grey matter Flashcards
what do dendrites do?
transfer nerve impulses to the cell body
what do axons do?
transfer nerve impulses away from the cell body
what is a myelin sheath?
lipid insulation of an axon
how is a myelin sheath created?
lipids are secreted by schwaan cells
what is the soma?
cell body of a neurone
what are the nodes of ranvier?
gaps inbetween the myelin sheath
what does a sensory neurone do?
carry impulses from the receptor to the CNS
what does a relay neurone do?
carry impulses from the CNS to the motor neurone
what does the motor neurone do?
carry impulses from the CNS to the effector
name 3 advantages of a myelin shieth?
- speeds up the impulse
- protect neurone from damage
- protect neurone from interferance
what are the 2 parts of the peripheral nervous system?
- autonomic = involuntary
- somatic = voluntary
what are the 2 parts of the autonomic nervous system?
- parasympathetic
- sympathetic
what is the sympathetic nervous system responsible for?
active and alert responses
what is the parasympathetic nervous system responsible for?
rest and digest responses
describe the relationship between the sympathetic and parasympathetic nervous system?
antagonistic
name the 2 muscles in control of pupil size?
- circular
- radial
where are the radial and circular muscles located?
the iris
describe the relationship between the radial and circular muscles?
antagonistic
describe the process of pupil dilation?
- nerve impulses sent along the optical nerve at low frequency
- impulses reach sympathetic motor neurones, sent to radial muscles
- radial muscles contract, more light reaches the retina
describe the process of pupil constriction?
- nerve impulses sent along the optical nerve at high frequency
- impulses reach parasympathetic motor neurones, sent to circular muscles
- circular muscles contract, less light reaches the retina
define resting potential?
state of nerve fibres when not conducting
what causes a resting potential?
- imbalance in NA and K ions
- difference in permeability to ions in the cell membrane
what charge is the axon outside?
+
what charge is the axon inside?
-
what is the potential difference when there are no impulses?
-70mv
name the carrier protein within neurones?
sodium-potassium pump
what ratio does the sodium-potassium pump move ions in?
3 NA out for every 2 K in
is an unstimulated nerve cell polarised or depolarised?
polarised
is an stimulated nerve cell polarised or depolarised?
depolarised
name the 5 stages that occur after a nerve cell receives an appropriate stimulus?
1) NA channels open after stimulus, more NA diffuses into the cell making the inside less negative
2) once -55mv is reached, more NA channels open, creating a potential difference of +40mv, end of depolarisation
3) start of repolarisation by NA channels closing and K opening
4) K diffuses out of the cell and eventually restores resting potential, channel closing is delayed, so there is brief hyperpolarisation
5) resting potential is achieved with the sodium potassium pump
what is the threshold value?
-55 mv
what happens if a stimulus does not reach the threshold value?
a failed initiation
what is a refractory period?
state of recovery that occurs after a neuron has fired an action potential
describe the absolute refractory period?
no stimuli can cause an action potential, lasts 1ms
describe the relative refractory period?
an action potential can be caused if the stimulus is very high
how does a myelin shieth increase the speed of impulses?
myelin changes charge on each end so impulses can jump across nodes of ranvier by saltatory conduction
what does the presynaptic membrane do?
release neurotransmitters
what does the postsynaptic membrane do?
recieves neurotransmitters
what are the 2 main types of neurotransmitters?
- exitatory
- inhibitory
what does an exitatory neurotransmitter do?
causes depolarisation (+) and generates an action potential
what does an inhibitory neurotransmitter do?
causes hyperpolarisation (-) and prevents an action potential
what is the space between synapses called?
synaptic cleft
how are neurotransmitters transported to the presynaptic membrane?
in vesicles
why do synaptic vesicles move toward the presynaptic membrane?
calcium channels open, causing an influx of CA ions
what is a stimulus?
a sensory input from the environment
what do cones detect?
colour in bright light
what do rods detect?
black and white vision, sensitive to light intensity
how many cones attach to a bipolar cell?
1
how many rods attach to a bipolar cell and what does this do?
3, this gives a greater chance of recepting in low light
what is rhodopsin?
light sensitive pigment in rods
what is the process of splitting rhodopsin called?
bleached
what does rhodopsin split into?
- retinal
- opsin
what is glutamate?
an inhibitory neurotransmitter
what is brain grey matter and where is it found?
neuronal cell bodies, outer part of brain
what is brain white matter and where is it found?
myelinated axons, inner part of brain
what is the cerebral cortex responsible for?
consciousness, intelligence, memory and language
what is the cerebellum responsible for?
co-ordination and balance
what is the medulla responsible for?
unconscious activities
what is the hypothalamus responsible for?
controls thermoregulation
name all 4 types of brain scan?
- CT scan
- MRI
- FMRI
- PET
name 3 features of CT scans?
- uses X-rays
- denser parts absorb more radiation, so they appear lighter
- shows structure not function
name 3 features of an MRI?
- uses magnetic fields and radio-waves
- shows structure not function
- clear tumor detection
name 2 features of an FMRI?
- shows location of oxygenated blood, showing activity
- shows structure and function
name 3 features of a PET scan?
- patient is injected with radioactive glucose
- amount of glucose detected indicates which areas are active
- shows structure and function
what is a critical window?
time periods after birth that the nervous system needs specific stimuli in order to develop properly
what are ocular dominance columns?
strips of neurones in the visual cortex that respond preferentially to input from a certain eye
what happens if the visual critical window is missed?
Neurones aren’t stimulated, so action potential isn’t received and synapse connections in the ocular dominance columns become weaker until they’re lost
define habituation?
when an animal receives a repeated stimulus without any positive or negative outcome, it will learn not to respond
what hormone affects depression?
seratonin
what hormone affects parkinsons?
dopamine
why cant dopamine be injected to treat parkinsons?
it cant cross the blood brain barrier
why is leva-dopa used to treat parkinsons?
it can cross the blood brain barrier, where its absorbed by nerve cells and turned into dopamine
what do SSRI’s do?
blocks serotonin removal from the synaptic cleft
what is the 5-HTT gene responsible for?
recycling seratonin from synaptic cleft to pre-synaptic membrane
