B10 - The HUman Nervous System Flashcards
What is homeostasis ?
The regulation of the itnernal conditions of a cell of an organsism to maintain the optimum conditiosn for fuction in response to internal and external changes .
An example of why we need homeostasis .
-Enxymes and cells require very stable condtions in order to work .
-What that mens is that enzymes and cells cannot work well if the conditions around them change too uch .
-Because of this , our bodies hae sysems in place to keep the itnernal conditions optimum , in order for the cells to function , this is HOEMOSTASIS .
What does homeostasis consits of ?
-Automatic control sytems , making usre the internal conditions of the body ,s tay as constant as possible .
e.g of the card above .
-An endurance athelete .
-Exercise places lots of demans ont he body .
*FOr exmapel respiration will use glucose to generate energy .
-Causin the blood flucose concentration to fall .
-Causing the atheltes body temperature to rise , they will also loose wter through sweitng .
-So int he human body , homeostasis is used to keep the blood glcose concentration , bodystemperture and water levels cosntant .
IN THE EXAM , ou could be asked to descrie the gerneal features of an automatic contol sytem .
-The automatic control sytems in the body , can involve the nervous or hormones .
Features of an automatic control system invovle ;
RECEPTOR CELLS
CO-ORDINTION CENTER
EFFECTOR
S1
-What are recepotr cells .
Recepotr cells detect changes in the environement .
-THe word ‘environment’ , cold be used to mean the body’s internal conditions , (concentration of glucose in the blood .)
-Or , could mean , the bodies externaal conditions - (temperature of the skin )
What do scientists call a change to the environement ?
Stimulus
S2
The Coordination center.
-The receptor cells , now pss information to the COORDINATION CENTER (THIS COULD EITHER BE THE BRAIN , SPINAL CORD , OR PANCREAS)
-The coordination center , receievs and processes the information fromt he recepotr cells .
S3
EFFECTOR .
The coordination centernows sends instructions to the effector .
-An EFFECTOR , is a muscle or gland .
-THE JOB , of the effector , is to carry out a response (restore the optimum level).
Although , there are lots of systems …
THEY ALL HAV A STIMULUS , RECEPOTR , COORDINATION CENTER , AN EFFECTOR , AND RESPONSE. THIS IS THE ORDER THE WORK IN .
A key part of homeostasis involves …
the nervous sytem .
The nervous sytem contains two parts , what are they ?
(1)The CENTRAL NERVOUS SYTEM (CNS)
This includes thebrian and spinalc ord
(2) Other nerves running to and from the nervous system.
S1
How does the nervous sytem work ?
-Recepotrs detec a stimulus , and sed electrical impulses down nerurones to the central nervous sytem .
(neurones is anoher way of aying nerve cells
S2
How does the nervous system work ?
-The central nervous system IS the cooridntion center .
-This now sends electrical impulses , down the other neurones to the effecotrs .
-And the effectors bring about the resposne .
S3
How does the nervous sytem work?
-The effectors are usually a msucle which contracts , or a gland which secretes a hormone .
A KEY , role of the nervous system is ?
That it enables humans to react to their surroundings and coordinate thier behabiour .
-One wya this is done is thorugh the REFLEX ARC .
EXAM QUESTION
WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
S1-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
-First the stimuus is detected by the receptor .
-In this case , the stimulus is heat , and the receptors in the skin .
S2-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
Eleectrical impulses now pass from the receptor , along a sensory neurone , to the central nervous system.
Sensory Neurones
Sensory neurones are connected to receptors , and receptors allow us to sense our environment.
S3-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
At the end of a sensory neurone , is a junction called a synapse . t the syynapse , a chemical is released .
S4-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
The chemical now diffuses acorss a relayneurone , in the central nervous system , where it triggers an electrical impulse .
S5-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
The electrical impulse , now passes across the replay neurone and reaches another synapse .
S6-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
Once again , this chemical is released.
S7-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
This chemical , triggers ,a ne electrical impulse in the motor neurones .
S8-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
The electrical impulse now passes down the motor neurone to an effector . (in this case a muscle )
S9-WHAT HAPPENS WHEN YOU TOUCH HOT OBJECTS .
-The msucle now contracts and (pulls the hand away from the hand - this is the response).
KEY POINT ABOUT REFLEXES ,
-THE CNS acts as a cooridnator , and in most cases , the brian makes decisions about what ction to call .
-However , int he case of reflexes , there is NO DECISION MAKING , by the conscious part of the brain , Maing reflexes AUTOATIC and RAPID .
-As they are RAPID , reflexes help to protect us from danger .
WHAT IS THE RQP ABOTU ?
-Describe , how to measure a persons reaction time .
Practical requires 2 peopme (perosn1 +and person2)
-Peron 2 will measure the reaction fime of person 1
S1 of RQP
First , person 1 , sits on a stoll , with a good upright posture .
S2 of RQP
Person 2 , then places their forearm of the dominant arm , across the able , with their hand overhanging the egde .
9if you are rightahdned , thats your dominant hand).
S3 of RQP
pERSON 2 HOLDS , a ruler verticallly
S4 OF RQP
the 0 cm mark , XHOULD BE ETWEEN PERSON1’S THUMB AND FIRST finger .
Person 2 , then tells person 1 to prepeare to catch the ruler , then person 2 drops the ruler at a random time .
Person 2 , then tells person 1 to prepeare to catch the ruler , then person 2 drops the ruler at a random time .
S5 RQP
Person 2 , then tells person 1 to prepeare to catch the ruler , then person 2 drops the ruler at a random time .
S6 RQP
Person 1 , has to catch the ruler with their thumb and first finger as quickly as possible , when it drops .
S7 RQP
Persn 2 ,, now records the measurmemen , ont he ruler ,t hat is level with the top of person1’s thumb .
S8 RQP
Person 1 , now has a hsort break .
-The tests is then rpeeated several times , and then a mean is clacualted .
S9 of RQP
From these experiments , we can covert our results to a reaction time . (We can use a onversion tbale online to do this .)
S10 RQP
Now person 1+2 switch places , with person1 , teasting the reaction time of person 2 .
S11 of RQP
This allws us to see whether the two people have different reactiont imes .
What is the Independant variable ?
Person haveing thier reaction time tested .
What is the dependant variable ?
Reaction time .
What is the control varible ?
-Starting distance between the finger and thumb , easure ruler always at the top of the thumb .
-Keep the conditions of the room safe , lighting nd background noise .
What would happen if the control variables changed ?
Could effect the dependant variable , the reactiont ime .
One other indepedant variable we could investiage ?
-Effect of practise , tos ee if reactoin time changes depending on the number of tries .
-as they have more tires . (Might expect thier reaction time to be shorter , as the person has gotten more practise.)
Another independant , variable we could investigate ?
-Whether reaction time depends on the hand , cthcing the ruler .
(Carry out this test with dominant hand , and non dominant hand of the same person .)
-As the dominant hand is used more often , might expect , reactoin time to be shorter , with the domiannt hand , rather than the non-dominant hand .
Final independant varibale we could investigate ?
-Whether chemicals affect reactoin time e.,g caffeine .
-Test subject drinks a measured amount of cola half an hr beofre the expermient .
-Then compare this reaction time , with thier normal reaction time .
Problem - there could be another chemical in the cola , which is affecring the reaction toieme ,
-So use a caffeine free cola , and compare this reaction time with thier normal reaction time .
Safet of this RQP WITH CHEMCCAL independant variable .
*As we are giving test subjects something to drink , make sure there is no medical issue affected by caffeine , like heart conditions or allergy .
-Also , carry out the tests , here hazardous chemicals are not usually used .
What do brain do ?
-The Brain plays a critical role in the CENTRL NERVOUS SYSTEM .
-As the brian controlls complex behaviour e.g language .
-To do this , the brian contains billions of interconnected neurones .
Different parts of the brain carry out different functions .
-In the exam , you coul dbe asked to identify three different pats of the brain and describe their functions .
… yeah
CEREBAL CORTEX
-The highly folded outer part of the brain is the cerebal cortex .
-The functions of this cerebal cortex include , language , memory and consciousness .
CEREBELLUM
-The second part of the brain is called the cerebellum .
-This controls balance and co-odiantes our movements .
MEDULLA
-FInal part of the brain is the medulla .
-This controlls our heartrae and breathing rate .
Studying the brain is extremely difficult .
-It is also difficult to treat brain diseases , or brain damage .
…
One reason why the brain is difficult ot study .
-The brain is proteced by the skull . So it is very tricky acess
Another reason why the brain is difficult to study .
-Strucutres of the brain are extremely complex .
-It is difficult to work out exactly , which parts of the brain carry out specific functions .
Final reason why the brain is difficult to study .
-The brain is extremely delicate and eay to damage .
There are three ways scientists can use to investigate the brain .
…
One way scientists can use to investigate the brain .
-Many scientsits look t patients who have suffered brain damage .
-By looking to see where the damage has taken palce , they cn try to link that part of the rain to its function .
Another way scientists can use to investigate the brain .
-We can also electrically stimulate different parts of the brain and look at the effects oon the persons behaviour .
-allowing us to narrow down specific regions to their funcitons .
The final way scientists can use to investigate the brain .
-We can also use MRI scanning , to look at which parts of the brain are most active during activities .
(e.g when a person is looking at images , we can see greater activity in the part of the brain responsible for image processing .)
What type of organ is the eye ?
The eye is a SENSE ORGAN .
-It contians receptors sensitive to both light intensity and also he colour of light .
How the eye detects light S1
-Light rays pass through the transparent frnt of the eye , this is called the cornea .
-The JOB of the cornea is to start the focussing of the light rays .
How the eye detects light S2
-The light rays then pass through the pupil , in the center of the iris .
-This IRIS , is the coloured part of the eye .
How the eye detects light S3
-Light rays then [ass through the lens .
-The JOB of the lens is to focus the light rays onto the back of the eye .
What is one KEY feature of the lens ?
-It can chnage its shape , allowing us to foucs on distant or near objects . This is known as ACCOMODATION .
How the eye detects light S4
-The light rays are then focused onto the back of these , this is called the RETINA .
-The retina contains the receptor cells for lgiht .
-These receptors allow us to detect light intensity and light colour .
How the eye detects light S5
-The receptor cells in the retina , now send electrical impulses down the optic nerve , to the brain .
OTHER PARTS OF THE EYE I NEED TO KNOW .(1)
-The white part of the eye is known as the sclera .
-This tough outer structure protects the eye .
OTHER PARTS OF THE EYE I NEED TO KNOW (2)
-the cillary muscles and suspensory ligaments work with the cells .
-Together they allow u to focus in distant or near objects .
THE PUPIL
-The pupil is the space in the center of the iris , where light passes through .
-The pupil allows light rays to pass into the eye and the job of the iris is to control the size of the pupil .
What happens if you enter a DARK ROOM ?
-The amount of light entering the eye is now LOW .
-This drop in light intensity is now sensed by the light receptors in the retina , and these send electical impulses to the brain .
-The brain then sends electrical impulses to specific muslces in the iris .
-These muscles hen conract causing the pupil to become larger .
-This now allows more light to enter they eye .
What happens in a LIGHT ROOM ?
-We can see the opposite in a light room .
-In this case , the reflex causes the pupil to become smaller , reducing the amount of light entering the eye , protecting it from dmage .
A lot of the foucidng of objects is crried out by what ?
-By the cornea .
-But the cornea is a fixed focus .
The rest of the foucsing is carried out by the lens .
-The lens allows us to focus on near , or distant objects .
-To do this , the shape of the lesn can change .
-tHIS IS accomaadatoin
How does accomodation take place s1
-The lens is surroudnd by a circular msucle , clled the CILLARY MUSLCE .
-This is conected to the lens by fibres , which ar called supsensory ligaments .
How does accomodation take place S2
-by contracting or relaxing the cillary muscle can change , the thickness of the lens .
How does accomodation take place S3
-When the cillary msucle contracts , the suspensory ligaments loosen .
-The lens is now thicker and refracts rays more strongly .
How does accomodation take place S4
-However , when the cillary muslce relaxes , the suspensory ligaments are pulled tight .
-THe lens is now pulled thin , and only slightly refrcts ligh rays .
FOCUSING ON DISTANT OBJECTS ;
KEY - Light from didstant objects need to be focused only a relatively small amount .
-So in this cas e, the cillry muscle relaxs , and the suspensory ligamnets re pulled tight . -The lens is now pulled thin ,.
-As the lens is thinn , the light rays are only lsightly refracted .
-The light rays are now focused to a pointon the retina .
NEAR OBJECT
-Light from near objects need to be focused a large amount .
-In this case , the cillary msucle contrac ts .
-This causes the suspensorY ligamnets to loosen
NEAR OBJECT (2)
-Now the lens is thicker and reracts the light rays more strongly .
-Again , the light rays are now focused to a point on the retina .
In some people , the light rays do not focus correctly on the retina.
-These people can be shortsighted or longsighted .
LONGSIGHTEDNESS
AKA AS HYPEROPIA
-people with longishtedness have no problem at all focusing on distant objects . -But they cannot focus on nearby objects .
-In amny cases , the eyeball is too short ..
-So the light is focused t a point behind the retina .
Elderly people - longsightedness .
-In some cases , especially in the elderly , the lens becomes less elastic .
-n this case , the lens cannot become thick enough to focus on near objecs.
TREATMENT TO LONGSIGHTEDNESS.
-Glasses with convex lenses , these partially focus the light efore it enters the eye .
SHORTSIGHTEDNESS
AKA MYOPIA
-People with shoert sight can focus on nearby objects , but cannot focus on ones far away .
-In people with short siht , the eyeball can be too long .
-So the light is focused on a point in front of the retina .
SHORTSIGHTEDNESS (2)
-Short sight can also be caused when the lens is too thick , therefore , light is focused infront of the retina .
THE TREATMENT FOR SHORT SIGHTENDESS , s glasses with CONCAVE LENSES .
-This is to partially unfocus the light before it enters the eyE .
CONTACT LENSES
-Instead of glasses , people can use hard or soft contact lenses ,
-These lenses sit on the eyeball , and they refract the light the same way as glasses.
Recently - new trements have been developed for short+long sightedness
-LASER SURGERY - can be used to change the shape of the cornea , so it refracts the light to a greater or lesser extent .
-SOmetimes , the lens inside the eye can be replaced using an ARTIFICAL LENS .
