Download 36.5 – 37.2 ˚c

Anatomy and Physiology for
Health and Social Care
P5
Homeostasis
Homeostasis Definition
Homeostasis means “staying the same”
It is the technical term for the process of
maintaining a constant internal environment
despite changes happening externally.
Exercise
In pairs think about:
We are able to live in both hot and cold
countries because our bodies have the ability
to regulate temperature. What would happen
if we could not regulate our temperature?
What do we mean by our internal
environment?
• It is our tissue fluid (lymph) in which all of our
cells are bathed.
• Every substance must pass through the fluid
to move to and from our cells.
• Tissue fluid is derived from blood, so blood
forms part of our internal environment.
• Our enzymes operate in a narrow range of
temperature and pH and can only work
effectively if conditions are maintained.
What do enzymes do?
• deliver nutrients,
• carry away toxic wastes,
• digest food,
• Clean and purify the blood,
• deliver hormones by feeding the endocrine system,
• balance cholesterol levels,
• feed the brain and
• cause no harm to the body.
All of these factors contribute to the strengthening of the
immune system
The Negative Feedback System
Detector
Controller
Effector
Feedback
Loop
Reference
Point
What needs to be regulated
•
•
•
•
Heart rate
Breathing rate
Body temperature
Blood glucose
Regulation of Heart Rate
Controlled by the autonomic nervous system
It has 2 branches:
The Sympathetic - accelerates the heart
The Parasympathetic – slows it down
Like a brake and an accelerator in a car
The effects of stimulating the
sympathetic nervous system
• Heart rate increases
• Blood flow increases to muscles, lungs and brain
but decreases to gut and kidney
• Breathing rate increases
• Sweat production increases
• Muscles of hairs contract
• Bladder and anal sphincters contract
• Glycogen converted into glucose in the liver
• Iris in the eyes dilate
Control of Heartbeat during exercise
• The cardiac centre is found in the medulla of
the brain.
• It receives signals from chemoreceptors which
are receptors that detect chemicals
Regulation of Breathing
• Most of the time we do this on AUTOMATIC PILOT
• Only when we take deep breaths, speaking,
holding our breath do we control our breathing.
• Controlled by the respiratory centre in the
medulla of the brain.
• The medulla controls nerves going into the
intercostal muscles and the diaphragm muscles.
• Normal breathing is a homeostatic mechanism
What happens when we breathe
• We breathe in when the respiratory centre sends
impulses to the intercostal and diagphram
muscles they contract and the lungs inflate.
• This inflation sends impulses to the respiratory
centre which stops sending impulses to the
intercostal and diagphram muscles.
• These muscles then relax
• They are no longer stimulated by the impulses
from the respiratory centre so it starts up again.
Control of Temperature
• Temperature of cells must be maintained at a
certain level to stop the structure of enzymes
being destroyed.
• Normal body temperature is?
36.8˚c
(36.5 – 37.2 ˚c)
Exercise
What would these lead to?
•
•
•
•
•
•
Below 25 ˚c
32 ˚c
36.5 - 37.2 ˚c
Above 37.2 ˚c
Above 38 ˚c
Above 43 ˚c
•
•
•
•
•
•
Lead to death
Hypothermia
Normal
Fever
Heat exhaustion
Death
Temperature
• Core body temperature is the one concerned
with operating enzymes
• Surface temperature can fluctuate rapidly
Question:
How do we gain heat
How do we loose heat
Heat
Gain
• Metabolism of food
• Absorbing solar energy
from objects, from the
ground and connections
with the ground
Loss
• Evaporation
• Conduction
• Convection
• Radiation
Regulation of Body temperature
• Is the role of the hypothalmus
• It sends nerve impulses to muscles, sweat
glands and skin blood vessels to cause
changes that counteract the external changes
• The skin is the main organ of
thermoregulation
Body responses
Cooling
• Speeds up metabolism
• Shivering to produce
heat
• Vascoconstrictions
Heating
• Slows down metabolism
• Sweating
• Vasodilation
• insulation
Control of blood glucose
• Glucose in the blood is referred to as blood
sugar level.
• The cells use glucose for respiration
• Carbohydrate levels fluctuate
• Cells need a constant supply of glucose
• Achieved by hormones interacting with
glycogen stored in the liver.
Hormones
Insulin
Glucagon
Lowers blood glucose if
the level goes too high.
Excess glucose is
converted to glucagon
and stored in the liver
Raises blood glucose if the
level goes too low.
Glycogen in the liver is
broken to glucose and
released into the blood
Diabetes
There are different types
TYPE 1
• Occurs when the
pancreas doesn’t
function properly and
doesn’t produce
enough insulin to
control blood glucose.
• People with this type of
diabetes need to have
regular injections of
insulin
TYPE 2
• Insulin is produced by
the pancreas but the
receptors in the cells
don’t recognise it as
being there
• People have to control
the amount of sugar
they eat in their diet.
• Insulin injections
wouldn’t work