5.5.9 Human Brain

Question 1

What are the regions of the brain? Where abouts?

Answer 1

Cerebrum (top)
Hypothalamus (above pituitary gland)
Pituitary Gland (infront and above spinal cord and medulla oblongata)
Cerebellum (bottom back)
Medulla Oblongata (bottom)
Spinal Cord (just behind medulla oblongata)

Question 2

What is the cerebrum? What does it do? What is its structure?

Answer 2

• Largest part of brain

Controls :
- Vision
- Hearing
- Speech
- Thinking
- Memory

Contains 5 lobes. Divided into 2 cerebral hemispheres. Each hemisphere controls opposite sides of the body.

Cerebral cortex (grey matter) is the thin outer layer containing cell bodies of neurones. Highly folded, increasing SA for more neurones. More neurones, so more connections, so greater ability of brain to carry out complex behaviors.

Beneath cerebral cortex is ‘white matter’, consisting of myelinated axons of neurones.

Question 3

What is the hypothalamus? What does it control? Functions?

Answer 3

Monitors blood flowing through it. If change is needed, it releases hormones or stimulates pituitary gland to release hormones.

Main Functions :
- Regulating body temperature
- Osmoregulation (hypothalamus is responsible for thirst)
- Regulating digestion
- Controlling endocrine function

Question 4

What is osmoregulation? How is it controlled?

Answer 4

• The monitoring of the concentration of blood
• If too concentrated posterior pituitary gland is stimulated to release ADH causing permeability of the collecting duct in the kidney to increase allowing for greater selective reabsorption of water into the blood hence increasing volume of water in the blood, so decreasing the concentration of blood

Question 5

How does the hypothalamus regulate digestion?

Answer 5

• Controls secretion of enzymes in gut and peristalsis
• Detects if blood nutrient levels are too low
• So generates feeling of hunger
• Food intake is increased (hopefully)

Question 6

How does the hypothalamus control endocrine function?

Answer 6

• Releases chemicals causing pituitary gland to release hormones
• Eg. In metabolism, growth, puberty, sleep, mood, etc

Question 7

What does the pituitary gland do? Anterior and Posterior?

Answer 7

• Produces range of hormones
• Some directly influence bodily processes
• Some stimulate release of further hormones from other glands in body

Anterior : Produces and releases
Posterior : Stores and releases hormones PRODUCED BY HYPOTHALAMUS (etc ADH or oxytocin)

Question 8

What does the cerebellum control?

Answer 8

• Motor coordination
• Eg. Balance (eyes, semicircular canals in ears, lots of muscles)
• Functions SUBCONSCIOUSLY (involuntary actions)

Question 9

What does the medulla oblongata control? How many centres?

Answer 9

Cardiac centre : Heart rate
Vasomotor centre : Blood pressure (controls contractions of smooth muscles in arteriole walls)
Respiratory centre : Breathing rate (inspiratory centre and respiratory centre)