LC Biology- The Nervous System

central nervous system (cns)

brain and spinal cord

Peripheral nervous system (PNS)

nerves that carry messages

sensory neurons

carries impulses from sense organs to CNS

interneurons

carry messages between sensory and motor neurons

motor neurons 

carries impulse from CNS to muscles

threshold

The minimum stimulus needed for an impulse to travel, if the threshold is reached the impulse travels

ganglion

a group of cell bodies outside the CNS

receptor

a group of cells that detect a stimulus

dendrites 

fibres that receive and carry impulses to the cell body

axon

carry the impulse away from the cell body

schwann cells

make the myelin sheath

myelin sheath

insulates electrical impulses/ speeds up the passage of an impulse

synapse

the region between neurons

synaptic cleft

a tiny gap between 2 neurons

how are impulses transmitted along neurons

-the impulse moves from the dendrites to the neurotransmitter swellings 

-the electrical impulse moves by means of ions

-it can’t cross the synaptic cleft 

refractory period

the delay between 2 impulses

how is a message carried across a synapse?

• the electrical impulse travels to the neurotransmitter swellings and makes acetylcholine

• the neurotransmitter diffuses across the synaptic cleft 

• the neurotransmitter combines with receptors in the dendrite

• this causes an electrical impulse to be generated and passed on towards the cell body 

• the neurotransmitters are then digested by enzymes to be recycled and used again 

4 functions of synapses

• transports impulses 

• controls the direction of impulses

• prevent over stimulation of effectors 

• impulses can be blocked by certain chemicals at the synapse (useful for trecerating pain)

cerebrum

• controls voluntary muscles, receives impulses from sense organs intelligence,memory,language.

cerebellum

muscular coordination, balance

medulla oblongata

controls involuntary actions

thalamus

sends messages to different parts of the brain

hypothalamus

controls internal environment of body

pituitary gland

produces hormones

nervous system disorder- cause,prevention, treatment

parkinson’s disease- lack of dopamine, none yet, physiotherapy