Nervous system Flashcards
Central nervous system
functions as a coordination centre which processes information
consist of brain and spinal cord
peripheral nervous system
Consist of nerves and receptors
the nerves link the receptors to the CNS and the CNS to the effectors
The PNS also consist of all other nerve cells in whole or parts that lie outside the CNS
what is a nerve
a nerve is an organ consisting of a bundle of nerve fibres enclosed in a sheath of connective tissue
what does the cell body of the neurone contain
contains the nucleus, cytoplasm and organelles such as mitochondria
Features on dendron in the neurone
transmits nerve impulse to the cell body, the end branches of the dendron are called dendrites which receive signals from other neurones
features of axon
transmit nerve impulse away from the cell body
the ends of the axon are called axon terminals which transmit nerve impulses to effectors
myelin sheath
most long nerve fibres are covered with myelin sheath. The Prescence of myelin sheath insulates nerve fibres and increase speed of transmission of nerve impulses. Nodes of ranvier are regions where the myelin sheath are absent
sensory neurone
has a circular body with a long dendron and short axon
the cell body and dendrites are outside the CNS and the axon is inside the CNS
transmits nerve impulses from receptors to the CNS
Relay neurone
Relay neurone can have an irregular or circular cell body
the whole neurone is inside the CNS
transmit nerve impulses from sensory to motor neurone and to other relay neurones within the CNS
Motor neurone
irregular cell body with dendrites and long axon
cell body and dendrites are in the CNS and axon is outside the CNS
motor neurones transmit nerve impulses from the CNS to the effectors
how brain spinal cord and nerves serves to coordinate and regulate bodily functions
brain, spinal cord and nerves serve to coordinate and regulate bodily functions by helping organism adjust rapidly to any changes in their environment and enable various parts of the body to coordinate with each other.
reflex action
a reflex action is any immediate response to a specific stimulus that occurs without any conscious effort
simple reflex
built in unlearned responses which have protective functions
spinal reflec actions- reflec centre is in the spinal cord (withdrawal of hand)
cranial reflex actions- reflec centre is in the brain (blind, pupil reflex)
conditioned reflexes
acquired from past experiences of learning with a stimulus which was orignally not effective in producing response
describe spinal reflex
when hot object stimulates the thermorecptor on the finer, nerve impulses are generated.
nerve impules travel along the sensory neurone to the spinal cord
in the spinal cord, neurotransmitters are released across the synapse between the sensory neurone and relay neurone
the nerve impulse then flows along the relay neurone and neurotransmitters are released across another synapse to the motor neurone
nerve impulses leave the spinal cord along the motor neurone to the effector. the effector is the bicep muscles which is stimulated to contract to cause the withdrawal action
