Human and Plant Biology: Homeostasis, Thermoregulation, Blood Sugar, and Tropisms

Cornea Lens: More spherical lens with shorter focal length

Thinner lens with longer focal length (requires less refraction)

Suspensory Ligaments: Distant = flat; Near = round/thick

Homeostasis: Maintenance of a constant internal environment despite changes in surroundings.

Control Center: The hypothalamus in the brain decides on the appropriate response. Receptors: In the skin and brain, detect changes in the body. Effectors: E.g., sweat glands, body hair, and thyroid glands change to increase/decrease body temperature.

Thermoregulation: If the body is too cold or hot, body temperature is adjusted to what it should be (negative feedback mechanism). It involves receptors linked to the hypothalamus, which monitors core body temperature in the brain. Impulses are sent to the skin, and the skin reacts to changes in body temperature.

Receptors detect that the body is too cold. Impulses are sent to the control center (brain). The control center determines the best response. Impulses are sent to arterioles. Arterioles near the skin get smaller. Shivering: Muscles generate heat through respiration. Sweat glands stop sweating. Hairs stand up, trapping warm air near the body, resulting in less body heat loss.

(Vice versa for too hot - Vasodilation)

Food is digested, and sugar (glucose) is produced.

Sugar levels in the blood that are too high result in hyperglycemia, while levels that are too low result in hypoglycemia.

The hormone insulin controls levels of sugar.

An increase in glucose leads to glucose moving down metabolic pathways, resulting in toxic metabolites which cause kidney damage, cardiovascular issues, neurological problems, and damage to the retina, feet, and legs.

Can cause confusion, abnormal behavior, or both. It can also lead to visual disturbances, loss of consciousness, and seizures.

Tropisms: A response to stimuli that can be negative or positive.

Plants are very sensitive, and their growth is affected by their environments. They respond to three types of stimuli: water, light, and gravity.

Plants grow towards the light.

Auxins are made at the top of the shoot and move down the stem, speeding up growth in a shoot.

Shoots grow up (negative tropism).

Roots grow down (positive tropism).

Auxins slow growth in roots.

Roots grow towards water.