homeostasis skin & temperature control. learning objectives 12.1 principles of homeostasis a)...

HomeostasisSkin & Temperature Control

Learning Objectives12.1 Principles of Homeostasis

a) Define homeostasis (b) Explain the basic principles of

homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedback

Homeostasis Homeostasis is

defined as the maintenance of a constant internal environment.

Changes in body temperature may result in enzyme inactivation or denaturation.

Any drastic changes in our blood and the surrounding tissues fluid will affect chemical reactions in the tissue cells and will harm the body.

Cells must be bathed in tissue fluid of the correct pH and water potential. Enzyme reaction will be affected.

Negative Feedback Control The internal environment of our bodies

MUST have certain conditions within tolerable limits to continue the healthy functioning.

Done by NEGATIVE FEEDBACK control. Used to control blood sugar concentration,

water concentration & temperature of the blood.

Negative Feedback A stimulus, which is the change in the

internal environment A receptor that can detect the stimulus A self-regulatory corrective mechanism A negative feedback to the receptor

StimulusCondition increases

Receptors detects it Corrective

mechanism

Condition decreases

StimulusCondition decreases

Receptor detects it

Correctivemechanism

Condition rises

Normal condition

Organs involved in Homeostasis1. Skin (helps in temperature regulation)

2. Kidneys (helps in the water concentration of the body)

3. Brain (MASTERMIND)

4. Pancreas (produces insulin that helps in the control of sugar concentration in the blood)

Learning Objectives 12.2 Structure and function of the skin (c) Identify on a diagram of the skin: hairs, sweat

glands, temperature receptors, blood vessels and fatty tissue

(d) Describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the brain

Skin Largest organ of the human body. An important sense organ Barrier between the body and the external

environment Organ that regulates our body temperature.

Epidermis outer layer of the skin :-a. Cornified layer (dead cells) Protects the body from water loss, invasion of

microbes & mechanical, thermal & chemical damage.

b. Granular layer New cells undergo cell divisionc. Malpighian layer to replace dead cells from the cornified layerpigmented cells (melanin) protects our skin against

harmful UV light of the sun

Functions of the Epidermis

1. Layer is water-resistant (waterproof)

2. Prevents evaporation of water from skin

3. Prevents germs from entrying into the body.

4. Protective layer, preventing mechnical injury.

Dermis Consists mainly of fibrous tissue and many other

structures:-(a) Blood vessels numerous blood vessels Arterioles that carry blood are controlled by vasometer

nerves. Nerves bring about contraction & dilation of the

arteries. Arterioles dilate (vasodilation) --> more blood is sent to

the skin. Arterioles contract (vasoconstriction) --> less blood is

sent to the skin.

Dermis(b) Hair Common feature of mammals. Grow inside the hair follicle At the base of the follicle is a mass of tissue

containing blood capillaries. Attached to the hair follicles are the “hair

erector” muscles. (contract --> causes the hair to stand)

Dermis(c ) Sweat glands sweat is secreted in the sweat glands. Sweat glands ---> sweat duct ---> sweat pore

surface of skin. Sweat = urea + water + salt (sodium chloride)

Dermis(d) Temperature receptors nerve endings are found in the epidermis and

dermis. Form sense organs Enable us to sense pain, pressure and

temperature changes in the external environment.

NERVE ENDINGS

Dermis(e) Fatty Tissue

--> Fat cells are present where fat is stored.

Dermis(f) Sebaceous glands 2 glands open into each hair follicle. Secreting an oily substance (sebum) into hair

follicle. Sebum lubricates the hair and keeps the skin

soft and smooth. Prevents dehydration of the skin. Has an antiseptic action.

Control of body temperature

Skin Able to detect temperature change in the

external environment. A change in atmospheric temperature -->

detected by temperature receptors on the skin

--> start some mechanisms to control the temperature.

The Brain Hypothalamus is the control centre for

temperature. Detects temperature changes in the blood.

What happens when temperature rises?

Hypothalamus triggers off the following:-1. Decreased metabolic rate of the cells, resulting in

less heat being produced.2. Relaxation of skeletal muscles to reduce heat

production. Causes the hair to lie flat3. Vasodilation causing arterioles to increase blood

supply to the skin . More heat can be lost through the skin.

4. More sweat is produced. As sweat is removed more latent heat is removed.

What happens when temperature falls?

(a) Increased metabolic rate, resulting in more heat being produced.

(b) Shivering due to the contraction of skeletal muscles. (increases heat production)

(c) Causes hair to stand.(d) Vasoconstriction causing arterioles in the

skin to constrict.(e) Blood is diverted from the skin to reduce

heat loss.

Body Temp 37 C

Detected by hypothalamusRise in Blood

Temperature

Heat releasedDuring exercise

Heat loss

Body Temp 37 C

Increased sweatingVasodilation

Coldenvironment

Drop in bloodtemperature

Blood temprises

Decreased sweatingVasoconstriction

shiveringDetected by

hypothalamus

Regulating Body Temperature - on a Hot Day

April 19, 2023

April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 35

Stimulus

Blood and skin temperatures rise



Stimulus


Receptor

Temperature receptors detect changes and send nerve impulses to the brain



Stimulus


blood capillaries

hair folliclehair

arteriole

erector muscle

Receptor


Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts



Stimulus


Receptor



arteriole

capillariesskin surface

Arterioles in skin dilate

1

More blood flows to capillaries in skin

2

3

Greater heat loss

4

Shunt vessels constrict



Stimulus



sweat duct

sweat pore

sweat gland

Sweat glands more active

Sweat production increases

More latent heat lost as sweat evaporates

6

7

5


Receptor



Stimulus


Hair erector muscles in skin relax

erector muscle

blood capillaries

hair folliclehair

arteriole

8

Receptor





Stimulus


Receptor



Corrective Mechanism

Increase in heat loss and decrease in heat production



Stimulus


Receptor





Decreased metabolic rate reduces heat production



Stimulus


Receptor





Blood temperature returns to normal levels




Stimulus


Receptor






Negativefeedback



Regulating Body Temperature - on a Cold Day

April 19, 2023


Stimulus

Blood and skin temperatures fall



Stimulus


Receptor




blood capillariesarteriole

hair hair follicle

Stimulus


Receptor



erector muscles



Stimulus


Receptor


Less blood flows to capillaries in skin

Arterioles in skin constrict

Shunt vessels dilate

skin surfacecapillaries

arteriole

1

2

3

Less heat loss

4




Sweat glands less active

Sweat production decreases

Less latent heat lost

sweat pore

sweat duct

sweat gland

Stimulus


Receptor



56

7


Hair erector muscles in skin contract


erector muscles

blood capillariesarteriole

hair hair follicle

Stimulus


Receptor



8



Shivering occurs when insufficient heat is produced

Stimulus


Receptor


Hypothalamus of brain is

stimulated and sends nerve impulses to relevant body parts


Decrease in heat loss and increase in heat production



Stimulus


Receptor




Increased metabolic rate increases heat production





Stimulus


Receptor












Negativefeedback


Stimulus


Receptor



HomeostasisHomeostasis (Concept Map)April 19, 2023


HOMEOSTASIS

The maintenance of a constant internal environment


Principles of Homeostasis

HOMEOSTASIS



Stimulus

Change in internal environment

HOMEOSTASIS




Stimulus


HOMEOSTASIS



Receptors

Detect the change


Stimulus


HOMEOSTASIS



Receptors

Detect the change

Self-corrective Mechanism

To rectify the change


Stimulus


HOMEOSTASIS



Receptors

Detect the change



Examples

Regulation of blood glucose concentration


Stimulus


HOMEOSTASIS



Receptors

Detect the change



Examples


Regulation of blood water potential


Stimulus


HOMEOSTASIS



Receptors

Detect the change



Examples



Regulation of body temperature



Stimulus Receptors Self-corrective Mechanism Negative Feedback


Detect the change


Examples



Regulation of body temperature

The reverse effect of the change

HOMEOSTASIS


homeostasis skin & temperature control. learning objectives 12.1 principles of homeostasis a)...

Documents

skin slide

blood slide

receptor slide

brain slide

negative feedback slide

normal condition slide

homeostasis homeostasis

skin surface