# The Endocrine System

Psychology I · Psychophysiology · https://tryals.app/learn/psychology-i/the-endocrine-system

## The Chemical Postal Service

Alongside the fast electrical nervous system runs a slower chemical one: the **endocrine system**, a network of **glands** that secrete **hormones** directly into the bloodstream. Where a neuron is fast and targeted, a hormone is slow, widespread, and long-lasting.

The **pituitary gland** is the master gland, directed by the **hypothalamus**, where nervous and endocrine systems meet. Other key glands include the **thyroid** (metabolism), **adrenal glands** (stress), and **gonads** (sex hormones).

| System Feature | Nervous System | Endocrine System |
| --- | --- | --- |
| **Speed** | Milliseconds | Seconds to hours |
| **Target** | Specific cells | Widespread via blood |
| **Duration** | Brief | Long-lasting |

## The HPA Axis & Stress

The stress response runs along the **HPA axis**: the **hypothalamus** signals the **pituitary**, which signals the **adrenal glands** to release **cortisol**, our main stress hormone. Cortisol mobilizes energy and feeds back to shut the loop down.

| Stress Response | Fast Adrenaline | Slow Cortisol (HPA) |
| --- | --- | --- |
| **Timing** | Seconds | Minutes to hours |
| **Pathway** | Sympathetic nerves | Bloodstream |

> **Common pitfall:** Thinking the endocrine system is just a slower copy of the nervous system. Hormones reach many organs at once and effects can last for hours or years.

## Practice questions

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

### 1. Cortisol acts back on the hypothalamus and pituitary to increase its own release, which is why stress escalates.

**Answer:** False

**Why:** False. The feedback is *negative*: cortisol shuts down its own release, because the response is expensive, sustained cortisol suppresses immunity, disrupts sleep and damages the hippocampus. Chronic stress is partly the failure of that shut-off, which is why duration does the damage rather than intensity.

Page: https://tryals.app/practice/psychology-i/the-endocrine-system/cortisol-acts-back-on-the-hypothalamus-and-pituitary-to-increase-its

### 2. The nervous system and the endocrine system both carry signals through the body. Why does an organism need both, rather than one well-designed system?

A. Because the nervous system evolved later and has not yet replaced the endocrine system.
B. Because the endocrine system serves as a backup in case the nervous system is damaged.
C. Because they solve different problems: fast and addressed, or slow and broadcast.
D. Because hormones can reach organs the nervous system does not innervate, which is the only difference.

**Answer:** C. Because they solve different problems: fast and addressed, or slow and broadcast.

**Why:** The two occupy different points on one trade-off: a neuron delivers to a connected target in milliseconds and is cleared at once; a gland reaches every tissue with the receptor and acts until metabolised. The stress response uses both in sequence, sympathetic nerves within a second, the HPA axis over minutes and hours. Same threat, two timescales.

Page: https://tryals.app/practice/psychology-i/the-endocrine-system/the-nervous-system-and-the-endocrine-system-both-carry-signals

### 3. Order the steps of the HPA axis, the body's slow stress pathway.

**Answer:**

1. The hypothalamus signals the pituitary gland.
2. The pituitary signals the adrenal glands.
3. The adrenal glands release cortisol.
4. Cortisol mobilizes energy for the stress response.
5. Cortisol feeds back to shut the axis down.

**Why:** Hypothalamus triggers pituitary, which triggers the adrenals to release cortisol, which mobilizes energy and then feeds back to shut the cascade down. That closing negative-feedback loop keeps cortisol from climbing without limit.

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

### 4. The adrenal gland drives two stress responses on different timescales. Sort each feature.

**Answer:**

- Fast: sympathetic adrenaline: Surges within seconds under direct sympathetic control, Delivers an immediate jolt of energy for fight-or-flight
- Slow: HPA cortisol: Builds over minutes to hours via a hormone cascade, Runs through hypothalamus, then pituitary, then adrenal glands

**Why:** Adrenaline surges in seconds under direct sympathetic control; cortisol builds over minutes to hours through the HPA cascade. Same stress, two systems: a fast neural jolt and a slow hormonal response.

Page: https://tryals.app/practice/psychology-i/the-endocrine-system/the-adrenal-gland-drives-two-stress-responses-on-different

### 5. The pituitary is called the master gland yet is directed by the hypothalamus. What does that arrangement accomplish?

A. It allows hormones to be produced in two places at once
B. It connects the nervous and endocrine systems
C. It slows hormone release to prevent overreaction
D. It provides a backup in case the pituitary fails

**Answer:** B. It connects the nervous and endocrine systems

**Why:** The hypothalamus is the translator. The HPA axis begins with a perception and ends in the adrenal cortex, which is only possible because a neural structure controls an endocrine one.

Page: https://tryals.app/practice/psychology-i/the-endocrine-system/the-pituitary-is-called-the-master-gland-yet-is-directed-by-the

### 6. A near-miss on the motorway makes your heart pound within a second, and you still feel shaky twenty minutes later. Two systems are running. What separates them?

A. The first is voluntary and the second is not
B. They are the same system measured at two points in time
C. Speed and route: a second and done, or minutes and lingering
D. One handles physical threats and the other psychological ones

**Answer:** C. Speed and route: a second and done, or minutes and lingering

**Why:** Two axes on two timescales: the sympathetic-adrenal route is wired and near-instant, the HPA route is hormonal and slow to start and stop. The shakiness afterwards is the second one still clearing, and it is why a two-second event can occupy your physiology for half an hour.

Page: https://tryals.app/practice/psychology-i/the-endocrine-system/a-near-miss-on-the-motorway-makes-your-heart-pound-within-a-second

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

A. One small structure sits above the rest of the endocrine system and directs it.
B. Cortisol's negative feedback limits the duration of the stress response.
C. A surge of adrenaline reaches every tissue at once, because it travels by blood rather than by nerve.
D. The thyroid sets the body's baseline metabolic rate.
E. Hormones act faster than nerve signals because they travel in the blood.

**Answer:** C. A surge of adrenaline reaches every tissue at once, because it travels by blood rather than by nerve.; D. The thyroid sets the body's baseline metabolic rate.; E. Hormones act faster than nerve signals because they travel in the blood.

**Why:** Hypothalamic control of the pituitary, bloodborne hormones, and cortisol's negative feedback are true. The endocrine system is slower than the nervous system, and the gonads (not the thyroid) release sex hormones - so those are false.

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