Introduction to the peripheral nervous system

Question 1

why do we need the nervous system

Answer 1

helps maintain homeostasis
detects changes inside and outside the body by allowing us to interact and respond to the external environment

Question 2

describe the function of the sympathetic nervous system

Answer 2

increases HR
dilates pupils
bronchodilation
reduced blood flow to the gut
shuts down blood flow to peripheral skin
stimulates sweat glands

Question 3

define bronchodilation

Answer 3

increase BR by widening the airways

Question 4

describe the parasympathetic nervous system function

Answer 4

decreases HR
constricts pupils
bronchoconstriction
increased blood flow to gut and to salivary glands
increased stimulation/movement of intestines
inhibit sweat production

Question 5

where is myelin produced

Answer 5

oligodendrocytes myelinate axons in the CNS
schwann cells myelinate axons in the PNS

Question 6

define neuroglia

Answer 6

supporting cells of the nervous system

Question 7

examples of neuroglia

Answer 7

oligdendrocytes
astrocytes
microglia
ependymal cells

Question 8

describe the function of astrocytes

Answer 8

help to form blood-brain barrier

Question 9

describe the function of microglia

Answer 9

remove bacteria and damaged tissue

Question 10

describe resting potential

Answer 10

-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

Question 11

describe an action potential generation

Answer 11

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

Question 12

describe repolarisation

Answer 12

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+

Question 13

describe the refactory period

Answer 13

membrane behind the travelling action potential is temporarily unexcitable until repolarisation occurs

Question 14

describe axonal conduction on a myelinated neurone

Answer 14

saltatory conduction
electrical changes only occur at the nodes of ranvier so the depolarisation jumps from one node to another
faster

Question 15

describe synaptic transmission

Answer 15

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

Question 16

describe neuromuscular transmission

Answer 16

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

Question 17

describe neurotransmitters action

Answer 17

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

Question 18

describe the journey of sensory info in spinal cord

Answer 18

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

Question 19

describe the journey of information from the brain to an effector

Answer 19

from brain to ventral horn to anterior motor nerve root
to the effector

Question 20

what are the basics of the PNS

Answer 20

dorsal and ventral roots
spinal nerves
peripheral nerves

Question 21

name the 3 meninges of the brain (outer-in)

Answer 21

dura matter
arachnoid matter
pia matter

Question 22

what does cerebral spinal fluid do

Answer 22

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

Question 23

what is the origin of cerebral spinal fluid

Answer 23

circulates constantly from the ventricles through the subarachnoid space around the brain and spinal cord.

Question 24

describe the function of the thalamus

Answer 24

send information about touch, pain and temperature
relays and redistributes impulses from most parts of the brain to the cerebral cortex.

Question 25

describe the function of the hypothalamus

Answer 25

• 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.

Question 26

describe the function of the pons

Answer 26

processes information from some of the cranial nerves
5th: sensory information from the face, scalp, mouth and nose
8th: hearing and balance

Question 27

describe the function of the medulla oblongata

Answer 27

autonomic reflex activity
includes the cardiovascular and respiratory centres and several reflex centres.

Question 28

describe the function of the midbrain

Answer 28

important roles in auditory and visual reflexes.