Chapter 13: Hormones and Sex

Topics Covered in this Unit:
1. Hormones and Sex
2. Neuroscience of Emotion
3. Mental Disorders
Learning Objectives for Hormones and Sex:
- Explain the process by which hormones exert effects on the body.
- Describe hormone regulation by glands and organs.
- Identify major endocrine glands and their released hormones.
- Provide examples of how hormonal changes influence body and behavior.

Definition: The endocrine system communicates through hormones (chemical messengers) transported via the bloodstream to target tissues.
Key Concepts:
- Hormones are released by endocrine cells into the bloodstream.
- Targets tissues that receive blood supply.

Two Types:
1. Neurotransmitters: Released at synapses, fast actions, specific effects, and cleared quickly.
2. Hormones: Released into the bloodstream, slower actions, longer-lasting effects.
- Comparison of Actions:
- Neurotransmitters: Fast (specific synaptic action).
- Hormones: Slower (must travel through circulatory system).
- Exocrine: Refers to chemicals released outside of the body (e.g., tears, sweat).

Three Main Families:
1. Amino Acid Derivatives:
- Modified single amino acids (e.g., epinephrine, melatonin).
1. Peptide Hormones:
- Short chains of amino acids (e.g., ACTH, TSH).
1. Steroid Hormones:
- Derived from cholesterol, includes sex hormones (e.g., estrogens, androgens).
Hormone Binding:
- Peptide and Amino Acids: Bind to membrane-bound (metabotropic) receptors.
- Steroid Hormones: Can pass through cell membranes and bind to intracellular receptors, affecting gene transcription directly.

Pineal Gland:
- Releases melatonin, regulates sleep-wake cycles; levels rise at night for drowsiness.
Hypothalamus:
- Regulates other glands but doesn’t have direct behavioral effects; produces stimulating and inhibiting hormones.
Pituitary Gland:
- Posterior Pituitary: Physical connection with the hypothalamus, releases hormones like vasopressin (water balance) and oxytocin (pair bonding).
- Anterior Pituitary: Not connected to hypothalamus; releases tropic hormones that influence the activity of other glands, includes growth hormone.

Vasopressin (ADH): Maintains water/salt balance, higher levels at night to prevent urination during sleep.
Oxytocin: Increases during bonding activities, significant in maternal behaviors (e.g., breastfeeding).

Importance of understanding the endocrine system in relation to behavior and physiology.
Will continue exploring hormonal functions in upcoming classes, particularly focusing on sex hormones and their influence on sexual behavior.

The thyroid gland plays a crucial role in growth, development, and metabolic rate.
Key hormones produced by the thyroid:
- Thyroxine: The primary hormone that regulates metabolism.
- Triiodothyronine: Another important hormone influencing metabolism and growth.
- Calcitonin: Regulates blood calcium levels.

Hyperthyroidism:
- Condition characterized by an overproduction of thyroid hormones.
- Results in a significantly accelerated metabolism.
- Common symptoms: difficulty in gaining weight, increased heart rate, anxiety.
Hypothyroidism:
- Condition characterized by insufficient hormone production.
- Leads to a slowed metabolism, often resulting in weight gain.
- Symptoms may include hair loss and low energy levels.
- Personal anecdote: Referring to a dog that experienced weight gain and hair loss due to hypothyroidism.

Thyroid hormone production depends on iodine.
Historical context: Before iodized salt, iodine deficiency was common, leading to goiter (swelling of the thyroid).
This swelling occurs due to a buildup of hormones from the hypothalamus and pituitary gland attempting to stimulate the thyroid.

The adrenal gland is located on top of the kidneys, but not part of them.
HPA Axis: Stands for hypothalamus, pituitary gland, and adrenal gland, involved in physiological stress response (fight or flight).

Responsible for the release of:
- Glucocorticoids: Involved in metabolism and blood sugar regulation by transforming proteins into glucose.
- Mineralocorticoids: Regulate sodium and potassium balance in the body.
- Androgens: Related to sex characteristics, affecting body hair.

Releases epinephrine (adrenaline) and norepinephrine (noradrenaline).
These hormones are crucial for the body’s fight or flight response, increasing heart rate and blood circulation.

Produces significant hormones for sugar metabolism:
- Insulin: Lowers blood sugar levels by facilitating sugar uptake in cells.
- Glucagon: Raises blood sugar levels by triggering the liver to release glucose.

Type 1 Diabetes: Characterized by inability to produce insulin (often genetic).
Type 2 Diabetes: Characterized by insulin resistance; often associated with lifestyle factors such as diet and exercise.

Hormones released from the stomach and intestines regulate hunger and satiety:
- Ghrelin: Increases hunger signals when the stomach is empty.
- Gastrin & Cholecystokinin: Trigger feelings of fullness when food is present.
Ongoing research in the gut-brain axis shows potential connections between gut hormones and mood disorders such as anxiety and depression.

Gonads produce sex hormones responsible for development and reproductive functions.
- Ovaries: Produce estrogens and progestins, responsible for female characteristics.
- Testes: Produce testosterone, responsible for male characteristics.
Both males and females produce all types of sex hormones, just at different levels.

Endocrine cells release hormones into the bloodstream to regulate various bodily functions.
Hormones are slower acting but longer-lasting compared to neurotransmitters.
Hormones can be classified as amino acid derivatives, peptides, or steroids.
Each major endocrine gland serves distinct biological functions and releases specific hormones.