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Homeostasis and the Human Endocrine System: A Comprehensive Guide, Summaries of Biology

Biology

A comprehensive overview of homeostasis, the process by which organisms maintain a stable internal environment. It explores key concepts such as the role of receptors, coordination centers, and effectors in maintaining homeostasis. The document also delves into the human endocrine system, highlighting the functions of various glands and hormones, including the pancreas, pituitary gland, thyroid gland, and adrenal glands. It further examines the mechanisms of negative feedback and its role in regulating hormone production. The document concludes with a discussion of diabetes, its types, causes, and treatment.

Typology: Summaries

2024/2025

Uploaded on 01/31/2025

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Homeostasis and Response
Homeostasis- The regulation of internal conditions of a cell or organism to maintain optimum conditions for a
function.
Conditions in the body that are controlled by Homeostasis:
-Water Levels
-Body Temperature
-Blood Glucose Concentration
-Thyroxine Levels
-Ion content
Parts of the control system:
Receptors – Detect a change in the environment.
Coordination centre – Receive and process information from receptors.
Effectors – Bring about a response.
Human Nervous System:
- The nervous system is a system that enables humans to react to their surroundings and coordinate
their behaviour.
- It is made up of the Central Nervous System which includes the brain and the spinal cord and the
Nerves.
Information is passed from:
Stimulus Receptor Coordinator Effectors Gland
Key Terms:
1. Central Nervous System- The brain and spinal cord.
2. Sensory Neurone- Transmit impulses from receptors to relay neurones.
3. Synapse- A gap between neurones.
4. Relay Neurones- Transmit nerve impulses within the CNS.
5. Motor Neurone- Transmit impulses from relay neurones to effectors.
Reflex Action: Automatic, Involuntary, go through the Spinal cord and not the brain so that they are faster.
1. Receptors detect a stimulus and generate an electrical impulse.
2. The impulse travels along the sensory neuron and crosses a synapse.
3. The impulse is processed by a relay neurone and the impulse then travels along a motor
neurone to the effector.
4. The effector brings a response.
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Download Homeostasis and the Human Endocrine System: A Comprehensive Guide and more Summaries Biology in PDF only on Docsity!

Homeostasis and Response

Homeostasis- The regulation of internal conditions of a cell or organism to maintain optimum conditions for a

function.

Conditions in the body that are controlled by Homeostasis:

  • Water Levels
  • Body Temperature
  • Blood Glucose Concentration
  • Thyroxine Levels
  • Ion content

Parts of the control system:

Receptors – Detect a change in the environment. Coordination centre – Receive and process information from receptors. Effectors – Bring about a response.

Human Nervous System:

  • The nervous system is a system that enables humans to react to their surroundings and coordinate their behaviour.
  • It is made up of the Central Nervous System which includes the brain and the spinal cord and the Nerves.

Information is passed from:

Stimulus Receptor Coordinator Effectors Gland

Key Terms:

1. Central Nervous System- The brain and spinal cord.

2. Sensory Neurone- Transmit impulses from receptors to relay neurones.

3. Synapse- A gap between neurones.

4. Relay Neurones- Transmit nerve impulses within the CNS.

5. Motor Neurone- Transmit impulses from relay neurones to effectors.

Reflex Action: Automatic, Involuntary, go through the Spinal cord and not the brain so that they are faster.

1. Receptors detect a stimulus and generate an electrical impulse.

2. The impulse travels along the sensory neuron and crosses a synapse.

3. The impulse is processed by a relay neurone and the impulse then travels along a motor

neuro ne to the effector.

4. The effector brings a response.

Synapse:

How does an electrical impulse travel through the synapse?

  • There is an electric impulse in the pre-synaptic neurone. It triggers the vesicles and they move to the cell membrane of the pre-synaptic neurone. The neurotransmitters from the vesicle empty into the synaptic cleft through exocytosis. The neurotransmitters diffuse through the synaptic cleft and bind to the receptors on the post-synaptic neurone. This triggers an electrical impulse to continue in the post- synaptic neurone. The leftover neurones diffuse back to the pre-synaptic neurone through reuptake. The neurotransmitters enter the neurone and form vesicles.

Human Endocrine System:

  • The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.
  • The blood carries the hormone to the target organ where it produces an effect.
  • The effects are slower compared to the Nervous system which is instant. However, the effects last for longer, unlike the Nervous system.

Gland Hormones Act

Adrenal Adrenaline In an emergency like a fight or flight.

Adrenal Cortisol Controls immunity and metabolism.

Thyroid Thyroxine Controls metabolism.

Testes Testosterone Regulates male reproductive and sexual development.

Ovaries Oestrogen Regulates female reproductive and sexual development.

Pancreas Insulin Controls blood sugar and storage of fat.

Pancreas Glucagon Controls blood sugar.

Pituitary Gland:

  • Known as the ‘Master Gland,’ located in the brain.
  • Secretes several hormones into the blood in response to body conditions.
  • These hormones stimulate other glands causing other glands to release other hormones to bring about an effect.

Negative Feedback:

  • The action taken by the body to return to an optimum level following a stimulus.

Thyroxine:

  • Produced in the thyroid gland.
  • Stimulates the basal metabolic rate.
  • Controls Rate of Respiration.
  • Key role in growth and development.
  • Controlled by negative feedback.

TSH- Thyroid stimulating hormone. Released by the pituitary gland.

Negative Feedback Loop of Thyroxine:

1. Receptors in the brain detect low thyroxine levels (stimulus) in the blood.

2. The pituitary gland releases TSH.

3. TSH stimulates the secretion of thyroxine by the thyroid glands.

4. Thyroxine levels increase.

  • Blood glucose concentration is monitored and controlled in the pancreas. If Blood glucose concentration is too high …
  • The pancreas makes insulin.
  • Insulin causes glucose to move from the blood into the cells.
  • Liver and muscle cells convert glucose into glycogen for storage. If Blood glucose concentration is too low …
  • The pancreas makes glucagon. (Gluca-gone… Shows glucose is gone… easy way to remember).
  • Glucagon causes Glycogen to be converted into Glucose and released into the blood. Glucose: a sugar found in the body. Glycogen : a storage of carbohydrates found in the liver and muscles. Glucagon: Hormone that causes the breakdown of glycogen into glucose. Insulin: Hormone that controls the storage of glycogen in the liver.

Diabetes:

  • Diabetes is a disease where your body cannot control the amount of glucose in the body.
  • Diabetes is a disease where your body’s ability to produce or respond to insulin is impaired.

Type 1 Diabetes:

  • The pancreas is unable to produce enough insulin.
  • Occurs typically in younger people/ children.
  • Genetic- no lifestyle risk factors.
  • Treated with insulin injections.

Type 2 Diabetes:

  • Body cells no longer respond to insulin.
  • Typically, in older people.
  • Obesity is a big risk factor.
  • Carbohydrate-controlled diet and exercise.

Control of Blood Glucose (diabetes):

  • People with either Type 1 or Type 2 diabetes must monitor their glucose levels.
  • People with either Type 1 or Type 2 diabetes will have high uncontrolled glucose levels and

after eating, their blood glucose levels will fall slower than someone who does not have

diabetes.

Differences and similarities between Type 1 and Type 2 Diabetes:

Type 1 Diabetes Type 2 Diabetes

Blood Glucose High uncontrolled blood glucose levels that fall slowly after

eating.

Cause The body does not produce

enough Insulin.

The body does not respond to

Insulin.

Insulin levels in Blood Low High

Treatment Insulin Injection Controlled diet and exercise.

Why must the insulin be given as an injection and cannot be taken as a tablet?

  • Insulin is a protein. If it were taken as a tablet, it would be digested by protease (enzymes) in the stomach. To identify Type 1 Diabetes:
  • Look for a high glucose level.
  • Look for a glucose level that does not fall.
  • Look for low insulin levels. To identify Type 2 Diabetes:
  • Look for a high glucose level.
  • Look for a glucose level that does not fall.
  • Look for high insulin levels.

Puberty:

  • Puberty is the process that occurs during adolescence, resulting in the development of secondary sexual characteristics and the ability to reproduce.
  • In females, a hormone called oestrogen is produced in the ovaries, and its main role during puberty is to stimulate the development of breast tissues and the onset of menstruation.
  • In males, a hormone called testosterone is produced in the testes, and its main role during puberty is to stimulate facial and body hair growth deepening of the voice and sperm production.

Change during Puberty Males Females

Voice deepens ✔️

Body hair grows ✔️

Shoulders broaden ✔️

Hips get wider ✔️

Breasts start to develop ✔️

Facial hair grows ✔️

Genital growth ✔️

Periods start ✔️

Mood Swings ✔️^ ✔️

Acne ✔️^ ✔️

Growth Spurt ✔️ ✔️

Hormones during Reproduction :

  • During puberty reproductive hormones cause secondary sex characteristics to develop.

Contraceptive Hormonal/ non- hormonal What it does Positives Negatives Oral Hormonal Contain hormones to inhibit FSH production so no eggs mature Can reduce some types of cancer Risk of high blood pressure. Injection Hormonal Slow-release progesterone inhibits the maturation and release of eggs for many months. Don’t have to remember to take a pill every day. Side effects. Barrier Method Non- Hormonal Prevent the sperm from reaching the egg. Easy to use. Can tear or rip. Intrauterine device Hormonal Prevent the implantation of an embryo or the release of a hormone. Can remain in position for a long time. Risk of ectopic pregnancy. Spermicidal Agents Non- Hormonal Kill or disable sperm. Can be added to a barrier contraceptive. Can cause allergic reactions. Abstaining Non- Hormonal Not having intercourse when an egg may be in the oviduct. Can be used for religious reasons. If the timing is not accurate, the chances of pregnancy is higher. Surgical Methods Non- Hormonal Sterilisation Effective at preventing pregnancy. Can’t be reversed. Treating Infertility:

  • Hormones can be used to treat infertility.
  • FSH and LH can be used as an infertility drug for a woman. She may then become pregnant in a normal way. IVF ( In Vitro Fertilisation):

1. The mother is given FSH and LH to stimulate to maturation of several eggs.

2. The eggs are collected from the mother and the sperm is collected from the father.

3. The eggs are then fertilised with the father’s sperm in a lab.

4. The fertilised eggs develop into embryos.

5. At the stage when they are tiny balls of cells, one or two embryos are inserted into the

mother’s uterus. Fertility treatments can be used to give a woman the chance to have her baby. However, it can be emotionally and physically stressful. – Success rates are not high. It can lead to multiple births that are a risk to the babies and the mother.