Homeostasis Flashcards
Briefly explain what is meant by the term homeostasis.
Homeostasis refers to the way in which the body maintains a stable internal environment despite changes to the internal and external environment.
What is meant by the term negative feedback in relation to homeostasis?
Negative feedback refers to the way the body responds to reverse the direction of change in order to main homeostasis.
The body requires three basic components to achieve negative feedback. What are they?
The three components necessary to maintain homeostasis are a sensor (or detector), a control centre (or integrator) and an effector mechanism/s.
Most of the homeostatic adjustments made by our body are the result of negative feedback. Provide at least two examples.
Examples of negative feedback include thermoregulation, heart rate, blood pressure, fluid balance, respiratory rate, plasma pH and blood glucose levels.
What is meant by the term positive feedback?
Positive feedback occurs when the body responds to a change by increasing that change even further in the same direction.
Provide an example of a positive feedback mechanism.
Labour (childbirth), breastfeeding, coagulation (blood clotting) and the transformation of pepsinogen into pepsin.
What are the three layer of the skin (from most superficial to deepest)?
Epidermis, dermis and subcutaneous fat (hypodermis).
Melanocytes, keratinocytes and merkel cells are all found in the epidermis. What do they do?
Melanocytes produce the brown/black pigment melanin that helps to protect the skin from ultraviolet (UV) radiation present in sunlight. Keratinocytes produce keratin which helps to waterproof the epidermis and is an important component of hair and nails. Merkel cells respond to gentle, localised pressure and are particularly abundant on the surface of the fingers.
Where would you find arrector pili muscles and what is their function?
Arrector pili muscles are found in the dermis attached to the side of a hair follicle. When we are cold, they contract to allow the hair to stand upright and trap an insulating layer of air next to the skin.
Where would you find sebaceous glands and what is their function?
Sebaceous glands are found in the dermis attached to the side of a hair follicle. They secrete a waxy substance called sebum onto the hair follicle (or directly onto the skin) which provides a water-resistant coating.
Explain the difference between shell and core temperature?
Shell temperature is the temperature of the skin’s surface and may vary considerably according to the temperature of the surrounding environment. Core temperature is the temperature of the internal organs and the blood (about 36.5– 37.5°C).
Name the four ways in which the body gains/loses heat
Radiation, conduction, convection and evaporation.
Which part of the brain controls thermoregulation?
The hypothalamus.
What is meant by the term vasoconstriction and how does this help to retain heat when we are cold?
Vasoconstriction refers to narrowing (constriction) of the blood vessels that provide the dermis with blood. This process ensures that heat carried by the blood is added back to the core rather than lost to the atmosphere via radiation.
What is meant by the term vasodilation and how does this help to lose heat when we are hot?
Vasodilation refers to widening (dilation) of the blood vessels in the dermis resulting in increased blood flow to the skin and additional heat loss via radiation.
