B5 - Homeostasis and response

Title B5 - Homeostasis and response Description

What is homeostasis?

The regulation of the conditions inside the body to maintain a stable internal environment

Why is homeostasis important?

It maintains optimal conditions for enzyme action and all cell functions

In the human body, what does homeostasis control?

Blood glucose concentration, body temperature, and water levels

What types of responses can automatic control systems use?

Nervous responses or chemical responses

What are three parts found in all control systems?

Receptors, co-ordination centres, and effectors

What is a receptor?

A cell that detects a stimuli (changes in the environment)

What is a coordination centre?

A centre such as the brain or spinal cord that receives and processes information from receptors

What is an effector?

A muscle or gland that carries out the response to restore optimum levels

What does the nervous system enable humans to do?

React to their surroundings and coordinate their behaviour

What is a neurone?

A cell that carries information as electrical impulses

How does information travel in the nervous system?

From receptors along neurones as electrical impulses to the CNS

What does CNS stand for?

Central nervous system – the brain and spinal cord

What does the CNS do?

It coordinates the response of effectors

What are effectors in the nervous system?

Muscles contracting

The order of the nervous system process

Stimulus → receptor → coordinator → effector → response

What is a reflex action?

An automatic and rapid response that does not involve the conscious part of the brain

Why are reflex actions important?

Because they are automatic and rapid, helping protect the body

What is the function of the sensory neurone?

Carries impulses from the receptor to the CNS

What is the function of the relay neurone?

Connects the sensory neurone to the motor neurone inside the CNS

What is the function of the motor neurone?

Carries impulses from the CNS to an effector

What is a synapse?

The connection between two neurones, and it is where impulses are transferred by chemicals across the gap

What is meant by ‘negative feedback’?

Negative feedback is when a change in condition triggers responses that reverse the change and restore normal levels

What is a hormone?

A chemical released by glands into the blood, carried to a target organ where it produces an effect

Compared to the nervous system , how do hormones act?

Slower but they act for longer

What is the pituitary gland?

A ‘master gland’ in the brain that secretes hormones into the blood in response to body conditions

What monitors and controls blood glucose concentration?

The pancreas

What happens if blood glucose concentration is too high?

The pancreas produces insulin

What does insulin do?

Causes glucose to move from the blood into cells

What happens to excess glucose in liver and muscle cells?

It is converted to glycogen for storage

What is type 1 diabetes?

A disorder where the pancreas fails to produce sufficient insulin

How is it treated?

Insulin injections

What is type 2 diabetes?

When body cells no longer respond to the insulin produced by the pancreas

What are comment treatments for type 2 diabetes?

A healthy, balanced diet and regular exercise

What is a risk factor for type 2 diabetes?

Obesity

What happens if blood glucose is too low?

The pancreas produces glucagon

What does glucagon do?

Causes glycogen to be converted into glucose and released into the blood

What do reproductive hormones do during puberty?

Cause secondary sex characteristics to develop

What is the main female reproductive hormone, and where is it produced?

Oestrogen, and it is produced in the ovary

What is the main male reproductive hormone and where is it produced?

Testosterone, and it is produced in the testes

What does testosterone do?

Stimulates sperm production

What does FSH do?

FSH stimulates the ovary to produce oestrogen and causes the maturation of the egg

Where is FSH produced?

The pituitary gland

What does oestrogen do?

Builds and thickens the uterus lining. High levels inhibits the release of FSH from pituitary to make LH

Where is oestrogen produced?

In the ovaries

What does LH do?

Stimulates the release of an egg (ovulation), and it also stimulates the profuction of progesterone

Where is LH produced?

Pituitary gland

What does progesterone do?

Maintains the lining of the womb and also prepares the uterus for pregnancy

Where is progesterone produced?

It is produced in the ovaries

What happens during days 1 - 5 in the menstrual cycle?

The lining of the uterus breaks down as oestrogen and progesterone levels are low

What happens during days 5 - 13?

• The pituitary gland releases FSH, which causes the egg to mature
  

• The ovary releases oestrogen, which thickens the lining, inhibits FSH and stimulates the release of LH

What happens during ovulation (around day 14)?

LH causes the egg to be releases from the ovary, and it enters the oviduct

What happens during days 15-28?

• Progesterone is released, which maintains the thick uterus lining, and it inhibits FSH and LH
  

• If egg is not fertilised, progesterone levels fall and the uterus lining breaks down → and menstruation starts again

What can fertility be controlled by?

Hormonal and non-hormonal methods of contraception

How do oral contraceptives work?

They contain hormones to inhibit FSH production so no eggs mature

How do the injection/implant methods wor?

Slow release of progesterone to inhibit maturation and release of eggs for months or years

What are barrier methods and what do they do?

Condoms and diaphragms: they prevent sperm reaching an egg

What do IUDs do?

They prevent the implantation of an embryo

What do spermicidal agents do?

Kill or disable sperm

What are surgical methods of contraception?

Cutting the fallopian tubes in a female and the sperm duct in a male

What other ways can you avoid pregnancy?

Abstaining from intercourse when an egg may be in an oviduct or to not have intercourse at all

What is a fertility drug, and what hormones does it contain?

A drug that gives FSH and LH to a woman

What are the pros and cons of taking these fertility drugs?

• A pro is that it helps lots of women to get pregnant
  

• Some cons are that it doesn’t always work and it can be expensive. Also too many eggs could be stimulated, resulting in multiple pregnancies

What does IVF stand for?

In vitro fertilisation

What is the first step of IVF?

Giving the mother FSH and LH to stimulate the maturation of the eggs

What is the second step of IVF?

Eggs are collected from the mother

What is the third step of IVF?

Eggs are fertilised by the sperm from the father in a lab

What is the fourth step of IVF?

The fertilised eggs are then grown into embryos

What is the last step of IVF?

When they become tiny balls of cells, one or two embryos are inserted into the mother’s uterus

Give 3 issues with fertility treatment.

• Can be emotionally and physically stressful
  

• Success rates are not high
  

• Can lead to multiple births

Where is adrenaline produced?

The adrenal glands

When is adrenaline produced?

In times of fear or stress

What does adrenaline do to the body?

It increases the heart rate, and boosts the deliver of oxygen and glucose to the brain and muscles

Where is thyroxine produced?

Thyroid gland

What does thyroxine do?

Regulates the basal metabolic rate and it’s also important for growth and development

How are thyroxine levels controlled?

By negative feedback