129873
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Mind Map by harry_bygraves, updated more than 1 year ago
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Created by harry_bygraves
almost 11 years ago
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Chemical and electrical coordination 1
- All the various animal nervous sytems are fast-acting communication systems containging nerve cells,
neurones. These convey information in the form of nerve impulses which are electrical in nature.
- Neurones take various forms but each has a cell body, containing a nucleus, and nerve fibres (long
extensions that transmits nerve impuses rapidly from one part of the body to the other) Fibres carrying
impulses away from the cell body are called axons; those carrying impulses towards the cell body are called
dendrons. Apart from the main nerve fibre, there may be small dendrons extending from the cell body.
- In mammals, sensory neurones carry
messages from pheripheral sense organs to a
centeral nervous system (CNS) consisting of
the brain and spinal cord. The CNS acts as an
integration centre and processes information
from many sources. Motor neurones convey
intructions from the CNS to effector organs
- The effect of a neurone on an effector
depends on chemicals called
neurotransmitters that are released by nerve
endings directly onto target cells. Some
neurones are excitatory- they secrete
neurotransmitters that make an effector more
active. Other neurones are inhibitory- they
secrete neurotransmitters that make an
effector more active. Whether excitatory or
inhibitory, the effect of the neurotransmitters
is usually rapid, short lived and localised.
- Organisation of the mammalian nervous system. Structually, the mammalian
nervous system consists of a CNS and the pherpheral nervous system. A nerve
is a thread like structure containing a bundle of nerve fibres. A single nerve may
contain both sensory and motor neurones.
- Functionally, the mammalian nervous
system is divided into the somatic nervous
system and the autonomic nervous system
- The somatic nervous systems includes sensory
neurones which transmit impulses from pheripheral
receptors to the CNS, and motor neurones which
send impulses to skeletal muscles. It is sometimes
called the voluntary nervous system (VNS) becuase
many of its actions are under concious control
- The autonomic nervous
system (ANS) is sometimes
called the involuntary nervous
system because it usually
enables internal organs to
function properly without any
concious control. It has two
parts; the parasympathic
nervous system, the
sympathetic nervous system
- These general act antagonistically,
while the parasympathetic nervous
system maintains the body in
non-threatening situations, the
sympathic nervous system prepares the
body for aaction during periods of
excitment or danger. Hence the vagus
nerves slows down the heart rate and
sympathetic speeds it up.
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