nervous system Flashcards
What is the function of the nervous system
•Function is control and co-ordination
• it’s fast, has short lived responses and is electrically mediated
What are examples of glial cells
Ependymal cells, microglia, astrocytes, oligodendrocytes
What do ependymal cells do
Assist in the production of cerebrospinal fluid
What are microglia and what do they do
•They are immune cells for our brain •remove debris waste by phagocytosis (phagocytic)
•can recruit other white blood cells
What do astrocytes do
•Absorb/recycle neurotransmitters
•involved in regulating/recycling neurotransmitters
•also highlighted by GSAP markers
•formation of blood brain barrier
What do oligodendrocytes do
•Myelinate central nervous system dendrites (up to 50 axon)
What are neurons
The functional units of the nervous system
What type of cells are the most important in the brain
Glial cells as they do everything a neuron can’t do
What can glial cells do
•store glycogen
•potassium buffering
•contact every synapse in brain
What do we have more of glial cells or neurons?
Glial cells
What cells in the peripheral nervous system myelinate axons
Schwann cells
What is the function of neurons
To process information which are mediated by neuronal membrane functions
What are the three regions of a neuron
• cell body and dendrites (receive info- inputs)
•axon (needed for transmission
•axon terminals (contacts other neuron to pass the info-outputs)
How are neurons classified
Based on their structure
Where are the purkinjee neurons located
In the cerebellum
unipolar neuron
Cell body in the middle but not directly attached
Bipolar neuron
Cell body in middle and directly attached to axon
Suniunipolar neuron
Cell body to the side
What is an afferent neuron
A sensory neuron (carry nerve impulse from skin to spinal cord)
What is an efferent neuron
A motor neuron (carry info from the spinal cord to muscle)
What is divergence
The spread of info to several neurons
What is convergence
When there are several neurons synapse on a single neuron so lots of info is collected together in one area of the brain
What is serial processing
When one neuron sends info to another (stepwise processing of information)
What is parallel processing
When lots of neurons receive the same info (divergence has to occur)
Example reflection arc (stepping on a pin)
What is reverberation
Positive feedback loop
Example maintenance of wakefulness (reinforcing you’re awake)
What is the central nervous system split into
The brain and spinal cord
What what protects our brain
•bone
•cerebrospinal fluid
•meninges
What are the three roots the spinal cord split into
Cervical root, thoracic root and lumbar root
Name the lobes in the brain
Parietal lobe, frontal lobe, occipital lobe and temporal lobe
What are the divisions of the brain
•Medulla
•pons
•midbrain
•limbic system
•diencephalon
•cerebrum
•cerebellum
As you go down the divisions of the brain what happens
It’s complexity increases
What is the oldest part of the brain
The medulla
What is the function of the medulla
•autonomic control
•carries out basic functions
What is the origin of the cranial nerve
The medulla
What is the midbrain part of
The reticular formation
What is the reticular formation
Maintenance of wakefulness and aspects of visual and auditory processing
How many cranial nerves are there
12
Where are nerves supplied to
head and neck but not vagus nerve
What is the diencephalon split into
Hypothalamus and thalamus
What is the function of the hypothalamus
•Controls release of own and different hormones of the pituitary gland
•controls body temperature
•nerves in hypothalamus regulate behavioural patterns like eating
What is the function of the thalamus
Acts as a filter as it’s the final relay point for sensory information that will go into cortex
Where is there cerebellum situated
Below the cerebrum and behind the brainstem
What is the cerebellum divided into
2 lobes that are further divided into 9 lobules
What does the cerebellum consist of
Outer grey matter and internal white matter
What connects the cerebellum to the brainstem
3 pairs of nerve fibres called cerebellar peduncles
What are the cerebellar peduncles
•inferior= cerebellum - medulla
•middle= cerebellum - pons
•superior= cerebellum- midbrain
What does the inferior cerebellar peduncle do
Receives inputs from proprioceptors (sensory receptors)
What does the middle cerebellar peduncle do
Voluntary motor activity
What does the superior cerebellar peduncle do
Fibres from cerebellum to motor cortex via thalamus
What can happen if there is a loss of cerebellum
Significant motor abnormalities such as:
•staggering walk and difficulty standing- cerebellar ataxia
•loss of coordination (asynergia) and muscle tone (hyptonia)
Why is there electrical stimulation in the cerebellum
To avoid losing sensation or movement
What is the function the cerebellum
Controls postural muscles and for rapid muscular activity such as typing
The cerebrum is split into 2 cerebral hemispheres but by what
Longitudinal fissures
How made lobes does each hemisphere have
4 lobes
What are the 2 hemispheres connected by
The corpus callosum
Which one grows quicker the white matter or cortex
The cortex
What is the outer layer of the hemispheres
The cortex
What are peaks called
Gyri
What are troughs called
Sulci
What is the cortex divided into
Motor, sensory, association and integrative areas
what is an action potential
- communication of information
- conduction of info along a nerve cell
- membrane phenomenon
what’s the intracellular recording of an action potential
- depolarisation: decrease in membrane potential so it becomes less negative
- repolarisation: increase in membrane potential so it becomes more negative
- hyperpolarisation: the membrane potential returns to it’s resting membrane potential.
what is the ionic basis of an action potential
firstly, Na+ increases in permeability so it’s removed from the extracellular fluid. The peak of the action potential is almost the same value as the Na+ electrochemical equilibrium potential (as nernst suggests) which means increased Na+ permeability is needed. the Na+ moves as the voltage gated Na+ channels open
what binds to phosphorylation sites
lots of toxins are produced which then bind to it
what triggers an action potential
- depolarisation to threshold has to occur before an action potential can be generated.
- the depolarisation has to bring the membrane at the axon hillock to threshold which is normally 15-30 mV (above resting membrane potential).
what happens at threshold
the voltage gated sodium channels open (depolarisation) which causes an influx of sodium ions.
what happens at the action potential peaks
- reversal of membrane potential from -60mv to +40mv
- the inactivation of the sodium channels starts to occur meaning the channels start to close when the membrane potential reaches +30mv (don’t open again until repolarisation)
- the voltage regulated potassium channels start to open
what happens when the action potential returns to rest
- the potassium ions move out of the cell across a electrochemical gradient (passive movement, repolarisation)
- the membrane potential starts to return to resting level
- K+ channels close
- a little hyperpolarisation occurs
- the sodium-potassium pump restores the intracellular and extracellular ion concentration back.
what is the refractory period
this is the period of time where the first action potential is generated and it’s impossible or difficult to generate a second one.
what is the relative refractory period
- relative RP is when the sodium channels regain their resting conditions to when the membrane potential is at resting level (membrane is excitable and even stronger if threshold applied)
what is the absolute RP
- the time from when the sodium channels open to when inactivated which is 0.4 - 1second
the membrane is inexciteable
what does resting suggest about the membrane potential
that it’s stable
what are membrane potentials measured as
voltage
what is the value of resting membrane potential
-70mv to -90mv
what surrounds a neuron
plasma membrane
what are two types of plasma membrane
extracellular and intracellular fluid
what is the difference between the composition of extracellular and intracellular fluid
- one difference is that extracellular fluid has higher levels of Na+ (145) compared to intra (20)
- another difference is that intracellular fluid has higher K+ levels (150) compared to extra (4)
what causes the difference in the compositions between extracellular and intracellular fluids
the sodium/potassium pump is electronegative
what is K+ efflux
when potassium ions leave a cell
what is Na+ influx
when sodium ions enter a cell
what can K+ efflux develop on a membrane
can lead to the development of a voltage across a membrane
