GCSE Biology B5- Homeostasis and Response

What is homeostasis?

the regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes. this is needed for enzyme action and all cell functions

what does homeostasis control in the body?

- blood glucose concenration (to provide the cells with a constant supply of energy)

_ water levels (water can be lost via: lungs, skin, kidneys when we urinate)

- body temperature (to maintain temp at which enzymes work best)

what is a receptor?

organs or cells that detect a stimuli

what are coordination centres?

areas in the body like the brain, spinal chord and pancreas that recieve and process information from receptors

what is a stimuli?

changes in the environment

what is an effector?

Muscles or glands that bring about responses which restore optimum levels

what does the nervous system enable humans to do?

react to our surroundings, coordinate actions in response to stimuli

what is a response

a reaction to the stimuli

What is the endocrine system?

glands that create a chemical message

what is the nervous system?

sends messages back and forth between the brain and the body

adaptations of a nerve cell

they have long axons in order to send electrical impulses quickly

The process

- the receptor cells in your skin detect internal and external stimuli and the information passes along the sensory neuron as an electrical impulse to the central nervous system (CNS) and passes along the relay neuron

- Then diffuses along to the motor neuron and a response occurs which is the effector which may be muscles contracting or glands secreting hormones

what type of signal is nervous

electrical impulses but chemical at synapses

what is the transmission of signal of nervous

nerve cells (neurones)

what is the transmission of signal of hormonal

by the bloodstream

what type of signal is hormonal

chemical

what effector is the nervous

muscles (contraction), glands (secretion)

what effector is the hormonal

target cells in partciular organs (glands)

what type of response is the nervous

muscle contraction or secretion from glands

what type of response is the hormonal

chemical change

speed of response of nervous

very rapid

speed of response of hormonal

slower

duration of nervous response

short and quick response. lasts for as long as there is a stimulus (until nerve impulses stop)

duration of hormonal response

long (until hormones are broken down)

what is a hormone

a chemical substance, produced by a gland and carried in the bloodstream to alter the activity of a specific target organ

if the temperature control factor is too high what happens

we sweat

if the water control factor is too high what happens

produce more urine

if the sugar control factor is too high what happens

produces insulin

if the temperature control factor is too low what happens

we shiver

if the water control factor is too low what happens

urine is very yellow

if the sugar control factor is too low what happens

produces glucagon

what controls body temperature

brain

what controls water levels

kidneys

what controls sugar concentration

pancreas

why are reflex actions important?

they are rapid, automatic and do not require the conscious part of the brain so they can respond to harm to the body

what is the synapse

the gaps between two neurons

examples of receptors

skin cells, eye cells, taste buds

what is a sense organ

a group of receptor cells e.g. eye, ear

what is a neuron

nerves are called neurones. they carry electrical impulses from one place to another. a bundle of neurons is a nerve

main features of a neuron

- dendrites

- long

- insultaed

what does the brain stem do?

controls:

- subconscious movements

- breathing

- blood pressure

- heartbeat

what does the spinal chord do?

carries nerve signals from your brain to the rest of your body and back and they help you feel sensations and move your body

how the nerve impulse travels betwee the synapse

- when the nerve impulse arrives at the synapse

- a chemical messenger (neurotransmitter) is released into the synapse

- the impulse causes the vesticles to fuse with the neuron membrane and the neurotransmitters diffuse across the synapse and bind with a veceptor on the membran of the post synaptic neuron

- binding of the transmitter to the recepter stimulates and impulse in the posynaptic neuron

what can effect your reaction time?

- age

- gender

- amount of practice

the brain

a protected organ in your skull that is made up of billions of interconnected neurons from different regions and controls complex behavior

what is reaction time

how long it takes for you to respond to a stimulus

cerebral cortex

controls consciousness, intelligense, memory and language, it is the outer part of the brain

cerebellum

controls fine movement of muscles and balance, rounded structure towards the bottom/back of the brain

medulla (oblongata)

controls unconscious activity such as heartbeat, breathing, the movement of the gut, found in the brain ste in front of the cerebellum

spinal chord

a long thing tubular structure made of nervous tissue connected to the medulla

hypothalamus

helps release hormones and regulates body temperature

pituatary gland

takes messages from the brain (via hypothalamus) to produce hormones that affects many parts of the body

why is investigating brain function and treating brain damage difficult

- it is complex and delicate

- easily damaged

- drugs given to treat diseases cannot always reach the brain because of the membranes that surround it

- it is not fully understood which part of the braind does what

how can neuroscientists map out regions of the brain

- studying patients with brain damage.

- electrically stimulating different parts of the brain

- using an MRI

studying patients with brain damage

observing the changes in an individual following damage on a certain area of the brain can provide information on the role this area has

electrical stimulation

- electrodes are implanted in the brain or on the scalp

- electrical current is passed through the brain to alter the brain function

- magnetic fields are applied to the head to induce electrical stimulation

- patients are asked to describe what they experience - movement if the motor area is stimulated or a flash of colour if the visual area is stimulated

what can electrical stimulation treat

- treating movement disorders (parkinsons)

- treating neuropsychiatric conditions (epilepsy, tourettes, OCD)

treating mental disorders (depressions

MRI

magnetic resonance imaging

- uses a strong magnetic field and radio waves to show brain structure nad function

- patients are asked to perform tasks while doctors view the scans

doctors can see which parts of the brain is active while the patients does the task

CT Scan

computed tomography

- patients passes through a ring that takes x-ray images from different angles

PET Scan

positron emission tomogrpahy

- used to detect high levels of metabolic reactions inside the patient

- before scanning, patient swallows a tracer ( a chemical compound that emits gamma rays)

- the tracer will travel to any area of the body that has unusually high levels of metabolic reactions

- often used to view tumours or diagnose cancer

Label the eye

the eye

a sense organ containing receptors sensitive to light intensity and colour

sclera

white outer layer which supports the structure inside the eye. it is strong to prevent damage

cornea

the transparent layer at the front of the eye which allows light through and refracts light onto the retina

pupil

the hole in the centre of the eye, through which light enters

iris

muscles that surround the pupil tha contract and relax to alter the size of the pupil (accomodation)

retina

layer of light sensitive cells at the back of the eye. there are two types of light receptor cells. one is sensitive to light intensity and the other is sensitive to colour. when light/ colour hits the cells are stimulated and impulses are sent to the brain which interprets the information to create an image

lens

focuses the light onto the retina

ciliary muscle

controls the shape of the lens

optic nerve

carries impulses from the receptors on the retina to the brain

suspensory ligaments

holds the ciliary muscle in place

why do pupils dilate and constrict

to allow as much light in as possible in the dark or to allow less light in to reduce stran on the eyes when there is a sudden change in light. the muscles in your iris controls the size of your pupil

how does the eye react to dim light

circular relax , radial contract to allow as much light in as possible so the pupils dilate

how does the eye react to bright light

circular contract, radial relax to allow less light in as the pupils constrict

what is accommodation

the process of changing the shape of the lens to focus on near or distant objects eually well

what is a gland

a group of cells that secrete chemicals called hormones directly into the bloodstream

what is glucagon

a hormone produced by the pancreas that causes glycogen to be converted into glucose and released into the blood

target organ

an organ which a hormone acts on to produce an effect

rod cells

work best in low light levels but only detect presence or absence of light

cone cells

there are two types of cone cells, each responding to a different wavelength of light (colour RGB)

what is on the outer segment of the rod and cone cells

containing photosensitive chemicals

what needs to occur when the object is further

less refraction is needed to occur to see the object

how to focus on near objects

- ciliary muscles tighten

- so the suspensory ligaments loosen

- the lens curves and thickens

- light rays are strongly refracted onto the retina

how to focus on far away objects

- ciliary muscles relax

- so the suspensory ligaments tighten

- this flatten and thins the lens

- light rays are only slightly refracted and focused onto the retina

what happens to your lens when you get older

the lens get harder which makes accommodation difficult. this makes it difficult to focus on objects both near and far

when an object is far what light ray is it

diverging

when an object is near what light ray is it

parallel

Myopia

- short sightedness (unable to focus on distant objects)

- the light is being focused in front of the retina causing the image to appear blurred

Causes of Myopia

lens is too curved or a long eyeball

treatments for myopia

wearing thicker glasses with concave lens which refocuses the rays onto the retina

Hyperopia

- long sightedness (unable to focus on near objects)

- the light is being focused behind the retina causing the image to appeared blurred

Causes of Hyperopia

lens is too flat and thin or a short eyeball

treatments for hyperopia

wearing thinner glasses with a convex lens which refocuses the rays onto the retina

treatment methods for hyperopia and myopia

- spectacle lenses (glasses) which can bring the rays together(hyperopia/ concave lenses)) or spread out the light (myopia/ convex lenses)

- contact lenses. hard or soft contact lenses lasts for different amount of times and allows you to do activities such as sports

- laser eye surgery. lasers can be used either to reduce the thickness of the cornea (so it refracts light less) to treat myopia or change its curvature (so it refracts light more strongly) to treat hyperopia

- replacement lens. treats hyperopia by replacing the lens with an articial one made of clear plastic (or adding the plastic on top of the natural lens.

pros of contact lenses

thin, lightweight, more convenient for sport

cons of contact lenses

higher risk of eye infection

pros of laser eye surgery

permanent change to the shape of cornea

cons of laser eye surgery

risk of complications with surgery, infection or eye reacting poorly to surgery or vision becomes worse

pros of replacement lens surgery

permanent change

cons of replacement lens surgery

mugh higher risk than laser eye surgery. possible damage to the retina and cataracts developic (lens becomes cloudy/opaque). could lead to loss of sight