27. Nervous tissue. Histogenesis, General characteristics, Classification.

Nerve tissue is made of 2 types of cells; neurons and __________.

glial cells

The main function of nerve tissue is to __________ stimuli and transmit signals.

sense

The nervous system is divided into the __________ and peripheral nervous system.

central nervous system (CNS)

The CNS consists of the brain and __________.

spinal cord

The two divisions of the nerve fibers are the __________ and somatic nervous system.

automatic

The CNS is composed of grey matter and __________ matter.

white

The __________ surrounds each nerve and is made of dense connective tissue.

epineurium

The __________ surrounds bundles of nerve fibres.

perineurium

The __________ constitutes a thin layer of loose connective tissue around individual nerve fibres.

endoneurium

Each neuron consists of a body, axon and __________.

dendrites

Nerve impulses are transmitted in one direction: into the cell body through the dendrites and away through the __________.

axon

The myelin sheath in the peripheral nervous system is produced by __________ cells.

Schwann

The nodes of __________ increase the speed of electrical impulses through saltatory conduction.

Ranvier

According to the axon's length, nerve tissue can be classified into golgi type 1 and golgi type __________.

2

According to the number of processes, neurons can be __________, bipolar, or unipolar.

multipolar

There are three types of neurons based on function: sensory, relay, and __________ neurons.

motor

The central types of neuroglial cells include astrocytes, oligodendrocytes, __________, and microglia.

ependymal

Neurons and macroglia originate from __________.

ectoblast

Glial cells are non-conducting and act as __________ between the neurons.

insulators

Oligodendrocytes produce myelin sheath in the __________ nervous system.

central

Ependymal cells secrete __________ fluid (CSF).

cerebral spinal

nerve tissue description

• 2 types of cell neurons and glial cells

• ectoderm origin

• function to sense stimuli and transmit signal to different parts

• divided into CNS and PNS

CNS

• made of grey matter and white matter

• unmyelinated neurons and glial cells

• myelinated dominate the white whereas grey consist of neuron bodies

• rich vascular supply more abundant in grey matter

• myelin sheath is made of oligodendrocytes

epineurium

sheath of dense connective tissue surrounding each nerve

perineurium

epineurium penetrates the nerve to form the perineurium surrounding bundles of nerve fibres

endoneurium

consists of a thin layer of loose connective tissue, surrounds the individual fibres

difference between the epineurium, perineurium and endoneurium

The epineurium is the outermost layer providing protection to the entire nerve, the perineurium surrounds individual fascicles of nerve fibers, and the endoneurium encloses each nerve fiber, providing support and insulation.

neurons

main cell of nervous tissue and are derived from ectoblast, collect stimuli transforming them into a nerve impulse by synthesising and releasing neurotransmitters

consists of body, axon and dendrites

dendrites to the cell body and axon away from the cell body

nissl bodies are found in the cytoplasm of the cell body which is for synthesis of proteins

PNS

• myelin sheath is made of Schwann cells

• have nodes of Ranvier which allow the speed of electrical impulses to increase because they jump from node to node called saltatory conduction

variations of nerve tissue classes

axon length : golgi type 1 =long, golgi type 2 = short

axon shape : star, pyramid, pear, spindle

axon function : motor, sensory, relay

axon processes : bipolar, unipolar, multipolar

central types of neuroglial cells

• astrocytes - structural support, maintain blood-brain barrier

• oligodendrocytes - insulating cells of the spinal cord

• ependyma - production and secretion of cerebral spinal fluid, line the ventricles of the brain and the central canal of the spinal cord

• microglia - supporting cells for immune defence

macroglia

a type of neuroglial cell that includes astrocytes and oligodendrocytes, providing support, insulation, and maintaining homeostasis in the nervous system.

gliosis

A reactive process involving the proliferation of glial cells in response to injury or disease in the nervous system, often resulting in scar formation.