Life Sciences Grade 12 Revision 1 | Reflex Arc | Neuron | Human Brain

The diagram below shows part of the human brain.

Question

Identify part A.

Part A is the cerebellum.

It is located at the back of the brain and plays a vital role in balance, posture, and coordinating voluntary muscle movements.

Question

State TWO functions of part D.

Part D is the cerebrum. Its main functions include:

• It controls higher thought processes such as reasoning, intelligence, and memory.
• It is responsible for the interpretation of all sensory information, allowing us to understand and respond to what we see, hear, touch, taste, and smell.
• It also controls all voluntary actions

Question

Name the hormone secreted by gland C that has an effect on:

(a) Long bones

Gland C (the pituitary gland) secretes growth hormone (GH), which stimulates the growth and lengthening of long bones during childhood and adolescence. It works mainly by making the cells in the growth plates multiply, leading to an increase in bone size and overall body growth.

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(b) Mammary glands in the breasts

The pituitary gland also secretes prolactin, which activates the mammary glands to produce milk after childbirth. Prolactin helps maintain milk supply throughout breastfeeding and also supports recovery after pregnancy.

Question

State TWO ways in which the brain is protected.

• The brain is protected by the meninges, which are three tough, protective membranes that cover the brain.
• It is also be protected by the cranium, which is the skull bone.

Question

Describe the role of the hypothalamus in thermoregulation.

The hypothalamus helps regulate body temperature by:

• Receiving and interpreting impulses from temperature receptors in the skin.
• It then sends impulses to blood vessels in the skin to either constrict or dilate, controlling blood flow and heat loss.
• The hypothalamus also stimulates sweat glands to produce sweat for cooling when necessary. In this way, it maintains a stable internal body temperature.

Question

Part B is involved in homeostatic control of carbon dioxide concentration in the blood.

(a) State the location of the receptors that are stimulated by an increase in carbon dioxide concentration in the blood.

• These receptors are found in the carotid artery. They detect changes in carbon dioxide levels.

(b) Name the effectors that part B sends impulses to.

• The heart muscle, which increases the heart rate to help transport excess carbon dioxide to the lungs for removal.
• The diaphragm, which contracts more rapidly and strongly to increase the breathing rate and depth.
• The intercostal muscles, which also contract more actively to expand and contract the chest cavity, further increasing ventilation and aiding in the removal of excess carbon dioxide.

The diagram below shows a part of the human brain.