Nervous System PDF

Nervous system The nervous system enables animals to A nervous response follows this pathway: An effector is a muscle or gland. The respond to changes in the external or internal...

Nervous system The nervous system enables animals to A nervous response follows this pathway: An effector is a muscle or gland. The respond to changes in the external or internal Stimulus  Receptor  Sensory neurone  Relay neurone in CNS  Motor neurone  Effector  Response motor and sensory neurones are part of environment, also known as stimuli. the peripheral nervous system. Central Structure of the spinal cord Cell body canal Dorsal root A reflex action is a fast, automatic response (sensory Sensory neurone ganglion Grey matter is grey as it contains many cell bodies to a stimulus that has a protective function. neurone) and nuclei. Dorsal root Receptors detect the harmful stimulus and The white matter is white as many axons, wrapped send impulses through sensory neurones to Motor neurone in the lipid myelin, pass through this region. a relay neurone in the spinal cord. This sends an impulse through a motor neurone to an Ventral root The central canal contains cerebrospinal fluid. effector, which responds to protect the body. Relay Grey matter Effector neurone The spinal cord is surrounded by membranes called White matter meninges. Motor neurone Dendrites transmit impulses into the cell body. In simple organisms such as Hydra, Schwann cells wrap around the axon and form the receptors respond to a limited Dendrites Node of Ranvier myelin sheath, an electrical insulator. number of stimuli, so the number of effectors is small. They have a Nodes of Ranvier are gaps in the myelin sheath nerve net of identical branching that form long local circuits with the next node, neurones that are interconnected. Axon speeding up transmission. The neurones are unmyelinated Axon Cell body and send impulses in all directions. endings Axon transmits the impulse to the axon endings. Myelin sheath and Schwann cell Axon endings innervate effectors.