Content - Central Nervous System Flashcards
What do Bio-psychologists assume that behaviour is caused by?
experiences in the nervous system
Define the nervous system
a specialised network of cells in the human body and is our primary internal communication system
Name the 2 main functions of the CNS (2)
1) To collect, process and respond to information in the environment.
2) To co-ordinate the working of different organs and cells
Define the CNS
made up of the brain and spinal cord and is the origin of all complex commands and decisions
Name 3 facts about the brain (3)
- This is the centre of all conscious awareness.
- The brain’s outer layer, the cerebral cortex, is highly developed in humans.
- The brain is divided into two hemispheres
Name 3 facts about the spinal chord (3)
- The spinal cord is an extension of the brain.
- One thing it is responsible for is reflex actions such as pulling your hand away from a hot plate.
- Passes messages to and from the brain and connects nerves to the PNS.
Define the Peripheral Nervous System
The PNS transmits messages via millions of neurons (nerve cells), to and from the central
nervous system
What’s the PNS further subdivided into? (2)
- the somatic nervous system (SNS)
2. the autonomic nervous system (ANS)
Define the somatic nervous system
This is the part of the PNS that is responsible for
carrying sensory and motor information to and from the spinal cord. It is involved in skeletal muscle contraction
Define the autonomic nervous system
This governs vital functions in the body such as
breathing, heart rate, digestion, sexual arousal
and stress responses
Name the 2 main divisions of the ANS (2)
- The sympathetic nervous system (SNS)
2. The parasympathetic nervous system (PNS)
What do the SNS and PNS control?
Fight of flight response
What happens to your gut?
Digestion slows/increases
What happens to the salivary glands?
Saliva production inhibits/increases
What happens to the heart?
Heart rate increases/decreases
What happens to the liver?
Glucose production stimulated/bile production stimulated
What happens to the bladder?
Urination stimulated/inhibits
What happens to the eye?
Pupils dilate/constrict
What happens to the lungs?
Bronchi dilates/constricts
What’s another name for nerve cells?
Neurons
Define neurons
a unit of nervous tissue
How many neurons are in the nervous system?
100 billion
What percentage of neurons are located in the brain?
80%
How do neurons allow the nervous system to communicate by?
transmitting an electro-chemical signal (i.e. part of it is electrical and part of it is chemical)
Define cell body?
Contains the nucleus (DNA) and mitochondria (provides energy).
Define dendrite
Branches on the cell body of each neuron that receive information from neighbouring neurons to trigger an action potential
Define axon hillock
Where the nerve impulse is triggered from
Define axon
A tube-like structure; carries impulses away from the cell body down the length of the neuron
Define myelin sheath
Layers of fatty deposits that provide insulation for protection and help speed up the rate of message transmission. Formed from
special cells called glial cells
Define axon terminal
End of the axon, separated from other neurons by a tiny gap (known as the synapse)
Define neurotransmitter
Chemical messengers that act between the neurons
Define node of ranvier
Gaps in the myelin sheath that force the impulse to ‘jump’ across the gaps along the axon, to help speed up the impulse
Define nerve impulse
Within a neuron, an electrical message is sent through it
How does the nerve impulse travel
from the dendrites towards the axon terminal buttons
What’s the gap called between neurons
Synaptic gap/synaptic cleft
What’s between synaptic gaps?
neurotransmitters
Name 3 types of neuron (3)
- Sensory neurons
- Motor neurons
- Relay neurons
Define sensory neurons
these carry messages to the CNS from sensory receptors (e.g. in the skin) along nerves in the peripheral nervous system
Define motor neurons
these carry messages from the CNS along nerves in the peripheral nervous system, to ‘effectors’ in the body such as muscles and glands
Define relay neurons
these connect sensory and motor neurons together, and also connect to other relay neurons. They are only found in the CNS, with many being in the spinal cord
Define neurotransmission
what gets a signal (or a message) from one neuron to another
Name 2 things neurotransmission involves (2)
- An action potential
2. Synaptic transmission
Define action potential
an electrical message being transmitted within the neuron
Define synaptic transmission
a chemical message being passed between neurons, from one to another
What happens when the action potential reaches the terminal buttons?
will cause the vesicles to release neurotransmitters into the synapse
What resting potential do neurons have?
-70mV
How is the action potential transmitted? (5)
- When a neuron receives a message from another, the
chemical message results in either excitation or inhibition of the postsynaptic neuron. - Excitation means it will slightly depolarise the neuron, increasing its charge (becomes more positive).
- Inhibition means it will hyperpolarise the neuron
decreasing its charge and stimulating an inhibitory
postsynaptic potential. - When a neuron has received enough excitatory
messages (usually when the charge has reached the
threshold of -55mV), an action potential is triggered in the postsynaptic neuron. - The action potential sends an impulse along the axon of
the neuron towards the axon terminal
What does the all or nothing principle suggest?
that the threshold of -55mv must be reached in order for an action potential to fire
Define synaptic transmission
the process by which neighbouring neurons communicate with each other by sending chemical messages across the tiny gap (the synapse) that separates neurons
How does synaptic transmission take place?
- An action potential (electrical impulse) reaches the axon terminal (terminal buttons)
- Following this electrical impulse, calcium ions (Ca2+) flow into the neuron through calcium ion channels on the pre-synaptic neuron’s membrane
- The Ca2+ ions coming in through the ion channels cause the vesicles in
the terminal buttons to migrate to the cell membrane and release neurotransmitter into the synapse - The neurotransmitter travels through the synapses/synaptic cleft and
binds to receptors on the post-synaptic neuron - Depending on which receptor type the neurotransmitter binds to or how many of the correct receptors it binds to, the result is usually either
excitation or inhibition of the post-synaptic neuron (Excitation = causes
an electrical impulse; inhibition = does not cause an electrical impulse) - Neurotransmitter molecules in the synaptic cleft are then either deactivated by reuptake (taken back up into the pre-synaptic neuron via
transporter proteins) or they are degraded by enzymes in the synaptic cleft.
What are neurotransmitters?
Chemical messengers that transmit information across a synapse from one neuron to another
Name 2 causes and effects of changing neurotransmitter levels (2)
- Low levels of serotonin can lead to depression
2. High levels of dopamine can live to schizophrenia
Name 2 examples of neurotransmitter levels being affected by things we consume and do (2)
- Chocolate increases level of endorphines in the brain (affects dopamine)
- Cocaine increases levels of dopamine
Describe the function of aletylcholine (3)
- Stimulates muscle contractions and has a key function in motor control
and movement. - Also necessary for memory and other cognitive functions such as attention and alertness/wakefulness.
- Also involved in expressions of some emotions such as anger and sexuality
Describe the function of noadrenaline
Associated with emotion. Involved in sleeping, dreaming and learning.
Describe the function of dopamine (3)
- Similar function to noradrenaline. Related to emotion and cognitive
function, posture and control of movement. - Associated with
reinforcement in learning as well as dependency such as addictions. - Also used in hormonal regulation such as control of the menstrual cycle
Describe the function of serotonin (2)
- Most commonly associated with mood control.
- Also involved in functions such as feeling pain, sleep,
regulating body temperature and hunger
Name the 4 key neurotransmitters (4)
- Aletylcholine
- Noadrenaline
- Dopamine
- Sortonin
Describe the Jovanovic supporting study
(using PET scanning) found differences in the synaptic receptors related to serotonin of women with pre-menstrual dysphoric disorder
Link the Jovanovic study back to A01
This supports the role of neurotransmitters in behaviour because we know that serotonin is most commonly associated with mood which would explain the feelings of sadness
Describe the McNeal & Cimbolic (1986) supporting study
found that people with depression have a lower level of 5-H1AA (formed when serotonin is broken down), suggesting that there must be lower levels of serotonin in their brains
Link the McNeal & Cimbolic (1986) back to A01
This supports the role of neurotransmitters in behaviour because we know that serotonin plays a role in mood control which would explain why decreased levels could cause disorders such as depression
Describe the Martinez & Kesner (1991) supporting study
investigated the effects of acetylcholine on rats’ ability to remember their way through a maze. It was found that the rats injected with chemicals affecting reception, degrading and/or reuptake of acetylcholine made more wrong turns in the maze than a control group of rats that were in their natural state
Link the Martinez & Kesner (1991) back to A01
This experiment therefore
demonstrates the significant influence of synaptic transmission and, more specifically, acetylcholine on memory. Acetylcholine is necessary for a range if cognitive functions such as memory and attention explaining the rats ability to remember
Describe the Allen and Stevens contradicting study
Allen & Stevens found that less than half the NT in transmission in the hippocampus arriving from the pre-synaptic neuron were picked up by the postsynaptic neuron
Link the Allen and Stevens study back to A01
This goes against what goes on during synaptic transmission because this process is characterised by the binding of many NTS receptors like a lock and key but this study suggests that there may be other factors responsible for behaviour if only few NTS bind
Describe the Martinez & Kesner contradicting study
As in the study by Martinez and Kesner (1991), much research is done on animals
Link the Martinez and Kesner contradicting study back to A01
Therefore, we can’t easily generalise findings to humans because the CNS and neurotransmission in humans is more complex
Describe another theory which shows that neurotransmission is not the only thing found to be linked to certain behaviour
Social learning theory suggests that we actually learn new behaviours through the imitation of role models and reinforcement/punishment
Link the other theory back to A01
Therefore to say that it is just electrical and chemical messages within and between neurons is not fully accurate
Describe how neurotransmission is useful?
Drug treatments have been developed such as antidepressants and antipsychotics, to enable those with faulty neurotransmitters and therefore mental illness (such as depression and schizophrenia) to function in society better
Link the usefulness of neurotransmission back to A01
Therefore it is useful that we know that serotonic levels can affect mood and dopamine can affect the development of schizophrenia as these explanations have paved the way for treatments. People less likely to blame themselves for their illness and seek help
Describe how neurotransmission is reductionist
More objective/easier to measure cause and effect because of the component parts this explanation of behaviour is simplified to
Give an example of neurotransmission reductionism
For example noradrenaline affects behaviour like sleeping and dreaming
Describe how neurotransmission is not reductionist
lots of other important factors that play a role in behaviour are ignored
Link the non-reductionist view to A01
To get a better understanding of human behaviour, these other factors must be considered alongside what we already know about the affects of NTS (eg dopamine) on behaviours such as addiction
