Hypothalamic and Pituitary Hormones Quiz

Hypothalamic Hormones and Pituitary Hormones

• The hypothalamus releases hormones that regulate the anterior pituitary
• These hormones (GnRH, CRH, TRH, PRH, Dopamine, GHRH, Somato-statin) act on the anterior pituitary
• The anterior pituitary then releases its own hormones (FSH/LH, ACTH, TSH, Prolactin, GH)
• These hormones regulate various target organs such as Gonads, Adrenal Cortex, Thyroid, Mammary Gland
• The posterior pituitary releases ADH and oxytocin

Cell-Cell Communication

• Complex multicellular organisms need long-range signaling
• Specialized cells have evolved for intercellular communication
• Key communication systems include Nervous System, Endocrine, and Immune Cells

Autocrine Mechanism of Signaling

• A signal released by a cell affects the same cell type
• Signals are quickly inactivated
• An example is prostaglandin

Prostaglandin Autocrine Control

• Autocrine control involves the signaling of a cell to itself via prostaglandins
• This signaling plays a role in growth and migration

Paracrine Mechanism of Communication

• Cells release signals that affect neighboring cells
• These signals act locally, without traveling in the bloodstream

Paracrine Regulation in the Pancreas

• Different cells in the pancreas (alpha, beta, delta) release hormones (glucagon, insulin, somatostatin) that affect neighboring cells in the pancreas

Endocrine Mechanism of Communication

• Hormones produced by endocrine glands travel through the bloodstream
• These hormones affect distant cells having specific receptors

Neuro-Endocrine Mechanism of Communication

• A nervous system stimulus triggers specialized neuro-endocrine cells to release hormones
• These hormones can initiate an appropriate response

Pheromones

• Chemicals secreted in sweat and other bodily fluids influencing the behavior of the opposite sex in the same species

Nervous and Endocrine Communication - Similarities

• Both share common messengers (e.g., epinephrine)
• Both are associated with the brain (hypothalamus)
• The systems are cooperative, with nerves secreting neurohormones, and some endocrine parts innervated directly by the nervous system

Nervous and Endocrine Communication - Differences

• Nervous system uses axons for unidirectional signaling, whereas the endocrine system uses the bloodstream
• Nerve impulses are fast (milliseconds), while hormonal responses are slower (seconds to days)

Amplitude vs. Frequency Modulation

• Hormone concentration is a slow (minutes to hours) amplitude modulation,
• Nerve impulses are rapid (milliseconds) frequency modulated

Controlling Hormone Secretion

• Hormone control depends on the rate of production, delivery, and degradation.
• Rates of synthesis and secretion are regulated (negative and positive feedback mechanisms)

Concentration of Hormone - As Seen By Target Cell

• Factors affecting hormone concentration in target cells include the rate of production, delivery and degradation/elimination.

Free Hormone

• Free hormone is the active form available for receptor binding.
• The fraction of free hormone is a critical factor in hormone response
• Clinical states of hormone excess/deficiency can be related to free hormone levels

Bound Hormone

• Bound hormones are inactive because they are combined with plasma proteins.
• Being inactive, they still significantly contribute to the circulatory pool of hormone

Synthesis and Secretion of Hormones

• Synthesis and secretion are the most important aspects of endocrine control
• Mechanisms include negative feedback and less commonly, positive feedback.

Negative Feedback Loops

• Hormones have feedback loops to regulate hormone levels
• A reduction in hormone (like in the thyroid section) causes the secretion of more hormone from the pituitary and hypothalamus to raise hormone levels

Positive Feedback Loops

• Feedback loops that enhance the production of hormones
• This is seen during child birth where levels of oxytocin are increased

Humoral Stimuli - Blood Chemistry

• Blood chemistry influences hormone secretion, with high and low levels of certain chemicals influencing the secretion of hormones to maintain a balance

Humoral Stimuli - Glucose Insulin

• Blood glucose levels influence the secretion of insulin
• Higher glucose levels cause higher insulin secretion

Neural Stimuli Control

• A neuron innervating an endocrine cell triggers stimulatory and inhibitory neurotransmitter secretion.
• This controls whether or not hormones are released

Control by Hormonal Stimuli

• The hypothalamus releases hormones to stimulate or inhibit anterior and posterior pituitary hormones
• The pituitary gland then releases hormones to target another endocrine gland leading to hormone production

Hormone Interaction

• Synergism occurs when two or more hormones produce similar effects
• Permissiveness implies one hormone needs another hormone for full effect,
• Examples include epinephrine, cortisol, and glucagon

Receptor Agonists and Antagonists

• Agonists—mimic the action of natural hormones/neurotransmitters
• Antagonists—block receptor binding, preventing natural hormone/neurotransmitter action

Agonists Mimic Normal Hormone Response

• Agonists bind to specific receptors to mimic a natural hormone response
• Phenylephrine– an example
• Used in specific medical treatments

Antagonists

• Antagonists bind to specific receptors
• They do not trigger a cellular response.
• Examples include androgen antagonist in prostate cancer treatment

Receptors

• Muscarinic Receptors
• Bind acetylcholine (ACh) from the autonomic nervous system
• Nicotinic Receptors
• Bind acetylcholine at neuromuscular junctions.

Test your knowledge on the functions of hypothalamic and pituitary hormones along with their roles in cell-cell communication. This quiz covers topics such as hormone regulation, signaling mechanisms, and autocrine control. Challenge yourself and see how much you know about these essential biological processes!