Biology: animal coordination, control and homeostatis


Endocrine system

The endocrine system regulates bodily functions through the release of hormones. e.g growth and development.

The endocrine glands release hormones into the bloodstream-this allows the hormones to travel to their target organs--> a particular organ that a hormone affects as it has the appropriate receptors for that hormone. 

The Nervous system vs Endocrine system:

type of signal- electrical / chemical

transmission of signal- neurones / by bloodstream

effectors- muscles or glands / target cells in particular organs

type of response- muscle contraction or secretion / chemical change 

speed of response- very rapid / slower

duration of response- short (until nerve impulses stop) / long (until hormone is broken down)

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Endocrine glands

Gland     /      Hormone produced    /       Function of hormones

Pituitary      FSH + LH                            control menstrual cycle

Adrenal       adrenaline                           causes fight / flight response to stress/excitement

Thyroid       thyroxine                             regulates metabolic rate (rate of respiration by the cells)

Ovaries      oestrogen+progesterone   develops reproductive organs during menstrual


Testes         testosterone                       male reproductive hormones during puberty

Pancreas    insulin+glucagon                controls amount of glucose in blood 

Endocrine glands are glands that produce and release hormones. Hormones are chemical messengers released by the endocrine glands. They are transported through the blood to target organs.

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Adrenaline affects the heart, liver and blood vessels.

Effects on the liver: liver cells convert glycogen into glucose for respiration and are then released into the blood, this increases blood sugar concentration. More glucose means more energy is released--> preparing for fight or flight response.

Heart: heart muscle cells contract more rapidly (so increases heart rate) and they contract more strongly (this increases the blood pressure). 

Blood vessels: wide blood vessel (vasodilation)--> diameter of vessel leading to muscles widens, which increases blood flow to muscles/// narrow blood vessels (vasoconstriction)--> diameter of vessel leading to other organs narrows which reduces blood flow to those organs and increases blood pressure. 

Quick summary: 

Adrenaline increases heart rate, blood flow, blood pressure and prepares body for fight or flight response by delivering oxygen and glucose to the brain and muscles. Adrenaline IS NOT controlled by negative feedback.

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Metabolic rate= the rate at which chemical reactions occur in the body e.g digestion.

Resting metabolic rate= the rate when the body is at rest

Thyroxine; stimulates the basal metabolic rate, causes heart cells to contract more rapidly and strongly, increases rate of protein and carbohydrate breakdown in cells.

Thyroxine levels are controlled by negative feedback--> increase of thyroxine in blood causes changes that decrease thyroxine levels. 

How is the concentration of thyroxine in the blood controlled by a series of glands?

Thyroxine levels in blood are too high-->inhibits release of TRH from hypothalamus which then inhibits release of TSH from the pituitary gland- this causes less thyroxine to be released so blood thyronixe concentration decreases.

Levels are too low-->stimulates hypothalamus to release TRH and TSH from pituitary- thyroid releases more thyroxine so blood thyroxine levels return to normal. 

Hypothalamus= located in the brain, detects changes in body, contributes to homeostatis.

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Negative feedback in hormonal control

Homeostatis= the maintenance of constant internal conditions in an organism. 

Negative feedback is found in homeostatis. Negative feedback system responds when conditions change from the ideal point and returns conditions back to normal.  

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Regulation of blood glucose

Glucose (a simple sugar) is needed by cells for respiration (the chemical change which uses glucose and oxygen to release energy). 

Insulin is a hormone produced by the pancreas which regulates glucose concentrations in the blood.

When blood sugar rises in the blood, insulin sends a signal to the liver, muscles and other cells to store the excess glucose. Some is stored as body fat and other is stored as glycogen in the liver and muscles.

When blood glucose levels fall too low, it's detected by the pancreas. This causes the pancreas to release the hormone glucagon into the blood stream. This hormone then travels around the body, and binds mainly to cells in the liver. This stimulates those liver cells to break down their stored glycogen into glucose and release it into the blood. 

Too low: there won't be enough glucose for tissue cells to respire.

Blood glucose levels rise after eating because we absorb glucose from the food. 

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Type 1: Pancreas doesn't produce enough insulin- characterised by uncontrolled high blood glucose levels--> controlled by injecting insulin into fatty layer of skin before eating, eating less sugary foods and regular exercise due to increased respiration in the muscles. 

Type 2: Body cells no longer respond to insulin, more common in older people-->controlled by a carbohydrate based diet and an exercise regime. Carbohydrate is digested into glucose, which raises the overall blood glucose level.

There's a correlation between rising levels of body mass in the population and an increase of type 2 diabetes. 

:BMI = mass (kg) / height squared (m)        -- obese= over 30kg/m^2

Waist:hip ratio = waist measurement/hip measurement.  --over 0.85 in women and 1 in men=obese

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The menstrual cycle

The menstrual cycle is a recurring process that usually takes around 28 days. 

The ovaries release; oestrogen, progesterone, FSH and LH. 

Oestrogen=builds up uterus lining / progesterone=maintains the lining of uterus--> the built up lining is ready for a fertilised egg to implant itself and start developing. However if no egg is fertilised (you're not pregnant), both hormone levels drop-->the lining sheds and menstruation (bleeding) occurs. 

1 egg is released from the ovaries every month (around day 14)=ovulation.

follicle stimulating hormone (FSH) causes the maturation of an egg in the ovary

luteinising hormone (LH) stimulates the release of the egg 

Day 1-12 - oestrogen gradually increases and peaks approx on D-12-> Progesterone, stays approx at the same level and begins to increase from around day 12. // Oestrogen drops during day 13/14, and progesterone continues to increase until about day 21, when it slowly begins to decrease again. Oestrogen mirrors this shape and also has a second lower peak at about D- 21.

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The menstrual cycle (2)

FSH released from pituitary gland--> FSH causes egg follicle to grow and mature--> egg follicle releases oestrogen so uterus lining thickens--> high levels of oestrogen stimulates release of LH from pituitary gland--> LH causes ovulation--> ruptured follicle becomes a corpus luteum--> corpus luteum releases progesterone--> progesterone inhibits release of FSH and LH--> no fertilisation; breakds down and menstruation occurs. 

Why are some couples unable to have children?

Assisted Reproductive Technology= uses hormones to increase the chance of pregnancy e.g Clomifene therapy (stimulates ovulation) and IVF. 

In Vito Fertilisation-->1. egg follicle maturation stimulated by hormones 2. egg cells released+ sperm cells taken from a man 3. eggs+ sperm combined to allow fertilisation 4. 1 or 2 healthy embryos placed in uterus.

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Controlling fertility

Non- hormonal methods; physical barriers e.g condoms/ diaphragms, spermicidal agents which kill or disable sperm, abstaining from intercourse. 

Pros; don't affect other health conditions, fewer side effects, protects against STI's

Cons; can be uncomfortable, some can't be used during menstruation, physical barriers could rip.

Hormonal methods; oral contreceptive (the pill) contains oestrogen and progesterone which inhibit FSH. Eventually egg development and release will stop.

Pros; 99% effective if taken effectively, can reduce risks of certain cancers

Cons; possible side effects such as changes in weight, mood and blood pressure due to high levels of oestrogen. Modern pills contain much less oestrogen.

Contraceptive injections, implants or skin patches contain slow release progesterone to inhibit the maturation and release of eggs.

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The Kidneys (1)

Main job of the kidneys: 

Filter the blood, remove all waste we don't want (urea), regulate levels of ions and water.

Urea--> made in the liver during deamination.(this is where excess amino acids- molecules that combine to form proteins- are converted to fats and carbs for storage).

Ions--> get them from diet, too high or too low can damage cells, we lose some naturally through sweating, 

Water--> attained from food and drink, lose water when we sweat and from lungs when we breathe, most water lost from the kidneys through urine.

Water regulation:

our cells will lose/gain water through osmosis

too much water- the water will diffuse into our cells- could swell and burst

too little- cells lose water and shrink.

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The Kidneys (2)

Urinary System: Facts, Functions & Diseases | Live Science

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