Living in the environment:
regulation and control
Heat Input
Processes
Heat
Generation
Heat Output
Homeostasis:
the maintenance of relatively stable conditions in the
internal environment of the body despite variations
in the external environment.
Factors such as:
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blood pressure,
body temperature,
respiration rate,
blood glucose levels
pH
Ions
O2 and CO2 levels
Nutritional needs
H2O levels
• are maintained within a range of normal values
around a set point despite constantly changing
external conditions.
• Homeostasis requires the body being able to :
– detect external changes
– Implement internal changes to compensate
The Stimulus - Response Model
The Stimulus - Response Model
Heat
Cools
The Stimulus Response Model
How can the body control the response?
1. Disrupt the signal transduction pathway
2. Removal of the original stimulus
3. Responding in a way that alters the original signal. Feedback
Negative feedback mechanisms
Negative Feedback
Negative Feedback Mechanism
Positive feedback
• Works by adding to the stimulus and increasing
the effect of it.
Positive feedback
Mechanisms enabling Homeostasis
Negative feedback
model
Modes of Transmission
Hormonal system
Nervous system
• Slow ( 30-178cm/sec)
• Act by binding to
specific receptors on
target cells after
travelling through the
blood stream.
• Can be more long term
effect
• Fast ( 1-120m/sec)
• Act by sending electrical
impulses along neuron
cells.
• Short term effect.
The nervous system is a rapid response to stimuli. It is a
more direct communication pathway than hormones .
• There are 2 main parts to the Nervous System:
– The peripheral nervous system
– The central nervous system
Nerve Structure
The nervous system is made up of neuron cells that send an
electrical impulse along from one neuron to the next.
Action Potentials
Basic types of neurons
receptor
effector
The Nerve impulse
Nerve impulse s are an electrical signal that travels along an axon. There is an
electrical difference between the inside of the axon and its surroundings,.
When the nerve is activated, there is a sudden change in the voltage across the wall of
the axon, caused by the movement of ions in and out of the neuron. This triggers a
wave of electrical activity that passes from the cell body along the length of the axon
to the synapse.
The synapse
The Synapse
Neurotransmitters
There are
hundreds of
different types of
neurotransmitters,
each of which
control something
different.
This makes the
nervous system
controllable,
meaning some
neurotransmitter
initiate a response
while others block
a response.
Receptors in the Skin
Types of sensory receptors
CNS
• Many responses are a reflex; not under conscious
control.
• Explain somatic nerves,
autonomic nerves,
parasympathetic and
sympathetic.
Hormones are
signalling
molecules or
chemical
messengers that
control many
functions in the
bodies of
organisms.
eg temperature, blood
glucose levels, calcium
uptake and many many
more are controlled by
hormones.
Hormones
Hormones at work.
Scary
• Cells that
produce
hormones and
are clustered
into organs.
When the homeostatic control of Blood sugar is
disrupted: Diabetes
• Type 1 Diabetes
• Type 2 Diabetes
The pituitary gland secretes
hormones regulating homeostasis,
including tropic hormones that
stimulate other endocrine glands. It is
functionally connected to the
hypothalamus by the median
eminence via a small tube called the
Pituitary Stalk. It is considered to be
the "master gland".
Cushing's disease-Pituitary Gland
Thermoregulation animation
countercurrent heat exchange
When food is scare and the temperature
is low. Some animals can’t maintain a
stable internal temperature. So instead
they hibernate! (Below: Dormice)
A ind of dormancy shown by insects,
where they pause a part of their
lifecycle. (Flies in winter??)
Ways that water can be lost
•
•
•
•
Panting in dogs, dingos & wolves
Sweating
Urine
Faeces
Ways to save or increase water supply
• Thirst response- experienced as the
concentration of water in the blood is
lowered
• Waterproof barriers like; hair,
feathers, scales and skin protect
against evaporative water loss.
• Reabsorption of water from the large
intestine.
• Increase in concentration of urine
by increasing reabsorption of water in
Kidneys.
• Storage of water.
– (Desert frogs store water in a cocoon,
– Camel’s store fat in their hump and
metabolise the fat to gain water
Saltwater
• Marine saltwater animals tend
to have body fluids that are
HYPOTONIC to their
surroundings. So they lose
water via osmosis to their
surroundings.
• To gain more water they drink
salt water and must spend a
lot of energy removing salt
from their body.
Freshwater
• Freshwater animals have lots
of water in their surroundings
but have body fluids that are
HYPERTONIC to their
surroundings. So they can
gain too much water from
their surroundings, causing
their cells to burst.
External : Hi H2O
Internal : LO H2O
LO Salts
Hi Salts
External : LO H2O
Hi Salts
Internal : Hi H2O
LO Salts