SPI Biology · Human Physiology
Control and Coordination
The brain and nerves send fast electrical messages, and the endocrine glands send slower chemical messages called hormones.
Why this matters
Five questions in the bank, four of them EASY: the largest part of the brain, an involuntary action, the nerve from the ear, the direction an impulse travels through two neurons, and the endocrine glands that sit in the brain. Learn which part of the brain does what and where each gland is.
Concept 1 of 3: Parts of the brain and voluntary actions
The brain has three parts. The front part, the cerebrum, is the thinking part and the largest. The back part looks after balance and the actions we never think about, such as the heartbeat. An action we choose is voluntary; one that goes on without our will is involuntary.
Definition
- Forebrain: cerebrum, the largest part. Thinking, memory, intelligence, the senses and all voluntary actions.
- Forebrain: hypothalamus, a small region that controls hunger, thirst and body temperature, and makes hormones.
- Hindbrain: cerebellum: balance, posture and smooth, exact movements (walking in a straight line, riding a cycle).
- Hindbrain: medulla: involuntary actions such as the heartbeat, breathing, blood pressure, vomiting and salivation.
- Spinal cord: controls reflex actions, such as pulling the hand away from a hot object.
| Part | Region | Controls |
|---|---|---|
| Cerebrum | Forebrain | Thinking, memory, senses, voluntary actions The cerebrum is the largest part of the brain. |
| Hypothalamus | Forebrain | Hunger, thirst, body temperature |
| Cerebellum | Hindbrain | Balance and posture |
| Medulla | Hindbrain | Heartbeat, breathing, vomiting (involuntary) |
| Spinal cord | Below the brain | Reflex actions |
Chosen actions: cerebrum. Balance: cerebellum. Heartbeat: medulla.
Practice this conceptself-check · 5 quick reps
The same idea in a practice question:
Practice questionEasy
Example 1 · Human Physiology · Control and Coordination
The largest part of our brain is
Cerebellum for the largest part
The names are close. The cerebrum is the largest part and does the thinking; the cerebellum is smaller, at the back, and keeps balance.
A skill is not involuntary
Riding a cycle or walking straight feels automatic once learnt, but we choose to do it, so it is voluntary. Involuntary actions, such as the heartbeat, go on even when we sleep.
Concept 2 of 3: Neurons, nerves and the direction of an impulse
A neuron is a long cell built to carry a message one way. The message comes in at the branched dendrites, passes the cell body, runs down the long axon and jumps a small gap, the synapse, to the dendrites of the next neuron. Each sense organ has its own nerve to the brain.
Definition
- Path in one neuron: dendrite, cell body, axon, nerve ending.
- Synapse: the gap between the nerve ending of one neuron and the dendrite of the next. A chemical crosses it.
- The impulse never runs backwards, from axon to dendrite.
- Optic nerve: eye to brain. Auditory nerve: ear to brain. Olfactory nerve: nose to brain.
- Reflex arc: receptor, sensory neuron, spinal cord, motor neuron, muscle.
| Nerve | Carries messages from | Sense |
|---|---|---|
| Optic nerve | Eye | Sight |
| Auditory nerve | Ear | Hearing |
| Olfactory nerve | Nose | Smell |
In a neuron: dendrite, cell body, axon, then across the synapse to the next dendrite.
Practice this conceptself-check · 4 quick reps
The same idea in a practice question:
Practice questionEasy
Example 2 · Human Physiology · Control and Coordination
Which nerve transmits sound impulse to brain form ear?
An impulse crossing into the next axon
At a synapse the message passes from the nerve ending of one neuron to the dendrite of the next, never straight into its axon or nerve ending.
Concept 3 of 3: Endocrine glands and where they sit
Endocrine glands pour hormones straight into the blood. The questions ask where a gland is and what its hormone does, so learn each gland with its place in the body.
Definition
- In the brain: hypothalamus, pituitary (growth hormone, the master gland) and pineal.
- In the neck: thyroid (thyroxine, needs iodine; lack of iodine causes goitre) and the parathyroids.
- In the chest: thymus.
- On top of the kidneys: adrenal glands (adrenaline, for emergencies).
- In the abdomen: pancreas (insulin, which lowers blood sugar; too little causes diabetes).
- Testes make testosterone; ovaries make oestrogen.
| Gland | Where | Hormone or job |
|---|---|---|
| Hypothalamus | Brain | Releasing hormones that control the pituitary |
| Pituitary | Brain | Growth hormone |
| Pineal | Brain | Melatonin (sleep cycle) |
| Thyroid | Neck | Thyroxine (needs iodine) |
| Parathyroid | Neck | Controls calcium in the blood |
| Thymus | Chest | Helps build immunity in children The thymus is in the chest, not the brain. |
| Adrenal | On top of the kidneys | Adrenaline |
| Pancreas | Abdomen | Insulin |
Practice this conceptself-check · 4 quick reps
The same idea in a practice question:
Practice questionEasy
Example 3 · Human Physiology · Control and Coordination
A pair of endocrine glands located in the human brain is
Parathyroid next to pituitary
The pituitary is in the brain, but the parathyroids are in the neck beside the thyroid. A pair is in the brain only if both glands are.
Pancreas as only a digestive organ
The pancreas makes pancreatic juice for digestion and also insulin for the blood. It is both a digestive gland and an endocrine gland.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (3)
Parts of the brain and voluntary actions5 rows
| Part | Region | Controls |
|---|---|---|
| Cerebrum | Forebrain | Thinking, memory, senses, voluntary actions The cerebrum is the largest part of the brain. |
| Hypothalamus | Forebrain | Hunger, thirst, body temperature |
| Cerebellum | Hindbrain | Balance and posture |
| Medulla | Hindbrain | Heartbeat, breathing, vomiting (involuntary) |
| Spinal cord | Below the brain | Reflex actions |
Chosen actions: cerebrum. Balance: cerebellum. Heartbeat: medulla.
Neurons, nerves and the direction of an impulse3 rows
| Nerve | Carries messages from | Sense |
|---|---|---|
| Optic nerve | Eye | Sight |
| Auditory nerve | Ear | Hearing |
| Olfactory nerve | Nose | Smell |
In a neuron: dendrite, cell body, axon, then across the synapse to the next dendrite.
Endocrine glands and where they sit8 rows
| Gland | Where | Hormone or job |
|---|---|---|
| Hypothalamus | Brain | Releasing hormones that control the pituitary |
| Pituitary | Brain | Growth hormone |
| Pineal | Brain | Melatonin (sleep cycle) |
| Thyroid | Neck | Thyroxine (needs iodine) |
| Parathyroid | Neck | Controls calcium in the blood |
| Thymus | Chest | Helps build immunity in children The thymus is in the chest, not the brain. |
| Adrenal | On top of the kidneys | Adrenaline |
| Pancreas | Abdomen | Insulin |
Watch out for (5)
- Cerebellum for the largest part→ Parts of the brain and voluntary actions
- A skill is not involuntary→ Parts of the brain and voluntary actions
- An impulse crossing into the next axon→ Neurons, nerves and the direction of an impulse
- Parathyroid next to pituitary→ Endocrine glands and where they sit
- Pancreas as only a digestive organ→ Endocrine glands and where they sit
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