Biology Grade 8 Study Guide - Skin, Respiration, Nervous System, and Eye

Comprehensive practice flashcards covering human anatomy (skin, eye), the nervous and respiratory systems, respiration types, the menstrual cycle, and plant tropisms based on the Grade 8 Biology Study Guide.

What is the function of the sebaceous gland in the skin?

It secretes an oily substance to coat hairs and keep the skin and hair soft.

What are the characteristics and function of the Malpighian layer?

It consists of actively dividing cells that form other layers of the epidermis and contains melanin to protect the skin against ultra-violet rays.

What protein in the skin helps form a protective, waterproof layer on the outside?

Keratin

How is Scabies defined in the study guide?

An itchy skin condition caused by a tiny burrowing mite called Sarcoptic scabies, causing intense itching where the mite burrows.

What is the medical name for Athlete's Foot and what causes it?

Tinea pedis; it is a fungal infection that usually begins between the toes, often in people whose feet become sweaty in tight-fitting shoes.

What makes up the human nervous system?

The brain, spinal cord, and nerves.

What is the specific role of Interneurons?

They act as the 'middle man,' transmitting information between sensory and motor neurons, and play a key role in learning, memory, and planning.

Which part of the neuron conducts electrical impulses along the cell?

Axon

What is the function of the Myelin Sheath?

It insulates the axon to help protect the neuron cell and speed up the transmission of electrical impulses.

What is Cerebral palsy as described in the notes?

A group of conditions affecting movement and posture caused by damage to the developing brain, often before birth due to lack of oxygen.

What is the path air takes from the nose to the alveoli?

Air passes through the nose or mouth to the trachea, then into the two bronchi, then into smaller bronchioles, and finally ends at the alveoli.

What happens to the oxygen percentage when air is inhaled versus exhaled?

Inhaled air contains $21\%$ oxygen, while exhaled air contains $17\%$, because the body has used some of it.

What is the chemical equation for Aerobic respiration in humans?

$$\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}$$

What is the chemical equation for Anaerobic respiration in muscle cells?

$$\text{glucose} \rightarrow \text{lactic acid} + \text{energy}$$

What are the four overall stages of the average 28-day menstrual cycle?

1. Menstruation (loss of lining), 2. Lining starts to thicken, 3. Ovulation (around day 14), 4. Lining is maintained to accept a fertilized egg.

How do Oestrogen levels affect the menstrual cycle before day 14?

Oestrogen levels rise to peak just before day 14, causing the uterine wall to thicken and the egg to mature.

How do shoots and roots respond to gravity in geotropism?

The shoot has a negative response to gravity, while the root has a positive response.

Define Thigmotropism.

Growth in response to touch.

What is the function of the Choroid layer in the eye?

A black layer behind the lens that prevents light from reflecting around the eye and nourishes it with blood and oxygen.

What occurs at the 'Blind spot' of the eye?

It is where blood vessels and the optic nerve join the eyeball; there are no light-sensitive cells to detect image information.

Which parts of the eye are responsible for focusing an image and changing the lens shape?

The lens helps focus the image, and the ciliary muscles change the shape of the lens to bring images into focus.