IB Biology : neural signalling C2.2

stopped at neuroglandar junction

Stimuli

a change in the environment

sensory imput

stimuli which are perceived by our senses, like smell, sight, touch, taste and hearing

nervous system

organised network of nerve tissue in the body which transmits nerve impulses between parts of the body

parts of nervous system

• central nervous system

• peripheral nervous system

structure of a neuron

• contains nucleus, but no centrioles as it doesn’t reproduce

• dentrites are small, branched muscle fibers

• the thing connection the neuron body and the long thing (axon) is the axon hillock

action potential

a rapid, temporary change in the electrical membrane potential of a neuron or other excitable cell

schwann cell

type of glial cell that separates and insulates nerve cells. in the peripheral nervous system, schwann cells secrete myelin

myelin sheath

a protective, insulating layer around the axon, made up of 75% lipids and 25% proteins

Oligodentrites

secrete myelin in the central nervous system

name of spaces without myelin in schwann cells

nodes of Ranvier

types of neurons

• sensory neurons

• intermediary/relay neurons

• motor neurons

Resting potential ration of Na and K ions

Sodium and chloride ions greater concentration outside

Potassium, and organic anions greater concentration inside

causes potential difference between inside and outside

inside negative, outside positive

resting potential

potential of the cell when not stimulated, 70mV, disturbed when neuron conducts signals

nerve impulse

temporary reversal of electrical potential in membrane → the signal transmitted along a nerve fibre, which is transmitted to another neuron or effector cell

sodium potassium pump

takes 3 sodium ions out of cell, and 2 potassium ions inside of cell using ATP

causes a negative charge to build up inside of cells. neuron is polarised

process of depolarisation

• stimuli/ neurotransmitter binds to receptor

• sodium channels opens

• sodium ions diffuse inside of cell

• reverses polarity of axon fiber and depolarises it ( positively charged ions charge in )

• this travels as a wave throughout the entirety of the axon

factors for nerve conduction velocity

• amount of myelination: more myelin, faster the action potential moves

• diameter of axon: larger diameter, faster propagation. this is because less SA for leakage of ions

• temperature: the warmer, the faster the transmittion

speed at which a nerve impulse travels down

nerve conduction velocity

squid axon

no myelin sheath, but because half a mm thick still have reasonably fast nerve impulse

what are synapses ?

 they are junctions between neurons and between neurons and effector cells. neurotransmitters can only go in one direction

synaptic knob

end part of axon terminal

synaptic cleft

space between two neurons

neuromuscular junction

specialised synapse betwen a motor neuron and muscle fiber

the motor neuron releases acetylcholine, which binds on receptors of sarcolema, and causes depolarisation of sarcolema → release of calcium from sarcoplasmic reticulum