Science S2 Theory Exam

What is the endocrine system made up of?

A collection of glands which produce and secrete chemicals directly into the bloodstream.

What does the endocrine system play a role in doing?

It plays a role in regulating mood, growth, development, tissue function, metabolism, sexual function and reproductive processes.

Is the endocrine system in charge of slow or fast responses?

Slow.

How does the endocrine system communicate information?

Through the use of chemical molecules called hormones which are transported through the bloodstream.

What is a gland?

A group of cells that produce and secrete (release) chemicals

Where are exocrine glands secreted?

Through ducts.

Where are endocrine glands secreted?

Straight into the bloodstream.

Major glands of the endocrine system

Pituitary, Adrenal glands, hypothalamus, thyroid, parathyroids, pineal body, pancreas, reproductive glands (testes and ovaries)

What are hormones?

Chemicals that are produced and secreted from endocrine glands into the bloodstream where they can be transported around the body.

Why are hormones sometimes called chemical messengers?

They can bind to specific cells and command them to do certain things.

What do hormones do?

They are used to communicate between organs and tissues so that certain bodily functions can be controlled, such as digestion, metabolism, respiration, excretion, growth, development, reproduction and mood.

Adrenaline?

The hormone that prepares your body to deal with stressful situations, such as intense exercise or fright.

Oestrogen and testosterone?

Hormones that help your body develop properly as you mature.

Why do responses in the endocrine system occur slowly?

Because it takes time to produce hormones, and for these hormones to travel where they need to be.

Why do endocrine responses last a long time?

The response will continue so long as hormones are in the area, and it takes time to destroy or remove them.

How do hormones know which cell to target?

Each hormone is designed to target and affect specific cells. Only particular cells will display a receptor that recognises a specific type of hormone - hormones are receptor-specific.

Hypothalamus?

A collection of specialised cells located in the lower central part of the brain. It acts like a bridge between the nervous system and the endocrine system.

What does the hypothalamus do?

It can receive and send out commands through the nervous system, and also produce hormones that interact with the endocrine system. Main function in the endocrine system is to tell the pituitary gland (located underneath) to start or stop producing hormones.

What type of things does the hypothalamus control?

Controls things such as body temperature, thirst, hunger, mood and sexual development.

Where is the pituitary gland?

At the base of the brain just beneath the hypothalamus.

Why is the pituitary gland referred to as the ‘master gland’?

Because it controls many other endocrine glands. It does this by producing hormones which “tell” those glands to release their own hormones.

What do hormones released by the pituitary gland do?

They control growth of bone and tissue, water balance (to make sure you body has enough water), and reproduction related processes.

Where is the pineal gland located and what does it look like?

It is located near the centre of the brain and is small and pine cone-shaped.

What hormone does the pineal gland produce?

Produces the hormone melatonin, which is responsible for making you feel sleepy at night when it is dark and awake during the day when there is light.

When is melatonin produced?

Melatonin is only produced when there is low light, which is why you sometimes feel alert at night if you are exposed to bright light.

Where is the thyroid gland located and what does it look like?

It is a butterfly-shaped gland found at the bottom of the throat.

What does the thyroid do?

It produces hormones which are essential for your body to be able to grow normally, and in the development of your brain and nervous system. Also makes hormones important for metabolism.

Where is the parathyroid gland located and what is it made up of?

Made up of four tiny masses of tissue that are found behind the thyroid, each about the size of a grain of rice.

What does the parathyroid gland do?

Responsible for maintaining calcium levels in the body, such as in the bones and the blood. Is connected to the nervous system as nerves in the nervous system require calcium to transmit electrical impulses.

Pancreas?

A large gland located behind the stomach. Both an exocrine and an endocrine gland.

What does the pancreas do?

Produces hormones through the exocrine part of the gland to make sure you have the right amount of sugar in your bloodstream. Can produce digestive enzymes that break down the food you eat through the exocrine glands.

Where are the adrenal glands located and what are they made up of?

The adrenal glands are made up of triangular-shaped glands which sit on top of each kidney.

What do the adrenal glands do?

• The adrenal glands are made up of triangular-shaped glands which sit on top of each kidney.

• The main function of the adrenal glands is to regulate the body's metabolism and to maintain the balance of salt and water in the body which is important for maintaining your blood pressure.

• The adrenal glands also make the hormone adrenaline which is produced in response to stress, fright or attack.

Reproductive glands?

• Reproductive glands are the testes and the ovaries

• Produce sex hormones during puberty

• Testes produce testosterone

• Ovaries produce oestrogen and progesterone

What are hormones?

Chemicals that are produced and secreted from endocrine glands into the bloodstream to send a message to another part of the body.

What two types of communication are hormones used for?

• Communication between two endocrine glands - when one gland releases a hormone which causes another gland to start or stop making hormones.

• Communication between an endocrine gland and target organ - this is when a gland releases a hormone that results in an effect somewhere else in the body (not a gland). For example, the release of the hormone insulin causes cells to take up glucose from the blood.

What is a feedback mechanism?

Prevents too much hormone from being secreted - When a certain amount of hormone has been reached in the bloodstream, this is sensed and information is sent back to the gland so that it stops producing and secreting that hormone.

Adrenaline?

produced by the adrenal glands and released into the bloodstream where it results in a number of responses. This is the hormone that prepares your body to deal with stressful situations, such as intense exercise, fright or dangerous situations.

Fight or flight response?

• Adrenaline triggers the 'fight or flight response' (or the sympathetic nervous system) to be activated.

• This response prepares the body to respond to stress and 'fight' or run away from the threat.

• Responses can include an increased heart rate and blood pressure, sweating, and dilation (expansion) of air passages to allow more oxygen to enter the body and reach the muscles.

Growth hormone?

• produced and secreted by the pituitary gland.

• Responsible for controlling the body's growth

• Helps you grow taller, stimulates the growth of all the tissues in the body, like muscles and bone

• Also involved in controlling the body's metabolism

oxytocin?

• produced by the hypothalamus and secreted by the pituitary gland in the brain.

• This hormone has an important role in women during childbirth. It causes the muscles in the uterus to contract during childbirth so that the baby can be pushed out of the birth canal.

• During childbirth oxytocin is controlled by a positive feedback mechanism. This means that the release stimulates more to be released. This is important to ensure that the muscles in the uterus continue to contract until the baby is born

antidiurectic hormone (ADH)

• made by the hypothalamus in the brain and secreted and stored by the pituitary gland.

• released from the pituitary gland into the bloodstream when there is a low blood pressure or not enough water in the blood.

• It tells your kidneys to conserve water by getting the kidneys to reduce the amount of water that is passed out as urine, and taking the water back into the bloodstream. This will increase the blood pressure, returning it to normal.

Melatonin

• mainly produced by the pineal gland in the brain.

• Light is an important factor that controls the production and secretion of it When there is a lot of light, such as during the day, production of the hormone is generally inhibited.

• This means that levels are the highest during the night when it is dark.

• This hormone generally helps us to sleep better at night and regulates our sleep and waking cycles so that we feel sleepy during the night and alert during the day.

What too hormones are produced and secreted by the pancreas?

Insulin and glucagon

What do insulin and glucagon do?

• Both hormones are quired to keep the levels of blood glucose in the narrow range that is required by your body.

• Insulin and glucagon are produced by the 'endocrine' cells in the pancreas, called islet cells.

• Insulin is secreted by beta cells (a type of islet cell). This cells also detect whether there is an increase in blood glucose.

• Glucagon is produced by alpha cells (another type of islet cell). These cells detect whether there is a decrease in blood glucose.

• Insulin is released from the pancreas to lower blood sugar level after a meal.

• When you eat a meal, your blood sugar will increase.

• As a result, your pancreas releases insulin to help lower the blood sugar back to normal levels.

• Insulin acts by binding to cells which allows the  cells to then take up the glucose from the bloodstream, resulting in normal blood sugar levels.

• Between meals and during exercise, the blood glucose levels can become low.

• The low blood glucose levels are detected by the cells in the pancreas, which then secretes the hormone glucagon to raise the blood glucose levels back to normal.

• Glucagon raises blood glucose levels by causing the breakdown of glycogen to glucose in liver cells. This process is called glycogenolysis.

How are normal blood glucose levels maintained?

Through a negative feedback loop.

Blood glucose levels negative feedback loop?

• After eating a meal, blood glucose levels increase. This is the stimulus.

• The receptors which detect this increase in blood glucose are the beta cells in the pancreas.

• A decrease in blood glucose levels is also regulated by a negative feedback loop.

• When blood glucose levels decrease between meals or during exercise, this stimulus is sensed by the alpha cells of the pancreas.

• As a response to this stimulus, alpha cells in the pancreas secrete glucagon.

• Glucagon stimulates the breakdown of glycogen in the liver into glucose which is then secreted out into the bloodstream

• As a result, blood glucose levels return to normal and the pancreas stops producing glucagon.

• In response to this, the pancreas releases insulin. Insulin signals for cells such as adipose (fat), liver and skeletal muscle cells to take in glucose from the blood stream.

• As a result, blood glucose levels then fall back to normal range. The normal blood glucose levels are detected by the pancreas which then stops producing insulin.

What is diabetes?

a disease where the pancreas can no longer make insulin or your body cannot use the insulin produced by the pancreas.

What is a feedback loop?

a cycle that helps the body make constant adjustments to stay balanced.

What is a variable?

the part of the internal environment that the body controls, e.g., temperature or blood oxygen levels.

set point?

 the ideal value for a variable

negative feedback loop?

a response that reverses a change (stimulus) and brings internal conditions back to within normal ranges.

positive feedback loop example?

Example: During childbirth a woman has contractions (stimulus) which trigger the release of hormones that cause more contractions that are stronger and faster. Every time the body responds it causes the stimulus to increase until the job is done - the baby is born.

 

positive feedback loop?

the response increases the change (stimulus) until the job is done - amplification.

As positive feedback loops increase the change (stimulus), the move the body further away from homeostasis.

homeostasis

the process or system that your body uses to keep your internal environment stable when  external conditions change.

negative feedback loop example

Example: When you are too hot (stimulus) you sweat, which cools you down (response). Eventually the original stimulus decreases until you are back at a normal temperature and you stop sweating.

Stimulus response model?

Stimulus > receptor > command centre > effector > response

Wave?

a disturbance that carries energy through matter or space without transferring matter.

trough?

the point at minimum height of a transverse wave

compression

 the place where particles are closest in a longitudinal wave

oscillation

movement back and forth in a regular rhythm. An example is a pendulum on a clock or particles as a wave passes.

crest

the point at maximum height of a transverse wave.

longitudinal wave

a wave where the oscillation of particles is back and forth in the same direction as the wave e.g. sound waves

frequency

number of waves per second, measured in  Hertz (Hz), symbol f, 1 hertz equivalent to 1 wave per second. --> wave that occurs 10 times per second has a frequency of 10 hz.

transverse wave

a wave where the oscillation is at right angles to the wave direction e.g. light waves

rarefaction

the place where particles are most spaced out in a longitudinal wave.

wavelength

the distance between two points on a wave that represent one full cycle, measured in metre. - symbolised by the greek letter lambda λ --> can be measured anywhere on the wave as long as one complete cycle is represented.

velocity

how far and which direction a wave travels per unit time, measured in m/s - we use velocity to describe wave speed.

amplitude

 the distance from the highest (or lowest) point of a wave measured from the centre position. In metres

• Shows how strong or intense the wave is - higher amplitude means more energy!

• Pebble dropped in pond - bigger the waves or ripple, more amplitude!

wave equation?

v = λf

What does frequency determine in a light wave?

The colour of the light.

What does amplitude determine in a light wave?

Brightness - higher amplitude, brighter light.

What does frequency determine in a sound wave?

Pitch

What does amplitude determine in a sound wave?

Volume

What is an oscilloscope?

a device that records sound waves and displays them as simplified waves for analysis

• Takes a sound signal and shows it as a wave, so we can measure how loud or high-pitched the sound is. Sound waves are longitudinal waves, but oscilloscopes convert them into transverse waves so we can easily analyse them on a screen.

sound wave?

vibrations that pass through the molecules of a medium

Eardrum?

thin membrane that vibrates when sound waves hit it, helping pass sound to the inner ear.

Ear canal?

a tube that carries sound waves to the eardrum.

Pinna?

channels sound waves into the ear canal.

ossicles?

three tiny bones in the middle ear named the hammer, anvil and stirrup (scientific names malleus, incus and stapes) that amplify the vibrations from the eardrum.

semicircular canals?

 fluid-filled structures in the inner ear that help with balance. They detect changes in head movement and send signals to the brain.

cochlea?

a spiral shaped part of the inner ear filled with fluid, that converts sound vibrations into electrical signals.

auditory nerve?

transmits electrical signals to the brain.

Three main sections of the ear

Outer, middle and inner ear

Process of hearing

• In the outer ear, sound waves are collected by the pinna and funnelled through the ear canal. After this, in the middle ear, the sound waves reach the eardrum, which vibrates in response to these sound waves. The wave is then amplified by the ossicles, making them strong enough to pass to the cochlea. 1This signal is then sent to the inner ear, which meets the cochlea before travelling through the auditory nerve to the brain. The cochlea is filled with fluid, and as the vibrations travel through it, they cause the fluid to move. Inside the cochlea are tiny hair cells, a type of sensory receptor cell that converts the mechanical sound waves into electrical signals. The hair cells bend in response to the fluid vibrating. This bending opens tiny channels that allow ions (charged atom) to flow into the cells, creating an electrical signal. This signal is then sent through the auditory nerve to the brain. Our brain now has all the information from the sound waves as electrical signals, allowing it to understand and process.

• Once the electrical signals reach the brain, it interprets them as sound. The brain breaks down all the components of a sound: pitch, rhythm and tone.

Workings of the cochlea

• Inside the inner ear, alongside the cochlea, are structures called the semicircular canals. These canals are filled with fluid and lined with tiny hair cells. When you move your head, the fluid in these canals shifts, causing the hair cells to bend. The bending sends signals to your brain about your head's position and movement, helping you stay balanced.

cochlear implant

An electronic device that can restore sound perception in people with certain types of severe hearing loss by picking up sound from the environment, converting that sound into electrical impulses, and transmitting those impulses directly to the auditory nerve.

Cochlear implant process

• Cochlear implants consist of both external and internal components. The external component typically sits behind the ear and picks up sound through a microphone; when sound is detected, a sound processor converts the auditory information into a radio frequency signal. The signal is transmitted to a receiver implanted under the skin behind the ear. The receiver decodes the signal, then converts it into electrical currents, which are sent along wires that have been surgically inserted into the cochlea. The wires stimulate the auditory nerve (a job typically reserved for the damaged cochlear cells), and stimulation of the nerve causes auditory information to be sent to the brain to create sound perception.

Ultrasound

sound waves with frequencies above 20, 000 Hz (too high to hear)

transducer

a handheld device that sends and receives ultrasound waves

ultrasound imaging

a medical technique that uses ultrasound to create images of the inside of the body. Doctors can examine internal structures without the use of harmful radiation.

Light?

electromagnetic radiation that acts like both a wave and a particle

visible light

a part of the broader electromagnetic radiation (EMR) spectrum, specifically occupying a narrow band of wavelengths that are visible to the human eye.

Rods

brightness

cones

colour

Reflection

• Waves - including sound and light - can be reflected at the boundary between two different materials

Law of Reflection

angle of incidence = angle of reflection

Diffuse reflection

happens if a surface is rough, may cause distorted image of the object

Refraction

the change in direction of a wave at a boundary/the bending of light as it moves through different mediums