The endocrine system, C3.1.12, C3.1.13

• What is adrenaline? Epinephrine, also known as adrenaline, is an amine hormone that is produced by the adrenal glands in preparation for vigorous activity. The release of adrenaline from the adrenal glands is controlled by the brain, producing a survival mechanism response known as 'fight or flight'.

  Adrenaline binds to cells with a transmembrane receptor, known as the adrenergic receptor. This receptor is a type of G- Protein-Coupled receptor.

  This binding triggers a signalling pathway, which is process in which binding of an extracellular chemical to a receptor is translated into changes in the cell.
• What are the effects of adrenaline secretion? - Causes liver and muscle cells to break down glycogen into glucose, which can be used for respiration

  - Bronchi and bronchioles dilate, as smooth muscles relax, widening the airways for increased air flow.

  - Ventilation rate then increases

  - Speeds up the firing of the sinoatrial node, which increases heart rate and moves blood to tissues faster.

  Increases the strength of cardiac contraction, allowing an increased volume of blood to be moved with each heartbeat.

  - Dilates arterioles that carry blood to the skeletal muscles, redirecting blood flow to areas that are crucial for dealing with the immediate threat via vasodilation

  - Constrict arterioles that carry blood to the gut, kidney and skin, redirecting blood from non-crucial areas via vasoconstriction.

  - Increases blood flow, oxygen and glucose to skeletal muscles, maximising its ability to produce ATP and perform contractions.
• What are the primary muscles used in the fight or flight response? Psoas- pulling the legs up/forward

  Hamstrings- bending the knee and extending the hip

  Abductors- moving the legs away from each other

  Adductors- bringing the legs together
• What is the hypothalamus? The hypothalamus is a small brain region that has major roles in system integration. It consists of a thin wall of tissue located on the left and right sides of the third ventricle and below it. Ventricles are spaces inside the brain, that are filled with cerebrospinal fluid.

  The hypothalamus contains nuclei, each one operating one or more specific control systems, using information from a variety of source to do so.

  The nuclei contain sensors for blood temperature, blood glucose concentration, osmolarity, and hormone concentration, and can also receive signals from sense organs (directly or indirectly), as well as inputs from other brain regions (such as the hippocampus).
• What is the pituitary gland? The hypothalamus links the nervous system to the endocrine system via the pituitary gland. The pituitary gland is located directly below the hypothalamus, connected via a narrow stalk.

  It consist of two distinct parts: the anterior lobe and the posterior lobe.

  Both lobes secrete hormones into capillaries under the direction of nuclei in the hypothalamus.
• What hormones does the anterior pituitary secrete? HGH

  TSH

  LH

  FSH

  prolactin
• What hormones does the posterior pituitary secrete?

  ADH

  Oxytocin
• What is osmoregulation (example of process based on system integration by the hypothalamus and pituitary gland)? Osmoreceptors in the hypothalamus monitor blood solute concentration constantly. This influences how much ADH is produced by neurosecretory cells in the hypothalamus. The axons of these neurosecretory cells transport the ADH to the pituitary gland, where it is secreted into capillaries.
• What is puberty (example of process based on system integration by the hypothalamus and pituitary gland)? The hypothalamus initiates puberty by secreting GnRH, a neurohormone that stimulates secretion of LH and FSH by the pituitary gland. These hormones stimulate the secretion of testosterone in males, and oestradiol and progesterone in females, leading to puberty.