HUBS L26 The hypothalamus, pituitary and growth hormone Flashcards
(22 cards)
Pituitary Gland – Location Explained
The pituitary gland is a small, pea-sized gland — about 1 cm wide.
It sits at the base of your brain, behind your nose and between your eyes.
It rests in a special bony “seat” called the sella turcica, which is part of a skull bone called the sphenoid bone.
The sella turcica is like a little depression or hollow (also called a fossa) that safely holds and protects the pituitary gland.
Analogy: Imagine the pituitary gland as a small marble sitting in a snug egg cup (the sella turcica), tucked deep at the bottom of your brain’s base.
Why was the pituitary gland formerly called the “Master Gland”?
Because it secretes several hormones that control other endocrine glands, like the thyroid, adrenal glands, and reproductive organs.
Hypothalamus and Pituitary Gland Relationship
It secretes its own special hormones that tell the pituitary gland what to do — like turning it “on” or “off” for certain hormones
Analogy: Think of the pituitary gland as a manager, and the hypothalamus as the CEO who gives the manager instructions.
What is the infundibulum?
The infundibulum is the stalk that connects the hypothalamus to the pituitary gland, allowing hormones and signals to pass between them.
What is the anterior pituitary (adenohypophysis) and where does it come from?
The anterior pituitary, or adenohypophysis, is made from epithelial tissue and makes up about 75% of the pituitary gland.
What are the two parts of the anterior pituitary?
Pars distalis – the larger, lower (inferior) part
Pars tuberalis – wraps around the infundibulum near the top (superiorly)
What is the pars distalis?
The pars distalis is the main, larger part of the anterior pituitary, located in the lower (inferior) region.
What is the posterior pituitary (neurohypophysis) made of and where does it come from?
The posterior pituitary (neurohypophysis) is derived from neuroectoderm and is mostly made up of supportive glial-like cells called pituicytes
What are the two parts of the posterior pituitary?
Pars nervosa – the larger, bulbar portion
Infundibulum – the stalk that connects the pituitary to the hypothalamus
What is the pars nervosa?
The pars nervosa is the larger, rounded part of the posterior pituitary that stores and releases hormones made by the hypothalamus.
What is the pars intermedia and what does it do?
The pars intermedia is the intermediate lobe of the pituitary gland, located between the anterior and posterior lobes.
It may produce melanocyte-stimulating hormone (MSH)
It’s mostly inactive in adults
The hypothalamus
(controls anterior through release hormones)
The hypothalamus controls how much hormone the anterior pituitary releases by sending it chemical signals called: Releasing hormones (RH): These tell the anterior pituitary to release a specific hormone.
Release-inhibiting hormones (RIH): These tell the anterior pituitary to stop releasing a specific hormone.
Analogy: Think of RH and RIH like traffic lights:
RH = green light → go! Release the hormone.
RIH = red light → stop! Don’t release it.
How the Hypothalamus Controls the Anterior Pituitary
The hypothalamus Hypothalamic Neurons
(controls posterior through action potential)
Specialised neurosecretory cells (neurons in the hypothalamus) synthesize hormones like: ADH (antidiuretic hormone), Oxytocin
These neurons have their cell bodies in the hypothalamus, but their axons extend into the posterior pituitary.
The hormones they make are stored in the posterior pituitary, and released into the bloodstream when needed
How the Hypothalamus Controls ADH and Oxytocin (Posterior Pituitary Hormones)
The hypothalamus autonomic center
(controls response through nerves)
The autonomic centers are like the control hubs for your body’s “autopilot system” — they make sure everything inside runs smoothly without you having to think about it.
These centers send signals through the autonomic nervous system (ANS), which has two main branches:
Sympathetic (fight or flight)(since preganglionic fibers extends to adrenal medulla realising hormones Adeline, noradrenaline)
Parasympathetic (rest and digest)
Endocrine Cells
Endocrine cells are specialized cells that synthesize and release hormones directly into the bloodstream, playing a crucial role in the endocrine system
Preganglionic Neurons and the Autonomic Nervous System
The autonomic nervous system is responsible for regulating involuntary bodily functions like heart rate, digestion, and breathing.
It uses a two-neuron pathway: preganglionic neurons and postganglionic neurons.
Preganglionic neurons are the first neurons in this pathway, located in the central nervous system (brainstem or spinal cord).
Their axons, called preganglionic fibers, extend from the central nervous system to autonomic ganglia.
These ganglia are collections of neuron cell bodies located outside the central nervous system.
Within the ganglia, preganglionic neurons synapse with postganglionic neurons.
Postganglionic neurons then project their axons to the target organs, such as the heart, lungs, and digestive system.
