Question

Choose two different types of cell and explain how they are adapted for the job they do in your body

Answer 1

Answer: Neurons, which transmits information, have dendrites and axons to transmit the signals. Cardiomyocytes, capable of spontaneous contraction due to the ramifications and tight junctions between cells.

Explanation:

Neuron: Principal component cell of the nervous system, which receives, processes and transmits information through electrical and chemical signals thanks to the electrical excitability of its plasma membrane. So they are specialized cells in the reception of stimuli and conduction of the nerve impulse, in the form of an action potential, between them through connections called synapses, or with other cell types such as, for example, the muscle fibers of the motor plate. So neurons have the ability to communicate accurately, rapidly, and over long distances with other cells, whether nerve, muscle, or glandular.  Neurons have morphological characteristics that support their functions:

• Dendrites: Short extensions consisting of cytoplasmic projections enveloped by a plasma membrane without a myelin sheath, that transmit impulses to the cell soma. The nerve impulse travels through the neuron, and when it reaches the dendrites, it jumps to the next neuron through the synapse (connection between cells), which occurs through the exchange of chemical substances called neurotransmitters. It also has many microtubules and few neurofilaments, both arranged in parallel bundles, many mitochondria, Nissl clumps (composed of free ribosomes attached to the rough reticulum) and smooth endoplasmic reticulum.

• Axons: Long extension surrounded by a membrane called axolemma, which conducts impulses from the soma to another neuron or target organ. Many axons are covered with a special insulating substance called myelin, which helps them to transmit nerve impulses quickly. Near its end, the axon divides into many branches and develops bulbous structures known as axon terminals. These axon terminals form connections with target cells.

The cell bodies of some neurons from the Peripheral Nervous System (PNS), such as the motor neurons that control skeletal muscles, are located in the Central Nervous System (CNS). The axons from this motor neurons run from the CNS to the muscles they connect with. The cell bodies of other PNS neurons, such as sensory neurons that provide information, for example about touch or temperature, are located outside the CNS, where they are grouped in clusters known as ganglia.  Axons of peripheral neurons that travel a common pathway bundle together and form nerves.

Neurons also consists of a central nucleus and a perikaryon that contains the typical organelles of an eukaryotic cell.

• Cell nucleus: Contains one or two prominent nucleoli, and a dispersed chromatin, which indicates a high transcriptional activity.The nuclear envelope, with a multitude of nuclear pores, has a highly developed nuclear lamina.  
• Perikarion : The most notable organelle, is the Nissl substance and such abundance in protein synthesis is due to the high biosynthetic rate.  The Golgi apparatus is a highly developed system of flattened, small agranular vesicles and it is the region where the products of the Nissl substance enable further synthesis. There are also lysosomes and mitochondria , a cytoskeleton rich in microtubules and intermediate filaments.  

Cardiomyocytes: Cardiac muscle cells that represents the contractile unit of the myocardiom, capable of spontaneous contraction since they show specialization in excitation and conduction of action potentials. The characteristic ramifications and tight junctions between these cells form a solid network of myocardial fibers, which determines the cardiac pump function and the cellular electrical conduction system that allows this pump to function.  They are uninucleated cells with a large nucleus located in the center of the cell cytoplasm and they show transverse striations, with dark bands corresponding to the overlapping of actin and myosin filaments in their cytoskeleton, and with light bands corresponding only to actin filaments.  Cardiomyocytes have morphological characteristics that support their functions:

• Sarcoplasmic reticulum: Not well developed and distributed irregularly among the myofibrils, which appear distinctly separated.
• Mitochondria: Small and extremely numerous, packed and regularly distributed, dividing the cardiac cells into very obvious myofibrils. Cardiac muscle cells have very little glycogen and therefore cannot obtain much energy from glycolysis. This means that most of their energy comes from oxidative phosphorylation, with high oxygen consumption.
• Cytoplasm: Occupied by longitudinally arranged myofibrils with a striated pattern.
• Intercalary discs: Join cardiomyocytes, which appear as dark bands in histological preparations, and which are a set of junctional complexes where desmosomes and adherens junctions can be found. There are also cleavage junctions that allow contractile synchronization as they communicate cytoplasms of neighboring cells directly.