# Endocrine System

Psychology I · Behavioral Biology · https://tryals.app/learn/psychology-i/endocrine-system

## Slow Chemistry and the Master Gland

While the nervous system fires fast millisecond signals across synapses, the **endocrine system** releases **hormones** into the bloodstream to affect distant organs for minutes, hours, or longer.

The **pituitary gland** is controlled by the **hypothalamus**. Its **anterior pituitary** synthesizes its own hormones, while the **posterior pituitary** only stores and releases oxytocin and vasopressin produced by the hypothalamus.

| Pituitary Part | Function | Examples |
| --- | --- | --- |
| **Anterior** | Synthesizes and releases own hormones | ACTH, Growth Hormone |
| **Posterior** | Stores and releases hypothalamic hormones | Oxytocin, Vasopressin |

## Stress Axes and Metabolic Glands

The **HPA axis** is the central stress pathway: the hypothalamus triggers the anterior pituitary, which prompts the adrenal cortex to release **cortisol**, with negative feedback shutting it down.

The **thyroid** sets baseline metabolic rate via thyroxine, and **gonads** release sex hormones.

| Adrenal Part | Control Pathway | Response Time & Chemical |
| --- | --- | --- |
| **Medulla** | Direct sympathetic nervous system | Instant, **adrenaline** |
| **Cortex** | Slow HPA cascade | Minutes to hours, **cortisol** |

**Common pitfall:** Confusing the fast adrenaline surge with the slow cortisol response. Both come from the adrenal gland, but via different pathways and timescales.

## Practice questions

6 of this lesson's 11 practice questions, with answers. The full set is in the app.

### 1. Select every statement that is TRUE about the endocrine system.

A. The hypothalamus controls the pituitary gland.
B. The anterior pituitary is controlled by the adrenal cortex.
C. The thyroid sets the body's baseline metabolic rate via thyroxine.
D. Hormones travel through the bloodstream to reach distant organs.
E. The posterior pituitary manufactures oxytocin and vasopressin itself.

**Answer:** A. The hypothalamus controls the pituitary gland.; C. The thyroid sets the body's baseline metabolic rate via thyroxine.; D. Hormones travel through the bloodstream to reach distant organs.

**Why:** Hypothalamic control of the pituitary, thyroid metabolic control, and bloodborne hormones are all true. The posterior pituitary only STORES oxytocin/vasopressin (the hypothalamus makes them), and the anterior pituitary is controlled by the hypothalamus, not the adrenal cortex.

Page: https://tryals.app/practice/psychology-i/endocrine-system/select-every-statement-that-is-true-about-the-endocrine-system

### 2. A nerve signal and a hormone can both raise the heart rate. The neural version is over in milliseconds; the hormonal one takes seconds to begin and minutes to wear off. Why is the endocrine route so much slower at both ends?

A. Because hormones act on the very same receptors as neurotransmitters but bind them more weakly.
B. Because hormone molecules are larger than neurotransmitters and therefore diffuse more slowly.
C. Because endocrine glands can only secrete their hormone gradually, a little at a time.
D. Because a hormone travels by blood and stops only when metabolised.

**Answer:** D. Because a hormone travels by blood and stops only when metabolised.

**Why:** A neuron has a wire and a gland does not: onset is limited by circulation time, and offset by metabolism, because nothing is actively clearing a synapse. Broadcast rather than point-to-point, which is why endocrine signalling can retune every tissue at once and keep them retuned for hours.

Page: https://tryals.app/practice/psychology-i/endocrine-system/a-nerve-signal-and-a-hormone-can-both-raise-the-heart-rate-the

### 3. Cortisol switches off the very signals that produced it. Why would a stress system be built to sabotage itself?

A. Because the adrenal gland would exhaust its cortisol supply without a brake
B. Because the hypothalamus can only sustain signalling for a limited period
C. Because the response is worth having briefly and damaging sustained
D. Because cortisol is toxic at any concentration and the body minimises total release

**Answer:** C. Because the response is worth having briefly and damaging sustained

**Why:** The off-switch is what makes the response safe to have. Cortisol is exactly right for a two-minute threat and corrosive for two years, so the axis winds itself down once the stressor passes. In chronic stress that feedback itself dulls, which is the mechanism behind Selye's exhaustion stage.

Page: https://tryals.app/practice/psychology-i/endocrine-system/cortisol-switches-off-the-very-signals-that-produced-it-why-would-a

### 4. If cortisol's negative feedback onto the hypothalamus failed, cortisol would settle at a new, lower baseline.

**Answer:** False

**Why:** False. Negative feedback is the *shut-off*: cortisol acting back on the hypothalamus and pituitary is what ends the stress response. Remove it and cortisol runs high and unchecked, which is broadly the picture in Cushing's syndrome, and part of why chronic stress damages the hippocampus.

Page: https://tryals.app/practice/psychology-i/endocrine-system/if-cortisols-negative-feedback-onto-the-hypothalamus-failed

### 5. Order the steps of the HPA axis, the body's central stress pathway.

**Answer:**

1. The hypothalamus releases a triggering hormone.
2. The anterior pituitary responds by releasing a second hormone into the blood.
3. That hormone prompts the adrenal cortex to release cortisol.
4. Rising cortisol acts on the body's stress response.
5. Cortisol feeds back to the hypothalamus and pituitary, shutting the cascade off.

**Why:** The hypothalamus triggers the pituitary, which triggers the adrenal cortex to release cortisol, and rising cortisol then feeds back to shut the cascade off. That final negative-feedback loop is what keeps cortisol from climbing without limit.

Page: https://tryals.app/practice/psychology-i/endocrine-system/order-the-steps-of-the-hpa-axis-the-bodys-central-stress-pathway

### 6. The adrenal gland runs two very different stress pathways. Sort each feature.

**Answer:**

- Fast: adrenal medulla -> adrenaline: Under direct sympathetic nervous control, acting within seconds, Released by the adrenal medulla
- Slow: HPA axis -> cortisol: A hormone cascade through the hypothalamus and pituitary, Released by the adrenal cortex, Effects build over minutes to hours

**Why:** Adrenaline comes fast from the adrenal medulla under direct sympathetic control; cortisol comes slowly from the adrenal cortex via the HPA hormone cascade. Same gland, entirely different control pathways and timescales - the lesson's central pitfall.

Page: https://tryals.app/practice/psychology-i/endocrine-system/the-adrenal-gland-runs-two-very-different-stress-pathways-sort-each