Regulating the Internal Environment

1
Regulating the Internal Environment

• Homeostasis is the maintenance of the
• bodys multicellular environment with the
• bodys external environment or any changes
• in activity caused.
• The bodies homeostatic response controls water
• concentration in the blood, body core
  temperature,
• blood glucose levels and heart rate by a process
• called negative feedback control.

2
Receptors and Effectors

• Receptors
• Any change to the environment will be detected by
  receptors found in the sensory organs and glands

• Effectors
• The receptor sends a message to the effector
  which alters the bodies response and returns it
  back to normal. Gland and muscular contraction,
  hormone and enzyme production are all effector
  responses.

3
Negative Feedback Control (Fig. 24.1)
4
Control of Heart Rate

• Although the pacemaker initiates heartbeats,
• the rate of heart beating is not fixed and can
• be altered as a result of nervous or
• hormonal activity.
• The autonomic nervous system regulates the
• heart, blood vessels, lungs, alimentary canal and
• sweat glands. This is when the body work
• automatically without the individual having
• to think about making the body do certain jobs.

5
Autonomic Nervous System (ANS)
6

• Medulla of Brain
• Cardio Accelerator Cardio Inhibitor
• Centre
  Centre
• Sympathetic
  Parasympathetic
• cardiac nerves
  cardiac nerves
• Antagonistic response
• Increase in
  Decrease in
• nerve impulses
  nerve impulses
• Increase in heart rate
  Decrease in heart rate

7
Hormonal Control of Heart Rate

• Adrenaline
• Adrenaline is produced in
• the adrenal glands which
• are situated above the
• kidneys. The sympathetic
• nervous system in a
• situation which would
• required adrenaline e.g.
• fight of flight situation, stimulates
• the adrenal glands to release
• adrenaline into the blood system.
• When it reaches the pacemaker it
• increases the heart rate

8
Exercise and Heart Rate

• When we exercise the muscle cells which
• are working are at a higher metabolic rate
• and therefore require a higher levels of
• oxygen and glucose. As a consequence
• they also produce higher levels of carbon
• dioxide. This all needs to be balanced.

9
Distribution of Blood During Exercise

• During exercise the heart rate (pulse) increases,
  the volume of blood
• (stoke volume) pumped through the heart in each
  contraction increases
• cardiac output heart rate X stoke volume
• This increase in heart rate and stoke volume
  increases the rate of
• oxygen delivery to working cells and tissues. Not
  all organs require an
• increase in blood during exercise, only the ones
  which are doing the
• extra work
• Increase in blood flow to tissue during exercise
  would be in the heart
• cardiac muscle, skeletal muscle and the skin
  where excess heat is lost.
• To help with this increase arteries and
  arterioles vasodilate to allow
• A larger volume of blood to pass through at a
  faster rate
• Decrease in blood flow to tissue during exercise
  would be in the kidneys,
• stomach, intestines etc.. The function of the
  kidneys to purify blood and the
• function of the intestine to digest and absorb
  nutrients are processes that can
• wait until exercise is complete. This decrease in
  blood is as a result of
• vasoconstriction of the arteries and arterioles
  carrying blood to these organs.

10
Control of Blood Sugar Levels

• Glucose is essential to
• all living cells as energy
• is released from
• Glucose. The liver
• stores excess glucose
• as glycogen so when it
• is needed there is a
• reserve.

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The Pancreas and Sugar Levels

• Cells in the pancreas called the
• Islets of Langerhans produce
• two hormones insulin and
• glucagon which help control blood
• glucose levels. These levels are controlled
  through negative feedback mechanisms.
• Insulin
• Glucose Glycogen
• Stored in liver
• Glucagon
• Glycogen Glucose

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Diabetes

• Diabetes mellitus is a disorder in
• people and animals who do not
• have or have less functional
• insulin secreting cells in the
• pancreas. As a result of having
• little or no insulin, their blood
• glucose levels increase and are
• not stored in the liver. This can be
• detected in their urine as there is
• so much glucose in the blood that
• it is not reabsorbed but excreted
• in the urine. This used to be a fatal
• disease but with controlled
• administration of insulin by injection
• daily, their glucose levels can be
• maintained.

13
Control of Body Temperature

• The hypothalamus is the
• bodies temperature
• monitoring centre. Heat and
• cold thermoreceptors in the
• skin convey information to
• the hypothalamus. A body
• core temperature from the
• blood and body shell
• temperature form the skin
• triggers a response to
• return the temperature back
• to normal .

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Hypothalamus

• Hypothalamus
• Receiving
• Information
• Core Blood
  
  Skin
• Temperature
  
  Thermoreceptors
• Sweat Glands Skin Arterioles Hair Erector
  Muscles Skeletal Muscles
• Sweating Vasodilatation
  Goose bumps Shivering
• 
  Vasoconstriction

15
Temperature Control in Infants

• Brown Fat
• Babies have a relatively large
• surface area to volume ratio and
• therefore loose heat more rapidly
• than an adult. When a baby is
• born its thermoregulation mechanisms are not
  fully
• developed. When it gets cold it
• involuntarily responds by
• vasoconstriction and brown fat
• generates heat as it is supplied
• with blood vessels.

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Hypothermia

• Hypothermia is when
• someone's body
• temperature is below
• what is considered a
• normal level.
• Preterm babies, infants
• and the elderly are at
• risk.