Co-ordination and response in humans Flashcards
What is homeostasis?
the maintenance of a constant internal environment
What are the different examples of homeostasis in the body?
Temperature
Water
Glucose
Describe Temperature homeostasis
Thermoregulation
If too hot - Skin acts to increase heat loss
Hair erector muscles relax, makes hairs lie flat
Less air trapped near the skin surface
More heat lost by radiation
Sweat glands make sweat
Blood vessels near skin surface dilate, more blood gets near surface (vasodilation)
Increases heat loss
If too cold - Skin acts to reduce heat loss
Hair erector muscles contract, makes hairs stand upright
Traps warm air near skin surface
Less heat lost by radiation
Sweat glands stop making sweat
Blood vessels near the skin surface get narrower (vasoconstriction)
Less blood gets near surface
Reduces heat loss
Describe Water homeostasis
Osmoregulation
The kidneys control the water content of the blood
Too much - large volume of dilute urine
Too little - small volume of concentrated urine
The part of the brain Hypothalamus detects changes to internal conditions
Sends signals to other parts of brain
Creates the feeling of thirst
What is vasoconstriction?
Muscle in the walls of arteries contracts, so arteries get narrower
This means less blood flows into the capillaries in the skin
Therefore less heat is lost from the skin by radiation
Skin appears pale
What is vasodilation?
Muscle in walls of arteries relax, so arteries get wider
This means more blood flows into the capillaries in the skin
Therefore more heat is lost by radiation
Skin appears red
What does a co-ordinated response require?
A stimulus, a receptor and an effector
Whats a stimulus?
Change in the internal or external environment
Whats a receptor?
Detects stimulus eg. sense organ
Whats an effector?
Carries out response - muscle or gland
Whats a co-ordinator?
Carries out response e.g. brain
Whats a response?
Bodys reaction to the stimulus
How does the nervous system control responses?
Made of neurones
Messages transmitted in the form of electrical impulses
Messages transmitted along nerve fibres
Messages travel very quickly
Effects of message usually only last a very short while
The system is made of:
The CNS - which consists of the brain and spinal cord
Nerves - which branch out from the CNS to all parts of the body
What are the three types of nerve cells?
Sensory Neurones - Transmit more impulses from receptors to the CNS
Motor Neurones - Transmit nerve impulses from the CNS to effectors
Relay neurones - transfer impulses from the sensory to motor neurones
How does the hormonal system control responses?
Made of secretory cells
Messages transmitted in the form of chemicals called hormones
Messages transmitted through the blood system
Effects of messages usually last longer