HUMB1000 Lecture Notes - Lecture 9: Adrenal Medulla, Thyroid, Pituitary Gland
12 Jun 2018
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Endocrine System
Principles of Chemical Communication
❖ Autocrine
o released by cells and have a local effect on same cell type from which
chemical signals released
❖ Paracrine
o released by cells and affect other cell types locally without being
transported in blood
❖ Neurotransmitter
o produced by neurons and secreted into extracellular spaces by presynaptic
nerve terminals; travels short distances; influences postsynaptic cells
❖ Endocrine
o produced by cells of endocrine glands, enter circulatory system, and affect
distant cells
Characteristics of the Endocrine System
❖ Body control system where regulation requires duration rather than speed
❖ Glands that secrete chemical messengers (hormones) into circulatory system (blood)
❖ Hormone characteristics
o Produced in small quantities
o Transported some distance in circulatory system
o Acts on target tissues elsewhere in body
❖ Hormone secretion can be:
o Acute - sudden release due to stimulus, e.g. adrenaline in response to stress
o Chronic – small variations over long periods, e.g. thyroid hormones
o Episodic – e.g. estrogen & progesterone during menstrual cycle
❖ Target cells respond to a hormone because they have the correct receptor
Nervous VS Endocrine Systems
Similarities
Differences
• Both systems associated with the brain
❖ Endocrine – hypothalamus
• May use same chemical messenger as
neurotransmitter and hormone.
❖ E.g. epinephrine
• Two systems are cooperative
❖ e.g. some parts of endocrine
system innervated directly by
nervous system (adrenal medulla)
• Mode of transport
❖ Axon
❖ Blood
• Speed of response
❖ Nervous – instant/milliseconds
❖ Endocrine – delayed/seconds
• Duration of response
❖ Nervous – milliseconds/seconds
❖ Endocrine – minutes/days
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Links between endocrine & nervous systems
❖ CNS control over endocrine
o CNS can influence hormone release through hypothalamus
▪ Hypothalamus synthesizes neuro-hormones and controls hormone
release from anterior pituitary
o Adrenal medulla
▪ Central part of adrenal gland, arose from neural tissue, secretes
adrenalin & noradrenalin
❖ Endocrine control over CNS
Endocrine system secretes hormones that
o maintain general health of neural tissue
o regulate minerals necessary for neural function
o are needed for normal growth and function of nervous system
Functions of the Endocrine System
1. Metabolism
2. Control of food intake and digestion
3. Tissue maturation
4. Ion regulation
5. Water balance
6. Heart rate and blood pressure regulation
7. Control of blood glucose and other nutrients
8. Control of reproductive functions
9. Uterine contractions and milk release
10. Immune system regulation
Pituitary Gland
❖ Where nervous and endocrine systems interact
❖ Hypothalamus regulates secretions of anterior pituitary
❖ Posterior pituitary is an extension of the hypothalamus
❖ Anterior pituitary produces nine major hormones that
o Regulate body functions
o Regulate the secretions of other endocrine glands
Structure of the Pituitary Gland
❖ Posterior pituitary
• Extension of the nervous system via the infundibulum
• Secretes neuropeptides
❖ Anterior pituitary
• Synthesizes and secretes hormones
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Autocrine released by cells and have a local effect on same cell type from which chemical signals released. Paracrine released by cells and affect other cell types locally without being transported in blood. Neurotransmitter: produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals; travels short distances; influences postsynaptic cells. Endocrine: produced by cells of endocrine glands, enter circulatory system, and affect distant cells. Body control system where regulation requires duration rather than speed. Glands that secrete chemical messengers (hormones) into circulatory system (blood) Hormone characteristics: produced in small quantities, transported some distance in circulatory system, acts on target tissues elsewhere in body. Hormone secretion can be: acute - sudden release due to stimulus, e. g. adrenaline in response to stress, chronic small variations over long periods, e. g. thyroid hormones, episodic e. g. estrogen & progesterone during menstrual cycle. Target cells respond to a hormone because they have the correct receptor. Similarities: both systems associated with the brain.
