

Pituitary gland
Pineal gland
Thyroid gland
Parathyroid gland
Adrenal gland


Where is the thymus located?

It is located in the superior mediastinum


How does the thymus develop over time?

Fully formed and functional at birth, it involutes after puberty and by the late teens is mostly fat


What is the role of the thymus?

Its role is the maturation of bone marrow derived stem cells into immunocompetent T cells. This is called thymic cell education. It produces thymosin, a hormone that promotes T cell maturation


What do hormones control and regulate?

Metabolism & energy balance
Growth and development
Body defences
General homeostasis (water, nutrients, electrolytes etc)


Describe the key features of peptide/glycoprotein hormones

- Stored: secretory vesicles
- In blood: dissolved in plasma
- Receptor location: cell membrane
- Response to ligand binding: activates second messenger (maybe genes)
- Example: insulin, glucagon, gastrin


Describe the key features of steroid hormones

- Stored: synthesised on demand from precursors
- In blood: bound to carrier proteins
- Receptor location: cytoplasm or nucleus
- Response to ligand binding: activation of genes for transcription
- Example: oestrogen, progesterone, cortisol


What are the two types of amino acid/ tyrosine derived hormones?

- Catecholamines
- Thyroid hormones


Describe the key features of catecholamines

- Stored: secretory vesicles
- In blood: dissolved in plasma
- Receptor location: cell membrane
- Response to ligand binding: activates second messenger
- Example: adrenaline/ noradrenaline


Describe the key features of thyroid hormones?

- Stored: precursor stored in secretory vesicles
- In blood: bound to carrier protein
- Receptor location: nucleus
- Response to ligand binding: activates genes for transcription
- Example: thyroxine


How do the CNS and endocrine system communicate?



What does the hypothalamus control ?

– Thermoregulation, panting, sweating, shivering
– Plasma osmolalty via osmoreceptors
– Heart rate, blood pressure
– Feeding, satiety, GIT regulation
– Circadian rhythms, wakefulness, sleep (afferents from retina)
– Autonomic input/stimulation via connections to the sympathetic andparasympathetic systems
– Emotion, sexual behaviour
– Lactation (suckling/baby crying)


What does the hypothalamus produce and where do they go?

– ADH and oxytocin that travel to posterior pituitary
– 6 hormones that travel via the hypothalamo-hypophyseal portal system to the anterior pituitary (4 stimulatory, 2 inhibitory)


What is the hypophysis?

- Pituitary gland
- Two lobes (anterior and posterior)


Describe the negative feedback caused by thyroxin (hypothalamic-pituitary-thyroid axis)

- Hypothalamus produces TRH (thyrotropin releasing hormone)
- Converted to TSH (thyroid stimulating hormone) in the pituitary
- T3 and T4 (thyroxin)
- Inhibit TRH release (long loop inhibition)
- Inhibit TSH (short loop inhibition)


What is the stress response ?

- Stress is commonly defined as a state of real or perceived threat to homeostasis.
- Maintenance of homeostasls In the presence of aversive stimuli (stressors) requires activation of a complex range of responses involving the endocrine, nervous, and immune systems, collectively known as the stress response.
- Activation of the stress response initiates a number of behavioral and physiological changes that improve an individual's chance of survival when faced with homeostatic challenges
- The principal effectors of the stress response are localized in the hypothalamus, the anterior lobe of the pituitary gland, and the
adrenal gland


Describe the behavioural effects of the stress response

Increased awareness, improved cognition, euphoria, and enhanced analgesia


Describe the physiological effects of the stress response

1. Increased cardiovascular tone, respiratory rate, and
intermediate metabolism
2. Inhibition of general vegetative functions such as feeding, digestion, growth, reproduction, and immunity


Describe the HPA Axis

- Hypothalamo-pituitary-adrenal axis
- Hypothalamus releases CRH (corticotropin releasing hormone)
- Causes anterior pituitary to release ACTH (adrenocorticotropic hormone)
- Causes adrenal cortex to release cortisol
- Cortisol negative feedback inhibits ACTH and CRH


Describe the neurons from the CNS to effectors

In the ANS
1. Somatic - Presynaptic neuron whose cell body is in the CNS straight to effector organ
2. Postsynaptic neuron whose cell body is in peripheral ganglion, second neurone to effector organ


Describe the composition of the adrenal gland

- The central portion of the adrenal gland, the medulla, is composed of a parenchyma of large, pale-staining epithelioid cells called chromaffin cells.
- The chromaffin cells are, in effect, modified neurons.
- Numerous myelinated, presynaptic sympathetic nerve fibers pass directly to the chromaffin cells of the medulla.


Why are chromaffin cells considered to be the equivalent of postsynaptic neurons?

When nerve impulses carried by the sympathetic fibers reach the catecholamine-secreting chromaffin cells, they release their secretory products adrenaline and noradrenaline into the blood
- Neurocrine secretion


What are the effects of adrenaline and noradrenaline on the body?

1. Glycogen broken down to glucose (increased blood glucose)
2. Increased BP
3. Increased breathing rate
4. Increased metabolic rate
5. Change in blood flow patterns, leading to increased alertness and decreased digestive excretory and reproductive system activity


How does the adrenal gland respond to stress in the short term?

1. Increased heart rate
2. Increased blood pressure
3. Liver converts glycogen to glucose (increased blood glucose)
4. Dilation of bronchioles
5. Changes in blood flow patterns
6. Increased metabolic rate


How does the adrenal gland respond to stress in the long term?

1. Retention of Na+ and water in kidneys
2. Increased blood volume and blood pressure
4. Proteins and fats converted to glucose
5. Increased blood sugar
6. Suppresses immune system


What are the posterior pituitary hormones and how are they secreted?

The posterior pituitary hormones are oxytocin and ADH, both are produced in the hypothalamus, travel down the neuronal axons and are secreted adjacent to the capillaries of the posterior pituitary


What does the pineal gland produce?

• It produces melatonin (not melanin!)
• Melatonin is involved in control of circadian rhythmn.
- Light exposure inhibits melatonin release. The neuronal pathway is from retina to hypothalamus to pineal gland
• Melatonin inhibits release of gonadotrophins (LH and FSH)
• The pineal gland function remains a bit of a mystery and is the
subject of much research
• Perhaps most important thing to know is that it calcifies in early
adulthood and is therefore visible on skull x-rays


How do hormones pass from the hypothalamus to the anterior pituitary ?

Hypothalamo-hypophyseal portal system