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whats the purpose of the nervous system
it detects and responds to changes inside and outside of the body. co-ordinates and controls vital body functions and maintains homeostasis
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what two systems fall under the nervous system
- the central - brain and spinal cord
- the peripheral nervous system - all nerves outside the brain and spinal cord
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what is a sensory nerve
it is afferent which means the impulse travels from the body to the cns
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what is a motor nerve
it is efferent so the impulse travels from the cns to the body
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what is nervous tissue
tissue which is found on the brain and spinal cord. responsible for coordinating and controlling body actions
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what is a neurone
a nerve cell which conducts impulses
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what is neuroglia
it connective tissue which supports the neurone
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what are nerves nerve fibres/tracts
bundles of neurones bound together
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what does the cell body do of a neurone
it connects to dendrites and take the impulse to the axon
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what are dendrites
part of neurone which receives the impulse
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what is an axon
the pathway the impulse travels from cell body to terminal boutons
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what are schwann cells
variety of glial cells that keep nerve fibres alive. they form the myeline sheath
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what are the nodes of ranvier
they are gaps in the insulating sheath which allows the impulse to jump to and therefore facilitates conduction of nerve impulses.
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what are the terminal boutons
they transmit impulse to another cell
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what is a myelinated neurone
these are neurones where the axon is completely surrounded by a number of myelin sheaths. the myelin sheath insulates the axon with proteins and fats which aids the conduction of the impulse
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what is an unmyelinated sheath
this is when the axon only has one myelin sheath. So the impulses cannot jump from in between the nodes of ranvier and be conducted as fast
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how much of the body's oxygen and glucose does the brain use
- 20 percent o2
- 25 percent glucose.
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what are the 4 sections of the brain
- cerebrum
- diencephalon
- cerebellum
- brain stem
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what is the cerebrum made up of and what connects them
2 hemispheres connected by tissue called corpus collosum
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what is the outer layer of the cerebrum called
cerebral cortex - grey matter
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what is the structure of the ceberal cortex and why is it like this
it is rigid and bumpy has folds which creates a larger surface area for the cell bodies.
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what is the inner part of the cerebrum composed of
- nerve fibres which is called white matter
- also has motor and sensory nerve tracts that links brain to spinal cord.
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what is the cebebral hemisphere divided into and are they responsible for
- 4 sections including the
- frontal - motor area, responsible for intellect, behaviour and prediction
- parietal - awareness of movement and position
- temporal - interpretation of sounds and smells
- occipital - visual perception and association
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what does the diencephalon connect and what does the diencephalon include.
- it connects cerebrum to the brain spine
- it includes thalamus - allows recognition of pain, hot, cold, pressure and relays and redistributes impulses from brain to cerebral cortex
- hypothalamus - small region which releases hormones which regulates body temp, emotions, appetite and thirst and circardium rhythm
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how many hemispheres does the cerebellum have and what does the cerebellum do
- 2 hems
- coordinates actions around posture, movement and balance.
- receives information from sensory systems including eyes, ears, joints, muscles.
- analyses input and works with motor centre to reproduce a response.
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what is the brain stem made up of
- pons varoli
- mid brain
- medulla oblongata
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what is the mid brain and pons varolli made up of
nerve fibres, but some nuclei. they act as a relay between different parts of the brain up and down side to side.
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what does the Pons varolli include
clumps of nuclei calls pneumotaxic centre and the apneustic centre which works with the respiratory centre in medulla oblongata to control respiration
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what does the medulla oblongata consist of
- cardi centre
- respiratory centre
- reflex centre
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what happens at the medulla oblongata and what is this section called
its where the motor nerves from the motor area in the cerebrum cross over to the other side of the spinal cord. it is called the decussation of pyramids.
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where do the cranial nerves originate from and what does it do
- nuclei based in the brain
- distributes signals to and from structures mostly within head and neck
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how many pairs of cranial nerves are there and what is the most important one.
- there are 12 pairs
- vagus nerve
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what does the vagus nerve do
- extends beyond the brain and is known as the wonderer
- works with heart, sexual organs and respiration
- it is a parasympathetic nerve
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talk about the spinal cord
- continuous with medulla oblongata
- solid structure of nerve endings
- 45 cm long
- extends down to L1/2 where is stops being solid and fans out to become the cauda equina
- cell bodies - grey matter - arrange in an H on inside and surround by nerve fibres - white matter on the outside
- acts as a Link between brain and body
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what are the cranial nerves involved in controlling
sight, smell, taste, moving eyes, producing tears, shrugging shoulders, chewing, swallowing
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what are the meninges
3 layers of tissue that surround the brain and spinal cord
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name the layers of the meninges
- dura mater - tough double layer lining the skull and brain
- sub dura mater - space between dura mater and arachnoid mater
- arachnoid mater - thin web like tissue
- sub arachnoid space - space where csf is secreted
- pia mater - delicate layer with blood vessels
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how many ventricles does the brain have
4
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what rate is csf secreted into each ventricle of the brain
0.5 ml per min
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where does csf flow and what aids its movement
in the sub arachnoid space and its aided by pulsating blood vessels, posture and respiration
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where is csf absorbed
by projections in the arachnoid matter
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what colour is csf
clear and colourless
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what does csf help to maintain
uniform pressure around the cns
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what does the csf do
- acts as a cushion
- lubricates the brain and cord
- exchanges nutrients and waste
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how many spinal nerves are there
31
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where do the first pair of spinal nerves leave the vertebral canal
between the occipital bone and the first cervical vertebra
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where do the spinal nerves end
at L1 where it fans out to form the cuada equina
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what does the ANS system do
subconsciously controls body functions and homeostasis by using specific ANS nerves to effect smooth muscle, cardiac muscle and glands
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what divisions are the ANS system split into
sympathetic and parasympathetic
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what does the sympathetic system do
- its the fight or flight
- speeds things up apart from digestive activity
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what does the parasympathetic system do
stimulates digestion and absorption over other systems
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