Paper 2: Topic 5 Homeostasis & response - Nervous system (LV) Flashcards
(108 cards)
1
Q
Why do single-celled organisms not need a nervous system?
A
They can respond to changes in their environment easily and directly
2
Q
Why does a multi-cellular organism need a nervous system?
A
- So that they can react to changes in their environment AND control and regulate changes in the different part of the body
- The nervous system allows cells to communicate with each other so a controlled response occurs
- A nervous system ensures co-ordinated behaviour
3
Q
What structures are the main parts of the central nervous system?
What is the peripheral nervous system?
A
The CNS is made up of the
- Brain
- Spinal cord
The peripheral nervous system is made up of all the other nerves in the body that lead into and out of the of the spinal cord.
4
Q
Describe how the central nervous system is connected to the other parts of the body?
A
Sensory and motor neurones in the peripheral nervous system
5
Q
Define the term receptor
A
A cell that detects a stimulus (change in the environment)
AND
that can generate/produce a nerve impulse
6
Q
State 4 different types of receptor
A
- Sound receptors
- Light receptors (photoreceptors)
- Chemical receptors (chemoreceptors)
- Pressure receptors
7
Q
Define the term effector
A
A muscle or gland that responds to nerve impulses and causes a response
8
Q
State how muscles respond to nerve impulses
A
They contract
HINT: do NOT write they “contract AND RELAX” - the impulse only causes them to contract
9
Q
State how glands respond to nerve impulses
A
Glands produce and secrete a hormone into the plasma
10
Q
State the function of the central nervous system
A
To receive and process information from the receptors AND
to co-ordinate the response
11
Q
Write the pathway of a nerve impulse from stimulus to response (reflex arc)
A
Stimulus → receptor -→ sensory neurone → central nervous system → motor neurone → effector → response
Remember in a reflex action the brain is not involved
12
Q
Explain why not all multi-cellular organisms have a nervous system
A
Only large, multi-cellular organisms have a nevous system
Small multi-cellular organsims e.g. jelly fish rely on reflex reponses
13
Q
State the function of a neurone
A
To transmit a nerve impulse
14
Q
Define the term ‘synapse’
A
A junction between two neurones
HINT: do NOT say “a gap” this is incorrect
15
Q
Describe how a nerve impulse is transmitted across a synapse
A
- Vesicles containing neurotransmitters travel to the end of the axon (pre synaptic membrane)
- The vesicles fuse with the pre-synaptic membrane
- The neurotransmitters are released into the synapse
- The neurotransmitters diffuse across the synapse
- The neurotransmitters bind to specific receptors on the membrane of the next neurone (post-synaptic neurone)
- And this then triggers the nerve impulse in the next neurone
16
Q
Define the term neurotransmitter
A
A specialised chemical that is released from the end of the axon of one neurone that can diffuse across a synapse to trigger a nerve impulse in the next neurone
Neurotransmitters are chemical messengers
17
Q
Explain the purpose of reflex actions
A
To prevent damage or harm to the organism.
They are rapid, they always result in the same response** and they are involuntary.
18
Q
State 5 examples of relex actions
A
- Blinking
- Coughing
- Sneezing
- Vomiting
- Knee-jerk
- Iris-reflex
19
Q
Describe a reflex arc
Hint: 6 main stages
A
- A change in the environment occurs (a stimulus)
- A receptor cell detects the stimulus
- A nerve impulse is sent along the sensory neurone to the CNS
- The nerve impulse is passed through the relay neurone in the CNS (NOT the brain)
- The nerve impulse is sent along a motor neurone to the effector
- The effector brings about a response (either a muscle contracts or a gland secretes a hormone)
20
Q
What is the role (function) of a sensory neurone?
A
To transmit a nerve impulse from the receptor to the relay neurone
21
Q
What is the role/function of a relay neurone?
A
To transmit a nerve impulse from the sensory neurone to the motor neurone
22
Q
What is the role/function of a motor neruone?
A
To transmit a nerve impulse from the relay neurone to the effector
23
Q
Explain the advantage of using reflex actions
A
- Quicker response time i.e. rapid response
- Which reduces damage and harm to the organism
24
Q
Define a reflex action
Hint:
This is a similar question to “state the charcateristics of a reflex action”
A
A rapid, automatic response that does not involve the conscious part of the brain
Characteristics of a reflex action:
- rapid / fast
- involuntary response i.e. subconcious
25
State which 2 parts of the CNS a reflex arc may pass through
The spinal cord
**OR**
An **un**conscious part of the brain
26
Define the term reaction time
The time it takes to respond to a stimulus
27
State 4 factors that can affect the reaction time
* Age
* Alcohol
* Biological sex (do not say ‘gender’ as this is inappropriate in this context)
* Drugs e.g. caffeine
28
Describe the effect caffeine has a person’s reaction time
* Speeds the reaction time up
* i.e. *time* to respond to a stimulus *decreases*
* hence caffeine is a stimulant
29
Describe the effect alcohol has a person’s reaction time
* Slows down the reaction time
* i.e. *time* to respond to a stimulus *increases*
* hence alcohol is a depressant
30
Describe how a person’s reaction time can be measured
* Use the dropping a ruler technique
**OR**
* Use a computer programme
31
An investigation studying the effect of gender on reaction time is carried out using the dropped ruler technique.
State 4 factors that should be controlled to make the investigation valid
* Only use participants of the same age
* Ensure no participants have consumed any caffeinated drinks prior to the test
* Make sure all the participants use their dominant hand
* Make sure the ruler is dropped from the same height each time
32
State two advantage of using a computer programme rather than the dropped ruler technique to determine a person’s reaction time
* A computer programme will give reactions times to a **greater level of precision** (as they remove human error)
* A computer programme will give **more accurate** reaction times (they can record in milliseconds)
* The participant is **unable to ‘predict**’ the test using a computer programme (when using the ruler technique participants can try to predict when the ruler is going to be dropped)
33
State 2 safety issues that should be considered if you are investigating the effect of caffeine on reaction times
* Check the participants on not taking any medication that may be affected by caffeine
* Advise participants to not consume any more caffeine after the test as high levels of caffeine can cause side effects e.g. heart palpitations, sweats
34
Describe the structure of the brain
A mass of billions of interconnected neurones
35
Describe the function of the brain
To control complex behaviour
36
State the 3 main regions of the brain
1. Cerebellum
2. Cerebral cortex (also called cerebrum or cerebral hemispheres)
3. Medulla oblongata
37
Describe the location and role/function of the cerebral cortex
* This is the outer part of the brain
* It is located at the front of the brain
* It controls voluntary movement
* It also controls consciousness, memory , intelligence and language
38
Describe the location and role/function of the cerebellum
* It is located at the back of the brain
* It is responsible for co-ordination of movement (using muscles)
* It maintains body posture and balance
39
Describe the role/function of the medulla oblongata
* It is located at the base of the brain at the top of the spinal cord
* It is controls unconscious activities (involuntary actions)
* For example breathing RATE, heart RATE
* It also relays impulses between the brain and spinal cord
40
What is the name given to scientists who study the brain?
Neuroscientists
41
State 3 methods neuroscientists have used to study the brain
1. Studying patients with brain damage
2. Electronically stimulating the brain
3. MRI scans
42
Describe how neuroscientists have studied patients with brain damage to make discoveries about brain function
By studying which part of the brain is damaged in different patients scientists can study the effect different types of damage has on their behaviour etc
43
Describe how neuroscientists have used electrodes to make discoveries about brain function
By artificially stimulating the brain with tiny electrodes in the brain tissue it is possible to determine which parts are responsible for specific functions
44
Describe how neuroscientists have used MRI scans to make discoveries about brain function
* Magnetic resonance imaging produces very detailed images of the brain structure.
* Scientists can study which parts of the brain are more active when patients are doing certain activities whilst inside the MRI scanner e.g. talking, listening to music, speaking a foreign language
45
State 3 reasons why some people are against neuroscientists using electrode stimulation to study the brain
1. Due to the complexity of the brain inserting the electrodes can cause physical damage to the brain
2. It can result in a higher risk of problems with brain function e.g. difficulties with speech
3. Long-term effects of using this technique are not yet understood (as it is a relatively new process)
46
Explain why the brain is a difficult organ to study
* It is a complex and delicate organ
* Which can easily be damaged
* If damage occurs it can result in life-changing consequences
* E.g. loss of mobility, speech impediments, memory loss
47
What type of organ is the eye?
Sense organ
48
Name the 2 types of stimuli the eye detects
1. Light intensity
2. Colour
49
State what type of receptors are found in the eye
Photoreceptors
50
Describe the role/function of the sclera
Tough, white outer layer of the eye which supports the eye
51
Describe the role/function of the retina
This layer contains the photoreceptor cells which can detect either the colour of the light (wavelength) or the light intensity
52
Describe the role/function of the cornea
* The cornea is a transparent, outer layer at the front of the eye
* It refracts (bends) the light
53
Describe the role/function of the optic nerve
The optic nerve carries the nerve impulses from the photoreceptors in the retina to the brain
54
Describe the role/function of the iris
* The iris is contains 2 sets of muscles
* These are the radial and circular muscles
* These muscles contract or relax to control the size of the pupil
* i.e. the iris controls the level (intensity) of light that enters the eye and reaches the retina
55
Describe the role/function of the ciliary muscles
* The ciliary muscles control the shape of the lens:
* if the ciliary muscles contract they allow the lens to be thicker
* if the ciliary muscles relax they pull the lens thinner
56
Describe the role/function of the suspensory ligaments
* The suspensory ligaments control the shape of the lens:
* if the suspensory ligament are pulled tight they make the lens thinner
* if the suspensory ligaments are slack they allow the lens to be thicker
57
Describe the role/function of the lens
* The lens focuses the light rays onto the retina
* To enable the photoreceptors to detect the stimulus
* If the lens is thin it only slightly refracts (bends) the light
* If the lens is thick then it strongly refracts (bends) the light
58
Describe how the eye focuses on a near object
* The ciliary muscles contract so their diameter reduces
* The suspensory ligaments are loose & slack
* The lens is thicker and more curved
* The lens is more convergent
* The light rays are refracted more strongly
* Light rays then converge on the retina to focus the image
59
Describe how the eye focuses on a distant object
* The ciliary muscles relax so their diameter increases
* The suspensory ligaments are tight and taught
* The lens is thinner and less curved
* The lens is more divergent
* The light rays are refracted less strongly
* Light rays then converge on the retina to focus the image
60
Describe how the eye responds to bright light
* The circular muscles of the iris contract
* The radial muscles of the iris are relaxed
* The pupil has a narrower diameter
* Less light enters the eye
* Less light hits the photoreceptors in the retina
61
Describe how the eye responds in dim light
* The radial muscles of the iris contract
* The circular muscles of the iris are relaxed
* The pupil has a wider diameter
* More light enters the eye
* More light hits the photoreceptors in the retina
62
Name the type of response that is shown when the iris changes size
Reflex action
63
Define the term accommodation (in the eye)
The reflex process of changing the shape of the lens to focus on a near or distant object
64
Name the type of response that is shown when the eye accommodates an object
Reflex action
65
Explain why a person’s eyesight may deteriorate as they age
* The lens loses flexibility as a it ages
* This prevents it changing shape easily
* Light refraction becomes more difficult
* Often meaning the person has to wear glasses
66
Describe what is meant by the term ‘long-sighted’
The person is unable to focus on a nearby object
67
Describe what is meant by the term ‘short-sighted’
The person is unable to focus on a distant object
68
Explain how a person may become long-sighted
* The shape of the lens is too thin or the shape of the eyeball is too short
* The light rays are not focussed on the retina
* They converge at a point behind the retina
* This causes the object to be focussed behind the retina
69
Describe how to correct long-sighted vision
Prescribe glasses with a **convex lens** (lens curves outwards)
70
Explain how to correct long-sighted vision
* Prescribe glasses with a **convex** lens
* This lens refracts the light **more strongly**
* So that the light rays focus on the retina
71
State the medical term for long-sight
Hyperopia
72
Explain how a person may become short-sighted
* The shape of the lens is too thick or the shape of the eyeball is too long
* The light rays are not focussed on the retina
* They converge at a point IN FRONT of the retina (within the vitreous humour)
* This causes the object to be focussed in front of the retina
73
Describe how to correct short-sighted vision
Prescribe glasses with a concave lens (lens curves inwards)
74
Explain how to correct short-sighted vision
Prescribe glasses with a concave lens
This lens refracts the light less strongly
So that the light rays focus on the retina
75
State the medical term for short-sight
Myopia
76
State 3 different new technologies that can be used to correct vision defects
1. Hard and soft contact lenses
2. Laser eye surgery
3. Replacement lenses (biological and artificial)
77
State 2 new technologies that can be used to change the shape of the lens to correct vision defects
1. Hard and soft contact lenses
2. Lens replacement surgery
78
Explain how contact lenses can be used to correct vision defects
* Contact lenses sit on the surface of the cornea
* They refract the light rays more or less (depending on the vision defect)
79
State 3 advantages of using contact lenses to correct vision defects
1. They are lightweight
2. They are convenient e.g. sport
3. It is easier to change a prescription if a persons vision changes (unlike with glasses which is costly and time consuming)
80
State 2 disadvantages of using contact lenses to correct vision defects
1. There is a risk of eye infections (more so with soft lenses than hard lenses)
2. They require a high level of hygiene when changing and cleaning them to prevent infection
81
State 2 advantages of using laser eye surgery to correct vision defects
1. It can lead to a permanent resolution (‘fix’)
2. It is a quick procedure (only ~3 hours required at hospital with no overnight stay i.e. day operation)
82
State 4 disadvantages of using laser eye surgery to correct vision defects
1. There is a risk of complications during surgery
2. The long-term effect is not fully understood
3. It may not be 100% effective and so the patient may still need to wear glasses
4. Vision may actually be made worse! The cost of the surgery
83
Explain how laser eye-surgery can correct vision defects
* A laser is used to vaporise tissue
* This changes the shape of the lens
* Which changes how much the lens refracts the light
* Making the lens thinner will correct short-sightedness
* Making the lens thicker will correct long-sightedness
84
Describe 3 risks associated with laser surgery
1. There are risks of complications as a result of the surgery e.g. reacting to the anaesthetic
2. There are risks of post-operative infection
3. There are risks of damaging other parts of the eye with the laser
85
Explain how lens replacement surgery can correct vision defects
* The damaged lens is removed and replaced with an different lens
* The artificial lens can be from a dead donor (cadaver) or an artificial lens made from clear plastic
86
Describe 3 risks associated with lens replacement surgery
1. There are risks of complications as a result of the surgery e.g. reacting to the anaesthetic
2. There are risks of post-operative infection
3. There are risks of damaging the retina during surgery (which could result in total loss of sight)
87
State which part of the brain monitors and controls body temperature in humans
The thermoregulatory centre in the hypothalamus
88
State what type of receptors are found in the thermoregulatory centre of the brain
Thermoreceptors
89
Describe the stimulus that is detected by the thermoreceptors in the thermoregulatory centre of the brain
The temperature of the blood flowing through the brain
90
Other than the thermoregulatory centre of the brain which other part of the body contains thermoreceptors?
The skin
91
Describe the stimulus that is detected by the thermoreceptors in the skin
The temperature of the skin
92
Define the term ‘core body temperature’
The temperature of the body’s internal organs (usually approximately 37 degrees C)
93
Describe the role/function of the thermoreceptors in the skin
To detect the change in temperature (stimulus) and send nerve impulses to the thermoregulatory centre
94
**Describe** how the body responds if the core body temperature is too high
**Arterioles** supplying the skin WIDEN (vasodilation)
**More** blood flows through the capillaries close the the **surface of the skin**
**More** sweat is produced from the sweat glands
Sweat **evaporates** from the skin
These **increase heat loss** and so *cools the body* MORE and **prevent overheating**
Hairs also lie flat on the surface of the skin
95
**Explain** the how vasodilation helps reduce the core body temperature
***** The diameter of the **arteriole** lumen **INCREASES** (vasodilation)
* This means **MORE** blood flows into **capillaries** to the surface of the skin
* This **INCREASES** the transfer of energy from the skin to the environment
* This then **REDUCES** the temperature of the blood returning to the core of the body
* Hence **REDUCING** the core body temperature
96
**Describe** how the body responds if the core body temperature is too low
* Arterioles supplying the skin narrow (vasoconstriction)
* Reduces blood to the surface of the skin so LESS heat energy is lost
* No sweat is produced from the sweat glands
* Skeletal muscles contract at a high rate (shivering)
* Hairs on the surface of the skin are erect
97
**Explain** the how vasoconstriction helps raise the core body temperature
* The diameter of the lumen of the arterioles decreases (vasoconstriction)
* This means less blood flows to the surface of the skin
* This decreases the transfer of energy from the skin to the environment
* This then ensures the temperature of the blood returning to the core of the body remains high
* Hence increasing the core body temperature
98
**Explain** the how shivering helps increase the core body temperature
* As the skeletal muscles contract more the rate of respiration in the muscle cells increases
* This is necessary to produce more ATP
* To enable the skeletal muscles to contract more frequently
* Respiration is an exothermic reaction so transfers more energy to the environment
* Hence raising the temperature of the blood flowing though the skeletal muscles
* The heat is then transferred to the core organs as blood flows through the body
99
**Explain** how the increased sweating helps reduce the core body temperature
* The sweat glands increase the quantity of sweat produced
* The sweat accumulates on the surface of the skin
* The sweat evaporates
* As the sweat evaporates it transfers the energy (heat) from the blood to the environment
* This means the blood returning to the core organs is at a lower temperature
100
**Explain** why the hairs on the surface of the skin are erect when the core body temperature is too low
* The erect hairs trap a layer of air underneath them
* This generates an insulation layer
* Which helps reduce energy transfer from the blood to the environment
* This means the temperature of the blood returning to the core organs is maintained (i.e. heat loss is prevented)
101
**Explain** why the hairs on the surface of the skin lie flat when the core body temperature is too high`
* The flattened hairs do not trap a layer of air underneath them
* This removes any insulation layer
* Which helps increase energy transfer from the blood to the environment
* This means the temperature of the blood returning to the core organs is lower
102
Label the diagram of the reflex arc
103
Label the diagram of a motor neurone
104
State the 7 charactersitics of living organisms
1. Movement
2. Respiration
3. Sensitvity - the ability to detect and respond to the environment
4. Growth
5. Reproduction
6. Excretion
7. Nutrition
105
Define the term 'sensitivity'
The ability to detect and respond to the environment
106
Explain what is meant by 'an involuntary action'
A response by an organism that requires no conscious thought
In these cases the stimulus always results in the same response i.e. the response is fixed
107
Define the term 'involuntary action' (2)
* It is an response that required no conscious thought i.e. it was automatic
* The stimulus will always produce the same response each time in an involuntary action
108
Name the two types of photoreceptor cell found in the retina and explain thier function
Cone cells - these detect the colour of the light
Rod cells - these detect the intensity of the light
