[Biology Class Notes] on Nervous Tissue Pdf for Exam

Cells are regarded as the basic unit of structure and function in living organisms. They exercise our body’s basic functionalities. A cluster of these specialized cells together acts to shape a tissue. Plants and animals have tissues distinct from one another. There are four types of tissues in animals namely: 

• Connective Fabric 

• Tissue epithelial 

• Muscle tissues 

• Nerve Tissue

What is Nervous Tissue?

The primary tissue of our nervous system is the nervous or nerve tissue. It monitors and controls the body’s functions. Nervous tissue consists of two cells: neurons or nerve cells and glial cells, which help to transmit nerve impulses and also provide nutrients to neurons. 

Structure of Nervous Tissue

• It consists of nerve cells or neurons, all composed of an axon. Axons are long stem projections that arise from the cell and are responsible for interacting with other cells called the Target cells, thus passing on impulses.

• The main component is the cell body that contains the nucleus, cytoplasm, and organelles. Cell membrane extensions are termed processes. 

• Dendrite is a highly branched mechanism, responsible for receiving information from other neurons and synapses. Dendrites provide information on other neurons to connect with their cell body.

Information in the neuron is unidirectional as it passes from dendrites through the neurons, down the axon through the cell body.

Nervous Tissue Location

The nerve tissue or nervous tissue is the chief component of the two major parts of the nervous tissue – the central nervous system (CNS) formed by the spinal cord and the brain, and the peripheral branching nerves of the peripheral nervous system (PNS) that control and regulate the body’s functions and activities. 

The nervous tissue is located throughout the body in the peripheral nerves as well as in the central nervous system organs such as the spinal cord and brain. 

Characteristics of Nervous Tissue

• Nervous tissue compensates for nervous system CNS and PNS 

• Contains two different cells – neurons and glial cells 

• It consists of dendrites, ends of the cell body, axons, and nerves. 

• The neurons secrete chemical neurotransmitters that stimulate other neurons as a result of stimuli 

• Presence of axonal terminal specializations called synapsis 

• Nerve cells live long, can’t be broken and replaced (except memory cells)

Function of Nervous Tissue

• Neurons produce nerve impulses and execute certain impulses. They produce electrical signals that are transmitted over distances by secreting neurotransmitters of chemical substances 

• Reacts to stimuli 

• Carries out integration and communication 

• Provides electrical insulation and removes debris to nerve cells

• Carries messages from other neurons to the cell body

Types of Nerves

The signals generated and initiated in the CNS (central nervous system) typically from the brain and in some cases, the spinal cord, approach the outer edge of sites, such as the internal organs or limbs that are conducting the specified organ of interest in order to take appropriate action.

The functioning of the nerves is accomplished by channeling electrochemical signals or impulses from the other nerves or brain or tissues or organs at which the nerves end up. Nerves can be classified into the following, based on functionality:

Motor Nerves

Motor neurons or motor nerves are capable of transmitting signals or impulses to all the muscles of the body from the spinal cord to the brain. The impulse allows for basic activities such as speaking, walking, drinking water, blinking eyes, sitting, sleeping, etc. Motor neuron damage can cause muscle weakness or muscle shrinkage. The nerve that goes from the bottom up to the buttocks is known as the sciatic nerve. The sciatic nerve allows the whole leg which is a collection of different nerves. Some of those motor nerves work in the hamstrings, feet, thighs, and feet.

Sensory Nerves

The sensory nerves or sensory neurons are responsible, in contrasting directions, for generating impulses or signals from another type of nerves known as motor neurons. The neurons of the senses gather information from the sensors present in the muscles, skin, and other internal organs such as pressure, pain, temperature, etc. which in turn redirect it back to the brain and spinal cord. Such sensory nerves have the ability to transmit information relevant to the movement (except for the pupils, as they do so themselves). Damage to the sensory nerves may cause numbness, discomfort, tingling sensation, and hypersensitivity.

Autonomic Nerves

The network of autonomic nerves regulates the actions of the heart muscles, including smooth muscles that are found in the stomach and interlinking glands and other organs. The autonomic nerves regulate the non-controlled, i.e. unconscious functions. 

Cranial Nerves

On the lower side of the brain, there are 12 pairs of cranial nerves developing. The cranial nerves identified from forehead to back are listed below: 

Nerves with hypoglossal cranial nerves are crucial in smell, vision, movement of the face and eyes, movements of the tongue, and salivation.