B10 - The Human Nervous System Flashcards
1
Q
Define homeostasis (1 mark)
A
The regulation of conditions in our body maintaining a stable internal environment, for example: internal body temperature
2
Q
Why is homeostasis important? (2 marks)
A
It is important for maintaining optimal condition for enzyme action and all cell functions
3
Q
Give examples of homeostasis in the human body. (3 marks)
A
- When you exercise your muscles get hotter (more strained, more lactic acid production)
- when you have eaten a meal and your blood sugar levels go up (glucose levels increased)
- in hot weather you lose water through sweating (perspiration)
4
Q
Describe homeostasis (3 marks)
A
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for functions, in response to internal and external changes. For instance; when internal body temperature is normal or slightly elevated, the enzymes are optimised and functions in the body are increased in speed.
5
Q
Why is it important to respond to changes in the internal or external environment? (2 marks)
A
It is important to respond to these environmental changes as it helps maintain the body’s optimum conditions for the cellular enzymes and its activities.
6
Q
What internal conditions can be controlled? (3 marks)
A
- body temperature
- the water content of the body
- blood glucose concentration
7
Q
What does the automatic control system involve? (2 marks)
A
They involve either NERVOUS or CHEMICAL responses
8
Q
What are receptors (1 marks)
A
Cells that detect stimuli - changes in the internal or external environment. They then send electrical impulses to the neurons to react to.
9
Q
Describe a receptor (3 marks)
A
Cells that detect changes in the external or internal environment. These changes are known as stimuli. Receptors may be part of the nervous or the hormonal control systems of the body and is responsible for the emitting of electrical impulses to the neurons or CNS (brain, spinal cord, etc.)
10
Q
What are coordination centres - CNS (1 mark)
A
Areas that recieve and process information from receptors (e.g. brain - CNS)
11
Q
Describe coordination centres - CNS (3 marks)
A
They are areas that recieve and process the information from the receptors. They send out signals (electrical impulses) and coordinate a response from the body (via. neurons). They include the brain (CNS) that acts as a coordinate centre for both the nervous system and parts of the hormonal system, the spinal cord (CNS), pancreas and some other organs.
12
Q
What are effectors? (1 mark)
A
Areas (usually muscles or glands) that bring about responses in the body
13
Q
Describe effectors (3 marks)
A
Muscles or glands that bring about responses (via. neurons) to the stimulus that have been recieved (via. receptors). These responses restore conditions in the body to the optimum levels.
14
Q
Define stimuli/us
A
Changes in the external or internal environment that can be detected by receptors.
15
Q
Name the different types of sense receptors (5 marks)
A
- ears
- eyes
- skin
- nose
- tongue
16
Q
Give one example of what the different types of sense receptors respond to (5 marks)
A
- Ears receptors are sensitive to changes in position for balance and sensitive to sound.
- Eyes receptors are sensitive to light and darkness
- Skin receptors are sensitive to touch, pressure, pain and temperature changes.
- Nose and tongue receptors respond to chemicals for smell and taste.
17
Q
Define a nerve (1 mark)
A
Bundle of hundreds or even thousands of neurons/ones
18
Q
Define a neurone (1 mark)
A
Basic cells of the nervous system that carry electrical impulses around the body
19
Q
What are the types of neurones (3 marks)
A
- sensory neurons
- motor neurons
- relay neurons
20
Q
Describe a nerve and each neurone (5 marks)
A
Nerves carry electrical impulses around the body that passes along special cells called neurones. There are two main types of neurons: SENSORY neurons - which are the cells that carry impulses from your sense organs to your CNS, and the other type are MOTOR neurons - they carry information from your CNS to the rest of your body by electrical impulses to make the right bits of your body.
21
Q
What may an effector be (2 marks)
A
Effectors may be muscles or glands
22
Q
Describe two examples of effectors (4 marks)
A
- Muscles, as your muscles respond to the arrival of impulses by contracting.
- Glands, your glands respond by releasing (secreting) chemical substances.
23
Q
Define the nervous system (1 mark)
A
The nervous system consists of the CNS - the brain and the spinal cord.
24
Q
Explain the nervous system (2 marks)
A
Carries electrical impulses so you can react quickly to changes in your surroundings
25
Why do you need a nervous system (2 marks)
The nervous system uses electrical signals to communicate with different parts of the body, without this your body internally and externally will not be able to react to changes in your surrounding, placing you at a fatal risk of danger.
26
What is the order to which the nervous system works (4 marks)
Stimulus (light) ---> Receptor (eyes) ---> Coordinator (CNS) ---> Effector (for eg. muscle) --> Response.
27
Explain what happens to your nervous system from stimuli to effector (5 marks)
The receptor sends an electrical impulse along a SENSORY neuron, carrying information about a change in the environment to the coordinator (CNS). Once all the incoming information has been processed, the coordinator send impulses down, via. MOTOR neurones. These MOTOR impulses stimulate the effectors to bring about responses needed in any particular situation.
28
Explain what happens to your nervous system, when you see a piece of fruit, pick it up and eat it. (6 marks)
Light from the piece of fruit is detected by the sensory receptors in the eyes (via. Refraction), then an electrical impulse travels along the SENSORY neuron to the brain (CNS) - where information is processed in the brain and another electrical impulse is sent along a MOTOR neuron to the muscles of the arm and hand (the EFFECTOR) so you can pick up the piece of fruit and then put it in your mouth. The taste receptors sensitive to chemicals for smell and taste on your tongue send information to the brain (CNS) about taste.
29
Give two methods of how quickly nerve impulses travel in your body (4 marks)
1. Use a ruler drop test or digital sensors to measure how quickly you react to visual stimulus.
2. Stand in a circle holding hands with your eyes closed and measure how long it takes a hand-squeeze to pass around the circle.
30
What are reflexes? (1 marks)
Ralid and automatic responses of the nervous system that do not involve conscious parts of the brain (CNS).
31
Name a couple examples of human reflexes (2 marks)
They control everyday bodily functions, such as: breathing and digestion, and help to avoid dangerous situations.
32
Wh are reflexes important? (2 marks)
They help you to avoid danger or harm because they happen so fast
33
Why is it important that reflexes dont go to the conscious areas of your brain? (1 mark)
Which makes it quicker to react and therefore reduces damage to the body
34
Define a sensory neuron
A sensory neuron is a neuron that carries electrical impulses from the sensory organs to the central nervous system (CNS)
35
Define a motor neurone (1 mark)
Motor neurones carry impulses from the central nervous system (CNS) to the effector organs
36
Define a relay neurone (1 mark)
Relay neurons connect a sensory neurone and a motor neurone, and are found in the CNS
37
How do reflexes work? (4 marks)
An electrical impulse passes from the receptor along the SENSORY neuron to the CNS. It then passes along a RELAY neurone (usually in the spinal cord - CNS) and straight back along the MOTOR neurone. From there, the electrical impulse arrives at the EFFECTOR organ. The EFFECTOR organ will be a muscle or a gland. This pathway is called a reflex ark.
38
SEE SHOWBIE FOR REFERENCE:
How do synapses work? Make sure you can label a synapse (3 marks)
When an electrical impulse arrives at the junction between two neurones (pre-synaptic and post-synaptic) - neurotransmitter chemicals are released that cross the synapse and arrive at receptor sites on the next neurone. This starts up a new electrical impulse in the next neurone.
Key terms for synapse processes:
- axons
- post-synaptic neuron
- pre-synaptic neuron
- synapse
- dendrites
- receptors
- synaptic vesicles
- neurotransmitters
- diffusion across synapse
39
Explain why some actions (unconscious), such as: breathing and swallowing are reflex actions, while others such as: speaking and eating are under your conscious control. (4 marks)
Reflex actions such as breathing and swallowing need to operate automatically even when sleeping, otherwise it could be fatal as if you forgot to breathe, it would stop the flow of oxygen inside your lungs and carbon dioxide out of them. As these actions are so vital to humans' life processes, the brain adapts to these actions and allows it to occur without it hindering the brain, thus making it an unconscious action/reflex. However, other actions/reflexes, such as; speaking and eating - require you to choose when to do them - consequently making it an conscious action or decision.
40
Describe what happens when you step on a pin. Make sure to indicate when an electrical impulse or chemical impulse is involved. (6 marks)
When you accidentally step on a pin, a sequence of events takes place in your body. First, the mechanical pressure from your foot compresses the pin against the sole of your foot. This pressure causes your sensory neurons to send electrical impulses to your brain (CNS), signaling pain and discomfort. The brain processes this information and simultaneously, your body releases chemical signals, like neurotransmitters, at the site of injury, which play a role in increasing the pain signals and triggering an inflammatory response. This combination of electrical and chemical impulses works like a warning mechanism, alerting you to the potential harm and prompting a quick reflex to remove your foot from the pin.
41
Describe what the brain is made up of (3 marks)
It is made up of billions of interconnected neurones that control complex behaviour
42
Explain the importance of the brain (3 marks)
Your brain controls everything from walking to complex behaviour, as well as, your thoughts and feelings.
43
Name 3 parts of the brain (3 marks)
- cerebral cortex
- cerebellum
- medulla
44
Explain the functions of the cerebral cortex, the cerebellum and the medulla. (6 marks)
1. Cerebral cortex - it is responsible for our memory, consciousness, language and intelligence.
2. Cerebellum - it is responsible for the coordination of muscular activity, etc.
3. Medulla - it is responsible for unconscious activities/reflexes, for instance; heartbeats and breathing.
45
Describe two ways in which scientists can find out about the functions of the different areas of the braim (6 marks)
- Scientists fit together regions of the brain to their functions by studying patients with brain damage, this may be done by electronically stimulating different areas of the brain, as welll as, using MRI scanning techniques.
- They can remove the top of the skull and stimulate different parts of the brain to see what effect this has.
- People can experience hunger, anger, fear or thirst, simply becuase the relevant area of the brain is stimulated.
- In addition to this, if someone develops a stroke or tumour in the brain, a magnetic resonance imaging machine (MRI) can show exactly which areas are affected.
- For instance, scientist can link speech or movement of one side of the body to a damaged part of the brain.
46
Describe the benefits and risks of stimulating areas of the brain and carrying out MRI scans on the brain of healthy people. (6 marks)
- A benefit of stimulating different areas of the brain, is that a scientist can stimulate different areas and see what effect this has.
- Another benefit is to see how people experience hunger, anger, fear or thirst differently, simply because the relevant area is stimulated on the brain.
- A benefit of MRI Scans, scientists and doctors have been able to develop their understanding of how the brain works, as a result of new ways of taking images of the brain in healthy, living people.
- However, the risk is that the brain is very delicate, therefore using scientific instruments to experiment on it can be dangerous.
- The brain is easily damged and destroyed especially when left exposed.
- Furthermore, since its difficult to understand what each part of the brain does, its easy to cause unintended damage.
47
Explain the functions of the hypothalamus and pituitary gland (2 marks)
1. The hypothalamus - homeostasis
2. The pituitary gland - produces hormones (for eg. Leutinising Hormone -LH and Follicle Stimulating Hormone - FSH) which control and coordinate the body
48
What is the protective membrane covering the brain (1 mark)
Meninges
49
Name examples of different parts of the brain. (5 marks)
- Cerebral cortex
- Cerebellum
- Hypothalamus
- Medulla
- Pituitary gland
50
What does MRI stand for?
Magnetic Resonance Imaging
51
What is the eye? (2 marks)
A sense organ containing a variety of receptors that are sensitive to light sensitivity and colour. Humans see images because light gets refracted and creates an image. With no light, humans can’t see.
52
Name the main parts of the eye (9 marks)
- Cornea
- Pupil
- Iris
- Ciliary muscles
- Suspensory ligaments
- Lens
- Optic nerve
- Retina
- Scelera
53
Explain and describe the function of the tough outer sclera (2 marks)
The scelera is a tough, white outer layer/tissue that helps maintain the shape of the eye and protect the eye from injury.
54
What is the function of the cornea. (2 marks)
The cornea is the transparent, protective layer at the front of the eye that lets light in and refracts (changes the direction of) light towards the retina to create an image. Similarly, the cornea cannot let the retina create an image for us to see if there is no light.
55
Explain and describe the function of the muscular iris (2 marks)
Controls the size of the pupil and the amount of light entering the eye.
56
Explain and describe the function of the lens. (2 marks)
The lens of the eye is a transparent convex disc that can change shape to focus light being refracted onto the retina.
57
Explain and describe the role of the retina in the eye. (2 marks)
The retina is a layer of cells at the back of the eye that contains photoreceptors that detect light and send signals to the brain through the optic nerve. The retina plays a crucial role in our ability to see by converting the light that enters the eye into electrical signals that the brain can understand.
58
Explain and describe the role of the optic nerve. (2 marks)
The optic nerve gets sent an elecrical impulse, via. The retina's photoreceptors and then sends that electrical impulse to the brain (CNS), via. Sensory neurons.
59
Explain and describe the role of the ciliary muscles. (2 marks)
The ciliary muscles contract or loosen to help change the shape of the lens. When the ciliary muscle relaxes, its diameter. becomes wider; the suspensory ligaments tighten and pull the lens thinner.
60
Explain and describe the role of the suspensory ligaments. (2 marks)
The suspensory ligaments help keep the lens in place and stop it from moving around/shifting too much. In addition to this, they connect to the ciliary muscles to help focus on objects from different distances.
61
What is the blind spot of the eye? (1 mark)
The point where the optic nerve leaves the eye - has no retina so there is a blind spot.
62
Accomodation of the eye:
What happens to the lens of the eyes when 'Near focusing' and 'Distance focusing'.
- Near focusing:
The lens thickens as the suspensory ligaments loosen.
- Distance focusing:
The lens thin as the suspensory ligaments tense
63
Accomodation of the eye:
What happens to the suspensory ligaments of the eyes when 'Near focusing' and 'Distance focusing'.
- Near focusing:
The suspensory ligaments loosen due to the ciliary muscles contracting
- Distance focusing:
The suspensory ligaments become more tense due to the ciliary muscles relaxing/loosened.
64
Accomodation of the eye:
What happens to the ciliary muscle of the eyes when 'Near focusing' and 'Distance focusing'.
- Near focusing:
The ciliary muscle contract in order to loosen the ligaments, to then allow the lens to thicken. As a result, we can see objects from nearer distances.
- Distance focusing:
The ciliary muscle relax as it allows the suspensory ligaments to become more tense, this leads to the lens becoming thin and allowing the eye to see from further distances.
65
Explain why your pupil is more open in dim light than in bright light. (3 marks)
Because the eye is under the conditions of dim lighting, the pupil is enlarged (via. the iris), so as much light as possible, enters the eye. Whilst in bright light, the iris makes the pupil very small, which reduces the amount of light entering the eye, as too much light can be harmful to the eye.
66
Describe how a light ray that enters the eye is translated into a visual image in the brain (6 marks)
When you focus on something e.g an object - light reflects off that object passing through the cornea and lens which focus it on the retina. The retina converts the image formed into nerve pulses which get sent to the brain. The optic nerve then transmits these impulses from the eye to the first visual relay in the brain.
67
Define accomodation (1 mark)
The process of changing the shape of the lens of the eye to focus on near or distant objects.
68
Name two common eye defects that affect people of age. (2 marks)
- Myopia: short-sightedness
- Hyperopia: long-sightedness
69
Name four technologies to treat slight defects in the eye (4 marks)
- Contact Lenses
- Laser Eye Procedure/surgery (LASIK)
- Replacement lenses
- Glasses
70
Compare myopia and hyperopia (4 marks)
With Myopia you can see objects in clear focus, but distant objects look blurred. This is because light is focused in the front of the retina, so the images that actually land on the retina are out of focus and blurry.
Whilst with Hyperopia you can focus clearly on distant objects but close objects appear blurred. This may be a result of a lens that is too flat and thin or a particularly short eyeball.
71
READ ONLY:
Explain and compare the advantages/disadvantages of three new eye technologies (12 marks)
Contact lenses, lenses placed on the surface of the eye and they do the same job as glasses but cannot be seen. Hard contact lenses are made of relatively rigid material and therefore as an advantage can last a long time but as a disadvantage, they have to be removed at overnight and kept sterile to prevent eye infections. Most modern contact lenses are soft lenses and therefore as an advantage are more comfortable but they do not last long, some soft lenses can be worn every day for a month but like hard lenses have to be kept in sterile solution overnight, another disadvantage. There are disposable ones that get thrown away after a day.
Laser eye surgery, only available for adults once their eye stops growing which is a disadvantage because if your eyesight is really bad at a young age it will take a very long time to get such treatment. Lasers are used to treat myopia by reducing the thickness of the cornea so it refracts the light less strongly, an advantage. To treat hyperopia, lasers are used to change the curve of the cornea so it refracts light from close objects more effectively, an advantage.
Replacement lenses, Corrects visual defect permanently, an advantage, by adding another lens inside the eye itself. Two main techniques. In one a permanent contact lens is implanted into the eye and the natural lens is left in place. In the other, the faulty lens is replaced by an artificial lens. As a disadvantage the risk of lens replacement is damage to the retina, cataracts developing if the natural lens remains in place. infections.
72
How are nerve cells adapted for their function? (3 marks)
● The axon is long, enabling the impulses to be carried along long distances
● Having lots of extensions from the cell body (called dendrites) means branched connections can form with other nerve cells
● The nerve endings have many mitochondria which supply the energy to make special transmitter chemicals called neurotransmitters. These allow the impulse to be passed from one cell to another.
73
What does bright light cause in the eye? (3 marks)
- Cilliary muscles contract
- suspensory ligaments relax
- Pupil constricts
74
What does dim light cause in the eye? (3 marks)
- ciliary muscles relax
- suspensory ligaments contract
- Pupil dilates
75
What does a comcave lens do?
Diverges light rays for short-sightedness (myopia)
76
What does a convex lens do?
Converges light rays for long-sightedness (hyperopia)
77
What is the pathway of a nerve impulse (conscious action)? (7 marks)
1. A stimulus is detected by receptors in a sense organ, e.g. the eyes.
2. The stimulus is converted to an electrical impulse by the receptor.
3. The electrical impulse travels along a sensory neuron to the brain (CNS)
4. The brain decides the correct response that is required. The electrical impulse is then passed to a relay neuron in the brain.
5. The relay neuron passes the electrical impulse to a motor neuron.
6. The electrical impulse travels along the motor neuron to the effector, e.g. a muscle.
7. The effector carries out the response.
78
How does an electrical impulse cross the synapse? (6 marks)
1. The electrical impulse reaches the end of the pre-synaptic neuron.
2. This stimulates the release of neurotransmitter chemicals from vesicles
3. The neruotransmitter chemicals diffuse across the gap called the synapse
4. The neurotransmitter chemicals bind to specific receptors on the post-synaptic neuron.
5. This binding triggers the generation of an electrical impulse (same message) in the post-synaptic neuron and it travels along it's axon.
6. The neurotransmitter chemical then diffuse back into the vesicles and are recycled.
5
79
How does eye glasses and contact lenses work? (2 marks)
They work by concentrating the light rays at the retina - focus point, allowing the eyes to recognise the stimulus and send an electrical impulse to the CNS.
80
Reasons for people being short-sighted (myopia). (3 marks)
- Large shape of eyeball
- Concave shape of lens
- Focal point is before
81
Reasons for being long-sighted (hyperopia). (3 marks)
- Small shape of eyeball
- Convex shape of lens
- Focal point is after
82
What are two types of lens for correcting vision?
- Convex: for long-sightedness (hyperopia)
- Concave: for short-sightedness (myopia)
83
What are the 2 automatic control systems of the body? (2 marks)
1) Nervous system
2) Endocrine system
84
The nervous system is made up of 2 parts. What are these 2 parts? (2 marks)
- The central nervous system (CNS - brain and spinal cord)
- The peripheral nervous system (PNS - all other nerve cells)
85
Describe how a neuron is adapted for it's function. (4 marks)
• Thin projections called dendrites extend from the cell body and connect with other neurones, allowing electrical impulses to pass from one to the other.
• The axons of most neurones are insulated by a layer called the myelin sheath. This ensure the impulses travel rapidly along the axon.
86
What happens if the myelin sheath degenerates? (1 mark)
The electrical impulse can not travel as smoothly down the axon. The person may experience tremors.
87
Why are reflex actions important to humans. (3 marks)
• Fast
• Automatic
• Protective responses
88
Why is the brain not involved (initially) in a reflex repsonse? (1 mark)
It would take too long and the person may be harmed
89
Which part of the CNS controls reflex responses?
The spinal cord
90
SEE SHOWBIE FOR REFERENCE:
Structure/labels of a motor neuron. (7 marks)
- axon terminal
- nucleus
- cell body
- myelin sheath
- axon
- dendrites
- sensory organ cell (effector)
91
SEE SHOWBIE FOR REFERENCE:
Structure/labels of a sensory neuron. (7 marks)
- Sense organ cells (effector)
- dendrites
- nucleus
- cell body
- myelin sheath
- axon
- axon terminal
92
How many nerves are there in the average human body? (1 mark)
It is said that there is approximately 7 trillion nerves in the average human body.
