Introduction to the peripheral nervous system Flashcards
why do we need the nervous system
helps maintain homeostasis
detects changes inside and outside the body by allowing us to interact and respond to the external environment
describe the function of the sympathetic nervous system
increases HR
dilates pupils
bronchodilation
reduced blood flow to the gut
shuts down blood flow to peripheral skin
stimulates sweat glands
define bronchodilation
increase BR by widening the airways
describe the parasympathetic nervous system function
decreases HR
constricts pupils
bronchoconstriction
increased blood flow to gut and to salivary glands
increased stimulation/movement of intestines
inhibit sweat production
where is myelin produced
oligodendrocytes myelinate axons in the CNS
schwann cells myelinate axons in the PNS
define neuroglia
supporting cells of the nervous system
examples of neuroglia
oligdendrocytes
astrocytes
microglia
ependymal cells
describe the function of astrocytes
help to form blood-brain barrier
describe the function of microglia
remove bacteria and damaged tissue
describe resting potential
-70mV
K+ diffuses out down a chemical gradient and diffuses in down its electrical gradient
intracellular: low Na+, high K+, high anions
extracellular: high Na+, low K+, low anions
describe an action potential generation
stimulus received
Na+ channels open and diffuse into neurone
threshold reached (-55)
that triggers the opening of Na+ voltage gated channel
more Na+ influx
depolarisation of neurone (inside more +ve)
to +40mV
describe repolarisation
change in charge triggers K+ voltage gated channel to open and K+ leaves neurone
repolarisation (inside more -ve)
Na+ channels close
Na+/K+ pump returns levels to resting potential as it expels 3 Na+ in exchange for 2 K+
describe the refactory period
membrane behind the travelling action potential is temporarily unexcitable until repolarisation occurs
describe axonal conduction on a myelinated neurone
saltatory conduction
electrical changes only occur at the nodes of ranvier so the depolarisation jumps from one node to another
faster
describe synaptic transmission
action potential arrives and voltage gated Ca2+ channels open
influx of calcium ions triggers vesicles to move and fuse with nerve membrane
neurotransmitters diffuse across synaptic cleft
act on specific receptors on post synaptic neurone
describe neuromuscular transmission
action potential arrives and voltage gated Ca2+ channels open
influx of calcium ions triggers vesicles to move and fuse with nerve membrane
neurotransmitters diffuse across synaptic cleft
act on specific receptors on motor end plate
describe neurotransmitters action
they affect postsynaptic neurone for as long as they spend in synaptic cleft
they are then inactivated by enzymes or by re-uptake into synaptic knob
describe the journey of sensory info in spinal cord
sensory receptors detect stimuli
travels from sensory neurone in spinal nerve into posterior dorsal root ganglion
then into dorsal horn from posterior sensory nerve root
to brain via central canal
describe the journey of information from the brain to an effector
from brain to ventral horn to anterior motor nerve root
to the effector
what are the basics of the PNS
dorsal and ventral roots
spinal nerves
peripheral nerves
name the 3 meninges of the brain (outer-in)
dura matter
arachnoid matter
pia matter
what does cerebral spinal fluid do
protects the brain and spinal cord by maintaining a uniform pressure around them and by acting as a cushion or shock absorber between the brain and the skull.
protects from inflammation by reducting friction
what is the origin of cerebral spinal fluid
circulates constantly from the ventricles through the subarachnoid space around the brain and spinal cord.
describe the function of the thalamus
send information about touch, pain and temperature
relays and redistributes impulses from most parts of the brain to the cerebral cortex.
describe the function of the hypothalamus
- effectors of the autonomic nervous system
- appetite and satiety
- thirst and water balance
- body temperature
- emotional reactions, e.g. pleasure, fear, rage, sexual arousal
- circadian rhythms, i.e. 24-hour body clocks, including the sleeping and waking cycle.
describe the function of the pons
processes information from some of the cranial nerves
5th: sensory information from the face, scalp, mouth and nose
8th: hearing and balance
describe the function of the medulla oblongata
autonomic reflex activity
includes the cardiovascular and respiratory centres and several reflex centres.
describe the function of the midbrain
important roles in auditory and visual reflexes.
