Red Blood Cells
Overview on how to examine and explore histology slides using a light microscope. General Systems Fetal Tissues Register now and grab your free ultimate anatomy study guide! Thus horizontal cells in the cerebral cortex are not the same as horizontal cells in the retina. Transmission of Autonomic Stimuli Neurons generate and propagate action potentials along their axons. These cells contain vesicles of hormones or enzymes ready to be released.
Eventually, efficient pathways of neural connections are carved out. During early childhood, which is known as a critical period of development, the nervous system must receive certain sensory inputs in order to develop properly. Once such a critical period ends, there is a precipitous drop in the number of connections that are maintained, and the ones that do remain are the ones that have been strengthened by the appropriate sensory experiences.
American neuroscientist Jordan Grafman has identified four other types of neuroplasticity, known as homologous area adaptation , compensatory masquerade, cross-modal reassignment, and map expansion. Homologous area adaptation occurs during the early critical period of development. If a particular brain module becomes damaged in early life, its normal operations have the ability to shift to brain areas that do not include the affected module.
The function is often shifted to a module in the matching, or homologous, area of the opposite brain hemisphere. The downside to this form of neuroplasticity is that it may come at costs to functions that are normally stored in the module but now have to make room for the new functions. An example of this is when the right parietal lobe the parietal lobe forms the middle region of the cerebral hemispheres becomes damaged early in life and the left parietal lobe takes over visuospatial functions at the cost of impaired arithmetical functions, which the left parietal lobe usually carries out exclusively.
Timing is also a factor in this process, since a child learns how to navigate physical space before he or she learns arithmetic. The second type of neuroplasticity, compensatory masquerade, can simply be described as the brain figuring out an alternative strategy for carrying out a task when the initial strategy cannot be followed due to impairment. One example is when a person attempts to navigate from one location to another.
Most people, to a greater or lesser extent, have an intuitive sense of direction and distance that they employ for navigation. However, a person who suffers some form of brain trauma and impaired spatial sense will resort to another strategy for spatial navigation, such as memorizing landmarks.
The only change that occurs in the brain is a reorganization of preexisting neuronal networks. The third form of neuroplasticity, cross-modal reassignment, entails the introduction of new inputs into a brain area deprived of its main inputs.
A classic example of this is the ability of an adult who has been blind since birth to have touch , or somatosensory, input redirected to the visual cortex in the occipital lobe region of the cerebrum located at the back of the head of the brain—specifically, in an area known as V1.
Sighted people, however, do not display any V1 activity when presented with similar touch-oriented experiments. Moreover, all the sensory cortices of the brain—visual, auditory, olfactory smell , gustatory taste , and somatosensory—have a similar six-layer processing structure. Because of this, the visual cortices of blind people can still carry out the cognitive functions of creating representations of the physical world but base these representations on input from another sense—namely, touch.
This is not, however, simply an instance of one area of the brain compensating for a lack of vision. It is a change in the actual functional assignment of a local brain region. Map expansion, the fourth type of neuroplasticity, entails the flexibility of local brain regions that are dedicated to performing one type of function or storing a particular form of information. This phenomenon usually takes place during the learning and practicing of a skill such as playing a musical instrument.
Specifically, the region grows as the individual gains implicit familiarity with the skill and then shrinks to baseline once the learning becomes explicit. Implicit learning is the passive acquisition of knowledge through exposure to information, whereas explicit learning is the active acquisition of knowledge gained by consciously seeking out information. But as one continues to develop the skill over repeated practice, the region retains the initial enlargement. Map expansion neuroplasticity has also been observed in association with pain in the phenomenon of phantom limb syndrome.
The relationship between cortical reorganization and phantom limb pain was discovered in the s in arm amputees. Later studies indicated that in amputees who experience phantom limb pain, the mouth brain map shifts to take over the adjacent area of the arm and hand brain maps.
In some patients, the cortical changes could be reversed with peripheral anesthesia. Some of the earliest applied research in neuroplasticity was carried out in the s, when scientists attempted to develop machines that interface with the brain in order to help blind people. The machine consisted of a metal plate with vibrating stimulators.
A camera was placed in front of the patient and connected to the vibrators. The camera acquired images of the room and translated them into patterns of vibration, which represented the physical space of the room and the objects within it.
After patients gained some familiarity with the device, their brains were able to construct mental representations of physical spaces and physical objects. Thus, instead of visible light stimulating their retinas and creating a mental representation of the world, vibrating stimulators triggered the skin of their backs to create a representation in their visual cortices.
A similar device exists today, only the camera fits inside a pair of glasses and the sensory surface fits on the tongue. Today neuroscientists are developing machines that bypass external sense organs and actually interface directly with the brain.
For example, researchers implanted a device that monitored neuronal activity in the brain of a female macaque monkey. Thus, the monkey became capable of moving a robot arm with its thoughts. This means that the motor cortex does not control the details of limb movement directly but instead controls the abstract parameters of movement, regardless of the connected apparatus that is actually moving. For humans, however, less-invasive forms of brain-computer interfaces are more conducive to clinical application.
For example, researchers have demonstrated that real-time visual feedback from functional magnetic resonance imaging fMRI can enable patients to retrain their brains and therefore improve brain functioning. Patients with emotional disorders have been trained to self-regulate a region of the brain known as the amygdala located deep within the cerebral hemispheres and believed to influence motivational behaviour by self-inducing sadness and monitoring the activity of the amygdala on a real-time fMRI readout.
Stroke victims have been able to reacquire lost functions through self-induced mental practice and mental imagery. This kind of therapy takes advantage of neuroplasticity in order to reactivate damaged areas of the brain or to deactivate overactive areas of the brain.
Today researchers are investigating the efficacy of these forms of therapy for individuals who suffer not only from stroke and emotional disorders but also from chronic pain, psychopathy, and social phobia. We welcome suggested improvements to any of our articles.
You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Your contribution may be further edited by our staff, and its publication is subject to our final approval. T-cells are involved in the destruction of bacteria, viruses and other damaging cells such as cancer cells.
They have a large kidney bean shaped nucleus. Monocytes circulate in the bloodstream between one and three days before entering the tissues of the body where they become macrophages. Macrophages are large phagocytic cells that engulf and kill dead cells and bacterial cells.
Just like the white and red blood cells, platelets also form an important component of the blood. Technically platelets are fragments of cells rather than true cells, but are vital in the control of bleeding. They are fragments of large cells called megakaryocytes which are produced in the bone marrow. They have surface proteins which allow them to bind to one another, and to bind to damaged blood vessel walls. They plug the source of the bleeding, coagulating and sticking together to form a blood clot, together with a fibrous protein known as fibrin.
Multipolar neuron - histological slide. Neurons can have multiple, two or one dendrite s which makes them multipolar , bipolar or unipolar respectively. They convert chemical signals from the synapse into small electrical impulses, and transmit them towards the cell body.
Electrical disturbance in the dendrites is transmitted to a structure called the axon hillock at the base of the axon, and with enough voltage, generates an action potential which moves down the axon and continues its course. Glia are very common in the brain , outnumbering neurons at a ratio of 3 to 1. Glia are smaller than neurons, and do not have axons or dendrites.
They have a variety of roles in the nervous system, they modulate synaptic action and rate of impulse propagation, they provide a scaffold for neural development, and aid recovery from neural injuries. Microglial cells - histological slide. There are 3 types of muscle cells, known as myocytes , in the human body. These types are skeletal, cardiac and smooth muscle. Skeletal and cardiac muscle cells are known as striated , due to the aligned arrangement of myosin and actin proteins within them.
Actin and myosin allow muscle contraction by sliding past one another, as described by sliding filament theory. Actin and myosin are arranged more randomly in smooth muscle cells, creating a smooth rather than striated appearance.
Skeletal muscle cells are responsible for voluntary movements. They are multinucleated and comprise a sarcolemma cell membrane , sarcoplasm cytoplasm , myofibrils actin and myosin , sarcosomes mitochondria and a sarcoplasmic reticulum , which is like the smooth endoplasmic reticulum of other cells.
They also contain two proteins called troponin and tropomyosin which regulate the interaction between actin and myosin during contraction. The basic units of striated muscle cells comprising actin and myosin are known as sarcomeres.
Smooth muscle cells are arranged in sheets allowing them to contract simultaneously. As they are smaller than cardiomyocytes and skeletal myocytes, they contain fewer cell organelles, and do not contain sarcomeres.
Chondrocytes produce and maintain the extracellular matrix of cartilage, comprising collagen, proteoglycan and elastin fibers. They lack blood vessels meaning that cartilage is repaired slower than other tissues, and nutrients have to be absorbed by diffusion from the tissue surrounding the cartilage, known as the perichondrium.
Articular cartilage cartilage found in synovial joints differs from other cartilages since it does not contain perichondrium. Osteoclasts are large multinucleated cells that are involved in bone resorption. This is where the bone is broken down during the process of renewal. Osteoclasts break down bone by forming sealed compartments on its surface, and releasing enzymes and acids.
After they complete the process, they die by apoptosis programmed cell death. They are cuboidal in shape and have one central nucleus. They work by synthesising protein which forms the organic matrix of the bone. Osteocytes are cells that are found inside the bone. Osteocytes can sense mechanical strain being placed on the bone, and secrete growth factors which activate bone growth in response. These originate as osteoblasts before becoming flat in structure.
Lining cells have receptors on their surfaces which are receptive to hormones and other chemicals that signify a need for bone growth and remodeling. There are many different types of cells in the epidermis top layer of the skin. The epidermis contains the following cell types:.
Keratinocytes generate the protein keratin , but are also important in protecting the body by blocking toxins and pathogens, and preventing loss of heat and moisture. They also stimulate inflammation and secrete inhibitory cytokines. The outermost layer of epidermis is formed by keratinized epithelial cells which are responsible for forming the protective barrier.
Hair and nails are examples of fully keratinized epithelial cells. These are dendritic cells involved in antigen processing when the skin becomes infected, they act as antigen-processing cells.
They contain large organelles known as Birbeck granules, but the exact function of these is still unknown. Endothelial cells are the cells that form the lining of blood vessels. They have a central nucleus, and are connected to one another via intercellular junctions. This allows growth and repair of body tissues, as new blood vessel networks can easily form.
As well as healthy body tissues, cancer cells also rely on endothelial cells and blood vessels to survive As a result, a lot of research is focused on preventing the formation of blood vessels in cancerous tissues.
Endothelial cells express different surface proteins, depending on whether they are forming veins or arteries. They are joined to one another forming sheets called epithelia , and are connected by tight junctions, adherens, desmosomes and gap junctions.
Tight junctions are unique to epithelial cells and form the closest type of junction between any cell type in the body. They are supported by a basement membrane known as a basal lamina , which covers a capillary bed. The nucleus of an epithelial cell is found close to the basal lamina, towards the bottom of the cell.
Epithelial cells are innervated with nerve endings, and can become sensory cells , detecting stimuli such as scent. Epithelial cells can also specialise to become secretory cells , that release mucous, hormones and enzymes into the body. These cells contain vesicles of hormones or enzymes ready to be released.
Specialised secretory epithelial cells include goblet cells and paneth cells in the intestines, which secrete mucous and antibacterial proteins respectively. Brown adipose tissue - histological slide. Sexual reproduction is the result of the fusion of two different types of sex cells called gametes.
Male sex cells are commonly known as sperm cells, or spermatozoa , and female gametes are known as eggs or ova. When they fuse together, fertilization occurs and a zygote is formed. The head contains an acrosome , which is a type of covering filled with enzymes that enable penetration of the female ovum during fertilisation. The head of the cell contains a nucleus that is densely packed with DNA, with little cytoplasm present. The midpiece region of the cell contains mitochondria which provide the energy required for locomotion.
Ova are very large compared to other cell bodies, being as large as 0. They are round in shape and are produced in the ovaries during embryological development. The cell itself comprises a nucleus, cytoplasm, the zona pellucida and the corona radiata.
The zona pellucida is a membrane that surrounds the cell membrane of the cell, and the corona radiata forms protective layers which surround the zona pellucida. During the process of fertilization, the spermatozoa binds with the ovum at the zona pellucida. After, the penetration of the spermatozoa and the release of its contents into the ovum can then occur acrosome reaction.
Lewis , et al. Neuroscience, 2nd Edition, Sinauer Associates Excitable Tissues Smooth Muscle. Molecular Cell Biology, 4th Edition, W. What is the Structure of Stem Cells? Advances in Dermatology and Allergology , volume 30, issue 1, p. Brown and beige fat: Nature Medicine , volume 19, p. Exercise and Sports Science Reviews , volume 39, issue 2, p.
Overview of Epithelial Cells. Epidermal Merkel cells are mechanosensory cells that tune mammalian touch receptors. What are Adult Stem Cells? Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours.
General Systems Fetal Tissues Register now and grab your free ultimate anatomy study guide! Types of cells in the human body - want to learn more about it? Sign up for your free Kenhub account today and join over , successful anatomy students. Create your free account. Highlights Stem cells are pluripotent cells that have the potential to become any type of cell in the body through a process called differentiation.
They are shaped like a biconcave disc. Platelets are fragments of cells rather than true cells, but are vital in the control of bleeding. They are fragments of large cells called megakaryocytes. Structurally, they have four specific regions; the cell body , dendrites , the axon and axon terminals. Neurons can have multiple, two or one dendrite s which makes them multipolar, bipolar or unipolar respectively.
There are four types of glial cells in the central nervous system; astrocytes, oligodendrocytes,microglial cells, and ependymal cells. Skeletal and cardiac muscle cells are known as striated, due to the aligned arrangement of myosin and actin proteins within them. The epidermis contains many types of cells, including keratinocytes, melanocytes, Langerhans cells and Merkel cells.
Endothelial cells are the cells that form the lining of blood vessels and are connected to one another via intercellular junctions. Fat cells, also referred to as adipocytes and lipocytes are the cells of the body that are specialised to store energy in the form of adipose tissue , or fat.