Lecture 23- Neuromodulation Flashcards
What is neuroendocrinology?
Studies the interaction between the nervous system and the endocrine system (hormones - circulatory system)
How is the neuroendocrine system bidirectional?
-Neurons regulate hormone secretion
-Hormones regulate neurons in the brain (i.e. act as neuromodulators).
How does the hypothalamus control the pituitary gland?
-Effect of hormones (estrogen) on neurons in the CNS
-The hypothalamus is connected by a stalk to the pituitary gland which releases hormones into the blood system
What is the hypothalamus known as?
The hypothalamus is a hypophysis or “Master Gland”- it secretes many hormones and regulates the function of other hormone-secreting glands.
What two important physiological processes does the hypothalamus and pituitary have a role in?
-homeostasis
-physiological responses (reproduction, stress, body weight)
What are the three zones of the hypothalamus?
lateral, medial and periventricular
What do the lateral and medial zones of the hypothalamus do?
lateral and medial project to brain stem and telencephalon
What does the periventricular zone of the hypothalamus do?
periventricular has multiple
functions including:-
regulation of the pituitary
Where do the Magnocellular neurons of the hypothalamus project to? What do they do?
-Magnocellular neurons project to posterior lobe of pituitary
-Magnocellular release neurohormones, oxytocin and antidiuretic hormone (ADH/ vasopressin) into the capillary bed (bloodstream)
How is Antidiuretic hormone release controlled from the hypothalamus?/ what does it do in the body?
Hypothalamus integrates multiple inputs
relating to blood pressure and osmolality:
* ADH regulates extracellular fluid volume
* ADH acts on kidney to increase water retention.
* and constricts blood vessels
What does oxytocin hormone do?
Oxytocin involved in uterine contraction and milk ejection
Does oxytocin and ADH act purely in the PNS?
No also act within the CNS
What do Parvocellular neurons of the hypothalamus regulate?
Anterior lobe of the pituitary
What type of hormones do Parvocellular neurons release and where do these go?
-Parvocellular neurons secrete hypophysiotropic hormones into the hypothalamic pituitary portal circulation
-These signals travel to the anterior pituitary and results in the release of other hormones
What are some examples of hypophysiotropic hormones?
- Gonadotropin-releasing hormone (GnRH)
- Thyrotropin-releasing hormone (TRH)
- Corticotropin-releasing hormone (CRH),
- Growth hormone-releasing and inhibiting
hormones (GHRH and somatostatin)
What are some hormones released from the anterior pituitary as a result of hypophysiotropic hormones?
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Growth hormone (GH)
- Prolactin
What is follicle stimulating hormone?
Stimulates estrogen secretion, egg production (females), sperm
production (males)
What is Luteinizing Hormone (LH)?
Triggers ovulation, progestin production (females), androgen production (males). LH and FSH are collectively known
as gonadotrophins.
What is Thyroid-Stimulating Hormone (TSH)?
Triggers thyroid hormone release, called thyroxine.
What is Adrenocorticotropic Hormone (ACTH)?
Stimulates glucocorticoid release from the adrenal gland
What is Growth hormone (GH)?
Stimulates cell growth via somatomedins released from liver
What is Prolactin (PRL)?
Stimulates mammary gland development and milk secretion
Draw the flow chart to summarize the hypothalamus and anterior pituitary interaction…
Side 13
Draw the flow chart to summarize the release of Gonadotropin releasing
hormone (GnRH)
Slide 15
What hormones are important for males?
- LH stimulates the testes to produce testosterone.
- FSH is involved in the maturation of sperm cells within the testes.
- Sperm maturation also requires testosterone, meaning that both LH and FSH play key roles in male fertility.
- Because there is cortical input to the hypothalamus, it is possible for psychological factors to decrease male
fertility by inhibiting gonadotropin secretion and sperm production.
What hormones are important for females?
- LH and FSH cause the secretion of estrogens from the ovaries. In the absence of gonadotropins, the ovaries are inactive, which is the situation throughout childhood.
- Variations in LH and FSH levels in adult females cause changes in the ovaries, and control the reproductive cycle, or menstrual cycle.
NOTE: positive and negative feedback regulatory loops
What is estrogen/ estradiol?
Is an examples of a steroid hormone
* Responsible for the development and
regulation of the female reproductive
system
* Estrogens play important physiological roles in males, although the levels are significantly lower in males than in females
What is Testosterone is converted to in the brain?
Estradiol
Where is estrogen in the CNS?
-Widely distributed
-Concentrated in pituitary and hypothalamus
-Also in the cortex, midbrain and cerebellum
What is the neural effect of estrogen? Is this fast or slow?
-Alters both the structure and function of neurons
On the functional side:
-Alters the intrinsic excitability of neurons
-via modulating the flow of potassium ions
-Depolarization
-More action potentials
=This is fast
On the structural side:
-Neurite growth in the hypothalamus
-forming neuronal circuitry during brain development
-increasing the number of dendritic spines
=This is slow
How does estrogen effect synaptic plasticity?
- Enhanced postsynaptic responses to glutamate
-Strengthens synapses
-Growth of synapses - Decreasing synaptic inhibition.
-Less GABA, less synaptic inhibition
What disease could estrogen therapy potentially have an effect?
Alzheimer’s disease
What are estrogen receptors and where are they located? Are they fast or slow acting?
Intracellular
* Estrogens are lipophilic and can enter the
brain by crossing membranes
- Estrogens can bind intracellular receptors
such as: - Nuclear estrogen receptors (ERα and ERβ)
- Transcription regulators
- Alter gene transcription
=Slow and long-lasting response
What are the four steps of the Reverse transcription-polymerase chain reaction?
-Isolate (purify) RNA
-Convert RNA-cDNA
-Amplify target DNA (PCR)
-Analyse products
As opposed to intracellular receptors what is the second type of estrogen receptor?
membrane-associated
