3.8 The nervous system Flashcards
What is the role of the nervous system?
To transmit signals from the brain to the rest of the body, detecting processing and protecting
What is a stimulus?
A detectable change in the internal or external environment producing a response
What is a receptor?
A transducer of energy converting it to electrical
provide organisms with senses
What are the 8 senses?
Sight
touch
taste
smell
hearing
pain
temperature
balance
What is the CNS made up from?
Brain, Brainstem and spinal cord
Mostly intermediate neurones
What does the CNS do?
Processes information form a stimulus
What is the PNS made up from?
Neurones outside of the CNS
sensory and motor neurones
What is the spinal chord made up of?
Unmyelinated neurones bundled in a column
What are the divisions of the PNS?
The somatic nervous system
The autonomic nervous system
What is the function of the Somatic nervous system?
voluntary movements
sensory and motor neurones of the skeletal muscles
What is the general function of the autonomic nervous system? and what are its divisions?
unconscious control
Sympathetic and parasympathetic
What is the function of the sympathetic system?
‘Fight or flight’
increases energy functions
e.g. increases heart rate or sweating
What is the function of the parasympathetic system?
‘rest and relax’
lowers energy functions
What is a reflex arc?
A neural pathway taken by impulses in rapid unconscious actions to protect the body
What is the general route of a reflex arc?
Stimulus–Receptor—CNS—Effector—Response
What tissue type is an effector?
Gland or muscle
What is the reflex arc for heat withdrawal?
Heat—temperature receptors—Impulse up spinal chord to intermideate neurone—motor neurone contracts muscle
What organism has a nerve net?
hydra
What is a nerve net? and what it it made of?
A basic nervous system with no brain
Ganglia cells allowing signals in all directions and sensory cells that detect stimuli
What is the charge of a resting potential?
-70 mv
How do sodium and potassium move at rest?
K+ diffuses out
Na+ diffuses in
3 Na+ for every K+
How does the sodium potassium pump work?
- 3 Na+ bind to protein inside the cell
- ATP losses a Phosphate to the protein causing it to shift, releasing Na out of the cell
- 2 K+ bind to protein outside the cell
- P leaves protein releasing K into the cell
What causes an action potential?
Energy from stimulus opens gated Na channels
Rapid diffusion of Na+ into cell causes depolarisation
What voltage is a depolarized cell?
+ 40 V
What causes repolarisation?
- at +40v Na gates shut
- K gates open and K+ diffuses out of the cell
- membrane is repolarised
What causes hyperpolarisation?
K+ gates remain open and excessive K leaves
Na/K pump restores -70v
What voltage is hyperpolarisation at?
-90 V
What voltage is hyperpolarisation at?
-90 V
What voltage is the action potential threshold at?
-55 V
What is the ‘All or Nothing Law’?
Stimulus threshold must be met to generate an action potential
AP is always at +40V but frequency can increase
What factors impact conduction speed?
Temperature-faster ions
diameter of axon- more ions flowing
myelination- salutary conduction
length of axon
number of channels
What is Saltatory conduction?
Ap jump from node to node increasing conduction speed
What steps occur at the synapse? (9)
- Impulse arrives at bulb of pre-synaptic neurone
- Ca ion channels open in membrane
3.Ca ions diffuse down conc gradient - Vesicles of neurotransmitters fuse with presynaptic membrane
- exocytosis of neurotransmitters into synaptic cleft
- neurotransmitters diffuse across cleft and bind to receptor on post synaptic membrane
- Receptor proteins change shape
- Na ion channels open, Na diffuses down conc gradient
- depolarisation occurs and AP is generated
What steps occur at the synapse? (9)
- Impulse arrives at bulb of pre-synaptic neurone
- Ca ion channels open in membrane
3.Ca ions diffuse down conc gradient - Vesicles of neurotransmitters fuse with presynaptic membrane
- exocytosis of neurotransmitters into synaptic cleft
- neurotransmitters diffuse across cleft and bind to receptor on post synaptic membrane
- Receptor proteins change shape
- Na ion channels open, Na diffuses down conc gradient
- depolarisation occurs and AP is generated
What are the properties of a synapse? (4)
Move impulses in 1 direction
transmit between neurones
protect response system from overstimulation
filter out low level stimuli
What is a drug?
Molecule that has a physiological effect on the body when absorbed or injected
