Endocrine vs. Nervous System

Stimulus for their release = lowered blood pressure or low salt or water concentration in the blood will stimulate the release of ADH from the posterior pituitary.

Learning Objective 1: 18.6 Describe the properties of the hypothalamus and pituitary gland and the

The nervous system uses sensory receptors, nerves and your brain to control your cells, and acts quickly. The endocrine system uses your circulatory system and hormones to care for your cells and acts more slowly. The reproductive system and endocrine systems use hormones to function. The nervous and endocrine systems are connected by sending information to the hypothalamus and uses the autonomic nervous system to transmit what activity needs to take place in the body. This activity might be what hormones are needed, or what sensations the body feels. While the nervous and endocrine systems send information to the hypothalamus, the reproductive system receives information from the hypothalamus. So all three systems do work together, although

Cortisol production is stimulated by ACTH secretion from the anterior pituitary via numerous feedback mechanisms according to the circadian rhythm, with peak levels in the early morning and smaller fluctuations throughout the day. ACTH secretion is stimulated by CRH in the hypothalamus which is stimulated by things such as: decreases in plasma cortisol, hypoglycemia, stress, and infection. Secretion of ACTH leads to conversion of cholesterol to cortisol in the zona fasciculata of the adrenal gland via various cytochrome P450 enzymes. Increased levels of cortisol itself cause negative feedback on the pituitary and hypothalamus. The zona glomerulosa is the site of production of Aldosterone, the principal mineralocorticoid, via similar mechanisms (cytochrome p 450.) Aldosterone production is stimulated by activation of the renin angiotensin system in response to decreased intravascular volume (sensed by baroreceptors), decreased sodium levels sensed in the macula densa of the nephron, and by the sympathetic nervous system in response to stress.

The hypothalamic nucleus, by releasing specific neuro- transmitter peptides, controls the activities of the secretory cells of the anterior lobe of the pituitary body. Hormones released or secreted by cells of the supraoptic and paraventricular nuclei are transported, in the form of granules, to the posterior lobe of the pituitary; from there they are absorbed into the blood stream (Engel, 1997).Under conditions of disease, the neurotransmitter peptides may be quantitatively increased, decreased, or in some way made defective; the neurons that synthesize these peptides or their glandular targets may fail to function or become over active(Ropper, 2002). The nuclei of the hypothalamus are conventionally divided into three paired groups: the anterior group, including the preoptic, supraoptic, and paraventriular nuclei, which are mainly neurohypophysical in their relationships; the middle group, including the tuberal, arcuate, ventrolatural, and dorsal nuclei; and the posterior group including the mammillary and posterior nuclei (Ropper, 2002).The Hypothalamus or hypopysis is divided into two lobes: the anterior, or adenohypophysis, which is derived from the buccal endoderm(Rathke’s pouch),and; the posterior, or neurohypophysis, which forms a diverticulum from the base of the hypothalamus (Bostrom,2003).

GnRH is released into the anterior pituitary gland and here it stimulates the production of follicle stimulating hormone (FSH) and lutenising hormone (LH).

Figure 2: The figure below illustrates how the interior structure of the pituitary gland and hypothalamus facilitate for hormone secretion. The pituitary gland consists of the posterior and anterior lobe. It is lined with

A: The hypothalamus controls hormone release mainly through the pituitary gland by sending signals in the form of releasing hormones to prompt the anterior lobe to secrete them as the main function of the pituitary gland is hormone secretion into the body. The anterior lobe is responsible for the release of crucial hormones including; growth hormone, follicle stimulating hormone, luteinizing hormone, adrenocorticotrophic hormone, thyroid stimulating hormone and finally prolactin.

It starts off with the hypothalamus gland, which is located near the center of the brain. It receives chemical and nervous signals regarding 4 of the 5 senses being sight, sound, taste and smell, as well as the body’s temperature, blood glucose levels, and the body’s balance of salt water. Furthermore, it also helps to control hunger and thirst, and takes part in the reproductive system. The hypothalamus also controls the pituitary gland.

The case is about the same with thyroid hormones. The hypothalamus is apart of the brain that produces thyroid-releasing hormones. This hormone pairs with what is known as our pituitary gland to begin the production of a thyroid-stimulating hormone. This pairing up acts on the thyroid in order to produce thyroid hormones, which travel through our bodies.

The characteristics of the endocrine system that makes its reactions different from those of the nervous system is that: the endocrine system is slower at communicating than the nervous system, the endocrine system hormones only reacts to cells with distinctive receptors for that hormone, and the endocrine system hormones practically reaches all cells in the body.

gland to release ACTH. If the CRH gets low it prevents the pituitary from releasing ACTH,

According to Shier, Butler & Lewis (2009) “other glands that produce hormones and thus are parts of the endocrine system include the pineal gland and the thymus gland”. Shier et al., 2009 argued the pineal gland, located deep between the cerebral hemispheres, secretes hormone melatonin that acts on certain brain regions that function as a biological clock. The changing levels of melatonin across 24 hours enable the body to know when day is and when is night.

Whereas, the hormones produced by the adrenal cortex will deal with long-term stress. There are two major hormones that made by adrenal cortex, which is mineralocorticoids and glucocorticoids.

Adrenal glands, located near the kidneys, secrete several hormones that are activated by the nervous system. These hormones dictate the body’s reaction to stressful situations. Each person secretes a different amount of hormones, therefore affecting behavior in stressful situations differently (Morris & Maisto, 2005).