Week 2: Structure & Function of Cells Flashcards
cell
basic units of the structure and function of living things
*First coined by Robert Hooke in 1665
*Honeycomb appearance
Cell Theory
*All organisms are made of one or more cells
*All life functions occur within cells
*All cells come from already existing cells
Nerve cells (Neurons)
cells of the nervous system that generate electrical signals (action potentials) which allow them to communicate.
*They have a nucleus (vs. prokaryote cells)
*They do not renew themselves
Neurons based on function:
Sensory
Motor
Interneuron/Relay
Sensory Neuron
*Soma located in PNS
*Detects changes in the external and internal environment and sends info to CNS
Motor Neuron
Soma located within the CNS
*controls muscle contraction and secretion of glands
Relay/ Interneuron
*Located in CNS within neuronal structures
*Connect somatic and motor information 11
Neurons based on structure:
Unipolar/Pseudo-unipolar
Bipolar
Multipolar
Unipolar / Pseudo-unipolar
One process. Sensory neurons (spinal/cranial nerve ganglia)
Bipolar
Two processes. Usually sensory neurons (e.g.retinal cells), also interneurons
Multipolar
Multiple processes. Most common neuron in the CNS
Plasma/ Cell Membrane
Structure
*Pliable lipid bilayer
*Selectively permeable *Embedded proteins
Function
*Protects inner cellular environment
*Regulates molecules that enter and exit the cell
*Passive Transport vs. Active Transport
Cytoplasm
*Made up of cytosol and organelles
- Place of chemical reactions
*In motion, moving material from one part of cell to other
Cytosol
Thick, jelly-like substance ~ 80% water
Organelles
membrane-enclosed bodies within the cell
Nucleus
“Control center” of the cell
*Contains chromosomes/DNA/genes
*DNA contains genes that each cell uses to make thousand of proteins, enabling the cell to survive
*It directs many of the cell’s activities
Mitochondria
Powerhouse of cell –creates more than 90% of cellular activity
*Produces ATP
*DNA material present
*Necessary to sustain life and support growth
*Mitochondrial failure causes cell injury that leads to cell death.
Endomembrane System
Endoplasmic reticulum
Golgi Apparatus
Lysosomes
Endoplasmic reticulum
Location for synthesis of proteins (RER) and lipids i.e. Ribosomes
Ribosomes
organelles in the cytoplasm and within the RER which synthesizes proteins for the cell
Golgi Apparatus
organelle that packages the products synthesized by the ER (proteins, lipid molecules)
Lysosomes
organelle that breaks down damaged cellular components or foreign material. Also facilitates apoptosis
Cytoskeleton
Cytoskeleton is part of cytoplasm which is important for cell shape and movement
Microtubles
*A long strand of bundles of protein filaments (tubulin)
*Involved in transporting substances from place to place within the cell and along the axon.
Axoplasmic transport (aka axonal transport): Anterograde
soma -> periphery
Axoplasmic transport (aka axonal transport): Retrograde
periphery towards soma
Glia cell / Neuroglia
*The “glue” of the nervous system
*Smaller in size than neurons
*Various roles: support neurons, modulate neuron communication, and maintains homeostasis of the nervous system
Types of Glial cells
(S A M E O S)
CNS:
Ependymal
Astrocytes
Oligodendrocytes
Microglia
PNS:
Satellite
Schwann
Ependymal cells
Lines each of the 4 ventricles and spinal cord
*Filters blood to make CSF
Astrocytes
*Physical support to cell
*Repair damage to tissue
*Controls chemical environment *Fosters neural communication (tripartite synapse)
*Nourishes cells
Microglia
*Smallest of glia
*Macrophage of the CNS
*Immune defense
Oligodendrocytes
*Myelin sheath of the CNS
Satellite cells
*Surround sensory neurons, sympathetic and parasympathetic ganglia
*Regulate extracellular space
*Activated in response to tissue damage –aid in repair of damaged tissue and muscle repair
Schwann cells
*Provide myelin sheath to axons in the PNS
*Each myelin “segment” is made up of a single Schwann cell
Degradation of microglia
*Compromised immune function of the brain
*Neurological disorders
Degradation of oligodendrocytes
*ALS
*MS
*Dementia
*Schizophrenia
*Degradation of astroglia
*Synaptogenesis
*Neurodegeneration
*Seizure disorder
The Blood-Brain Barrier (BBB)
➢Discovered in 19th century: Ehrlich & Goldman injected colored dyes into blood stream versus CSF
➢Lina Stern coined BBB and described selective permeability
*A physical barrier between the brain and blood
*Made up of capillaries (endothelial cells) that form tight junctions
*Semi-permeable barrier
*Passive diffusion of oxygen, carbon dioxide, small uncharged molecules, lipid soluble molecules
*Active transport for glucose, amino acid, choline, iron, hormones
BBB Functions
*Protection: prevents easy access of pathogens, toxins and harmful metabolites
*Homeostasis: regulates movement of Na+ and K+
*Nutrition: allows transport of glucose
Circumventricular Organs: Allows the brain to monitor the physiological status of the body and regulation of endocrine function
BBB Compromised by:
*Radiation
*Hypertension
*Infection, trauma/inflammation
