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Week 6 (Scientist and Scholar Theme (Embryogenesis (After implantation has…

- - - - Primary
        
        Transport across a membrane when only the substance required to pass through is transported. Energy is gained through the direct hydrolysis of ATP
        
        Endocytosis
        
        Pinocytosis
        
        Process of transporting substances through a cell membrane in the form of a liquid. No receptors are required and the substance is transported in vesicles
        
        Phagocytosis
        
        The process of a cell ingesting an object and this allowing it to enter its cytoplasm. This is done by putting false feet around the object and consuming it within a sac
        
        Receptor-mediated endocytosis
        
        Process of particles entering he cell by binding to particular receptor proteins on the membrane and therefore being brought in with vesicles
        
        Exocytosis
        
        The only type of exocytosis is vesicular trafficking. In this process, the substance that is to be ejected is placed in a vesicle and then transported out of the cell. This vesicle is made of the same material as the plasma membrane and is thus able to fuse with it to expel substances
      - Secondary
        
        This method uses energy stored in ionic gradients to allow for substances to pass through can move substances in opposite directions (antiport system), or in the same direction (symport system)
    - - Facilitated diffusion
        
        Carrier-mediated
        
        This is shown by the flipping and flopping nature of proteins depending on what is bound to the channel. This flipping and flopping nature is what allows for the transfer. Furthermore, protein carries in the membrane are also able to ferry across substances
        
        Channel-mediated
        
        Involves channel proteins, and the ions that pass through are chosen depending on their size and charge. The ion is able to pass through water-filled protein channels
      - Osmosis
        
        The process of water moving with the concentration gradient to alter the tonicity of the cell.
        
        Isotonic
        
        Where there is no net movement of water as there is a balance in concentration of ions inside and outside of the cell
        
        Hypotonic
        
        This is when there is too much of a concentration of solutes within the cell. This means the cell attempts to let as much water in as possible and therefore expands. If too much water is ingested however, the cell can lyse
        
        Hypertonic
        
        If a cell is described as hypertonic, this means that there are not enough solutes present in the cellular environment and therefore the cell starts to shrivel up
      - Simple diffusion
        
        When a molecule or substance simply moves through the membrane of a cell. This process does not require any activity of the cell itself. An example is the ability of ethanol to move through the plasma membrane as it is able to interact with the polar heads of the phospholipid bilayer heads (polar alcohol group) and the nonpolar tails (carbon chain)
    - - There are villi formed in the lacunae of the embryo which are immersed in maternal blood. These villi allow for the passage of nutrients through the process of cellular membrane transport. The part of the endometrium that lies beneath the embryo becomes the decidua basalis and the part surrounding the uterine cavity is the decidua capsularis. Together, the chorionic villi and decidua basalis form the disc-shaped placenta
  - - - Desmosomes
        
        Cellular junctions that allow for internal plaques of cells to be joined together in order for cells to be bound and also have the ability to form sheets
      - Tight junctions
        
        The most apical form of a cellular junction. These junctions hold two cells together and do not allow for the passage of substances any deeper than in the lumen they are present in
      - Gap junctions
        
        Junctions that are present with protein channels that allow for communication and the transfer of substances between cells
      - Adherens junctions
        
        Junctions that are present more basally than tight junctions and are bound together using actin filaments formed between the cytoplasmic faces of cells next to one another
      - Hemidesmosomes
        
        Junctions present at the basal end of a cell. These cell junctions anchor cells to the basement membrane (hold them in place)
    - - Integral proteins
        
        Proteins that have the ability to stretch from one side of the cell to another. In this case, they are called transmembrane proteins. These proteins can allow for transport by grouping together to form channels and also can form carriers to pass a substance across the membrane
      - Peripheral proteins
        
        Proteins that can be easily removed and only pass through one face of the cytoplasm. These proteins can allow for the structure of a cell as well as its interaction with other cells. They can also act as enzymes
- - - - Cells
        
        Glial cells - Glial cells are those that support the neurons and the nervous system in its operation. The peripheral nervous system contains two glial cells, satellite cells and Schwann cells
        
        Satellite cells - These cells play a regenerative role in the peripheral nervous system. They also allow for nutrients to be provided to the neurons and cushion them in the sympathetic and parasympathetic divisions
        
        Schwann cells - Schwann cells are responsible for myelination in the central nervous system and do so by wrapping around the neuron repeatedly. Schwann cells can also wrap around many neurons at a time, however these axons are said to be 'unmyelinated'
        
        Neurons - The main functional unit of the peripheral nervous system. The main function of neurons is to relay either sensory information or motor information wither to or from the CNS respectively
        
        General structure
        
        Terminal bouton - Ends of the synapse (elongated buds) that are the points at which vesicles are able to release neurotransmitters into the synapse in order to be received by the synaptic neuron
        
        Cell body (soma) - The soma is the main control centre of the neuron and contains the nucleus. This is where all of the dendrites and therefore nerve impulses converge and therefore are transported to the axon
        
        Axon terminals - Axon terminals are the ends of the axon and are where the postsynaptic neurons are able to attach to the presynaptic neuron
        
        Dendrites - These are the 'listening arms' of the neuron and extend from the body to receive nerve impulses from other neurons
        
        Axon hillock - The point at which the cell body meets the axon. It is the point at which all of the nerve impulses gained by the dendrites are collected and sent forward through the axon
        
        Terminal branches - The end of the neuron where the presynaptic and postsynaptic neurons meet
        
        Nodes of Ranvier - The space where one Schwann cell ends and another begins on an axon is called a 'Node of Ranvier'. These nodes are helpful to the function of the axon as they allow for saltatory conduction. This is when the nerve impulse is able to 'jump over' the gaps created by the Schwann cells and therefore the passage of the impulse is faster
        
        Epineurium - The combination of many nerve fascicles in order to form a nerve. This nerve is covered in the epineurium which is a reticulin fibre connective tissue layer
        
        Perineurium - Many nerve fibres group together to form a nerve fascicle are covered in the perineurium. The perineurium also contains the blood-nerve barrier that is selectively permeable
        
        Endoneurium - The myelin sheath of the neuron (myelinated layer)
        
        Organelles
        
        Neurotransmitters - Chemical messengers that are sent from the synapse of the presynaptic to postsynaptic neuron. There can be thousands of neurotransmitters that can be released at a time to relay a message
        
        Nucleus - The control centre of the neuron. It contains the nucleolus which contains the genetic material important for the correct operation of the neuron. The nucleus is also the location of the synthesis of ribosomal units
        
        Nucleolus - The site that contains the genetic material of the neuron. It is also the site where ribosomal units are made
        
        Nissl body - A large granular body which is the rough endoplasmic reticulum of the neuron. There are many Nissl bodies present (granules) that contain ribosomes on them for the synthesis of proteins
        
        Ribosome - The organelle that is responsible for the formation of proteins for the operation of the neuron. This can include neurofilaments, which are crucial for the structure of the neuron
        
        Neurofilaments - Protein filaments which give structure and strength to the neuron
        
        Ganglia - A collection of nerve cell bodies outside of the CNS that have the role of relaying information from where the stimulus was sensed to the CNS.
        
        Psuedounipolar
        
        These neurons are found in the sensory division in the autonomic ganglia
        
        Multipolar
        
        These neurons are part of the spinal cord (CNS). They have the role of relaying information from the sensory pseudounipolar neurons to the brain and then sending a response back to the pseudounipolar neurons of the motor division to carry out a response
        
        Bipolar
        
        Bipolar neurons have a highly specialised sensory role as they are present in specific parts of the body such as the retina, olfactory epithelium, and ganglia of the inner ear
      - Motor (efferent) division
        
        The somatic motor division controls motor innervation of skeletal muscle (voluntary), and the visceral system controls processes such as peristalsis and constant heart rate
        
        Autonomic nervous system (ANS) - This system is a subcategory of the visceral motor division
        
        Parasympathetic division
        
        The rest and digest division that has the role of carrying out processes such as digestion or slowing heart rate
        
        Sympathetic division
        
        The sympathetic nervous system is associated with stress responses to situations and includes motor responses such as increased heart rate, blood pressure, and defines 'fight or flight' responses
      - Sensory (afferent) division
        
        Sensory messages (stimuli) travel from the peripheries of the body to the spinal cord. The somatic sensory division is responsible for monitoring touch, pain, vibration, and other special functions such as smell, hearing, and vision. The visceral division on the other hand senses internal bodily stimuli such as taste, hunger, and nausea
    - - Other cells
        
        Pyramidal cells
        
        Contain a dendrite on the apical end and a dendrite tree on the basal end and are primary excitation units
        
        Purkinje cells
        
        These cells are large neurons that have many branches and are found in the cortex of the brain and have a fundamental role in controlling motor movement
      - Glial cells
        
        Ependymal cells
        
        These cells are present in the ventricles of the brain and have the role of producing cerebrospinal fluid. This fluid is essential for the protection of the brain (acts as buffer) and also is able to allow for the transfer of nutrients and removal of wastes
        
        Microglia
        
        The function of these glial cells is analogous to macrophages in the rest of the body. They have the role phagocytosing waste products and overall serving a cleaning role in the brain as they are able to remove wastes and clean up the by-products of reactions as well
        
        Oligodendrocytes
        
        The function of these cells is analogous to that of Schwann cells in the PNS. Oligodendrocytes are however able to myelinate many (up to 60) axons at once and therefore allow for the protection of these axon bodies
        
        Astrocytes
        
        Astrocytes are analogous in their function to satellite cells in the PNS. These cells are responsible for the transfer of nutrients from the blood vessels that are present in the brain to the neurons so that they are able to function. The astrocytes are able to do this by allowing nutrients to diffuse through the false feet that these cells have that attach to the blood vessels to the neuron
    - - From the peripheral nervous system, the nerve impulse reaches the dorsal root ganglion where it is relayed to the spinal cord. In the spinal cord, the nerve impulse is transported to the brain. When a response is sent, the nerve impulse goes back into the spinal cord where a motor neuron cell body picks up the signal and transports it through the ventral root of the spinal nerve and to the effector