Chapter 12 - Homeostasis

Chapter 12: Homeostasis

On a warm sunny day

First meal of the day?

Oops..where’s Lizzy?

Better luck next time

This time, its personal!

Swooping in for the meal

Got it…finally!

A meal at last

Food for thought 

Why is the bird (Kokkaburra) able to capture its prey (the lizard) effectively during cloudy weather compared to a sunny one?

Homeostasis 

Maintenance of a constant internal environment within a mammalian body

Negative Feedback Control

When T>set temp

When T=set temp (20°C)

When T<set temp

When T=set temp (20°C)

Homeostatic Temperature Control System Brain

Spinal Cord (Central Nervous System - CNS)

Nerves (eg. skin) (Peripheral Nervous System - PNS)

The Mammalian Skin

Sweat pore epidermis Sweat duct Blood capillaries

Erector muscle

dermis

Sebaceous gland Sweat gland Hair follicle Hair papilla

hypodermis

Bld vessel Nerve receptors

Adipose tissue

Forming “goose pimples” Layer of trapped still air  bad conductor of heat

Hair erector muscles contract  causing hair follicle to stand on end

Shivering

Muscles contract  produce more heat

Blood vessels near skin

Vasoconstriction Diameter of blood capillaries decrease

Heat loss is very little

Nerve receptors detect low temperature

CNS alerted

Blood capillaries constricts

Vasodilation Diameter of blood capillaries increase

Heat loss is very large

Nerve receptors detect high temperature

CNS alerted

Blood capillaries dilates

Losing heat to surrounding

Why does panting regulate the body temperature of this dog?

Ways of maintaining internal body temperature Muscular movement

Shivering

Vary diameter of Sweat glands blood capillaries produce sweat in varying amounts Vasodilation Vasoconstriction

Hair erector muscles contract

Produce more heat Form goose pimples  higher metabolic rate

Adipose Tissue  helps to prevent excessive body heat loss to the surroundings