Nerves and Disorders of the Nervous system Flashcards
What are nerves
basic units of the nervous system known as nerve cells/neurons
bundles of neurons are called:
PNS -nerves
CNS- tracts
How would you break down the structure of a nerve
- a nerve consists of many neurons
- these are bound together by connective tissue [perineurium]
- these bundles have delicate endoneurium surrounding the neurons
- an artery and vein occur between bundles to supply nourishment for the fibres and remove waste.
What does nervous tissue consist of, briefly describe these two structures
neurons and neuroglial
neurons form a continuous network extended all over the body + form structural units of the NS
- last for a lifetime in correct conditions
-cannot undergo mitosis
-very high metabolic rate
-need continuous supply of oxygen and glucose
neuroglial [ nerve cell glue]
glial cells make myelin, support and protect neurons
What is the structure of a neuron (nerve cell)
cell body + long thin processes [fibres of cytoplasm] extending from cell body making it possible for nerve impulses be carried over long distances
fibres are
-dendrites [ conduct impulses towards cell body]
-an axon conducting impulses away
[only one axon in a neuron but usually branches at end to form terminal branches]
What are the different classifications of neurons [3]
- sensory/unipolar, has one fibre [afferent i.e. impulses from receptor to CNS]
- connector/interneurons [multipolar, found in CNS]
- motor/multipolar [efferent i.e. impulses away from CNS to effectors to respond appropriately]
What are Nissl granules
group of ribosomes in neuroplasm
are involved in protein synthesis
What does the node of Ranvier do
allows rapid conduction of impulses by forcing them to jump between nodes
What is the function of schwann cells
wrap around axon several times and inner layer of fatty tissue fuse to form myelin sheath [electrical insulator to prevent disruption from neighbouring cells]
What is a nerve impulse
minute electrical signal caused by a stimulus [nerve impulses] and creates a difference in electrical charges across the nerve fibre membrane
what gives neurons the conducting abilities
their membranes are extra permeable to sodium and potassium ions [charged atoms]
what 5 components make up a reflex arc
- receptor
- sensory neuron
- connector neuron
- motor neuron
- effector
What is a Reflex arc
functional unit of the NS
[impulses do not travel to the brain]
it is a neutral pathway followed by impulses from a receptor to an effector via spinal cord to bring about a reflex action
two types of reflexes
1. somatic [activate skeletal muscles]
2.autonomic[activate smooth/cardiac muscles +glands]
How does a reflex arc function [6 steps]
- Free nerve endings of a receptor respond to stimulus from a pin prick and register it as pain
- Impulses are conducted along sensory neurons to grey matter in spinal cord
- Impluses now make synaptic contact with connector neurons [acting as reflex centres]
- impulses make synaptic contact with motor neurons which conducts them to the effector
- the effector [flexor muscle in finger] brings about a response by contracting away quickly
- impulses also conducted to cerebral cortex [parietal lobe] and interpreted as pain
Why are reflex arcs important
- Enable quick body responses
- are inborn safety mechanism to protect from danger
e. g. coughing when food enters trachea
What are synapses
the junction/gap across which a nerve impulses passes from an axon terminal to a neuron, muscle cell or gland cell
what are synaptic knobs
hundreds of small vesicles [sacs] filled with molecules of neurotransmitter e.g. the chemical acetylcholine
neurotransmitter is a chemical substance released from axon terminals at synapse to carry impulses across junction
Why are synapses important
Make sure impulses flow in one direction and allow dispersal of impulses to several locations
filter out unnecessary stimuli
What is Alzheimers disease [causes, how common, symptoms, and treatment]
incurable degenerative and terminal disease
cause: build up of amyloid plaques
common for older people [7 year life expectancy after diagnosis]
symptoms: short term memory loss, aggression, confusion and mood swings and death due to to loss of body functions
no cure, need mental stimulation, balanced diet and a caregiver
What is multiple sclerosis (MS)
[causes, how common, symptoms, and treatment]
autoimmune disease [immune system attacks myelin sheaths until destroyed]
age 20-40
cause: genetics and childhood infections
symptoms: issues with muscle control, walking difficulties, speech and visual difficulty and urinary incontinence
treatment: bovine myelin from cattle given to patients and showed some improvements over a year long study
but still incurable
