Communication: Introduction to CNS Biology PDF

Communication: Introduction to CNS biology **MLO16.    **Explain the adaptations of different cell types and the processes that enable them to; \                             a)     provide immunity, and \ **                            b)    generate nerve impulses**\ **     MLO17.     **List the ke...

Communication: Introduction to CNS biology **MLO16.    **Explain the adaptations of different cell types and the processes that enable them to; \                             a)     provide immunity, and \ **                            b)    generate nerve impulses**\ **     MLO17.     **List the key features of the nervous system Membrane potential: the difference in potential/voltage across a membrane at one point in time. Membrane potential fluctuates all the time All cells have a membrane potential, at rest the average is -70mV The intracellular organelles also have membrane potentials which are set up by an imbalance of charged particles. Resting potential: the potential of the cell across its membrane Spike in graph is reversal of action potential/small dips at bottom are synaptic potentials which don't cause an action potential Sodium potassium pump - Form of active transport - Pumps sodium ions out of cell - Pumps potassium ions into cell - Causes imbalance of ions - 3 sodiums for two potassiums Membrane potential creation: - Membrane more impermeable to sodium - More permeable to potassium, causing leak outwards - Membrane is then more negative - Concentration gradient pushes potassium ions out of cell, building voltage gradient - Voltage gradient causes sodium ions to go in more, balancing out - Equilibrium potential reached Neurons: - Electrically excitable - Respond to inputs by sending electrical signal along axon - This is accompanied by the action potential in the form of a nerve impulse Action potential: - Momentary reversal of electrical potential - If the axon is depolarised above -50mV (threshold value), an action potential is generated - Depolarisation is the increase in the curve on a graph, and is caused by sodium channels opening and sodium flooding in - More depolarisation occurs - Repolarisation then occurs, as sodium channels close - Slight increase after is known as hyperpolarisation, where extra potassium channels are open so potential is more negative The brain is a development of the anterior spinal cord - It is protected by bones (skull) and vertebrae protect the spinal cord - Underneath the bones are three layers of membranes (Dura, arachnoid and matter) - Dura: hardest layer, underneath is filled with cerebrospinal fluid which flows through ventricles and down central canal of spinal cord - Arachnoid: looks like a spider as webbed - Matter: next to sensitive neuronal tissues Brain structure: - Two types of cells, neurons and glial - Neurons: dendrites, axons wrapped in myelin sheathe - Glial: make up 95% of the brain Glial cells: - Three types - Astrocytes: star shaped, feed neurons, manage intracellular/extracellular environment - Oligodendrocytes: wrap processes around neurons, insulate them with myelin sheath - Microglia: immune cells, detect bacterium etc and can engulf invading material  A diagram of the brain Description automatically generated A diagram of a brain Description automatically generated - Cortex controls memory, thinking etc - Hypothalamus regulates homeostasis in the body - Pituitary gland is the interface between the nervous system and endocrine system - Thalamus is a halfway point between cortex and the rest of the nervous system - Cerebellum controls simple motor movement - Pons and medulla oblongata control breathing, pH etc Outer view: - Grooves formed in brain known as sulky - Bits that stick out called gyory, gyrus singular - Four major lobes - Frontal lobe at front controls decision making and rational thinking - Parietal lobe near back - Temporal lobe along the side - Occipital lobe at back, controls vision The primary auditory cortex is located on the temporal cortex  Diagram of the neck and shoulder muscles Description automatically generated Spinal cord anatomy; - Segmental organisation - Each segment corresponds to area of body called dermatome - Each segment has two nerves, two roots coming out - Dorsal segment contains sensory neurons - Ventral segment contains motor neurons - Spinal chord also covered by dura, arachnoid and matter - White matter where axons are covered by myelin sheath - Grey matter is made of cell bodies and dendrites and synapses Grey matter can be divided in 2 ways: - Layers (called rexed layers) - Nuclei The dorsal and ventral horns are composed of grey matter Sensory input to the spinal cord is through the dorsal root The peripheral nervous system is what connects the brain and spinal cord to the rest of the body -- it is all the nervous system outside the spinal cord and brain - It is not protected by bones - Outside the blood brain barrier - Nerves are outside the plasma, therefore drugs can get to it - Susceptible to shock, mechanical or toxic - Divided into two halves, somatic and autonomic Somatic nervous system: - Sensory nerves provide input to CNS - Motor nerves connect CNS to muscles - Peripheral ganglia - Nerves coming into spinal cord will pass through dorsal (dorsal root ganglia) form a chain down the side of the spinal cord - Motor nerves divide into spinal and cranial nerves Ganglia: - Mini processors - Neuronal cell bodies connected by synapses Autonomic nervous system - Enteric nervous system: entirely autonomous, intestines - Sympathetic nervous system - Parasympathetic nervous system Sympathetic nervous system - Chain of ganglia next to spinal cord - Sympathetic neurons emerge through ventral root - Synapses in sympathetic ganglia - Preganglionic neurons from spinal cord to ganglia - Postganglionic neurons from ganglion to target - Stimulates adrenal medulla to retreat to release epinephrine and norepinephrine releasing energy from cells Parasympathetic nervous system - Neurons leave spinal chord - Preganglionic neurons - Postganglionic neurons - Synapse is taking place in target tissue instead of a visible ganglion near spinal cord - More visible peripheral ganglia Moodle recap quiz Q: Which one of the following is the best definition of active transport? A: A process that moves a material against its concentration gradient at the expense of energy Q: What is a common value for the resting membrane potential? A: -70mV Q: Ion channels can be divided into ?  -gated and ?  -gated ion channels (of which some neurotransmitter receptors are an example).  Voltage-gated ion channels open in response to a change in ?, which displaces a domain which has ?  , which in turn causes the ?  to open.  Voltage-gated ion channels typically consist of ?  subunits each with ?  domains, whereas ligand-gated ion channels have ?  subunits. A: voltage, ligand, potential, charge, gate, 4, 6, 5 Q: An action potential is triggered when the ? reaches the ?  potential.  At this point, ?  open, allowing the influx of positive charge .  After reaching its peak, the ?  starts to ? .  A brief ?  follows, after which the resting potential is resumed. A: membrane potential, threshold, voltage gated sodium channels, positive charge, membrane potential, repolarize, hyperpolarization Q: Which of the following is true of the resting membrane potential? A: It is the membrane potential when the membrane is at rest, It is caused by a selective permeability for potassium ions