Science Focus 3-7

Endocrine system?

A network of glands that produces hormones, known as chemical messengers, that travel through the bloodstream to regulate bodily functions and maintain homeostasis.

What are hormones?

Hormones are chemical messengers produced by endocrine glands, they are signals that help influence and regulate bodily processes. Receptor-specific.

What is an endocrine gland?

an organ in your body that produces and releases hormones directly into bloodstream.

Why do hormones only affect certain cells and not all cells in the body?

Hormones only affect cells that have specific receptors for them, the hormone can bind to receptor if it’s the target cell.

Why do responses of the endocrine system occur slowly?

It takes time for hormones to be produced and to travel where they need to go.

Name the 9 endocrine glands?

Hypothalamus, Pituitary, Thyroid, Adrenal, Parathyroid, Reproductive, Pineal, Pancreas, Thymus.

Hypothalamus?

Maintains homeostasis, regulates body temperature, heart rate, blood pressure, and control centre for both nervous and endocrine systems. Signals pituitary gland to release or stop hormones. Base of Brain.

Pituitary gland?

Master gland. Anterior lobe releases hormone for growth and development. Posterior lobe controls water balance and blood pressure through ADH . Below hypothalamus.

Pineal gland?

Produces melatonin hormone, regulating sleep cycles. Location: brain.

Thyroid gland?

Produces calcitonin, triiodothyronine, thyroxine; determines how your body uses energy, and metabolism. Location: base of neck

Parathyroid gland?

Releases PTH hormone for calcium absorption in bones and blood. Located in neck, below thyroid.

Thymus gland?

Controls production of white blood cells and immune function. located behind sternum.

What do the reproductive glands do?

Ovaries & Testicles. Produces sex hormone (oestrogen, progesterone, testosterone) for reproductive growth and development.

Pancreas gland?

Produces insulin and glucagon to regulate blood glucose & digesting nutrients. Glucagon: signals liver to release stored glucose. Insulin: lowers blood sugar by removing it from bloodstream into cells for energy or storage. Endocrine & exocrine. Located behind stomach, under liver.

Adrenal gland?

Produces adrenaline, aldosterone and cortisol to react to stress for fight or flight responses and salt and water balance.

What is the ‘master’ gland?

The pituitary gland, it’s secretion of hormones determine the distribution of hormones by other glands.

Why is adrenaline referred to the fight or flight hormone?

Triggers a rapid stress response, preparing the body for immediate action against a threat or danger. It increases heart rate, vasodilation and sharpense sense by releasing glucose for energy allowing quick decisions. The sympathetic nervous system.

Difference between reflexes and adrenaline?

• reflexes = immediate reactions stimulates by instant, electrical and nerve-based.

• Adrenaline = provides whole-body readiness by giving your body more energy and awareness.

Endocrine?

Inside, secreted through bloodstream.

Exocrine?

outside, secreted through ducts.

Adrenaline?

Triggers sympathetic nervous system, prepares body to respond to stress (+ heart rate, blood pressure, sweating, dilation of air passages.)

Oestrogen

Female sex hormone: growth of breasts, pubic hair, menstrual cycles.

Testosterone?

Male sex hormone: facial/pubic/body hair, voice pitch & strength

Growth hormone

controls body growth and metabolism

Oxytocin

Muscle contraction in childbirth; positive feedback.

Anti-diuretic hormone

Conserves water by reducing urine production

Melatonin

Produced by pineal glands, light controls production and secretion of melatonin. Highest levels in dark.

Cortisol

Helps manage stress by increasing blood glucose when stressor is present, controls blood pressure, support metabolism.

Characteristics of Nervous and Endocrine systems?

Nervous:

• Transmission: electrical impulses through neurons, fast, short-term responses, responds in muscles or glands.

Endocrine

• Transmission: chemical through bloodstream, slow, long-term, organs.

What is homeostasis?

The body’s ability to maintain a stable internal environment despite external changes.

Negative feedback?

A process where a change in a variable triggers response to restore to its set point.

Positive Feedback?

Amplifies stimulus to encourage change.

Variable?

A body condition being controlled.

Set point?

Ideal value of a variable

Reference range

The normal/healthy range of a variable.

Main systems involved in maintaining homeostasis?

Nervous and endocrine systems.

Can the body change a variable’s set point?

Yes, to prioritise one variable over another. (e.g., increasing heart rate during exercise.)

Consequences of changing set point?

Yes at times it can be beneficial (raising body temp to fight infection) however if maintained long-term it can be harmful leading to high blood pressure, heart disease.

Process of detecting and imbalance in the body?

1. Hypothalamus monitors internal conditions.

2. Detects imbalance, signals pituitary via hormones or nerves.

3. Pituitary releases hormones directing other glands.

4. Target glands release hormones.

5. Hormones travel via blood to target cells.

6. Once balance restored, signals reduce hormone production.

7. Negative feedback prevents overproduction, maintaining homeostasis.

What is a wave?

Disturbance that transfers energy from one point to another.

Examples of mechanical waves

Sound waves, ocean waves, seismic waves, slinky waves.

Examples of electromagentic waves

Radio waves, microwaves, visible light, UV light, x-rays

What a transverse wave?

Oscillations of the medium move perpendicular to the direction of energy transfer. ripples, microwaves, radio waves.

What’s a longitudinal wave?

Oscillations of medium move parallel to direction of wave’s travel. Earthquakes, sound waves, vibration of spring.

Wavelength?

Distance between two consecutive corresponding points on a wave like crests or troughs.

Amplitude?

Vertical height of a crest or trough above the equilibrium. Measured in meters. Volume.

How do you find the velocity?

Velocity = frequency * wavelength. Its how fast a wave travels through a medium.

How is sound created, and give an example.

By vibrating objects, vocal cords in your throat vibrate to create sound.

What happens when an object vibrates?

Particles in the medium vibrate too.

What’s a medium?

Anything that contains particles.

What happens to the particles in a mdeium when sound moves through it?

They bunch together (compression) and spread apart (rarefaction).

What’s a sound wave made of.

Series of compressions and rarefactions. = longitudinal

What affects the speed of a sound wave?

The medium it travels through. + dense = faster. - dense = slower

What is sonar and how does it work.

Sends out pulses of sound underwater, once it hits an object it reflects the echo back, and time to take to return is used to calculate depth because the speed of sound in water is constant.

Main characteristics of a sound wave?

Frequency, wavelength, and amplitude.

What’s pitch and how is it determined.

How high or low a sound is, it is determined by frequency and wavelength.

How are pitch, frequency and wavelength related?

High pitch —> high frequency = short wavelength

In relation to sound how is amplitude determined?

Linked to loudness.

What kind of sound does a low frequency and long wavelength make?

A low-pitched sound.

Unit to measure sound?

Decibels (dB) —> tells how loud a sound is.

Why isn’t the decibel scale perfect?

Our ears are more sensitive to some sounds than others.

What kind of scale is the decibel scale?

Logarithmic scale —> every 10dB increase = sound is twice as loud.

Function of the ear?

Transforms vibration in the air into signal that the brain can interpret as sound.

Parts of outer ear and function.

• Pinna → flappy cartilage that collects sound waves from environment

• Ear canal → a tube that carries sound waves from pinna to ear drum

Part of middle ear, and functions?

• Ear drum → thin flap of tissue, separates outer from middle ear. Waves vibrate ear drum and passes to ossicles.

• Ossicles → three smallest bone in human body (hammer, anvil stirrup,) magnify vibrations and transmit to inner ear via oval window.

Parts of inner ear, and function?

• Oval window → small membrane covered opening that connects middle and inner ear, transmits vibrations inwards.

• Cochlea → spiral shaped, fluid-filled tube. Vibrations make fluid move, stimulating tiny hair cells on lining —> connected to auditory nerve which connects to brain where sound is interpreted.

• Semi-circular canals -→ responsible for balance not hearing

Cochlear implant?

Bypasses damaged parts of ear and directly stimulates auditory nerves with electrical impulses using electrodes.

Brain stem implant?

Provides sensation of sound for people with severe hearing loss or non-functioning cochlea/auditory nerve, bypassing them and stimulating brainstem directly.

Hearing aid?

Device that amplifies sound, making it easier to hear.

What is ultrasound?

Non-invasive technology that uses high-frequency sound waves for medical imaging and other applications.

What is light?

Light is energy that travels as a transverse wave called electromagnetic radiation, which can travel through a vaccum or medium.

Where does visible light sit on the electromagnetic spectrum?

Visible light lies in the middle of the spectrum.

Other forms of electromagnetic radiation?

Infrared, Microwaves, radio waves, UV radiation. All EMR are transverse waves unlike sound.

What properties does light travel with?

Velocity, frequency and wavelength. fastest thing in the universe, carries energy without carrying matter.

What is a wave in terms of light?

A wave is a disturbance in the electromagnetic field.

How does light interact with surfaces?

• Reflection → light waves bouncing off a surface

• Refraction → light waves bend when passing through a surface

Law of reflection?

Angle of incidence = angle of reflection

What is a plane mirror?

A flat reflective surface

Angle of incidence?

Angle between incoming ray and normal. always <90 degrees

Angle of reflection?

Equal to angle of incidence and angle between reflected ray and normal.

What’s lateral inversion?

A mirror reflection where left and right appear swtiched around.

What types of objects allow light to pass through?

Transparent and translucent objects.

How does the medium affect light?

Light travels at different speed depending on the density of the medium. In a medium, light scatters as particles reflect, absorb and redirect light making it slower.

How does light bend between different mediums?

Into denser medium = bends towards normal

Into less dense medium = bends away from normal.

What is a refracted ray?

The light ray that bends when it enters a new medium.

How do concave and convex lenses refract light?

• Concave lenses → causes rays to diverge (spread out.)

• Convex lens → causes rays to converge to focal point.

What is white light composed of?

White light is made of different colours, each with a different wave length.

Function of eye?

Allows us to detect light and send messages to brain.

Main parts and process of eye?

Cornea, Vitreous & Aqueous Humour, Pupil, Iris, lens, retina, optic nerve.

Light enters cornea, passes the aqueous humour, pupil regulated by iris, focused by the lens, travels through vitreous humour to the retina where signals are sent via optic nerve to the brain.

Cornea?

Is a transparent covering over fornt of eye, no blood vessels and focuses vision.

Aqueous Humour?

A water liquid that distributes nutrients of the cornea and lens.

Pupil & Iris?

The pupil allows light into the eye but dilates in dim light and contracts in bright late this is controlled by the iris that controls the size of the pupil to regulate light and protect eye.

Lens?

Clear, jelly-like substance that focuses light onto retina. Muscles attached to it can change its thickness to ensure proper focus.

Vitreous Humour & retina?

Vitreous humor → jelly-like substance keeps eyes shape. Retina is a tissue lining the back of the eye containing photoreceptors that detect light and converts into electrical message for brain.

• Rods -→ detect light, movement, shapes. Work in dim light, no colour vision, majority of photo receptors.

• Cones → detect colour, require bright light, sends signals to brain to interpret as colour.

Sclera and Choroid?

Sclera - tough, white outer layer that protects and maintains shape of eyeball. outer coat

Choroid - middle layer between sclera and retina, filled with blood vessels to supply oxygen and nutrients to retina.

Reflection off concave (converging) mirror?

Parallel rays of light converge at focal point after reflecting.

Reflection off convex (diverging) mirror?

Parallel rays of light diverge after reflecting.