The Structure and Function of the Nervous System Flashcards
what is the CNS composed of ?
brain and spinal cord
what is the PNS composed of ?
composed of nerves that connect the brain or spinal cord with muscles, glands and sense organs
define ‘neurotransmitters’
neurotransmitters are the chemical transmitters released from the neurones in response to chemical signals
define ‘processes’
the long extensions that connect neurones to each other
define ‘cell body’
also called the some; contains nucleus and ribosomes(protein synthesis)
define ‘dendrites’
branched outgrowths from the cell body/some that receive signals
define ‘dendritic spines’
knob-like outgrowths that receive inputs
define ‘axon’
the ‘nerve fibre’; a long process extending from the cell body/soma that carries signals to target cells
what is the size of an axon ?
ranges form 1 um to 1 m
define ‘initial segment’
the ‘trigger zone’ on the axon
define ‘axon collateral’
axon branches which carry the signal ‘sideways’
define ‘axon terminals’
the end of the axon which establishes synaptic contact with another neurone of an effector cell
define ‘varicosities’
bulging areas along the axon at which neurotransmitters can be released from
Neurones are wrapped in myelin. What is myelin ?
20-200 layers of modified plasma membrane
what is Myelin made of in the CNS and in the PNS ?
CNS - oligodendrocytes
PNS - Schwann cells
define ‘axonal transport’
to maintain the structure and function of the nerve fibre, organelles must more more than 1 m between the soma and the axon terminals via a process called ‘axonal transport’
what is axonal transport dependent on ?
Motor proteins called Kinesins and Dyneins
how do the Motor proteins in axonal transport work ? (2 points)
- at one end, the motor protein binds to the cellular cargo
- at the other end, the motor protein uses energy derived from ATP to ‘walk’ up or down the axon
state 2 facts about ‘Kinesin transport’
- Kinesin transport occurs at the cell body and carries down the axon (anterograde)
- carries nutrients, molecules, mitochondria, neurotransmitter filled vesicles, and other organelles
talk about ‘Dynein transport’ (2 points)
- retrograde (opposite direction to Kinesin transport)
- carry recycles membrane vesicles, growth factors, and other chemical signals that effect a neurones morphology, biochemistry and connectivity
talk about a potential danger associated with ‘Dynein transport’
the route at which some harmful agents enter the CNS (eg - polio virus)
state the three types of neurones
- afferent - sensory - convey info to CNS (enter via dorsal)
- efferent - motor - convey info from CNS (exit via ventral)
- interneurone - convey into within CNS (reflexes between afferent and efferent neurones)
state 2 facts about afferent/sensory neurones
- transmit into to CNS from receptors at their peripheral endings
- cell body and peripheral process in the PNS; short central process and axon terminals in CNS
state 2 facts about efferent/motor neurones
- transmit info out of CNS to effector cells
2. cell body, dendrites and small portion of axon in CNS; most of axon in PNS
state 4 facts about interneurones
- integration and signal changers
- create a reflex circuit
- lie entirely within the CNS
- constitute for > 99% of the total neurones in the human body
define ‘nerves’
groups of afferent and efferent neurones together within a connective tissue sheath
define ‘synapses’
the anatomical specialised junction between two neurones which neurotransmitters diffuse across
A) what proportion of the neurones in the CNS are composed of Glial cells ?
B) what proportion of the space in the CNS is composed of Glial cells ?
A) 90%
B) 50% (neurones branch more extensively than Glial cells so take up more space)
what is the main function of Glial cells ?
surround the Soma, axon and dendrites and provide them with physical and metabolic support
state 2 functions of Astrocytes (type of glial cell)
- regulate extracellular fluid by removing potassium and neurotransmitters
- form tight junctions with cells forming capillaries forming a blood-brain barrier (prevents toxins and other substances entering the brain)