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Homeostasis and Response

Homeostasis and Body Temp
Homeostasis is the regulation of the internal
Human core temperature should be kept around 37
conditions of a cell or organism in response to the
degrees celsius, this is the optimum temperature for
internal and external changes
...
The thermoregulatory centre in the brain
because it keeps conditions constant for the enzyme
monitors and controls the core temperature
...
Includes the regulation:
receptors that monitor the temperature of the blood flowing
blood glucose concentration, body temperature and
through the brain and it receives the information (impulses)
water and ion levels
...

involve: response to the nerves and chemical
If the temperature is too low the
responses using hormones
...
Also more
muscles contract and relax quickly
● Coordination centres (such as the brain and
sweat is produced
...

process information from receptors
...
change so the person can do
This type of control is called negative feedback
...
They do not involve the conscious part of the brain
...
Information
from the receptors are passed to the central nervous system The effector is the muscle
initiates a response (muscle
(either the brain or spinal cord)
...

response of effectors, like secreting hormones or muscle
contracting
...

The impulse then pass
along a relay neurone
where in the spinal
cord a decision is
made
...


The skin receptors
detect the heat of the
flame

Candle is the
stimulus

The receptor sends electrical
impulses along the sensory
neurone
...
It is made of billions of
interconnected neurons and has different regions that carry out different functions
...

Cerebrum or cerebral cortex - responsible for consciousness, memory,
intelligence and language
...

Hypothalamus - which coordinates both the autonomic nervous system
and the activity of the pituitary, controlling body temperature, thirst,
hunger, and other homeostatic systems, and involved in sleep and
emotional activity
...

● Electrically stimulating parts of the brain
...

The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult
...

Optic nerve - carries impulses from retina to the brain
...

Iris - controls the size of the pupil (absorbs light) and the amount of light
reaching the retina
...


Accommodation is the process of changing shape of the lense to focus on near or
distant objects
...
These are
corrected with lenses which refract the
light rays so they focus on the retina in
the form of contact lenses or glasses
...


Hormones and Homeostasis
The Endocrine System is made up of glands that secrete hormones directly into the
bloodstream
...
The effects of hormones are slower than the nervous system
...
It secretes several hormones in
response to body conditions
...
Thyroxine produced
by the thyroid gland it increase metabolic rate and controls growth and development
in young animals is controlled by negative feedback
...
If the levels are too high more
insulin is produced which causes the glucose to move into the cells from the blood where in the liver and
muscle cells it is converted into glycogen for storage
...
Type 1 diabetes is when the
pancreas doesn’t produce enough insulin leading to high concentration levels treated with insulin injections
...
There is a obesity risk factor and is treated with a
carbohydrate-control diet and regular exercise
...


Water leaves the body through sweat, exhaling and urine (along with ions and urea)
...
The balance of water and ions is regulated by the kidneys
...
The
digestion of proteins from food results in excess amino acids, these are then converted to ammonia in the liver by a
process called deamination
...

The kidneys produce urine by:
● Filtering the blood
...

● This leaves urea and excess water and ions to for urine
...

The water level is controlled by the ADH hormone
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Sex Hormones
Hormones play many roles in controlling human reproduction
...
Oestrogen from the ovaries in females
...
Testosterone from the
testes and stimulates sperm production
...

Hormone

Secreted by

Function

Follicle stimulating
Hormone (FSH)

Pituitary gland

Causes eggs to mature and stimulates
oestrogen production

Oestrogen

Ovaries

Inhibits FSH release, stimulates LH
and makes lining of uterus grow
...


Progesterone

Empty follicle in
the ovaries

Maintaining the lining of uterus and
inhibits FSH and LH
...

An injection, implant or skin patch of slow release progesterone stopping release of eggs for a no
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Barrier methods like condoms and diaphragms to prevent sperm reaching the egg
...

Spermicidal creams which kill or disable sperm
...

Surgical methods of male and female sterilisation such as tying the fallopian tubes or cutting the sperm ducts
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Increasing fertility
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Doctors may give FSH and LH in a fertility drug if a woman’s level of
FSH is too low to simulate eggs to mature
...

Collecting the eggs from the mother
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This gives a woman a chance to have a baby
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Can lead to multiple births putting the babies and mother at risk
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They respond to
the changes slower than animals and include: roots and shoots
growing away or towards a stimulus, plants flowering at a particular
time and the ripening of fruits
...
These are controlled by auxins
...

More auxins sent down the shaded side
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The shoots grow towards the light
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Gibberellins initiate seed germination and ethene is a gas controls
cell division and ripening of fruit
...
Ethene
is used in the food industry for ripening, storage and
transport
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