ANAT 1010 Lecture Notes - Neuroglia, Sympathomimetic Drug, Chromaffin Cell
ENDOCRINE SYSTEM (Chapter 23)
A. Endocrine Glands
1. The body contains two types of glands:
i. exocrine glands (e.g., sudoriferous, sebaceous, and mucous glands)
secrete their products into ducts which deliver the
secretions into body cavities, into the lumen of an
organ, or to the outer surface of the body ii.
endocrine glands secrete their products, called
hormones, into the surrounding interstitial fluid
from which they diffuse into capillaries to be
carried away by the blood
2. The endocrine glands collectively form the endocrine system; there are several
organs of the body (e.g., hypothalamus, thymus gland, pancreas, stomach, skin,
heart, etc.) that contain endocrine tissue but are not endocrine glands exclusively.
B. Comparison of Nervous and Endocrine Systems
1. The nervous and endocrine systems together coordinate functions of all body
systems.
2. The nervous system controls homeostasis via nerve impulses that trigger
release of neurotransmitter molecules which excite or inhibit other neurons,
muscle cells, or gland cells.
3. The endocrine system controls homeostasis by secreting hormones, i.e.,
messenger molecules, into the bloodstream for delivery to virtually all body cells.
4. The nervous and endocrine symptoms act as a coordinated supersystem called
the neuroendocrine system: some neurons stimulate or inhibit the release of
hormones and some hormones promote or inhibit the initiation of nerve impulses.
5. The nervous system causes muscles to contract and glands to secrete; the
endocrine system affects virtually all body tissues by altering metabolic activities,
regulating growth and development, and guiding reproductive processes.
6. Nerve impulses typically produce their effects within several milliseconds and
the effects are relatively brief in duration; hormones may take seconds to hours to
produce their effects and these effects are generally longer in duration.
C. Hypothalamus and Pituitary Gland (Hypophysis)
1. The hypothalamus is the major integrating link between the nervous and
endocrine systems.
2. The hypothalamus receives input from numerous sources and, in addition to
many other functions, exerts control over the pituitary gland and is itself a crucial
endocrine gland; the hypothalamus and pituitary gland together play important
roles in regulation of virtually all aspects of growth, development, metabolism,
and homeostasis.
3. The pituitary gland:
i. lies at the base of the brain
ii. is attached to the hypothalamus by the infundibulum
iii. has two anatomically and functionally separate portions:
a. anterior pituitary gland (anterior lobe) accounts for about
75% of the total weight of the gland and contains many
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glandular cells that form the glandular part of the pituitary
gland
b. posterior pituitary gland (posterior lobe) contains axons
and axon terminals of neurons whose cell bodies are
located in the hypothalamus
- the nerve fibers that terminate in the posterior pituitary
gland are associated with specialized neuroglia called
pituicytes
4. Anterior Pituitary Gland (Anterior Lobe) or Adenohypophysis:
i. Secretion of anterior pituitary hormones is regulated by releasing
hormones and inhibiting hormones that are delivered from the
hypothalamus by a system of blood vessels.
ii. Five major types of anterior pituitary cells secrete seven major
hormones:
a. somatotrophs secrete human growth hormone (HGH) which
stimulates general body growth and regulates aspects of
metabolism
b. lactotrophs secrete prolactin (PRL) which stimulates milk
production
c. corticotrophs secrete 1) adrenocorticotropic hormone (ACTH)
which stimulates the adrenal cortex to secrete glucocorticoids; 2)
melanocyte-stimulating hormone (MSH) which affects skin
pigmentation
d. thyrotrophs secrete thyroid-stimulating hormone (TSH) which
regulates activities of the thyroid gland
e. gonadotrophs secrete follicle-stimulating hormone (FSH) and
luteinizing hormone (LH) which affect activities of the ovaries and
testes
5. Posterior Pituitary Gland (Posterior Lobe) or Neurohypophysis:
i. The posterior pituitary does not synthesize hormones but it does
store and release two hormones synthesized in the hypothalamus.
1. oxytocin (OT) which is involved in labor and milk
ejection
2. antidiuretic hormone (ADH) which decrease urine
volume and increases blood pressure
- these hormones are delivered in secretory vesicles to and
stored in the axon terminals until nerve impulses that are
delivered to the axon terminals trigger release of the
hormones into nearby capillaries
D. Thyroid Gland
1. The thyroid gland is located just below the larynx.
2. It has right and left lateral lobes, located on either side of the trachea, that are
connected by an isthmus that lies in front of the upper end of the trachea
3. It contains thyroid follicles; the wall of each follicle consists of two types of
cells:
i. follicular cells which secrete:
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