The Nervous System Flashcards
What does the nervous system enable humans to do?
Enables humans to react to their surroundings and coordinate their behavior
What is it made out of?
A network of nerves
What do nerves do?
Transmit electrical impulses between the brain, spinal cord, and the rest of the body.
What is the role of nerves?
to transmit electrical impulses
What is the CNS (central nervous system) made up of?
The brain and the spinal cord
What helps the CNS carry out its responses?
Coordinates responses via:
- receptors
- sensory neurones
- motor neurones
- effectors
What does the PERIPHERAL nervous system consist of?
Consists of neurones that travel to and from the CNS.
What is the peripheral nervous system’s role?
Connects the CNS to the body
What is a nerve?
A bundle of many neurones
What is a neurone?
An individual nerve cell
What do neurones do?
Neurones carry electrical impulses between receptors, the CNS and effectors
What do nerves do?
Nerves carry electrical impulses from the CNS to the rest of the body
What do receptors do?
detect change/ stimuli
What does the CNS do?
Coordinate a response
What do effectors do?
Carry out a response
What are effectors and why are they called that?
Often glands or muscles
Called that because they go into action when they recieve nerve impulses of hormones.
What are nerve impulses from sense organs to the CNS called?
sensory impulses
What are nerve impulses from the CNS to the effectors called?
motor impulses
How does the nervous system act as a COORDINATOR?
Acts as a coordinator by directing responses to stimuli such as changes in body conditions
How do sensory receptors help to coordinate a response?
Sensory receptors, located in sense organs, stimulate sensory neurones.
What do relay neurones do?
Relay neurones in CNS stimulate motor neurones
What are examples of responses that effectors can carry out?
- muscle contraction
- hormone secretion
What is the junction between 2 neurones called?
A synapse / synaptic cleft
How do electrical impulses pass between neurones?
When an electrical impulse reaches the end of the first neurone, it triggers the release of a chemical. This chemical is called NEUROTRANSIMITTER
How does the neurotransmitter travel?
Diffuses across the gap
Does the process of the electrical impulse travelling over the synapse slow down the speed of nerve impulses?
Yes
Do synapses control the direction of impulses? If so, how?
Yes
- neurotransmitter substances are synthesised on only one side of the nerve impulse, while receptor molecules are only present on one side
How does heroin interact with receptor molecules at synapses?
Stimulates receptor molecules in synapses in the brain, triggering the release of dopamine
How do spider toxin and the toxin released by tetanus affect the nervous system?
Breaks down vesicles, releasing mass amounts of transmitter substance and disrupting normal synaptic function.
What is a reflex?
A very fast, automatic response to a stimulus that does not involve direct coordination by the concious part of the brain. They are INVOLUNTARY.
What are reflexes coordinated by?
Reflex arcs
What does a reflex arc consist of?
Consists of an electrical impulse being directly transmitted from a sensory neuron, via a relay neuron, to a motor neuron, to stimulate a rapid response.
Why are reflexes so fast in bringing about a response?
This is because when the electrical impulse reaches the CNS, it often only passes through the spinal cord, and not the brain.
How is the brain informed that a reflex reaction has occured?
If the reflex signal does not initiialy pass through the brain, a seperate impulse can be sent from the spinal cord to the concious part of the brain.
Why are reflexes important?
Help protect the body from danger
What is reaction time?
Time taken for a response to occur in reaction to a stimulus
What are the 3 types of neurones?
Motor, Sensory, Relay
Where do motor neurones carry signals from and to?
From the CNS to effectors
Where do sensory neurones carry signals from and to?
From the receptors / sense organs to the CNS
Where do relay neurones carry signals from and to?
Connect motor and sensory neurones
Where are the cell bodies of the neurones mainly located?
brain or spinal cord
What types of neurones can a nerve contain?
A combination of sensory and motor nerve fibres (axons) in order to carry many different impulses
What is an impulse?
A series of electrical pulses which travel down the axon
At what speed does a nerve impulse travel?
100m/s -1
Are all nerve impulses similar?
Yes
What is a spinal reflex?
Examples
A reflex that uses relay neurones in the spine cord
- withdrawing the hand from a hot object
Examples of reflexes that take place in the head?
location: not coordinated by brain
Iris reflex
Blinking
Coughing
Synapse definition
A junction between 2 neurones
What is a volunatry action?
One which requires a concious decision by the brain
- Unlike a reflex action, it does not happen automatically
- choice in selection of the response
What is the main function of the brain during voluntary actions?
To coordinate the actions so that they happen in the right sequence and at the right time and place.
Definition of a sense organ?
Example
Sense organs are groups of sensory cells, responding to specific stimuli, such as light, sound, touch, temperature and chemicals.
e.g eye / ear
Definition of stimulus
A change in the enivronment (light, tempertaure, pressure) which produces a reaction in a living organism.
list 5 sense organs and the stimuli they respond to
- ear - sound, body movement (balance)
- eye - light
- nose - chemicals (smells)
- tongue - chemicals (taste)
- skin - temperature, pressure, touch, pain
What is the special property of sensory cells and organs?
They are able to convert one form of energy into another
e.g eyes can convert light energy into electrical energy (of nerve impulse)
Describe the reflex arc of coughing
STIMULUS - Particles making contact with the lining of the respiratory tree
RESPONSE - Violent contraction of the diaphragm and internal intercostal muscles
What is the survival value of coughing?
Prevents lungs being damaged or infected, so that gas exchange remains efficient
What is the survival value of the knee-jerk reflex?
The leg can support the body’s wait during walking
Describe the reflex arc of swallowing
STIMULUS - Food particles making contact with the back of the throat
RESPONSE - Contraction of the muscle of the epiglottis, which closes off the entrance to the trachea
What is the survival value of swallowing?
Prevents food entering the respiratory pathway so that lungs are not damaged
What does the white matter in the spine contain?
Contains the nerve fibres
What does the grey matter in the spine contain?
Contains cell bodies of the motor neurones
Can impulses travel both ways?
No
- synapses act as valves, forcing impulses to travel 1 way
What is intergration?
When the CNS processes information from receptors and passes instructions to effectors to tell the organism how to respond
What is a cranial reflex?
Reflexes that use the brain as a relay centre without conscious involvement.
Where do learned reflexes take place?
In the lower regions of the brain
How are learned reflexes activated?
need a stimulus from a higher region, but once started always lead to the same response
What is the system called that controls the reflexes which help keep a constant internal environment in the body ?
Examples of such reflexes
Autonomic nervous system
e.g breathing, heart beat, peristalsis
How can the brain communicate with the other parts of the body?
Via the spinal cord
definition of involuntary action
Does not involve any consious decision by the brain
- organism has no choice
- response automatically follows the stimulus
How are learned reflexes formed?
Each time a particular stimulus leads to a certain response, that impulse passes along the same route
e.g talking, cycling
What is a transducer?
Something which can convert one type of energy into another
- sense organs convert energy
What are the 4 types of receptors?
Photoreceptor - light
Chemoreceptor - chemicals
Thermoreceptor - changes in temp.
Mechanoreceptor - mechanical changes such as changes in length
Where can you find them?
p - rod cells in retina of eyes
c - taste buds
t - t in skin
m - hair cells in ear (hearing and balance)
What is a conditioned reflex?
Learned reflexes in which the final response has no natural relationship to the stimulus
Can conditioned reflexes be unlearnt? How?
Yes
- if the unnatural stimulus is not repeated with the natural one