3.8 Nervous System Flashcards
Functions of nervous system
- Detects changes
- Processes the information
- Initiates responses
2 parts of the nervous system
CNS
PNS
6 steps of the nervous system mechanism
Stimulus
Receptor
CNS
Effector
Response
Feedback
7 parts of the spinal cord
Sensory (contains cell body)
Relay
Motor
Dorsal root ganglian
Ventral root
Grey matter
White matter
8 parts of a motor neurone
Dendrite
Nucleus
Cell body
Axon
Myelin sheath
Node of ranvier
Schwann Cell
Axon terminal
Resting Potential
Sodium/Potasium pumps actively transports 3 Na+ out and 2 K+ in
Potasium also diffuse out
Sodium channels closed
Inside axon more negative
-70mV
Polarised
Action Potential
The rapid raise and fall of the electrical potential across a nerve cell membrane as impulse passes
Na+ channels open (Na+ diffuses in)
Mambrane becomes more permeable
+40mV
Depolarised
Why does impulse travell one way
Refractory period behind every impulse
Every nerve has synaps at the end
Repolarisation
Na+ channels close
K+ channels open
K+ diffuse out of axon
Becomes more negative than resting potential
Hyperpolarised
Refractory period
All or nothing principle
the size of the impulse is independant of the size of the stimulus
3 things that affects the speed of conduction
- Myelination
- Axon diameter
- Temperature
What if axon has no myelin
No saltitory conduction
Impulse cant jump from node to node
Myelin is a good eletrical insulator
Synaps functions
Transmit info between neurones
Transmit info in one direction only
Acts as a junction
Protects form over stimulation
2 types of synaps
Eletrical - impulse jump
Chemical - too big for impulse to jump - neurotransmitter is needed
How does impulse cross a synaps
- impulse arives
- Ca2+ diffuses into presynaptic knob
- Vesicles fuse to presynaptic membrane and relese neurotransmitter (acetylecholine) by excotyosis
- acetylecholine diffuse and attaches to 2 receptor sites
- Protein channels open Na+ diffuses into post synaptic membrane - Depolarised
- Acetylsecholinesterase breaks down acetylecholine and diffuses back into presynaptic membrane as chloride and ethanoic acid
Effects of drugs
Alters brain behaviour
increase alertness
Plesant - euphoria
Excitatory
- Drugs increase action potential
- Mimic neurotransmitter
- Inhibit breakdown of neurotransmitter
- Block uptake back into presynaptic knob
- Increase number of receptors on post synaptic membrane
Inhibitory
- Decrease action potentials in post synaptic membrane
- Prevents exocytosis
- Binds with receptors on post synaptic membrane and blocks it
- Provents Ca2+ entry
Function of:
Cell body
Contains nucleus and cytoplasm
Function of:
Cytoplasm
Granular; contains many ribosomes
Function of:
Nucleus
Holds DNA
Function of:
Nissl granules
Synthesise neeurotransmitter
Function of:
Dendrite
Carries impulse towards cell body
Function of:
Axon
Carries impulse away from cell body
Function of:
Schwaan cells
Wrap around axon synthesise myelin
Function of:
Myelin Sheath
Electrical insulator
Function of:
Node of ranvier
Gaps in myelin sheath
Function of:
Axon terminal
Transmits impulse to adjacent neurone
