B3.1 and B3.3 (Test 1- Monday 26th April) Flashcards
What are the 2 parts of the Nervous System and their functions?
-Central Nervous System (CNS)- controls most functions in the body and mind (brain and spinal cord).
-Peripheral Nervous System (PNS)- this includes nerves leading to & from the brain and spinal cord.
Primary role of the PNS is to connect the CNS to the organs, limbs, and skin.
What are neurones?
Neurones are a particular type of cell (nerve cell) that carry information messages or signals to and from the brain and the rest of the body.
Groups of neurones are called nerves.
They are specialised for transmitting messages in the form of an electrical impulse.
Why do neurones have an extended shape?
Neurones have an extended shape so that they can carry nerve impulses from one part of the body to another.
It’s designed that way by the neurone to slow down the action potential of signals in order to optimise the refraction ratio.
Describe a motor neurone:
A motor neurone is a type of nerve cell whose cell body is located in the motor cortex, brainstem or the spinal cord
-And whose axon projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles (contract) and glands (secrete).
A motor neurone contains:
-dendrites, nucleus, cell body, myelin sheath, axon, motor end plate.
Describe a sensory neurone:
- Sensory neurones are nerve cells within the nervous system responsible for converting external stimuli from the organism’s environment into internal electrical impulses.
- For example, some sensory neurones respond to tactile stimuli and can activate motor neurones in order to achieve muscle contraction.
Sensory neurones contain:
-pressure receptor, myelin sheath, axon, cell body, dendrites.
Describe a relay neurone:
- Relay neurones are found between sensory input and motor output/response.
- Relay neurones are found in the brain and spinal cord (CNS) and allow sensory and motor neurones to communicate.
Relay neurone contains:
-dendrites, cell body, axon, synaptic endings.
What is the function of the axon?
The axon allows neurones to transmit electrical and chemical signals to other cells.
-It is where the electrical impulse travels down.
What is the function of the myelin sheath?
-The myelin sheath is a white, fatty substance (protein and fatty substances) that prevents leakage of electrical impulses through insulation.
What is the function of dendrites?
- The dendrites connect to other neurones to make a new nerve pathway.
- They contain lots of mitochondria- create lots of ATP.
What is the function of the motor end plate?
The motor end plate connect to muscles (contract) or glands (secrete).
Describe the nerve pathway:
(Top to bottom- nerve pathway):
Stimulus (change in environment)
|
Receptor (5 senses)
|
(Sensory neurone)
|
(relay neurone)
|
CNS (brain/spinal cord- co-ordinate response)
|
(motor neurone)
|
Effector (muscle or gland)
|
Response.What is a reflex action?
-A reflex action is an automatic, fast, involuntary reaction
-You do NOT have any control over these actions.
-They are survival responses.
-They can bypass the brain
-They take the shortest route- from receptor->effector.
=Reflex Arc.
Name some reflex actions:
- pupil constriction
- knee jerk
- startle reflex (babies)
- stepping reflex (babies)
Explain the pathway taken by a reflex arc (example of a reflex action):
1) A stimulus is a change in the environment of an organism.
2) This is detected by a receptor, such as the eye.
2) Impulses from a receptor pass along a sensory neurone to the CNS (the co-ordinator)
3) A chemical crosses the gap (synapse) between a sensory neurone and a relay neurone.
4) Then a chemical crosses the synapse between a relay neurone and a motor neurone.
5) The motor neurone carries an impulse to an effector which can be a muscle or a gland.
6) The muscle responds by contracting and a gland responds by releasing chemical substances.
What is a synapse?
- A synapse is where 2 or more neurones meet,
- There is a small gap around 2-3 micrometres big
- Signals cross the gap using chemical released by a neurone.
- This chemical is called a neurotransmitter (NT) (electrolyte charged) (this can be sodium ions, but there are many different types of NT that diffuse across the synapse.)
- The gap between the two neurones can also be called the synaptic cleft.
- The electric signal that travels through the axon in the neurone comes in contact with the end of the neurone and the signal is temporarily converted into chemical energy (chemical transmitter molecules).
- These chemical transmitter molecules diffuse across the synaptic cleft.
- Then, the chemical transmitted molecules bind to receptors on the other neurone, which opens the channels, allowing the chemical energy to be re-converted into electrical energy/signal.
- The nerve impulse is then initiated in the next neurone
- This repeats until the effector is reached.
What is the function of the brain?
- The brain coordinates responses to changes in the internal conditions and the environment.
- The brain and spinal cord form the CNS which process information that comes from body via neurones.
- CNS receives electrical signals from neurones that are stimulated by change in both internal and external environment.
- It sends out electrical signals along other neurones to bring about a suitable response.
What is the function of the cerebrum:
This is the largest part of the brain
It is responsible for things like consciousness, intelligence, memory and language.
What is the function of the Hypothalamus?
-The hypothalamus is involved in maintaining body temperature at the normal level.
It also produces hormones that control the pituitary gland.
What is the function of the pituitary gland?
The pituitary gland produces many important hormones, such as those involved in the menstrual cycle.
What is the function of the medulla?
The medulla controls unconscious activities like breathing and heart rate.
What is the function of the cerebellum?
The cerebellum is responsible for muscle coordination.
Describe a non-intrusive technique to investigate the brain’s function?
- Neuroscientists can use electrodes to stimulate different parts of the brain.
- By observing the resulting behaviour, it is possible to work out the function of the region stimulated.
- Observations that may be recorded include a change in emotion, sudden movement or an increase in heart rate,
Describe the uses of an MRI scan:
- MRI scan uses strong magnets and radio waves to produce detailed images of the inside of the brain/body.
- Most common use is: anatomical structure.
- Used to identify presence of tumours or haemorrhages.
Describe the uses of a PET scan:
PET scanning produces detailed 3D images that can be used to investigate brain’s activity.
A substance that emits radiation is injected into the patients bloodstream.
In the scanner, radiation can be detected as it collects in different parts of the body, including the brain.
-During PET scan, patient is asked to perform tasks.
-Depending on tasks, different images are produced.
Describe the uses of CT scan:
-A CT scan uses x-rays + special computer technology to produce images of ‘slices’ showing inside the body.
Bone absorbs x-rays well; soft tissues don’t.
Different tissues absorb different level of x-ray, so you get different shades (greyscale).
ONLY shows brain’s anatomical structure.
Describe some difficulties of investigating the brain’s function:
- If a person is severely brain damaged, it may be unethical to study them as they might not be able to give informed consent.
- Studying the brains of people who have died relies on people donating their brains for research- not many people are willing to do this.
- There can be difficulty reaching some areas of the brain during operations.
- Difficulty in obtaining volunteers.
- Operations may cause irreversible damage- nerve tissue cannot heal and nerve cells cannot be re-made.
- Placebo effect.
