The Nervous System Flashcards
Reflex reaction
Involuntary and almost immediate response to a stimulus
Types of neurons
Motor Sensory Relay
Cell body
The part of a neurone which contains the nucleus
Dendrites
Extensions which receive nerve impulses from other cells; the nerve impulses are then transmitted towards the cell body
Axon
Carries nerve impulses to an effector organ
Myelin sheath
Fatty sheath which insulates the axon (preventing short-circuits of electrical impulses) and speeds up the conduction of nerve impulses
Nerve muscle junction
The point between the branches of the axon and the muscle cells
Reflex arc
The pathway thought the nervous system that reflex takes
Spinal cord
Extension of the CNS from the brain which is enclosed by the vertebral column
Summary of the reflex arc
Sense organ receptor senses stimulus Sensory neurone detects and passes to relay (through spinal cord) and to motor neurone which triggers a response from the muscle effector
Dorsal root ganglion
Module on dorsal root containing ell bodies
Grey matter
Darker tissue of spinal cord
Synapse
Tiny gal between two neurones
Nerve impulses across synapse
Travels to synapse as electrical impulse They trigger vesicles, containing neurotransmitters, to move to the membrane Neurotransmitters released across synapses then bind to receptors on the next neurone This triggers new nerve impulse
Cornea
Clear later at front of eye Helps to refract and focus light
Lens
Transparent structure behind pupil Refracts and focuses light
Pupil
Hole in centre of iris Controls amount of light entering eye
Iris
Pigmented tissue Controls amount of light entering eye
Suspensory ligaments
Ligaments in connecting the ciliary muscles and the lens Involved in controlling accommodation (focussing)
Ciliary muscles
Ring of muscle connected to lens via suspensory ligaments Controls accusation (focussing)