B9. 2 Nervous System Flashcards
what is the human nervous system made up of
- central nervous system (brain and spinal cord)
* peripheral nervous system (cranial nerves, spinal nerves and sense organs)
what does the CNS control
(brain and spinal cord)
what does the PNS control
(cranial nerves, spinal nerves and sense organs)
what is the function of a sensory neurone
transmit nerve impulses from the sense organs to the central nervous system
what is the structure of a sensory neurone
circular cell body
long dendron
short axon
what is the function of a relay neurone
• transmits nerve impulses from sensory neurone to motor neurone
where are relay neurones located
• located in the central nervous system
what is the function of a motor neurone
• transmit nerve impulses from central nervous system to nerve effectors
what is the structure of a motor neurone
• short dendron and long axon
define synapse
the junction or connection between two neurones
how does synapses facilitate nerve transmission between two neurones
Impulses are transmitted from an axon to a dendron across a synapse.
how is synapse transmission conducted
Transmission across a synapse is by chemical means (through neurotransmitters).
define reflex action
an immediate response to a specific stimulus without conscious control (involuntary)
define reflex arc
the shortest pathway by which nerve impulses travel from the
receptor to the effector in a reflex action
what are types of reflexes we have
- Cranial reflexes
* Spinal reflexes
what does the cranial reflex control
controlled by the brain but not by conscious will
what does the spinal reflex control
controlled by spinal cord
give examples of cranial reflex actions
pupil reflex, blinking, salivation
give examples of spinal reflex actions
knee-jerk reflex, sudden withdrawal of hand on touching hot object
what does dendrities do
dendrites of dendron receive nerve impulses from other neurones
what is the myelin shealth
layer of fatty substances that shields and insulates nerve fibre
what is the axon
nerve fibre that carries nerve impulses away from cell body
what is the motor end plates
junction between dendrite and muscle fibre
what are nodes of ranvier
regions where myelin sheath is absent to speed up transmission by allowing impulses to jump from node to node
what is the dendron
nerve fibre that transmits nerve impulses towards cell body
describe how a nerve impulse travels
- receptors in skin
- sensory neurone
- relay neurone
- motor neurone
- effector muscle
