The Nervous System Flashcards
(30 cards)
What is the nervous system?
The communication network and control centre of the body.
What is the nervous system made up of?
The brain, spinal cord and nerves.
What are the two divisions of the nervous system?
Central and peripheral
Draw a flow diagram of all the divisions in the nervous system.
- central - brain + spinal cord
- peripheral - afferent division and efferent division - somatic division and autonomic division - parasympathetic (fight or flight) and sympathetic (rest and digest)
What is the central nervous system?
Where incoming messages are processed and outgoing messages are initiated.
What is the CNS protected by?
- bones of the brain - cranium and vertebral canal provide a strong rigid structure.
- meninges - three layers of connective tissue forming membranes.
- CSF - cerebrospinal fluid.
What are the three layers of the meninges and their functions?
- Dura mater (outer layer) - tough and fibrous, sticks to the bones of the skull.
- Arachnoid mater (middle layer) - loose mesh of fibres.
- Pia mater (inner layer) - delicate, contains blood vessels, sticks to the surface of brain and spinal cord.
What is CSF?
Cerebrospinal fluid, is a clear, watery fluid containing a few cells and some glucose, protein, urea and salts.
Where is CSF stored?
Occupies the sub-arachnoid space and circulates cavities in the brain and central canal of the spinal cord (sub-dural space).
What are the functions of CSF?
- Support - brain is suspended in fluid, buoyancy.
- Protection - acts as a shock absorber and cushions the brain.
- Transport - takes nutrients to cells of the CNS and carries away their wastes.
What is a reflex?
A rapid, automatic response to a change in the internal/external environment.
- Requires a stimulus
- Involuntary
- Stereotyped (occurs the same way)
What are learnt reflexes?
- Acquired through constant repetition.
- Not genetic like some other reflexes.
What are the different types of receptors?
- Thermoreceptors
- Osmoreceptors
- Chemoreceotirs
- Touch receptors
- Pain receptors
What are receptors?
A structure able to detect a change in the body’s internal/external environment. When stimulated the body responds to a change this can be an automatic reflex or more complex.
What are thermoreceptors?
Respond to heat and cold. Skin receptors inform brain on external temperature changes. Hypothalamus receptors respond to internal temperature changes.
What are osmoreceptors?
Located in the hypothalamus and detect changes in osmotic pressure (body’s water content).
What are chemoreceptors?
Detect changes in blood pH and gas concentrations. Nose - odours, moth - taste.
What are touch receptors?
Found mainly in the skin, especially lips, fingertips and eyelids. Some are close to the skin and respond to hair receptors, some deeper and respond to pressure and vibrations.
What are pain receptors?
stimulated by damaged tissues, located in most organs but the brain.
What is the process of a reflex arc?
stimulus - receptor- sensory neuron - interneuron - motor neuron - effector - response
Describe the steps involved in nerve impulse transmission across a synapse.
- Nerve impulse reaches the axon terminal, causing voltage-gated calcium ion channels to open.
- Influx of calcium ions in the pre-synaptic axon terminal.
- Synaptic vesicles fuse with the membrane, releasing NTs by exocytosis.
- NTs diffuse across the synaptic cleft and attach to receptors on the post-synaptic membrane.
- This produces an AP.
- Enzymes break down the NTs for the next use.
What is a nerve impulse?
An AP that causes another AP in the adjacent membrane and continues along the length of the neuron.
Can the size of a nerve impulse change?
No, size of nerve impulses always stay the same. However, a strong stimulus causes depolarisation of more nerve fibres than a weak stimulus and a strong stimulus produces more nerve impulses in a given time than a weak stimulus.
How are nerve impulses transmitted along myelinated fibres?
Ions cannot flow through myelin sheath - APs instead jump from one Node of Ranvier to the next (saltatory conduction). This allows nerve impulses to travel much faster.
