Nervous Tissue. Nervous Tissue. Cell body : Contains the nucleus, cytoplasm, mitochondria, endoplasmic reticulum, ribosomes and golgi apparatus. Dendrites: short, often highly branched extensions of the cytoplasm which carry messages into cell.
Nervous Tissue • Cellbody: Contains the nucleus, cytoplasm, mitochondria, endoplasmic reticulum, ribosomes and golgi apparatus. • Dendrites: short, often highly branched extensions of the cytoplasm which carry messages into cell. • Axon: single, long extension of cytoplasm which carries messages away from the cell. Length ranges from 1mm to 1m.
Nervous Tissue • Myelin Sheath: fatty material covering the nerve fibre. Axon with sheath is named a myelinated fibre, those without are unmyelinated fibres. • Three functions: • 1. Insulation • 2. Protection • 3. Speeds up nervous impulse along axon. (NOR)
Nervous Tissue • Neurilemma: membrane around myelin sheath which helps repair damaged fibres. • Schwann cells: Outside brain, special cells which make up the myelin sheath. • Nodes of Ranvier: Gaps in the myelin sheath at regular intervals. • Synapses: Junction between adjacent neurons. (between axon and dendrite/cell body)
Nervous Tissue • Nerve Fibre: any long extension of cytoplasm. (usually referring to axon) • Nerve: A bundle of nerve fibres held together by connective tissue. - Ganglion: A group of neuron cell bodies outside the brain or spinal cord.
Nervous Tissue Types of Neurons Functional Classification: • Sensory (receptor): Carry messages from sensory receptors to brain/spinal cord. • Often has long myelinated dendrite. • Motor (effector): Carry messages from brain/spinal cord to muscles and glands • Motor end plate: The point where each branch of the motor neurons axon meets the muscle fibre. May connect to 1 or 100 muscle fibres. • Neuromuscular junction: synapse (small gap) between motor end plate and muscle fibre • Interneuron (Connector/association neuron): located in the brain and spinal cord and are the link between the sensory and motor neurons.
Nervous Tissue Structural Classification: • Multipolar: One axon cell body multiple dendrites • Bipolar: One axon cell body one dendrite (each may have many branches) • Often connect with receptor cells • Unipolar: dendrites fused to one axon cell body same axon (fused to) dendrites